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:
562 CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]
564 When transferring memsize parameter to Linux, some versions
565 expect it to be in bytes, others in MB.
566 Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
570 New kernel versions are expecting firmware settings to be
571 passed using flattened device trees (based on open firmware
575 * New libfdt-based support
576 * Adds the "fdt" command
577 * The bootm command automatically updates the fdt
579 OF_TBCLK - The timebase frequency.
580 OF_STDOUT_PATH - The path to the console device
582 boards with QUICC Engines require OF_QE to set UCC MAC
585 CONFIG_OF_BOARD_SETUP
587 Board code has addition modification that it wants to make
588 to the flat device tree before handing it off to the kernel
590 CONFIG_OF_SYSTEM_SETUP
592 Other code has addition modification that it wants to make
593 to the flat device tree before handing it off to the kernel.
594 This causes ft_system_setup() to be called before booting
599 U-Boot can detect if an IDE device is present or not.
600 If not, and this new config option is activated, U-Boot
601 removes the ATA node from the DTS before booting Linux,
602 so the Linux IDE driver does not probe the device and
603 crash. This is needed for buggy hardware (uc101) where
604 no pull down resistor is connected to the signal IDE5V_DD7.
606 CONFIG_MACH_TYPE [relevant for ARM only][mandatory]
608 This setting is mandatory for all boards that have only one
609 machine type and must be used to specify the machine type
610 number as it appears in the ARM machine registry
611 (see http://www.arm.linux.org.uk/developer/machines/).
612 Only boards that have multiple machine types supported
613 in a single configuration file and the machine type is
614 runtime discoverable, do not have to use this setting.
616 - vxWorks boot parameters:
618 bootvx constructs a valid bootline using the following
619 environments variables: bootdev, bootfile, ipaddr, netmask,
620 serverip, gatewayip, hostname, othbootargs.
621 It loads the vxWorks image pointed bootfile.
623 Note: If a "bootargs" environment is defined, it will overwride
624 the defaults discussed just above.
626 - Cache Configuration:
627 CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
629 - Cache Configuration for ARM:
630 CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
632 CONFIG_SYS_PL310_BASE - Physical base address of PL310
633 controller register space
638 Define this if you want support for Amba PrimeCell PL010 UARTs.
642 Define this if you want support for Amba PrimeCell PL011 UARTs.
646 If you have Amba PrimeCell PL011 UARTs, set this variable to
647 the clock speed of the UARTs.
651 If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
652 define this to a list of base addresses for each (supported)
653 port. See e.g. include/configs/versatile.h
655 CONFIG_SERIAL_HW_FLOW_CONTROL
657 Define this variable to enable hw flow control in serial driver.
658 Current user of this option is drivers/serial/nsl16550.c driver
662 Only needed when CONFIG_BOOTDELAY is enabled;
663 define a command string that is automatically executed
664 when no character is read on the console interface
665 within "Boot Delay" after reset.
667 CONFIG_RAMBOOT and CONFIG_NFSBOOT
668 The value of these goes into the environment as
669 "ramboot" and "nfsboot" respectively, and can be used
670 as a convenience, when switching between booting from
673 - Serial Download Echo Mode:
675 If defined to 1, all characters received during a
676 serial download (using the "loads" command) are
677 echoed back. This might be needed by some terminal
678 emulations (like "cu"), but may as well just take
679 time on others. This setting #define's the initial
680 value of the "loads_echo" environment variable.
682 - Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
684 Select one of the baudrates listed in
685 CONFIG_SYS_BAUDRATE_TABLE, see below.
687 - Removal of commands
688 If no commands are needed to boot, you can disable
689 CONFIG_CMDLINE to remove them. In this case, the command line
690 will not be available, and when U-Boot wants to execute the
691 boot command (on start-up) it will call board_run_command()
692 instead. This can reduce image size significantly for very
693 simple boot procedures.
695 - Regular expression support:
697 If this variable is defined, U-Boot is linked against
698 the SLRE (Super Light Regular Expression) library,
699 which adds regex support to some commands, as for
700 example "env grep" and "setexpr".
704 If this variable is defined, U-Boot will use a device tree
705 to configure its devices, instead of relying on statically
706 compiled #defines in the board file. This option is
707 experimental and only available on a few boards. The device
708 tree is available in the global data as gd->fdt_blob.
710 U-Boot needs to get its device tree from somewhere. This can
711 be done using one of the three options below:
714 If this variable is defined, U-Boot will embed a device tree
715 binary in its image. This device tree file should be in the
716 board directory and called <soc>-<board>.dts. The binary file
717 is then picked up in board_init_f() and made available through
718 the global data structure as gd->fdt_blob.
721 If this variable is defined, U-Boot will build a device tree
722 binary. It will be called u-boot.dtb. Architecture-specific
723 code will locate it at run-time. Generally this works by:
725 cat u-boot.bin u-boot.dtb >image.bin
727 and in fact, U-Boot does this for you, creating a file called
728 u-boot-dtb.bin which is useful in the common case. You can
729 still use the individual files if you need something more
733 If this variable is defined, U-Boot will use the device tree
734 provided by the board at runtime instead of embedding one with
735 the image. Only boards defining board_fdt_blob_setup() support
736 this option (see include/fdtdec.h file).
740 If this variable is defined, it enables watchdog
741 support for the SoC. There must be support in the SoC
742 specific code for a watchdog. For the 8xx
743 CPUs, the SIU Watchdog feature is enabled in the SYPCR
744 register. When supported for a specific SoC is
745 available, then no further board specific code should
749 When using a watchdog circuitry external to the used
750 SoC, then define this variable and provide board
751 specific code for the "hw_watchdog_reset" function.
755 When CONFIG_CMD_DATE is selected, the type of the RTC
756 has to be selected, too. Define exactly one of the
759 CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
760 CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
761 CONFIG_RTC_MC146818 - use MC146818 RTC
762 CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
763 CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
764 CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
765 CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
766 CONFIG_RTC_DS164x - use Dallas DS164x RTC
767 CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
768 CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
769 CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
770 CONFIG_SYS_RV3029_TCR - enable trickle charger on
773 Note that if the RTC uses I2C, then the I2C interface
774 must also be configured. See I2C Support, below.
777 CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
779 The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
780 chip-ngpio pairs that tell the PCA953X driver the number of
781 pins supported by a particular chip.
783 Note that if the GPIO device uses I2C, then the I2C interface
784 must also be configured. See I2C Support, below.
787 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
788 accesses and can checksum them or write a list of them out
789 to memory. See the 'iotrace' command for details. This is
790 useful for testing device drivers since it can confirm that
791 the driver behaves the same way before and after a code
792 change. Currently this is supported on sandbox and arm. To
793 add support for your architecture, add '#include <iotrace.h>'
794 to the bottom of arch/<arch>/include/asm/io.h and test.
796 Example output from the 'iotrace stats' command is below.
797 Note that if the trace buffer is exhausted, the checksum will
798 still continue to operate.
801 Start: 10000000 (buffer start address)
802 Size: 00010000 (buffer size)
803 Offset: 00000120 (current buffer offset)
804 Output: 10000120 (start + offset)
805 Count: 00000018 (number of trace records)
806 CRC32: 9526fb66 (CRC32 of all trace records)
810 When CONFIG_TIMESTAMP is selected, the timestamp
811 (date and time) of an image is printed by image
812 commands like bootm or iminfo. This option is
813 automatically enabled when you select CONFIG_CMD_DATE .
815 - Partition Labels (disklabels) Supported:
816 Zero or more of the following:
817 CONFIG_MAC_PARTITION Apple's MacOS partition table.
818 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
819 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
820 bootloader. Note 2TB partition limit; see
822 CONFIG_SCSI) you must configure support for at
823 least one non-MTD partition type as well.
826 CONFIG_IDE_RESET_ROUTINE - this is defined in several
827 board configurations files but used nowhere!
829 CONFIG_IDE_RESET - is this is defined, IDE Reset will
830 be performed by calling the function
831 ide_set_reset(int reset)
832 which has to be defined in a board specific file
837 Set this to enable ATAPI support.
842 Set this to enable support for disks larger than 137GB
843 Also look at CONFIG_SYS_64BIT_LBA.
844 Whithout these , LBA48 support uses 32bit variables and will 'only'
845 support disks up to 2.1TB.
847 CONFIG_SYS_64BIT_LBA:
848 When enabled, makes the IDE subsystem use 64bit sector addresses.
852 CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
853 CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
854 CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
855 maximum numbers of LUNs, SCSI ID's and target
858 The environment variable 'scsidevs' is set to the number of
859 SCSI devices found during the last scan.
861 - NETWORK Support (PCI):
863 Support for Intel 8254x/8257x gigabit chips.
866 Utility code for direct access to the SPI bus on Intel 8257x.
867 This does not do anything useful unless you set at least one
868 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
870 CONFIG_E1000_SPI_GENERIC
871 Allow generic access to the SPI bus on the Intel 8257x, for
872 example with the "sspi" command.
875 Support for National dp83815 chips.
878 Support for National dp8382[01] gigabit chips.
880 - NETWORK Support (other):
882 CONFIG_DRIVER_AT91EMAC
883 Support for AT91RM9200 EMAC.
886 Define this to use reduced MII inteface
888 CONFIG_DRIVER_AT91EMAC_QUIET
889 If this defined, the driver is quiet.
890 The driver doen't show link status messages.
893 Support for the Calxeda XGMAC device
896 Support for SMSC's LAN91C96 chips.
898 CONFIG_LAN91C96_USE_32_BIT
899 Define this to enable 32 bit addressing
902 Support for SMSC's LAN91C111 chip
905 Define this to hold the physical address
906 of the device (I/O space)
908 CONFIG_SMC_USE_32_BIT
909 Define this if data bus is 32 bits
911 CONFIG_SMC_USE_IOFUNCS
912 Define this to use i/o functions instead of macros
913 (some hardware wont work with macros)
915 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
916 Define this if you have more then 3 PHYs.
919 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
921 CONFIG_FTGMAC100_EGIGA
922 Define this to use GE link update with gigabit PHY.
923 Define this if FTGMAC100 is connected to gigabit PHY.
924 If your system has 10/100 PHY only, it might not occur
925 wrong behavior. Because PHY usually return timeout or
926 useless data when polling gigabit status and gigabit
927 control registers. This behavior won't affect the
928 correctnessof 10/100 link speed update.
931 Support for Renesas on-chip Ethernet controller
933 CONFIG_SH_ETHER_USE_PORT
934 Define the number of ports to be used
936 CONFIG_SH_ETHER_PHY_ADDR
937 Define the ETH PHY's address
939 CONFIG_SH_ETHER_CACHE_WRITEBACK
940 If this option is set, the driver enables cache flush.
946 CONFIG_TPM_TIS_INFINEON
947 Support for Infineon i2c bus TPM devices. Only one device
948 per system is supported at this time.
950 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
951 Define the burst count bytes upper limit
954 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
956 CONFIG_TPM_ST33ZP24_I2C
957 Support for STMicroelectronics ST33ZP24 I2C devices.
958 Requires TPM_ST33ZP24 and I2C.
960 CONFIG_TPM_ST33ZP24_SPI
961 Support for STMicroelectronics ST33ZP24 SPI devices.
962 Requires TPM_ST33ZP24 and SPI.
965 Support for Atmel TWI TPM device. Requires I2C support.
968 Support for generic parallel port TPM devices. Only one device
969 per system is supported at this time.
971 CONFIG_TPM_TIS_BASE_ADDRESS
972 Base address where the generic TPM device is mapped
973 to. Contemporary x86 systems usually map it at
977 Define this to enable the TPM support library which provides
978 functional interfaces to some TPM commands.
979 Requires support for a TPM device.
981 CONFIG_TPM_AUTH_SESSIONS
982 Define this to enable authorized functions in the TPM library.
983 Requires CONFIG_TPM and CONFIG_SHA1.
986 At the moment only the UHCI host controller is
987 supported (PIP405, MIP405); define
988 CONFIG_USB_UHCI to enable it.
989 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
990 and define CONFIG_USB_STORAGE to enable the USB
993 Supported are USB Keyboards and USB Floppy drives
996 CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
997 txfilltuning field in the EHCI controller on reset.
999 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1000 HW module registers.
1003 Define the below if you wish to use the USB console.
1004 Once firmware is rebuilt from a serial console issue the
1005 command "setenv stdin usbtty; setenv stdout usbtty" and
1006 attach your USB cable. The Unix command "dmesg" should print
1007 it has found a new device. The environment variable usbtty
1008 can be set to gserial or cdc_acm to enable your device to
1009 appear to a USB host as a Linux gserial device or a
1010 Common Device Class Abstract Control Model serial device.
1011 If you select usbtty = gserial you should be able to enumerate
1013 # modprobe usbserial vendor=0xVendorID product=0xProductID
1014 else if using cdc_acm, simply setting the environment
1015 variable usbtty to be cdc_acm should suffice. The following
1016 might be defined in YourBoardName.h
1019 Define this to build a UDC device
1022 Define this to have a tty type of device available to
1023 talk to the UDC device
1026 Define this to enable the high speed support for usb
1027 device and usbtty. If this feature is enabled, a routine
1028 int is_usbd_high_speed(void)
1029 also needs to be defined by the driver to dynamically poll
1030 whether the enumeration has succeded at high speed or full
1033 CONFIG_SYS_CONSOLE_IS_IN_ENV
1034 Define this if you want stdin, stdout &/or stderr to
1037 If you have a USB-IF assigned VendorID then you may wish to
1038 define your own vendor specific values either in BoardName.h
1039 or directly in usbd_vendor_info.h. If you don't define
1040 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1041 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1042 should pretend to be a Linux device to it's target host.
1044 CONFIG_USBD_MANUFACTURER
1045 Define this string as the name of your company for
1046 - CONFIG_USBD_MANUFACTURER "my company"
1048 CONFIG_USBD_PRODUCT_NAME
1049 Define this string as the name of your product
1050 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1052 CONFIG_USBD_VENDORID
1053 Define this as your assigned Vendor ID from the USB
1054 Implementors Forum. This *must* be a genuine Vendor ID
1055 to avoid polluting the USB namespace.
1056 - CONFIG_USBD_VENDORID 0xFFFF
1058 CONFIG_USBD_PRODUCTID
1059 Define this as the unique Product ID
1061 - CONFIG_USBD_PRODUCTID 0xFFFF
1063 - ULPI Layer Support:
1064 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1065 the generic ULPI layer. The generic layer accesses the ULPI PHY
1066 via the platform viewport, so you need both the genric layer and
1067 the viewport enabled. Currently only Chipidea/ARC based
1068 viewport is supported.
1069 To enable the ULPI layer support, define CONFIG_USB_ULPI and
1070 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1071 If your ULPI phy needs a different reference clock than the
1072 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1073 the appropriate value in Hz.
1076 The MMC controller on the Intel PXA is supported. To
1077 enable this define CONFIG_MMC. The MMC can be
1078 accessed from the boot prompt by mapping the device
1079 to physical memory similar to flash. Command line is
1080 enabled with CONFIG_CMD_MMC. The MMC driver also works with
1081 the FAT fs. This is enabled with CONFIG_CMD_FAT.
1084 Support for Renesas on-chip MMCIF controller
1086 CONFIG_SH_MMCIF_ADDR
1087 Define the base address of MMCIF registers
1090 Define the clock frequency for MMCIF
1092 - USB Device Firmware Update (DFU) class support:
1094 This enables the USB portion of the DFU USB class
1097 This enables support for exposing NAND devices via DFU.
1100 This enables support for exposing RAM via DFU.
1101 Note: DFU spec refer to non-volatile memory usage, but
1102 allow usages beyond the scope of spec - here RAM usage,
1103 one that would help mostly the developer.
1105 CONFIG_SYS_DFU_DATA_BUF_SIZE
1106 Dfu transfer uses a buffer before writing data to the
1107 raw storage device. Make the size (in bytes) of this buffer
1108 configurable. The size of this buffer is also configurable
1109 through the "dfu_bufsiz" environment variable.
1111 CONFIG_SYS_DFU_MAX_FILE_SIZE
1112 When updating files rather than the raw storage device,
1113 we use a static buffer to copy the file into and then write
1114 the buffer once we've been given the whole file. Define
1115 this to the maximum filesize (in bytes) for the buffer.
1116 Default is 4 MiB if undefined.
1118 DFU_DEFAULT_POLL_TIMEOUT
1119 Poll timeout [ms], is the timeout a device can send to the
1120 host. The host must wait for this timeout before sending
1121 a subsequent DFU_GET_STATUS request to the device.
1123 DFU_MANIFEST_POLL_TIMEOUT
1124 Poll timeout [ms], which the device sends to the host when
1125 entering dfuMANIFEST state. Host waits this timeout, before
1126 sending again an USB request to the device.
1128 - Journaling Flash filesystem support:
1130 Define these for a default partition on a NAND device
1132 CONFIG_SYS_JFFS2_FIRST_SECTOR,
1133 CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1134 Define these for a default partition on a NOR device
1137 See Kconfig help for available keyboard drivers.
1141 Define this to enable a custom keyboard support.
1142 This simply calls drv_keyboard_init() which must be
1143 defined in your board-specific files. This option is deprecated
1144 and is only used by novena. For new boards, use driver model
1149 Enable the Freescale DIU video driver. Reference boards for
1150 SOCs that have a DIU should define this macro to enable DIU
1151 support, and should also define these other macros:
1156 CONFIG_VIDEO_SW_CURSOR
1157 CONFIG_VGA_AS_SINGLE_DEVICE
1159 CONFIG_VIDEO_BMP_LOGO
1161 The DIU driver will look for the 'video-mode' environment
1162 variable, and if defined, enable the DIU as a console during
1163 boot. See the documentation file doc/README.video for a
1164 description of this variable.
1166 - LCD Support: CONFIG_LCD
1168 Define this to enable LCD support (for output to LCD
1169 display); also select one of the supported displays
1170 by defining one of these:
1174 HITACHI TX09D70VM1CCA, 3.5", 240x320.
1176 CONFIG_NEC_NL6448AC33:
1178 NEC NL6448AC33-18. Active, color, single scan.
1180 CONFIG_NEC_NL6448BC20
1182 NEC NL6448BC20-08. 6.5", 640x480.
1183 Active, color, single scan.
1185 CONFIG_NEC_NL6448BC33_54
1187 NEC NL6448BC33-54. 10.4", 640x480.
1188 Active, color, single scan.
1192 Sharp 320x240. Active, color, single scan.
1193 It isn't 16x9, and I am not sure what it is.
1195 CONFIG_SHARP_LQ64D341
1197 Sharp LQ64D341 display, 640x480.
1198 Active, color, single scan.
1202 HLD1045 display, 640x480.
1203 Active, color, single scan.
1207 Optrex CBL50840-2 NF-FW 99 22 M5
1209 Hitachi LMG6912RPFC-00T
1213 320x240. Black & white.
1215 CONFIG_LCD_ALIGNMENT
1217 Normally the LCD is page-aligned (typically 4KB). If this is
1218 defined then the LCD will be aligned to this value instead.
1219 For ARM it is sometimes useful to use MMU_SECTION_SIZE
1220 here, since it is cheaper to change data cache settings on
1221 a per-section basis.
1226 Sometimes, for example if the display is mounted in portrait
1227 mode or even if it's mounted landscape but rotated by 180degree,
1228 we need to rotate our content of the display relative to the
1229 framebuffer, so that user can read the messages which are
1231 Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1232 initialized with a given rotation from "vl_rot" out of
1233 "vidinfo_t" which is provided by the board specific code.
1234 The value for vl_rot is coded as following (matching to
1235 fbcon=rotate:<n> linux-kernel commandline):
1236 0 = no rotation respectively 0 degree
1237 1 = 90 degree rotation
1238 2 = 180 degree rotation
1239 3 = 270 degree rotation
1241 If CONFIG_LCD_ROTATION is not defined, the console will be
1242 initialized with 0degree rotation.
1246 Support drawing of RLE8-compressed bitmaps on the LCD.
1250 Enables an 'i2c edid' command which can read EDID
1251 information over I2C from an attached LCD display.
1253 - Splash Screen Support: CONFIG_SPLASH_SCREEN
1255 If this option is set, the environment is checked for
1256 a variable "splashimage". If found, the usual display
1257 of logo, copyright and system information on the LCD
1258 is suppressed and the BMP image at the address
1259 specified in "splashimage" is loaded instead. The
1260 console is redirected to the "nulldev", too. This
1261 allows for a "silent" boot where a splash screen is
1262 loaded very quickly after power-on.
1264 CONFIG_SPLASHIMAGE_GUARD
1266 If this option is set, then U-Boot will prevent the environment
1267 variable "splashimage" from being set to a problematic address
1268 (see doc/README.displaying-bmps).
1269 This option is useful for targets where, due to alignment
1270 restrictions, an improperly aligned BMP image will cause a data
1271 abort. If you think you will not have problems with unaligned
1272 accesses (for example because your toolchain prevents them)
1273 there is no need to set this option.
1275 CONFIG_SPLASH_SCREEN_ALIGN
1277 If this option is set the splash image can be freely positioned
1278 on the screen. Environment variable "splashpos" specifies the
1279 position as "x,y". If a positive number is given it is used as
1280 number of pixel from left/top. If a negative number is given it
1281 is used as number of pixel from right/bottom. You can also
1282 specify 'm' for centering the image.
1285 setenv splashpos m,m
1286 => image at center of screen
1288 setenv splashpos 30,20
1289 => image at x = 30 and y = 20
1291 setenv splashpos -10,m
1292 => vertically centered image
1293 at x = dspWidth - bmpWidth - 9
1295 - Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1297 If this option is set, additionally to standard BMP
1298 images, gzipped BMP images can be displayed via the
1299 splashscreen support or the bmp command.
1301 - Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1303 If this option is set, 8-bit RLE compressed BMP images
1304 can be displayed via the splashscreen support or the
1308 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1310 The clock frequency of the MII bus
1312 CONFIG_PHY_RESET_DELAY
1314 Some PHY like Intel LXT971A need extra delay after
1315 reset before any MII register access is possible.
1316 For such PHY, set this option to the usec delay
1317 required. (minimum 300usec for LXT971A)
1319 CONFIG_PHY_CMD_DELAY (ppc4xx)
1321 Some PHY like Intel LXT971A need extra delay after
1322 command issued before MII status register can be read
1327 Define a default value for the IP address to use for
1328 the default Ethernet interface, in case this is not
1329 determined through e.g. bootp.
1330 (Environment variable "ipaddr")
1332 - Server IP address:
1335 Defines a default value for the IP address of a TFTP
1336 server to contact when using the "tftboot" command.
1337 (Environment variable "serverip")
1339 CONFIG_KEEP_SERVERADDR
1341 Keeps the server's MAC address, in the env 'serveraddr'
1342 for passing to bootargs (like Linux's netconsole option)
1344 - Gateway IP address:
1347 Defines a default value for the IP address of the
1348 default router where packets to other networks are
1350 (Environment variable "gatewayip")
1355 Defines a default value for the subnet mask (or
1356 routing prefix) which is used to determine if an IP
1357 address belongs to the local subnet or needs to be
1358 forwarded through a router.
1359 (Environment variable "netmask")
1361 - BOOTP Recovery Mode:
1362 CONFIG_BOOTP_RANDOM_DELAY
1364 If you have many targets in a network that try to
1365 boot using BOOTP, you may want to avoid that all
1366 systems send out BOOTP requests at precisely the same
1367 moment (which would happen for instance at recovery
1368 from a power failure, when all systems will try to
1369 boot, thus flooding the BOOTP server. Defining
1370 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1371 inserted before sending out BOOTP requests. The
1372 following delays are inserted then:
1374 1st BOOTP request: delay 0 ... 1 sec
1375 2nd BOOTP request: delay 0 ... 2 sec
1376 3rd BOOTP request: delay 0 ... 4 sec
1378 BOOTP requests: delay 0 ... 8 sec
1380 CONFIG_BOOTP_ID_CACHE_SIZE
1382 BOOTP packets are uniquely identified using a 32-bit ID. The
1383 server will copy the ID from client requests to responses and
1384 U-Boot will use this to determine if it is the destination of
1385 an incoming response. Some servers will check that addresses
1386 aren't in use before handing them out (usually using an ARP
1387 ping) and therefore take up to a few hundred milliseconds to
1388 respond. Network congestion may also influence the time it
1389 takes for a response to make it back to the client. If that
1390 time is too long, U-Boot will retransmit requests. In order
1391 to allow earlier responses to still be accepted after these
1392 retransmissions, U-Boot's BOOTP client keeps a small cache of
1393 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1394 cache. The default is to keep IDs for up to four outstanding
1395 requests. Increasing this will allow U-Boot to accept offers
1396 from a BOOTP client in networks with unusually high latency.
1398 - DHCP Advanced Options:
1399 You can fine tune the DHCP functionality by defining
1400 CONFIG_BOOTP_* symbols:
1402 CONFIG_BOOTP_NISDOMAIN
1403 CONFIG_BOOTP_BOOTFILESIZE
1404 CONFIG_BOOTP_SEND_HOSTNAME
1405 CONFIG_BOOTP_NTPSERVER
1406 CONFIG_BOOTP_TIMEOFFSET
1407 CONFIG_BOOTP_VENDOREX
1408 CONFIG_BOOTP_MAY_FAIL
1410 CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1411 environment variable, not the BOOTP server.
1413 CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1414 after the configured retry count, the call will fail
1415 instead of starting over. This can be used to fail over
1416 to Link-local IP address configuration if the DHCP server
1419 CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1420 to do a dynamic update of a DNS server. To do this, they
1421 need the hostname of the DHCP requester.
1422 If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1423 of the "hostname" environment variable is passed as
1424 option 12 to the DHCP server.
1426 CONFIG_BOOTP_DHCP_REQUEST_DELAY
1428 A 32bit value in microseconds for a delay between
1429 receiving a "DHCP Offer" and sending the "DHCP Request".
1430 This fixes a problem with certain DHCP servers that don't
1431 respond 100% of the time to a "DHCP request". E.g. On an
1432 AT91RM9200 processor running at 180MHz, this delay needed
1433 to be *at least* 15,000 usec before a Windows Server 2003
1434 DHCP server would reply 100% of the time. I recommend at
1435 least 50,000 usec to be safe. The alternative is to hope
1436 that one of the retries will be successful but note that
1437 the DHCP timeout and retry process takes a longer than
1440 - Link-local IP address negotiation:
1441 Negotiate with other link-local clients on the local network
1442 for an address that doesn't require explicit configuration.
1443 This is especially useful if a DHCP server cannot be guaranteed
1444 to exist in all environments that the device must operate.
1446 See doc/README.link-local for more information.
1448 - MAC address from environment variables
1450 FDT_SEQ_MACADDR_FROM_ENV
1452 Fix-up device tree with MAC addresses fetched sequentially from
1453 environment variables. This config work on assumption that
1454 non-usable ethernet node of device-tree are either not present
1455 or their status has been marked as "disabled".
1458 CONFIG_CDP_DEVICE_ID
1460 The device id used in CDP trigger frames.
1462 CONFIG_CDP_DEVICE_ID_PREFIX
1464 A two character string which is prefixed to the MAC address
1469 A printf format string which contains the ascii name of
1470 the port. Normally is set to "eth%d" which sets
1471 eth0 for the first Ethernet, eth1 for the second etc.
1473 CONFIG_CDP_CAPABILITIES
1475 A 32bit integer which indicates the device capabilities;
1476 0x00000010 for a normal host which does not forwards.
1480 An ascii string containing the version of the software.
1484 An ascii string containing the name of the platform.
1488 A 32bit integer sent on the trigger.
1490 CONFIG_CDP_POWER_CONSUMPTION
1492 A 16bit integer containing the power consumption of the
1493 device in .1 of milliwatts.
1495 CONFIG_CDP_APPLIANCE_VLAN_TYPE
1497 A byte containing the id of the VLAN.
1499 - Status LED: CONFIG_LED_STATUS
1501 Several configurations allow to display the current
1502 status using a LED. For instance, the LED will blink
1503 fast while running U-Boot code, stop blinking as
1504 soon as a reply to a BOOTP request was received, and
1505 start blinking slow once the Linux kernel is running
1506 (supported by a status LED driver in the Linux
1507 kernel). Defining CONFIG_LED_STATUS enables this
1512 CONFIG_LED_STATUS_GPIO
1513 The status LED can be connected to a GPIO pin.
1514 In such cases, the gpio_led driver can be used as a
1515 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1516 to include the gpio_led driver in the U-Boot binary.
1518 CONFIG_GPIO_LED_INVERTED_TABLE
1519 Some GPIO connected LEDs may have inverted polarity in which
1520 case the GPIO high value corresponds to LED off state and
1521 GPIO low value corresponds to LED on state.
1522 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1523 with a list of GPIO LEDs that have inverted polarity.
1525 - I2C Support: CONFIG_SYS_I2C
1527 This enable the NEW i2c subsystem, and will allow you to use
1528 i2c commands at the u-boot command line (as long as you set
1529 CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1530 for defining speed and slave address
1531 - activate second bus with I2C_SOFT_DECLARATIONS2 define
1532 CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1533 for defining speed and slave address
1534 - activate third bus with I2C_SOFT_DECLARATIONS3 define
1535 CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1536 for defining speed and slave address
1537 - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1538 CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1539 for defining speed and slave address
1541 - drivers/i2c/fsl_i2c.c:
1542 - activate i2c driver with CONFIG_SYS_I2C_FSL
1543 define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1544 offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1545 CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1547 - If your board supports a second fsl i2c bus, define
1548 CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1549 CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1550 CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1553 - drivers/i2c/tegra_i2c.c:
1554 - activate this driver with CONFIG_SYS_I2C_TEGRA
1555 - This driver adds 4 i2c buses with a fix speed from
1556 100000 and the slave addr 0!
1558 - drivers/i2c/ppc4xx_i2c.c
1559 - activate this driver with CONFIG_SYS_I2C_PPC4XX
1560 - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1561 - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1563 - drivers/i2c/i2c_mxc.c
1564 - activate this driver with CONFIG_SYS_I2C_MXC
1565 - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1566 - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1567 - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1568 - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1569 - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1570 - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1571 - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1572 - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1573 - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1574 - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1575 - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1576 - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1577 If those defines are not set, default value is 100000
1578 for speed, and 0 for slave.
1580 - drivers/i2c/rcar_i2c.c:
1581 - activate this driver with CONFIG_SYS_I2C_RCAR
1582 - This driver adds 4 i2c buses
1584 - drivers/i2c/sh_i2c.c:
1585 - activate this driver with CONFIG_SYS_I2C_SH
1586 - This driver adds from 2 to 5 i2c buses
1588 - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1589 - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1590 - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1591 - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1592 - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1593 - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1594 - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1595 - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1596 - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1597 - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1598 - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1600 - drivers/i2c/omap24xx_i2c.c
1601 - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1602 - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1603 - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1604 - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1605 - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1606 - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1607 - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1608 - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1609 - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1610 - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1611 - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1613 - drivers/i2c/s3c24x0_i2c.c:
1614 - activate this driver with CONFIG_SYS_I2C_S3C24X0
1615 - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1616 9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1617 with a fix speed from 100000 and the slave addr 0!
1619 - drivers/i2c/ihs_i2c.c
1620 - activate this driver with CONFIG_SYS_I2C_IHS
1621 - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1622 - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1623 - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1624 - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1625 - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1626 - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1627 - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1628 - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1629 - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1630 - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1631 - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1632 - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1633 - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1634 - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1635 - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1636 - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1637 - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1638 - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1639 - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1640 - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1641 - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1645 CONFIG_SYS_NUM_I2C_BUSES
1646 Hold the number of i2c buses you want to use.
1648 CONFIG_SYS_I2C_DIRECT_BUS
1649 define this, if you don't use i2c muxes on your hardware.
1650 if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1653 CONFIG_SYS_I2C_MAX_HOPS
1654 define how many muxes are maximal consecutively connected
1655 on one i2c bus. If you not use i2c muxes, omit this
1658 CONFIG_SYS_I2C_BUSES
1659 hold a list of buses you want to use, only used if
1660 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1661 a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1662 CONFIG_SYS_NUM_I2C_BUSES = 9:
1664 CONFIG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
1665 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1666 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1667 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1668 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1669 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1670 {1, {I2C_NULL_HOP}}, \
1671 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1672 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1676 bus 0 on adapter 0 without a mux
1677 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1678 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1679 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1680 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1681 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1682 bus 6 on adapter 1 without a mux
1683 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1684 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1686 If you do not have i2c muxes on your board, omit this define.
1688 - Legacy I2C Support:
1689 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1690 then the following macros need to be defined (examples are
1691 from include/configs/lwmon.h):
1695 (Optional). Any commands necessary to enable the I2C
1696 controller or configure ports.
1698 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
1702 The code necessary to make the I2C data line active
1703 (driven). If the data line is open collector, this
1706 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
1710 The code necessary to make the I2C data line tri-stated
1711 (inactive). If the data line is open collector, this
1714 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1718 Code that returns true if the I2C data line is high,
1721 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1725 If <bit> is true, sets the I2C data line high. If it
1726 is false, it clears it (low).
1728 eg: #define I2C_SDA(bit) \
1729 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
1730 else immr->im_cpm.cp_pbdat &= ~PB_SDA
1734 If <bit> is true, sets the I2C clock line high. If it
1735 is false, it clears it (low).
1737 eg: #define I2C_SCL(bit) \
1738 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
1739 else immr->im_cpm.cp_pbdat &= ~PB_SCL
1743 This delay is invoked four times per clock cycle so this
1744 controls the rate of data transfer. The data rate thus
1745 is 1 / (I2C_DELAY * 4). Often defined to be something
1748 #define I2C_DELAY udelay(2)
1750 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1752 If your arch supports the generic GPIO framework (asm/gpio.h),
1753 then you may alternatively define the two GPIOs that are to be
1754 used as SCL / SDA. Any of the previous I2C_xxx macros will
1755 have GPIO-based defaults assigned to them as appropriate.
1757 You should define these to the GPIO value as given directly to
1758 the generic GPIO functions.
1760 CONFIG_SYS_I2C_INIT_BOARD
1762 When a board is reset during an i2c bus transfer
1763 chips might think that the current transfer is still
1764 in progress. On some boards it is possible to access
1765 the i2c SCLK line directly, either by using the
1766 processor pin as a GPIO or by having a second pin
1767 connected to the bus. If this option is defined a
1768 custom i2c_init_board() routine in boards/xxx/board.c
1769 is run early in the boot sequence.
1771 CONFIG_I2C_MULTI_BUS
1773 This option allows the use of multiple I2C buses, each of which
1774 must have a controller. At any point in time, only one bus is
1775 active. To switch to a different bus, use the 'i2c dev' command.
1776 Note that bus numbering is zero-based.
1778 CONFIG_SYS_I2C_NOPROBES
1780 This option specifies a list of I2C devices that will be skipped
1781 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
1782 is set, specify a list of bus-device pairs. Otherwise, specify
1783 a 1D array of device addresses
1786 #undef CONFIG_I2C_MULTI_BUS
1787 #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1789 will skip addresses 0x50 and 0x68 on a board with one I2C bus
1791 #define CONFIG_I2C_MULTI_BUS
1792 #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1794 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1796 CONFIG_SYS_SPD_BUS_NUM
1798 If defined, then this indicates the I2C bus number for DDR SPD.
1799 If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1801 CONFIG_SYS_RTC_BUS_NUM
1803 If defined, then this indicates the I2C bus number for the RTC.
1804 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1806 CONFIG_SOFT_I2C_READ_REPEATED_START
1808 defining this will force the i2c_read() function in
1809 the soft_i2c driver to perform an I2C repeated start
1810 between writing the address pointer and reading the
1811 data. If this define is omitted the default behaviour
1812 of doing a stop-start sequence will be used. Most I2C
1813 devices can use either method, but some require one or
1816 - SPI Support: CONFIG_SPI
1818 Enables SPI driver (so far only tested with
1819 SPI EEPROM, also an instance works with Crystal A/D and
1820 D/As on the SACSng board)
1824 Enables a software (bit-bang) SPI driver rather than
1825 using hardware support. This is a general purpose
1826 driver that only requires three general I/O port pins
1827 (two outputs, one input) to function. If this is
1828 defined, the board configuration must define several
1829 SPI configuration items (port pins to use, etc). For
1830 an example, see include/configs/sacsng.h.
1832 CONFIG_SYS_SPI_MXC_WAIT
1833 Timeout for waiting until spi transfer completed.
1834 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1836 - FPGA Support: CONFIG_FPGA
1838 Enables FPGA subsystem.
1840 CONFIG_FPGA_<vendor>
1842 Enables support for specific chip vendors.
1845 CONFIG_FPGA_<family>
1847 Enables support for FPGA family.
1848 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1852 Specify the number of FPGA devices to support.
1854 CONFIG_SYS_FPGA_PROG_FEEDBACK
1856 Enable printing of hash marks during FPGA configuration.
1858 CONFIG_SYS_FPGA_CHECK_BUSY
1860 Enable checks on FPGA configuration interface busy
1861 status by the configuration function. This option
1862 will require a board or device specific function to
1867 If defined, a function that provides delays in the FPGA
1868 configuration driver.
1870 CONFIG_SYS_FPGA_CHECK_CTRLC
1871 Allow Control-C to interrupt FPGA configuration
1873 CONFIG_SYS_FPGA_CHECK_ERROR
1875 Check for configuration errors during FPGA bitfile
1876 loading. For example, abort during Virtex II
1877 configuration if the INIT_B line goes low (which
1878 indicated a CRC error).
1880 CONFIG_SYS_FPGA_WAIT_INIT
1882 Maximum time to wait for the INIT_B line to de-assert
1883 after PROB_B has been de-asserted during a Virtex II
1884 FPGA configuration sequence. The default time is 500
1887 CONFIG_SYS_FPGA_WAIT_BUSY
1889 Maximum time to wait for BUSY to de-assert during
1890 Virtex II FPGA configuration. The default is 5 ms.
1892 CONFIG_SYS_FPGA_WAIT_CONFIG
1894 Time to wait after FPGA configuration. The default is
1897 - Configuration Management:
1901 If defined, this string will be added to the U-Boot
1902 version information (U_BOOT_VERSION)
1904 - Vendor Parameter Protection:
1906 U-Boot considers the values of the environment
1907 variables "serial#" (Board Serial Number) and
1908 "ethaddr" (Ethernet Address) to be parameters that
1909 are set once by the board vendor / manufacturer, and
1910 protects these variables from casual modification by
1911 the user. Once set, these variables are read-only,
1912 and write or delete attempts are rejected. You can
1913 change this behaviour:
1915 If CONFIG_ENV_OVERWRITE is #defined in your config
1916 file, the write protection for vendor parameters is
1917 completely disabled. Anybody can change or delete
1920 Alternatively, if you define _both_ an ethaddr in the
1921 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1922 Ethernet address is installed in the environment,
1923 which can be changed exactly ONCE by the user. [The
1924 serial# is unaffected by this, i. e. it remains
1927 The same can be accomplished in a more flexible way
1928 for any variable by configuring the type of access
1929 to allow for those variables in the ".flags" variable
1930 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1935 Define this variable to enable the reservation of
1936 "protected RAM", i. e. RAM which is not overwritten
1937 by U-Boot. Define CONFIG_PRAM to hold the number of
1938 kB you want to reserve for pRAM. You can overwrite
1939 this default value by defining an environment
1940 variable "pram" to the number of kB you want to
1941 reserve. Note that the board info structure will
1942 still show the full amount of RAM. If pRAM is
1943 reserved, a new environment variable "mem" will
1944 automatically be defined to hold the amount of
1945 remaining RAM in a form that can be passed as boot
1946 argument to Linux, for instance like that:
1948 setenv bootargs ... mem=\${mem}
1951 This way you can tell Linux not to use this memory,
1952 either, which results in a memory region that will
1953 not be affected by reboots.
1955 *WARNING* If your board configuration uses automatic
1956 detection of the RAM size, you must make sure that
1957 this memory test is non-destructive. So far, the
1958 following board configurations are known to be
1961 IVMS8, IVML24, SPD8xx,
1962 HERMES, IP860, RPXlite, LWMON,
1965 - Access to physical memory region (> 4GB)
1966 Some basic support is provided for operations on memory not
1967 normally accessible to U-Boot - e.g. some architectures
1968 support access to more than 4GB of memory on 32-bit
1969 machines using physical address extension or similar.
1970 Define CONFIG_PHYSMEM to access this basic support, which
1971 currently only supports clearing the memory.
1974 CONFIG_NET_RETRY_COUNT
1976 This variable defines the number of retries for
1977 network operations like ARP, RARP, TFTP, or BOOTP
1978 before giving up the operation. If not defined, a
1979 default value of 5 is used.
1983 Timeout waiting for an ARP reply in milliseconds.
1987 Timeout in milliseconds used in NFS protocol.
1988 If you encounter "ERROR: Cannot umount" in nfs command,
1989 try longer timeout such as
1990 #define CONFIG_NFS_TIMEOUT 10000UL
1992 - Command Interpreter:
1993 CONFIG_SYS_PROMPT_HUSH_PS2
1995 This defines the secondary prompt string, which is
1996 printed when the command interpreter needs more input
1997 to complete a command. Usually "> ".
2001 In the current implementation, the local variables
2002 space and global environment variables space are
2003 separated. Local variables are those you define by
2004 simply typing `name=value'. To access a local
2005 variable later on, you have write `$name' or
2006 `${name}'; to execute the contents of a variable
2007 directly type `$name' at the command prompt.
2009 Global environment variables are those you use
2010 setenv/printenv to work with. To run a command stored
2011 in such a variable, you need to use the run command,
2012 and you must not use the '$' sign to access them.
2014 To store commands and special characters in a
2015 variable, please use double quotation marks
2016 surrounding the whole text of the variable, instead
2017 of the backslashes before semicolons and special
2020 - Command Line Editing and History:
2021 CONFIG_CMDLINE_PS_SUPPORT
2023 Enable support for changing the command prompt string
2024 at run-time. Only static string is supported so far.
2025 The string is obtained from environment variables PS1
2028 - Default Environment:
2029 CONFIG_EXTRA_ENV_SETTINGS
2031 Define this to contain any number of null terminated
2032 strings (variable = value pairs) that will be part of
2033 the default environment compiled into the boot image.
2035 For example, place something like this in your
2036 board's config file:
2038 #define CONFIG_EXTRA_ENV_SETTINGS \
2042 Warning: This method is based on knowledge about the
2043 internal format how the environment is stored by the
2044 U-Boot code. This is NOT an official, exported
2045 interface! Although it is unlikely that this format
2046 will change soon, there is no guarantee either.
2047 You better know what you are doing here.
2049 Note: overly (ab)use of the default environment is
2050 discouraged. Make sure to check other ways to preset
2051 the environment like the "source" command or the
2054 CONFIG_DELAY_ENVIRONMENT
2056 Normally the environment is loaded when the board is
2057 initialised so that it is available to U-Boot. This inhibits
2058 that so that the environment is not available until
2059 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2060 this is instead controlled by the value of
2061 /config/load-environment.
2063 - TFTP Fixed UDP Port:
2066 If this is defined, the environment variable tftpsrcp
2067 is used to supply the TFTP UDP source port value.
2068 If tftpsrcp isn't defined, the normal pseudo-random port
2069 number generator is used.
2071 Also, the environment variable tftpdstp is used to supply
2072 the TFTP UDP destination port value. If tftpdstp isn't
2073 defined, the normal port 69 is used.
2075 The purpose for tftpsrcp is to allow a TFTP server to
2076 blindly start the TFTP transfer using the pre-configured
2077 target IP address and UDP port. This has the effect of
2078 "punching through" the (Windows XP) firewall, allowing
2079 the remainder of the TFTP transfer to proceed normally.
2080 A better solution is to properly configure the firewall,
2081 but sometimes that is not allowed.
2083 CONFIG_STANDALONE_LOAD_ADDR
2085 This option defines a board specific value for the
2086 address where standalone program gets loaded, thus
2087 overwriting the architecture dependent default
2090 - Frame Buffer Address:
2093 Define CONFIG_FB_ADDR if you want to use specific
2094 address for frame buffer. This is typically the case
2095 when using a graphics controller has separate video
2096 memory. U-Boot will then place the frame buffer at
2097 the given address instead of dynamically reserving it
2098 in system RAM by calling lcd_setmem(), which grabs
2099 the memory for the frame buffer depending on the
2100 configured panel size.
2102 Please see board_init_f function.
2104 - Automatic software updates via TFTP server
2106 CONFIG_UPDATE_TFTP_CNT_MAX
2107 CONFIG_UPDATE_TFTP_MSEC_MAX
2109 These options enable and control the auto-update feature;
2110 for a more detailed description refer to doc/README.update.
2112 - MTD Support (mtdparts command, UBI support)
2113 CONFIG_MTD_UBI_WL_THRESHOLD
2114 This parameter defines the maximum difference between the highest
2115 erase counter value and the lowest erase counter value of eraseblocks
2116 of UBI devices. When this threshold is exceeded, UBI starts performing
2117 wear leveling by means of moving data from eraseblock with low erase
2118 counter to eraseblocks with high erase counter.
2120 The default value should be OK for SLC NAND flashes, NOR flashes and
2121 other flashes which have eraseblock life-cycle 100000 or more.
2122 However, in case of MLC NAND flashes which typically have eraseblock
2123 life-cycle less than 10000, the threshold should be lessened (e.g.,
2124 to 128 or 256, although it does not have to be power of 2).
2128 CONFIG_MTD_UBI_BEB_LIMIT
2129 This option specifies the maximum bad physical eraseblocks UBI
2130 expects on the MTD device (per 1024 eraseblocks). If the
2131 underlying flash does not admit of bad eraseblocks (e.g. NOR
2132 flash), this value is ignored.
2134 NAND datasheets often specify the minimum and maximum NVM
2135 (Number of Valid Blocks) for the flashes' endurance lifetime.
2136 The maximum expected bad eraseblocks per 1024 eraseblocks
2137 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2138 which gives 20 for most NANDs (MaxNVB is basically the total
2139 count of eraseblocks on the chip).
2141 To put it differently, if this value is 20, UBI will try to
2142 reserve about 1.9% of physical eraseblocks for bad blocks
2143 handling. And that will be 1.9% of eraseblocks on the entire
2144 NAND chip, not just the MTD partition UBI attaches. This means
2145 that if you have, say, a NAND flash chip admits maximum 40 bad
2146 eraseblocks, and it is split on two MTD partitions of the same
2147 size, UBI will reserve 40 eraseblocks when attaching a
2152 CONFIG_MTD_UBI_FASTMAP
2153 Fastmap is a mechanism which allows attaching an UBI device
2154 in nearly constant time. Instead of scanning the whole MTD device it
2155 only has to locate a checkpoint (called fastmap) on the device.
2156 The on-flash fastmap contains all information needed to attach
2157 the device. Using fastmap makes only sense on large devices where
2158 attaching by scanning takes long. UBI will not automatically install
2159 a fastmap on old images, but you can set the UBI parameter
2160 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2161 that fastmap-enabled images are still usable with UBI implementations
2162 without fastmap support. On typical flash devices the whole fastmap
2163 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2165 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2166 Set this parameter to enable fastmap automatically on images
2170 CONFIG_MTD_UBI_FM_DEBUG
2171 Enable UBI fastmap debug
2176 Enable building of SPL globally.
2179 LDSCRIPT for linking the SPL binary.
2181 CONFIG_SPL_MAX_FOOTPRINT
2182 Maximum size in memory allocated to the SPL, BSS included.
2183 When defined, the linker checks that the actual memory
2184 used by SPL from _start to __bss_end does not exceed it.
2185 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2186 must not be both defined at the same time.
2189 Maximum size of the SPL image (text, data, rodata, and
2190 linker lists sections), BSS excluded.
2191 When defined, the linker checks that the actual size does
2194 CONFIG_SPL_RELOC_TEXT_BASE
2195 Address to relocate to. If unspecified, this is equal to
2196 CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2198 CONFIG_SPL_BSS_START_ADDR
2199 Link address for the BSS within the SPL binary.
2201 CONFIG_SPL_BSS_MAX_SIZE
2202 Maximum size in memory allocated to the SPL BSS.
2203 When defined, the linker checks that the actual memory used
2204 by SPL from __bss_start to __bss_end does not exceed it.
2205 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2206 must not be both defined at the same time.
2209 Adress of the start of the stack SPL will use
2211 CONFIG_SPL_PANIC_ON_RAW_IMAGE
2212 When defined, SPL will panic() if the image it has
2213 loaded does not have a signature.
2214 Defining this is useful when code which loads images
2215 in SPL cannot guarantee that absolutely all read errors
2217 An example is the LPC32XX MLC NAND driver, which will
2218 consider that a completely unreadable NAND block is bad,
2219 and thus should be skipped silently.
2221 CONFIG_SPL_RELOC_STACK
2222 Adress of the start of the stack SPL will use after
2223 relocation. If unspecified, this is equal to
2226 CONFIG_SYS_SPL_MALLOC_START
2227 Starting address of the malloc pool used in SPL.
2228 When this option is set the full malloc is used in SPL and
2229 it is set up by spl_init() and before that, the simple malloc()
2230 can be used if CONFIG_SYS_MALLOC_F is defined.
2232 CONFIG_SYS_SPL_MALLOC_SIZE
2233 The size of the malloc pool used in SPL.
2236 Enable booting directly to an OS from SPL.
2237 See also: doc/README.falcon
2239 CONFIG_SPL_DISPLAY_PRINT
2240 For ARM, enable an optional function to print more information
2241 about the running system.
2243 CONFIG_SPL_INIT_MINIMAL
2244 Arch init code should be built for a very small image
2246 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2247 Partition on the MMC to load U-Boot from when the MMC is being
2250 CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2251 Sector to load kernel uImage from when MMC is being
2252 used in raw mode (for Falcon mode)
2254 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2255 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2256 Sector and number of sectors to load kernel argument
2257 parameters from when MMC is being used in raw mode
2260 CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2261 Partition on the MMC to load U-Boot from when the MMC is being
2264 CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2265 Filename to read to load U-Boot when reading from filesystem
2267 CONFIG_SPL_FS_LOAD_KERNEL_NAME
2268 Filename to read to load kernel uImage when reading
2269 from filesystem (for Falcon mode)
2271 CONFIG_SPL_FS_LOAD_ARGS_NAME
2272 Filename to read to load kernel argument parameters
2273 when reading from filesystem (for Falcon mode)
2275 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2276 Set this for NAND SPL on PPC mpc83xx targets, so that
2277 start.S waits for the rest of the SPL to load before
2278 continuing (the hardware starts execution after just
2279 loading the first page rather than the full 4K).
2281 CONFIG_SPL_SKIP_RELOCATE
2282 Avoid SPL relocation
2284 CONFIG_SPL_NAND_BASE
2285 Include nand_base.c in the SPL. Requires
2286 CONFIG_SPL_NAND_IDENT
2287 SPL uses the chip ID list to identify the NAND flash.
2288 Requires CONFIG_SPL_NAND_BASE.
2291 Support for a lightweight UBI (fastmap) scanner and
2294 CONFIG_SPL_NAND_RAW_ONLY
2295 Support to boot only raw u-boot.bin images. Use this only
2296 if you need to save space.
2298 CONFIG_SPL_COMMON_INIT_DDR
2299 Set for common ddr init with serial presence detect in
2302 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2303 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2304 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2305 CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2306 CONFIG_SYS_NAND_ECCBYTES
2307 Defines the size and behavior of the NAND that SPL uses
2310 CONFIG_SYS_NAND_U_BOOT_OFFS
2311 Location in NAND to read U-Boot from
2313 CONFIG_SYS_NAND_U_BOOT_DST
2314 Location in memory to load U-Boot to
2316 CONFIG_SYS_NAND_U_BOOT_SIZE
2317 Size of image to load
2319 CONFIG_SYS_NAND_U_BOOT_START
2320 Entry point in loaded image to jump to
2322 CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2323 Define this if you need to first read the OOB and then the
2324 data. This is used, for example, on davinci platforms.
2326 CONFIG_SPL_RAM_DEVICE
2327 Support for running image already present in ram, in SPL binary
2330 Image offset to which the SPL should be padded before appending
2331 the SPL payload. By default, this is defined as
2332 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2333 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2334 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2337 Final target image containing SPL and payload. Some SPLs
2338 use an arch-specific makefile fragment instead, for
2339 example if more than one image needs to be produced.
2341 CONFIG_SPL_FIT_PRINT
2342 Printing information about a FIT image adds quite a bit of
2343 code to SPL. So this is normally disabled in SPL. Use this
2344 option to re-enable it. This will affect the output of the
2345 bootm command when booting a FIT image.
2349 Enable building of TPL globally.
2352 Image offset to which the TPL should be padded before appending
2353 the TPL payload. By default, this is defined as
2354 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2355 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2356 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2358 - Interrupt support (PPC):
2360 There are common interrupt_init() and timer_interrupt()
2361 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2362 for CPU specific initialization. interrupt_init_cpu()
2363 should set decrementer_count to appropriate value. If
2364 CPU resets decrementer automatically after interrupt
2365 (ppc4xx) it should set decrementer_count to zero.
2366 timer_interrupt() calls timer_interrupt_cpu() for CPU
2367 specific handling. If board has watchdog / status_led
2368 / other_activity_monitor it works automatically from
2369 general timer_interrupt().
2372 Board initialization settings:
2373 ------------------------------
2375 During Initialization u-boot calls a number of board specific functions
2376 to allow the preparation of board specific prerequisites, e.g. pin setup
2377 before drivers are initialized. To enable these callbacks the
2378 following configuration macros have to be defined. Currently this is
2379 architecture specific, so please check arch/your_architecture/lib/board.c
2380 typically in board_init_f() and board_init_r().
2382 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2383 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2384 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
2385 - CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2387 Configuration Settings:
2388 -----------------------
2390 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2391 Optionally it can be defined to support 64-bit memory commands.
2393 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2394 undefine this when you're short of memory.
2396 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2397 width of the commands listed in the 'help' command output.
2399 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
2400 prompt for user input.
2402 - CONFIG_SYS_CBSIZE: Buffer size for input from the Console
2404 - CONFIG_SYS_PBSIZE: Buffer size for Console output
2406 - CONFIG_SYS_MAXARGS: max. Number of arguments accepted for monitor commands
2408 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2409 the application (usually a Linux kernel) when it is
2412 - CONFIG_SYS_BAUDRATE_TABLE:
2413 List of legal baudrate settings for this board.
2415 - CONFIG_SYS_MEM_RESERVE_SECURE
2416 Only implemented for ARMv8 for now.
2417 If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2418 is substracted from total RAM and won't be reported to OS.
2419 This memory can be used as secure memory. A variable
2420 gd->arch.secure_ram is used to track the location. In systems
2421 the RAM base is not zero, or RAM is divided into banks,
2422 this variable needs to be recalcuated to get the address.
2424 - CONFIG_SYS_MEM_TOP_HIDE:
2425 If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2426 this specified memory area will get subtracted from the top
2427 (end) of RAM and won't get "touched" at all by U-Boot. By
2428 fixing up gd->ram_size the Linux kernel should gets passed
2429 the now "corrected" memory size and won't touch it either.
2430 This should work for arch/ppc and arch/powerpc. Only Linux
2431 board ports in arch/powerpc with bootwrapper support that
2432 recalculate the memory size from the SDRAM controller setup
2433 will have to get fixed in Linux additionally.
2435 This option can be used as a workaround for the 440EPx/GRx
2436 CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2439 WARNING: Please make sure that this value is a multiple of
2440 the Linux page size (normally 4k). If this is not the case,
2441 then the end address of the Linux memory will be located at a
2442 non page size aligned address and this could cause major
2445 - CONFIG_SYS_LOADS_BAUD_CHANGE:
2446 Enable temporary baudrate change while serial download
2448 - CONFIG_SYS_SDRAM_BASE:
2449 Physical start address of SDRAM. _Must_ be 0 here.
2451 - CONFIG_SYS_FLASH_BASE:
2452 Physical start address of Flash memory.
2454 - CONFIG_SYS_MONITOR_BASE:
2455 Physical start address of boot monitor code (set by
2456 make config files to be same as the text base address
2457 (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2458 CONFIG_SYS_FLASH_BASE when booting from flash.
2460 - CONFIG_SYS_MONITOR_LEN:
2461 Size of memory reserved for monitor code, used to
2462 determine _at_compile_time_ (!) if the environment is
2463 embedded within the U-Boot image, or in a separate
2466 - CONFIG_SYS_MALLOC_LEN:
2467 Size of DRAM reserved for malloc() use.
2469 - CONFIG_SYS_MALLOC_F_LEN
2470 Size of the malloc() pool for use before relocation. If
2471 this is defined, then a very simple malloc() implementation
2472 will become available before relocation. The address is just
2473 below the global data, and the stack is moved down to make
2476 This feature allocates regions with increasing addresses
2477 within the region. calloc() is supported, but realloc()
2478 is not available. free() is supported but does nothing.
2479 The memory will be freed (or in fact just forgotten) when
2480 U-Boot relocates itself.
2482 - CONFIG_SYS_MALLOC_SIMPLE
2483 Provides a simple and small malloc() and calloc() for those
2484 boards which do not use the full malloc in SPL (which is
2485 enabled with CONFIG_SYS_SPL_MALLOC_START).
2487 - CONFIG_SYS_NONCACHED_MEMORY:
2488 Size of non-cached memory area. This area of memory will be
2489 typically located right below the malloc() area and mapped
2490 uncached in the MMU. This is useful for drivers that would
2491 otherwise require a lot of explicit cache maintenance. For
2492 some drivers it's also impossible to properly maintain the
2493 cache. For example if the regions that need to be flushed
2494 are not a multiple of the cache-line size, *and* padding
2495 cannot be allocated between the regions to align them (i.e.
2496 if the HW requires a contiguous array of regions, and the
2497 size of each region is not cache-aligned), then a flush of
2498 one region may result in overwriting data that hardware has
2499 written to another region in the same cache-line. This can
2500 happen for example in network drivers where descriptors for
2501 buffers are typically smaller than the CPU cache-line (e.g.
2502 16 bytes vs. 32 or 64 bytes).
2504 Non-cached memory is only supported on 32-bit ARM at present.
2506 - CONFIG_SYS_BOOTM_LEN:
2507 Normally compressed uImages are limited to an
2508 uncompressed size of 8 MBytes. If this is not enough,
2509 you can define CONFIG_SYS_BOOTM_LEN in your board config file
2510 to adjust this setting to your needs.
2512 - CONFIG_SYS_BOOTMAPSZ:
2513 Maximum size of memory mapped by the startup code of
2514 the Linux kernel; all data that must be processed by
2515 the Linux kernel (bd_info, boot arguments, FDT blob if
2516 used) must be put below this limit, unless "bootm_low"
2517 environment variable is defined and non-zero. In such case
2518 all data for the Linux kernel must be between "bootm_low"
2519 and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
2520 variable "bootm_mapsize" will override the value of
2521 CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
2522 then the value in "bootm_size" will be used instead.
2524 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
2525 Enable initrd_high functionality. If defined then the
2526 initrd_high feature is enabled and the bootm ramdisk subcommand
2529 - CONFIG_SYS_BOOT_GET_CMDLINE:
2530 Enables allocating and saving kernel cmdline in space between
2531 "bootm_low" and "bootm_low" + BOOTMAPSZ.
2533 - CONFIG_SYS_BOOT_GET_KBD:
2534 Enables allocating and saving a kernel copy of the bd_info in
2535 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2537 - CONFIG_SYS_MAX_FLASH_BANKS:
2538 Max number of Flash memory banks
2540 - CONFIG_SYS_MAX_FLASH_SECT:
2541 Max number of sectors on a Flash chip
2543 - CONFIG_SYS_FLASH_ERASE_TOUT:
2544 Timeout for Flash erase operations (in ms)
2546 - CONFIG_SYS_FLASH_WRITE_TOUT:
2547 Timeout for Flash write operations (in ms)
2549 - CONFIG_SYS_FLASH_LOCK_TOUT
2550 Timeout for Flash set sector lock bit operation (in ms)
2552 - CONFIG_SYS_FLASH_UNLOCK_TOUT
2553 Timeout for Flash clear lock bits operation (in ms)
2555 - CONFIG_SYS_FLASH_PROTECTION
2556 If defined, hardware flash sectors protection is used
2557 instead of U-Boot software protection.
2559 - CONFIG_SYS_DIRECT_FLASH_TFTP:
2561 Enable TFTP transfers directly to flash memory;
2562 without this option such a download has to be
2563 performed in two steps: (1) download to RAM, and (2)
2564 copy from RAM to flash.
2566 The two-step approach is usually more reliable, since
2567 you can check if the download worked before you erase
2568 the flash, but in some situations (when system RAM is
2569 too limited to allow for a temporary copy of the
2570 downloaded image) this option may be very useful.
2572 - CONFIG_SYS_FLASH_CFI:
2573 Define if the flash driver uses extra elements in the
2574 common flash structure for storing flash geometry.
2576 - CONFIG_FLASH_CFI_DRIVER
2577 This option also enables the building of the cfi_flash driver
2578 in the drivers directory
2580 - CONFIG_FLASH_CFI_MTD
2581 This option enables the building of the cfi_mtd driver
2582 in the drivers directory. The driver exports CFI flash
2585 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2586 Use buffered writes to flash.
2588 - CONFIG_FLASH_SPANSION_S29WS_N
2589 s29ws-n MirrorBit flash has non-standard addresses for buffered
2592 - CONFIG_SYS_FLASH_QUIET_TEST
2593 If this option is defined, the common CFI flash doesn't
2594 print it's warning upon not recognized FLASH banks. This
2595 is useful, if some of the configured banks are only
2596 optionally available.
2598 - CONFIG_FLASH_SHOW_PROGRESS
2599 If defined (must be an integer), print out countdown
2600 digits and dots. Recommended value: 45 (9..1) for 80
2601 column displays, 15 (3..1) for 40 column displays.
2603 - CONFIG_FLASH_VERIFY
2604 If defined, the content of the flash (destination) is compared
2605 against the source after the write operation. An error message
2606 will be printed when the contents are not identical.
2607 Please note that this option is useless in nearly all cases,
2608 since such flash programming errors usually are detected earlier
2609 while unprotecting/erasing/programming. Please only enable
2610 this option if you really know what you are doing.
2612 - CONFIG_SYS_RX_ETH_BUFFER:
2613 Defines the number of Ethernet receive buffers. On some
2614 Ethernet controllers it is recommended to set this value
2615 to 8 or even higher (EEPRO100 or 405 EMAC), since all
2616 buffers can be full shortly after enabling the interface
2617 on high Ethernet traffic.
2618 Defaults to 4 if not defined.
2620 - CONFIG_ENV_MAX_ENTRIES
2622 Maximum number of entries in the hash table that is used
2623 internally to store the environment settings. The default
2624 setting is supposed to be generous and should work in most
2625 cases. This setting can be used to tune behaviour; see
2626 lib/hashtable.c for details.
2628 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2629 - CONFIG_ENV_FLAGS_LIST_STATIC
2630 Enable validation of the values given to environment variables when
2631 calling env set. Variables can be restricted to only decimal,
2632 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
2633 the variables can also be restricted to IP address or MAC address.
2635 The format of the list is:
2636 type_attribute = [s|d|x|b|i|m]
2637 access_attribute = [a|r|o|c]
2638 attributes = type_attribute[access_attribute]
2639 entry = variable_name[:attributes]
2642 The type attributes are:
2643 s - String (default)
2646 b - Boolean ([1yYtT|0nNfF])
2650 The access attributes are:
2656 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2657 Define this to a list (string) to define the ".flags"
2658 environment variable in the default or embedded environment.
2660 - CONFIG_ENV_FLAGS_LIST_STATIC
2661 Define this to a list (string) to define validation that
2662 should be done if an entry is not found in the ".flags"
2663 environment variable. To override a setting in the static
2664 list, simply add an entry for the same variable name to the
2667 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2668 regular expression. This allows multiple variables to define the same
2669 flags without explicitly listing them for each variable.
2671 The following definitions that deal with the placement and management
2672 of environment data (variable area); in general, we support the
2673 following configurations:
2675 - CONFIG_BUILD_ENVCRC:
2677 Builds up envcrc with the target environment so that external utils
2678 may easily extract it and embed it in final U-Boot images.
2680 BE CAREFUL! The first access to the environment happens quite early
2681 in U-Boot initialization (when we try to get the setting of for the
2682 console baudrate). You *MUST* have mapped your NVRAM area then, or
2685 Please note that even with NVRAM we still use a copy of the
2686 environment in RAM: we could work on NVRAM directly, but we want to
2687 keep settings there always unmodified except somebody uses "saveenv"
2688 to save the current settings.
2690 BE CAREFUL! For some special cases, the local device can not use
2691 "saveenv" command. For example, the local device will get the
2692 environment stored in a remote NOR flash by SRIO or PCIE link,
2693 but it can not erase, write this NOR flash by SRIO or PCIE interface.
2695 - CONFIG_NAND_ENV_DST
2697 Defines address in RAM to which the nand_spl code should copy the
2698 environment. If redundant environment is used, it will be copied to
2699 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2701 Please note that the environment is read-only until the monitor
2702 has been relocated to RAM and a RAM copy of the environment has been
2703 created; also, when using EEPROM you will have to use env_get_f()
2704 until then to read environment variables.
2706 The environment is protected by a CRC32 checksum. Before the monitor
2707 is relocated into RAM, as a result of a bad CRC you will be working
2708 with the compiled-in default environment - *silently*!!! [This is
2709 necessary, because the first environment variable we need is the
2710 "baudrate" setting for the console - if we have a bad CRC, we don't
2711 have any device yet where we could complain.]
2713 Note: once the monitor has been relocated, then it will complain if
2714 the default environment is used; a new CRC is computed as soon as you
2715 use the "saveenv" command to store a valid environment.
2717 - CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2718 Echo the inverted Ethernet link state to the fault LED.
2720 Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2721 also needs to be defined.
2723 - CONFIG_SYS_FAULT_MII_ADDR:
2724 MII address of the PHY to check for the Ethernet link state.
2726 - CONFIG_NS16550_MIN_FUNCTIONS:
2727 Define this if you desire to only have use of the NS16550_init
2728 and NS16550_putc functions for the serial driver located at
2729 drivers/serial/ns16550.c. This option is useful for saving
2730 space for already greatly restricted images, including but not
2731 limited to NAND_SPL configurations.
2733 - CONFIG_DISPLAY_BOARDINFO
2734 Display information about the board that U-Boot is running on
2735 when U-Boot starts up. The board function checkboard() is called
2738 - CONFIG_DISPLAY_BOARDINFO_LATE
2739 Similar to the previous option, but display this information
2740 later, once stdio is running and output goes to the LCD, if
2743 - CONFIG_BOARD_SIZE_LIMIT:
2744 Maximum size of the U-Boot image. When defined, the
2745 build system checks that the actual size does not
2748 Low Level (hardware related) configuration options:
2749 ---------------------------------------------------
2751 - CONFIG_SYS_CACHELINE_SIZE:
2752 Cache Line Size of the CPU.
2754 - CONFIG_SYS_CCSRBAR_DEFAULT:
2755 Default (power-on reset) physical address of CCSR on Freescale
2758 - CONFIG_SYS_CCSRBAR:
2759 Virtual address of CCSR. On a 32-bit build, this is typically
2760 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2762 - CONFIG_SYS_CCSRBAR_PHYS:
2763 Physical address of CCSR. CCSR can be relocated to a new
2764 physical address, if desired. In this case, this macro should
2765 be set to that address. Otherwise, it should be set to the
2766 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
2767 is typically relocated on 36-bit builds. It is recommended
2768 that this macro be defined via the _HIGH and _LOW macros:
2770 #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2771 * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2773 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2774 Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
2775 either 0 (32-bit build) or 0xF (36-bit build). This macro is
2776 used in assembly code, so it must not contain typecasts or
2777 integer size suffixes (e.g. "ULL").
2779 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
2780 Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
2781 used in assembly code, so it must not contain typecasts or
2782 integer size suffixes (e.g. "ULL").
2784 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2785 If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2786 forced to a value that ensures that CCSR is not relocated.
2789 Most IDE controllers were designed to be connected with PCI
2790 interface. Only few of them were designed for AHB interface.
2791 When software is doing ATA command and data transfer to
2792 IDE devices through IDE-AHB controller, some additional
2793 registers accessing to these kind of IDE-AHB controller
2796 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
2797 DO NOT CHANGE unless you know exactly what you're
2798 doing! (11-4) [MPC8xx systems only]
2800 - CONFIG_SYS_INIT_RAM_ADDR:
2802 Start address of memory area that can be used for
2803 initial data and stack; please note that this must be
2804 writable memory that is working WITHOUT special
2805 initialization, i. e. you CANNOT use normal RAM which
2806 will become available only after programming the
2807 memory controller and running certain initialization
2810 U-Boot uses the following memory types:
2811 - MPC8xx: IMMR (internal memory of the CPU)
2813 - CONFIG_SYS_GBL_DATA_OFFSET:
2815 Offset of the initial data structure in the memory
2816 area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2817 CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2818 data is located at the end of the available space
2819 (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2820 GENERATED_GBL_DATA_SIZE), and the initial stack is just
2821 below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2822 CONFIG_SYS_GBL_DATA_OFFSET) downward.
2825 On the MPC824X (or other systems that use the data
2826 cache for initial memory) the address chosen for
2827 CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2828 point to an otherwise UNUSED address space between
2829 the top of RAM and the start of the PCI space.
2831 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
2833 - CONFIG_SYS_OR_TIMING_SDRAM:
2836 - CONFIG_SYS_MAMR_PTA:
2837 periodic timer for refresh
2839 - FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2840 CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2841 CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2842 CONFIG_SYS_BR1_PRELIM:
2843 Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2845 - SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2846 CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2847 CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2848 Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2850 - CONFIG_PCI_ENUM_ONLY
2851 Only scan through and get the devices on the buses.
2852 Don't do any setup work, presumably because someone or
2853 something has already done it, and we don't need to do it
2854 a second time. Useful for platforms that are pre-booted
2855 by coreboot or similar.
2857 - CONFIG_PCI_INDIRECT_BRIDGE:
2858 Enable support for indirect PCI bridges.
2861 Chip has SRIO or not
2864 Board has SRIO 1 port available
2867 Board has SRIO 2 port available
2869 - CONFIG_SRIO_PCIE_BOOT_MASTER
2870 Board can support master function for Boot from SRIO and PCIE
2872 - CONFIG_SYS_SRIOn_MEM_VIRT:
2873 Virtual Address of SRIO port 'n' memory region
2875 - CONFIG_SYS_SRIOn_MEM_PHYxS:
2876 Physical Address of SRIO port 'n' memory region
2878 - CONFIG_SYS_SRIOn_MEM_SIZE:
2879 Size of SRIO port 'n' memory region
2881 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
2882 Defined to tell the NAND controller that the NAND chip is using
2884 Not all NAND drivers use this symbol.
2885 Example of drivers that use it:
2886 - drivers/mtd/nand/raw/ndfc.c
2887 - drivers/mtd/nand/raw/mxc_nand.c
2889 - CONFIG_SYS_NDFC_EBC0_CFG
2890 Sets the EBC0_CFG register for the NDFC. If not defined
2891 a default value will be used.
2894 Get DDR timing information from an I2C EEPROM. Common
2895 with pluggable memory modules such as SODIMMs
2898 I2C address of the SPD EEPROM
2900 - CONFIG_SYS_SPD_BUS_NUM
2901 If SPD EEPROM is on an I2C bus other than the first
2902 one, specify here. Note that the value must resolve
2903 to something your driver can deal with.
2905 - CONFIG_SYS_DDR_RAW_TIMING
2906 Get DDR timing information from other than SPD. Common with
2907 soldered DDR chips onboard without SPD. DDR raw timing
2908 parameters are extracted from datasheet and hard-coded into
2909 header files or board specific files.
2911 - CONFIG_FSL_DDR_INTERACTIVE
2912 Enable interactive DDR debugging. See doc/README.fsl-ddr.
2914 - CONFIG_FSL_DDR_SYNC_REFRESH
2915 Enable sync of refresh for multiple controllers.
2917 - CONFIG_FSL_DDR_BIST
2918 Enable built-in memory test for Freescale DDR controllers.
2920 - CONFIG_SYS_83XX_DDR_USES_CS0
2921 Only for 83xx systems. If specified, then DDR should
2922 be configured using CS0 and CS1 instead of CS2 and CS3.
2925 Enable RMII mode for all FECs.
2926 Note that this is a global option, we can't
2927 have one FEC in standard MII mode and another in RMII mode.
2929 - CONFIG_CRC32_VERIFY
2930 Add a verify option to the crc32 command.
2933 => crc32 -v <address> <count> <crc32>
2935 Where address/count indicate a memory area
2936 and crc32 is the correct crc32 which the
2940 Add the "loopw" memory command. This only takes effect if
2941 the memory commands are activated globally (CONFIG_CMD_MEMORY).
2943 - CONFIG_CMD_MX_CYCLIC
2944 Add the "mdc" and "mwc" memory commands. These are cyclic
2949 This command will print 4 bytes (10,11,12,13) each 500 ms.
2951 => mwc.l 100 12345678 10
2952 This command will write 12345678 to address 100 all 10 ms.
2954 This only takes effect if the memory commands are activated
2955 globally (CONFIG_CMD_MEMORY).
2957 - CONFIG_SKIP_LOWLEVEL_INIT
2958 [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
2959 low level initializations (like setting up the memory
2960 controller) are omitted and/or U-Boot does not
2961 relocate itself into RAM.
2963 Normally this variable MUST NOT be defined. The only
2964 exception is when U-Boot is loaded (to RAM) by some
2965 other boot loader or by a debugger which performs
2966 these initializations itself.
2968 - CONFIG_SKIP_LOWLEVEL_INIT_ONLY
2969 [ARM926EJ-S only] This allows just the call to lowlevel_init()
2970 to be skipped. The normal CP15 init (such as enabling the
2971 instruction cache) is still performed.
2974 Set when the currently-running compilation is for an artifact
2975 that will end up in the SPL (as opposed to the TPL or U-Boot
2976 proper). Code that needs stage-specific behavior should check
2980 Set when the currently-running compilation is for an artifact
2981 that will end up in the TPL (as opposed to the SPL or U-Boot
2982 proper). Code that needs stage-specific behavior should check
2985 - CONFIG_SYS_MPC85XX_NO_RESETVEC
2986 Only for 85xx systems. If this variable is specified, the section
2987 .resetvec is not kept and the section .bootpg is placed in the
2988 previous 4k of the .text section.
2990 - CONFIG_ARCH_MAP_SYSMEM
2991 Generally U-Boot (and in particular the md command) uses
2992 effective address. It is therefore not necessary to regard
2993 U-Boot address as virtual addresses that need to be translated
2994 to physical addresses. However, sandbox requires this, since
2995 it maintains its own little RAM buffer which contains all
2996 addressable memory. This option causes some memory accesses
2997 to be mapped through map_sysmem() / unmap_sysmem().
2999 - CONFIG_X86_RESET_VECTOR
3000 If defined, the x86 reset vector code is included. This is not
3001 needed when U-Boot is running from Coreboot.
3003 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3004 Option to disable subpage write in NAND driver
3005 driver that uses this:
3006 drivers/mtd/nand/raw/davinci_nand.c
3008 Freescale QE/FMAN Firmware Support:
3009 -----------------------------------
3011 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3012 loading of "firmware", which is encoded in the QE firmware binary format.
3013 This firmware often needs to be loaded during U-Boot booting, so macros
3014 are used to identify the storage device (NOR flash, SPI, etc) and the address
3017 - CONFIG_SYS_FMAN_FW_ADDR
3018 The address in the storage device where the FMAN microcode is located. The
3019 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3022 - CONFIG_SYS_QE_FW_ADDR
3023 The address in the storage device where the QE microcode is located. The
3024 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3027 - CONFIG_SYS_QE_FMAN_FW_LENGTH
3028 The maximum possible size of the firmware. The firmware binary format
3029 has a field that specifies the actual size of the firmware, but it
3030 might not be possible to read any part of the firmware unless some
3031 local storage is allocated to hold the entire firmware first.
3033 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
3034 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3035 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
3036 virtual address in NOR flash.
3038 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
3039 Specifies that QE/FMAN firmware is located in NAND flash.
3040 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3042 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
3043 Specifies that QE/FMAN firmware is located on the primary SD/MMC
3044 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3046 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3047 Specifies that QE/FMAN firmware is located in the remote (master)
3048 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3049 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3050 window->master inbound window->master LAW->the ucode address in
3051 master's memory space.
3053 Freescale Layerscape Management Complex Firmware Support:
3054 ---------------------------------------------------------
3055 The Freescale Layerscape Management Complex (MC) supports the loading of
3057 This firmware often needs to be loaded during U-Boot booting, so macros
3058 are used to identify the storage device (NOR flash, SPI, etc) and the address
3061 - CONFIG_FSL_MC_ENET
3062 Enable the MC driver for Layerscape SoCs.
3064 Freescale Layerscape Debug Server Support:
3065 -------------------------------------------
3066 The Freescale Layerscape Debug Server Support supports the loading of
3067 "Debug Server firmware" and triggering SP boot-rom.
3068 This firmware often needs to be loaded during U-Boot booting.
3070 - CONFIG_SYS_MC_RSV_MEM_ALIGN
3071 Define alignment of reserved memory MC requires
3076 In order to achieve reproducible builds, timestamps used in the U-Boot build
3077 process have to be set to a fixed value.
3079 This is done using the SOURCE_DATE_EPOCH environment variable.
3080 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3081 option for U-Boot or an environment variable in U-Boot.
3083 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3085 Building the Software:
3086 ======================
3088 Building U-Boot has been tested in several native build environments
3089 and in many different cross environments. Of course we cannot support
3090 all possibly existing versions of cross development tools in all
3091 (potentially obsolete) versions. In case of tool chain problems we
3092 recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3093 which is extensively used to build and test U-Boot.
3095 If you are not using a native environment, it is assumed that you
3096 have GNU cross compiling tools available in your path. In this case,
3097 you must set the environment variable CROSS_COMPILE in your shell.
3098 Note that no changes to the Makefile or any other source files are
3099 necessary. For example using the ELDK on a 4xx CPU, please enter:
3101 $ CROSS_COMPILE=ppc_4xx-
3102 $ export CROSS_COMPILE
3104 U-Boot is intended to be simple to build. After installing the
3105 sources you must configure U-Boot for one specific board type. This
3110 where "NAME_defconfig" is the name of one of the existing configu-
3111 rations; see configs/*_defconfig for supported names.
3113 Note: for some boards special configuration names may exist; check if
3114 additional information is available from the board vendor; for
3115 instance, the TQM823L systems are available without (standard)
3116 or with LCD support. You can select such additional "features"
3117 when choosing the configuration, i. e.
3119 make TQM823L_defconfig
3120 - will configure for a plain TQM823L, i. e. no LCD support
3122 make TQM823L_LCD_defconfig
3123 - will configure for a TQM823L with U-Boot console on LCD
3128 Finally, type "make all", and you should get some working U-Boot
3129 images ready for download to / installation on your system:
3131 - "u-boot.bin" is a raw binary image
3132 - "u-boot" is an image in ELF binary format
3133 - "u-boot.srec" is in Motorola S-Record format
3135 By default the build is performed locally and the objects are saved
3136 in the source directory. One of the two methods can be used to change
3137 this behavior and build U-Boot to some external directory:
3139 1. Add O= to the make command line invocations:
3141 make O=/tmp/build distclean
3142 make O=/tmp/build NAME_defconfig
3143 make O=/tmp/build all
3145 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
3147 export KBUILD_OUTPUT=/tmp/build
3152 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3155 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3156 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3157 For example to treat all compiler warnings as errors:
3159 make KCFLAGS=-Werror
3161 Please be aware that the Makefiles assume you are using GNU make, so
3162 for instance on NetBSD you might need to use "gmake" instead of
3166 If the system board that you have is not listed, then you will need
3167 to port U-Boot to your hardware platform. To do this, follow these
3170 1. Create a new directory to hold your board specific code. Add any
3171 files you need. In your board directory, you will need at least
3172 the "Makefile" and a "<board>.c".
3173 2. Create a new configuration file "include/configs/<board>.h" for
3175 3. If you're porting U-Boot to a new CPU, then also create a new
3176 directory to hold your CPU specific code. Add any files you need.
3177 4. Run "make <board>_defconfig" with your new name.
3178 5. Type "make", and you should get a working "u-boot.srec" file
3179 to be installed on your target system.
3180 6. Debug and solve any problems that might arise.
3181 [Of course, this last step is much harder than it sounds.]
3184 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3185 ==============================================================
3187 If you have modified U-Boot sources (for instance added a new board
3188 or support for new devices, a new CPU, etc.) you are expected to
3189 provide feedback to the other developers. The feedback normally takes
3190 the form of a "patch", i.e. a context diff against a certain (latest
3191 official or latest in the git repository) version of U-Boot sources.
3193 But before you submit such a patch, please verify that your modifi-
3194 cation did not break existing code. At least make sure that *ALL* of
3195 the supported boards compile WITHOUT ANY compiler warnings. To do so,
3196 just run the buildman script (tools/buildman/buildman), which will
3197 configure and build U-Boot for ALL supported system. Be warned, this
3198 will take a while. Please see the buildman README, or run 'buildman -H'
3202 See also "U-Boot Porting Guide" below.
3205 Monitor Commands - Overview:
3206 ============================
3208 go - start application at address 'addr'
3209 run - run commands in an environment variable
3210 bootm - boot application image from memory
3211 bootp - boot image via network using BootP/TFTP protocol
3212 bootz - boot zImage from memory
3213 tftpboot- boot image via network using TFTP protocol
3214 and env variables "ipaddr" and "serverip"
3215 (and eventually "gatewayip")
3216 tftpput - upload a file via network using TFTP protocol
3217 rarpboot- boot image via network using RARP/TFTP protocol
3218 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
3219 loads - load S-Record file over serial line
3220 loadb - load binary file over serial line (kermit mode)
3222 mm - memory modify (auto-incrementing)
3223 nm - memory modify (constant address)
3224 mw - memory write (fill)
3227 cmp - memory compare
3228 crc32 - checksum calculation
3229 i2c - I2C sub-system
3230 sspi - SPI utility commands
3231 base - print or set address offset
3232 printenv- print environment variables
3233 setenv - set environment variables
3234 saveenv - save environment variables to persistent storage
3235 protect - enable or disable FLASH write protection
3236 erase - erase FLASH memory
3237 flinfo - print FLASH memory information
3238 nand - NAND memory operations (see doc/README.nand)
3239 bdinfo - print Board Info structure
3240 iminfo - print header information for application image
3241 coninfo - print console devices and informations
3242 ide - IDE sub-system
3243 loop - infinite loop on address range
3244 loopw - infinite write loop on address range
3245 mtest - simple RAM test
3246 icache - enable or disable instruction cache
3247 dcache - enable or disable data cache
3248 reset - Perform RESET of the CPU
3249 echo - echo args to console
3250 version - print monitor version
3251 help - print online help
3252 ? - alias for 'help'
3255 Monitor Commands - Detailed Description:
3256 ========================================
3260 For now: just type "help <command>".
3263 Environment Variables:
3264 ======================
3266 U-Boot supports user configuration using Environment Variables which
3267 can be made persistent by saving to Flash memory.
3269 Environment Variables are set using "setenv", printed using
3270 "printenv", and saved to Flash using "saveenv". Using "setenv"
3271 without a value can be used to delete a variable from the
3272 environment. As long as you don't save the environment you are
3273 working with an in-memory copy. In case the Flash area containing the
3274 environment is erased by accident, a default environment is provided.
3276 Some configuration options can be set using Environment Variables.
3278 List of environment variables (most likely not complete):
3280 baudrate - see CONFIG_BAUDRATE
3282 bootdelay - see CONFIG_BOOTDELAY
3284 bootcmd - see CONFIG_BOOTCOMMAND
3286 bootargs - Boot arguments when booting an RTOS image
3288 bootfile - Name of the image to load with TFTP
3290 bootm_low - Memory range available for image processing in the bootm
3291 command can be restricted. This variable is given as
3292 a hexadecimal number and defines lowest address allowed
3293 for use by the bootm command. See also "bootm_size"
3294 environment variable. Address defined by "bootm_low" is
3295 also the base of the initial memory mapping for the Linux
3296 kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3299 bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3300 This variable is given as a hexadecimal number and it
3301 defines the size of the memory region starting at base
3302 address bootm_low that is accessible by the Linux kernel
3303 during early boot. If unset, CONFIG_SYS_BOOTMAPSZ is used
3304 as the default value if it is defined, and bootm_size is
3307 bootm_size - Memory range available for image processing in the bootm
3308 command can be restricted. This variable is given as
3309 a hexadecimal number and defines the size of the region
3310 allowed for use by the bootm command. See also "bootm_low"
3311 environment variable.
3313 bootstopkeysha256, bootdelaykey, bootstopkey - See README.autoboot
3315 updatefile - Location of the software update file on a TFTP server, used
3316 by the automatic software update feature. Please refer to
3317 documentation in doc/README.update for more details.
3319 autoload - if set to "no" (any string beginning with 'n'),
3320 "bootp" will just load perform a lookup of the
3321 configuration from the BOOTP server, but not try to
3322 load any image using TFTP
3324 autostart - if set to "yes", an image loaded using the "bootp",
3325 "rarpboot", "tftpboot" or "diskboot" commands will
3326 be automatically started (by internally calling
3329 If set to "no", a standalone image passed to the
3330 "bootm" command will be copied to the load address
3331 (and eventually uncompressed), but NOT be started.
3332 This can be used to load and uncompress arbitrary
3335 fdt_high - if set this restricts the maximum address that the
3336 flattened device tree will be copied into upon boot.
3337 For example, if you have a system with 1 GB memory
3338 at physical address 0x10000000, while Linux kernel
3339 only recognizes the first 704 MB as low memory, you
3340 may need to set fdt_high as 0x3C000000 to have the
3341 device tree blob be copied to the maximum address
3342 of the 704 MB low memory, so that Linux kernel can
3343 access it during the boot procedure.
3345 If this is set to the special value 0xFFFFFFFF then
3346 the fdt will not be copied at all on boot. For this
3347 to work it must reside in writable memory, have
3348 sufficient padding on the end of it for u-boot to
3349 add the information it needs into it, and the memory
3350 must be accessible by the kernel.
3352 fdtcontroladdr- if set this is the address of the control flattened
3353 device tree used by U-Boot when CONFIG_OF_CONTROL is
3356 i2cfast - (PPC405GP|PPC405EP only)
3357 if set to 'y' configures Linux I2C driver for fast
3358 mode (400kHZ). This environment variable is used in
3359 initialization code. So, for changes to be effective
3360 it must be saved and board must be reset.
3362 initrd_high - restrict positioning of initrd images:
3363 If this variable is not set, initrd images will be
3364 copied to the highest possible address in RAM; this
3365 is usually what you want since it allows for
3366 maximum initrd size. If for some reason you want to
3367 make sure that the initrd image is loaded below the
3368 CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3369 variable to a value of "no" or "off" or "0".
3370 Alternatively, you can set it to a maximum upper
3371 address to use (U-Boot will still check that it
3372 does not overwrite the U-Boot stack and data).
3374 For instance, when you have a system with 16 MB
3375 RAM, and want to reserve 4 MB from use by Linux,
3376 you can do this by adding "mem=12M" to the value of
3377 the "bootargs" variable. However, now you must make
3378 sure that the initrd image is placed in the first
3379 12 MB as well - this can be done with
3381 setenv initrd_high 00c00000
3383 If you set initrd_high to 0xFFFFFFFF, this is an
3384 indication to U-Boot that all addresses are legal
3385 for the Linux kernel, including addresses in flash
3386 memory. In this case U-Boot will NOT COPY the
3387 ramdisk at all. This may be useful to reduce the
3388 boot time on your system, but requires that this
3389 feature is supported by your Linux kernel.
3391 ipaddr - IP address; needed for tftpboot command
3393 loadaddr - Default load address for commands like "bootp",
3394 "rarpboot", "tftpboot", "loadb" or "diskboot"
3396 loads_echo - see CONFIG_LOADS_ECHO
3398 serverip - TFTP server IP address; needed for tftpboot command
3400 bootretry - see CONFIG_BOOT_RETRY_TIME
3402 bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR
3404 bootstopkey - see CONFIG_AUTOBOOT_STOP_STR
3406 ethprime - controls which interface is used first.
3408 ethact - controls which interface is currently active.
3409 For example you can do the following
3411 => setenv ethact FEC
3412 => ping 192.168.0.1 # traffic sent on FEC
3413 => setenv ethact SCC
3414 => ping 10.0.0.1 # traffic sent on SCC
3416 ethrotate - When set to "no" U-Boot does not go through all
3417 available network interfaces.
3418 It just stays at the currently selected interface.
3420 netretry - When set to "no" each network operation will
3421 either succeed or fail without retrying.
3422 When set to "once" the network operation will
3423 fail when all the available network interfaces
3424 are tried once without success.
3425 Useful on scripts which control the retry operation
3428 npe_ucode - set load address for the NPE microcode
3430 silent_linux - If set then Linux will be told to boot silently, by
3431 changing the console to be empty. If "yes" it will be
3432 made silent. If "no" it will not be made silent. If
3433 unset, then it will be made silent if the U-Boot console
3436 tftpsrcp - If this is set, the value is used for TFTP's
3439 tftpdstp - If this is set, the value is used for TFTP's UDP
3440 destination port instead of the Well Know Port 69.
3442 tftpblocksize - Block size to use for TFTP transfers; if not set,
3443 we use the TFTP server's default block size
3445 tftptimeout - Retransmission timeout for TFTP packets (in milli-
3446 seconds, minimum value is 1000 = 1 second). Defines
3447 when a packet is considered to be lost so it has to
3448 be retransmitted. The default is 5000 = 5 seconds.
3449 Lowering this value may make downloads succeed
3450 faster in networks with high packet loss rates or
3451 with unreliable TFTP servers.
3453 tftptimeoutcountmax - maximum count of TFTP timeouts (no
3454 unit, minimum value = 0). Defines how many timeouts
3455 can happen during a single file transfer before that
3456 transfer is aborted. The default is 10, and 0 means
3457 'no timeouts allowed'. Increasing this value may help
3458 downloads succeed with high packet loss rates, or with
3459 unreliable TFTP servers or client hardware.
3461 vlan - When set to a value < 4095 the traffic over
3462 Ethernet is encapsulated/received over 802.1q
3465 bootpretryperiod - Period during which BOOTP/DHCP sends retries.
3466 Unsigned value, in milliseconds. If not set, the period will
3467 be either the default (28000), or a value based on
3468 CONFIG_NET_RETRY_COUNT, if defined. This value has
3469 precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3471 memmatches - Number of matches found by the last 'ms' command, in hex
3473 memaddr - Address of the last match found by the 'ms' command, in hex,
3476 mempos - Index position of the last match found by the 'ms' command,
3477 in units of the size (.b, .w, .l) of the search
3480 The following image location variables contain the location of images
3481 used in booting. The "Image" column gives the role of the image and is
3482 not an environment variable name. The other columns are environment
3483 variable names. "File Name" gives the name of the file on a TFTP
3484 server, "RAM Address" gives the location in RAM the image will be
3485 loaded to, and "Flash Location" gives the image's address in NOR
3486 flash or offset in NAND flash.
3488 *Note* - these variables don't have to be defined for all boards, some
3489 boards currently use other variables for these purposes, and some
3490 boards use these variables for other purposes.
3492 Image File Name RAM Address Flash Location
3493 ----- --------- ----------- --------------
3494 u-boot u-boot u-boot_addr_r u-boot_addr
3495 Linux kernel bootfile kernel_addr_r kernel_addr
3496 device tree blob fdtfile fdt_addr_r fdt_addr
3497 ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr
3499 The following environment variables may be used and automatically
3500 updated by the network boot commands ("bootp" and "rarpboot"),
3501 depending the information provided by your boot server:
3503 bootfile - see above
3504 dnsip - IP address of your Domain Name Server
3505 dnsip2 - IP address of your secondary Domain Name Server
3506 gatewayip - IP address of the Gateway (Router) to use
3507 hostname - Target hostname
3509 netmask - Subnet Mask
3510 rootpath - Pathname of the root filesystem on the NFS server
3511 serverip - see above
3514 There are two special Environment Variables:
3516 serial# - contains hardware identification information such
3517 as type string and/or serial number
3518 ethaddr - Ethernet address
3520 These variables can be set only once (usually during manufacturing of
3521 the board). U-Boot refuses to delete or overwrite these variables
3522 once they have been set once.
3525 Further special Environment Variables:
3527 ver - Contains the U-Boot version string as printed
3528 with the "version" command. This variable is
3529 readonly (see CONFIG_VERSION_VARIABLE).
3532 Please note that changes to some configuration parameters may take
3533 only effect after the next boot (yes, that's just like Windoze :-).
3536 Callback functions for environment variables:
3537 ---------------------------------------------
3539 For some environment variables, the behavior of u-boot needs to change
3540 when their values are changed. This functionality allows functions to
3541 be associated with arbitrary variables. On creation, overwrite, or
3542 deletion, the callback will provide the opportunity for some side
3543 effect to happen or for the change to be rejected.
3545 The callbacks are named and associated with a function using the
3546 U_BOOT_ENV_CALLBACK macro in your board or driver code.
3548 These callbacks are associated with variables in one of two ways. The
3549 static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3550 in the board configuration to a string that defines a list of
3551 associations. The list must be in the following format:
3553 entry = variable_name[:callback_name]
3556 If the callback name is not specified, then the callback is deleted.
3557 Spaces are also allowed anywhere in the list.
3559 Callbacks can also be associated by defining the ".callbacks" variable
3560 with the same list format above. Any association in ".callbacks" will
3561 override any association in the static list. You can define
3562 CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3563 ".callbacks" environment variable in the default or embedded environment.
3565 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3566 regular expression. This allows multiple variables to be connected to
3567 the same callback without explicitly listing them all out.
3569 The signature of the callback functions is:
3571 int callback(const char *name, const char *value, enum env_op op, int flags)
3573 * name - changed environment variable
3574 * value - new value of the environment variable
3575 * op - operation (create, overwrite, or delete)
3576 * flags - attributes of the environment variable change, see flags H_* in
3579 The return value is 0 if the variable change is accepted and 1 otherwise.
3581 Command Line Parsing:
3582 =====================
3584 There are two different command line parsers available with U-Boot:
3585 the old "simple" one, and the much more powerful "hush" shell:
3587 Old, simple command line parser:
3588 --------------------------------
3590 - supports environment variables (through setenv / saveenv commands)
3591 - several commands on one line, separated by ';'
3592 - variable substitution using "... ${name} ..." syntax
3593 - special characters ('$', ';') can be escaped by prefixing with '\',
3595 setenv bootcmd bootm \${address}
3596 - You can also escape text by enclosing in single apostrophes, for example:
3597 setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3602 - similar to Bourne shell, with control structures like
3603 if...then...else...fi, for...do...done; while...do...done,
3604 until...do...done, ...
3605 - supports environment ("global") variables (through setenv / saveenv
3606 commands) and local shell variables (through standard shell syntax
3607 "name=value"); only environment variables can be used with "run"
3613 (1) If a command line (or an environment variable executed by a "run"
3614 command) contains several commands separated by semicolon, and
3615 one of these commands fails, then the remaining commands will be
3618 (2) If you execute several variables with one call to run (i. e.
3619 calling run with a list of variables as arguments), any failing
3620 command will cause "run" to terminate, i. e. the remaining
3621 variables are not executed.
3623 Note for Redundant Ethernet Interfaces:
3624 =======================================
3626 Some boards come with redundant Ethernet interfaces; U-Boot supports
3627 such configurations and is capable of automatic selection of a
3628 "working" interface when needed. MAC assignment works as follows:
3630 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3631 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3632 "eth1addr" (=>eth1), "eth2addr", ...
3634 If the network interface stores some valid MAC address (for instance
3635 in SROM), this is used as default address if there is NO correspon-
3636 ding setting in the environment; if the corresponding environment
3637 variable is set, this overrides the settings in the card; that means:
3639 o If the SROM has a valid MAC address, and there is no address in the
3640 environment, the SROM's address is used.
3642 o If there is no valid address in the SROM, and a definition in the
3643 environment exists, then the value from the environment variable is
3646 o If both the SROM and the environment contain a MAC address, and
3647 both addresses are the same, this MAC address is used.
3649 o If both the SROM and the environment contain a MAC address, and the
3650 addresses differ, the value from the environment is used and a
3653 o If neither SROM nor the environment contain a MAC address, an error
3654 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3655 a random, locally-assigned MAC is used.
3657 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3658 will be programmed into hardware as part of the initialization process. This
3659 may be skipped by setting the appropriate 'ethmacskip' environment variable.
3660 The naming convention is as follows:
3661 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3666 U-Boot is capable of booting (and performing other auxiliary operations on)
3667 images in two formats:
3669 New uImage format (FIT)
3670 -----------------------
3672 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3673 to Flattened Device Tree). It allows the use of images with multiple
3674 components (several kernels, ramdisks, etc.), with contents protected by
3675 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3681 Old image format is based on binary files which can be basically anything,
3682 preceded by a special header; see the definitions in include/image.h for
3683 details; basically, the header defines the following image properties:
3685 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3686 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3687 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3688 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3690 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3691 IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3692 Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3693 * Compression Type (uncompressed, gzip, bzip2)
3699 The header is marked by a special Magic Number, and both the header
3700 and the data portions of the image are secured against corruption by
3707 Although U-Boot should support any OS or standalone application
3708 easily, the main focus has always been on Linux during the design of
3711 U-Boot includes many features that so far have been part of some
3712 special "boot loader" code within the Linux kernel. Also, any
3713 "initrd" images to be used are no longer part of one big Linux image;
3714 instead, kernel and "initrd" are separate images. This implementation
3715 serves several purposes:
3717 - the same features can be used for other OS or standalone
3718 applications (for instance: using compressed images to reduce the
3719 Flash memory footprint)
3721 - it becomes much easier to port new Linux kernel versions because
3722 lots of low-level, hardware dependent stuff are done by U-Boot
3724 - the same Linux kernel image can now be used with different "initrd"
3725 images; of course this also means that different kernel images can
3726 be run with the same "initrd". This makes testing easier (you don't
3727 have to build a new "zImage.initrd" Linux image when you just
3728 change a file in your "initrd"). Also, a field-upgrade of the
3729 software is easier now.
3735 Porting Linux to U-Boot based systems:
3736 ---------------------------------------
3738 U-Boot cannot save you from doing all the necessary modifications to
3739 configure the Linux device drivers for use with your target hardware
3740 (no, we don't intend to provide a full virtual machine interface to
3743 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3745 Just make sure your machine specific header file (for instance
3746 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3747 Information structure as we define in include/asm-<arch>/u-boot.h,
3748 and make sure that your definition of IMAP_ADDR uses the same value
3749 as your U-Boot configuration in CONFIG_SYS_IMMR.
3751 Note that U-Boot now has a driver model, a unified model for drivers.
3752 If you are adding a new driver, plumb it into driver model. If there
3753 is no uclass available, you are encouraged to create one. See
3757 Configuring the Linux kernel:
3758 -----------------------------
3760 No specific requirements for U-Boot. Make sure you have some root
3761 device (initial ramdisk, NFS) for your target system.
3764 Building a Linux Image:
3765 -----------------------
3767 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3768 not used. If you use recent kernel source, a new build target
3769 "uImage" will exist which automatically builds an image usable by
3770 U-Boot. Most older kernels also have support for a "pImage" target,
3771 which was introduced for our predecessor project PPCBoot and uses a
3772 100% compatible format.
3776 make TQM850L_defconfig
3781 The "uImage" build target uses a special tool (in 'tools/mkimage') to
3782 encapsulate a compressed Linux kernel image with header information,
3783 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3785 * build a standard "vmlinux" kernel image (in ELF binary format):
3787 * convert the kernel into a raw binary image:
3789 ${CROSS_COMPILE}-objcopy -O binary \
3790 -R .note -R .comment \
3791 -S vmlinux linux.bin
3793 * compress the binary image:
3797 * package compressed binary image for U-Boot:
3799 mkimage -A ppc -O linux -T kernel -C gzip \
3800 -a 0 -e 0 -n "Linux Kernel Image" \
3801 -d linux.bin.gz uImage
3804 The "mkimage" tool can also be used to create ramdisk images for use
3805 with U-Boot, either separated from the Linux kernel image, or
3806 combined into one file. "mkimage" encapsulates the images with a 64
3807 byte header containing information about target architecture,
3808 operating system, image type, compression method, entry points, time
3809 stamp, CRC32 checksums, etc.
3811 "mkimage" can be called in two ways: to verify existing images and
3812 print the header information, or to build new images.
3814 In the first form (with "-l" option) mkimage lists the information
3815 contained in the header of an existing U-Boot image; this includes
3816 checksum verification:
3818 tools/mkimage -l image
3819 -l ==> list image header information
3821 The second form (with "-d" option) is used to build a U-Boot image
3822 from a "data file" which is used as image payload:
3824 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3825 -n name -d data_file image
3826 -A ==> set architecture to 'arch'
3827 -O ==> set operating system to 'os'
3828 -T ==> set image type to 'type'
3829 -C ==> set compression type 'comp'
3830 -a ==> set load address to 'addr' (hex)
3831 -e ==> set entry point to 'ep' (hex)
3832 -n ==> set image name to 'name'
3833 -d ==> use image data from 'datafile'
3835 Right now, all Linux kernels for PowerPC systems use the same load
3836 address (0x00000000), but the entry point address depends on the
3839 - 2.2.x kernels have the entry point at 0x0000000C,
3840 - 2.3.x and later kernels have the entry point at 0x00000000.
3842 So a typical call to build a U-Boot image would read:
3844 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3845 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3846 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3847 > examples/uImage.TQM850L
3848 Image Name: 2.4.4 kernel for TQM850L
3849 Created: Wed Jul 19 02:34:59 2000
3850 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3851 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3852 Load Address: 0x00000000
3853 Entry Point: 0x00000000
3855 To verify the contents of the image (or check for corruption):
3857 -> tools/mkimage -l examples/uImage.TQM850L
3858 Image Name: 2.4.4 kernel for TQM850L
3859 Created: Wed Jul 19 02:34:59 2000
3860 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3861 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3862 Load Address: 0x00000000
3863 Entry Point: 0x00000000
3865 NOTE: for embedded systems where boot time is critical you can trade
3866 speed for memory and install an UNCOMPRESSED image instead: this
3867 needs more space in Flash, but boots much faster since it does not
3868 need to be uncompressed:
3870 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3871 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3872 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3873 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3874 > examples/uImage.TQM850L-uncompressed
3875 Image Name: 2.4.4 kernel for TQM850L
3876 Created: Wed Jul 19 02:34:59 2000
3877 Image Type: PowerPC Linux Kernel Image (uncompressed)
3878 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
3879 Load Address: 0x00000000
3880 Entry Point: 0x00000000
3883 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3884 when your kernel is intended to use an initial ramdisk:
3886 -> tools/mkimage -n 'Simple Ramdisk Image' \
3887 > -A ppc -O linux -T ramdisk -C gzip \
3888 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3889 Image Name: Simple Ramdisk Image
3890 Created: Wed Jan 12 14:01:50 2000
3891 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3892 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
3893 Load Address: 0x00000000
3894 Entry Point: 0x00000000
3896 The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
3897 option performs the converse operation of the mkimage's second form (the "-d"
3898 option). Given an image built by mkimage, the dumpimage extracts a "data file"
3901 tools/dumpimage -i image -T type -p position data_file
3902 -i ==> extract from the 'image' a specific 'data_file'
3903 -T ==> set image type to 'type'
3904 -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
3907 Installing a Linux Image:
3908 -------------------------
3910 To downloading a U-Boot image over the serial (console) interface,
3911 you must convert the image to S-Record format:
3913 objcopy -I binary -O srec examples/image examples/image.srec
3915 The 'objcopy' does not understand the information in the U-Boot
3916 image header, so the resulting S-Record file will be relative to
3917 address 0x00000000. To load it to a given address, you need to
3918 specify the target address as 'offset' parameter with the 'loads'
3921 Example: install the image to address 0x40100000 (which on the
3922 TQM8xxL is in the first Flash bank):
3924 => erase 40100000 401FFFFF
3930 ## Ready for S-Record download ...
3931 ~>examples/image.srec
3932 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3934 15989 15990 15991 15992
3935 [file transfer complete]
3937 ## Start Addr = 0x00000000
3940 You can check the success of the download using the 'iminfo' command;
3941 this includes a checksum verification so you can be sure no data
3942 corruption happened:
3946 ## Checking Image at 40100000 ...
3947 Image Name: 2.2.13 for initrd on TQM850L
3948 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3949 Data Size: 335725 Bytes = 327 kB = 0 MB
3950 Load Address: 00000000
3951 Entry Point: 0000000c
3952 Verifying Checksum ... OK
3958 The "bootm" command is used to boot an application that is stored in
3959 memory (RAM or Flash). In case of a Linux kernel image, the contents
3960 of the "bootargs" environment variable is passed to the kernel as
3961 parameters. You can check and modify this variable using the
3962 "printenv" and "setenv" commands:
3965 => printenv bootargs
3966 bootargs=root=/dev/ram
3968 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3970 => printenv bootargs
3971 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3974 ## Booting Linux kernel at 40020000 ...
3975 Image Name: 2.2.13 for NFS on TQM850L
3976 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3977 Data Size: 381681 Bytes = 372 kB = 0 MB
3978 Load Address: 00000000
3979 Entry Point: 0000000c
3980 Verifying Checksum ... OK
3981 Uncompressing Kernel Image ... OK
3982 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
3983 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3984 time_init: decrementer frequency = 187500000/60
3985 Calibrating delay loop... 49.77 BogoMIPS
3986 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3989 If you want to boot a Linux kernel with initial RAM disk, you pass
3990 the memory addresses of both the kernel and the initrd image (PPBCOOT
3991 format!) to the "bootm" command:
3993 => imi 40100000 40200000
3995 ## Checking Image at 40100000 ...
3996 Image Name: 2.2.13 for initrd on TQM850L
3997 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3998 Data Size: 335725 Bytes = 327 kB = 0 MB
3999 Load Address: 00000000
4000 Entry Point: 0000000c
4001 Verifying Checksum ... OK
4003 ## Checking Image at 40200000 ...
4004 Image Name: Simple Ramdisk Image
4005 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
4006 Data Size: 566530 Bytes = 553 kB = 0 MB
4007 Load Address: 00000000
4008 Entry Point: 00000000
4009 Verifying Checksum ... OK
4011 => bootm 40100000 40200000
4012 ## Booting Linux kernel at 40100000 ...
4013 Image Name: 2.2.13 for initrd on TQM850L
4014 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4015 Data Size: 335725 Bytes = 327 kB = 0 MB
4016 Load Address: 00000000
4017 Entry Point: 0000000c
4018 Verifying Checksum ... OK
4019 Uncompressing Kernel Image ... OK
4020 ## Loading RAMDisk Image at 40200000 ...
4021 Image Name: Simple Ramdisk Image
4022 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
4023 Data Size: 566530 Bytes = 553 kB = 0 MB
4024 Load Address: 00000000
4025 Entry Point: 00000000
4026 Verifying Checksum ... OK
4027 Loading Ramdisk ... OK
4028 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
4029 Boot arguments: root=/dev/ram
4030 time_init: decrementer frequency = 187500000/60
4031 Calibrating delay loop... 49.77 BogoMIPS
4033 RAMDISK: Compressed image found at block 0
4034 VFS: Mounted root (ext2 filesystem).
4038 Boot Linux and pass a flat device tree:
4041 First, U-Boot must be compiled with the appropriate defines. See the section
4042 titled "Linux Kernel Interface" above for a more in depth explanation. The
4043 following is an example of how to start a kernel and pass an updated
4049 oft=oftrees/mpc8540ads.dtb
4050 => tftp $oftaddr $oft
4051 Speed: 1000, full duplex
4053 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4054 Filename 'oftrees/mpc8540ads.dtb'.
4055 Load address: 0x300000
4058 Bytes transferred = 4106 (100a hex)
4059 => tftp $loadaddr $bootfile
4060 Speed: 1000, full duplex
4062 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4064 Load address: 0x200000
4065 Loading:############
4067 Bytes transferred = 1029407 (fb51f hex)
4072 => bootm $loadaddr - $oftaddr
4073 ## Booting image at 00200000 ...
4074 Image Name: Linux-2.6.17-dirty
4075 Image Type: PowerPC Linux Kernel Image (gzip compressed)
4076 Data Size: 1029343 Bytes = 1005.2 kB
4077 Load Address: 00000000
4078 Entry Point: 00000000
4079 Verifying Checksum ... OK
4080 Uncompressing Kernel Image ... OK
4081 Booting using flat device tree at 0x300000
4082 Using MPC85xx ADS machine description
4083 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4087 More About U-Boot Image Types:
4088 ------------------------------
4090 U-Boot supports the following image types:
4092 "Standalone Programs" are directly runnable in the environment
4093 provided by U-Boot; it is expected that (if they behave
4094 well) you can continue to work in U-Boot after return from
4095 the Standalone Program.
4096 "OS Kernel Images" are usually images of some Embedded OS which
4097 will take over control completely. Usually these programs
4098 will install their own set of exception handlers, device
4099 drivers, set up the MMU, etc. - this means, that you cannot
4100 expect to re-enter U-Boot except by resetting the CPU.
4101 "RAMDisk Images" are more or less just data blocks, and their
4102 parameters (address, size) are passed to an OS kernel that is
4104 "Multi-File Images" contain several images, typically an OS
4105 (Linux) kernel image and one or more data images like
4106 RAMDisks. This construct is useful for instance when you want
4107 to boot over the network using BOOTP etc., where the boot
4108 server provides just a single image file, but you want to get
4109 for instance an OS kernel and a RAMDisk image.
4111 "Multi-File Images" start with a list of image sizes, each
4112 image size (in bytes) specified by an "uint32_t" in network
4113 byte order. This list is terminated by an "(uint32_t)0".
4114 Immediately after the terminating 0 follow the images, one by
4115 one, all aligned on "uint32_t" boundaries (size rounded up to
4116 a multiple of 4 bytes).
4118 "Firmware Images" are binary images containing firmware (like
4119 U-Boot or FPGA images) which usually will be programmed to
4122 "Script files" are command sequences that will be executed by
4123 U-Boot's command interpreter; this feature is especially
4124 useful when you configure U-Boot to use a real shell (hush)
4125 as command interpreter.
4127 Booting the Linux zImage:
4128 -------------------------
4130 On some platforms, it's possible to boot Linux zImage. This is done
4131 using the "bootz" command. The syntax of "bootz" command is the same
4132 as the syntax of "bootm" command.
4134 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4135 kernel with raw initrd images. The syntax is slightly different, the
4136 address of the initrd must be augmented by it's size, in the following
4137 format: "<initrd addres>:<initrd size>".
4143 One of the features of U-Boot is that you can dynamically load and
4144 run "standalone" applications, which can use some resources of
4145 U-Boot like console I/O functions or interrupt services.
4147 Two simple examples are included with the sources:
4152 'examples/hello_world.c' contains a small "Hello World" Demo
4153 application; it is automatically compiled when you build U-Boot.
4154 It's configured to run at address 0x00040004, so you can play with it
4158 ## Ready for S-Record download ...
4159 ~>examples/hello_world.srec
4160 1 2 3 4 5 6 7 8 9 10 11 ...
4161 [file transfer complete]
4163 ## Start Addr = 0x00040004
4165 => go 40004 Hello World! This is a test.
4166 ## Starting application at 0x00040004 ...
4177 Hit any key to exit ...
4179 ## Application terminated, rc = 0x0
4181 Another example, which demonstrates how to register a CPM interrupt
4182 handler with the U-Boot code, can be found in 'examples/timer.c'.
4183 Here, a CPM timer is set up to generate an interrupt every second.
4184 The interrupt service routine is trivial, just printing a '.'
4185 character, but this is just a demo program. The application can be
4186 controlled by the following keys:
4188 ? - print current values og the CPM Timer registers
4189 b - enable interrupts and start timer
4190 e - stop timer and disable interrupts
4191 q - quit application
4194 ## Ready for S-Record download ...
4195 ~>examples/timer.srec
4196 1 2 3 4 5 6 7 8 9 10 11 ...
4197 [file transfer complete]
4199 ## Start Addr = 0x00040004
4202 ## Starting application at 0x00040004 ...
4205 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4208 [q, b, e, ?] Set interval 1000000 us
4211 [q, b, e, ?] ........
4212 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4215 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4218 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4221 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4223 [q, b, e, ?] ...Stopping timer
4225 [q, b, e, ?] ## Application terminated, rc = 0x0
4231 Over time, many people have reported problems when trying to use the
4232 "minicom" terminal emulation program for serial download. I (wd)
4233 consider minicom to be broken, and recommend not to use it. Under
4234 Unix, I recommend to use C-Kermit for general purpose use (and
4235 especially for kermit binary protocol download ("loadb" command), and
4236 use "cu" for S-Record download ("loads" command). See
4237 http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4238 for help with kermit.
4241 Nevertheless, if you absolutely want to use it try adding this
4242 configuration to your "File transfer protocols" section:
4244 Name Program Name U/D FullScr IO-Red. Multi
4245 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
4246 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
4252 Starting at version 0.9.2, U-Boot supports NetBSD both as host
4253 (build U-Boot) and target system (boots NetBSD/mpc8xx).
4255 Building requires a cross environment; it is known to work on
4256 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4257 need gmake since the Makefiles are not compatible with BSD make).
4258 Note that the cross-powerpc package does not install include files;
4259 attempting to build U-Boot will fail because <machine/ansi.h> is
4260 missing. This file has to be installed and patched manually:
4262 # cd /usr/pkg/cross/powerpc-netbsd/include
4264 # ln -s powerpc machine
4265 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4266 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
4268 Native builds *don't* work due to incompatibilities between native
4269 and U-Boot include files.
4271 Booting assumes that (the first part of) the image booted is a
4272 stage-2 loader which in turn loads and then invokes the kernel
4273 proper. Loader sources will eventually appear in the NetBSD source
4274 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4275 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4278 Implementation Internals:
4279 =========================
4281 The following is not intended to be a complete description of every
4282 implementation detail. However, it should help to understand the
4283 inner workings of U-Boot and make it easier to port it to custom
4287 Initial Stack, Global Data:
4288 ---------------------------
4290 The implementation of U-Boot is complicated by the fact that U-Boot
4291 starts running out of ROM (flash memory), usually without access to
4292 system RAM (because the memory controller is not initialized yet).
4293 This means that we don't have writable Data or BSS segments, and BSS
4294 is not initialized as zero. To be able to get a C environment working
4295 at all, we have to allocate at least a minimal stack. Implementation
4296 options for this are defined and restricted by the CPU used: Some CPU
4297 models provide on-chip memory (like the IMMR area on MPC8xx and
4298 MPC826x processors), on others (parts of) the data cache can be
4299 locked as (mis-) used as memory, etc.
4301 Chris Hallinan posted a good summary of these issues to the
4302 U-Boot mailing list:
4304 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4305 From: "Chris Hallinan" <clh@net1plus.com>
4306 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4309 Correct me if I'm wrong, folks, but the way I understand it
4310 is this: Using DCACHE as initial RAM for Stack, etc, does not
4311 require any physical RAM backing up the cache. The cleverness
4312 is that the cache is being used as a temporary supply of
4313 necessary storage before the SDRAM controller is setup. It's
4314 beyond the scope of this list to explain the details, but you
4315 can see how this works by studying the cache architecture and
4316 operation in the architecture and processor-specific manuals.
4318 OCM is On Chip Memory, which I believe the 405GP has 4K. It
4319 is another option for the system designer to use as an
4320 initial stack/RAM area prior to SDRAM being available. Either
4321 option should work for you. Using CS 4 should be fine if your
4322 board designers haven't used it for something that would
4323 cause you grief during the initial boot! It is frequently not
4326 CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4327 with your processor/board/system design. The default value
4328 you will find in any recent u-boot distribution in
4329 walnut.h should work for you. I'd set it to a value larger
4330 than your SDRAM module. If you have a 64MB SDRAM module, set
4331 it above 400_0000. Just make sure your board has no resources
4332 that are supposed to respond to that address! That code in
4333 start.S has been around a while and should work as is when
4334 you get the config right.
4339 It is essential to remember this, since it has some impact on the C
4340 code for the initialization procedures:
4342 * Initialized global data (data segment) is read-only. Do not attempt
4345 * Do not use any uninitialized global data (or implicitly initialized
4346 as zero data - BSS segment) at all - this is undefined, initiali-
4347 zation is performed later (when relocating to RAM).
4349 * Stack space is very limited. Avoid big data buffers or things like
4352 Having only the stack as writable memory limits means we cannot use
4353 normal global data to share information between the code. But it
4354 turned out that the implementation of U-Boot can be greatly
4355 simplified by making a global data structure (gd_t) available to all
4356 functions. We could pass a pointer to this data as argument to _all_
4357 functions, but this would bloat the code. Instead we use a feature of
4358 the GCC compiler (Global Register Variables) to share the data: we
4359 place a pointer (gd) to the global data into a register which we
4360 reserve for this purpose.
4362 When choosing a register for such a purpose we are restricted by the
4363 relevant (E)ABI specifications for the current architecture, and by
4364 GCC's implementation.
4366 For PowerPC, the following registers have specific use:
4368 R2: reserved for system use
4369 R3-R4: parameter passing and return values
4370 R5-R10: parameter passing
4371 R13: small data area pointer
4375 (U-Boot also uses R12 as internal GOT pointer. r12
4376 is a volatile register so r12 needs to be reset when
4377 going back and forth between asm and C)
4379 ==> U-Boot will use R2 to hold a pointer to the global data
4381 Note: on PPC, we could use a static initializer (since the
4382 address of the global data structure is known at compile time),
4383 but it turned out that reserving a register results in somewhat
4384 smaller code - although the code savings are not that big (on
4385 average for all boards 752 bytes for the whole U-Boot image,
4386 624 text + 127 data).
4388 On ARM, the following registers are used:
4390 R0: function argument word/integer result
4391 R1-R3: function argument word
4392 R9: platform specific
4393 R10: stack limit (used only if stack checking is enabled)
4394 R11: argument (frame) pointer
4395 R12: temporary workspace
4398 R15: program counter
4400 ==> U-Boot will use R9 to hold a pointer to the global data
4402 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4404 On Nios II, the ABI is documented here:
4405 http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4407 ==> U-Boot will use gp to hold a pointer to the global data
4409 Note: on Nios II, we give "-G0" option to gcc and don't use gp
4410 to access small data sections, so gp is free.
4412 On NDS32, the following registers are used:
4414 R0-R1: argument/return
4416 R15: temporary register for assembler
4417 R16: trampoline register
4418 R28: frame pointer (FP)
4419 R29: global pointer (GP)
4420 R30: link register (LP)
4421 R31: stack pointer (SP)
4422 PC: program counter (PC)
4424 ==> U-Boot will use R10 to hold a pointer to the global data
4426 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4427 or current versions of GCC may "optimize" the code too much.
4429 On RISC-V, the following registers are used:
4431 x0: hard-wired zero (zero)
4432 x1: return address (ra)
4433 x2: stack pointer (sp)
4434 x3: global pointer (gp)
4435 x4: thread pointer (tp)
4436 x5: link register (t0)
4437 x8: frame pointer (fp)
4438 x10-x11: arguments/return values (a0-1)
4439 x12-x17: arguments (a2-7)
4440 x28-31: temporaries (t3-6)
4441 pc: program counter (pc)
4443 ==> U-Boot will use gp to hold a pointer to the global data
4448 U-Boot runs in system state and uses physical addresses, i.e. the
4449 MMU is not used either for address mapping nor for memory protection.
4451 The available memory is mapped to fixed addresses using the memory
4452 controller. In this process, a contiguous block is formed for each
4453 memory type (Flash, SDRAM, SRAM), even when it consists of several
4454 physical memory banks.
4456 U-Boot is installed in the first 128 kB of the first Flash bank (on
4457 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4458 booting and sizing and initializing DRAM, the code relocates itself
4459 to the upper end of DRAM. Immediately below the U-Boot code some
4460 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4461 configuration setting]. Below that, a structure with global Board
4462 Info data is placed, followed by the stack (growing downward).
4464 Additionally, some exception handler code is copied to the low 8 kB
4465 of DRAM (0x00000000 ... 0x00001FFF).
4467 So a typical memory configuration with 16 MB of DRAM could look like
4470 0x0000 0000 Exception Vector code
4473 0x0000 2000 Free for Application Use
4479 0x00FB FF20 Monitor Stack (Growing downward)
4480 0x00FB FFAC Board Info Data and permanent copy of global data
4481 0x00FC 0000 Malloc Arena
4484 0x00FE 0000 RAM Copy of Monitor Code
4485 ... eventually: LCD or video framebuffer
4486 ... eventually: pRAM (Protected RAM - unchanged by reset)
4487 0x00FF FFFF [End of RAM]
4490 System Initialization:
4491 ----------------------
4493 In the reset configuration, U-Boot starts at the reset entry point
4494 (on most PowerPC systems at address 0x00000100). Because of the reset
4495 configuration for CS0# this is a mirror of the on board Flash memory.
4496 To be able to re-map memory U-Boot then jumps to its link address.
4497 To be able to implement the initialization code in C, a (small!)
4498 initial stack is set up in the internal Dual Ported RAM (in case CPUs
4499 which provide such a feature like), or in a locked part of the data
4500 cache. After that, U-Boot initializes the CPU core, the caches and
4503 Next, all (potentially) available memory banks are mapped using a
4504 preliminary mapping. For example, we put them on 512 MB boundaries
4505 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4506 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4507 programmed for SDRAM access. Using the temporary configuration, a
4508 simple memory test is run that determines the size of the SDRAM
4511 When there is more than one SDRAM bank, and the banks are of
4512 different size, the largest is mapped first. For equal size, the first
4513 bank (CS2#) is mapped first. The first mapping is always for address
4514 0x00000000, with any additional banks following immediately to create
4515 contiguous memory starting from 0.
4517 Then, the monitor installs itself at the upper end of the SDRAM area
4518 and allocates memory for use by malloc() and for the global Board
4519 Info data; also, the exception vector code is copied to the low RAM
4520 pages, and the final stack is set up.
4522 Only after this relocation will you have a "normal" C environment;
4523 until that you are restricted in several ways, mostly because you are
4524 running from ROM, and because the code will have to be relocated to a
4528 U-Boot Porting Guide:
4529 ----------------------
4531 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4535 int main(int argc, char *argv[])
4537 sighandler_t no_more_time;
4539 signal(SIGALRM, no_more_time);
4540 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4542 if (available_money > available_manpower) {
4543 Pay consultant to port U-Boot;
4547 Download latest U-Boot source;
4549 Subscribe to u-boot mailing list;
4552 email("Hi, I am new to U-Boot, how do I get started?");
4555 Read the README file in the top level directory;
4556 Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4557 Read applicable doc/README.*;
4558 Read the source, Luke;
4559 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4562 if (available_money > toLocalCurrency ($2500))
4565 Add a lot of aggravation and time;
4567 if (a similar board exists) { /* hopefully... */
4568 cp -a board/<similar> board/<myboard>
4569 cp include/configs/<similar>.h include/configs/<myboard>.h
4571 Create your own board support subdirectory;
4572 Create your own board include/configs/<myboard>.h file;
4574 Edit new board/<myboard> files
4575 Edit new include/configs/<myboard>.h
4580 Add / modify source code;
4584 email("Hi, I am having problems...");
4586 Send patch file to the U-Boot email list;
4587 if (reasonable critiques)
4588 Incorporate improvements from email list code review;
4590 Defend code as written;
4596 void no_more_time (int sig)
4605 All contributions to U-Boot should conform to the Linux kernel
4606 coding style; see the kernel coding style guide at
4607 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4608 script "scripts/Lindent" in your Linux kernel source directory.
4610 Source files originating from a different project (for example the
4611 MTD subsystem) are generally exempt from these guidelines and are not
4612 reformatted to ease subsequent migration to newer versions of those
4615 Please note that U-Boot is implemented in C (and to some small parts in
4616 Assembler); no C++ is used, so please do not use C++ style comments (//)
4619 Please also stick to the following formatting rules:
4620 - remove any trailing white space
4621 - use TAB characters for indentation and vertical alignment, not spaces
4622 - make sure NOT to use DOS '\r\n' line feeds
4623 - do not add more than 2 consecutive empty lines to source files
4624 - do not add trailing empty lines to source files
4626 Submissions which do not conform to the standards may be returned
4627 with a request to reformat the changes.
4633 Since the number of patches for U-Boot is growing, we need to
4634 establish some rules. Submissions which do not conform to these rules
4635 may be rejected, even when they contain important and valuable stuff.
4637 Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4639 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4640 see https://lists.denx.de/listinfo/u-boot
4642 When you send a patch, please include the following information with
4645 * For bug fixes: a description of the bug and how your patch fixes
4646 this bug. Please try to include a way of demonstrating that the
4647 patch actually fixes something.
4649 * For new features: a description of the feature and your
4652 * For major contributions, add a MAINTAINERS file with your
4653 information and associated file and directory references.
4655 * When you add support for a new board, don't forget to add a
4656 maintainer e-mail address to the boards.cfg file, too.
4658 * If your patch adds new configuration options, don't forget to
4659 document these in the README file.
4661 * The patch itself. If you are using git (which is *strongly*
4662 recommended) you can easily generate the patch using the
4663 "git format-patch". If you then use "git send-email" to send it to
4664 the U-Boot mailing list, you will avoid most of the common problems
4665 with some other mail clients.
4667 If you cannot use git, use "diff -purN OLD NEW". If your version of
4668 diff does not support these options, then get the latest version of
4671 The current directory when running this command shall be the parent
4672 directory of the U-Boot source tree (i. e. please make sure that
4673 your patch includes sufficient directory information for the
4676 We prefer patches as plain text. MIME attachments are discouraged,
4677 and compressed attachments must not be used.
4679 * If one logical set of modifications affects or creates several
4680 files, all these changes shall be submitted in a SINGLE patch file.
4682 * Changesets that contain different, unrelated modifications shall be
4683 submitted as SEPARATE patches, one patch per changeset.
4688 * Before sending the patch, run the buildman script on your patched
4689 source tree and make sure that no errors or warnings are reported
4690 for any of the boards.
4692 * Keep your modifications to the necessary minimum: A patch
4693 containing several unrelated changes or arbitrary reformats will be
4694 returned with a request to re-formatting / split it.
4696 * If you modify existing code, make sure that your new code does not
4697 add to the memory footprint of the code ;-) Small is beautiful!
4698 When adding new features, these should compile conditionally only
4699 (using #ifdef), and the resulting code with the new feature
4700 disabled must not need more memory than the old code without your
4703 * Remember that there is a size limit of 100 kB per message on the
4704 u-boot mailing list. Bigger patches will be moderated. If they are
4705 reasonable and not too big, they will be acknowledged. But patches
4706 bigger than the size limit should be avoided.