1 # SPDX-License-Identifier: GPL-2.0+
3 # (C) Copyright 2000 - 2013
4 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
9 This directory contains the source code for U-Boot, a boot loader for
10 Embedded boards based on PowerPC, ARM, MIPS and several other
11 processors, which can be installed in a boot ROM and used to
12 initialize and test the hardware or to download and run application
15 The development of U-Boot is closely related to Linux: some parts of
16 the source code originate in the Linux source tree, we have some
17 header files in common, and special provision has been made to
18 support booting of Linux images.
20 Some attention has been paid to make this software easily
21 configurable and extendable. For instance, all monitor commands are
22 implemented with the same call interface, so that it's very easy to
23 add new commands. Also, instead of permanently adding rarely used
24 code (for instance hardware test utilities) to the monitor, you can
25 load and run it dynamically.
31 In general, all boards for which a configuration option exists in the
32 Makefile have been tested to some extent and can be considered
33 "working". In fact, many of them are used in production systems.
35 In case of problems see the CHANGELOG file to find out who contributed
36 the specific port. In addition, there are various MAINTAINERS files
37 scattered throughout the U-Boot source identifying the people or
38 companies responsible for various boards and subsystems.
40 Note: As of August, 2010, there is no longer a CHANGELOG file in the
41 actual U-Boot source tree; however, it can be created dynamically
42 from the Git log using:
50 In case you have questions about, problems with or contributions for
51 U-Boot, you should send a message to the U-Boot mailing list at
52 <u-boot@lists.denx.de>. There is also an archive of previous traffic
53 on the mailing list - please search the archive before asking FAQ's.
54 Please see http://lists.denx.de/pipermail/u-boot and
55 http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58 Where to get source code:
59 =========================
61 The U-Boot source code is maintained in the Git repository at
62 git://www.denx.de/git/u-boot.git ; you can browse it online at
63 http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
65 The "snapshot" links on this page allow you to download tarballs of
66 any version you might be interested in. Official releases are also
67 available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70 Pre-built (and tested) images are available from
71 ftp://ftp.denx.de/pub/u-boot/images/
77 - start from 8xxrom sources
78 - create PPCBoot project (http://sourceforge.net/projects/ppcboot)
80 - make it easier to add custom boards
81 - make it possible to add other [PowerPC] CPUs
82 - extend functions, especially:
83 * Provide extended interface to Linux boot loader
86 * ATA disk / SCSI ... boot
87 - create ARMBoot project (http://sourceforge.net/projects/armboot)
88 - add other CPU families (starting with ARM)
89 - create U-Boot project (http://sourceforge.net/projects/u-boot)
90 - current project page: see http://www.denx.de/wiki/U-Boot
96 The "official" name of this project is "Das U-Boot". The spelling
97 "U-Boot" shall be used in all written text (documentation, comments
98 in source files etc.). Example:
100 This is the README file for the U-Boot project.
102 File names etc. shall be based on the string "u-boot". Examples:
104 include/asm-ppc/u-boot.h
106 #include <asm/u-boot.h>
108 Variable names, preprocessor constants etc. shall be either based on
109 the string "u_boot" or on "U_BOOT". Example:
111 U_BOOT_VERSION u_boot_logo
112 IH_OS_U_BOOT u_boot_hush_start
118 Starting with the release in October 2008, the names of the releases
119 were changed from numerical release numbers without deeper meaning
120 into a time stamp based numbering. Regular releases are identified by
121 names consisting of the calendar year and month of the release date.
122 Additional fields (if present) indicate release candidates or bug fix
123 releases in "stable" maintenance trees.
126 U-Boot v2009.11 - Release November 2009
127 U-Boot v2009.11.1 - Release 1 in version November 2009 stable tree
128 U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
134 /arch Architecture specific files
135 /arc Files generic to ARC architecture
136 /arm Files generic to ARM architecture
137 /m68k Files generic to m68k architecture
138 /microblaze Files generic to microblaze architecture
139 /mips Files generic to MIPS architecture
140 /nds32 Files generic to NDS32 architecture
141 /nios2 Files generic to Altera NIOS2 architecture
142 /openrisc Files generic to OpenRISC architecture
143 /powerpc Files generic to PowerPC architecture
144 /riscv Files generic to RISC-V architecture
145 /sandbox Files generic to HW-independent "sandbox"
146 /sh Files generic to SH architecture
147 /x86 Files generic to x86 architecture
148 /api Machine/arch independent API for external apps
149 /board Board dependent files
150 /cmd U-Boot commands functions
151 /common Misc architecture independent functions
152 /configs Board default configuration files
153 /disk Code for disk drive partition handling
154 /doc Documentation (don't expect too much)
155 /drivers Commonly used device drivers
156 /dts Contains Makefile for building internal U-Boot fdt.
157 /examples Example code for standalone applications, etc.
158 /fs Filesystem code (cramfs, ext2, jffs2, etc.)
159 /include Header Files
160 /lib Library routines generic to all architectures
161 /Licenses Various license files
163 /post Power On Self Test
164 /scripts Various build scripts and Makefiles
165 /test Various unit test files
166 /tools Tools to build S-Record or U-Boot images, etc.
168 Software Configuration:
169 =======================
171 Configuration is usually done using C preprocessor defines; the
172 rationale behind that is to avoid dead code whenever possible.
174 There are two classes of configuration variables:
176 * Configuration _OPTIONS_:
177 These are selectable by the user and have names beginning with
180 * Configuration _SETTINGS_:
181 These depend on the hardware etc. and should not be meddled with if
182 you don't know what you're doing; they have names beginning with
185 Previously, all configuration was done by hand, which involved creating
186 symbolic links and editing configuration files manually. More recently,
187 U-Boot has added the Kbuild infrastructure used by the Linux kernel,
188 allowing you to use the "make menuconfig" command to configure your
192 Selection of Processor Architecture and Board Type:
193 ---------------------------------------------------
195 For all supported boards there are ready-to-use default
196 configurations available; just type "make <board_name>_defconfig".
198 Example: For a TQM823L module type:
201 make TQM823L_defconfig
203 Note: If you're looking for the default configuration file for a board
204 you're sure used to be there but is now missing, check the file
205 doc/README.scrapyard for a list of no longer supported boards.
210 U-Boot can be built natively to run on a Linux host using the 'sandbox'
211 board. This allows feature development which is not board- or architecture-
212 specific to be undertaken on a native platform. The sandbox is also used to
213 run some of U-Boot's tests.
215 See doc/arch/index.rst for more details.
218 Board Initialisation Flow:
219 --------------------------
221 This is the intended start-up flow for boards. This should apply for both
222 SPL and U-Boot proper (i.e. they both follow the same rules).
224 Note: "SPL" stands for "Secondary Program Loader," which is explained in
225 more detail later in this file.
227 At present, SPL mostly uses a separate code path, but the function names
228 and roles of each function are the same. Some boards or architectures
229 may not conform to this. At least most ARM boards which use
230 CONFIG_SPL_FRAMEWORK conform to this.
232 Execution typically starts with an architecture-specific (and possibly
233 CPU-specific) start.S file, such as:
235 - arch/arm/cpu/armv7/start.S
236 - arch/powerpc/cpu/mpc83xx/start.S
237 - arch/mips/cpu/start.S
239 and so on. From there, three functions are called; the purpose and
240 limitations of each of these functions are described below.
243 - purpose: essential init to permit execution to reach board_init_f()
244 - no global_data or BSS
245 - there is no stack (ARMv7 may have one but it will soon be removed)
246 - must not set up SDRAM or use console
247 - must only do the bare minimum to allow execution to continue to
249 - this is almost never needed
250 - return normally from this function
253 - purpose: set up the machine ready for running board_init_r():
254 i.e. SDRAM and serial UART
255 - global_data is available
257 - BSS is not available, so you cannot use global/static variables,
258 only stack variables and global_data
260 Non-SPL-specific notes:
261 - dram_init() is called to set up DRAM. If already done in SPL this
265 - you can override the entire board_init_f() function with your own
267 - preloader_console_init() can be called here in extremis
268 - should set up SDRAM, and anything needed to make the UART work
269 - these is no need to clear BSS, it will be done by crt0.S
270 - for specific scenarios on certain architectures an early BSS *can*
271 be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
272 of BSS prior to entering board_init_f()) but doing so is discouraged.
273 Instead it is strongly recommended to architect any code changes
274 or additions such to not depend on the availability of BSS during
275 board_init_f() as indicated in other sections of this README to
276 maintain compatibility and consistency across the entire code base.
277 - must return normally from this function (don't call board_init_r()
280 Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
281 this point the stack and global_data are relocated to below
282 CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
286 - purpose: main execution, common code
287 - global_data is available
289 - BSS is available, all static/global variables can be used
290 - execution eventually continues to main_loop()
292 Non-SPL-specific notes:
293 - U-Boot is relocated to the top of memory and is now running from
297 - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
298 CONFIG_SPL_STACK_R_ADDR points into SDRAM
299 - preloader_console_init() can be called here - typically this is
300 done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
301 spl_board_init() function containing this call
302 - loads U-Boot or (in falcon mode) Linux
306 Configuration Options:
307 ----------------------
309 Configuration depends on the combination of board and CPU type; all
310 such information is kept in a configuration file
311 "include/configs/<board_name>.h".
313 Example: For a TQM823L module, all configuration settings are in
314 "include/configs/TQM823L.h".
317 Many of the options are named exactly as the corresponding Linux
318 kernel configuration options. The intention is to make it easier to
319 build a config tool - later.
321 - ARM Platform Bus Type(CCI):
322 CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
323 provides full cache coherency between two clusters of multi-core
324 CPUs and I/O coherency for devices and I/O masters
326 CONFIG_SYS_FSL_HAS_CCI400
328 Defined For SoC that has cache coherent interconnect
331 CONFIG_SYS_FSL_HAS_CCN504
333 Defined for SoC that has cache coherent interconnect CCN-504
335 The following options need to be configured:
337 - CPU Type: Define exactly one, e.g. CONFIG_MPC85XX.
339 - Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS.
344 Specifies that the core is a 64-bit PowerPC implementation (implements
345 the "64" category of the Power ISA). This is necessary for ePAPR
346 compliance, among other possible reasons.
348 CONFIG_SYS_FSL_TBCLK_DIV
350 Defines the core time base clock divider ratio compared to the
351 system clock. On most PQ3 devices this is 8, on newer QorIQ
352 devices it can be 16 or 32. The ratio varies from SoC to Soc.
354 CONFIG_SYS_FSL_PCIE_COMPAT
356 Defines the string to utilize when trying to match PCIe device
357 tree nodes for the given platform.
359 CONFIG_SYS_FSL_ERRATUM_A004510
361 Enables a workaround for erratum A004510. If set,
362 then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
363 CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
365 CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
366 CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
368 Defines one or two SoC revisions (low 8 bits of SVR)
369 for which the A004510 workaround should be applied.
371 The rest of SVR is either not relevant to the decision
372 of whether the erratum is present (e.g. p2040 versus
373 p2041) or is implied by the build target, which controls
374 whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
376 See Freescale App Note 4493 for more information about
379 CONFIG_A003399_NOR_WORKAROUND
380 Enables a workaround for IFC erratum A003399. It is only
381 required during NOR boot.
383 CONFIG_A008044_WORKAROUND
384 Enables a workaround for T1040/T1042 erratum A008044. It is only
385 required during NAND boot and valid for Rev 1.0 SoC revision
387 CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
389 This is the value to write into CCSR offset 0x18600
390 according to the A004510 workaround.
392 CONFIG_SYS_FSL_DSP_DDR_ADDR
393 This value denotes start offset of DDR memory which is
394 connected exclusively to the DSP cores.
396 CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
397 This value denotes start offset of M2 memory
398 which is directly connected to the DSP core.
400 CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
401 This value denotes start offset of M3 memory which is directly
402 connected to the DSP core.
404 CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
405 This value denotes start offset of DSP CCSR space.
407 CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
408 Single Source Clock is clocking mode present in some of FSL SoC's.
409 In this mode, a single differential clock is used to supply
410 clocks to the sysclock, ddrclock and usbclock.
412 CONFIG_SYS_CPC_REINIT_F
413 This CONFIG is defined when the CPC is configured as SRAM at the
414 time of U-Boot entry and is required to be re-initialized.
417 Indicates this SoC supports deep sleep feature. If deep sleep is
418 supported, core will start to execute uboot when wakes up.
420 - Generic CPU options:
421 CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
423 Defines the endianess of the CPU. Implementation of those
424 values is arch specific.
427 Freescale DDR driver in use. This type of DDR controller is
428 found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
431 CONFIG_SYS_FSL_DDR_ADDR
432 Freescale DDR memory-mapped register base.
434 CONFIG_SYS_FSL_DDR_EMU
435 Specify emulator support for DDR. Some DDR features such as
436 deskew training are not available.
438 CONFIG_SYS_FSL_DDRC_GEN1
439 Freescale DDR1 controller.
441 CONFIG_SYS_FSL_DDRC_GEN2
442 Freescale DDR2 controller.
444 CONFIG_SYS_FSL_DDRC_GEN3
445 Freescale DDR3 controller.
447 CONFIG_SYS_FSL_DDRC_GEN4
448 Freescale DDR4 controller.
450 CONFIG_SYS_FSL_DDRC_ARM_GEN3
451 Freescale DDR3 controller for ARM-based SoCs.
454 Board config to use DDR1. It can be enabled for SoCs with
455 Freescale DDR1 or DDR2 controllers, depending on the board
459 Board config to use DDR2. It can be enabled for SoCs with
460 Freescale DDR2 or DDR3 controllers, depending on the board
464 Board config to use DDR3. It can be enabled for SoCs with
465 Freescale DDR3 or DDR3L controllers.
468 Board config to use DDR3L. It can be enabled for SoCs with
472 Board config to use DDR4. It can be enabled for SoCs with
475 CONFIG_SYS_FSL_IFC_BE
476 Defines the IFC controller register space as Big Endian
478 CONFIG_SYS_FSL_IFC_LE
479 Defines the IFC controller register space as Little Endian
481 CONFIG_SYS_FSL_IFC_CLK_DIV
482 Defines divider of platform clock(clock input to IFC controller).
484 CONFIG_SYS_FSL_LBC_CLK_DIV
485 Defines divider of platform clock(clock input to eLBC controller).
487 CONFIG_SYS_FSL_PBL_PBI
488 It enables addition of RCW (Power on reset configuration) in built image.
489 Please refer doc/README.pblimage for more details
491 CONFIG_SYS_FSL_PBL_RCW
492 It adds PBI(pre-boot instructions) commands in u-boot build image.
493 PBI commands can be used to configure SoC before it starts the execution.
494 Please refer doc/README.pblimage for more details
496 CONFIG_SYS_FSL_DDR_BE
497 Defines the DDR controller register space as Big Endian
499 CONFIG_SYS_FSL_DDR_LE
500 Defines the DDR controller register space as Little Endian
502 CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
503 Physical address from the view of DDR controllers. It is the
504 same as CONFIG_SYS_DDR_SDRAM_BASE for all Power SoCs. But
505 it could be different for ARM SoCs.
507 CONFIG_SYS_FSL_DDR_INTLV_256B
508 DDR controller interleaving on 256-byte. This is a special
509 interleaving mode, handled by Dickens for Freescale layerscape
512 CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
513 Number of controllers used as main memory.
515 CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
516 Number of controllers used for other than main memory.
518 CONFIG_SYS_FSL_HAS_DP_DDR
519 Defines the SoC has DP-DDR used for DPAA.
521 CONFIG_SYS_FSL_SEC_BE
522 Defines the SEC controller register space as Big Endian
524 CONFIG_SYS_FSL_SEC_LE
525 Defines the SEC controller register space as Little Endian
528 CONFIG_SYS_INIT_SP_OFFSET
530 Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
531 pointer. This is needed for the temporary stack before
534 CONFIG_XWAY_SWAP_BYTES
536 Enable compilation of tools/xway-swap-bytes needed for Lantiq
537 XWAY SoCs for booting from NOR flash. The U-Boot image needs to
538 be swapped if a flash programmer is used.
541 CONFIG_SYS_EXCEPTION_VECTORS_HIGH
543 Select high exception vectors of the ARM core, e.g., do not
544 clear the V bit of the c1 register of CP15.
547 Generic timer clock source frequency.
549 COUNTER_FREQUENCY_REAL
550 Generic timer clock source frequency if the real clock is
551 different from COUNTER_FREQUENCY, and can only be determined
555 CONFIG_TEGRA_SUPPORT_NON_SECURE
557 Support executing U-Boot in non-secure (NS) mode. Certain
558 impossible actions will be skipped if the CPU is in NS mode,
559 such as ARM architectural timer initialization.
561 - Linux Kernel Interface:
564 U-Boot stores all clock information in Hz
565 internally. For binary compatibility with older Linux
566 kernels (which expect the clocks passed in the
567 bd_info data to be in MHz) the environment variable
568 "clocks_in_mhz" can be defined so that U-Boot
569 converts clock data to MHZ before passing it to the
571 When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
572 "clocks_in_mhz=1" is automatically included in the
575 CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]
577 When transferring memsize parameter to Linux, some versions
578 expect it to be in bytes, others in MB.
579 Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
583 New kernel versions are expecting firmware settings to be
584 passed using flattened device trees (based on open firmware
588 * New libfdt-based support
589 * Adds the "fdt" command
590 * The bootm command automatically updates the fdt
592 OF_TBCLK - The timebase frequency.
593 OF_STDOUT_PATH - The path to the console device
595 boards with QUICC Engines require OF_QE to set UCC MAC
598 CONFIG_OF_BOARD_SETUP
600 Board code has addition modification that it wants to make
601 to the flat device tree before handing it off to the kernel
603 CONFIG_OF_SYSTEM_SETUP
605 Other code has addition modification that it wants to make
606 to the flat device tree before handing it off to the kernel.
607 This causes ft_system_setup() to be called before booting
612 U-Boot can detect if an IDE device is present or not.
613 If not, and this new config option is activated, U-Boot
614 removes the ATA node from the DTS before booting Linux,
615 so the Linux IDE driver does not probe the device and
616 crash. This is needed for buggy hardware (uc101) where
617 no pull down resistor is connected to the signal IDE5V_DD7.
619 CONFIG_MACH_TYPE [relevant for ARM only][mandatory]
621 This setting is mandatory for all boards that have only one
622 machine type and must be used to specify the machine type
623 number as it appears in the ARM machine registry
624 (see http://www.arm.linux.org.uk/developer/machines/).
625 Only boards that have multiple machine types supported
626 in a single configuration file and the machine type is
627 runtime discoverable, do not have to use this setting.
629 - vxWorks boot parameters:
631 bootvx constructs a valid bootline using the following
632 environments variables: bootdev, bootfile, ipaddr, netmask,
633 serverip, gatewayip, hostname, othbootargs.
634 It loads the vxWorks image pointed bootfile.
636 Note: If a "bootargs" environment is defined, it will overwride
637 the defaults discussed just above.
639 - Cache Configuration:
640 CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
642 - Cache Configuration for ARM:
643 CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
645 CONFIG_SYS_PL310_BASE - Physical base address of PL310
646 controller register space
651 Define this if you want support for Amba PrimeCell PL010 UARTs.
655 Define this if you want support for Amba PrimeCell PL011 UARTs.
659 If you have Amba PrimeCell PL011 UARTs, set this variable to
660 the clock speed of the UARTs.
664 If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
665 define this to a list of base addresses for each (supported)
666 port. See e.g. include/configs/versatile.h
668 CONFIG_SERIAL_HW_FLOW_CONTROL
670 Define this variable to enable hw flow control in serial driver.
671 Current user of this option is drivers/serial/nsl16550.c driver
674 CONFIG_BAUDRATE - in bps
675 Select one of the baudrates listed in
676 CONFIG_SYS_BAUDRATE_TABLE, see below.
680 Only needed when CONFIG_BOOTDELAY is enabled;
681 define a command string that is automatically executed
682 when no character is read on the console interface
683 within "Boot Delay" after reset.
685 CONFIG_RAMBOOT and CONFIG_NFSBOOT
686 The value of these goes into the environment as
687 "ramboot" and "nfsboot" respectively, and can be used
688 as a convenience, when switching between booting from
691 - Serial Download Echo Mode:
693 If defined to 1, all characters received during a
694 serial download (using the "loads" command) are
695 echoed back. This might be needed by some terminal
696 emulations (like "cu"), but may as well just take
697 time on others. This setting #define's the initial
698 value of the "loads_echo" environment variable.
700 - Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
702 Select one of the baudrates listed in
703 CONFIG_SYS_BAUDRATE_TABLE, see below.
705 - Removal of commands
706 If no commands are needed to boot, you can disable
707 CONFIG_CMDLINE to remove them. In this case, the command line
708 will not be available, and when U-Boot wants to execute the
709 boot command (on start-up) it will call board_run_command()
710 instead. This can reduce image size significantly for very
711 simple boot procedures.
713 - Regular expression support:
715 If this variable is defined, U-Boot is linked against
716 the SLRE (Super Light Regular Expression) library,
717 which adds regex support to some commands, as for
718 example "env grep" and "setexpr".
722 If this variable is defined, U-Boot will use a device tree
723 to configure its devices, instead of relying on statically
724 compiled #defines in the board file. This option is
725 experimental and only available on a few boards. The device
726 tree is available in the global data as gd->fdt_blob.
728 U-Boot needs to get its device tree from somewhere. This can
729 be done using one of the three options below:
732 If this variable is defined, U-Boot will embed a device tree
733 binary in its image. This device tree file should be in the
734 board directory and called <soc>-<board>.dts. The binary file
735 is then picked up in board_init_f() and made available through
736 the global data structure as gd->fdt_blob.
739 If this variable is defined, U-Boot will build a device tree
740 binary. It will be called u-boot.dtb. Architecture-specific
741 code will locate it at run-time. Generally this works by:
743 cat u-boot.bin u-boot.dtb >image.bin
745 and in fact, U-Boot does this for you, creating a file called
746 u-boot-dtb.bin which is useful in the common case. You can
747 still use the individual files if you need something more
751 If this variable is defined, U-Boot will use the device tree
752 provided by the board at runtime instead of embedding one with
753 the image. Only boards defining board_fdt_blob_setup() support
754 this option (see include/fdtdec.h file).
758 If this variable is defined, it enables watchdog
759 support for the SoC. There must be support in the SoC
760 specific code for a watchdog. For the 8xx
761 CPUs, the SIU Watchdog feature is enabled in the SYPCR
762 register. When supported for a specific SoC is
763 available, then no further board specific code should
767 When using a watchdog circuitry external to the used
768 SoC, then define this variable and provide board
769 specific code for the "hw_watchdog_reset" function.
773 When CONFIG_CMD_DATE is selected, the type of the RTC
774 has to be selected, too. Define exactly one of the
777 CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
778 CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
779 CONFIG_RTC_MC146818 - use MC146818 RTC
780 CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
781 CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
782 CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
783 CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
784 CONFIG_RTC_DS164x - use Dallas DS164x RTC
785 CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
786 CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
787 CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
788 CONFIG_SYS_RV3029_TCR - enable trickle charger on
791 Note that if the RTC uses I2C, then the I2C interface
792 must also be configured. See I2C Support, below.
795 CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
797 The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
798 chip-ngpio pairs that tell the PCA953X driver the number of
799 pins supported by a particular chip.
801 Note that if the GPIO device uses I2C, then the I2C interface
802 must also be configured. See I2C Support, below.
805 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
806 accesses and can checksum them or write a list of them out
807 to memory. See the 'iotrace' command for details. This is
808 useful for testing device drivers since it can confirm that
809 the driver behaves the same way before and after a code
810 change. Currently this is supported on sandbox and arm. To
811 add support for your architecture, add '#include <iotrace.h>'
812 to the bottom of arch/<arch>/include/asm/io.h and test.
814 Example output from the 'iotrace stats' command is below.
815 Note that if the trace buffer is exhausted, the checksum will
816 still continue to operate.
819 Start: 10000000 (buffer start address)
820 Size: 00010000 (buffer size)
821 Offset: 00000120 (current buffer offset)
822 Output: 10000120 (start + offset)
823 Count: 00000018 (number of trace records)
824 CRC32: 9526fb66 (CRC32 of all trace records)
828 When CONFIG_TIMESTAMP is selected, the timestamp
829 (date and time) of an image is printed by image
830 commands like bootm or iminfo. This option is
831 automatically enabled when you select CONFIG_CMD_DATE .
833 - Partition Labels (disklabels) Supported:
834 Zero or more of the following:
835 CONFIG_MAC_PARTITION Apple's MacOS partition table.
836 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
837 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
838 bootloader. Note 2TB partition limit; see
840 CONFIG_SCSI) you must configure support for at
841 least one non-MTD partition type as well.
844 CONFIG_IDE_RESET_ROUTINE - this is defined in several
845 board configurations files but used nowhere!
847 CONFIG_IDE_RESET - is this is defined, IDE Reset will
848 be performed by calling the function
849 ide_set_reset(int reset)
850 which has to be defined in a board specific file
855 Set this to enable ATAPI support.
860 Set this to enable support for disks larger than 137GB
861 Also look at CONFIG_SYS_64BIT_LBA.
862 Whithout these , LBA48 support uses 32bit variables and will 'only'
863 support disks up to 2.1TB.
865 CONFIG_SYS_64BIT_LBA:
866 When enabled, makes the IDE subsystem use 64bit sector addresses.
870 CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
871 CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
872 CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
873 maximum numbers of LUNs, SCSI ID's and target
876 The environment variable 'scsidevs' is set to the number of
877 SCSI devices found during the last scan.
879 - NETWORK Support (PCI):
881 Support for Intel 8254x/8257x gigabit chips.
884 Utility code for direct access to the SPI bus on Intel 8257x.
885 This does not do anything useful unless you set at least one
886 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
888 CONFIG_E1000_SPI_GENERIC
889 Allow generic access to the SPI bus on the Intel 8257x, for
890 example with the "sspi" command.
893 Support for Intel 82557/82559/82559ER chips.
896 Support for Digital 2114x chips.
899 Support for National dp83815 chips.
902 Support for National dp8382[01] gigabit chips.
904 - NETWORK Support (other):
906 CONFIG_DRIVER_AT91EMAC
907 Support for AT91RM9200 EMAC.
910 Define this to use reduced MII inteface
912 CONFIG_DRIVER_AT91EMAC_QUIET
913 If this defined, the driver is quiet.
914 The driver doen't show link status messages.
917 Support for the Calxeda XGMAC device
920 Support for SMSC's LAN91C96 chips.
922 CONFIG_LAN91C96_USE_32_BIT
923 Define this to enable 32 bit addressing
926 Support for SMSC's LAN91C111 chip
929 Define this to hold the physical address
930 of the device (I/O space)
932 CONFIG_SMC_USE_32_BIT
933 Define this if data bus is 32 bits
935 CONFIG_SMC_USE_IOFUNCS
936 Define this to use i/o functions instead of macros
937 (some hardware wont work with macros)
939 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
940 Define this if you have more then 3 PHYs.
943 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
945 CONFIG_FTGMAC100_EGIGA
946 Define this to use GE link update with gigabit PHY.
947 Define this if FTGMAC100 is connected to gigabit PHY.
948 If your system has 10/100 PHY only, it might not occur
949 wrong behavior. Because PHY usually return timeout or
950 useless data when polling gigabit status and gigabit
951 control registers. This behavior won't affect the
952 correctnessof 10/100 link speed update.
955 Support for Renesas on-chip Ethernet controller
957 CONFIG_SH_ETHER_USE_PORT
958 Define the number of ports to be used
960 CONFIG_SH_ETHER_PHY_ADDR
961 Define the ETH PHY's address
963 CONFIG_SH_ETHER_CACHE_WRITEBACK
964 If this option is set, the driver enables cache flush.
970 CONFIG_TPM_TIS_INFINEON
971 Support for Infineon i2c bus TPM devices. Only one device
972 per system is supported at this time.
974 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
975 Define the burst count bytes upper limit
978 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
980 CONFIG_TPM_ST33ZP24_I2C
981 Support for STMicroelectronics ST33ZP24 I2C devices.
982 Requires TPM_ST33ZP24 and I2C.
984 CONFIG_TPM_ST33ZP24_SPI
985 Support for STMicroelectronics ST33ZP24 SPI devices.
986 Requires TPM_ST33ZP24 and SPI.
989 Support for Atmel TWI TPM device. Requires I2C support.
992 Support for generic parallel port TPM devices. Only one device
993 per system is supported at this time.
995 CONFIG_TPM_TIS_BASE_ADDRESS
996 Base address where the generic TPM device is mapped
997 to. Contemporary x86 systems usually map it at
1001 Define this to enable the TPM support library which provides
1002 functional interfaces to some TPM commands.
1003 Requires support for a TPM device.
1005 CONFIG_TPM_AUTH_SESSIONS
1006 Define this to enable authorized functions in the TPM library.
1007 Requires CONFIG_TPM and CONFIG_SHA1.
1010 At the moment only the UHCI host controller is
1011 supported (PIP405, MIP405); define
1012 CONFIG_USB_UHCI to enable it.
1013 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1014 and define CONFIG_USB_STORAGE to enable the USB
1017 Supported are USB Keyboards and USB Floppy drives
1020 CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1021 txfilltuning field in the EHCI controller on reset.
1023 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1024 HW module registers.
1027 Define the below if you wish to use the USB console.
1028 Once firmware is rebuilt from a serial console issue the
1029 command "setenv stdin usbtty; setenv stdout usbtty" and
1030 attach your USB cable. The Unix command "dmesg" should print
1031 it has found a new device. The environment variable usbtty
1032 can be set to gserial or cdc_acm to enable your device to
1033 appear to a USB host as a Linux gserial device or a
1034 Common Device Class Abstract Control Model serial device.
1035 If you select usbtty = gserial you should be able to enumerate
1037 # modprobe usbserial vendor=0xVendorID product=0xProductID
1038 else if using cdc_acm, simply setting the environment
1039 variable usbtty to be cdc_acm should suffice. The following
1040 might be defined in YourBoardName.h
1043 Define this to build a UDC device
1046 Define this to have a tty type of device available to
1047 talk to the UDC device
1050 Define this to enable the high speed support for usb
1051 device and usbtty. If this feature is enabled, a routine
1052 int is_usbd_high_speed(void)
1053 also needs to be defined by the driver to dynamically poll
1054 whether the enumeration has succeded at high speed or full
1057 CONFIG_SYS_CONSOLE_IS_IN_ENV
1058 Define this if you want stdin, stdout &/or stderr to
1061 If you have a USB-IF assigned VendorID then you may wish to
1062 define your own vendor specific values either in BoardName.h
1063 or directly in usbd_vendor_info.h. If you don't define
1064 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1065 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1066 should pretend to be a Linux device to it's target host.
1068 CONFIG_USBD_MANUFACTURER
1069 Define this string as the name of your company for
1070 - CONFIG_USBD_MANUFACTURER "my company"
1072 CONFIG_USBD_PRODUCT_NAME
1073 Define this string as the name of your product
1074 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1076 CONFIG_USBD_VENDORID
1077 Define this as your assigned Vendor ID from the USB
1078 Implementors Forum. This *must* be a genuine Vendor ID
1079 to avoid polluting the USB namespace.
1080 - CONFIG_USBD_VENDORID 0xFFFF
1082 CONFIG_USBD_PRODUCTID
1083 Define this as the unique Product ID
1085 - CONFIG_USBD_PRODUCTID 0xFFFF
1087 - ULPI Layer Support:
1088 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1089 the generic ULPI layer. The generic layer accesses the ULPI PHY
1090 via the platform viewport, so you need both the genric layer and
1091 the viewport enabled. Currently only Chipidea/ARC based
1092 viewport is supported.
1093 To enable the ULPI layer support, define CONFIG_USB_ULPI and
1094 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1095 If your ULPI phy needs a different reference clock than the
1096 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1097 the appropriate value in Hz.
1100 The MMC controller on the Intel PXA is supported. To
1101 enable this define CONFIG_MMC. The MMC can be
1102 accessed from the boot prompt by mapping the device
1103 to physical memory similar to flash. Command line is
1104 enabled with CONFIG_CMD_MMC. The MMC driver also works with
1105 the FAT fs. This is enabled with CONFIG_CMD_FAT.
1108 Support for Renesas on-chip MMCIF controller
1110 CONFIG_SH_MMCIF_ADDR
1111 Define the base address of MMCIF registers
1114 Define the clock frequency for MMCIF
1116 - USB Device Firmware Update (DFU) class support:
1118 This enables the USB portion of the DFU USB class
1121 This enables support for exposing NAND devices via DFU.
1124 This enables support for exposing RAM via DFU.
1125 Note: DFU spec refer to non-volatile memory usage, but
1126 allow usages beyond the scope of spec - here RAM usage,
1127 one that would help mostly the developer.
1129 CONFIG_SYS_DFU_DATA_BUF_SIZE
1130 Dfu transfer uses a buffer before writing data to the
1131 raw storage device. Make the size (in bytes) of this buffer
1132 configurable. The size of this buffer is also configurable
1133 through the "dfu_bufsiz" environment variable.
1135 CONFIG_SYS_DFU_MAX_FILE_SIZE
1136 When updating files rather than the raw storage device,
1137 we use a static buffer to copy the file into and then write
1138 the buffer once we've been given the whole file. Define
1139 this to the maximum filesize (in bytes) for the buffer.
1140 Default is 4 MiB if undefined.
1142 DFU_DEFAULT_POLL_TIMEOUT
1143 Poll timeout [ms], is the timeout a device can send to the
1144 host. The host must wait for this timeout before sending
1145 a subsequent DFU_GET_STATUS request to the device.
1147 DFU_MANIFEST_POLL_TIMEOUT
1148 Poll timeout [ms], which the device sends to the host when
1149 entering dfuMANIFEST state. Host waits this timeout, before
1150 sending again an USB request to the device.
1152 - Journaling Flash filesystem support:
1154 Define these for a default partition on a NAND device
1156 CONFIG_SYS_JFFS2_FIRST_SECTOR,
1157 CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1158 Define these for a default partition on a NOR device
1161 See Kconfig help for available keyboard drivers.
1165 Define this to enable a custom keyboard support.
1166 This simply calls drv_keyboard_init() which must be
1167 defined in your board-specific files. This option is deprecated
1168 and is only used by novena. For new boards, use driver model
1173 Enable the Freescale DIU video driver. Reference boards for
1174 SOCs that have a DIU should define this macro to enable DIU
1175 support, and should also define these other macros:
1180 CONFIG_VIDEO_SW_CURSOR
1181 CONFIG_VGA_AS_SINGLE_DEVICE
1183 CONFIG_VIDEO_BMP_LOGO
1185 The DIU driver will look for the 'video-mode' environment
1186 variable, and if defined, enable the DIU as a console during
1187 boot. See the documentation file doc/README.video for a
1188 description of this variable.
1190 - LCD Support: CONFIG_LCD
1192 Define this to enable LCD support (for output to LCD
1193 display); also select one of the supported displays
1194 by defining one of these:
1198 HITACHI TX09D70VM1CCA, 3.5", 240x320.
1200 CONFIG_NEC_NL6448AC33:
1202 NEC NL6448AC33-18. Active, color, single scan.
1204 CONFIG_NEC_NL6448BC20
1206 NEC NL6448BC20-08. 6.5", 640x480.
1207 Active, color, single scan.
1209 CONFIG_NEC_NL6448BC33_54
1211 NEC NL6448BC33-54. 10.4", 640x480.
1212 Active, color, single scan.
1216 Sharp 320x240. Active, color, single scan.
1217 It isn't 16x9, and I am not sure what it is.
1219 CONFIG_SHARP_LQ64D341
1221 Sharp LQ64D341 display, 640x480.
1222 Active, color, single scan.
1226 HLD1045 display, 640x480.
1227 Active, color, single scan.
1231 Optrex CBL50840-2 NF-FW 99 22 M5
1233 Hitachi LMG6912RPFC-00T
1237 320x240. Black & white.
1239 CONFIG_LCD_ALIGNMENT
1241 Normally the LCD is page-aligned (typically 4KB). If this is
1242 defined then the LCD will be aligned to this value instead.
1243 For ARM it is sometimes useful to use MMU_SECTION_SIZE
1244 here, since it is cheaper to change data cache settings on
1245 a per-section basis.
1250 Sometimes, for example if the display is mounted in portrait
1251 mode or even if it's mounted landscape but rotated by 180degree,
1252 we need to rotate our content of the display relative to the
1253 framebuffer, so that user can read the messages which are
1255 Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1256 initialized with a given rotation from "vl_rot" out of
1257 "vidinfo_t" which is provided by the board specific code.
1258 The value for vl_rot is coded as following (matching to
1259 fbcon=rotate:<n> linux-kernel commandline):
1260 0 = no rotation respectively 0 degree
1261 1 = 90 degree rotation
1262 2 = 180 degree rotation
1263 3 = 270 degree rotation
1265 If CONFIG_LCD_ROTATION is not defined, the console will be
1266 initialized with 0degree rotation.
1270 Support drawing of RLE8-compressed bitmaps on the LCD.
1274 Enables an 'i2c edid' command which can read EDID
1275 information over I2C from an attached LCD display.
1277 - Splash Screen Support: CONFIG_SPLASH_SCREEN
1279 If this option is set, the environment is checked for
1280 a variable "splashimage". If found, the usual display
1281 of logo, copyright and system information on the LCD
1282 is suppressed and the BMP image at the address
1283 specified in "splashimage" is loaded instead. The
1284 console is redirected to the "nulldev", too. This
1285 allows for a "silent" boot where a splash screen is
1286 loaded very quickly after power-on.
1288 CONFIG_SPLASHIMAGE_GUARD
1290 If this option is set, then U-Boot will prevent the environment
1291 variable "splashimage" from being set to a problematic address
1292 (see doc/README.displaying-bmps).
1293 This option is useful for targets where, due to alignment
1294 restrictions, an improperly aligned BMP image will cause a data
1295 abort. If you think you will not have problems with unaligned
1296 accesses (for example because your toolchain prevents them)
1297 there is no need to set this option.
1299 CONFIG_SPLASH_SCREEN_ALIGN
1301 If this option is set the splash image can be freely positioned
1302 on the screen. Environment variable "splashpos" specifies the
1303 position as "x,y". If a positive number is given it is used as
1304 number of pixel from left/top. If a negative number is given it
1305 is used as number of pixel from right/bottom. You can also
1306 specify 'm' for centering the image.
1309 setenv splashpos m,m
1310 => image at center of screen
1312 setenv splashpos 30,20
1313 => image at x = 30 and y = 20
1315 setenv splashpos -10,m
1316 => vertically centered image
1317 at x = dspWidth - bmpWidth - 9
1319 - Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1321 If this option is set, additionally to standard BMP
1322 images, gzipped BMP images can be displayed via the
1323 splashscreen support or the bmp command.
1325 - Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1327 If this option is set, 8-bit RLE compressed BMP images
1328 can be displayed via the splashscreen support or the
1332 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1334 The clock frequency of the MII bus
1336 CONFIG_PHY_RESET_DELAY
1338 Some PHY like Intel LXT971A need extra delay after
1339 reset before any MII register access is possible.
1340 For such PHY, set this option to the usec delay
1341 required. (minimum 300usec for LXT971A)
1343 CONFIG_PHY_CMD_DELAY (ppc4xx)
1345 Some PHY like Intel LXT971A need extra delay after
1346 command issued before MII status register can be read
1351 Define a default value for the IP address to use for
1352 the default Ethernet interface, in case this is not
1353 determined through e.g. bootp.
1354 (Environment variable "ipaddr")
1356 - Server IP address:
1359 Defines a default value for the IP address of a TFTP
1360 server to contact when using the "tftboot" command.
1361 (Environment variable "serverip")
1363 CONFIG_KEEP_SERVERADDR
1365 Keeps the server's MAC address, in the env 'serveraddr'
1366 for passing to bootargs (like Linux's netconsole option)
1368 - Gateway IP address:
1371 Defines a default value for the IP address of the
1372 default router where packets to other networks are
1374 (Environment variable "gatewayip")
1379 Defines a default value for the subnet mask (or
1380 routing prefix) which is used to determine if an IP
1381 address belongs to the local subnet or needs to be
1382 forwarded through a router.
1383 (Environment variable "netmask")
1385 - BOOTP Recovery Mode:
1386 CONFIG_BOOTP_RANDOM_DELAY
1388 If you have many targets in a network that try to
1389 boot using BOOTP, you may want to avoid that all
1390 systems send out BOOTP requests at precisely the same
1391 moment (which would happen for instance at recovery
1392 from a power failure, when all systems will try to
1393 boot, thus flooding the BOOTP server. Defining
1394 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1395 inserted before sending out BOOTP requests. The
1396 following delays are inserted then:
1398 1st BOOTP request: delay 0 ... 1 sec
1399 2nd BOOTP request: delay 0 ... 2 sec
1400 3rd BOOTP request: delay 0 ... 4 sec
1402 BOOTP requests: delay 0 ... 8 sec
1404 CONFIG_BOOTP_ID_CACHE_SIZE
1406 BOOTP packets are uniquely identified using a 32-bit ID. The
1407 server will copy the ID from client requests to responses and
1408 U-Boot will use this to determine if it is the destination of
1409 an incoming response. Some servers will check that addresses
1410 aren't in use before handing them out (usually using an ARP
1411 ping) and therefore take up to a few hundred milliseconds to
1412 respond. Network congestion may also influence the time it
1413 takes for a response to make it back to the client. If that
1414 time is too long, U-Boot will retransmit requests. In order
1415 to allow earlier responses to still be accepted after these
1416 retransmissions, U-Boot's BOOTP client keeps a small cache of
1417 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1418 cache. The default is to keep IDs for up to four outstanding
1419 requests. Increasing this will allow U-Boot to accept offers
1420 from a BOOTP client in networks with unusually high latency.
1422 - DHCP Advanced Options:
1423 You can fine tune the DHCP functionality by defining
1424 CONFIG_BOOTP_* symbols:
1426 CONFIG_BOOTP_NISDOMAIN
1427 CONFIG_BOOTP_BOOTFILESIZE
1428 CONFIG_BOOTP_SEND_HOSTNAME
1429 CONFIG_BOOTP_NTPSERVER
1430 CONFIG_BOOTP_TIMEOFFSET
1431 CONFIG_BOOTP_VENDOREX
1432 CONFIG_BOOTP_MAY_FAIL
1434 CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1435 environment variable, not the BOOTP server.
1437 CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1438 after the configured retry count, the call will fail
1439 instead of starting over. This can be used to fail over
1440 to Link-local IP address configuration if the DHCP server
1443 CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1444 to do a dynamic update of a DNS server. To do this, they
1445 need the hostname of the DHCP requester.
1446 If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1447 of the "hostname" environment variable is passed as
1448 option 12 to the DHCP server.
1450 CONFIG_BOOTP_DHCP_REQUEST_DELAY
1452 A 32bit value in microseconds for a delay between
1453 receiving a "DHCP Offer" and sending the "DHCP Request".
1454 This fixes a problem with certain DHCP servers that don't
1455 respond 100% of the time to a "DHCP request". E.g. On an
1456 AT91RM9200 processor running at 180MHz, this delay needed
1457 to be *at least* 15,000 usec before a Windows Server 2003
1458 DHCP server would reply 100% of the time. I recommend at
1459 least 50,000 usec to be safe. The alternative is to hope
1460 that one of the retries will be successful but note that
1461 the DHCP timeout and retry process takes a longer than
1464 - Link-local IP address negotiation:
1465 Negotiate with other link-local clients on the local network
1466 for an address that doesn't require explicit configuration.
1467 This is especially useful if a DHCP server cannot be guaranteed
1468 to exist in all environments that the device must operate.
1470 See doc/README.link-local for more information.
1472 - MAC address from environment variables
1474 FDT_SEQ_MACADDR_FROM_ENV
1476 Fix-up device tree with MAC addresses fetched sequentially from
1477 environment variables. This config work on assumption that
1478 non-usable ethernet node of device-tree are either not present
1479 or their status has been marked as "disabled".
1482 CONFIG_CDP_DEVICE_ID
1484 The device id used in CDP trigger frames.
1486 CONFIG_CDP_DEVICE_ID_PREFIX
1488 A two character string which is prefixed to the MAC address
1493 A printf format string which contains the ascii name of
1494 the port. Normally is set to "eth%d" which sets
1495 eth0 for the first Ethernet, eth1 for the second etc.
1497 CONFIG_CDP_CAPABILITIES
1499 A 32bit integer which indicates the device capabilities;
1500 0x00000010 for a normal host which does not forwards.
1504 An ascii string containing the version of the software.
1508 An ascii string containing the name of the platform.
1512 A 32bit integer sent on the trigger.
1514 CONFIG_CDP_POWER_CONSUMPTION
1516 A 16bit integer containing the power consumption of the
1517 device in .1 of milliwatts.
1519 CONFIG_CDP_APPLIANCE_VLAN_TYPE
1521 A byte containing the id of the VLAN.
1523 - Status LED: CONFIG_LED_STATUS
1525 Several configurations allow to display the current
1526 status using a LED. For instance, the LED will blink
1527 fast while running U-Boot code, stop blinking as
1528 soon as a reply to a BOOTP request was received, and
1529 start blinking slow once the Linux kernel is running
1530 (supported by a status LED driver in the Linux
1531 kernel). Defining CONFIG_LED_STATUS enables this
1536 CONFIG_LED_STATUS_GPIO
1537 The status LED can be connected to a GPIO pin.
1538 In such cases, the gpio_led driver can be used as a
1539 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1540 to include the gpio_led driver in the U-Boot binary.
1542 CONFIG_GPIO_LED_INVERTED_TABLE
1543 Some GPIO connected LEDs may have inverted polarity in which
1544 case the GPIO high value corresponds to LED off state and
1545 GPIO low value corresponds to LED on state.
1546 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1547 with a list of GPIO LEDs that have inverted polarity.
1549 - I2C Support: CONFIG_SYS_I2C
1551 This enable the NEW i2c subsystem, and will allow you to use
1552 i2c commands at the u-boot command line (as long as you set
1553 CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1554 for defining speed and slave address
1555 - activate second bus with I2C_SOFT_DECLARATIONS2 define
1556 CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1557 for defining speed and slave address
1558 - activate third bus with I2C_SOFT_DECLARATIONS3 define
1559 CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1560 for defining speed and slave address
1561 - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1562 CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1563 for defining speed and slave address
1565 - drivers/i2c/fsl_i2c.c:
1566 - activate i2c driver with CONFIG_SYS_I2C_FSL
1567 define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1568 offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1569 CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1571 - If your board supports a second fsl i2c bus, define
1572 CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1573 CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1574 CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1577 - drivers/i2c/tegra_i2c.c:
1578 - activate this driver with CONFIG_SYS_I2C_TEGRA
1579 - This driver adds 4 i2c buses with a fix speed from
1580 100000 and the slave addr 0!
1582 - drivers/i2c/ppc4xx_i2c.c
1583 - activate this driver with CONFIG_SYS_I2C_PPC4XX
1584 - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1585 - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1587 - drivers/i2c/i2c_mxc.c
1588 - activate this driver with CONFIG_SYS_I2C_MXC
1589 - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1590 - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1591 - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1592 - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1593 - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1594 - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1595 - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1596 - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1597 - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1598 - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1599 - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1600 - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1601 If those defines are not set, default value is 100000
1602 for speed, and 0 for slave.
1604 - drivers/i2c/rcar_i2c.c:
1605 - activate this driver with CONFIG_SYS_I2C_RCAR
1606 - This driver adds 4 i2c buses
1608 - drivers/i2c/sh_i2c.c:
1609 - activate this driver with CONFIG_SYS_I2C_SH
1610 - This driver adds from 2 to 5 i2c buses
1612 - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1613 - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1614 - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1615 - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1616 - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1617 - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1618 - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1619 - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1620 - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1621 - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1622 - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1624 - drivers/i2c/omap24xx_i2c.c
1625 - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1626 - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1627 - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1628 - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1629 - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1630 - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1631 - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1632 - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1633 - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1634 - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1635 - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1637 - drivers/i2c/s3c24x0_i2c.c:
1638 - activate this driver with CONFIG_SYS_I2C_S3C24X0
1639 - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1640 9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1641 with a fix speed from 100000 and the slave addr 0!
1643 - drivers/i2c/ihs_i2c.c
1644 - activate this driver with CONFIG_SYS_I2C_IHS
1645 - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1646 - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1647 - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1648 - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1649 - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1650 - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1651 - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1652 - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1653 - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1654 - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1655 - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1656 - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1657 - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1658 - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1659 - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1660 - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1661 - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1662 - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1663 - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1664 - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1665 - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1669 CONFIG_SYS_NUM_I2C_BUSES
1670 Hold the number of i2c buses you want to use.
1672 CONFIG_SYS_I2C_DIRECT_BUS
1673 define this, if you don't use i2c muxes on your hardware.
1674 if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1677 CONFIG_SYS_I2C_MAX_HOPS
1678 define how many muxes are maximal consecutively connected
1679 on one i2c bus. If you not use i2c muxes, omit this
1682 CONFIG_SYS_I2C_BUSES
1683 hold a list of buses you want to use, only used if
1684 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1685 a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1686 CONFIG_SYS_NUM_I2C_BUSES = 9:
1688 CONFIG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
1689 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1690 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1691 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1692 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1693 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1694 {1, {I2C_NULL_HOP}}, \
1695 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1696 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1700 bus 0 on adapter 0 without a mux
1701 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1702 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1703 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1704 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1705 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1706 bus 6 on adapter 1 without a mux
1707 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1708 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1710 If you do not have i2c muxes on your board, omit this define.
1712 - Legacy I2C Support:
1713 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1714 then the following macros need to be defined (examples are
1715 from include/configs/lwmon.h):
1719 (Optional). Any commands necessary to enable the I2C
1720 controller or configure ports.
1722 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
1726 The code necessary to make the I2C data line active
1727 (driven). If the data line is open collector, this
1730 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
1734 The code necessary to make the I2C data line tri-stated
1735 (inactive). If the data line is open collector, this
1738 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1742 Code that returns true if the I2C data line is high,
1745 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1749 If <bit> is true, sets the I2C data line high. If it
1750 is false, it clears it (low).
1752 eg: #define I2C_SDA(bit) \
1753 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
1754 else immr->im_cpm.cp_pbdat &= ~PB_SDA
1758 If <bit> is true, sets the I2C clock line high. If it
1759 is false, it clears it (low).
1761 eg: #define I2C_SCL(bit) \
1762 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
1763 else immr->im_cpm.cp_pbdat &= ~PB_SCL
1767 This delay is invoked four times per clock cycle so this
1768 controls the rate of data transfer. The data rate thus
1769 is 1 / (I2C_DELAY * 4). Often defined to be something
1772 #define I2C_DELAY udelay(2)
1774 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1776 If your arch supports the generic GPIO framework (asm/gpio.h),
1777 then you may alternatively define the two GPIOs that are to be
1778 used as SCL / SDA. Any of the previous I2C_xxx macros will
1779 have GPIO-based defaults assigned to them as appropriate.
1781 You should define these to the GPIO value as given directly to
1782 the generic GPIO functions.
1784 CONFIG_SYS_I2C_INIT_BOARD
1786 When a board is reset during an i2c bus transfer
1787 chips might think that the current transfer is still
1788 in progress. On some boards it is possible to access
1789 the i2c SCLK line directly, either by using the
1790 processor pin as a GPIO or by having a second pin
1791 connected to the bus. If this option is defined a
1792 custom i2c_init_board() routine in boards/xxx/board.c
1793 is run early in the boot sequence.
1795 CONFIG_I2C_MULTI_BUS
1797 This option allows the use of multiple I2C buses, each of which
1798 must have a controller. At any point in time, only one bus is
1799 active. To switch to a different bus, use the 'i2c dev' command.
1800 Note that bus numbering is zero-based.
1802 CONFIG_SYS_I2C_NOPROBES
1804 This option specifies a list of I2C devices that will be skipped
1805 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
1806 is set, specify a list of bus-device pairs. Otherwise, specify
1807 a 1D array of device addresses
1810 #undef CONFIG_I2C_MULTI_BUS
1811 #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1813 will skip addresses 0x50 and 0x68 on a board with one I2C bus
1815 #define CONFIG_I2C_MULTI_BUS
1816 #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1818 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1820 CONFIG_SYS_SPD_BUS_NUM
1822 If defined, then this indicates the I2C bus number for DDR SPD.
1823 If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1825 CONFIG_SYS_RTC_BUS_NUM
1827 If defined, then this indicates the I2C bus number for the RTC.
1828 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1830 CONFIG_SOFT_I2C_READ_REPEATED_START
1832 defining this will force the i2c_read() function in
1833 the soft_i2c driver to perform an I2C repeated start
1834 between writing the address pointer and reading the
1835 data. If this define is omitted the default behaviour
1836 of doing a stop-start sequence will be used. Most I2C
1837 devices can use either method, but some require one or
1840 - SPI Support: CONFIG_SPI
1842 Enables SPI driver (so far only tested with
1843 SPI EEPROM, also an instance works with Crystal A/D and
1844 D/As on the SACSng board)
1848 Enables a software (bit-bang) SPI driver rather than
1849 using hardware support. This is a general purpose
1850 driver that only requires three general I/O port pins
1851 (two outputs, one input) to function. If this is
1852 defined, the board configuration must define several
1853 SPI configuration items (port pins to use, etc). For
1854 an example, see include/configs/sacsng.h.
1856 CONFIG_SYS_SPI_MXC_WAIT
1857 Timeout for waiting until spi transfer completed.
1858 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1860 - FPGA Support: CONFIG_FPGA
1862 Enables FPGA subsystem.
1864 CONFIG_FPGA_<vendor>
1866 Enables support for specific chip vendors.
1869 CONFIG_FPGA_<family>
1871 Enables support for FPGA family.
1872 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1876 Specify the number of FPGA devices to support.
1878 CONFIG_SYS_FPGA_PROG_FEEDBACK
1880 Enable printing of hash marks during FPGA configuration.
1882 CONFIG_SYS_FPGA_CHECK_BUSY
1884 Enable checks on FPGA configuration interface busy
1885 status by the configuration function. This option
1886 will require a board or device specific function to
1891 If defined, a function that provides delays in the FPGA
1892 configuration driver.
1894 CONFIG_SYS_FPGA_CHECK_CTRLC
1895 Allow Control-C to interrupt FPGA configuration
1897 CONFIG_SYS_FPGA_CHECK_ERROR
1899 Check for configuration errors during FPGA bitfile
1900 loading. For example, abort during Virtex II
1901 configuration if the INIT_B line goes low (which
1902 indicated a CRC error).
1904 CONFIG_SYS_FPGA_WAIT_INIT
1906 Maximum time to wait for the INIT_B line to de-assert
1907 after PROB_B has been de-asserted during a Virtex II
1908 FPGA configuration sequence. The default time is 500
1911 CONFIG_SYS_FPGA_WAIT_BUSY
1913 Maximum time to wait for BUSY to de-assert during
1914 Virtex II FPGA configuration. The default is 5 ms.
1916 CONFIG_SYS_FPGA_WAIT_CONFIG
1918 Time to wait after FPGA configuration. The default is
1921 - Configuration Management:
1925 If defined, this string will be added to the U-Boot
1926 version information (U_BOOT_VERSION)
1928 - Vendor Parameter Protection:
1930 U-Boot considers the values of the environment
1931 variables "serial#" (Board Serial Number) and
1932 "ethaddr" (Ethernet Address) to be parameters that
1933 are set once by the board vendor / manufacturer, and
1934 protects these variables from casual modification by
1935 the user. Once set, these variables are read-only,
1936 and write or delete attempts are rejected. You can
1937 change this behaviour:
1939 If CONFIG_ENV_OVERWRITE is #defined in your config
1940 file, the write protection for vendor parameters is
1941 completely disabled. Anybody can change or delete
1944 Alternatively, if you define _both_ an ethaddr in the
1945 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1946 Ethernet address is installed in the environment,
1947 which can be changed exactly ONCE by the user. [The
1948 serial# is unaffected by this, i. e. it remains
1951 The same can be accomplished in a more flexible way
1952 for any variable by configuring the type of access
1953 to allow for those variables in the ".flags" variable
1954 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1959 Define this variable to enable the reservation of
1960 "protected RAM", i. e. RAM which is not overwritten
1961 by U-Boot. Define CONFIG_PRAM to hold the number of
1962 kB you want to reserve for pRAM. You can overwrite
1963 this default value by defining an environment
1964 variable "pram" to the number of kB you want to
1965 reserve. Note that the board info structure will
1966 still show the full amount of RAM. If pRAM is
1967 reserved, a new environment variable "mem" will
1968 automatically be defined to hold the amount of
1969 remaining RAM in a form that can be passed as boot
1970 argument to Linux, for instance like that:
1972 setenv bootargs ... mem=\${mem}
1975 This way you can tell Linux not to use this memory,
1976 either, which results in a memory region that will
1977 not be affected by reboots.
1979 *WARNING* If your board configuration uses automatic
1980 detection of the RAM size, you must make sure that
1981 this memory test is non-destructive. So far, the
1982 following board configurations are known to be
1985 IVMS8, IVML24, SPD8xx,
1986 HERMES, IP860, RPXlite, LWMON,
1989 - Access to physical memory region (> 4GB)
1990 Some basic support is provided for operations on memory not
1991 normally accessible to U-Boot - e.g. some architectures
1992 support access to more than 4GB of memory on 32-bit
1993 machines using physical address extension or similar.
1994 Define CONFIG_PHYSMEM to access this basic support, which
1995 currently only supports clearing the memory.
1998 CONFIG_NET_RETRY_COUNT
2000 This variable defines the number of retries for
2001 network operations like ARP, RARP, TFTP, or BOOTP
2002 before giving up the operation. If not defined, a
2003 default value of 5 is used.
2007 Timeout waiting for an ARP reply in milliseconds.
2011 Timeout in milliseconds used in NFS protocol.
2012 If you encounter "ERROR: Cannot umount" in nfs command,
2013 try longer timeout such as
2014 #define CONFIG_NFS_TIMEOUT 10000UL
2016 - Command Interpreter:
2017 CONFIG_SYS_PROMPT_HUSH_PS2
2019 This defines the secondary prompt string, which is
2020 printed when the command interpreter needs more input
2021 to complete a command. Usually "> ".
2025 In the current implementation, the local variables
2026 space and global environment variables space are
2027 separated. Local variables are those you define by
2028 simply typing `name=value'. To access a local
2029 variable later on, you have write `$name' or
2030 `${name}'; to execute the contents of a variable
2031 directly type `$name' at the command prompt.
2033 Global environment variables are those you use
2034 setenv/printenv to work with. To run a command stored
2035 in such a variable, you need to use the run command,
2036 and you must not use the '$' sign to access them.
2038 To store commands and special characters in a
2039 variable, please use double quotation marks
2040 surrounding the whole text of the variable, instead
2041 of the backslashes before semicolons and special
2044 - Command Line Editing and History:
2045 CONFIG_CMDLINE_PS_SUPPORT
2047 Enable support for changing the command prompt string
2048 at run-time. Only static string is supported so far.
2049 The string is obtained from environment variables PS1
2052 - Default Environment:
2053 CONFIG_EXTRA_ENV_SETTINGS
2055 Define this to contain any number of null terminated
2056 strings (variable = value pairs) that will be part of
2057 the default environment compiled into the boot image.
2059 For example, place something like this in your
2060 board's config file:
2062 #define CONFIG_EXTRA_ENV_SETTINGS \
2066 Warning: This method is based on knowledge about the
2067 internal format how the environment is stored by the
2068 U-Boot code. This is NOT an official, exported
2069 interface! Although it is unlikely that this format
2070 will change soon, there is no guarantee either.
2071 You better know what you are doing here.
2073 Note: overly (ab)use of the default environment is
2074 discouraged. Make sure to check other ways to preset
2075 the environment like the "source" command or the
2078 CONFIG_DELAY_ENVIRONMENT
2080 Normally the environment is loaded when the board is
2081 initialised so that it is available to U-Boot. This inhibits
2082 that so that the environment is not available until
2083 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2084 this is instead controlled by the value of
2085 /config/load-environment.
2087 - TFTP Fixed UDP Port:
2090 If this is defined, the environment variable tftpsrcp
2091 is used to supply the TFTP UDP source port value.
2092 If tftpsrcp isn't defined, the normal pseudo-random port
2093 number generator is used.
2095 Also, the environment variable tftpdstp is used to supply
2096 the TFTP UDP destination port value. If tftpdstp isn't
2097 defined, the normal port 69 is used.
2099 The purpose for tftpsrcp is to allow a TFTP server to
2100 blindly start the TFTP transfer using the pre-configured
2101 target IP address and UDP port. This has the effect of
2102 "punching through" the (Windows XP) firewall, allowing
2103 the remainder of the TFTP transfer to proceed normally.
2104 A better solution is to properly configure the firewall,
2105 but sometimes that is not allowed.
2107 CONFIG_STANDALONE_LOAD_ADDR
2109 This option defines a board specific value for the
2110 address where standalone program gets loaded, thus
2111 overwriting the architecture dependent default
2114 - Frame Buffer Address:
2117 Define CONFIG_FB_ADDR if you want to use specific
2118 address for frame buffer. This is typically the case
2119 when using a graphics controller has separate video
2120 memory. U-Boot will then place the frame buffer at
2121 the given address instead of dynamically reserving it
2122 in system RAM by calling lcd_setmem(), which grabs
2123 the memory for the frame buffer depending on the
2124 configured panel size.
2126 Please see board_init_f function.
2128 - Automatic software updates via TFTP server
2130 CONFIG_UPDATE_TFTP_CNT_MAX
2131 CONFIG_UPDATE_TFTP_MSEC_MAX
2133 These options enable and control the auto-update feature;
2134 for a more detailed description refer to doc/README.update.
2136 - MTD Support (mtdparts command, UBI support)
2137 CONFIG_MTD_UBI_WL_THRESHOLD
2138 This parameter defines the maximum difference between the highest
2139 erase counter value and the lowest erase counter value of eraseblocks
2140 of UBI devices. When this threshold is exceeded, UBI starts performing
2141 wear leveling by means of moving data from eraseblock with low erase
2142 counter to eraseblocks with high erase counter.
2144 The default value should be OK for SLC NAND flashes, NOR flashes and
2145 other flashes which have eraseblock life-cycle 100000 or more.
2146 However, in case of MLC NAND flashes which typically have eraseblock
2147 life-cycle less than 10000, the threshold should be lessened (e.g.,
2148 to 128 or 256, although it does not have to be power of 2).
2152 CONFIG_MTD_UBI_BEB_LIMIT
2153 This option specifies the maximum bad physical eraseblocks UBI
2154 expects on the MTD device (per 1024 eraseblocks). If the
2155 underlying flash does not admit of bad eraseblocks (e.g. NOR
2156 flash), this value is ignored.
2158 NAND datasheets often specify the minimum and maximum NVM
2159 (Number of Valid Blocks) for the flashes' endurance lifetime.
2160 The maximum expected bad eraseblocks per 1024 eraseblocks
2161 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2162 which gives 20 for most NANDs (MaxNVB is basically the total
2163 count of eraseblocks on the chip).
2165 To put it differently, if this value is 20, UBI will try to
2166 reserve about 1.9% of physical eraseblocks for bad blocks
2167 handling. And that will be 1.9% of eraseblocks on the entire
2168 NAND chip, not just the MTD partition UBI attaches. This means
2169 that if you have, say, a NAND flash chip admits maximum 40 bad
2170 eraseblocks, and it is split on two MTD partitions of the same
2171 size, UBI will reserve 40 eraseblocks when attaching a
2176 CONFIG_MTD_UBI_FASTMAP
2177 Fastmap is a mechanism which allows attaching an UBI device
2178 in nearly constant time. Instead of scanning the whole MTD device it
2179 only has to locate a checkpoint (called fastmap) on the device.
2180 The on-flash fastmap contains all information needed to attach
2181 the device. Using fastmap makes only sense on large devices where
2182 attaching by scanning takes long. UBI will not automatically install
2183 a fastmap on old images, but you can set the UBI parameter
2184 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2185 that fastmap-enabled images are still usable with UBI implementations
2186 without fastmap support. On typical flash devices the whole fastmap
2187 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2189 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2190 Set this parameter to enable fastmap automatically on images
2194 CONFIG_MTD_UBI_FM_DEBUG
2195 Enable UBI fastmap debug
2200 Enable building of SPL globally.
2203 LDSCRIPT for linking the SPL binary.
2205 CONFIG_SPL_MAX_FOOTPRINT
2206 Maximum size in memory allocated to the SPL, BSS included.
2207 When defined, the linker checks that the actual memory
2208 used by SPL from _start to __bss_end does not exceed it.
2209 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2210 must not be both defined at the same time.
2213 Maximum size of the SPL image (text, data, rodata, and
2214 linker lists sections), BSS excluded.
2215 When defined, the linker checks that the actual size does
2218 CONFIG_SPL_RELOC_TEXT_BASE
2219 Address to relocate to. If unspecified, this is equal to
2220 CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2222 CONFIG_SPL_BSS_START_ADDR
2223 Link address for the BSS within the SPL binary.
2225 CONFIG_SPL_BSS_MAX_SIZE
2226 Maximum size in memory allocated to the SPL BSS.
2227 When defined, the linker checks that the actual memory used
2228 by SPL from __bss_start to __bss_end does not exceed it.
2229 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2230 must not be both defined at the same time.
2233 Adress of the start of the stack SPL will use
2235 CONFIG_SPL_PANIC_ON_RAW_IMAGE
2236 When defined, SPL will panic() if the image it has
2237 loaded does not have a signature.
2238 Defining this is useful when code which loads images
2239 in SPL cannot guarantee that absolutely all read errors
2241 An example is the LPC32XX MLC NAND driver, which will
2242 consider that a completely unreadable NAND block is bad,
2243 and thus should be skipped silently.
2245 CONFIG_SPL_RELOC_STACK
2246 Adress of the start of the stack SPL will use after
2247 relocation. If unspecified, this is equal to
2250 CONFIG_SYS_SPL_MALLOC_START
2251 Starting address of the malloc pool used in SPL.
2252 When this option is set the full malloc is used in SPL and
2253 it is set up by spl_init() and before that, the simple malloc()
2254 can be used if CONFIG_SYS_MALLOC_F is defined.
2256 CONFIG_SYS_SPL_MALLOC_SIZE
2257 The size of the malloc pool used in SPL.
2260 Enable booting directly to an OS from SPL.
2261 See also: doc/README.falcon
2263 CONFIG_SPL_DISPLAY_PRINT
2264 For ARM, enable an optional function to print more information
2265 about the running system.
2267 CONFIG_SPL_INIT_MINIMAL
2268 Arch init code should be built for a very small image
2270 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2271 Partition on the MMC to load U-Boot from when the MMC is being
2274 CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2275 Sector to load kernel uImage from when MMC is being
2276 used in raw mode (for Falcon mode)
2278 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2279 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2280 Sector and number of sectors to load kernel argument
2281 parameters from when MMC is being used in raw mode
2284 CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2285 Partition on the MMC to load U-Boot from when the MMC is being
2288 CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2289 Filename to read to load U-Boot when reading from filesystem
2291 CONFIG_SPL_FS_LOAD_KERNEL_NAME
2292 Filename to read to load kernel uImage when reading
2293 from filesystem (for Falcon mode)
2295 CONFIG_SPL_FS_LOAD_ARGS_NAME
2296 Filename to read to load kernel argument parameters
2297 when reading from filesystem (for Falcon mode)
2299 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2300 Set this for NAND SPL on PPC mpc83xx targets, so that
2301 start.S waits for the rest of the SPL to load before
2302 continuing (the hardware starts execution after just
2303 loading the first page rather than the full 4K).
2305 CONFIG_SPL_SKIP_RELOCATE
2306 Avoid SPL relocation
2308 CONFIG_SPL_NAND_BASE
2309 Include nand_base.c in the SPL. Requires
2310 CONFIG_SPL_NAND_DRIVERS.
2312 CONFIG_SPL_NAND_DRIVERS
2313 SPL uses normal NAND drivers, not minimal drivers.
2315 CONFIG_SPL_NAND_IDENT
2316 SPL uses the chip ID list to identify the NAND flash.
2317 Requires CONFIG_SPL_NAND_BASE.
2320 Include standard software ECC in the SPL
2322 CONFIG_SPL_NAND_SIMPLE
2323 Support for NAND boot using simple NAND drivers that
2324 expose the cmd_ctrl() interface.
2327 Support for a lightweight UBI (fastmap) scanner and
2330 CONFIG_SPL_NAND_RAW_ONLY
2331 Support to boot only raw u-boot.bin images. Use this only
2332 if you need to save space.
2334 CONFIG_SPL_COMMON_INIT_DDR
2335 Set for common ddr init with serial presence detect in
2338 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2339 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2340 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2341 CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2342 CONFIG_SYS_NAND_ECCBYTES
2343 Defines the size and behavior of the NAND that SPL uses
2346 CONFIG_SYS_NAND_U_BOOT_OFFS
2347 Location in NAND to read U-Boot from
2349 CONFIG_SYS_NAND_U_BOOT_DST
2350 Location in memory to load U-Boot to
2352 CONFIG_SYS_NAND_U_BOOT_SIZE
2353 Size of image to load
2355 CONFIG_SYS_NAND_U_BOOT_START
2356 Entry point in loaded image to jump to
2358 CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2359 Define this if you need to first read the OOB and then the
2360 data. This is used, for example, on davinci platforms.
2362 CONFIG_SPL_RAM_DEVICE
2363 Support for running image already present in ram, in SPL binary
2366 Image offset to which the SPL should be padded before appending
2367 the SPL payload. By default, this is defined as
2368 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2369 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2370 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2373 Final target image containing SPL and payload. Some SPLs
2374 use an arch-specific makefile fragment instead, for
2375 example if more than one image needs to be produced.
2377 CONFIG_SPL_FIT_PRINT
2378 Printing information about a FIT image adds quite a bit of
2379 code to SPL. So this is normally disabled in SPL. Use this
2380 option to re-enable it. This will affect the output of the
2381 bootm command when booting a FIT image.
2385 Enable building of TPL globally.
2388 Image offset to which the TPL should be padded before appending
2389 the TPL payload. By default, this is defined as
2390 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2391 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2392 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2394 - Interrupt support (PPC):
2396 There are common interrupt_init() and timer_interrupt()
2397 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2398 for CPU specific initialization. interrupt_init_cpu()
2399 should set decrementer_count to appropriate value. If
2400 CPU resets decrementer automatically after interrupt
2401 (ppc4xx) it should set decrementer_count to zero.
2402 timer_interrupt() calls timer_interrupt_cpu() for CPU
2403 specific handling. If board has watchdog / status_led
2404 / other_activity_monitor it works automatically from
2405 general timer_interrupt().
2408 Board initialization settings:
2409 ------------------------------
2411 During Initialization u-boot calls a number of board specific functions
2412 to allow the preparation of board specific prerequisites, e.g. pin setup
2413 before drivers are initialized. To enable these callbacks the
2414 following configuration macros have to be defined. Currently this is
2415 architecture specific, so please check arch/your_architecture/lib/board.c
2416 typically in board_init_f() and board_init_r().
2418 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2419 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2420 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
2421 - CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2423 Configuration Settings:
2424 -----------------------
2426 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2427 Optionally it can be defined to support 64-bit memory commands.
2429 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2430 undefine this when you're short of memory.
2432 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2433 width of the commands listed in the 'help' command output.
2435 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
2436 prompt for user input.
2438 - CONFIG_SYS_CBSIZE: Buffer size for input from the Console
2440 - CONFIG_SYS_PBSIZE: Buffer size for Console output
2442 - CONFIG_SYS_MAXARGS: max. Number of arguments accepted for monitor commands
2444 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2445 the application (usually a Linux kernel) when it is
2448 - CONFIG_SYS_BAUDRATE_TABLE:
2449 List of legal baudrate settings for this board.
2451 - CONFIG_SYS_MEM_RESERVE_SECURE
2452 Only implemented for ARMv8 for now.
2453 If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2454 is substracted from total RAM and won't be reported to OS.
2455 This memory can be used as secure memory. A variable
2456 gd->arch.secure_ram is used to track the location. In systems
2457 the RAM base is not zero, or RAM is divided into banks,
2458 this variable needs to be recalcuated to get the address.
2460 - CONFIG_SYS_MEM_TOP_HIDE:
2461 If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2462 this specified memory area will get subtracted from the top
2463 (end) of RAM and won't get "touched" at all by U-Boot. By
2464 fixing up gd->ram_size the Linux kernel should gets passed
2465 the now "corrected" memory size and won't touch it either.
2466 This should work for arch/ppc and arch/powerpc. Only Linux
2467 board ports in arch/powerpc with bootwrapper support that
2468 recalculate the memory size from the SDRAM controller setup
2469 will have to get fixed in Linux additionally.
2471 This option can be used as a workaround for the 440EPx/GRx
2472 CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2475 WARNING: Please make sure that this value is a multiple of
2476 the Linux page size (normally 4k). If this is not the case,
2477 then the end address of the Linux memory will be located at a
2478 non page size aligned address and this could cause major
2481 - CONFIG_SYS_LOADS_BAUD_CHANGE:
2482 Enable temporary baudrate change while serial download
2484 - CONFIG_SYS_SDRAM_BASE:
2485 Physical start address of SDRAM. _Must_ be 0 here.
2487 - CONFIG_SYS_FLASH_BASE:
2488 Physical start address of Flash memory.
2490 - CONFIG_SYS_MONITOR_BASE:
2491 Physical start address of boot monitor code (set by
2492 make config files to be same as the text base address
2493 (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2494 CONFIG_SYS_FLASH_BASE when booting from flash.
2496 - CONFIG_SYS_MONITOR_LEN:
2497 Size of memory reserved for monitor code, used to
2498 determine _at_compile_time_ (!) if the environment is
2499 embedded within the U-Boot image, or in a separate
2502 - CONFIG_SYS_MALLOC_LEN:
2503 Size of DRAM reserved for malloc() use.
2505 - CONFIG_SYS_MALLOC_F_LEN
2506 Size of the malloc() pool for use before relocation. If
2507 this is defined, then a very simple malloc() implementation
2508 will become available before relocation. The address is just
2509 below the global data, and the stack is moved down to make
2512 This feature allocates regions with increasing addresses
2513 within the region. calloc() is supported, but realloc()
2514 is not available. free() is supported but does nothing.
2515 The memory will be freed (or in fact just forgotten) when
2516 U-Boot relocates itself.
2518 - CONFIG_SYS_MALLOC_SIMPLE
2519 Provides a simple and small malloc() and calloc() for those
2520 boards which do not use the full malloc in SPL (which is
2521 enabled with CONFIG_SYS_SPL_MALLOC_START).
2523 - CONFIG_SYS_NONCACHED_MEMORY:
2524 Size of non-cached memory area. This area of memory will be
2525 typically located right below the malloc() area and mapped
2526 uncached in the MMU. This is useful for drivers that would
2527 otherwise require a lot of explicit cache maintenance. For
2528 some drivers it's also impossible to properly maintain the
2529 cache. For example if the regions that need to be flushed
2530 are not a multiple of the cache-line size, *and* padding
2531 cannot be allocated between the regions to align them (i.e.
2532 if the HW requires a contiguous array of regions, and the
2533 size of each region is not cache-aligned), then a flush of
2534 one region may result in overwriting data that hardware has
2535 written to another region in the same cache-line. This can
2536 happen for example in network drivers where descriptors for
2537 buffers are typically smaller than the CPU cache-line (e.g.
2538 16 bytes vs. 32 or 64 bytes).
2540 Non-cached memory is only supported on 32-bit ARM at present.
2542 - CONFIG_SYS_BOOTM_LEN:
2543 Normally compressed uImages are limited to an
2544 uncompressed size of 8 MBytes. If this is not enough,
2545 you can define CONFIG_SYS_BOOTM_LEN in your board config file
2546 to adjust this setting to your needs.
2548 - CONFIG_SYS_BOOTMAPSZ:
2549 Maximum size of memory mapped by the startup code of
2550 the Linux kernel; all data that must be processed by
2551 the Linux kernel (bd_info, boot arguments, FDT blob if
2552 used) must be put below this limit, unless "bootm_low"
2553 environment variable is defined and non-zero. In such case
2554 all data for the Linux kernel must be between "bootm_low"
2555 and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
2556 variable "bootm_mapsize" will override the value of
2557 CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
2558 then the value in "bootm_size" will be used instead.
2560 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
2561 Enable initrd_high functionality. If defined then the
2562 initrd_high feature is enabled and the bootm ramdisk subcommand
2565 - CONFIG_SYS_BOOT_GET_CMDLINE:
2566 Enables allocating and saving kernel cmdline in space between
2567 "bootm_low" and "bootm_low" + BOOTMAPSZ.
2569 - CONFIG_SYS_BOOT_GET_KBD:
2570 Enables allocating and saving a kernel copy of the bd_info in
2571 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2573 - CONFIG_SYS_MAX_FLASH_BANKS:
2574 Max number of Flash memory banks
2576 - CONFIG_SYS_MAX_FLASH_SECT:
2577 Max number of sectors on a Flash chip
2579 - CONFIG_SYS_FLASH_ERASE_TOUT:
2580 Timeout for Flash erase operations (in ms)
2582 - CONFIG_SYS_FLASH_WRITE_TOUT:
2583 Timeout for Flash write operations (in ms)
2585 - CONFIG_SYS_FLASH_LOCK_TOUT
2586 Timeout for Flash set sector lock bit operation (in ms)
2588 - CONFIG_SYS_FLASH_UNLOCK_TOUT
2589 Timeout for Flash clear lock bits operation (in ms)
2591 - CONFIG_SYS_FLASH_PROTECTION
2592 If defined, hardware flash sectors protection is used
2593 instead of U-Boot software protection.
2595 - CONFIG_SYS_DIRECT_FLASH_TFTP:
2597 Enable TFTP transfers directly to flash memory;
2598 without this option such a download has to be
2599 performed in two steps: (1) download to RAM, and (2)
2600 copy from RAM to flash.
2602 The two-step approach is usually more reliable, since
2603 you can check if the download worked before you erase
2604 the flash, but in some situations (when system RAM is
2605 too limited to allow for a temporary copy of the
2606 downloaded image) this option may be very useful.
2608 - CONFIG_SYS_FLASH_CFI:
2609 Define if the flash driver uses extra elements in the
2610 common flash structure for storing flash geometry.
2612 - CONFIG_FLASH_CFI_DRIVER
2613 This option also enables the building of the cfi_flash driver
2614 in the drivers directory
2616 - CONFIG_FLASH_CFI_MTD
2617 This option enables the building of the cfi_mtd driver
2618 in the drivers directory. The driver exports CFI flash
2621 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2622 Use buffered writes to flash.
2624 - CONFIG_FLASH_SPANSION_S29WS_N
2625 s29ws-n MirrorBit flash has non-standard addresses for buffered
2628 - CONFIG_SYS_FLASH_QUIET_TEST
2629 If this option is defined, the common CFI flash doesn't
2630 print it's warning upon not recognized FLASH banks. This
2631 is useful, if some of the configured banks are only
2632 optionally available.
2634 - CONFIG_FLASH_SHOW_PROGRESS
2635 If defined (must be an integer), print out countdown
2636 digits and dots. Recommended value: 45 (9..1) for 80
2637 column displays, 15 (3..1) for 40 column displays.
2639 - CONFIG_FLASH_VERIFY
2640 If defined, the content of the flash (destination) is compared
2641 against the source after the write operation. An error message
2642 will be printed when the contents are not identical.
2643 Please note that this option is useless in nearly all cases,
2644 since such flash programming errors usually are detected earlier
2645 while unprotecting/erasing/programming. Please only enable
2646 this option if you really know what you are doing.
2648 - CONFIG_SYS_RX_ETH_BUFFER:
2649 Defines the number of Ethernet receive buffers. On some
2650 Ethernet controllers it is recommended to set this value
2651 to 8 or even higher (EEPRO100 or 405 EMAC), since all
2652 buffers can be full shortly after enabling the interface
2653 on high Ethernet traffic.
2654 Defaults to 4 if not defined.
2656 - CONFIG_ENV_MAX_ENTRIES
2658 Maximum number of entries in the hash table that is used
2659 internally to store the environment settings. The default
2660 setting is supposed to be generous and should work in most
2661 cases. This setting can be used to tune behaviour; see
2662 lib/hashtable.c for details.
2664 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2665 - CONFIG_ENV_FLAGS_LIST_STATIC
2666 Enable validation of the values given to environment variables when
2667 calling env set. Variables can be restricted to only decimal,
2668 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
2669 the variables can also be restricted to IP address or MAC address.
2671 The format of the list is:
2672 type_attribute = [s|d|x|b|i|m]
2673 access_attribute = [a|r|o|c]
2674 attributes = type_attribute[access_attribute]
2675 entry = variable_name[:attributes]
2678 The type attributes are:
2679 s - String (default)
2682 b - Boolean ([1yYtT|0nNfF])
2686 The access attributes are:
2692 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2693 Define this to a list (string) to define the ".flags"
2694 environment variable in the default or embedded environment.
2696 - CONFIG_ENV_FLAGS_LIST_STATIC
2697 Define this to a list (string) to define validation that
2698 should be done if an entry is not found in the ".flags"
2699 environment variable. To override a setting in the static
2700 list, simply add an entry for the same variable name to the
2703 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2704 regular expression. This allows multiple variables to define the same
2705 flags without explicitly listing them for each variable.
2707 The following definitions that deal with the placement and management
2708 of environment data (variable area); in general, we support the
2709 following configurations:
2711 - CONFIG_BUILD_ENVCRC:
2713 Builds up envcrc with the target environment so that external utils
2714 may easily extract it and embed it in final U-Boot images.
2716 BE CAREFUL! The first access to the environment happens quite early
2717 in U-Boot initialization (when we try to get the setting of for the
2718 console baudrate). You *MUST* have mapped your NVRAM area then, or
2721 Please note that even with NVRAM we still use a copy of the
2722 environment in RAM: we could work on NVRAM directly, but we want to
2723 keep settings there always unmodified except somebody uses "saveenv"
2724 to save the current settings.
2726 BE CAREFUL! For some special cases, the local device can not use
2727 "saveenv" command. For example, the local device will get the
2728 environment stored in a remote NOR flash by SRIO or PCIE link,
2729 but it can not erase, write this NOR flash by SRIO or PCIE interface.
2731 - CONFIG_NAND_ENV_DST
2733 Defines address in RAM to which the nand_spl code should copy the
2734 environment. If redundant environment is used, it will be copied to
2735 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2737 Please note that the environment is read-only until the monitor
2738 has been relocated to RAM and a RAM copy of the environment has been
2739 created; also, when using EEPROM you will have to use env_get_f()
2740 until then to read environment variables.
2742 The environment is protected by a CRC32 checksum. Before the monitor
2743 is relocated into RAM, as a result of a bad CRC you will be working
2744 with the compiled-in default environment - *silently*!!! [This is
2745 necessary, because the first environment variable we need is the
2746 "baudrate" setting for the console - if we have a bad CRC, we don't
2747 have any device yet where we could complain.]
2749 Note: once the monitor has been relocated, then it will complain if
2750 the default environment is used; a new CRC is computed as soon as you
2751 use the "saveenv" command to store a valid environment.
2753 - CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2754 Echo the inverted Ethernet link state to the fault LED.
2756 Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2757 also needs to be defined.
2759 - CONFIG_SYS_FAULT_MII_ADDR:
2760 MII address of the PHY to check for the Ethernet link state.
2762 - CONFIG_NS16550_MIN_FUNCTIONS:
2763 Define this if you desire to only have use of the NS16550_init
2764 and NS16550_putc functions for the serial driver located at
2765 drivers/serial/ns16550.c. This option is useful for saving
2766 space for already greatly restricted images, including but not
2767 limited to NAND_SPL configurations.
2769 - CONFIG_DISPLAY_BOARDINFO
2770 Display information about the board that U-Boot is running on
2771 when U-Boot starts up. The board function checkboard() is called
2774 - CONFIG_DISPLAY_BOARDINFO_LATE
2775 Similar to the previous option, but display this information
2776 later, once stdio is running and output goes to the LCD, if
2779 - CONFIG_BOARD_SIZE_LIMIT:
2780 Maximum size of the U-Boot image. When defined, the
2781 build system checks that the actual size does not
2784 Low Level (hardware related) configuration options:
2785 ---------------------------------------------------
2787 - CONFIG_SYS_CACHELINE_SIZE:
2788 Cache Line Size of the CPU.
2790 - CONFIG_SYS_CCSRBAR_DEFAULT:
2791 Default (power-on reset) physical address of CCSR on Freescale
2794 - CONFIG_SYS_CCSRBAR:
2795 Virtual address of CCSR. On a 32-bit build, this is typically
2796 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2798 - CONFIG_SYS_CCSRBAR_PHYS:
2799 Physical address of CCSR. CCSR can be relocated to a new
2800 physical address, if desired. In this case, this macro should
2801 be set to that address. Otherwise, it should be set to the
2802 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
2803 is typically relocated on 36-bit builds. It is recommended
2804 that this macro be defined via the _HIGH and _LOW macros:
2806 #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2807 * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2809 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2810 Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
2811 either 0 (32-bit build) or 0xF (36-bit build). This macro is
2812 used in assembly code, so it must not contain typecasts or
2813 integer size suffixes (e.g. "ULL").
2815 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
2816 Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
2817 used in assembly code, so it must not contain typecasts or
2818 integer size suffixes (e.g. "ULL").
2820 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2821 If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2822 forced to a value that ensures that CCSR is not relocated.
2825 Most IDE controllers were designed to be connected with PCI
2826 interface. Only few of them were designed for AHB interface.
2827 When software is doing ATA command and data transfer to
2828 IDE devices through IDE-AHB controller, some additional
2829 registers accessing to these kind of IDE-AHB controller
2832 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
2833 DO NOT CHANGE unless you know exactly what you're
2834 doing! (11-4) [MPC8xx systems only]
2836 - CONFIG_SYS_INIT_RAM_ADDR:
2838 Start address of memory area that can be used for
2839 initial data and stack; please note that this must be
2840 writable memory that is working WITHOUT special
2841 initialization, i. e. you CANNOT use normal RAM which
2842 will become available only after programming the
2843 memory controller and running certain initialization
2846 U-Boot uses the following memory types:
2847 - MPC8xx: IMMR (internal memory of the CPU)
2849 - CONFIG_SYS_GBL_DATA_OFFSET:
2851 Offset of the initial data structure in the memory
2852 area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2853 CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2854 data is located at the end of the available space
2855 (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2856 GENERATED_GBL_DATA_SIZE), and the initial stack is just
2857 below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2858 CONFIG_SYS_GBL_DATA_OFFSET) downward.
2861 On the MPC824X (or other systems that use the data
2862 cache for initial memory) the address chosen for
2863 CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2864 point to an otherwise UNUSED address space between
2865 the top of RAM and the start of the PCI space.
2867 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
2869 - CONFIG_SYS_OR_TIMING_SDRAM:
2872 - CONFIG_SYS_MAMR_PTA:
2873 periodic timer for refresh
2875 - FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2876 CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2877 CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2878 CONFIG_SYS_BR1_PRELIM:
2879 Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2881 - SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2882 CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2883 CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2884 Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2886 - CONFIG_PCI_ENUM_ONLY
2887 Only scan through and get the devices on the buses.
2888 Don't do any setup work, presumably because someone or
2889 something has already done it, and we don't need to do it
2890 a second time. Useful for platforms that are pre-booted
2891 by coreboot or similar.
2893 - CONFIG_PCI_INDIRECT_BRIDGE:
2894 Enable support for indirect PCI bridges.
2897 Chip has SRIO or not
2900 Board has SRIO 1 port available
2903 Board has SRIO 2 port available
2905 - CONFIG_SRIO_PCIE_BOOT_MASTER
2906 Board can support master function for Boot from SRIO and PCIE
2908 - CONFIG_SYS_SRIOn_MEM_VIRT:
2909 Virtual Address of SRIO port 'n' memory region
2911 - CONFIG_SYS_SRIOn_MEM_PHYxS:
2912 Physical Address of SRIO port 'n' memory region
2914 - CONFIG_SYS_SRIOn_MEM_SIZE:
2915 Size of SRIO port 'n' memory region
2917 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
2918 Defined to tell the NAND controller that the NAND chip is using
2920 Not all NAND drivers use this symbol.
2921 Example of drivers that use it:
2922 - drivers/mtd/nand/raw/ndfc.c
2923 - drivers/mtd/nand/raw/mxc_nand.c
2925 - CONFIG_SYS_NDFC_EBC0_CFG
2926 Sets the EBC0_CFG register for the NDFC. If not defined
2927 a default value will be used.
2930 Get DDR timing information from an I2C EEPROM. Common
2931 with pluggable memory modules such as SODIMMs
2934 I2C address of the SPD EEPROM
2936 - CONFIG_SYS_SPD_BUS_NUM
2937 If SPD EEPROM is on an I2C bus other than the first
2938 one, specify here. Note that the value must resolve
2939 to something your driver can deal with.
2941 - CONFIG_SYS_DDR_RAW_TIMING
2942 Get DDR timing information from other than SPD. Common with
2943 soldered DDR chips onboard without SPD. DDR raw timing
2944 parameters are extracted from datasheet and hard-coded into
2945 header files or board specific files.
2947 - CONFIG_FSL_DDR_INTERACTIVE
2948 Enable interactive DDR debugging. See doc/README.fsl-ddr.
2950 - CONFIG_FSL_DDR_SYNC_REFRESH
2951 Enable sync of refresh for multiple controllers.
2953 - CONFIG_FSL_DDR_BIST
2954 Enable built-in memory test for Freescale DDR controllers.
2956 - CONFIG_SYS_83XX_DDR_USES_CS0
2957 Only for 83xx systems. If specified, then DDR should
2958 be configured using CS0 and CS1 instead of CS2 and CS3.
2961 Enable RMII mode for all FECs.
2962 Note that this is a global option, we can't
2963 have one FEC in standard MII mode and another in RMII mode.
2965 - CONFIG_CRC32_VERIFY
2966 Add a verify option to the crc32 command.
2969 => crc32 -v <address> <count> <crc32>
2971 Where address/count indicate a memory area
2972 and crc32 is the correct crc32 which the
2976 Add the "loopw" memory command. This only takes effect if
2977 the memory commands are activated globally (CONFIG_CMD_MEMORY).
2979 - CONFIG_CMD_MX_CYCLIC
2980 Add the "mdc" and "mwc" memory commands. These are cyclic
2985 This command will print 4 bytes (10,11,12,13) each 500 ms.
2987 => mwc.l 100 12345678 10
2988 This command will write 12345678 to address 100 all 10 ms.
2990 This only takes effect if the memory commands are activated
2991 globally (CONFIG_CMD_MEMORY).
2993 - CONFIG_SKIP_LOWLEVEL_INIT
2994 [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
2995 low level initializations (like setting up the memory
2996 controller) are omitted and/or U-Boot does not
2997 relocate itself into RAM.
2999 Normally this variable MUST NOT be defined. The only
3000 exception is when U-Boot is loaded (to RAM) by some
3001 other boot loader or by a debugger which performs
3002 these initializations itself.
3004 - CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3005 [ARM926EJ-S only] This allows just the call to lowlevel_init()
3006 to be skipped. The normal CP15 init (such as enabling the
3007 instruction cache) is still performed.
3010 Set when the currently-running compilation is for an artifact
3011 that will end up in the SPL (as opposed to the TPL or U-Boot
3012 proper). Code that needs stage-specific behavior should check
3016 Set when the currently-running compilation is for an artifact
3017 that will end up in the TPL (as opposed to the SPL or U-Boot
3018 proper). Code that needs stage-specific behavior should check
3021 - CONFIG_SYS_MPC85XX_NO_RESETVEC
3022 Only for 85xx systems. If this variable is specified, the section
3023 .resetvec is not kept and the section .bootpg is placed in the
3024 previous 4k of the .text section.
3026 - CONFIG_ARCH_MAP_SYSMEM
3027 Generally U-Boot (and in particular the md command) uses
3028 effective address. It is therefore not necessary to regard
3029 U-Boot address as virtual addresses that need to be translated
3030 to physical addresses. However, sandbox requires this, since
3031 it maintains its own little RAM buffer which contains all
3032 addressable memory. This option causes some memory accesses
3033 to be mapped through map_sysmem() / unmap_sysmem().
3035 - CONFIG_X86_RESET_VECTOR
3036 If defined, the x86 reset vector code is included. This is not
3037 needed when U-Boot is running from Coreboot.
3039 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3040 Option to disable subpage write in NAND driver
3041 driver that uses this:
3042 drivers/mtd/nand/raw/davinci_nand.c
3044 Freescale QE/FMAN Firmware Support:
3045 -----------------------------------
3047 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3048 loading of "firmware", which is encoded in the QE firmware binary format.
3049 This firmware often needs to be loaded during U-Boot booting, so macros
3050 are used to identify the storage device (NOR flash, SPI, etc) and the address
3053 - CONFIG_SYS_FMAN_FW_ADDR
3054 The address in the storage device where the FMAN microcode is located. The
3055 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3058 - CONFIG_SYS_QE_FW_ADDR
3059 The address in the storage device where the QE microcode is located. The
3060 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3063 - CONFIG_SYS_QE_FMAN_FW_LENGTH
3064 The maximum possible size of the firmware. The firmware binary format
3065 has a field that specifies the actual size of the firmware, but it
3066 might not be possible to read any part of the firmware unless some
3067 local storage is allocated to hold the entire firmware first.
3069 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
3070 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3071 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
3072 virtual address in NOR flash.
3074 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
3075 Specifies that QE/FMAN firmware is located in NAND flash.
3076 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3078 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
3079 Specifies that QE/FMAN firmware is located on the primary SD/MMC
3080 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3082 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3083 Specifies that QE/FMAN firmware is located in the remote (master)
3084 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3085 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3086 window->master inbound window->master LAW->the ucode address in
3087 master's memory space.
3089 Freescale Layerscape Management Complex Firmware Support:
3090 ---------------------------------------------------------
3091 The Freescale Layerscape Management Complex (MC) supports the loading of
3093 This firmware often needs to be loaded during U-Boot booting, so macros
3094 are used to identify the storage device (NOR flash, SPI, etc) and the address
3097 - CONFIG_FSL_MC_ENET
3098 Enable the MC driver for Layerscape SoCs.
3100 Freescale Layerscape Debug Server Support:
3101 -------------------------------------------
3102 The Freescale Layerscape Debug Server Support supports the loading of
3103 "Debug Server firmware" and triggering SP boot-rom.
3104 This firmware often needs to be loaded during U-Boot booting.
3106 - CONFIG_SYS_MC_RSV_MEM_ALIGN
3107 Define alignment of reserved memory MC requires
3112 In order to achieve reproducible builds, timestamps used in the U-Boot build
3113 process have to be set to a fixed value.
3115 This is done using the SOURCE_DATE_EPOCH environment variable.
3116 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3117 option for U-Boot or an environment variable in U-Boot.
3119 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3121 Building the Software:
3122 ======================
3124 Building U-Boot has been tested in several native build environments
3125 and in many different cross environments. Of course we cannot support
3126 all possibly existing versions of cross development tools in all
3127 (potentially obsolete) versions. In case of tool chain problems we
3128 recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3129 which is extensively used to build and test U-Boot.
3131 If you are not using a native environment, it is assumed that you
3132 have GNU cross compiling tools available in your path. In this case,
3133 you must set the environment variable CROSS_COMPILE in your shell.
3134 Note that no changes to the Makefile or any other source files are
3135 necessary. For example using the ELDK on a 4xx CPU, please enter:
3137 $ CROSS_COMPILE=ppc_4xx-
3138 $ export CROSS_COMPILE
3140 U-Boot is intended to be simple to build. After installing the
3141 sources you must configure U-Boot for one specific board type. This
3146 where "NAME_defconfig" is the name of one of the existing configu-
3147 rations; see configs/*_defconfig for supported names.
3149 Note: for some boards special configuration names may exist; check if
3150 additional information is available from the board vendor; for
3151 instance, the TQM823L systems are available without (standard)
3152 or with LCD support. You can select such additional "features"
3153 when choosing the configuration, i. e.
3155 make TQM823L_defconfig
3156 - will configure for a plain TQM823L, i. e. no LCD support
3158 make TQM823L_LCD_defconfig
3159 - will configure for a TQM823L with U-Boot console on LCD
3164 Finally, type "make all", and you should get some working U-Boot
3165 images ready for download to / installation on your system:
3167 - "u-boot.bin" is a raw binary image
3168 - "u-boot" is an image in ELF binary format
3169 - "u-boot.srec" is in Motorola S-Record format
3171 By default the build is performed locally and the objects are saved
3172 in the source directory. One of the two methods can be used to change
3173 this behavior and build U-Boot to some external directory:
3175 1. Add O= to the make command line invocations:
3177 make O=/tmp/build distclean
3178 make O=/tmp/build NAME_defconfig
3179 make O=/tmp/build all
3181 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
3183 export KBUILD_OUTPUT=/tmp/build
3188 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3191 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3192 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3193 For example to treat all compiler warnings as errors:
3195 make KCFLAGS=-Werror
3197 Please be aware that the Makefiles assume you are using GNU make, so
3198 for instance on NetBSD you might need to use "gmake" instead of
3202 If the system board that you have is not listed, then you will need
3203 to port U-Boot to your hardware platform. To do this, follow these
3206 1. Create a new directory to hold your board specific code. Add any
3207 files you need. In your board directory, you will need at least
3208 the "Makefile" and a "<board>.c".
3209 2. Create a new configuration file "include/configs/<board>.h" for
3211 3. If you're porting U-Boot to a new CPU, then also create a new
3212 directory to hold your CPU specific code. Add any files you need.
3213 4. Run "make <board>_defconfig" with your new name.
3214 5. Type "make", and you should get a working "u-boot.srec" file
3215 to be installed on your target system.
3216 6. Debug and solve any problems that might arise.
3217 [Of course, this last step is much harder than it sounds.]
3220 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3221 ==============================================================
3223 If you have modified U-Boot sources (for instance added a new board
3224 or support for new devices, a new CPU, etc.) you are expected to
3225 provide feedback to the other developers. The feedback normally takes
3226 the form of a "patch", i.e. a context diff against a certain (latest
3227 official or latest in the git repository) version of U-Boot sources.
3229 But before you submit such a patch, please verify that your modifi-
3230 cation did not break existing code. At least make sure that *ALL* of
3231 the supported boards compile WITHOUT ANY compiler warnings. To do so,
3232 just run the buildman script (tools/buildman/buildman), which will
3233 configure and build U-Boot for ALL supported system. Be warned, this
3234 will take a while. Please see the buildman README, or run 'buildman -H'
3238 See also "U-Boot Porting Guide" below.
3241 Monitor Commands - Overview:
3242 ============================
3244 go - start application at address 'addr'
3245 run - run commands in an environment variable
3246 bootm - boot application image from memory
3247 bootp - boot image via network using BootP/TFTP protocol
3248 bootz - boot zImage from memory
3249 tftpboot- boot image via network using TFTP protocol
3250 and env variables "ipaddr" and "serverip"
3251 (and eventually "gatewayip")
3252 tftpput - upload a file via network using TFTP protocol
3253 rarpboot- boot image via network using RARP/TFTP protocol
3254 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
3255 loads - load S-Record file over serial line
3256 loadb - load binary file over serial line (kermit mode)
3258 mm - memory modify (auto-incrementing)
3259 nm - memory modify (constant address)
3260 mw - memory write (fill)
3262 cmp - memory compare
3263 crc32 - checksum calculation
3264 i2c - I2C sub-system
3265 sspi - SPI utility commands
3266 base - print or set address offset
3267 printenv- print environment variables
3268 setenv - set environment variables
3269 saveenv - save environment variables to persistent storage
3270 protect - enable or disable FLASH write protection
3271 erase - erase FLASH memory
3272 flinfo - print FLASH memory information
3273 nand - NAND memory operations (see doc/README.nand)
3274 bdinfo - print Board Info structure
3275 iminfo - print header information for application image
3276 coninfo - print console devices and informations
3277 ide - IDE sub-system
3278 loop - infinite loop on address range
3279 loopw - infinite write loop on address range
3280 mtest - simple RAM test
3281 icache - enable or disable instruction cache
3282 dcache - enable or disable data cache
3283 reset - Perform RESET of the CPU
3284 echo - echo args to console
3285 version - print monitor version
3286 help - print online help
3287 ? - alias for 'help'
3290 Monitor Commands - Detailed Description:
3291 ========================================
3295 For now: just type "help <command>".
3298 Environment Variables:
3299 ======================
3301 U-Boot supports user configuration using Environment Variables which
3302 can be made persistent by saving to Flash memory.
3304 Environment Variables are set using "setenv", printed using
3305 "printenv", and saved to Flash using "saveenv". Using "setenv"
3306 without a value can be used to delete a variable from the
3307 environment. As long as you don't save the environment you are
3308 working with an in-memory copy. In case the Flash area containing the
3309 environment is erased by accident, a default environment is provided.
3311 Some configuration options can be set using Environment Variables.
3313 List of environment variables (most likely not complete):
3315 baudrate - see CONFIG_BAUDRATE
3317 bootdelay - see CONFIG_BOOTDELAY
3319 bootcmd - see CONFIG_BOOTCOMMAND
3321 bootargs - Boot arguments when booting an RTOS image
3323 bootfile - Name of the image to load with TFTP
3325 bootm_low - Memory range available for image processing in the bootm
3326 command can be restricted. This variable is given as
3327 a hexadecimal number and defines lowest address allowed
3328 for use by the bootm command. See also "bootm_size"
3329 environment variable. Address defined by "bootm_low" is
3330 also the base of the initial memory mapping for the Linux
3331 kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3334 bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3335 This variable is given as a hexadecimal number and it
3336 defines the size of the memory region starting at base
3337 address bootm_low that is accessible by the Linux kernel
3338 during early boot. If unset, CONFIG_SYS_BOOTMAPSZ is used
3339 as the default value if it is defined, and bootm_size is
3342 bootm_size - Memory range available for image processing in the bootm
3343 command can be restricted. This variable is given as
3344 a hexadecimal number and defines the size of the region
3345 allowed for use by the bootm command. See also "bootm_low"
3346 environment variable.
3348 bootstopkeysha256, bootdelaykey, bootstopkey - See README.autoboot
3350 updatefile - Location of the software update file on a TFTP server, used
3351 by the automatic software update feature. Please refer to
3352 documentation in doc/README.update for more details.
3354 autoload - if set to "no" (any string beginning with 'n'),
3355 "bootp" will just load perform a lookup of the
3356 configuration from the BOOTP server, but not try to
3357 load any image using TFTP
3359 autostart - if set to "yes", an image loaded using the "bootp",
3360 "rarpboot", "tftpboot" or "diskboot" commands will
3361 be automatically started (by internally calling
3364 If set to "no", a standalone image passed to the
3365 "bootm" command will be copied to the load address
3366 (and eventually uncompressed), but NOT be started.
3367 This can be used to load and uncompress arbitrary
3370 fdt_high - if set this restricts the maximum address that the
3371 flattened device tree will be copied into upon boot.
3372 For example, if you have a system with 1 GB memory
3373 at physical address 0x10000000, while Linux kernel
3374 only recognizes the first 704 MB as low memory, you
3375 may need to set fdt_high as 0x3C000000 to have the
3376 device tree blob be copied to the maximum address
3377 of the 704 MB low memory, so that Linux kernel can
3378 access it during the boot procedure.
3380 If this is set to the special value 0xFFFFFFFF then
3381 the fdt will not be copied at all on boot. For this
3382 to work it must reside in writable memory, have
3383 sufficient padding on the end of it for u-boot to
3384 add the information it needs into it, and the memory
3385 must be accessible by the kernel.
3387 fdtcontroladdr- if set this is the address of the control flattened
3388 device tree used by U-Boot when CONFIG_OF_CONTROL is
3391 i2cfast - (PPC405GP|PPC405EP only)
3392 if set to 'y' configures Linux I2C driver for fast
3393 mode (400kHZ). This environment variable is used in
3394 initialization code. So, for changes to be effective
3395 it must be saved and board must be reset.
3397 initrd_high - restrict positioning of initrd images:
3398 If this variable is not set, initrd images will be
3399 copied to the highest possible address in RAM; this
3400 is usually what you want since it allows for
3401 maximum initrd size. If for some reason you want to
3402 make sure that the initrd image is loaded below the
3403 CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3404 variable to a value of "no" or "off" or "0".
3405 Alternatively, you can set it to a maximum upper
3406 address to use (U-Boot will still check that it
3407 does not overwrite the U-Boot stack and data).
3409 For instance, when you have a system with 16 MB
3410 RAM, and want to reserve 4 MB from use by Linux,
3411 you can do this by adding "mem=12M" to the value of
3412 the "bootargs" variable. However, now you must make
3413 sure that the initrd image is placed in the first
3414 12 MB as well - this can be done with
3416 setenv initrd_high 00c00000
3418 If you set initrd_high to 0xFFFFFFFF, this is an
3419 indication to U-Boot that all addresses are legal
3420 for the Linux kernel, including addresses in flash
3421 memory. In this case U-Boot will NOT COPY the
3422 ramdisk at all. This may be useful to reduce the
3423 boot time on your system, but requires that this
3424 feature is supported by your Linux kernel.
3426 ipaddr - IP address; needed for tftpboot command
3428 loadaddr - Default load address for commands like "bootp",
3429 "rarpboot", "tftpboot", "loadb" or "diskboot"
3431 loads_echo - see CONFIG_LOADS_ECHO
3433 serverip - TFTP server IP address; needed for tftpboot command
3435 bootretry - see CONFIG_BOOT_RETRY_TIME
3437 bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR
3439 bootstopkey - see CONFIG_AUTOBOOT_STOP_STR
3441 ethprime - controls which interface is used first.
3443 ethact - controls which interface is currently active.
3444 For example you can do the following
3446 => setenv ethact FEC
3447 => ping 192.168.0.1 # traffic sent on FEC
3448 => setenv ethact SCC
3449 => ping 10.0.0.1 # traffic sent on SCC
3451 ethrotate - When set to "no" U-Boot does not go through all
3452 available network interfaces.
3453 It just stays at the currently selected interface.
3455 netretry - When set to "no" each network operation will
3456 either succeed or fail without retrying.
3457 When set to "once" the network operation will
3458 fail when all the available network interfaces
3459 are tried once without success.
3460 Useful on scripts which control the retry operation
3463 npe_ucode - set load address for the NPE microcode
3465 silent_linux - If set then Linux will be told to boot silently, by
3466 changing the console to be empty. If "yes" it will be
3467 made silent. If "no" it will not be made silent. If
3468 unset, then it will be made silent if the U-Boot console
3471 tftpsrcp - If this is set, the value is used for TFTP's
3474 tftpdstp - If this is set, the value is used for TFTP's UDP
3475 destination port instead of the Well Know Port 69.
3477 tftpblocksize - Block size to use for TFTP transfers; if not set,
3478 we use the TFTP server's default block size
3480 tftptimeout - Retransmission timeout for TFTP packets (in milli-
3481 seconds, minimum value is 1000 = 1 second). Defines
3482 when a packet is considered to be lost so it has to
3483 be retransmitted. The default is 5000 = 5 seconds.
3484 Lowering this value may make downloads succeed
3485 faster in networks with high packet loss rates or
3486 with unreliable TFTP servers.
3488 tftptimeoutcountmax - maximum count of TFTP timeouts (no
3489 unit, minimum value = 0). Defines how many timeouts
3490 can happen during a single file transfer before that
3491 transfer is aborted. The default is 10, and 0 means
3492 'no timeouts allowed'. Increasing this value may help
3493 downloads succeed with high packet loss rates, or with
3494 unreliable TFTP servers or client hardware.
3496 vlan - When set to a value < 4095 the traffic over
3497 Ethernet is encapsulated/received over 802.1q
3500 bootpretryperiod - Period during which BOOTP/DHCP sends retries.
3501 Unsigned value, in milliseconds. If not set, the period will
3502 be either the default (28000), or a value based on
3503 CONFIG_NET_RETRY_COUNT, if defined. This value has
3504 precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3506 The following image location variables contain the location of images
3507 used in booting. The "Image" column gives the role of the image and is
3508 not an environment variable name. The other columns are environment
3509 variable names. "File Name" gives the name of the file on a TFTP
3510 server, "RAM Address" gives the location in RAM the image will be
3511 loaded to, and "Flash Location" gives the image's address in NOR
3512 flash or offset in NAND flash.
3514 *Note* - these variables don't have to be defined for all boards, some
3515 boards currently use other variables for these purposes, and some
3516 boards use these variables for other purposes.
3518 Image File Name RAM Address Flash Location
3519 ----- --------- ----------- --------------
3520 u-boot u-boot u-boot_addr_r u-boot_addr
3521 Linux kernel bootfile kernel_addr_r kernel_addr
3522 device tree blob fdtfile fdt_addr_r fdt_addr
3523 ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr
3525 The following environment variables may be used and automatically
3526 updated by the network boot commands ("bootp" and "rarpboot"),
3527 depending the information provided by your boot server:
3529 bootfile - see above
3530 dnsip - IP address of your Domain Name Server
3531 dnsip2 - IP address of your secondary Domain Name Server
3532 gatewayip - IP address of the Gateway (Router) to use
3533 hostname - Target hostname
3535 netmask - Subnet Mask
3536 rootpath - Pathname of the root filesystem on the NFS server
3537 serverip - see above
3540 There are two special Environment Variables:
3542 serial# - contains hardware identification information such
3543 as type string and/or serial number
3544 ethaddr - Ethernet address
3546 These variables can be set only once (usually during manufacturing of
3547 the board). U-Boot refuses to delete or overwrite these variables
3548 once they have been set once.
3551 Further special Environment Variables:
3553 ver - Contains the U-Boot version string as printed
3554 with the "version" command. This variable is
3555 readonly (see CONFIG_VERSION_VARIABLE).
3558 Please note that changes to some configuration parameters may take
3559 only effect after the next boot (yes, that's just like Windoze :-).
3562 Callback functions for environment variables:
3563 ---------------------------------------------
3565 For some environment variables, the behavior of u-boot needs to change
3566 when their values are changed. This functionality allows functions to
3567 be associated with arbitrary variables. On creation, overwrite, or
3568 deletion, the callback will provide the opportunity for some side
3569 effect to happen or for the change to be rejected.
3571 The callbacks are named and associated with a function using the
3572 U_BOOT_ENV_CALLBACK macro in your board or driver code.
3574 These callbacks are associated with variables in one of two ways. The
3575 static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3576 in the board configuration to a string that defines a list of
3577 associations. The list must be in the following format:
3579 entry = variable_name[:callback_name]
3582 If the callback name is not specified, then the callback is deleted.
3583 Spaces are also allowed anywhere in the list.
3585 Callbacks can also be associated by defining the ".callbacks" variable
3586 with the same list format above. Any association in ".callbacks" will
3587 override any association in the static list. You can define
3588 CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3589 ".callbacks" environment variable in the default or embedded environment.
3591 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3592 regular expression. This allows multiple variables to be connected to
3593 the same callback without explicitly listing them all out.
3595 The signature of the callback functions is:
3597 int callback(const char *name, const char *value, enum env_op op, int flags)
3599 * name - changed environment variable
3600 * value - new value of the environment variable
3601 * op - operation (create, overwrite, or delete)
3602 * flags - attributes of the environment variable change, see flags H_* in
3605 The return value is 0 if the variable change is accepted and 1 otherwise.
3607 Command Line Parsing:
3608 =====================
3610 There are two different command line parsers available with U-Boot:
3611 the old "simple" one, and the much more powerful "hush" shell:
3613 Old, simple command line parser:
3614 --------------------------------
3616 - supports environment variables (through setenv / saveenv commands)
3617 - several commands on one line, separated by ';'
3618 - variable substitution using "... ${name} ..." syntax
3619 - special characters ('$', ';') can be escaped by prefixing with '\',
3621 setenv bootcmd bootm \${address}
3622 - You can also escape text by enclosing in single apostrophes, for example:
3623 setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3628 - similar to Bourne shell, with control structures like
3629 if...then...else...fi, for...do...done; while...do...done,
3630 until...do...done, ...
3631 - supports environment ("global") variables (through setenv / saveenv
3632 commands) and local shell variables (through standard shell syntax
3633 "name=value"); only environment variables can be used with "run"
3639 (1) If a command line (or an environment variable executed by a "run"
3640 command) contains several commands separated by semicolon, and
3641 one of these commands fails, then the remaining commands will be
3644 (2) If you execute several variables with one call to run (i. e.
3645 calling run with a list of variables as arguments), any failing
3646 command will cause "run" to terminate, i. e. the remaining
3647 variables are not executed.
3649 Note for Redundant Ethernet Interfaces:
3650 =======================================
3652 Some boards come with redundant Ethernet interfaces; U-Boot supports
3653 such configurations and is capable of automatic selection of a
3654 "working" interface when needed. MAC assignment works as follows:
3656 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3657 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3658 "eth1addr" (=>eth1), "eth2addr", ...
3660 If the network interface stores some valid MAC address (for instance
3661 in SROM), this is used as default address if there is NO correspon-
3662 ding setting in the environment; if the corresponding environment
3663 variable is set, this overrides the settings in the card; that means:
3665 o If the SROM has a valid MAC address, and there is no address in the
3666 environment, the SROM's address is used.
3668 o If there is no valid address in the SROM, and a definition in the
3669 environment exists, then the value from the environment variable is
3672 o If both the SROM and the environment contain a MAC address, and
3673 both addresses are the same, this MAC address is used.
3675 o If both the SROM and the environment contain a MAC address, and the
3676 addresses differ, the value from the environment is used and a
3679 o If neither SROM nor the environment contain a MAC address, an error
3680 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3681 a random, locally-assigned MAC is used.
3683 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3684 will be programmed into hardware as part of the initialization process. This
3685 may be skipped by setting the appropriate 'ethmacskip' environment variable.
3686 The naming convention is as follows:
3687 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3692 U-Boot is capable of booting (and performing other auxiliary operations on)
3693 images in two formats:
3695 New uImage format (FIT)
3696 -----------------------
3698 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3699 to Flattened Device Tree). It allows the use of images with multiple
3700 components (several kernels, ramdisks, etc.), with contents protected by
3701 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3707 Old image format is based on binary files which can be basically anything,
3708 preceded by a special header; see the definitions in include/image.h for
3709 details; basically, the header defines the following image properties:
3711 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3712 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3713 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3714 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3716 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3717 IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3718 Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3719 * Compression Type (uncompressed, gzip, bzip2)
3725 The header is marked by a special Magic Number, and both the header
3726 and the data portions of the image are secured against corruption by
3733 Although U-Boot should support any OS or standalone application
3734 easily, the main focus has always been on Linux during the design of
3737 U-Boot includes many features that so far have been part of some
3738 special "boot loader" code within the Linux kernel. Also, any
3739 "initrd" images to be used are no longer part of one big Linux image;
3740 instead, kernel and "initrd" are separate images. This implementation
3741 serves several purposes:
3743 - the same features can be used for other OS or standalone
3744 applications (for instance: using compressed images to reduce the
3745 Flash memory footprint)
3747 - it becomes much easier to port new Linux kernel versions because
3748 lots of low-level, hardware dependent stuff are done by U-Boot
3750 - the same Linux kernel image can now be used with different "initrd"
3751 images; of course this also means that different kernel images can
3752 be run with the same "initrd". This makes testing easier (you don't
3753 have to build a new "zImage.initrd" Linux image when you just
3754 change a file in your "initrd"). Also, a field-upgrade of the
3755 software is easier now.
3761 Porting Linux to U-Boot based systems:
3762 ---------------------------------------
3764 U-Boot cannot save you from doing all the necessary modifications to
3765 configure the Linux device drivers for use with your target hardware
3766 (no, we don't intend to provide a full virtual machine interface to
3769 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3771 Just make sure your machine specific header file (for instance
3772 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3773 Information structure as we define in include/asm-<arch>/u-boot.h,
3774 and make sure that your definition of IMAP_ADDR uses the same value
3775 as your U-Boot configuration in CONFIG_SYS_IMMR.
3777 Note that U-Boot now has a driver model, a unified model for drivers.
3778 If you are adding a new driver, plumb it into driver model. If there
3779 is no uclass available, you are encouraged to create one. See
3783 Configuring the Linux kernel:
3784 -----------------------------
3786 No specific requirements for U-Boot. Make sure you have some root
3787 device (initial ramdisk, NFS) for your target system.
3790 Building a Linux Image:
3791 -----------------------
3793 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3794 not used. If you use recent kernel source, a new build target
3795 "uImage" will exist which automatically builds an image usable by
3796 U-Boot. Most older kernels also have support for a "pImage" target,
3797 which was introduced for our predecessor project PPCBoot and uses a
3798 100% compatible format.
3802 make TQM850L_defconfig
3807 The "uImage" build target uses a special tool (in 'tools/mkimage') to
3808 encapsulate a compressed Linux kernel image with header information,
3809 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3811 * build a standard "vmlinux" kernel image (in ELF binary format):
3813 * convert the kernel into a raw binary image:
3815 ${CROSS_COMPILE}-objcopy -O binary \
3816 -R .note -R .comment \
3817 -S vmlinux linux.bin
3819 * compress the binary image:
3823 * package compressed binary image for U-Boot:
3825 mkimage -A ppc -O linux -T kernel -C gzip \
3826 -a 0 -e 0 -n "Linux Kernel Image" \
3827 -d linux.bin.gz uImage
3830 The "mkimage" tool can also be used to create ramdisk images for use
3831 with U-Boot, either separated from the Linux kernel image, or
3832 combined into one file. "mkimage" encapsulates the images with a 64
3833 byte header containing information about target architecture,
3834 operating system, image type, compression method, entry points, time
3835 stamp, CRC32 checksums, etc.
3837 "mkimage" can be called in two ways: to verify existing images and
3838 print the header information, or to build new images.
3840 In the first form (with "-l" option) mkimage lists the information
3841 contained in the header of an existing U-Boot image; this includes
3842 checksum verification:
3844 tools/mkimage -l image
3845 -l ==> list image header information
3847 The second form (with "-d" option) is used to build a U-Boot image
3848 from a "data file" which is used as image payload:
3850 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3851 -n name -d data_file image
3852 -A ==> set architecture to 'arch'
3853 -O ==> set operating system to 'os'
3854 -T ==> set image type to 'type'
3855 -C ==> set compression type 'comp'
3856 -a ==> set load address to 'addr' (hex)
3857 -e ==> set entry point to 'ep' (hex)
3858 -n ==> set image name to 'name'
3859 -d ==> use image data from 'datafile'
3861 Right now, all Linux kernels for PowerPC systems use the same load
3862 address (0x00000000), but the entry point address depends on the
3865 - 2.2.x kernels have the entry point at 0x0000000C,
3866 - 2.3.x and later kernels have the entry point at 0x00000000.
3868 So a typical call to build a U-Boot image would read:
3870 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3871 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3872 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3873 > examples/uImage.TQM850L
3874 Image Name: 2.4.4 kernel for TQM850L
3875 Created: Wed Jul 19 02:34:59 2000
3876 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3877 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3878 Load Address: 0x00000000
3879 Entry Point: 0x00000000
3881 To verify the contents of the image (or check for corruption):
3883 -> tools/mkimage -l examples/uImage.TQM850L
3884 Image Name: 2.4.4 kernel for TQM850L
3885 Created: Wed Jul 19 02:34:59 2000
3886 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3887 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3888 Load Address: 0x00000000
3889 Entry Point: 0x00000000
3891 NOTE: for embedded systems where boot time is critical you can trade
3892 speed for memory and install an UNCOMPRESSED image instead: this
3893 needs more space in Flash, but boots much faster since it does not
3894 need to be uncompressed:
3896 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3897 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3898 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3899 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3900 > examples/uImage.TQM850L-uncompressed
3901 Image Name: 2.4.4 kernel for TQM850L
3902 Created: Wed Jul 19 02:34:59 2000
3903 Image Type: PowerPC Linux Kernel Image (uncompressed)
3904 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
3905 Load Address: 0x00000000
3906 Entry Point: 0x00000000
3909 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3910 when your kernel is intended to use an initial ramdisk:
3912 -> tools/mkimage -n 'Simple Ramdisk Image' \
3913 > -A ppc -O linux -T ramdisk -C gzip \
3914 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3915 Image Name: Simple Ramdisk Image
3916 Created: Wed Jan 12 14:01:50 2000
3917 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3918 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
3919 Load Address: 0x00000000
3920 Entry Point: 0x00000000
3922 The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
3923 option performs the converse operation of the mkimage's second form (the "-d"
3924 option). Given an image built by mkimage, the dumpimage extracts a "data file"
3927 tools/dumpimage -i image -T type -p position data_file
3928 -i ==> extract from the 'image' a specific 'data_file'
3929 -T ==> set image type to 'type'
3930 -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
3933 Installing a Linux Image:
3934 -------------------------
3936 To downloading a U-Boot image over the serial (console) interface,
3937 you must convert the image to S-Record format:
3939 objcopy -I binary -O srec examples/image examples/image.srec
3941 The 'objcopy' does not understand the information in the U-Boot
3942 image header, so the resulting S-Record file will be relative to
3943 address 0x00000000. To load it to a given address, you need to
3944 specify the target address as 'offset' parameter with the 'loads'
3947 Example: install the image to address 0x40100000 (which on the
3948 TQM8xxL is in the first Flash bank):
3950 => erase 40100000 401FFFFF
3956 ## Ready for S-Record download ...
3957 ~>examples/image.srec
3958 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3960 15989 15990 15991 15992
3961 [file transfer complete]
3963 ## Start Addr = 0x00000000
3966 You can check the success of the download using the 'iminfo' command;
3967 this includes a checksum verification so you can be sure no data
3968 corruption happened:
3972 ## Checking Image at 40100000 ...
3973 Image Name: 2.2.13 for initrd on TQM850L
3974 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3975 Data Size: 335725 Bytes = 327 kB = 0 MB
3976 Load Address: 00000000
3977 Entry Point: 0000000c
3978 Verifying Checksum ... OK
3984 The "bootm" command is used to boot an application that is stored in
3985 memory (RAM or Flash). In case of a Linux kernel image, the contents
3986 of the "bootargs" environment variable is passed to the kernel as
3987 parameters. You can check and modify this variable using the
3988 "printenv" and "setenv" commands:
3991 => printenv bootargs
3992 bootargs=root=/dev/ram
3994 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3996 => printenv bootargs
3997 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4000 ## Booting Linux kernel at 40020000 ...
4001 Image Name: 2.2.13 for NFS on TQM850L
4002 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4003 Data Size: 381681 Bytes = 372 kB = 0 MB
4004 Load Address: 00000000
4005 Entry Point: 0000000c
4006 Verifying Checksum ... OK
4007 Uncompressing Kernel Image ... OK
4008 Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
4009 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4010 time_init: decrementer frequency = 187500000/60
4011 Calibrating delay loop... 49.77 BogoMIPS
4012 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4015 If you want to boot a Linux kernel with initial RAM disk, you pass
4016 the memory addresses of both the kernel and the initrd image (PPBCOOT
4017 format!) to the "bootm" command:
4019 => imi 40100000 40200000
4021 ## Checking Image at 40100000 ...
4022 Image Name: 2.2.13 for initrd on TQM850L
4023 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4024 Data Size: 335725 Bytes = 327 kB = 0 MB
4025 Load Address: 00000000
4026 Entry Point: 0000000c
4027 Verifying Checksum ... OK
4029 ## Checking Image at 40200000 ...
4030 Image Name: Simple Ramdisk Image
4031 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
4032 Data Size: 566530 Bytes = 553 kB = 0 MB
4033 Load Address: 00000000
4034 Entry Point: 00000000
4035 Verifying Checksum ... OK
4037 => bootm 40100000 40200000
4038 ## Booting Linux kernel at 40100000 ...
4039 Image Name: 2.2.13 for initrd on TQM850L
4040 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4041 Data Size: 335725 Bytes = 327 kB = 0 MB
4042 Load Address: 00000000
4043 Entry Point: 0000000c
4044 Verifying Checksum ... OK
4045 Uncompressing Kernel Image ... OK
4046 ## Loading RAMDisk Image at 40200000 ...
4047 Image Name: Simple Ramdisk Image
4048 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
4049 Data Size: 566530 Bytes = 553 kB = 0 MB
4050 Load Address: 00000000
4051 Entry Point: 00000000
4052 Verifying Checksum ... OK
4053 Loading Ramdisk ... OK
4054 Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
4055 Boot arguments: root=/dev/ram
4056 time_init: decrementer frequency = 187500000/60
4057 Calibrating delay loop... 49.77 BogoMIPS
4059 RAMDISK: Compressed image found at block 0
4060 VFS: Mounted root (ext2 filesystem).
4064 Boot Linux and pass a flat device tree:
4067 First, U-Boot must be compiled with the appropriate defines. See the section
4068 titled "Linux Kernel Interface" above for a more in depth explanation. The
4069 following is an example of how to start a kernel and pass an updated
4075 oft=oftrees/mpc8540ads.dtb
4076 => tftp $oftaddr $oft
4077 Speed: 1000, full duplex
4079 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4080 Filename 'oftrees/mpc8540ads.dtb'.
4081 Load address: 0x300000
4084 Bytes transferred = 4106 (100a hex)
4085 => tftp $loadaddr $bootfile
4086 Speed: 1000, full duplex
4088 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4090 Load address: 0x200000
4091 Loading:############
4093 Bytes transferred = 1029407 (fb51f hex)
4098 => bootm $loadaddr - $oftaddr
4099 ## Booting image at 00200000 ...
4100 Image Name: Linux-2.6.17-dirty
4101 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4102 Data Size: 1029343 Bytes = 1005.2 kB
4103 Load Address: 00000000
4104 Entry Point: 00000000
4105 Verifying Checksum ... OK
4106 Uncompressing Kernel Image ... OK
4107 Booting using flat device tree at 0x300000
4108 Using MPC85xx ADS machine description
4109 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4113 More About U-Boot Image Types:
4114 ------------------------------
4116 U-Boot supports the following image types:
4118 "Standalone Programs" are directly runnable in the environment
4119 provided by U-Boot; it is expected that (if they behave
4120 well) you can continue to work in U-Boot after return from
4121 the Standalone Program.
4122 "OS Kernel Images" are usually images of some Embedded OS which
4123 will take over control completely. Usually these programs
4124 will install their own set of exception handlers, device
4125 drivers, set up the MMU, etc. - this means, that you cannot
4126 expect to re-enter U-Boot except by resetting the CPU.
4127 "RAMDisk Images" are more or less just data blocks, and their
4128 parameters (address, size) are passed to an OS kernel that is
4130 "Multi-File Images" contain several images, typically an OS
4131 (Linux) kernel image and one or more data images like
4132 RAMDisks. This construct is useful for instance when you want
4133 to boot over the network using BOOTP etc., where the boot
4134 server provides just a single image file, but you want to get
4135 for instance an OS kernel and a RAMDisk image.
4137 "Multi-File Images" start with a list of image sizes, each
4138 image size (in bytes) specified by an "uint32_t" in network
4139 byte order. This list is terminated by an "(uint32_t)0".
4140 Immediately after the terminating 0 follow the images, one by
4141 one, all aligned on "uint32_t" boundaries (size rounded up to
4142 a multiple of 4 bytes).
4144 "Firmware Images" are binary images containing firmware (like
4145 U-Boot or FPGA images) which usually will be programmed to
4148 "Script files" are command sequences that will be executed by
4149 U-Boot's command interpreter; this feature is especially
4150 useful when you configure U-Boot to use a real shell (hush)
4151 as command interpreter.
4153 Booting the Linux zImage:
4154 -------------------------
4156 On some platforms, it's possible to boot Linux zImage. This is done
4157 using the "bootz" command. The syntax of "bootz" command is the same
4158 as the syntax of "bootm" command.
4160 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4161 kernel with raw initrd images. The syntax is slightly different, the
4162 address of the initrd must be augmented by it's size, in the following
4163 format: "<initrd addres>:<initrd size>".
4169 One of the features of U-Boot is that you can dynamically load and
4170 run "standalone" applications, which can use some resources of
4171 U-Boot like console I/O functions or interrupt services.
4173 Two simple examples are included with the sources:
4178 'examples/hello_world.c' contains a small "Hello World" Demo
4179 application; it is automatically compiled when you build U-Boot.
4180 It's configured to run at address 0x00040004, so you can play with it
4184 ## Ready for S-Record download ...
4185 ~>examples/hello_world.srec
4186 1 2 3 4 5 6 7 8 9 10 11 ...
4187 [file transfer complete]
4189 ## Start Addr = 0x00040004
4191 => go 40004 Hello World! This is a test.
4192 ## Starting application at 0x00040004 ...
4203 Hit any key to exit ...
4205 ## Application terminated, rc = 0x0
4207 Another example, which demonstrates how to register a CPM interrupt
4208 handler with the U-Boot code, can be found in 'examples/timer.c'.
4209 Here, a CPM timer is set up to generate an interrupt every second.
4210 The interrupt service routine is trivial, just printing a '.'
4211 character, but this is just a demo program. The application can be
4212 controlled by the following keys:
4214 ? - print current values og the CPM Timer registers
4215 b - enable interrupts and start timer
4216 e - stop timer and disable interrupts
4217 q - quit application
4220 ## Ready for S-Record download ...
4221 ~>examples/timer.srec
4222 1 2 3 4 5 6 7 8 9 10 11 ...
4223 [file transfer complete]
4225 ## Start Addr = 0x00040004
4228 ## Starting application at 0x00040004 ...
4231 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4234 [q, b, e, ?] Set interval 1000000 us
4237 [q, b, e, ?] ........
4238 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4241 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4244 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4247 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4249 [q, b, e, ?] ...Stopping timer
4251 [q, b, e, ?] ## Application terminated, rc = 0x0
4257 Over time, many people have reported problems when trying to use the
4258 "minicom" terminal emulation program for serial download. I (wd)
4259 consider minicom to be broken, and recommend not to use it. Under
4260 Unix, I recommend to use C-Kermit for general purpose use (and
4261 especially for kermit binary protocol download ("loadb" command), and
4262 use "cu" for S-Record download ("loads" command). See
4263 http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4264 for help with kermit.
4267 Nevertheless, if you absolutely want to use it try adding this
4268 configuration to your "File transfer protocols" section:
4270 Name Program Name U/D FullScr IO-Red. Multi
4271 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
4272 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
4278 Starting at version 0.9.2, U-Boot supports NetBSD both as host
4279 (build U-Boot) and target system (boots NetBSD/mpc8xx).
4281 Building requires a cross environment; it is known to work on
4282 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4283 need gmake since the Makefiles are not compatible with BSD make).
4284 Note that the cross-powerpc package does not install include files;
4285 attempting to build U-Boot will fail because <machine/ansi.h> is
4286 missing. This file has to be installed and patched manually:
4288 # cd /usr/pkg/cross/powerpc-netbsd/include
4290 # ln -s powerpc machine
4291 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4292 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
4294 Native builds *don't* work due to incompatibilities between native
4295 and U-Boot include files.
4297 Booting assumes that (the first part of) the image booted is a
4298 stage-2 loader which in turn loads and then invokes the kernel
4299 proper. Loader sources will eventually appear in the NetBSD source
4300 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4301 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4304 Implementation Internals:
4305 =========================
4307 The following is not intended to be a complete description of every
4308 implementation detail. However, it should help to understand the
4309 inner workings of U-Boot and make it easier to port it to custom
4313 Initial Stack, Global Data:
4314 ---------------------------
4316 The implementation of U-Boot is complicated by the fact that U-Boot
4317 starts running out of ROM (flash memory), usually without access to
4318 system RAM (because the memory controller is not initialized yet).
4319 This means that we don't have writable Data or BSS segments, and BSS
4320 is not initialized as zero. To be able to get a C environment working
4321 at all, we have to allocate at least a minimal stack. Implementation
4322 options for this are defined and restricted by the CPU used: Some CPU
4323 models provide on-chip memory (like the IMMR area on MPC8xx and
4324 MPC826x processors), on others (parts of) the data cache can be
4325 locked as (mis-) used as memory, etc.
4327 Chris Hallinan posted a good summary of these issues to the
4328 U-Boot mailing list:
4330 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4331 From: "Chris Hallinan" <clh@net1plus.com>
4332 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4335 Correct me if I'm wrong, folks, but the way I understand it
4336 is this: Using DCACHE as initial RAM for Stack, etc, does not
4337 require any physical RAM backing up the cache. The cleverness
4338 is that the cache is being used as a temporary supply of
4339 necessary storage before the SDRAM controller is setup. It's
4340 beyond the scope of this list to explain the details, but you
4341 can see how this works by studying the cache architecture and
4342 operation in the architecture and processor-specific manuals.
4344 OCM is On Chip Memory, which I believe the 405GP has 4K. It
4345 is another option for the system designer to use as an
4346 initial stack/RAM area prior to SDRAM being available. Either
4347 option should work for you. Using CS 4 should be fine if your
4348 board designers haven't used it for something that would
4349 cause you grief during the initial boot! It is frequently not
4352 CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4353 with your processor/board/system design. The default value
4354 you will find in any recent u-boot distribution in
4355 walnut.h should work for you. I'd set it to a value larger
4356 than your SDRAM module. If you have a 64MB SDRAM module, set
4357 it above 400_0000. Just make sure your board has no resources
4358 that are supposed to respond to that address! That code in
4359 start.S has been around a while and should work as is when
4360 you get the config right.
4365 It is essential to remember this, since it has some impact on the C
4366 code for the initialization procedures:
4368 * Initialized global data (data segment) is read-only. Do not attempt
4371 * Do not use any uninitialized global data (or implicitly initialized
4372 as zero data - BSS segment) at all - this is undefined, initiali-
4373 zation is performed later (when relocating to RAM).
4375 * Stack space is very limited. Avoid big data buffers or things like
4378 Having only the stack as writable memory limits means we cannot use
4379 normal global data to share information between the code. But it
4380 turned out that the implementation of U-Boot can be greatly
4381 simplified by making a global data structure (gd_t) available to all
4382 functions. We could pass a pointer to this data as argument to _all_
4383 functions, but this would bloat the code. Instead we use a feature of
4384 the GCC compiler (Global Register Variables) to share the data: we
4385 place a pointer (gd) to the global data into a register which we
4386 reserve for this purpose.
4388 When choosing a register for such a purpose we are restricted by the
4389 relevant (E)ABI specifications for the current architecture, and by
4390 GCC's implementation.
4392 For PowerPC, the following registers have specific use:
4394 R2: reserved for system use
4395 R3-R4: parameter passing and return values
4396 R5-R10: parameter passing
4397 R13: small data area pointer
4401 (U-Boot also uses R12 as internal GOT pointer. r12
4402 is a volatile register so r12 needs to be reset when
4403 going back and forth between asm and C)
4405 ==> U-Boot will use R2 to hold a pointer to the global data
4407 Note: on PPC, we could use a static initializer (since the
4408 address of the global data structure is known at compile time),
4409 but it turned out that reserving a register results in somewhat
4410 smaller code - although the code savings are not that big (on
4411 average for all boards 752 bytes for the whole U-Boot image,
4412 624 text + 127 data).
4414 On ARM, the following registers are used:
4416 R0: function argument word/integer result
4417 R1-R3: function argument word
4418 R9: platform specific
4419 R10: stack limit (used only if stack checking is enabled)
4420 R11: argument (frame) pointer
4421 R12: temporary workspace
4424 R15: program counter
4426 ==> U-Boot will use R9 to hold a pointer to the global data
4428 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4430 On Nios II, the ABI is documented here:
4431 http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4433 ==> U-Boot will use gp to hold a pointer to the global data
4435 Note: on Nios II, we give "-G0" option to gcc and don't use gp
4436 to access small data sections, so gp is free.
4438 On NDS32, the following registers are used:
4440 R0-R1: argument/return
4442 R15: temporary register for assembler
4443 R16: trampoline register
4444 R28: frame pointer (FP)
4445 R29: global pointer (GP)
4446 R30: link register (LP)
4447 R31: stack pointer (SP)
4448 PC: program counter (PC)
4450 ==> U-Boot will use R10 to hold a pointer to the global data
4452 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4453 or current versions of GCC may "optimize" the code too much.
4455 On RISC-V, the following registers are used:
4457 x0: hard-wired zero (zero)
4458 x1: return address (ra)
4459 x2: stack pointer (sp)
4460 x3: global pointer (gp)
4461 x4: thread pointer (tp)
4462 x5: link register (t0)
4463 x8: frame pointer (fp)
4464 x10-x11: arguments/return values (a0-1)
4465 x12-x17: arguments (a2-7)
4466 x28-31: temporaries (t3-6)
4467 pc: program counter (pc)
4469 ==> U-Boot will use gp to hold a pointer to the global data
4474 U-Boot runs in system state and uses physical addresses, i.e. the
4475 MMU is not used either for address mapping nor for memory protection.
4477 The available memory is mapped to fixed addresses using the memory
4478 controller. In this process, a contiguous block is formed for each
4479 memory type (Flash, SDRAM, SRAM), even when it consists of several
4480 physical memory banks.
4482 U-Boot is installed in the first 128 kB of the first Flash bank (on
4483 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4484 booting and sizing and initializing DRAM, the code relocates itself
4485 to the upper end of DRAM. Immediately below the U-Boot code some
4486 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4487 configuration setting]. Below that, a structure with global Board
4488 Info data is placed, followed by the stack (growing downward).
4490 Additionally, some exception handler code is copied to the low 8 kB
4491 of DRAM (0x00000000 ... 0x00001FFF).
4493 So a typical memory configuration with 16 MB of DRAM could look like
4496 0x0000 0000 Exception Vector code
4499 0x0000 2000 Free for Application Use
4505 0x00FB FF20 Monitor Stack (Growing downward)
4506 0x00FB FFAC Board Info Data and permanent copy of global data
4507 0x00FC 0000 Malloc Arena
4510 0x00FE 0000 RAM Copy of Monitor Code
4511 ... eventually: LCD or video framebuffer
4512 ... eventually: pRAM (Protected RAM - unchanged by reset)
4513 0x00FF FFFF [End of RAM]
4516 System Initialization:
4517 ----------------------
4519 In the reset configuration, U-Boot starts at the reset entry point
4520 (on most PowerPC systems at address 0x00000100). Because of the reset
4521 configuration for CS0# this is a mirror of the on board Flash memory.
4522 To be able to re-map memory U-Boot then jumps to its link address.
4523 To be able to implement the initialization code in C, a (small!)
4524 initial stack is set up in the internal Dual Ported RAM (in case CPUs
4525 which provide such a feature like), or in a locked part of the data
4526 cache. After that, U-Boot initializes the CPU core, the caches and
4529 Next, all (potentially) available memory banks are mapped using a
4530 preliminary mapping. For example, we put them on 512 MB boundaries
4531 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4532 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4533 programmed for SDRAM access. Using the temporary configuration, a
4534 simple memory test is run that determines the size of the SDRAM
4537 When there is more than one SDRAM bank, and the banks are of
4538 different size, the largest is mapped first. For equal size, the first
4539 bank (CS2#) is mapped first. The first mapping is always for address
4540 0x00000000, with any additional banks following immediately to create
4541 contiguous memory starting from 0.
4543 Then, the monitor installs itself at the upper end of the SDRAM area
4544 and allocates memory for use by malloc() and for the global Board
4545 Info data; also, the exception vector code is copied to the low RAM
4546 pages, and the final stack is set up.
4548 Only after this relocation will you have a "normal" C environment;
4549 until that you are restricted in several ways, mostly because you are
4550 running from ROM, and because the code will have to be relocated to a
4554 U-Boot Porting Guide:
4555 ----------------------
4557 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4561 int main(int argc, char *argv[])
4563 sighandler_t no_more_time;
4565 signal(SIGALRM, no_more_time);
4566 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4568 if (available_money > available_manpower) {
4569 Pay consultant to port U-Boot;
4573 Download latest U-Boot source;
4575 Subscribe to u-boot mailing list;
4578 email("Hi, I am new to U-Boot, how do I get started?");
4581 Read the README file in the top level directory;
4582 Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4583 Read applicable doc/README.*;
4584 Read the source, Luke;
4585 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4588 if (available_money > toLocalCurrency ($2500))
4591 Add a lot of aggravation and time;
4593 if (a similar board exists) { /* hopefully... */
4594 cp -a board/<similar> board/<myboard>
4595 cp include/configs/<similar>.h include/configs/<myboard>.h
4597 Create your own board support subdirectory;
4598 Create your own board include/configs/<myboard>.h file;
4600 Edit new board/<myboard> files
4601 Edit new include/configs/<myboard>.h
4606 Add / modify source code;
4610 email("Hi, I am having problems...");
4612 Send patch file to the U-Boot email list;
4613 if (reasonable critiques)
4614 Incorporate improvements from email list code review;
4616 Defend code as written;
4622 void no_more_time (int sig)
4631 All contributions to U-Boot should conform to the Linux kernel
4632 coding style; see the kernel coding style guide at
4633 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4634 script "scripts/Lindent" in your Linux kernel source directory.
4636 Source files originating from a different project (for example the
4637 MTD subsystem) are generally exempt from these guidelines and are not
4638 reformatted to ease subsequent migration to newer versions of those
4641 Please note that U-Boot is implemented in C (and to some small parts in
4642 Assembler); no C++ is used, so please do not use C++ style comments (//)
4645 Please also stick to the following formatting rules:
4646 - remove any trailing white space
4647 - use TAB characters for indentation and vertical alignment, not spaces
4648 - make sure NOT to use DOS '\r\n' line feeds
4649 - do not add more than 2 consecutive empty lines to source files
4650 - do not add trailing empty lines to source files
4652 Submissions which do not conform to the standards may be returned
4653 with a request to reformat the changes.
4659 Since the number of patches for U-Boot is growing, we need to
4660 establish some rules. Submissions which do not conform to these rules
4661 may be rejected, even when they contain important and valuable stuff.
4663 Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4665 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4666 see https://lists.denx.de/listinfo/u-boot
4668 When you send a patch, please include the following information with
4671 * For bug fixes: a description of the bug and how your patch fixes
4672 this bug. Please try to include a way of demonstrating that the
4673 patch actually fixes something.
4675 * For new features: a description of the feature and your
4678 * For major contributions, add a MAINTAINERS file with your
4679 information and associated file and directory references.
4681 * When you add support for a new board, don't forget to add a
4682 maintainer e-mail address to the boards.cfg file, too.
4684 * If your patch adds new configuration options, don't forget to
4685 document these in the README file.
4687 * The patch itself. If you are using git (which is *strongly*
4688 recommended) you can easily generate the patch using the
4689 "git format-patch". If you then use "git send-email" to send it to
4690 the U-Boot mailing list, you will avoid most of the common problems
4691 with some other mail clients.
4693 If you cannot use git, use "diff -purN OLD NEW". If your version of
4694 diff does not support these options, then get the latest version of
4697 The current directory when running this command shall be the parent
4698 directory of the U-Boot source tree (i. e. please make sure that
4699 your patch includes sufficient directory information for the
4702 We prefer patches as plain text. MIME attachments are discouraged,
4703 and compressed attachments must not be used.
4705 * If one logical set of modifications affects or creates several
4706 files, all these changes shall be submitted in a SINGLE patch file.
4708 * Changesets that contain different, unrelated modifications shall be
4709 submitted as SEPARATE patches, one patch per changeset.
4714 * Before sending the patch, run the buildman script on your patched
4715 source tree and make sure that no errors or warnings are reported
4716 for any of the boards.
4718 * Keep your modifications to the necessary minimum: A patch
4719 containing several unrelated changes or arbitrary reformats will be
4720 returned with a request to re-formatting / split it.
4722 * If you modify existing code, make sure that your new code does not
4723 add to the memory footprint of the code ;-) Small is beautiful!
4724 When adding new features, these should compile conditionally only
4725 (using #ifdef), and the resulting code with the new feature
4726 disabled must not need more memory than the old code without your
4729 * Remember that there is a size limit of 100 kB per message on the
4730 u-boot mailing list. Bigger patches will be moderated. If they are
4731 reasonable and not too big, they will be acknowledged. But patches
4732 bigger than the size limit should be avoided.