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
675 Only needed when CONFIG_BOOTDELAY is enabled;
676 define a command string that is automatically executed
677 when no character is read on the console interface
678 within "Boot Delay" after reset.
680 CONFIG_RAMBOOT and CONFIG_NFSBOOT
681 The value of these goes into the environment as
682 "ramboot" and "nfsboot" respectively, and can be used
683 as a convenience, when switching between booting from
686 - Serial Download Echo Mode:
688 If defined to 1, all characters received during a
689 serial download (using the "loads" command) are
690 echoed back. This might be needed by some terminal
691 emulations (like "cu"), but may as well just take
692 time on others. This setting #define's the initial
693 value of the "loads_echo" environment variable.
695 - Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
697 Select one of the baudrates listed in
698 CONFIG_SYS_BAUDRATE_TABLE, see below.
700 - Removal of commands
701 If no commands are needed to boot, you can disable
702 CONFIG_CMDLINE to remove them. In this case, the command line
703 will not be available, and when U-Boot wants to execute the
704 boot command (on start-up) it will call board_run_command()
705 instead. This can reduce image size significantly for very
706 simple boot procedures.
708 - Regular expression support:
710 If this variable is defined, U-Boot is linked against
711 the SLRE (Super Light Regular Expression) library,
712 which adds regex support to some commands, as for
713 example "env grep" and "setexpr".
717 If this variable is defined, U-Boot will use a device tree
718 to configure its devices, instead of relying on statically
719 compiled #defines in the board file. This option is
720 experimental and only available on a few boards. The device
721 tree is available in the global data as gd->fdt_blob.
723 U-Boot needs to get its device tree from somewhere. This can
724 be done using one of the three options below:
727 If this variable is defined, U-Boot will embed a device tree
728 binary in its image. This device tree file should be in the
729 board directory and called <soc>-<board>.dts. The binary file
730 is then picked up in board_init_f() and made available through
731 the global data structure as gd->fdt_blob.
734 If this variable is defined, U-Boot will build a device tree
735 binary. It will be called u-boot.dtb. Architecture-specific
736 code will locate it at run-time. Generally this works by:
738 cat u-boot.bin u-boot.dtb >image.bin
740 and in fact, U-Boot does this for you, creating a file called
741 u-boot-dtb.bin which is useful in the common case. You can
742 still use the individual files if you need something more
746 If this variable is defined, U-Boot will use the device tree
747 provided by the board at runtime instead of embedding one with
748 the image. Only boards defining board_fdt_blob_setup() support
749 this option (see include/fdtdec.h file).
753 If this variable is defined, it enables watchdog
754 support for the SoC. There must be support in the SoC
755 specific code for a watchdog. For the 8xx
756 CPUs, the SIU Watchdog feature is enabled in the SYPCR
757 register. When supported for a specific SoC is
758 available, then no further board specific code should
762 When using a watchdog circuitry external to the used
763 SoC, then define this variable and provide board
764 specific code for the "hw_watchdog_reset" function.
768 When CONFIG_CMD_DATE is selected, the type of the RTC
769 has to be selected, too. Define exactly one of the
772 CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
773 CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
774 CONFIG_RTC_MC146818 - use MC146818 RTC
775 CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
776 CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
777 CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
778 CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
779 CONFIG_RTC_DS164x - use Dallas DS164x RTC
780 CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
781 CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
782 CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
783 CONFIG_SYS_RV3029_TCR - enable trickle charger on
786 Note that if the RTC uses I2C, then the I2C interface
787 must also be configured. See I2C Support, below.
790 CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
792 The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
793 chip-ngpio pairs that tell the PCA953X driver the number of
794 pins supported by a particular chip.
796 Note that if the GPIO device uses I2C, then the I2C interface
797 must also be configured. See I2C Support, below.
800 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
801 accesses and can checksum them or write a list of them out
802 to memory. See the 'iotrace' command for details. This is
803 useful for testing device drivers since it can confirm that
804 the driver behaves the same way before and after a code
805 change. Currently this is supported on sandbox and arm. To
806 add support for your architecture, add '#include <iotrace.h>'
807 to the bottom of arch/<arch>/include/asm/io.h and test.
809 Example output from the 'iotrace stats' command is below.
810 Note that if the trace buffer is exhausted, the checksum will
811 still continue to operate.
814 Start: 10000000 (buffer start address)
815 Size: 00010000 (buffer size)
816 Offset: 00000120 (current buffer offset)
817 Output: 10000120 (start + offset)
818 Count: 00000018 (number of trace records)
819 CRC32: 9526fb66 (CRC32 of all trace records)
823 When CONFIG_TIMESTAMP is selected, the timestamp
824 (date and time) of an image is printed by image
825 commands like bootm or iminfo. This option is
826 automatically enabled when you select CONFIG_CMD_DATE .
828 - Partition Labels (disklabels) Supported:
829 Zero or more of the following:
830 CONFIG_MAC_PARTITION Apple's MacOS partition table.
831 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
832 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
833 bootloader. Note 2TB partition limit; see
835 CONFIG_SCSI) you must configure support for at
836 least one non-MTD partition type as well.
839 CONFIG_IDE_RESET_ROUTINE - this is defined in several
840 board configurations files but used nowhere!
842 CONFIG_IDE_RESET - is this is defined, IDE Reset will
843 be performed by calling the function
844 ide_set_reset(int reset)
845 which has to be defined in a board specific file
850 Set this to enable ATAPI support.
855 Set this to enable support for disks larger than 137GB
856 Also look at CONFIG_SYS_64BIT_LBA.
857 Whithout these , LBA48 support uses 32bit variables and will 'only'
858 support disks up to 2.1TB.
860 CONFIG_SYS_64BIT_LBA:
861 When enabled, makes the IDE subsystem use 64bit sector addresses.
865 CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
866 CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
867 CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
868 maximum numbers of LUNs, SCSI ID's and target
871 The environment variable 'scsidevs' is set to the number of
872 SCSI devices found during the last scan.
874 - NETWORK Support (PCI):
876 Support for Intel 8254x/8257x gigabit chips.
879 Utility code for direct access to the SPI bus on Intel 8257x.
880 This does not do anything useful unless you set at least one
881 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
883 CONFIG_E1000_SPI_GENERIC
884 Allow generic access to the SPI bus on the Intel 8257x, for
885 example with the "sspi" command.
888 Support for Digital 2114x chips.
891 Support for National dp83815 chips.
894 Support for National dp8382[01] gigabit chips.
896 - NETWORK Support (other):
898 CONFIG_DRIVER_AT91EMAC
899 Support for AT91RM9200 EMAC.
902 Define this to use reduced MII inteface
904 CONFIG_DRIVER_AT91EMAC_QUIET
905 If this defined, the driver is quiet.
906 The driver doen't show link status messages.
909 Support for the Calxeda XGMAC device
912 Support for SMSC's LAN91C96 chips.
914 CONFIG_LAN91C96_USE_32_BIT
915 Define this to enable 32 bit addressing
918 Support for SMSC's LAN91C111 chip
921 Define this to hold the physical address
922 of the device (I/O space)
924 CONFIG_SMC_USE_32_BIT
925 Define this if data bus is 32 bits
927 CONFIG_SMC_USE_IOFUNCS
928 Define this to use i/o functions instead of macros
929 (some hardware wont work with macros)
931 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
932 Define this if you have more then 3 PHYs.
935 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
937 CONFIG_FTGMAC100_EGIGA
938 Define this to use GE link update with gigabit PHY.
939 Define this if FTGMAC100 is connected to gigabit PHY.
940 If your system has 10/100 PHY only, it might not occur
941 wrong behavior. Because PHY usually return timeout or
942 useless data when polling gigabit status and gigabit
943 control registers. This behavior won't affect the
944 correctnessof 10/100 link speed update.
947 Support for Renesas on-chip Ethernet controller
949 CONFIG_SH_ETHER_USE_PORT
950 Define the number of ports to be used
952 CONFIG_SH_ETHER_PHY_ADDR
953 Define the ETH PHY's address
955 CONFIG_SH_ETHER_CACHE_WRITEBACK
956 If this option is set, the driver enables cache flush.
962 CONFIG_TPM_TIS_INFINEON
963 Support for Infineon i2c bus TPM devices. Only one device
964 per system is supported at this time.
966 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
967 Define the burst count bytes upper limit
970 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
972 CONFIG_TPM_ST33ZP24_I2C
973 Support for STMicroelectronics ST33ZP24 I2C devices.
974 Requires TPM_ST33ZP24 and I2C.
976 CONFIG_TPM_ST33ZP24_SPI
977 Support for STMicroelectronics ST33ZP24 SPI devices.
978 Requires TPM_ST33ZP24 and SPI.
981 Support for Atmel TWI TPM device. Requires I2C support.
984 Support for generic parallel port TPM devices. Only one device
985 per system is supported at this time.
987 CONFIG_TPM_TIS_BASE_ADDRESS
988 Base address where the generic TPM device is mapped
989 to. Contemporary x86 systems usually map it at
993 Define this to enable the TPM support library which provides
994 functional interfaces to some TPM commands.
995 Requires support for a TPM device.
997 CONFIG_TPM_AUTH_SESSIONS
998 Define this to enable authorized functions in the TPM library.
999 Requires CONFIG_TPM and CONFIG_SHA1.
1002 At the moment only the UHCI host controller is
1003 supported (PIP405, MIP405); define
1004 CONFIG_USB_UHCI to enable it.
1005 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1006 and define CONFIG_USB_STORAGE to enable the USB
1009 Supported are USB Keyboards and USB Floppy drives
1012 CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1013 txfilltuning field in the EHCI controller on reset.
1015 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1016 HW module registers.
1019 Define the below if you wish to use the USB console.
1020 Once firmware is rebuilt from a serial console issue the
1021 command "setenv stdin usbtty; setenv stdout usbtty" and
1022 attach your USB cable. The Unix command "dmesg" should print
1023 it has found a new device. The environment variable usbtty
1024 can be set to gserial or cdc_acm to enable your device to
1025 appear to a USB host as a Linux gserial device or a
1026 Common Device Class Abstract Control Model serial device.
1027 If you select usbtty = gserial you should be able to enumerate
1029 # modprobe usbserial vendor=0xVendorID product=0xProductID
1030 else if using cdc_acm, simply setting the environment
1031 variable usbtty to be cdc_acm should suffice. The following
1032 might be defined in YourBoardName.h
1035 Define this to build a UDC device
1038 Define this to have a tty type of device available to
1039 talk to the UDC device
1042 Define this to enable the high speed support for usb
1043 device and usbtty. If this feature is enabled, a routine
1044 int is_usbd_high_speed(void)
1045 also needs to be defined by the driver to dynamically poll
1046 whether the enumeration has succeded at high speed or full
1049 CONFIG_SYS_CONSOLE_IS_IN_ENV
1050 Define this if you want stdin, stdout &/or stderr to
1053 If you have a USB-IF assigned VendorID then you may wish to
1054 define your own vendor specific values either in BoardName.h
1055 or directly in usbd_vendor_info.h. If you don't define
1056 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1057 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1058 should pretend to be a Linux device to it's target host.
1060 CONFIG_USBD_MANUFACTURER
1061 Define this string as the name of your company for
1062 - CONFIG_USBD_MANUFACTURER "my company"
1064 CONFIG_USBD_PRODUCT_NAME
1065 Define this string as the name of your product
1066 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1068 CONFIG_USBD_VENDORID
1069 Define this as your assigned Vendor ID from the USB
1070 Implementors Forum. This *must* be a genuine Vendor ID
1071 to avoid polluting the USB namespace.
1072 - CONFIG_USBD_VENDORID 0xFFFF
1074 CONFIG_USBD_PRODUCTID
1075 Define this as the unique Product ID
1077 - CONFIG_USBD_PRODUCTID 0xFFFF
1079 - ULPI Layer Support:
1080 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1081 the generic ULPI layer. The generic layer accesses the ULPI PHY
1082 via the platform viewport, so you need both the genric layer and
1083 the viewport enabled. Currently only Chipidea/ARC based
1084 viewport is supported.
1085 To enable the ULPI layer support, define CONFIG_USB_ULPI and
1086 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1087 If your ULPI phy needs a different reference clock than the
1088 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1089 the appropriate value in Hz.
1092 The MMC controller on the Intel PXA is supported. To
1093 enable this define CONFIG_MMC. The MMC can be
1094 accessed from the boot prompt by mapping the device
1095 to physical memory similar to flash. Command line is
1096 enabled with CONFIG_CMD_MMC. The MMC driver also works with
1097 the FAT fs. This is enabled with CONFIG_CMD_FAT.
1100 Support for Renesas on-chip MMCIF controller
1102 CONFIG_SH_MMCIF_ADDR
1103 Define the base address of MMCIF registers
1106 Define the clock frequency for MMCIF
1108 - USB Device Firmware Update (DFU) class support:
1110 This enables the USB portion of the DFU USB class
1113 This enables support for exposing NAND devices via DFU.
1116 This enables support for exposing RAM via DFU.
1117 Note: DFU spec refer to non-volatile memory usage, but
1118 allow usages beyond the scope of spec - here RAM usage,
1119 one that would help mostly the developer.
1121 CONFIG_SYS_DFU_DATA_BUF_SIZE
1122 Dfu transfer uses a buffer before writing data to the
1123 raw storage device. Make the size (in bytes) of this buffer
1124 configurable. The size of this buffer is also configurable
1125 through the "dfu_bufsiz" environment variable.
1127 CONFIG_SYS_DFU_MAX_FILE_SIZE
1128 When updating files rather than the raw storage device,
1129 we use a static buffer to copy the file into and then write
1130 the buffer once we've been given the whole file. Define
1131 this to the maximum filesize (in bytes) for the buffer.
1132 Default is 4 MiB if undefined.
1134 DFU_DEFAULT_POLL_TIMEOUT
1135 Poll timeout [ms], is the timeout a device can send to the
1136 host. The host must wait for this timeout before sending
1137 a subsequent DFU_GET_STATUS request to the device.
1139 DFU_MANIFEST_POLL_TIMEOUT
1140 Poll timeout [ms], which the device sends to the host when
1141 entering dfuMANIFEST state. Host waits this timeout, before
1142 sending again an USB request to the device.
1144 - Journaling Flash filesystem support:
1146 Define these for a default partition on a NAND device
1148 CONFIG_SYS_JFFS2_FIRST_SECTOR,
1149 CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1150 Define these for a default partition on a NOR device
1153 See Kconfig help for available keyboard drivers.
1157 Define this to enable a custom keyboard support.
1158 This simply calls drv_keyboard_init() which must be
1159 defined in your board-specific files. This option is deprecated
1160 and is only used by novena. For new boards, use driver model
1165 Enable the Freescale DIU video driver. Reference boards for
1166 SOCs that have a DIU should define this macro to enable DIU
1167 support, and should also define these other macros:
1172 CONFIG_VIDEO_SW_CURSOR
1173 CONFIG_VGA_AS_SINGLE_DEVICE
1175 CONFIG_VIDEO_BMP_LOGO
1177 The DIU driver will look for the 'video-mode' environment
1178 variable, and if defined, enable the DIU as a console during
1179 boot. See the documentation file doc/README.video for a
1180 description of this variable.
1182 - LCD Support: CONFIG_LCD
1184 Define this to enable LCD support (for output to LCD
1185 display); also select one of the supported displays
1186 by defining one of these:
1190 HITACHI TX09D70VM1CCA, 3.5", 240x320.
1192 CONFIG_NEC_NL6448AC33:
1194 NEC NL6448AC33-18. Active, color, single scan.
1196 CONFIG_NEC_NL6448BC20
1198 NEC NL6448BC20-08. 6.5", 640x480.
1199 Active, color, single scan.
1201 CONFIG_NEC_NL6448BC33_54
1203 NEC NL6448BC33-54. 10.4", 640x480.
1204 Active, color, single scan.
1208 Sharp 320x240. Active, color, single scan.
1209 It isn't 16x9, and I am not sure what it is.
1211 CONFIG_SHARP_LQ64D341
1213 Sharp LQ64D341 display, 640x480.
1214 Active, color, single scan.
1218 HLD1045 display, 640x480.
1219 Active, color, single scan.
1223 Optrex CBL50840-2 NF-FW 99 22 M5
1225 Hitachi LMG6912RPFC-00T
1229 320x240. Black & white.
1231 CONFIG_LCD_ALIGNMENT
1233 Normally the LCD is page-aligned (typically 4KB). If this is
1234 defined then the LCD will be aligned to this value instead.
1235 For ARM it is sometimes useful to use MMU_SECTION_SIZE
1236 here, since it is cheaper to change data cache settings on
1237 a per-section basis.
1242 Sometimes, for example if the display is mounted in portrait
1243 mode or even if it's mounted landscape but rotated by 180degree,
1244 we need to rotate our content of the display relative to the
1245 framebuffer, so that user can read the messages which are
1247 Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1248 initialized with a given rotation from "vl_rot" out of
1249 "vidinfo_t" which is provided by the board specific code.
1250 The value for vl_rot is coded as following (matching to
1251 fbcon=rotate:<n> linux-kernel commandline):
1252 0 = no rotation respectively 0 degree
1253 1 = 90 degree rotation
1254 2 = 180 degree rotation
1255 3 = 270 degree rotation
1257 If CONFIG_LCD_ROTATION is not defined, the console will be
1258 initialized with 0degree rotation.
1262 Support drawing of RLE8-compressed bitmaps on the LCD.
1266 Enables an 'i2c edid' command which can read EDID
1267 information over I2C from an attached LCD display.
1269 - Splash Screen Support: CONFIG_SPLASH_SCREEN
1271 If this option is set, the environment is checked for
1272 a variable "splashimage". If found, the usual display
1273 of logo, copyright and system information on the LCD
1274 is suppressed and the BMP image at the address
1275 specified in "splashimage" is loaded instead. The
1276 console is redirected to the "nulldev", too. This
1277 allows for a "silent" boot where a splash screen is
1278 loaded very quickly after power-on.
1280 CONFIG_SPLASHIMAGE_GUARD
1282 If this option is set, then U-Boot will prevent the environment
1283 variable "splashimage" from being set to a problematic address
1284 (see doc/README.displaying-bmps).
1285 This option is useful for targets where, due to alignment
1286 restrictions, an improperly aligned BMP image will cause a data
1287 abort. If you think you will not have problems with unaligned
1288 accesses (for example because your toolchain prevents them)
1289 there is no need to set this option.
1291 CONFIG_SPLASH_SCREEN_ALIGN
1293 If this option is set the splash image can be freely positioned
1294 on the screen. Environment variable "splashpos" specifies the
1295 position as "x,y". If a positive number is given it is used as
1296 number of pixel from left/top. If a negative number is given it
1297 is used as number of pixel from right/bottom. You can also
1298 specify 'm' for centering the image.
1301 setenv splashpos m,m
1302 => image at center of screen
1304 setenv splashpos 30,20
1305 => image at x = 30 and y = 20
1307 setenv splashpos -10,m
1308 => vertically centered image
1309 at x = dspWidth - bmpWidth - 9
1311 - Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1313 If this option is set, additionally to standard BMP
1314 images, gzipped BMP images can be displayed via the
1315 splashscreen support or the bmp command.
1317 - Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1319 If this option is set, 8-bit RLE compressed BMP images
1320 can be displayed via the splashscreen support or the
1324 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1326 The clock frequency of the MII bus
1328 CONFIG_PHY_RESET_DELAY
1330 Some PHY like Intel LXT971A need extra delay after
1331 reset before any MII register access is possible.
1332 For such PHY, set this option to the usec delay
1333 required. (minimum 300usec for LXT971A)
1335 CONFIG_PHY_CMD_DELAY (ppc4xx)
1337 Some PHY like Intel LXT971A need extra delay after
1338 command issued before MII status register can be read
1343 Define a default value for the IP address to use for
1344 the default Ethernet interface, in case this is not
1345 determined through e.g. bootp.
1346 (Environment variable "ipaddr")
1348 - Server IP address:
1351 Defines a default value for the IP address of a TFTP
1352 server to contact when using the "tftboot" command.
1353 (Environment variable "serverip")
1355 CONFIG_KEEP_SERVERADDR
1357 Keeps the server's MAC address, in the env 'serveraddr'
1358 for passing to bootargs (like Linux's netconsole option)
1360 - Gateway IP address:
1363 Defines a default value for the IP address of the
1364 default router where packets to other networks are
1366 (Environment variable "gatewayip")
1371 Defines a default value for the subnet mask (or
1372 routing prefix) which is used to determine if an IP
1373 address belongs to the local subnet or needs to be
1374 forwarded through a router.
1375 (Environment variable "netmask")
1377 - BOOTP Recovery Mode:
1378 CONFIG_BOOTP_RANDOM_DELAY
1380 If you have many targets in a network that try to
1381 boot using BOOTP, you may want to avoid that all
1382 systems send out BOOTP requests at precisely the same
1383 moment (which would happen for instance at recovery
1384 from a power failure, when all systems will try to
1385 boot, thus flooding the BOOTP server. Defining
1386 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1387 inserted before sending out BOOTP requests. The
1388 following delays are inserted then:
1390 1st BOOTP request: delay 0 ... 1 sec
1391 2nd BOOTP request: delay 0 ... 2 sec
1392 3rd BOOTP request: delay 0 ... 4 sec
1394 BOOTP requests: delay 0 ... 8 sec
1396 CONFIG_BOOTP_ID_CACHE_SIZE
1398 BOOTP packets are uniquely identified using a 32-bit ID. The
1399 server will copy the ID from client requests to responses and
1400 U-Boot will use this to determine if it is the destination of
1401 an incoming response. Some servers will check that addresses
1402 aren't in use before handing them out (usually using an ARP
1403 ping) and therefore take up to a few hundred milliseconds to
1404 respond. Network congestion may also influence the time it
1405 takes for a response to make it back to the client. If that
1406 time is too long, U-Boot will retransmit requests. In order
1407 to allow earlier responses to still be accepted after these
1408 retransmissions, U-Boot's BOOTP client keeps a small cache of
1409 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1410 cache. The default is to keep IDs for up to four outstanding
1411 requests. Increasing this will allow U-Boot to accept offers
1412 from a BOOTP client in networks with unusually high latency.
1414 - DHCP Advanced Options:
1415 You can fine tune the DHCP functionality by defining
1416 CONFIG_BOOTP_* symbols:
1418 CONFIG_BOOTP_NISDOMAIN
1419 CONFIG_BOOTP_BOOTFILESIZE
1420 CONFIG_BOOTP_SEND_HOSTNAME
1421 CONFIG_BOOTP_NTPSERVER
1422 CONFIG_BOOTP_TIMEOFFSET
1423 CONFIG_BOOTP_VENDOREX
1424 CONFIG_BOOTP_MAY_FAIL
1426 CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1427 environment variable, not the BOOTP server.
1429 CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1430 after the configured retry count, the call will fail
1431 instead of starting over. This can be used to fail over
1432 to Link-local IP address configuration if the DHCP server
1435 CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1436 to do a dynamic update of a DNS server. To do this, they
1437 need the hostname of the DHCP requester.
1438 If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1439 of the "hostname" environment variable is passed as
1440 option 12 to the DHCP server.
1442 CONFIG_BOOTP_DHCP_REQUEST_DELAY
1444 A 32bit value in microseconds for a delay between
1445 receiving a "DHCP Offer" and sending the "DHCP Request".
1446 This fixes a problem with certain DHCP servers that don't
1447 respond 100% of the time to a "DHCP request". E.g. On an
1448 AT91RM9200 processor running at 180MHz, this delay needed
1449 to be *at least* 15,000 usec before a Windows Server 2003
1450 DHCP server would reply 100% of the time. I recommend at
1451 least 50,000 usec to be safe. The alternative is to hope
1452 that one of the retries will be successful but note that
1453 the DHCP timeout and retry process takes a longer than
1456 - Link-local IP address negotiation:
1457 Negotiate with other link-local clients on the local network
1458 for an address that doesn't require explicit configuration.
1459 This is especially useful if a DHCP server cannot be guaranteed
1460 to exist in all environments that the device must operate.
1462 See doc/README.link-local for more information.
1464 - MAC address from environment variables
1466 FDT_SEQ_MACADDR_FROM_ENV
1468 Fix-up device tree with MAC addresses fetched sequentially from
1469 environment variables. This config work on assumption that
1470 non-usable ethernet node of device-tree are either not present
1471 or their status has been marked as "disabled".
1474 CONFIG_CDP_DEVICE_ID
1476 The device id used in CDP trigger frames.
1478 CONFIG_CDP_DEVICE_ID_PREFIX
1480 A two character string which is prefixed to the MAC address
1485 A printf format string which contains the ascii name of
1486 the port. Normally is set to "eth%d" which sets
1487 eth0 for the first Ethernet, eth1 for the second etc.
1489 CONFIG_CDP_CAPABILITIES
1491 A 32bit integer which indicates the device capabilities;
1492 0x00000010 for a normal host which does not forwards.
1496 An ascii string containing the version of the software.
1500 An ascii string containing the name of the platform.
1504 A 32bit integer sent on the trigger.
1506 CONFIG_CDP_POWER_CONSUMPTION
1508 A 16bit integer containing the power consumption of the
1509 device in .1 of milliwatts.
1511 CONFIG_CDP_APPLIANCE_VLAN_TYPE
1513 A byte containing the id of the VLAN.
1515 - Status LED: CONFIG_LED_STATUS
1517 Several configurations allow to display the current
1518 status using a LED. For instance, the LED will blink
1519 fast while running U-Boot code, stop blinking as
1520 soon as a reply to a BOOTP request was received, and
1521 start blinking slow once the Linux kernel is running
1522 (supported by a status LED driver in the Linux
1523 kernel). Defining CONFIG_LED_STATUS enables this
1528 CONFIG_LED_STATUS_GPIO
1529 The status LED can be connected to a GPIO pin.
1530 In such cases, the gpio_led driver can be used as a
1531 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1532 to include the gpio_led driver in the U-Boot binary.
1534 CONFIG_GPIO_LED_INVERTED_TABLE
1535 Some GPIO connected LEDs may have inverted polarity in which
1536 case the GPIO high value corresponds to LED off state and
1537 GPIO low value corresponds to LED on state.
1538 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1539 with a list of GPIO LEDs that have inverted polarity.
1541 - I2C Support: CONFIG_SYS_I2C
1543 This enable the NEW i2c subsystem, and will allow you to use
1544 i2c commands at the u-boot command line (as long as you set
1545 CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1546 for defining speed and slave address
1547 - activate second bus with I2C_SOFT_DECLARATIONS2 define
1548 CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1549 for defining speed and slave address
1550 - activate third bus with I2C_SOFT_DECLARATIONS3 define
1551 CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1552 for defining speed and slave address
1553 - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1554 CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1555 for defining speed and slave address
1557 - drivers/i2c/fsl_i2c.c:
1558 - activate i2c driver with CONFIG_SYS_I2C_FSL
1559 define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1560 offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1561 CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1563 - If your board supports a second fsl i2c bus, define
1564 CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1565 CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1566 CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1569 - drivers/i2c/tegra_i2c.c:
1570 - activate this driver with CONFIG_SYS_I2C_TEGRA
1571 - This driver adds 4 i2c buses with a fix speed from
1572 100000 and the slave addr 0!
1574 - drivers/i2c/ppc4xx_i2c.c
1575 - activate this driver with CONFIG_SYS_I2C_PPC4XX
1576 - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1577 - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1579 - drivers/i2c/i2c_mxc.c
1580 - activate this driver with CONFIG_SYS_I2C_MXC
1581 - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1582 - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1583 - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1584 - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1585 - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1586 - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1587 - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1588 - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1589 - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1590 - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1591 - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1592 - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1593 If those defines are not set, default value is 100000
1594 for speed, and 0 for slave.
1596 - drivers/i2c/rcar_i2c.c:
1597 - activate this driver with CONFIG_SYS_I2C_RCAR
1598 - This driver adds 4 i2c buses
1600 - drivers/i2c/sh_i2c.c:
1601 - activate this driver with CONFIG_SYS_I2C_SH
1602 - This driver adds from 2 to 5 i2c buses
1604 - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1605 - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1606 - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1607 - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1608 - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1609 - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1610 - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1611 - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1612 - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1613 - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1614 - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1616 - drivers/i2c/omap24xx_i2c.c
1617 - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1618 - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1619 - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1620 - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1621 - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1622 - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1623 - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1624 - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1625 - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1626 - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1627 - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1629 - drivers/i2c/s3c24x0_i2c.c:
1630 - activate this driver with CONFIG_SYS_I2C_S3C24X0
1631 - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1632 9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1633 with a fix speed from 100000 and the slave addr 0!
1635 - drivers/i2c/ihs_i2c.c
1636 - activate this driver with CONFIG_SYS_I2C_IHS
1637 - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1638 - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1639 - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1640 - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1641 - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1642 - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1643 - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1644 - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1645 - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1646 - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1647 - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1648 - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1649 - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1650 - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1651 - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1652 - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1653 - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1654 - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1655 - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1656 - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1657 - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1661 CONFIG_SYS_NUM_I2C_BUSES
1662 Hold the number of i2c buses you want to use.
1664 CONFIG_SYS_I2C_DIRECT_BUS
1665 define this, if you don't use i2c muxes on your hardware.
1666 if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1669 CONFIG_SYS_I2C_MAX_HOPS
1670 define how many muxes are maximal consecutively connected
1671 on one i2c bus. If you not use i2c muxes, omit this
1674 CONFIG_SYS_I2C_BUSES
1675 hold a list of buses you want to use, only used if
1676 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1677 a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1678 CONFIG_SYS_NUM_I2C_BUSES = 9:
1680 CONFIG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
1681 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1682 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1683 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1684 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1685 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1686 {1, {I2C_NULL_HOP}}, \
1687 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1688 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1692 bus 0 on adapter 0 without a mux
1693 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1694 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1695 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1696 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1697 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1698 bus 6 on adapter 1 without a mux
1699 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1700 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1702 If you do not have i2c muxes on your board, omit this define.
1704 - Legacy I2C Support:
1705 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1706 then the following macros need to be defined (examples are
1707 from include/configs/lwmon.h):
1711 (Optional). Any commands necessary to enable the I2C
1712 controller or configure ports.
1714 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
1718 The code necessary to make the I2C data line active
1719 (driven). If the data line is open collector, this
1722 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
1726 The code necessary to make the I2C data line tri-stated
1727 (inactive). If the data line is open collector, this
1730 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1734 Code that returns true if the I2C data line is high,
1737 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1741 If <bit> is true, sets the I2C data line high. If it
1742 is false, it clears it (low).
1744 eg: #define I2C_SDA(bit) \
1745 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
1746 else immr->im_cpm.cp_pbdat &= ~PB_SDA
1750 If <bit> is true, sets the I2C clock line high. If it
1751 is false, it clears it (low).
1753 eg: #define I2C_SCL(bit) \
1754 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
1755 else immr->im_cpm.cp_pbdat &= ~PB_SCL
1759 This delay is invoked four times per clock cycle so this
1760 controls the rate of data transfer. The data rate thus
1761 is 1 / (I2C_DELAY * 4). Often defined to be something
1764 #define I2C_DELAY udelay(2)
1766 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1768 If your arch supports the generic GPIO framework (asm/gpio.h),
1769 then you may alternatively define the two GPIOs that are to be
1770 used as SCL / SDA. Any of the previous I2C_xxx macros will
1771 have GPIO-based defaults assigned to them as appropriate.
1773 You should define these to the GPIO value as given directly to
1774 the generic GPIO functions.
1776 CONFIG_SYS_I2C_INIT_BOARD
1778 When a board is reset during an i2c bus transfer
1779 chips might think that the current transfer is still
1780 in progress. On some boards it is possible to access
1781 the i2c SCLK line directly, either by using the
1782 processor pin as a GPIO or by having a second pin
1783 connected to the bus. If this option is defined a
1784 custom i2c_init_board() routine in boards/xxx/board.c
1785 is run early in the boot sequence.
1787 CONFIG_I2C_MULTI_BUS
1789 This option allows the use of multiple I2C buses, each of which
1790 must have a controller. At any point in time, only one bus is
1791 active. To switch to a different bus, use the 'i2c dev' command.
1792 Note that bus numbering is zero-based.
1794 CONFIG_SYS_I2C_NOPROBES
1796 This option specifies a list of I2C devices that will be skipped
1797 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
1798 is set, specify a list of bus-device pairs. Otherwise, specify
1799 a 1D array of device addresses
1802 #undef CONFIG_I2C_MULTI_BUS
1803 #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1805 will skip addresses 0x50 and 0x68 on a board with one I2C bus
1807 #define CONFIG_I2C_MULTI_BUS
1808 #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1810 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1812 CONFIG_SYS_SPD_BUS_NUM
1814 If defined, then this indicates the I2C bus number for DDR SPD.
1815 If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1817 CONFIG_SYS_RTC_BUS_NUM
1819 If defined, then this indicates the I2C bus number for the RTC.
1820 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1822 CONFIG_SOFT_I2C_READ_REPEATED_START
1824 defining this will force the i2c_read() function in
1825 the soft_i2c driver to perform an I2C repeated start
1826 between writing the address pointer and reading the
1827 data. If this define is omitted the default behaviour
1828 of doing a stop-start sequence will be used. Most I2C
1829 devices can use either method, but some require one or
1832 - SPI Support: CONFIG_SPI
1834 Enables SPI driver (so far only tested with
1835 SPI EEPROM, also an instance works with Crystal A/D and
1836 D/As on the SACSng board)
1840 Enables a software (bit-bang) SPI driver rather than
1841 using hardware support. This is a general purpose
1842 driver that only requires three general I/O port pins
1843 (two outputs, one input) to function. If this is
1844 defined, the board configuration must define several
1845 SPI configuration items (port pins to use, etc). For
1846 an example, see include/configs/sacsng.h.
1848 CONFIG_SYS_SPI_MXC_WAIT
1849 Timeout for waiting until spi transfer completed.
1850 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1852 - FPGA Support: CONFIG_FPGA
1854 Enables FPGA subsystem.
1856 CONFIG_FPGA_<vendor>
1858 Enables support for specific chip vendors.
1861 CONFIG_FPGA_<family>
1863 Enables support for FPGA family.
1864 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1868 Specify the number of FPGA devices to support.
1870 CONFIG_SYS_FPGA_PROG_FEEDBACK
1872 Enable printing of hash marks during FPGA configuration.
1874 CONFIG_SYS_FPGA_CHECK_BUSY
1876 Enable checks on FPGA configuration interface busy
1877 status by the configuration function. This option
1878 will require a board or device specific function to
1883 If defined, a function that provides delays in the FPGA
1884 configuration driver.
1886 CONFIG_SYS_FPGA_CHECK_CTRLC
1887 Allow Control-C to interrupt FPGA configuration
1889 CONFIG_SYS_FPGA_CHECK_ERROR
1891 Check for configuration errors during FPGA bitfile
1892 loading. For example, abort during Virtex II
1893 configuration if the INIT_B line goes low (which
1894 indicated a CRC error).
1896 CONFIG_SYS_FPGA_WAIT_INIT
1898 Maximum time to wait for the INIT_B line to de-assert
1899 after PROB_B has been de-asserted during a Virtex II
1900 FPGA configuration sequence. The default time is 500
1903 CONFIG_SYS_FPGA_WAIT_BUSY
1905 Maximum time to wait for BUSY to de-assert during
1906 Virtex II FPGA configuration. The default is 5 ms.
1908 CONFIG_SYS_FPGA_WAIT_CONFIG
1910 Time to wait after FPGA configuration. The default is
1913 - Configuration Management:
1917 If defined, this string will be added to the U-Boot
1918 version information (U_BOOT_VERSION)
1920 - Vendor Parameter Protection:
1922 U-Boot considers the values of the environment
1923 variables "serial#" (Board Serial Number) and
1924 "ethaddr" (Ethernet Address) to be parameters that
1925 are set once by the board vendor / manufacturer, and
1926 protects these variables from casual modification by
1927 the user. Once set, these variables are read-only,
1928 and write or delete attempts are rejected. You can
1929 change this behaviour:
1931 If CONFIG_ENV_OVERWRITE is #defined in your config
1932 file, the write protection for vendor parameters is
1933 completely disabled. Anybody can change or delete
1936 Alternatively, if you define _both_ an ethaddr in the
1937 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1938 Ethernet address is installed in the environment,
1939 which can be changed exactly ONCE by the user. [The
1940 serial# is unaffected by this, i. e. it remains
1943 The same can be accomplished in a more flexible way
1944 for any variable by configuring the type of access
1945 to allow for those variables in the ".flags" variable
1946 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1951 Define this variable to enable the reservation of
1952 "protected RAM", i. e. RAM which is not overwritten
1953 by U-Boot. Define CONFIG_PRAM to hold the number of
1954 kB you want to reserve for pRAM. You can overwrite
1955 this default value by defining an environment
1956 variable "pram" to the number of kB you want to
1957 reserve. Note that the board info structure will
1958 still show the full amount of RAM. If pRAM is
1959 reserved, a new environment variable "mem" will
1960 automatically be defined to hold the amount of
1961 remaining RAM in a form that can be passed as boot
1962 argument to Linux, for instance like that:
1964 setenv bootargs ... mem=\${mem}
1967 This way you can tell Linux not to use this memory,
1968 either, which results in a memory region that will
1969 not be affected by reboots.
1971 *WARNING* If your board configuration uses automatic
1972 detection of the RAM size, you must make sure that
1973 this memory test is non-destructive. So far, the
1974 following board configurations are known to be
1977 IVMS8, IVML24, SPD8xx,
1978 HERMES, IP860, RPXlite, LWMON,
1981 - Access to physical memory region (> 4GB)
1982 Some basic support is provided for operations on memory not
1983 normally accessible to U-Boot - e.g. some architectures
1984 support access to more than 4GB of memory on 32-bit
1985 machines using physical address extension or similar.
1986 Define CONFIG_PHYSMEM to access this basic support, which
1987 currently only supports clearing the memory.
1990 CONFIG_NET_RETRY_COUNT
1992 This variable defines the number of retries for
1993 network operations like ARP, RARP, TFTP, or BOOTP
1994 before giving up the operation. If not defined, a
1995 default value of 5 is used.
1999 Timeout waiting for an ARP reply in milliseconds.
2003 Timeout in milliseconds used in NFS protocol.
2004 If you encounter "ERROR: Cannot umount" in nfs command,
2005 try longer timeout such as
2006 #define CONFIG_NFS_TIMEOUT 10000UL
2008 - Command Interpreter:
2009 CONFIG_SYS_PROMPT_HUSH_PS2
2011 This defines the secondary prompt string, which is
2012 printed when the command interpreter needs more input
2013 to complete a command. Usually "> ".
2017 In the current implementation, the local variables
2018 space and global environment variables space are
2019 separated. Local variables are those you define by
2020 simply typing `name=value'. To access a local
2021 variable later on, you have write `$name' or
2022 `${name}'; to execute the contents of a variable
2023 directly type `$name' at the command prompt.
2025 Global environment variables are those you use
2026 setenv/printenv to work with. To run a command stored
2027 in such a variable, you need to use the run command,
2028 and you must not use the '$' sign to access them.
2030 To store commands and special characters in a
2031 variable, please use double quotation marks
2032 surrounding the whole text of the variable, instead
2033 of the backslashes before semicolons and special
2036 - Command Line Editing and History:
2037 CONFIG_CMDLINE_PS_SUPPORT
2039 Enable support for changing the command prompt string
2040 at run-time. Only static string is supported so far.
2041 The string is obtained from environment variables PS1
2044 - Default Environment:
2045 CONFIG_EXTRA_ENV_SETTINGS
2047 Define this to contain any number of null terminated
2048 strings (variable = value pairs) that will be part of
2049 the default environment compiled into the boot image.
2051 For example, place something like this in your
2052 board's config file:
2054 #define CONFIG_EXTRA_ENV_SETTINGS \
2058 Warning: This method is based on knowledge about the
2059 internal format how the environment is stored by the
2060 U-Boot code. This is NOT an official, exported
2061 interface! Although it is unlikely that this format
2062 will change soon, there is no guarantee either.
2063 You better know what you are doing here.
2065 Note: overly (ab)use of the default environment is
2066 discouraged. Make sure to check other ways to preset
2067 the environment like the "source" command or the
2070 CONFIG_DELAY_ENVIRONMENT
2072 Normally the environment is loaded when the board is
2073 initialised so that it is available to U-Boot. This inhibits
2074 that so that the environment is not available until
2075 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2076 this is instead controlled by the value of
2077 /config/load-environment.
2079 - TFTP Fixed UDP Port:
2082 If this is defined, the environment variable tftpsrcp
2083 is used to supply the TFTP UDP source port value.
2084 If tftpsrcp isn't defined, the normal pseudo-random port
2085 number generator is used.
2087 Also, the environment variable tftpdstp is used to supply
2088 the TFTP UDP destination port value. If tftpdstp isn't
2089 defined, the normal port 69 is used.
2091 The purpose for tftpsrcp is to allow a TFTP server to
2092 blindly start the TFTP transfer using the pre-configured
2093 target IP address and UDP port. This has the effect of
2094 "punching through" the (Windows XP) firewall, allowing
2095 the remainder of the TFTP transfer to proceed normally.
2096 A better solution is to properly configure the firewall,
2097 but sometimes that is not allowed.
2099 CONFIG_STANDALONE_LOAD_ADDR
2101 This option defines a board specific value for the
2102 address where standalone program gets loaded, thus
2103 overwriting the architecture dependent default
2106 - Frame Buffer Address:
2109 Define CONFIG_FB_ADDR if you want to use specific
2110 address for frame buffer. This is typically the case
2111 when using a graphics controller has separate video
2112 memory. U-Boot will then place the frame buffer at
2113 the given address instead of dynamically reserving it
2114 in system RAM by calling lcd_setmem(), which grabs
2115 the memory for the frame buffer depending on the
2116 configured panel size.
2118 Please see board_init_f function.
2120 - Automatic software updates via TFTP server
2122 CONFIG_UPDATE_TFTP_CNT_MAX
2123 CONFIG_UPDATE_TFTP_MSEC_MAX
2125 These options enable and control the auto-update feature;
2126 for a more detailed description refer to doc/README.update.
2128 - MTD Support (mtdparts command, UBI support)
2129 CONFIG_MTD_UBI_WL_THRESHOLD
2130 This parameter defines the maximum difference between the highest
2131 erase counter value and the lowest erase counter value of eraseblocks
2132 of UBI devices. When this threshold is exceeded, UBI starts performing
2133 wear leveling by means of moving data from eraseblock with low erase
2134 counter to eraseblocks with high erase counter.
2136 The default value should be OK for SLC NAND flashes, NOR flashes and
2137 other flashes which have eraseblock life-cycle 100000 or more.
2138 However, in case of MLC NAND flashes which typically have eraseblock
2139 life-cycle less than 10000, the threshold should be lessened (e.g.,
2140 to 128 or 256, although it does not have to be power of 2).
2144 CONFIG_MTD_UBI_BEB_LIMIT
2145 This option specifies the maximum bad physical eraseblocks UBI
2146 expects on the MTD device (per 1024 eraseblocks). If the
2147 underlying flash does not admit of bad eraseblocks (e.g. NOR
2148 flash), this value is ignored.
2150 NAND datasheets often specify the minimum and maximum NVM
2151 (Number of Valid Blocks) for the flashes' endurance lifetime.
2152 The maximum expected bad eraseblocks per 1024 eraseblocks
2153 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2154 which gives 20 for most NANDs (MaxNVB is basically the total
2155 count of eraseblocks on the chip).
2157 To put it differently, if this value is 20, UBI will try to
2158 reserve about 1.9% of physical eraseblocks for bad blocks
2159 handling. And that will be 1.9% of eraseblocks on the entire
2160 NAND chip, not just the MTD partition UBI attaches. This means
2161 that if you have, say, a NAND flash chip admits maximum 40 bad
2162 eraseblocks, and it is split on two MTD partitions of the same
2163 size, UBI will reserve 40 eraseblocks when attaching a
2168 CONFIG_MTD_UBI_FASTMAP
2169 Fastmap is a mechanism which allows attaching an UBI device
2170 in nearly constant time. Instead of scanning the whole MTD device it
2171 only has to locate a checkpoint (called fastmap) on the device.
2172 The on-flash fastmap contains all information needed to attach
2173 the device. Using fastmap makes only sense on large devices where
2174 attaching by scanning takes long. UBI will not automatically install
2175 a fastmap on old images, but you can set the UBI parameter
2176 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2177 that fastmap-enabled images are still usable with UBI implementations
2178 without fastmap support. On typical flash devices the whole fastmap
2179 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2181 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2182 Set this parameter to enable fastmap automatically on images
2186 CONFIG_MTD_UBI_FM_DEBUG
2187 Enable UBI fastmap debug
2192 Enable building of SPL globally.
2195 LDSCRIPT for linking the SPL binary.
2197 CONFIG_SPL_MAX_FOOTPRINT
2198 Maximum size in memory allocated to the SPL, BSS included.
2199 When defined, the linker checks that the actual memory
2200 used by SPL from _start to __bss_end does not exceed it.
2201 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2202 must not be both defined at the same time.
2205 Maximum size of the SPL image (text, data, rodata, and
2206 linker lists sections), BSS excluded.
2207 When defined, the linker checks that the actual size does
2210 CONFIG_SPL_RELOC_TEXT_BASE
2211 Address to relocate to. If unspecified, this is equal to
2212 CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2214 CONFIG_SPL_BSS_START_ADDR
2215 Link address for the BSS within the SPL binary.
2217 CONFIG_SPL_BSS_MAX_SIZE
2218 Maximum size in memory allocated to the SPL BSS.
2219 When defined, the linker checks that the actual memory used
2220 by SPL from __bss_start to __bss_end does not exceed it.
2221 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2222 must not be both defined at the same time.
2225 Adress of the start of the stack SPL will use
2227 CONFIG_SPL_PANIC_ON_RAW_IMAGE
2228 When defined, SPL will panic() if the image it has
2229 loaded does not have a signature.
2230 Defining this is useful when code which loads images
2231 in SPL cannot guarantee that absolutely all read errors
2233 An example is the LPC32XX MLC NAND driver, which will
2234 consider that a completely unreadable NAND block is bad,
2235 and thus should be skipped silently.
2237 CONFIG_SPL_RELOC_STACK
2238 Adress of the start of the stack SPL will use after
2239 relocation. If unspecified, this is equal to
2242 CONFIG_SYS_SPL_MALLOC_START
2243 Starting address of the malloc pool used in SPL.
2244 When this option is set the full malloc is used in SPL and
2245 it is set up by spl_init() and before that, the simple malloc()
2246 can be used if CONFIG_SYS_MALLOC_F is defined.
2248 CONFIG_SYS_SPL_MALLOC_SIZE
2249 The size of the malloc pool used in SPL.
2252 Enable booting directly to an OS from SPL.
2253 See also: doc/README.falcon
2255 CONFIG_SPL_DISPLAY_PRINT
2256 For ARM, enable an optional function to print more information
2257 about the running system.
2259 CONFIG_SPL_INIT_MINIMAL
2260 Arch init code should be built for a very small image
2262 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2263 Partition on the MMC to load U-Boot from when the MMC is being
2266 CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2267 Sector to load kernel uImage from when MMC is being
2268 used in raw mode (for Falcon mode)
2270 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2271 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2272 Sector and number of sectors to load kernel argument
2273 parameters from when MMC is being used in raw mode
2276 CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2277 Partition on the MMC to load U-Boot from when the MMC is being
2280 CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2281 Filename to read to load U-Boot when reading from filesystem
2283 CONFIG_SPL_FS_LOAD_KERNEL_NAME
2284 Filename to read to load kernel uImage when reading
2285 from filesystem (for Falcon mode)
2287 CONFIG_SPL_FS_LOAD_ARGS_NAME
2288 Filename to read to load kernel argument parameters
2289 when reading from filesystem (for Falcon mode)
2291 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2292 Set this for NAND SPL on PPC mpc83xx targets, so that
2293 start.S waits for the rest of the SPL to load before
2294 continuing (the hardware starts execution after just
2295 loading the first page rather than the full 4K).
2297 CONFIG_SPL_SKIP_RELOCATE
2298 Avoid SPL relocation
2300 CONFIG_SPL_NAND_BASE
2301 Include nand_base.c in the SPL. Requires
2302 CONFIG_SPL_NAND_DRIVERS.
2304 CONFIG_SPL_NAND_DRIVERS
2305 SPL uses normal NAND drivers, not minimal drivers.
2307 CONFIG_SPL_NAND_IDENT
2308 SPL uses the chip ID list to identify the NAND flash.
2309 Requires CONFIG_SPL_NAND_BASE.
2312 Include standard software ECC in the SPL
2314 CONFIG_SPL_NAND_SIMPLE
2315 Support for NAND boot using simple NAND drivers that
2316 expose the cmd_ctrl() interface.
2319 Support for a lightweight UBI (fastmap) scanner and
2322 CONFIG_SPL_NAND_RAW_ONLY
2323 Support to boot only raw u-boot.bin images. Use this only
2324 if you need to save space.
2326 CONFIG_SPL_COMMON_INIT_DDR
2327 Set for common ddr init with serial presence detect in
2330 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2331 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2332 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2333 CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2334 CONFIG_SYS_NAND_ECCBYTES
2335 Defines the size and behavior of the NAND that SPL uses
2338 CONFIG_SYS_NAND_U_BOOT_OFFS
2339 Location in NAND to read U-Boot from
2341 CONFIG_SYS_NAND_U_BOOT_DST
2342 Location in memory to load U-Boot to
2344 CONFIG_SYS_NAND_U_BOOT_SIZE
2345 Size of image to load
2347 CONFIG_SYS_NAND_U_BOOT_START
2348 Entry point in loaded image to jump to
2350 CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2351 Define this if you need to first read the OOB and then the
2352 data. This is used, for example, on davinci platforms.
2354 CONFIG_SPL_RAM_DEVICE
2355 Support for running image already present in ram, in SPL binary
2358 Image offset to which the SPL should be padded before appending
2359 the SPL payload. By default, this is defined as
2360 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2361 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2362 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2365 Final target image containing SPL and payload. Some SPLs
2366 use an arch-specific makefile fragment instead, for
2367 example if more than one image needs to be produced.
2369 CONFIG_SPL_FIT_PRINT
2370 Printing information about a FIT image adds quite a bit of
2371 code to SPL. So this is normally disabled in SPL. Use this
2372 option to re-enable it. This will affect the output of the
2373 bootm command when booting a FIT image.
2377 Enable building of TPL globally.
2380 Image offset to which the TPL should be padded before appending
2381 the TPL payload. By default, this is defined as
2382 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2383 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2384 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2386 - Interrupt support (PPC):
2388 There are common interrupt_init() and timer_interrupt()
2389 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2390 for CPU specific initialization. interrupt_init_cpu()
2391 should set decrementer_count to appropriate value. If
2392 CPU resets decrementer automatically after interrupt
2393 (ppc4xx) it should set decrementer_count to zero.
2394 timer_interrupt() calls timer_interrupt_cpu() for CPU
2395 specific handling. If board has watchdog / status_led
2396 / other_activity_monitor it works automatically from
2397 general timer_interrupt().
2400 Board initialization settings:
2401 ------------------------------
2403 During Initialization u-boot calls a number of board specific functions
2404 to allow the preparation of board specific prerequisites, e.g. pin setup
2405 before drivers are initialized. To enable these callbacks the
2406 following configuration macros have to be defined. Currently this is
2407 architecture specific, so please check arch/your_architecture/lib/board.c
2408 typically in board_init_f() and board_init_r().
2410 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2411 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2412 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
2413 - CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2415 Configuration Settings:
2416 -----------------------
2418 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2419 Optionally it can be defined to support 64-bit memory commands.
2421 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2422 undefine this when you're short of memory.
2424 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2425 width of the commands listed in the 'help' command output.
2427 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
2428 prompt for user input.
2430 - CONFIG_SYS_CBSIZE: Buffer size for input from the Console
2432 - CONFIG_SYS_PBSIZE: Buffer size for Console output
2434 - CONFIG_SYS_MAXARGS: max. Number of arguments accepted for monitor commands
2436 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2437 the application (usually a Linux kernel) when it is
2440 - CONFIG_SYS_BAUDRATE_TABLE:
2441 List of legal baudrate settings for this board.
2443 - CONFIG_SYS_MEM_RESERVE_SECURE
2444 Only implemented for ARMv8 for now.
2445 If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2446 is substracted from total RAM and won't be reported to OS.
2447 This memory can be used as secure memory. A variable
2448 gd->arch.secure_ram is used to track the location. In systems
2449 the RAM base is not zero, or RAM is divided into banks,
2450 this variable needs to be recalcuated to get the address.
2452 - CONFIG_SYS_MEM_TOP_HIDE:
2453 If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2454 this specified memory area will get subtracted from the top
2455 (end) of RAM and won't get "touched" at all by U-Boot. By
2456 fixing up gd->ram_size the Linux kernel should gets passed
2457 the now "corrected" memory size and won't touch it either.
2458 This should work for arch/ppc and arch/powerpc. Only Linux
2459 board ports in arch/powerpc with bootwrapper support that
2460 recalculate the memory size from the SDRAM controller setup
2461 will have to get fixed in Linux additionally.
2463 This option can be used as a workaround for the 440EPx/GRx
2464 CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2467 WARNING: Please make sure that this value is a multiple of
2468 the Linux page size (normally 4k). If this is not the case,
2469 then the end address of the Linux memory will be located at a
2470 non page size aligned address and this could cause major
2473 - CONFIG_SYS_LOADS_BAUD_CHANGE:
2474 Enable temporary baudrate change while serial download
2476 - CONFIG_SYS_SDRAM_BASE:
2477 Physical start address of SDRAM. _Must_ be 0 here.
2479 - CONFIG_SYS_FLASH_BASE:
2480 Physical start address of Flash memory.
2482 - CONFIG_SYS_MONITOR_BASE:
2483 Physical start address of boot monitor code (set by
2484 make config files to be same as the text base address
2485 (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2486 CONFIG_SYS_FLASH_BASE when booting from flash.
2488 - CONFIG_SYS_MONITOR_LEN:
2489 Size of memory reserved for monitor code, used to
2490 determine _at_compile_time_ (!) if the environment is
2491 embedded within the U-Boot image, or in a separate
2494 - CONFIG_SYS_MALLOC_LEN:
2495 Size of DRAM reserved for malloc() use.
2497 - CONFIG_SYS_MALLOC_F_LEN
2498 Size of the malloc() pool for use before relocation. If
2499 this is defined, then a very simple malloc() implementation
2500 will become available before relocation. The address is just
2501 below the global data, and the stack is moved down to make
2504 This feature allocates regions with increasing addresses
2505 within the region. calloc() is supported, but realloc()
2506 is not available. free() is supported but does nothing.
2507 The memory will be freed (or in fact just forgotten) when
2508 U-Boot relocates itself.
2510 - CONFIG_SYS_MALLOC_SIMPLE
2511 Provides a simple and small malloc() and calloc() for those
2512 boards which do not use the full malloc in SPL (which is
2513 enabled with CONFIG_SYS_SPL_MALLOC_START).
2515 - CONFIG_SYS_NONCACHED_MEMORY:
2516 Size of non-cached memory area. This area of memory will be
2517 typically located right below the malloc() area and mapped
2518 uncached in the MMU. This is useful for drivers that would
2519 otherwise require a lot of explicit cache maintenance. For
2520 some drivers it's also impossible to properly maintain the
2521 cache. For example if the regions that need to be flushed
2522 are not a multiple of the cache-line size, *and* padding
2523 cannot be allocated between the regions to align them (i.e.
2524 if the HW requires a contiguous array of regions, and the
2525 size of each region is not cache-aligned), then a flush of
2526 one region may result in overwriting data that hardware has
2527 written to another region in the same cache-line. This can
2528 happen for example in network drivers where descriptors for
2529 buffers are typically smaller than the CPU cache-line (e.g.
2530 16 bytes vs. 32 or 64 bytes).
2532 Non-cached memory is only supported on 32-bit ARM at present.
2534 - CONFIG_SYS_BOOTM_LEN:
2535 Normally compressed uImages are limited to an
2536 uncompressed size of 8 MBytes. If this is not enough,
2537 you can define CONFIG_SYS_BOOTM_LEN in your board config file
2538 to adjust this setting to your needs.
2540 - CONFIG_SYS_BOOTMAPSZ:
2541 Maximum size of memory mapped by the startup code of
2542 the Linux kernel; all data that must be processed by
2543 the Linux kernel (bd_info, boot arguments, FDT blob if
2544 used) must be put below this limit, unless "bootm_low"
2545 environment variable is defined and non-zero. In such case
2546 all data for the Linux kernel must be between "bootm_low"
2547 and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
2548 variable "bootm_mapsize" will override the value of
2549 CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
2550 then the value in "bootm_size" will be used instead.
2552 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
2553 Enable initrd_high functionality. If defined then the
2554 initrd_high feature is enabled and the bootm ramdisk subcommand
2557 - CONFIG_SYS_BOOT_GET_CMDLINE:
2558 Enables allocating and saving kernel cmdline in space between
2559 "bootm_low" and "bootm_low" + BOOTMAPSZ.
2561 - CONFIG_SYS_BOOT_GET_KBD:
2562 Enables allocating and saving a kernel copy of the bd_info in
2563 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2565 - CONFIG_SYS_MAX_FLASH_BANKS:
2566 Max number of Flash memory banks
2568 - CONFIG_SYS_MAX_FLASH_SECT:
2569 Max number of sectors on a Flash chip
2571 - CONFIG_SYS_FLASH_ERASE_TOUT:
2572 Timeout for Flash erase operations (in ms)
2574 - CONFIG_SYS_FLASH_WRITE_TOUT:
2575 Timeout for Flash write operations (in ms)
2577 - CONFIG_SYS_FLASH_LOCK_TOUT
2578 Timeout for Flash set sector lock bit operation (in ms)
2580 - CONFIG_SYS_FLASH_UNLOCK_TOUT
2581 Timeout for Flash clear lock bits operation (in ms)
2583 - CONFIG_SYS_FLASH_PROTECTION
2584 If defined, hardware flash sectors protection is used
2585 instead of U-Boot software protection.
2587 - CONFIG_SYS_DIRECT_FLASH_TFTP:
2589 Enable TFTP transfers directly to flash memory;
2590 without this option such a download has to be
2591 performed in two steps: (1) download to RAM, and (2)
2592 copy from RAM to flash.
2594 The two-step approach is usually more reliable, since
2595 you can check if the download worked before you erase
2596 the flash, but in some situations (when system RAM is
2597 too limited to allow for a temporary copy of the
2598 downloaded image) this option may be very useful.
2600 - CONFIG_SYS_FLASH_CFI:
2601 Define if the flash driver uses extra elements in the
2602 common flash structure for storing flash geometry.
2604 - CONFIG_FLASH_CFI_DRIVER
2605 This option also enables the building of the cfi_flash driver
2606 in the drivers directory
2608 - CONFIG_FLASH_CFI_MTD
2609 This option enables the building of the cfi_mtd driver
2610 in the drivers directory. The driver exports CFI flash
2613 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2614 Use buffered writes to flash.
2616 - CONFIG_FLASH_SPANSION_S29WS_N
2617 s29ws-n MirrorBit flash has non-standard addresses for buffered
2620 - CONFIG_SYS_FLASH_QUIET_TEST
2621 If this option is defined, the common CFI flash doesn't
2622 print it's warning upon not recognized FLASH banks. This
2623 is useful, if some of the configured banks are only
2624 optionally available.
2626 - CONFIG_FLASH_SHOW_PROGRESS
2627 If defined (must be an integer), print out countdown
2628 digits and dots. Recommended value: 45 (9..1) for 80
2629 column displays, 15 (3..1) for 40 column displays.
2631 - CONFIG_FLASH_VERIFY
2632 If defined, the content of the flash (destination) is compared
2633 against the source after the write operation. An error message
2634 will be printed when the contents are not identical.
2635 Please note that this option is useless in nearly all cases,
2636 since such flash programming errors usually are detected earlier
2637 while unprotecting/erasing/programming. Please only enable
2638 this option if you really know what you are doing.
2640 - CONFIG_SYS_RX_ETH_BUFFER:
2641 Defines the number of Ethernet receive buffers. On some
2642 Ethernet controllers it is recommended to set this value
2643 to 8 or even higher (EEPRO100 or 405 EMAC), since all
2644 buffers can be full shortly after enabling the interface
2645 on high Ethernet traffic.
2646 Defaults to 4 if not defined.
2648 - CONFIG_ENV_MAX_ENTRIES
2650 Maximum number of entries in the hash table that is used
2651 internally to store the environment settings. The default
2652 setting is supposed to be generous and should work in most
2653 cases. This setting can be used to tune behaviour; see
2654 lib/hashtable.c for details.
2656 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2657 - CONFIG_ENV_FLAGS_LIST_STATIC
2658 Enable validation of the values given to environment variables when
2659 calling env set. Variables can be restricted to only decimal,
2660 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
2661 the variables can also be restricted to IP address or MAC address.
2663 The format of the list is:
2664 type_attribute = [s|d|x|b|i|m]
2665 access_attribute = [a|r|o|c]
2666 attributes = type_attribute[access_attribute]
2667 entry = variable_name[:attributes]
2670 The type attributes are:
2671 s - String (default)
2674 b - Boolean ([1yYtT|0nNfF])
2678 The access attributes are:
2684 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2685 Define this to a list (string) to define the ".flags"
2686 environment variable in the default or embedded environment.
2688 - CONFIG_ENV_FLAGS_LIST_STATIC
2689 Define this to a list (string) to define validation that
2690 should be done if an entry is not found in the ".flags"
2691 environment variable. To override a setting in the static
2692 list, simply add an entry for the same variable name to the
2695 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2696 regular expression. This allows multiple variables to define the same
2697 flags without explicitly listing them for each variable.
2699 The following definitions that deal with the placement and management
2700 of environment data (variable area); in general, we support the
2701 following configurations:
2703 - CONFIG_BUILD_ENVCRC:
2705 Builds up envcrc with the target environment so that external utils
2706 may easily extract it and embed it in final U-Boot images.
2708 BE CAREFUL! The first access to the environment happens quite early
2709 in U-Boot initialization (when we try to get the setting of for the
2710 console baudrate). You *MUST* have mapped your NVRAM area then, or
2713 Please note that even with NVRAM we still use a copy of the
2714 environment in RAM: we could work on NVRAM directly, but we want to
2715 keep settings there always unmodified except somebody uses "saveenv"
2716 to save the current settings.
2718 BE CAREFUL! For some special cases, the local device can not use
2719 "saveenv" command. For example, the local device will get the
2720 environment stored in a remote NOR flash by SRIO or PCIE link,
2721 but it can not erase, write this NOR flash by SRIO or PCIE interface.
2723 - CONFIG_NAND_ENV_DST
2725 Defines address in RAM to which the nand_spl code should copy the
2726 environment. If redundant environment is used, it will be copied to
2727 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2729 Please note that the environment is read-only until the monitor
2730 has been relocated to RAM and a RAM copy of the environment has been
2731 created; also, when using EEPROM you will have to use env_get_f()
2732 until then to read environment variables.
2734 The environment is protected by a CRC32 checksum. Before the monitor
2735 is relocated into RAM, as a result of a bad CRC you will be working
2736 with the compiled-in default environment - *silently*!!! [This is
2737 necessary, because the first environment variable we need is the
2738 "baudrate" setting for the console - if we have a bad CRC, we don't
2739 have any device yet where we could complain.]
2741 Note: once the monitor has been relocated, then it will complain if
2742 the default environment is used; a new CRC is computed as soon as you
2743 use the "saveenv" command to store a valid environment.
2745 - CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2746 Echo the inverted Ethernet link state to the fault LED.
2748 Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2749 also needs to be defined.
2751 - CONFIG_SYS_FAULT_MII_ADDR:
2752 MII address of the PHY to check for the Ethernet link state.
2754 - CONFIG_NS16550_MIN_FUNCTIONS:
2755 Define this if you desire to only have use of the NS16550_init
2756 and NS16550_putc functions for the serial driver located at
2757 drivers/serial/ns16550.c. This option is useful for saving
2758 space for already greatly restricted images, including but not
2759 limited to NAND_SPL configurations.
2761 - CONFIG_DISPLAY_BOARDINFO
2762 Display information about the board that U-Boot is running on
2763 when U-Boot starts up. The board function checkboard() is called
2766 - CONFIG_DISPLAY_BOARDINFO_LATE
2767 Similar to the previous option, but display this information
2768 later, once stdio is running and output goes to the LCD, if
2771 - CONFIG_BOARD_SIZE_LIMIT:
2772 Maximum size of the U-Boot image. When defined, the
2773 build system checks that the actual size does not
2776 Low Level (hardware related) configuration options:
2777 ---------------------------------------------------
2779 - CONFIG_SYS_CACHELINE_SIZE:
2780 Cache Line Size of the CPU.
2782 - CONFIG_SYS_CCSRBAR_DEFAULT:
2783 Default (power-on reset) physical address of CCSR on Freescale
2786 - CONFIG_SYS_CCSRBAR:
2787 Virtual address of CCSR. On a 32-bit build, this is typically
2788 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2790 - CONFIG_SYS_CCSRBAR_PHYS:
2791 Physical address of CCSR. CCSR can be relocated to a new
2792 physical address, if desired. In this case, this macro should
2793 be set to that address. Otherwise, it should be set to the
2794 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
2795 is typically relocated on 36-bit builds. It is recommended
2796 that this macro be defined via the _HIGH and _LOW macros:
2798 #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2799 * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2801 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2802 Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
2803 either 0 (32-bit build) or 0xF (36-bit build). This macro is
2804 used in assembly code, so it must not contain typecasts or
2805 integer size suffixes (e.g. "ULL").
2807 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
2808 Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
2809 used in assembly code, so it must not contain typecasts or
2810 integer size suffixes (e.g. "ULL").
2812 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2813 If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2814 forced to a value that ensures that CCSR is not relocated.
2817 Most IDE controllers were designed to be connected with PCI
2818 interface. Only few of them were designed for AHB interface.
2819 When software is doing ATA command and data transfer to
2820 IDE devices through IDE-AHB controller, some additional
2821 registers accessing to these kind of IDE-AHB controller
2824 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
2825 DO NOT CHANGE unless you know exactly what you're
2826 doing! (11-4) [MPC8xx systems only]
2828 - CONFIG_SYS_INIT_RAM_ADDR:
2830 Start address of memory area that can be used for
2831 initial data and stack; please note that this must be
2832 writable memory that is working WITHOUT special
2833 initialization, i. e. you CANNOT use normal RAM which
2834 will become available only after programming the
2835 memory controller and running certain initialization
2838 U-Boot uses the following memory types:
2839 - MPC8xx: IMMR (internal memory of the CPU)
2841 - CONFIG_SYS_GBL_DATA_OFFSET:
2843 Offset of the initial data structure in the memory
2844 area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2845 CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2846 data is located at the end of the available space
2847 (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2848 GENERATED_GBL_DATA_SIZE), and the initial stack is just
2849 below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2850 CONFIG_SYS_GBL_DATA_OFFSET) downward.
2853 On the MPC824X (or other systems that use the data
2854 cache for initial memory) the address chosen for
2855 CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2856 point to an otherwise UNUSED address space between
2857 the top of RAM and the start of the PCI space.
2859 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
2861 - CONFIG_SYS_OR_TIMING_SDRAM:
2864 - CONFIG_SYS_MAMR_PTA:
2865 periodic timer for refresh
2867 - FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2868 CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2869 CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2870 CONFIG_SYS_BR1_PRELIM:
2871 Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2873 - SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2874 CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2875 CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2876 Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2878 - CONFIG_PCI_ENUM_ONLY
2879 Only scan through and get the devices on the buses.
2880 Don't do any setup work, presumably because someone or
2881 something has already done it, and we don't need to do it
2882 a second time. Useful for platforms that are pre-booted
2883 by coreboot or similar.
2885 - CONFIG_PCI_INDIRECT_BRIDGE:
2886 Enable support for indirect PCI bridges.
2889 Chip has SRIO or not
2892 Board has SRIO 1 port available
2895 Board has SRIO 2 port available
2897 - CONFIG_SRIO_PCIE_BOOT_MASTER
2898 Board can support master function for Boot from SRIO and PCIE
2900 - CONFIG_SYS_SRIOn_MEM_VIRT:
2901 Virtual Address of SRIO port 'n' memory region
2903 - CONFIG_SYS_SRIOn_MEM_PHYxS:
2904 Physical Address of SRIO port 'n' memory region
2906 - CONFIG_SYS_SRIOn_MEM_SIZE:
2907 Size of SRIO port 'n' memory region
2909 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
2910 Defined to tell the NAND controller that the NAND chip is using
2912 Not all NAND drivers use this symbol.
2913 Example of drivers that use it:
2914 - drivers/mtd/nand/raw/ndfc.c
2915 - drivers/mtd/nand/raw/mxc_nand.c
2917 - CONFIG_SYS_NDFC_EBC0_CFG
2918 Sets the EBC0_CFG register for the NDFC. If not defined
2919 a default value will be used.
2922 Get DDR timing information from an I2C EEPROM. Common
2923 with pluggable memory modules such as SODIMMs
2926 I2C address of the SPD EEPROM
2928 - CONFIG_SYS_SPD_BUS_NUM
2929 If SPD EEPROM is on an I2C bus other than the first
2930 one, specify here. Note that the value must resolve
2931 to something your driver can deal with.
2933 - CONFIG_SYS_DDR_RAW_TIMING
2934 Get DDR timing information from other than SPD. Common with
2935 soldered DDR chips onboard without SPD. DDR raw timing
2936 parameters are extracted from datasheet and hard-coded into
2937 header files or board specific files.
2939 - CONFIG_FSL_DDR_INTERACTIVE
2940 Enable interactive DDR debugging. See doc/README.fsl-ddr.
2942 - CONFIG_FSL_DDR_SYNC_REFRESH
2943 Enable sync of refresh for multiple controllers.
2945 - CONFIG_FSL_DDR_BIST
2946 Enable built-in memory test for Freescale DDR controllers.
2948 - CONFIG_SYS_83XX_DDR_USES_CS0
2949 Only for 83xx systems. If specified, then DDR should
2950 be configured using CS0 and CS1 instead of CS2 and CS3.
2953 Enable RMII mode for all FECs.
2954 Note that this is a global option, we can't
2955 have one FEC in standard MII mode and another in RMII mode.
2957 - CONFIG_CRC32_VERIFY
2958 Add a verify option to the crc32 command.
2961 => crc32 -v <address> <count> <crc32>
2963 Where address/count indicate a memory area
2964 and crc32 is the correct crc32 which the
2968 Add the "loopw" memory command. This only takes effect if
2969 the memory commands are activated globally (CONFIG_CMD_MEMORY).
2971 - CONFIG_CMD_MX_CYCLIC
2972 Add the "mdc" and "mwc" memory commands. These are cyclic
2977 This command will print 4 bytes (10,11,12,13) each 500 ms.
2979 => mwc.l 100 12345678 10
2980 This command will write 12345678 to address 100 all 10 ms.
2982 This only takes effect if the memory commands are activated
2983 globally (CONFIG_CMD_MEMORY).
2985 - CONFIG_SKIP_LOWLEVEL_INIT
2986 [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
2987 low level initializations (like setting up the memory
2988 controller) are omitted and/or U-Boot does not
2989 relocate itself into RAM.
2991 Normally this variable MUST NOT be defined. The only
2992 exception is when U-Boot is loaded (to RAM) by some
2993 other boot loader or by a debugger which performs
2994 these initializations itself.
2996 - CONFIG_SKIP_LOWLEVEL_INIT_ONLY
2997 [ARM926EJ-S only] This allows just the call to lowlevel_init()
2998 to be skipped. The normal CP15 init (such as enabling the
2999 instruction cache) is still performed.
3002 Set when the currently-running compilation is for an artifact
3003 that will end up in the SPL (as opposed to the TPL or U-Boot
3004 proper). Code that needs stage-specific behavior should check
3008 Set when the currently-running compilation is for an artifact
3009 that will end up in the TPL (as opposed to the SPL or U-Boot
3010 proper). Code that needs stage-specific behavior should check
3013 - CONFIG_SYS_MPC85XX_NO_RESETVEC
3014 Only for 85xx systems. If this variable is specified, the section
3015 .resetvec is not kept and the section .bootpg is placed in the
3016 previous 4k of the .text section.
3018 - CONFIG_ARCH_MAP_SYSMEM
3019 Generally U-Boot (and in particular the md command) uses
3020 effective address. It is therefore not necessary to regard
3021 U-Boot address as virtual addresses that need to be translated
3022 to physical addresses. However, sandbox requires this, since
3023 it maintains its own little RAM buffer which contains all
3024 addressable memory. This option causes some memory accesses
3025 to be mapped through map_sysmem() / unmap_sysmem().
3027 - CONFIG_X86_RESET_VECTOR
3028 If defined, the x86 reset vector code is included. This is not
3029 needed when U-Boot is running from Coreboot.
3031 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3032 Option to disable subpage write in NAND driver
3033 driver that uses this:
3034 drivers/mtd/nand/raw/davinci_nand.c
3036 Freescale QE/FMAN Firmware Support:
3037 -----------------------------------
3039 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3040 loading of "firmware", which is encoded in the QE firmware binary format.
3041 This firmware often needs to be loaded during U-Boot booting, so macros
3042 are used to identify the storage device (NOR flash, SPI, etc) and the address
3045 - CONFIG_SYS_FMAN_FW_ADDR
3046 The address in the storage device where the FMAN microcode is located. The
3047 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3050 - CONFIG_SYS_QE_FW_ADDR
3051 The address in the storage device where the QE microcode is located. The
3052 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3055 - CONFIG_SYS_QE_FMAN_FW_LENGTH
3056 The maximum possible size of the firmware. The firmware binary format
3057 has a field that specifies the actual size of the firmware, but it
3058 might not be possible to read any part of the firmware unless some
3059 local storage is allocated to hold the entire firmware first.
3061 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
3062 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3063 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
3064 virtual address in NOR flash.
3066 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
3067 Specifies that QE/FMAN firmware is located in NAND flash.
3068 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3070 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
3071 Specifies that QE/FMAN firmware is located on the primary SD/MMC
3072 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3074 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3075 Specifies that QE/FMAN firmware is located in the remote (master)
3076 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3077 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3078 window->master inbound window->master LAW->the ucode address in
3079 master's memory space.
3081 Freescale Layerscape Management Complex Firmware Support:
3082 ---------------------------------------------------------
3083 The Freescale Layerscape Management Complex (MC) supports the loading of
3085 This firmware often needs to be loaded during U-Boot booting, so macros
3086 are used to identify the storage device (NOR flash, SPI, etc) and the address
3089 - CONFIG_FSL_MC_ENET
3090 Enable the MC driver for Layerscape SoCs.
3092 Freescale Layerscape Debug Server Support:
3093 -------------------------------------------
3094 The Freescale Layerscape Debug Server Support supports the loading of
3095 "Debug Server firmware" and triggering SP boot-rom.
3096 This firmware often needs to be loaded during U-Boot booting.
3098 - CONFIG_SYS_MC_RSV_MEM_ALIGN
3099 Define alignment of reserved memory MC requires
3104 In order to achieve reproducible builds, timestamps used in the U-Boot build
3105 process have to be set to a fixed value.
3107 This is done using the SOURCE_DATE_EPOCH environment variable.
3108 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3109 option for U-Boot or an environment variable in U-Boot.
3111 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3113 Building the Software:
3114 ======================
3116 Building U-Boot has been tested in several native build environments
3117 and in many different cross environments. Of course we cannot support
3118 all possibly existing versions of cross development tools in all
3119 (potentially obsolete) versions. In case of tool chain problems we
3120 recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3121 which is extensively used to build and test U-Boot.
3123 If you are not using a native environment, it is assumed that you
3124 have GNU cross compiling tools available in your path. In this case,
3125 you must set the environment variable CROSS_COMPILE in your shell.
3126 Note that no changes to the Makefile or any other source files are
3127 necessary. For example using the ELDK on a 4xx CPU, please enter:
3129 $ CROSS_COMPILE=ppc_4xx-
3130 $ export CROSS_COMPILE
3132 U-Boot is intended to be simple to build. After installing the
3133 sources you must configure U-Boot for one specific board type. This
3138 where "NAME_defconfig" is the name of one of the existing configu-
3139 rations; see configs/*_defconfig for supported names.
3141 Note: for some boards special configuration names may exist; check if
3142 additional information is available from the board vendor; for
3143 instance, the TQM823L systems are available without (standard)
3144 or with LCD support. You can select such additional "features"
3145 when choosing the configuration, i. e.
3147 make TQM823L_defconfig
3148 - will configure for a plain TQM823L, i. e. no LCD support
3150 make TQM823L_LCD_defconfig
3151 - will configure for a TQM823L with U-Boot console on LCD
3156 Finally, type "make all", and you should get some working U-Boot
3157 images ready for download to / installation on your system:
3159 - "u-boot.bin" is a raw binary image
3160 - "u-boot" is an image in ELF binary format
3161 - "u-boot.srec" is in Motorola S-Record format
3163 By default the build is performed locally and the objects are saved
3164 in the source directory. One of the two methods can be used to change
3165 this behavior and build U-Boot to some external directory:
3167 1. Add O= to the make command line invocations:
3169 make O=/tmp/build distclean
3170 make O=/tmp/build NAME_defconfig
3171 make O=/tmp/build all
3173 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
3175 export KBUILD_OUTPUT=/tmp/build
3180 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3183 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3184 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3185 For example to treat all compiler warnings as errors:
3187 make KCFLAGS=-Werror
3189 Please be aware that the Makefiles assume you are using GNU make, so
3190 for instance on NetBSD you might need to use "gmake" instead of
3194 If the system board that you have is not listed, then you will need
3195 to port U-Boot to your hardware platform. To do this, follow these
3198 1. Create a new directory to hold your board specific code. Add any
3199 files you need. In your board directory, you will need at least
3200 the "Makefile" and a "<board>.c".
3201 2. Create a new configuration file "include/configs/<board>.h" for
3203 3. If you're porting U-Boot to a new CPU, then also create a new
3204 directory to hold your CPU specific code. Add any files you need.
3205 4. Run "make <board>_defconfig" with your new name.
3206 5. Type "make", and you should get a working "u-boot.srec" file
3207 to be installed on your target system.
3208 6. Debug and solve any problems that might arise.
3209 [Of course, this last step is much harder than it sounds.]
3212 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3213 ==============================================================
3215 If you have modified U-Boot sources (for instance added a new board
3216 or support for new devices, a new CPU, etc.) you are expected to
3217 provide feedback to the other developers. The feedback normally takes
3218 the form of a "patch", i.e. a context diff against a certain (latest
3219 official or latest in the git repository) version of U-Boot sources.
3221 But before you submit such a patch, please verify that your modifi-
3222 cation did not break existing code. At least make sure that *ALL* of
3223 the supported boards compile WITHOUT ANY compiler warnings. To do so,
3224 just run the buildman script (tools/buildman/buildman), which will
3225 configure and build U-Boot for ALL supported system. Be warned, this
3226 will take a while. Please see the buildman README, or run 'buildman -H'
3230 See also "U-Boot Porting Guide" below.
3233 Monitor Commands - Overview:
3234 ============================
3236 go - start application at address 'addr'
3237 run - run commands in an environment variable
3238 bootm - boot application image from memory
3239 bootp - boot image via network using BootP/TFTP protocol
3240 bootz - boot zImage from memory
3241 tftpboot- boot image via network using TFTP protocol
3242 and env variables "ipaddr" and "serverip"
3243 (and eventually "gatewayip")
3244 tftpput - upload a file via network using TFTP protocol
3245 rarpboot- boot image via network using RARP/TFTP protocol
3246 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
3247 loads - load S-Record file over serial line
3248 loadb - load binary file over serial line (kermit mode)
3250 mm - memory modify (auto-incrementing)
3251 nm - memory modify (constant address)
3252 mw - memory write (fill)
3254 cmp - memory compare
3255 crc32 - checksum calculation
3256 i2c - I2C sub-system
3257 sspi - SPI utility commands
3258 base - print or set address offset
3259 printenv- print environment variables
3260 setenv - set environment variables
3261 saveenv - save environment variables to persistent storage
3262 protect - enable or disable FLASH write protection
3263 erase - erase FLASH memory
3264 flinfo - print FLASH memory information
3265 nand - NAND memory operations (see doc/README.nand)
3266 bdinfo - print Board Info structure
3267 iminfo - print header information for application image
3268 coninfo - print console devices and informations
3269 ide - IDE sub-system
3270 loop - infinite loop on address range
3271 loopw - infinite write loop on address range
3272 mtest - simple RAM test
3273 icache - enable or disable instruction cache
3274 dcache - enable or disable data cache
3275 reset - Perform RESET of the CPU
3276 echo - echo args to console
3277 version - print monitor version
3278 help - print online help
3279 ? - alias for 'help'
3282 Monitor Commands - Detailed Description:
3283 ========================================
3287 For now: just type "help <command>".
3290 Environment Variables:
3291 ======================
3293 U-Boot supports user configuration using Environment Variables which
3294 can be made persistent by saving to Flash memory.
3296 Environment Variables are set using "setenv", printed using
3297 "printenv", and saved to Flash using "saveenv". Using "setenv"
3298 without a value can be used to delete a variable from the
3299 environment. As long as you don't save the environment you are
3300 working with an in-memory copy. In case the Flash area containing the
3301 environment is erased by accident, a default environment is provided.
3303 Some configuration options can be set using Environment Variables.
3305 List of environment variables (most likely not complete):
3307 baudrate - see CONFIG_BAUDRATE
3309 bootdelay - see CONFIG_BOOTDELAY
3311 bootcmd - see CONFIG_BOOTCOMMAND
3313 bootargs - Boot arguments when booting an RTOS image
3315 bootfile - Name of the image to load with TFTP
3317 bootm_low - Memory range available for image processing in the bootm
3318 command can be restricted. This variable is given as
3319 a hexadecimal number and defines lowest address allowed
3320 for use by the bootm command. See also "bootm_size"
3321 environment variable. Address defined by "bootm_low" is
3322 also the base of the initial memory mapping for the Linux
3323 kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3326 bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3327 This variable is given as a hexadecimal number and it
3328 defines the size of the memory region starting at base
3329 address bootm_low that is accessible by the Linux kernel
3330 during early boot. If unset, CONFIG_SYS_BOOTMAPSZ is used
3331 as the default value if it is defined, and bootm_size is
3334 bootm_size - Memory range available for image processing in the bootm
3335 command can be restricted. This variable is given as
3336 a hexadecimal number and defines the size of the region
3337 allowed for use by the bootm command. See also "bootm_low"
3338 environment variable.
3340 bootstopkeysha256, bootdelaykey, bootstopkey - See README.autoboot
3342 updatefile - Location of the software update file on a TFTP server, used
3343 by the automatic software update feature. Please refer to
3344 documentation in doc/README.update for more details.
3346 autoload - if set to "no" (any string beginning with 'n'),
3347 "bootp" will just load perform a lookup of the
3348 configuration from the BOOTP server, but not try to
3349 load any image using TFTP
3351 autostart - if set to "yes", an image loaded using the "bootp",
3352 "rarpboot", "tftpboot" or "diskboot" commands will
3353 be automatically started (by internally calling
3356 If set to "no", a standalone image passed to the
3357 "bootm" command will be copied to the load address
3358 (and eventually uncompressed), but NOT be started.
3359 This can be used to load and uncompress arbitrary
3362 fdt_high - if set this restricts the maximum address that the
3363 flattened device tree will be copied into upon boot.
3364 For example, if you have a system with 1 GB memory
3365 at physical address 0x10000000, while Linux kernel
3366 only recognizes the first 704 MB as low memory, you
3367 may need to set fdt_high as 0x3C000000 to have the
3368 device tree blob be copied to the maximum address
3369 of the 704 MB low memory, so that Linux kernel can
3370 access it during the boot procedure.
3372 If this is set to the special value 0xFFFFFFFF then
3373 the fdt will not be copied at all on boot. For this
3374 to work it must reside in writable memory, have
3375 sufficient padding on the end of it for u-boot to
3376 add the information it needs into it, and the memory
3377 must be accessible by the kernel.
3379 fdtcontroladdr- if set this is the address of the control flattened
3380 device tree used by U-Boot when CONFIG_OF_CONTROL is
3383 i2cfast - (PPC405GP|PPC405EP only)
3384 if set to 'y' configures Linux I2C driver for fast
3385 mode (400kHZ). This environment variable is used in
3386 initialization code. So, for changes to be effective
3387 it must be saved and board must be reset.
3389 initrd_high - restrict positioning of initrd images:
3390 If this variable is not set, initrd images will be
3391 copied to the highest possible address in RAM; this
3392 is usually what you want since it allows for
3393 maximum initrd size. If for some reason you want to
3394 make sure that the initrd image is loaded below the
3395 CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3396 variable to a value of "no" or "off" or "0".
3397 Alternatively, you can set it to a maximum upper
3398 address to use (U-Boot will still check that it
3399 does not overwrite the U-Boot stack and data).
3401 For instance, when you have a system with 16 MB
3402 RAM, and want to reserve 4 MB from use by Linux,
3403 you can do this by adding "mem=12M" to the value of
3404 the "bootargs" variable. However, now you must make
3405 sure that the initrd image is placed in the first
3406 12 MB as well - this can be done with
3408 setenv initrd_high 00c00000
3410 If you set initrd_high to 0xFFFFFFFF, this is an
3411 indication to U-Boot that all addresses are legal
3412 for the Linux kernel, including addresses in flash
3413 memory. In this case U-Boot will NOT COPY the
3414 ramdisk at all. This may be useful to reduce the
3415 boot time on your system, but requires that this
3416 feature is supported by your Linux kernel.
3418 ipaddr - IP address; needed for tftpboot command
3420 loadaddr - Default load address for commands like "bootp",
3421 "rarpboot", "tftpboot", "loadb" or "diskboot"
3423 loads_echo - see CONFIG_LOADS_ECHO
3425 serverip - TFTP server IP address; needed for tftpboot command
3427 bootretry - see CONFIG_BOOT_RETRY_TIME
3429 bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR
3431 bootstopkey - see CONFIG_AUTOBOOT_STOP_STR
3433 ethprime - controls which interface is used first.
3435 ethact - controls which interface is currently active.
3436 For example you can do the following
3438 => setenv ethact FEC
3439 => ping 192.168.0.1 # traffic sent on FEC
3440 => setenv ethact SCC
3441 => ping 10.0.0.1 # traffic sent on SCC
3443 ethrotate - When set to "no" U-Boot does not go through all
3444 available network interfaces.
3445 It just stays at the currently selected interface.
3447 netretry - When set to "no" each network operation will
3448 either succeed or fail without retrying.
3449 When set to "once" the network operation will
3450 fail when all the available network interfaces
3451 are tried once without success.
3452 Useful on scripts which control the retry operation
3455 npe_ucode - set load address for the NPE microcode
3457 silent_linux - If set then Linux will be told to boot silently, by
3458 changing the console to be empty. If "yes" it will be
3459 made silent. If "no" it will not be made silent. If
3460 unset, then it will be made silent if the U-Boot console
3463 tftpsrcp - If this is set, the value is used for TFTP's
3466 tftpdstp - If this is set, the value is used for TFTP's UDP
3467 destination port instead of the Well Know Port 69.
3469 tftpblocksize - Block size to use for TFTP transfers; if not set,
3470 we use the TFTP server's default block size
3472 tftptimeout - Retransmission timeout for TFTP packets (in milli-
3473 seconds, minimum value is 1000 = 1 second). Defines
3474 when a packet is considered to be lost so it has to
3475 be retransmitted. The default is 5000 = 5 seconds.
3476 Lowering this value may make downloads succeed
3477 faster in networks with high packet loss rates or
3478 with unreliable TFTP servers.
3480 tftptimeoutcountmax - maximum count of TFTP timeouts (no
3481 unit, minimum value = 0). Defines how many timeouts
3482 can happen during a single file transfer before that
3483 transfer is aborted. The default is 10, and 0 means
3484 'no timeouts allowed'. Increasing this value may help
3485 downloads succeed with high packet loss rates, or with
3486 unreliable TFTP servers or client hardware.
3488 vlan - When set to a value < 4095 the traffic over
3489 Ethernet is encapsulated/received over 802.1q
3492 bootpretryperiod - Period during which BOOTP/DHCP sends retries.
3493 Unsigned value, in milliseconds. If not set, the period will
3494 be either the default (28000), or a value based on
3495 CONFIG_NET_RETRY_COUNT, if defined. This value has
3496 precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3498 The following image location variables contain the location of images
3499 used in booting. The "Image" column gives the role of the image and is
3500 not an environment variable name. The other columns are environment
3501 variable names. "File Name" gives the name of the file on a TFTP
3502 server, "RAM Address" gives the location in RAM the image will be
3503 loaded to, and "Flash Location" gives the image's address in NOR
3504 flash or offset in NAND flash.
3506 *Note* - these variables don't have to be defined for all boards, some
3507 boards currently use other variables for these purposes, and some
3508 boards use these variables for other purposes.
3510 Image File Name RAM Address Flash Location
3511 ----- --------- ----------- --------------
3512 u-boot u-boot u-boot_addr_r u-boot_addr
3513 Linux kernel bootfile kernel_addr_r kernel_addr
3514 device tree blob fdtfile fdt_addr_r fdt_addr
3515 ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr
3517 The following environment variables may be used and automatically
3518 updated by the network boot commands ("bootp" and "rarpboot"),
3519 depending the information provided by your boot server:
3521 bootfile - see above
3522 dnsip - IP address of your Domain Name Server
3523 dnsip2 - IP address of your secondary Domain Name Server
3524 gatewayip - IP address of the Gateway (Router) to use
3525 hostname - Target hostname
3527 netmask - Subnet Mask
3528 rootpath - Pathname of the root filesystem on the NFS server
3529 serverip - see above
3532 There are two special Environment Variables:
3534 serial# - contains hardware identification information such
3535 as type string and/or serial number
3536 ethaddr - Ethernet address
3538 These variables can be set only once (usually during manufacturing of
3539 the board). U-Boot refuses to delete or overwrite these variables
3540 once they have been set once.
3543 Further special Environment Variables:
3545 ver - Contains the U-Boot version string as printed
3546 with the "version" command. This variable is
3547 readonly (see CONFIG_VERSION_VARIABLE).
3550 Please note that changes to some configuration parameters may take
3551 only effect after the next boot (yes, that's just like Windoze :-).
3554 Callback functions for environment variables:
3555 ---------------------------------------------
3557 For some environment variables, the behavior of u-boot needs to change
3558 when their values are changed. This functionality allows functions to
3559 be associated with arbitrary variables. On creation, overwrite, or
3560 deletion, the callback will provide the opportunity for some side
3561 effect to happen or for the change to be rejected.
3563 The callbacks are named and associated with a function using the
3564 U_BOOT_ENV_CALLBACK macro in your board or driver code.
3566 These callbacks are associated with variables in one of two ways. The
3567 static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3568 in the board configuration to a string that defines a list of
3569 associations. The list must be in the following format:
3571 entry = variable_name[:callback_name]
3574 If the callback name is not specified, then the callback is deleted.
3575 Spaces are also allowed anywhere in the list.
3577 Callbacks can also be associated by defining the ".callbacks" variable
3578 with the same list format above. Any association in ".callbacks" will
3579 override any association in the static list. You can define
3580 CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3581 ".callbacks" environment variable in the default or embedded environment.
3583 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3584 regular expression. This allows multiple variables to be connected to
3585 the same callback without explicitly listing them all out.
3587 The signature of the callback functions is:
3589 int callback(const char *name, const char *value, enum env_op op, int flags)
3591 * name - changed environment variable
3592 * value - new value of the environment variable
3593 * op - operation (create, overwrite, or delete)
3594 * flags - attributes of the environment variable change, see flags H_* in
3597 The return value is 0 if the variable change is accepted and 1 otherwise.
3599 Command Line Parsing:
3600 =====================
3602 There are two different command line parsers available with U-Boot:
3603 the old "simple" one, and the much more powerful "hush" shell:
3605 Old, simple command line parser:
3606 --------------------------------
3608 - supports environment variables (through setenv / saveenv commands)
3609 - several commands on one line, separated by ';'
3610 - variable substitution using "... ${name} ..." syntax
3611 - special characters ('$', ';') can be escaped by prefixing with '\',
3613 setenv bootcmd bootm \${address}
3614 - You can also escape text by enclosing in single apostrophes, for example:
3615 setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3620 - similar to Bourne shell, with control structures like
3621 if...then...else...fi, for...do...done; while...do...done,
3622 until...do...done, ...
3623 - supports environment ("global") variables (through setenv / saveenv
3624 commands) and local shell variables (through standard shell syntax
3625 "name=value"); only environment variables can be used with "run"
3631 (1) If a command line (or an environment variable executed by a "run"
3632 command) contains several commands separated by semicolon, and
3633 one of these commands fails, then the remaining commands will be
3636 (2) If you execute several variables with one call to run (i. e.
3637 calling run with a list of variables as arguments), any failing
3638 command will cause "run" to terminate, i. e. the remaining
3639 variables are not executed.
3641 Note for Redundant Ethernet Interfaces:
3642 =======================================
3644 Some boards come with redundant Ethernet interfaces; U-Boot supports
3645 such configurations and is capable of automatic selection of a
3646 "working" interface when needed. MAC assignment works as follows:
3648 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3649 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3650 "eth1addr" (=>eth1), "eth2addr", ...
3652 If the network interface stores some valid MAC address (for instance
3653 in SROM), this is used as default address if there is NO correspon-
3654 ding setting in the environment; if the corresponding environment
3655 variable is set, this overrides the settings in the card; that means:
3657 o If the SROM has a valid MAC address, and there is no address in the
3658 environment, the SROM's address is used.
3660 o If there is no valid address in the SROM, and a definition in the
3661 environment exists, then the value from the environment variable is
3664 o If both the SROM and the environment contain a MAC address, and
3665 both addresses are the same, this MAC address is used.
3667 o If both the SROM and the environment contain a MAC address, and the
3668 addresses differ, the value from the environment is used and a
3671 o If neither SROM nor the environment contain a MAC address, an error
3672 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3673 a random, locally-assigned MAC is used.
3675 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3676 will be programmed into hardware as part of the initialization process. This
3677 may be skipped by setting the appropriate 'ethmacskip' environment variable.
3678 The naming convention is as follows:
3679 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3684 U-Boot is capable of booting (and performing other auxiliary operations on)
3685 images in two formats:
3687 New uImage format (FIT)
3688 -----------------------
3690 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3691 to Flattened Device Tree). It allows the use of images with multiple
3692 components (several kernels, ramdisks, etc.), with contents protected by
3693 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3699 Old image format is based on binary files which can be basically anything,
3700 preceded by a special header; see the definitions in include/image.h for
3701 details; basically, the header defines the following image properties:
3703 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3704 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3705 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3706 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3708 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3709 IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3710 Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3711 * Compression Type (uncompressed, gzip, bzip2)
3717 The header is marked by a special Magic Number, and both the header
3718 and the data portions of the image are secured against corruption by
3725 Although U-Boot should support any OS or standalone application
3726 easily, the main focus has always been on Linux during the design of
3729 U-Boot includes many features that so far have been part of some
3730 special "boot loader" code within the Linux kernel. Also, any
3731 "initrd" images to be used are no longer part of one big Linux image;
3732 instead, kernel and "initrd" are separate images. This implementation
3733 serves several purposes:
3735 - the same features can be used for other OS or standalone
3736 applications (for instance: using compressed images to reduce the
3737 Flash memory footprint)
3739 - it becomes much easier to port new Linux kernel versions because
3740 lots of low-level, hardware dependent stuff are done by U-Boot
3742 - the same Linux kernel image can now be used with different "initrd"
3743 images; of course this also means that different kernel images can
3744 be run with the same "initrd". This makes testing easier (you don't
3745 have to build a new "zImage.initrd" Linux image when you just
3746 change a file in your "initrd"). Also, a field-upgrade of the
3747 software is easier now.
3753 Porting Linux to U-Boot based systems:
3754 ---------------------------------------
3756 U-Boot cannot save you from doing all the necessary modifications to
3757 configure the Linux device drivers for use with your target hardware
3758 (no, we don't intend to provide a full virtual machine interface to
3761 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3763 Just make sure your machine specific header file (for instance
3764 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3765 Information structure as we define in include/asm-<arch>/u-boot.h,
3766 and make sure that your definition of IMAP_ADDR uses the same value
3767 as your U-Boot configuration in CONFIG_SYS_IMMR.
3769 Note that U-Boot now has a driver model, a unified model for drivers.
3770 If you are adding a new driver, plumb it into driver model. If there
3771 is no uclass available, you are encouraged to create one. See
3775 Configuring the Linux kernel:
3776 -----------------------------
3778 No specific requirements for U-Boot. Make sure you have some root
3779 device (initial ramdisk, NFS) for your target system.
3782 Building a Linux Image:
3783 -----------------------
3785 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3786 not used. If you use recent kernel source, a new build target
3787 "uImage" will exist which automatically builds an image usable by
3788 U-Boot. Most older kernels also have support for a "pImage" target,
3789 which was introduced for our predecessor project PPCBoot and uses a
3790 100% compatible format.
3794 make TQM850L_defconfig
3799 The "uImage" build target uses a special tool (in 'tools/mkimage') to
3800 encapsulate a compressed Linux kernel image with header information,
3801 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3803 * build a standard "vmlinux" kernel image (in ELF binary format):
3805 * convert the kernel into a raw binary image:
3807 ${CROSS_COMPILE}-objcopy -O binary \
3808 -R .note -R .comment \
3809 -S vmlinux linux.bin
3811 * compress the binary image:
3815 * package compressed binary image for U-Boot:
3817 mkimage -A ppc -O linux -T kernel -C gzip \
3818 -a 0 -e 0 -n "Linux Kernel Image" \
3819 -d linux.bin.gz uImage
3822 The "mkimage" tool can also be used to create ramdisk images for use
3823 with U-Boot, either separated from the Linux kernel image, or
3824 combined into one file. "mkimage" encapsulates the images with a 64
3825 byte header containing information about target architecture,
3826 operating system, image type, compression method, entry points, time
3827 stamp, CRC32 checksums, etc.
3829 "mkimage" can be called in two ways: to verify existing images and
3830 print the header information, or to build new images.
3832 In the first form (with "-l" option) mkimage lists the information
3833 contained in the header of an existing U-Boot image; this includes
3834 checksum verification:
3836 tools/mkimage -l image
3837 -l ==> list image header information
3839 The second form (with "-d" option) is used to build a U-Boot image
3840 from a "data file" which is used as image payload:
3842 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3843 -n name -d data_file image
3844 -A ==> set architecture to 'arch'
3845 -O ==> set operating system to 'os'
3846 -T ==> set image type to 'type'
3847 -C ==> set compression type 'comp'
3848 -a ==> set load address to 'addr' (hex)
3849 -e ==> set entry point to 'ep' (hex)
3850 -n ==> set image name to 'name'
3851 -d ==> use image data from 'datafile'
3853 Right now, all Linux kernels for PowerPC systems use the same load
3854 address (0x00000000), but the entry point address depends on the
3857 - 2.2.x kernels have the entry point at 0x0000000C,
3858 - 2.3.x and later kernels have the entry point at 0x00000000.
3860 So a typical call to build a U-Boot image would read:
3862 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3863 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3864 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3865 > examples/uImage.TQM850L
3866 Image Name: 2.4.4 kernel for TQM850L
3867 Created: Wed Jul 19 02:34:59 2000
3868 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3869 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3870 Load Address: 0x00000000
3871 Entry Point: 0x00000000
3873 To verify the contents of the image (or check for corruption):
3875 -> tools/mkimage -l examples/uImage.TQM850L
3876 Image Name: 2.4.4 kernel for TQM850L
3877 Created: Wed Jul 19 02:34:59 2000
3878 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3879 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3880 Load Address: 0x00000000
3881 Entry Point: 0x00000000
3883 NOTE: for embedded systems where boot time is critical you can trade
3884 speed for memory and install an UNCOMPRESSED image instead: this
3885 needs more space in Flash, but boots much faster since it does not
3886 need to be uncompressed:
3888 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3889 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3890 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3891 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3892 > examples/uImage.TQM850L-uncompressed
3893 Image Name: 2.4.4 kernel for TQM850L
3894 Created: Wed Jul 19 02:34:59 2000
3895 Image Type: PowerPC Linux Kernel Image (uncompressed)
3896 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
3897 Load Address: 0x00000000
3898 Entry Point: 0x00000000
3901 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3902 when your kernel is intended to use an initial ramdisk:
3904 -> tools/mkimage -n 'Simple Ramdisk Image' \
3905 > -A ppc -O linux -T ramdisk -C gzip \
3906 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3907 Image Name: Simple Ramdisk Image
3908 Created: Wed Jan 12 14:01:50 2000
3909 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3910 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
3911 Load Address: 0x00000000
3912 Entry Point: 0x00000000
3914 The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
3915 option performs the converse operation of the mkimage's second form (the "-d"
3916 option). Given an image built by mkimage, the dumpimage extracts a "data file"
3919 tools/dumpimage -i image -T type -p position data_file
3920 -i ==> extract from the 'image' a specific 'data_file'
3921 -T ==> set image type to 'type'
3922 -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
3925 Installing a Linux Image:
3926 -------------------------
3928 To downloading a U-Boot image over the serial (console) interface,
3929 you must convert the image to S-Record format:
3931 objcopy -I binary -O srec examples/image examples/image.srec
3933 The 'objcopy' does not understand the information in the U-Boot
3934 image header, so the resulting S-Record file will be relative to
3935 address 0x00000000. To load it to a given address, you need to
3936 specify the target address as 'offset' parameter with the 'loads'
3939 Example: install the image to address 0x40100000 (which on the
3940 TQM8xxL is in the first Flash bank):
3942 => erase 40100000 401FFFFF
3948 ## Ready for S-Record download ...
3949 ~>examples/image.srec
3950 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3952 15989 15990 15991 15992
3953 [file transfer complete]
3955 ## Start Addr = 0x00000000
3958 You can check the success of the download using the 'iminfo' command;
3959 this includes a checksum verification so you can be sure no data
3960 corruption happened:
3964 ## Checking Image at 40100000 ...
3965 Image Name: 2.2.13 for initrd on TQM850L
3966 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3967 Data Size: 335725 Bytes = 327 kB = 0 MB
3968 Load Address: 00000000
3969 Entry Point: 0000000c
3970 Verifying Checksum ... OK
3976 The "bootm" command is used to boot an application that is stored in
3977 memory (RAM or Flash). In case of a Linux kernel image, the contents
3978 of the "bootargs" environment variable is passed to the kernel as
3979 parameters. You can check and modify this variable using the
3980 "printenv" and "setenv" commands:
3983 => printenv bootargs
3984 bootargs=root=/dev/ram
3986 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3988 => printenv bootargs
3989 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3992 ## Booting Linux kernel at 40020000 ...
3993 Image Name: 2.2.13 for NFS on TQM850L
3994 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3995 Data Size: 381681 Bytes = 372 kB = 0 MB
3996 Load Address: 00000000
3997 Entry Point: 0000000c
3998 Verifying Checksum ... OK
3999 Uncompressing Kernel Image ... OK
4000 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
4001 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4002 time_init: decrementer frequency = 187500000/60
4003 Calibrating delay loop... 49.77 BogoMIPS
4004 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4007 If you want to boot a Linux kernel with initial RAM disk, you pass
4008 the memory addresses of both the kernel and the initrd image (PPBCOOT
4009 format!) to the "bootm" command:
4011 => imi 40100000 40200000
4013 ## Checking Image at 40100000 ...
4014 Image Name: 2.2.13 for initrd on TQM850L
4015 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4016 Data Size: 335725 Bytes = 327 kB = 0 MB
4017 Load Address: 00000000
4018 Entry Point: 0000000c
4019 Verifying Checksum ... OK
4021 ## Checking Image at 40200000 ...
4022 Image Name: Simple Ramdisk Image
4023 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
4024 Data Size: 566530 Bytes = 553 kB = 0 MB
4025 Load Address: 00000000
4026 Entry Point: 00000000
4027 Verifying Checksum ... OK
4029 => bootm 40100000 40200000
4030 ## Booting Linux kernel at 40100000 ...
4031 Image Name: 2.2.13 for initrd on TQM850L
4032 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4033 Data Size: 335725 Bytes = 327 kB = 0 MB
4034 Load Address: 00000000
4035 Entry Point: 0000000c
4036 Verifying Checksum ... OK
4037 Uncompressing Kernel Image ... OK
4038 ## Loading RAMDisk Image at 40200000 ...
4039 Image Name: Simple Ramdisk Image
4040 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
4041 Data Size: 566530 Bytes = 553 kB = 0 MB
4042 Load Address: 00000000
4043 Entry Point: 00000000
4044 Verifying Checksum ... OK
4045 Loading Ramdisk ... OK
4046 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
4047 Boot arguments: root=/dev/ram
4048 time_init: decrementer frequency = 187500000/60
4049 Calibrating delay loop... 49.77 BogoMIPS
4051 RAMDISK: Compressed image found at block 0
4052 VFS: Mounted root (ext2 filesystem).
4056 Boot Linux and pass a flat device tree:
4059 First, U-Boot must be compiled with the appropriate defines. See the section
4060 titled "Linux Kernel Interface" above for a more in depth explanation. The
4061 following is an example of how to start a kernel and pass an updated
4067 oft=oftrees/mpc8540ads.dtb
4068 => tftp $oftaddr $oft
4069 Speed: 1000, full duplex
4071 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4072 Filename 'oftrees/mpc8540ads.dtb'.
4073 Load address: 0x300000
4076 Bytes transferred = 4106 (100a hex)
4077 => tftp $loadaddr $bootfile
4078 Speed: 1000, full duplex
4080 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4082 Load address: 0x200000
4083 Loading:############
4085 Bytes transferred = 1029407 (fb51f hex)
4090 => bootm $loadaddr - $oftaddr
4091 ## Booting image at 00200000 ...
4092 Image Name: Linux-2.6.17-dirty
4093 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4094 Data Size: 1029343 Bytes = 1005.2 kB
4095 Load Address: 00000000
4096 Entry Point: 00000000
4097 Verifying Checksum ... OK
4098 Uncompressing Kernel Image ... OK
4099 Booting using flat device tree at 0x300000
4100 Using MPC85xx ADS machine description
4101 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4105 More About U-Boot Image Types:
4106 ------------------------------
4108 U-Boot supports the following image types:
4110 "Standalone Programs" are directly runnable in the environment
4111 provided by U-Boot; it is expected that (if they behave
4112 well) you can continue to work in U-Boot after return from
4113 the Standalone Program.
4114 "OS Kernel Images" are usually images of some Embedded OS which
4115 will take over control completely. Usually these programs
4116 will install their own set of exception handlers, device
4117 drivers, set up the MMU, etc. - this means, that you cannot
4118 expect to re-enter U-Boot except by resetting the CPU.
4119 "RAMDisk Images" are more or less just data blocks, and their
4120 parameters (address, size) are passed to an OS kernel that is
4122 "Multi-File Images" contain several images, typically an OS
4123 (Linux) kernel image and one or more data images like
4124 RAMDisks. This construct is useful for instance when you want
4125 to boot over the network using BOOTP etc., where the boot
4126 server provides just a single image file, but you want to get
4127 for instance an OS kernel and a RAMDisk image.
4129 "Multi-File Images" start with a list of image sizes, each
4130 image size (in bytes) specified by an "uint32_t" in network
4131 byte order. This list is terminated by an "(uint32_t)0".
4132 Immediately after the terminating 0 follow the images, one by
4133 one, all aligned on "uint32_t" boundaries (size rounded up to
4134 a multiple of 4 bytes).
4136 "Firmware Images" are binary images containing firmware (like
4137 U-Boot or FPGA images) which usually will be programmed to
4140 "Script files" are command sequences that will be executed by
4141 U-Boot's command interpreter; this feature is especially
4142 useful when you configure U-Boot to use a real shell (hush)
4143 as command interpreter.
4145 Booting the Linux zImage:
4146 -------------------------
4148 On some platforms, it's possible to boot Linux zImage. This is done
4149 using the "bootz" command. The syntax of "bootz" command is the same
4150 as the syntax of "bootm" command.
4152 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4153 kernel with raw initrd images. The syntax is slightly different, the
4154 address of the initrd must be augmented by it's size, in the following
4155 format: "<initrd addres>:<initrd size>".
4161 One of the features of U-Boot is that you can dynamically load and
4162 run "standalone" applications, which can use some resources of
4163 U-Boot like console I/O functions or interrupt services.
4165 Two simple examples are included with the sources:
4170 'examples/hello_world.c' contains a small "Hello World" Demo
4171 application; it is automatically compiled when you build U-Boot.
4172 It's configured to run at address 0x00040004, so you can play with it
4176 ## Ready for S-Record download ...
4177 ~>examples/hello_world.srec
4178 1 2 3 4 5 6 7 8 9 10 11 ...
4179 [file transfer complete]
4181 ## Start Addr = 0x00040004
4183 => go 40004 Hello World! This is a test.
4184 ## Starting application at 0x00040004 ...
4195 Hit any key to exit ...
4197 ## Application terminated, rc = 0x0
4199 Another example, which demonstrates how to register a CPM interrupt
4200 handler with the U-Boot code, can be found in 'examples/timer.c'.
4201 Here, a CPM timer is set up to generate an interrupt every second.
4202 The interrupt service routine is trivial, just printing a '.'
4203 character, but this is just a demo program. The application can be
4204 controlled by the following keys:
4206 ? - print current values og the CPM Timer registers
4207 b - enable interrupts and start timer
4208 e - stop timer and disable interrupts
4209 q - quit application
4212 ## Ready for S-Record download ...
4213 ~>examples/timer.srec
4214 1 2 3 4 5 6 7 8 9 10 11 ...
4215 [file transfer complete]
4217 ## Start Addr = 0x00040004
4220 ## Starting application at 0x00040004 ...
4223 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4226 [q, b, e, ?] Set interval 1000000 us
4229 [q, b, e, ?] ........
4230 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4233 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4236 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4239 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4241 [q, b, e, ?] ...Stopping timer
4243 [q, b, e, ?] ## Application terminated, rc = 0x0
4249 Over time, many people have reported problems when trying to use the
4250 "minicom" terminal emulation program for serial download. I (wd)
4251 consider minicom to be broken, and recommend not to use it. Under
4252 Unix, I recommend to use C-Kermit for general purpose use (and
4253 especially for kermit binary protocol download ("loadb" command), and
4254 use "cu" for S-Record download ("loads" command). See
4255 http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4256 for help with kermit.
4259 Nevertheless, if you absolutely want to use it try adding this
4260 configuration to your "File transfer protocols" section:
4262 Name Program Name U/D FullScr IO-Red. Multi
4263 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
4264 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
4270 Starting at version 0.9.2, U-Boot supports NetBSD both as host
4271 (build U-Boot) and target system (boots NetBSD/mpc8xx).
4273 Building requires a cross environment; it is known to work on
4274 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4275 need gmake since the Makefiles are not compatible with BSD make).
4276 Note that the cross-powerpc package does not install include files;
4277 attempting to build U-Boot will fail because <machine/ansi.h> is
4278 missing. This file has to be installed and patched manually:
4280 # cd /usr/pkg/cross/powerpc-netbsd/include
4282 # ln -s powerpc machine
4283 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4284 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
4286 Native builds *don't* work due to incompatibilities between native
4287 and U-Boot include files.
4289 Booting assumes that (the first part of) the image booted is a
4290 stage-2 loader which in turn loads and then invokes the kernel
4291 proper. Loader sources will eventually appear in the NetBSD source
4292 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4293 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4296 Implementation Internals:
4297 =========================
4299 The following is not intended to be a complete description of every
4300 implementation detail. However, it should help to understand the
4301 inner workings of U-Boot and make it easier to port it to custom
4305 Initial Stack, Global Data:
4306 ---------------------------
4308 The implementation of U-Boot is complicated by the fact that U-Boot
4309 starts running out of ROM (flash memory), usually without access to
4310 system RAM (because the memory controller is not initialized yet).
4311 This means that we don't have writable Data or BSS segments, and BSS
4312 is not initialized as zero. To be able to get a C environment working
4313 at all, we have to allocate at least a minimal stack. Implementation
4314 options for this are defined and restricted by the CPU used: Some CPU
4315 models provide on-chip memory (like the IMMR area on MPC8xx and
4316 MPC826x processors), on others (parts of) the data cache can be
4317 locked as (mis-) used as memory, etc.
4319 Chris Hallinan posted a good summary of these issues to the
4320 U-Boot mailing list:
4322 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4323 From: "Chris Hallinan" <clh@net1plus.com>
4324 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4327 Correct me if I'm wrong, folks, but the way I understand it
4328 is this: Using DCACHE as initial RAM for Stack, etc, does not
4329 require any physical RAM backing up the cache. The cleverness
4330 is that the cache is being used as a temporary supply of
4331 necessary storage before the SDRAM controller is setup. It's
4332 beyond the scope of this list to explain the details, but you
4333 can see how this works by studying the cache architecture and
4334 operation in the architecture and processor-specific manuals.
4336 OCM is On Chip Memory, which I believe the 405GP has 4K. It
4337 is another option for the system designer to use as an
4338 initial stack/RAM area prior to SDRAM being available. Either
4339 option should work for you. Using CS 4 should be fine if your
4340 board designers haven't used it for something that would
4341 cause you grief during the initial boot! It is frequently not
4344 CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4345 with your processor/board/system design. The default value
4346 you will find in any recent u-boot distribution in
4347 walnut.h should work for you. I'd set it to a value larger
4348 than your SDRAM module. If you have a 64MB SDRAM module, set
4349 it above 400_0000. Just make sure your board has no resources
4350 that are supposed to respond to that address! That code in
4351 start.S has been around a while and should work as is when
4352 you get the config right.
4357 It is essential to remember this, since it has some impact on the C
4358 code for the initialization procedures:
4360 * Initialized global data (data segment) is read-only. Do not attempt
4363 * Do not use any uninitialized global data (or implicitly initialized
4364 as zero data - BSS segment) at all - this is undefined, initiali-
4365 zation is performed later (when relocating to RAM).
4367 * Stack space is very limited. Avoid big data buffers or things like
4370 Having only the stack as writable memory limits means we cannot use
4371 normal global data to share information between the code. But it
4372 turned out that the implementation of U-Boot can be greatly
4373 simplified by making a global data structure (gd_t) available to all
4374 functions. We could pass a pointer to this data as argument to _all_
4375 functions, but this would bloat the code. Instead we use a feature of
4376 the GCC compiler (Global Register Variables) to share the data: we
4377 place a pointer (gd) to the global data into a register which we
4378 reserve for this purpose.
4380 When choosing a register for such a purpose we are restricted by the
4381 relevant (E)ABI specifications for the current architecture, and by
4382 GCC's implementation.
4384 For PowerPC, the following registers have specific use:
4386 R2: reserved for system use
4387 R3-R4: parameter passing and return values
4388 R5-R10: parameter passing
4389 R13: small data area pointer
4393 (U-Boot also uses R12 as internal GOT pointer. r12
4394 is a volatile register so r12 needs to be reset when
4395 going back and forth between asm and C)
4397 ==> U-Boot will use R2 to hold a pointer to the global data
4399 Note: on PPC, we could use a static initializer (since the
4400 address of the global data structure is known at compile time),
4401 but it turned out that reserving a register results in somewhat
4402 smaller code - although the code savings are not that big (on
4403 average for all boards 752 bytes for the whole U-Boot image,
4404 624 text + 127 data).
4406 On ARM, the following registers are used:
4408 R0: function argument word/integer result
4409 R1-R3: function argument word
4410 R9: platform specific
4411 R10: stack limit (used only if stack checking is enabled)
4412 R11: argument (frame) pointer
4413 R12: temporary workspace
4416 R15: program counter
4418 ==> U-Boot will use R9 to hold a pointer to the global data
4420 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4422 On Nios II, the ABI is documented here:
4423 http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4425 ==> U-Boot will use gp to hold a pointer to the global data
4427 Note: on Nios II, we give "-G0" option to gcc and don't use gp
4428 to access small data sections, so gp is free.
4430 On NDS32, the following registers are used:
4432 R0-R1: argument/return
4434 R15: temporary register for assembler
4435 R16: trampoline register
4436 R28: frame pointer (FP)
4437 R29: global pointer (GP)
4438 R30: link register (LP)
4439 R31: stack pointer (SP)
4440 PC: program counter (PC)
4442 ==> U-Boot will use R10 to hold a pointer to the global data
4444 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4445 or current versions of GCC may "optimize" the code too much.
4447 On RISC-V, the following registers are used:
4449 x0: hard-wired zero (zero)
4450 x1: return address (ra)
4451 x2: stack pointer (sp)
4452 x3: global pointer (gp)
4453 x4: thread pointer (tp)
4454 x5: link register (t0)
4455 x8: frame pointer (fp)
4456 x10-x11: arguments/return values (a0-1)
4457 x12-x17: arguments (a2-7)
4458 x28-31: temporaries (t3-6)
4459 pc: program counter (pc)
4461 ==> U-Boot will use gp to hold a pointer to the global data
4466 U-Boot runs in system state and uses physical addresses, i.e. the
4467 MMU is not used either for address mapping nor for memory protection.
4469 The available memory is mapped to fixed addresses using the memory
4470 controller. In this process, a contiguous block is formed for each
4471 memory type (Flash, SDRAM, SRAM), even when it consists of several
4472 physical memory banks.
4474 U-Boot is installed in the first 128 kB of the first Flash bank (on
4475 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4476 booting and sizing and initializing DRAM, the code relocates itself
4477 to the upper end of DRAM. Immediately below the U-Boot code some
4478 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4479 configuration setting]. Below that, a structure with global Board
4480 Info data is placed, followed by the stack (growing downward).
4482 Additionally, some exception handler code is copied to the low 8 kB
4483 of DRAM (0x00000000 ... 0x00001FFF).
4485 So a typical memory configuration with 16 MB of DRAM could look like
4488 0x0000 0000 Exception Vector code
4491 0x0000 2000 Free for Application Use
4497 0x00FB FF20 Monitor Stack (Growing downward)
4498 0x00FB FFAC Board Info Data and permanent copy of global data
4499 0x00FC 0000 Malloc Arena
4502 0x00FE 0000 RAM Copy of Monitor Code
4503 ... eventually: LCD or video framebuffer
4504 ... eventually: pRAM (Protected RAM - unchanged by reset)
4505 0x00FF FFFF [End of RAM]
4508 System Initialization:
4509 ----------------------
4511 In the reset configuration, U-Boot starts at the reset entry point
4512 (on most PowerPC systems at address 0x00000100). Because of the reset
4513 configuration for CS0# this is a mirror of the on board Flash memory.
4514 To be able to re-map memory U-Boot then jumps to its link address.
4515 To be able to implement the initialization code in C, a (small!)
4516 initial stack is set up in the internal Dual Ported RAM (in case CPUs
4517 which provide such a feature like), or in a locked part of the data
4518 cache. After that, U-Boot initializes the CPU core, the caches and
4521 Next, all (potentially) available memory banks are mapped using a
4522 preliminary mapping. For example, we put them on 512 MB boundaries
4523 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4524 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4525 programmed for SDRAM access. Using the temporary configuration, a
4526 simple memory test is run that determines the size of the SDRAM
4529 When there is more than one SDRAM bank, and the banks are of
4530 different size, the largest is mapped first. For equal size, the first
4531 bank (CS2#) is mapped first. The first mapping is always for address
4532 0x00000000, with any additional banks following immediately to create
4533 contiguous memory starting from 0.
4535 Then, the monitor installs itself at the upper end of the SDRAM area
4536 and allocates memory for use by malloc() and for the global Board
4537 Info data; also, the exception vector code is copied to the low RAM
4538 pages, and the final stack is set up.
4540 Only after this relocation will you have a "normal" C environment;
4541 until that you are restricted in several ways, mostly because you are
4542 running from ROM, and because the code will have to be relocated to a
4546 U-Boot Porting Guide:
4547 ----------------------
4549 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4553 int main(int argc, char *argv[])
4555 sighandler_t no_more_time;
4557 signal(SIGALRM, no_more_time);
4558 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4560 if (available_money > available_manpower) {
4561 Pay consultant to port U-Boot;
4565 Download latest U-Boot source;
4567 Subscribe to u-boot mailing list;
4570 email("Hi, I am new to U-Boot, how do I get started?");
4573 Read the README file in the top level directory;
4574 Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4575 Read applicable doc/README.*;
4576 Read the source, Luke;
4577 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4580 if (available_money > toLocalCurrency ($2500))
4583 Add a lot of aggravation and time;
4585 if (a similar board exists) { /* hopefully... */
4586 cp -a board/<similar> board/<myboard>
4587 cp include/configs/<similar>.h include/configs/<myboard>.h
4589 Create your own board support subdirectory;
4590 Create your own board include/configs/<myboard>.h file;
4592 Edit new board/<myboard> files
4593 Edit new include/configs/<myboard>.h
4598 Add / modify source code;
4602 email("Hi, I am having problems...");
4604 Send patch file to the U-Boot email list;
4605 if (reasonable critiques)
4606 Incorporate improvements from email list code review;
4608 Defend code as written;
4614 void no_more_time (int sig)
4623 All contributions to U-Boot should conform to the Linux kernel
4624 coding style; see the kernel coding style guide at
4625 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4626 script "scripts/Lindent" in your Linux kernel source directory.
4628 Source files originating from a different project (for example the
4629 MTD subsystem) are generally exempt from these guidelines and are not
4630 reformatted to ease subsequent migration to newer versions of those
4633 Please note that U-Boot is implemented in C (and to some small parts in
4634 Assembler); no C++ is used, so please do not use C++ style comments (//)
4637 Please also stick to the following formatting rules:
4638 - remove any trailing white space
4639 - use TAB characters for indentation and vertical alignment, not spaces
4640 - make sure NOT to use DOS '\r\n' line feeds
4641 - do not add more than 2 consecutive empty lines to source files
4642 - do not add trailing empty lines to source files
4644 Submissions which do not conform to the standards may be returned
4645 with a request to reformat the changes.
4651 Since the number of patches for U-Boot is growing, we need to
4652 establish some rules. Submissions which do not conform to these rules
4653 may be rejected, even when they contain important and valuable stuff.
4655 Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4657 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4658 see https://lists.denx.de/listinfo/u-boot
4660 When you send a patch, please include the following information with
4663 * For bug fixes: a description of the bug and how your patch fixes
4664 this bug. Please try to include a way of demonstrating that the
4665 patch actually fixes something.
4667 * For new features: a description of the feature and your
4670 * For major contributions, add a MAINTAINERS file with your
4671 information and associated file and directory references.
4673 * When you add support for a new board, don't forget to add a
4674 maintainer e-mail address to the boards.cfg file, too.
4676 * If your patch adds new configuration options, don't forget to
4677 document these in the README file.
4679 * The patch itself. If you are using git (which is *strongly*
4680 recommended) you can easily generate the patch using the
4681 "git format-patch". If you then use "git send-email" to send it to
4682 the U-Boot mailing list, you will avoid most of the common problems
4683 with some other mail clients.
4685 If you cannot use git, use "diff -purN OLD NEW". If your version of
4686 diff does not support these options, then get the latest version of
4689 The current directory when running this command shall be the parent
4690 directory of the U-Boot source tree (i. e. please make sure that
4691 your patch includes sufficient directory information for the
4694 We prefer patches as plain text. MIME attachments are discouraged,
4695 and compressed attachments must not be used.
4697 * If one logical set of modifications affects or creates several
4698 files, all these changes shall be submitted in a SINGLE patch file.
4700 * Changesets that contain different, unrelated modifications shall be
4701 submitted as SEPARATE patches, one patch per changeset.
4706 * Before sending the patch, run the buildman script on your patched
4707 source tree and make sure that no errors or warnings are reported
4708 for any of the boards.
4710 * Keep your modifications to the necessary minimum: A patch
4711 containing several unrelated changes or arbitrary reformats will be
4712 returned with a request to re-formatting / split it.
4714 * If you modify existing code, make sure that your new code does not
4715 add to the memory footprint of the code ;-) Small is beautiful!
4716 When adding new features, these should compile conditionally only
4717 (using #ifdef), and the resulting code with the new feature
4718 disabled must not need more memory than the old code without your
4721 * Remember that there is a size limit of 100 kB per message on the
4722 u-boot mailing list. Bigger patches will be moderated. If they are
4723 reasonable and not too big, they will be acknowledged. But patches
4724 bigger than the size limit should be avoided.