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 https://lists.denx.de/pipermail/u-boot and
55 https://marc.info/?l=u-boot
57 Where to get source code:
58 =========================
60 The U-Boot source code is maintained in the Git repository at
61 https://source.denx.de/u-boot/u-boot.git ; you can browse it online at
62 https://source.denx.de/u-boot/u-boot
64 The "Tags" links on this page allow you to download tarballs of
65 any version you might be interested in. Official releases are also
66 available from the DENX file server through HTTPS or FTP.
67 https://ftp.denx.de/pub/u-boot/
68 ftp://ftp.denx.de/pub/u-boot/
74 - start from 8xxrom sources
75 - create PPCBoot project (https://sourceforge.net/projects/ppcboot)
77 - make it easier to add custom boards
78 - make it possible to add other [PowerPC] CPUs
79 - extend functions, especially:
80 * Provide extended interface to Linux boot loader
83 * ATA disk / SCSI ... boot
84 - create ARMBoot project (https://sourceforge.net/projects/armboot)
85 - add other CPU families (starting with ARM)
86 - create U-Boot project (https://sourceforge.net/projects/u-boot)
87 - current project page: see https://www.denx.de/wiki/U-Boot
93 The "official" name of this project is "Das U-Boot". The spelling
94 "U-Boot" shall be used in all written text (documentation, comments
95 in source files etc.). Example:
97 This is the README file for the U-Boot project.
99 File names etc. shall be based on the string "u-boot". Examples:
101 include/asm-ppc/u-boot.h
103 #include <asm/u-boot.h>
105 Variable names, preprocessor constants etc. shall be either based on
106 the string "u_boot" or on "U_BOOT". Example:
108 U_BOOT_VERSION u_boot_logo
109 IH_OS_U_BOOT u_boot_hush_start
115 Starting with the release in October 2008, the names of the releases
116 were changed from numerical release numbers without deeper meaning
117 into a time stamp based numbering. Regular releases are identified by
118 names consisting of the calendar year and month of the release date.
119 Additional fields (if present) indicate release candidates or bug fix
120 releases in "stable" maintenance trees.
123 U-Boot v2009.11 - Release November 2009
124 U-Boot v2009.11.1 - Release 1 in version November 2009 stable tree
125 U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
131 /arch Architecture-specific files
132 /arc Files generic to ARC architecture
133 /arm Files generic to ARM architecture
134 /m68k Files generic to m68k architecture
135 /microblaze Files generic to microblaze architecture
136 /mips Files generic to MIPS architecture
137 /nds32 Files generic to NDS32 architecture
138 /nios2 Files generic to Altera NIOS2 architecture
139 /powerpc Files generic to PowerPC architecture
140 /riscv Files generic to RISC-V architecture
141 /sandbox Files generic to HW-independent "sandbox"
142 /sh Files generic to SH architecture
143 /x86 Files generic to x86 architecture
144 /xtensa Files generic to Xtensa architecture
145 /api Machine/arch-independent API for external apps
146 /board Board-dependent files
147 /cmd U-Boot commands functions
148 /common Misc architecture-independent functions
149 /configs Board default configuration files
150 /disk Code for disk drive partition handling
151 /doc Documentation (a mix of ReST and READMEs)
152 /drivers Device drivers
153 /dts Makefile for building internal U-Boot fdt.
154 /env Environment support
155 /examples Example code for standalone applications, etc.
156 /fs Filesystem code (cramfs, ext2, jffs2, etc.)
157 /include Header Files
158 /lib Library routines generic to all architectures
159 /Licenses Various license files
161 /post Power On Self Test
162 /scripts Various build scripts and Makefiles
163 /test Various unit test files
164 /tools Tools to build and sign FIT images, etc.
166 Software Configuration:
167 =======================
169 Configuration is usually done using C preprocessor defines; the
170 rationale behind that is to avoid dead code whenever possible.
172 There are two classes of configuration variables:
174 * Configuration _OPTIONS_:
175 These are selectable by the user and have names beginning with
178 * Configuration _SETTINGS_:
179 These depend on the hardware etc. and should not be meddled with if
180 you don't know what you're doing; they have names beginning with
183 Previously, all configuration was done by hand, which involved creating
184 symbolic links and editing configuration files manually. More recently,
185 U-Boot has added the Kbuild infrastructure used by the Linux kernel,
186 allowing you to use the "make menuconfig" command to configure your
190 Selection of Processor Architecture and Board Type:
191 ---------------------------------------------------
193 For all supported boards there are ready-to-use default
194 configurations available; just type "make <board_name>_defconfig".
196 Example: For a TQM823L module type:
199 make TQM823L_defconfig
201 Note: If you're looking for the default configuration file for a board
202 you're sure used to be there but is now missing, check the file
203 doc/README.scrapyard for a list of no longer supported boards.
208 U-Boot can be built natively to run on a Linux host using the 'sandbox'
209 board. This allows feature development which is not board- or architecture-
210 specific to be undertaken on a native platform. The sandbox is also used to
211 run some of U-Boot's tests.
213 See doc/arch/sandbox.rst for more details.
216 Board Initialisation Flow:
217 --------------------------
219 This is the intended start-up flow for boards. This should apply for both
220 SPL and U-Boot proper (i.e. they both follow the same rules).
222 Note: "SPL" stands for "Secondary Program Loader," which is explained in
223 more detail later in this file.
225 At present, SPL mostly uses a separate code path, but the function names
226 and roles of each function are the same. Some boards or architectures
227 may not conform to this. At least most ARM boards which use
228 CONFIG_SPL_FRAMEWORK conform to this.
230 Execution typically starts with an architecture-specific (and possibly
231 CPU-specific) start.S file, such as:
233 - arch/arm/cpu/armv7/start.S
234 - arch/powerpc/cpu/mpc83xx/start.S
235 - arch/mips/cpu/start.S
237 and so on. From there, three functions are called; the purpose and
238 limitations of each of these functions are described below.
241 - purpose: essential init to permit execution to reach board_init_f()
242 - no global_data or BSS
243 - there is no stack (ARMv7 may have one but it will soon be removed)
244 - must not set up SDRAM or use console
245 - must only do the bare minimum to allow execution to continue to
247 - this is almost never needed
248 - return normally from this function
251 - purpose: set up the machine ready for running board_init_r():
252 i.e. SDRAM and serial UART
253 - global_data is available
255 - BSS is not available, so you cannot use global/static variables,
256 only stack variables and global_data
258 Non-SPL-specific notes:
259 - dram_init() is called to set up DRAM. If already done in SPL this
263 - you can override the entire board_init_f() function with your own
265 - preloader_console_init() can be called here in extremis
266 - should set up SDRAM, and anything needed to make the UART work
267 - there is no need to clear BSS, it will be done by crt0.S
268 - for specific scenarios on certain architectures an early BSS *can*
269 be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
270 of BSS prior to entering board_init_f()) but doing so is discouraged.
271 Instead it is strongly recommended to architect any code changes
272 or additions such to not depend on the availability of BSS during
273 board_init_f() as indicated in other sections of this README to
274 maintain compatibility and consistency across the entire code base.
275 - must return normally from this function (don't call board_init_r()
278 Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
279 this point the stack and global_data are relocated to below
280 CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
284 - purpose: main execution, common code
285 - global_data is available
287 - BSS is available, all static/global variables can be used
288 - execution eventually continues to main_loop()
290 Non-SPL-specific notes:
291 - U-Boot is relocated to the top of memory and is now running from
295 - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
296 CONFIG_SPL_STACK_R_ADDR points into SDRAM
297 - preloader_console_init() can be called here - typically this is
298 done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
299 spl_board_init() function containing this call
300 - loads U-Boot or (in falcon mode) Linux
304 Configuration Options:
305 ----------------------
307 Configuration depends on the combination of board and CPU type; all
308 such information is kept in a configuration file
309 "include/configs/<board_name>.h".
311 Example: For a TQM823L module, all configuration settings are in
312 "include/configs/TQM823L.h".
315 Many of the options are named exactly as the corresponding Linux
316 kernel configuration options. The intention is to make it easier to
317 build a config tool - later.
319 - ARM Platform Bus Type(CCI):
320 CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
321 provides full cache coherency between two clusters of multi-core
322 CPUs and I/O coherency for devices and I/O masters
324 CONFIG_SYS_FSL_HAS_CCI400
326 Defined For SoC that has cache coherent interconnect
329 CONFIG_SYS_FSL_HAS_CCN504
331 Defined for SoC that has cache coherent interconnect CCN-504
333 The following options need to be configured:
335 - CPU Type: Define exactly one, e.g. CONFIG_MPC85XX.
337 - Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS.
342 Specifies that the core is a 64-bit PowerPC implementation (implements
343 the "64" category of the Power ISA). This is necessary for ePAPR
344 compliance, among other possible reasons.
346 CONFIG_SYS_FSL_TBCLK_DIV
348 Defines the core time base clock divider ratio compared to the
349 system clock. On most PQ3 devices this is 8, on newer QorIQ
350 devices it can be 16 or 32. The ratio varies from SoC to Soc.
352 CONFIG_SYS_FSL_PCIE_COMPAT
354 Defines the string to utilize when trying to match PCIe device
355 tree nodes for the given platform.
357 CONFIG_SYS_FSL_ERRATUM_A004510
359 Enables a workaround for erratum A004510. If set,
360 then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
361 CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
363 CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
364 CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
366 Defines one or two SoC revisions (low 8 bits of SVR)
367 for which the A004510 workaround should be applied.
369 The rest of SVR is either not relevant to the decision
370 of whether the erratum is present (e.g. p2040 versus
371 p2041) or is implied by the build target, which controls
372 whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
374 See Freescale App Note 4493 for more information about
377 CONFIG_A003399_NOR_WORKAROUND
378 Enables a workaround for IFC erratum A003399. It is only
379 required during NOR boot.
381 CONFIG_A008044_WORKAROUND
382 Enables a workaround for T1040/T1042 erratum A008044. It is only
383 required during NAND boot and valid for Rev 1.0 SoC revision
385 CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
387 This is the value to write into CCSR offset 0x18600
388 according to the A004510 workaround.
390 CONFIG_SYS_FSL_DSP_DDR_ADDR
391 This value denotes start offset of DDR memory which is
392 connected exclusively to the DSP cores.
394 CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
395 This value denotes start offset of M2 memory
396 which is directly connected to the DSP core.
398 CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
399 This value denotes start offset of M3 memory which is directly
400 connected to the DSP core.
402 CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
403 This value denotes start offset of DSP CCSR space.
405 CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
406 Single Source Clock is clocking mode present in some of FSL SoC's.
407 In this mode, a single differential clock is used to supply
408 clocks to the sysclock, ddrclock and usbclock.
410 CONFIG_SYS_CPC_REINIT_F
411 This CONFIG is defined when the CPC is configured as SRAM at the
412 time of U-Boot entry and is required to be re-initialized.
415 Indicates this SoC supports deep sleep feature. If deep sleep is
416 supported, core will start to execute uboot when wakes up.
418 - Generic CPU options:
419 CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
421 Defines the endianess of the CPU. Implementation of those
422 values is arch specific.
425 Freescale DDR driver in use. This type of DDR controller is
426 found in mpc83xx, mpc85xx as well as some ARM core SoCs.
428 CONFIG_SYS_FSL_DDR_ADDR
429 Freescale DDR memory-mapped register base.
431 CONFIG_SYS_FSL_DDR_EMU
432 Specify emulator support for DDR. Some DDR features such as
433 deskew training are not available.
435 CONFIG_SYS_FSL_DDRC_GEN1
436 Freescale DDR1 controller.
438 CONFIG_SYS_FSL_DDRC_GEN2
439 Freescale DDR2 controller.
441 CONFIG_SYS_FSL_DDRC_GEN3
442 Freescale DDR3 controller.
444 CONFIG_SYS_FSL_DDRC_GEN4
445 Freescale DDR4 controller.
447 CONFIG_SYS_FSL_DDRC_ARM_GEN3
448 Freescale DDR3 controller for ARM-based SoCs.
451 Board config to use DDR1. It can be enabled for SoCs with
452 Freescale DDR1 or DDR2 controllers, depending on the board
456 Board config to use DDR2. It can be enabled for SoCs with
457 Freescale DDR2 or DDR3 controllers, depending on the board
461 Board config to use DDR3. It can be enabled for SoCs with
462 Freescale DDR3 or DDR3L controllers.
465 Board config to use DDR3L. It can be enabled for SoCs with
469 Board config to use DDR4. It can be enabled for SoCs with
472 CONFIG_SYS_FSL_IFC_BE
473 Defines the IFC controller register space as Big Endian
475 CONFIG_SYS_FSL_IFC_LE
476 Defines the IFC controller register space as Little Endian
478 CONFIG_SYS_FSL_IFC_CLK_DIV
479 Defines divider of platform clock(clock input to IFC controller).
481 CONFIG_SYS_FSL_LBC_CLK_DIV
482 Defines divider of platform clock(clock input to eLBC controller).
484 CONFIG_SYS_FSL_PBL_PBI
485 It enables addition of RCW (Power on reset configuration) in built image.
486 Please refer doc/README.pblimage for more details
488 CONFIG_SYS_FSL_PBL_RCW
489 It adds PBI(pre-boot instructions) commands in u-boot build image.
490 PBI commands can be used to configure SoC before it starts the execution.
491 Please refer doc/README.pblimage for more details
493 CONFIG_SYS_FSL_DDR_BE
494 Defines the DDR controller register space as Big Endian
496 CONFIG_SYS_FSL_DDR_LE
497 Defines the DDR controller register space as Little Endian
499 CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
500 Physical address from the view of DDR controllers. It is the
501 same as CONFIG_SYS_DDR_SDRAM_BASE for all Power SoCs. But
502 it could be different for ARM SoCs.
504 CONFIG_SYS_FSL_DDR_INTLV_256B
505 DDR controller interleaving on 256-byte. This is a special
506 interleaving mode, handled by Dickens for Freescale layerscape
509 CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
510 Number of controllers used as main memory.
512 CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
513 Number of controllers used for other than main memory.
515 CONFIG_SYS_FSL_HAS_DP_DDR
516 Defines the SoC has DP-DDR used for DPAA.
518 CONFIG_SYS_FSL_SEC_BE
519 Defines the SEC controller register space as Big Endian
521 CONFIG_SYS_FSL_SEC_LE
522 Defines the SEC controller register space as Little Endian
525 CONFIG_SYS_INIT_SP_OFFSET
527 Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
528 pointer. This is needed for the temporary stack before
531 CONFIG_XWAY_SWAP_BYTES
533 Enable compilation of tools/xway-swap-bytes needed for Lantiq
534 XWAY SoCs for booting from NOR flash. The U-Boot image needs to
535 be swapped if a flash programmer is used.
538 CONFIG_SYS_EXCEPTION_VECTORS_HIGH
540 Select high exception vectors of the ARM core, e.g., do not
541 clear the V bit of the c1 register of CP15.
544 Generic timer clock source frequency.
546 COUNTER_FREQUENCY_REAL
547 Generic timer clock source frequency if the real clock is
548 different from COUNTER_FREQUENCY, and can only be determined
552 CONFIG_TEGRA_SUPPORT_NON_SECURE
554 Support executing U-Boot in non-secure (NS) mode. Certain
555 impossible actions will be skipped if the CPU is in NS mode,
556 such as ARM architectural timer initialization.
558 - Linux Kernel Interface:
559 CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]
561 When transferring memsize parameter to Linux, some versions
562 expect it to be in bytes, others in MB.
563 Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
567 New kernel versions are expecting firmware settings to be
568 passed using flattened device trees (based on open firmware
572 * New libfdt-based support
573 * Adds the "fdt" command
574 * The bootm command automatically updates the fdt
576 OF_TBCLK - The timebase frequency.
578 boards with QUICC Engines require OF_QE to set UCC MAC
581 CONFIG_OF_BOARD_SETUP
583 Board code has addition modification that it wants to make
584 to the flat device tree before handing it off to the kernel
586 CONFIG_OF_SYSTEM_SETUP
588 Other code has addition modification that it wants to make
589 to the flat device tree before handing it off to the kernel.
590 This causes ft_system_setup() to be called before booting
595 U-Boot can detect if an IDE device is present or not.
596 If not, and this new config option is activated, U-Boot
597 removes the ATA node from the DTS before booting Linux,
598 so the Linux IDE driver does not probe the device and
599 crash. This is needed for buggy hardware (uc101) where
600 no pull down resistor is connected to the signal IDE5V_DD7.
602 CONFIG_MACH_TYPE [relevant for ARM only][mandatory]
604 This setting is mandatory for all boards that have only one
605 machine type and must be used to specify the machine type
606 number as it appears in the ARM machine registry
607 (see https://www.arm.linux.org.uk/developer/machines/).
608 Only boards that have multiple machine types supported
609 in a single configuration file and the machine type is
610 runtime discoverable, do not have to use this setting.
612 - vxWorks boot parameters:
614 bootvx constructs a valid bootline using the following
615 environments variables: bootdev, bootfile, ipaddr, netmask,
616 serverip, gatewayip, hostname, othbootargs.
617 It loads the vxWorks image pointed bootfile.
619 Note: If a "bootargs" environment is defined, it will override
620 the defaults discussed just above.
622 - Cache Configuration:
623 CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
625 - Cache Configuration for ARM:
626 CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
628 CONFIG_SYS_PL310_BASE - Physical base address of PL310
629 controller register space
634 Define this if you want support for Amba PrimeCell PL011 UARTs.
638 If you have Amba PrimeCell PL011 UARTs, set this variable to
639 the clock speed of the UARTs.
643 If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
644 define this to a list of base addresses for each (supported)
645 port. See e.g. include/configs/versatile.h
647 CONFIG_SERIAL_HW_FLOW_CONTROL
649 Define this variable to enable hw flow control in serial driver.
650 Current user of this option is drivers/serial/nsl16550.c driver
654 Only needed when CONFIG_BOOTDELAY is enabled;
655 define a command string that is automatically executed
656 when no character is read on the console interface
657 within "Boot Delay" after reset.
659 CONFIG_RAMBOOT and CONFIG_NFSBOOT
660 The value of these goes into the environment as
661 "ramboot" and "nfsboot" respectively, and can be used
662 as a convenience, when switching between booting from
665 - Serial Download Echo Mode:
667 If defined to 1, all characters received during a
668 serial download (using the "loads" command) are
669 echoed back. This might be needed by some terminal
670 emulations (like "cu"), but may as well just take
671 time on others. This setting #define's the initial
672 value of the "loads_echo" environment variable.
674 - Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
676 Select one of the baudrates listed in
677 CONFIG_SYS_BAUDRATE_TABLE, see below.
679 - Removal of commands
680 If no commands are needed to boot, you can disable
681 CONFIG_CMDLINE to remove them. In this case, the command line
682 will not be available, and when U-Boot wants to execute the
683 boot command (on start-up) it will call board_run_command()
684 instead. This can reduce image size significantly for very
685 simple boot procedures.
687 - Regular expression support:
689 If this variable is defined, U-Boot is linked against
690 the SLRE (Super Light Regular Expression) library,
691 which adds regex support to some commands, as for
692 example "env grep" and "setexpr".
696 If this variable is defined, U-Boot will use a device tree
697 to configure its devices, instead of relying on statically
698 compiled #defines in the board file. This option is
699 experimental and only available on a few boards. The device
700 tree is available in the global data as gd->fdt_blob.
702 U-Boot needs to get its device tree from somewhere. This can
703 be done using one of the three options below:
706 If this variable is defined, U-Boot will embed a device tree
707 binary in its image. This device tree file should be in the
708 board directory and called <soc>-<board>.dts. The binary file
709 is then picked up in board_init_f() and made available through
710 the global data structure as gd->fdt_blob.
713 If this variable is defined, U-Boot will build a device tree
714 binary. It will be called u-boot.dtb. Architecture-specific
715 code will locate it at run-time. Generally this works by:
717 cat u-boot.bin u-boot.dtb >image.bin
719 and in fact, U-Boot does this for you, creating a file called
720 u-boot-dtb.bin which is useful in the common case. You can
721 still use the individual files if you need something more
725 If this variable is defined, U-Boot will use the device tree
726 provided by the board at runtime instead of embedding one with
727 the image. Only boards defining board_fdt_blob_setup() support
728 this option (see include/fdtdec.h file).
732 If this variable is defined, it enables watchdog
733 support for the SoC. There must be support in the SoC
734 specific code for a watchdog. For the 8xx
735 CPUs, the SIU Watchdog feature is enabled in the SYPCR
736 register. When supported for a specific SoC is
737 available, then no further board specific code should
741 When using a watchdog circuitry external to the used
742 SoC, then define this variable and provide board
743 specific code for the "hw_watchdog_reset" function.
745 CONFIG_SYS_WATCHDOG_FREQ
746 Some platforms automatically call WATCHDOG_RESET()
747 from the timer interrupt handler every
748 CONFIG_SYS_WATCHDOG_FREQ interrupts. If not set by the
749 board configuration file, a default of CONFIG_SYS_HZ/2
750 (i.e. 500) is used. Setting CONFIG_SYS_WATCHDOG_FREQ
751 to 0 disables calling WATCHDOG_RESET() from the timer
756 When CONFIG_CMD_DATE is selected, the type of the RTC
757 has to be selected, too. Define exactly one of the
760 CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
761 CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
762 CONFIG_RTC_MC146818 - use MC146818 RTC
763 CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
764 CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
765 CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
766 CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
767 CONFIG_RTC_DS164x - use Dallas DS164x RTC
768 CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
769 CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
770 CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
771 CONFIG_SYS_RV3029_TCR - enable trickle charger on
774 Note that if the RTC uses I2C, then the I2C interface
775 must also be configured. See I2C Support, below.
778 CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
780 The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
781 chip-ngpio pairs that tell the PCA953X driver the number of
782 pins supported by a particular chip.
784 Note that if the GPIO device uses I2C, then the I2C interface
785 must also be configured. See I2C Support, below.
788 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
789 accesses and can checksum them or write a list of them out
790 to memory. See the 'iotrace' command for details. This is
791 useful for testing device drivers since it can confirm that
792 the driver behaves the same way before and after a code
793 change. Currently this is supported on sandbox and arm. To
794 add support for your architecture, add '#include <iotrace.h>'
795 to the bottom of arch/<arch>/include/asm/io.h and test.
797 Example output from the 'iotrace stats' command is below.
798 Note that if the trace buffer is exhausted, the checksum will
799 still continue to operate.
802 Start: 10000000 (buffer start address)
803 Size: 00010000 (buffer size)
804 Offset: 00000120 (current buffer offset)
805 Output: 10000120 (start + offset)
806 Count: 00000018 (number of trace records)
807 CRC32: 9526fb66 (CRC32 of all trace records)
811 When CONFIG_TIMESTAMP is selected, the timestamp
812 (date and time) of an image is printed by image
813 commands like bootm or iminfo. This option is
814 automatically enabled when you select CONFIG_CMD_DATE .
816 - Partition Labels (disklabels) Supported:
817 Zero or more of the following:
818 CONFIG_MAC_PARTITION Apple's MacOS partition table.
819 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
820 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
821 bootloader. Note 2TB partition limit; see
823 CONFIG_SCSI) you must configure support for at
824 least one non-MTD partition type as well.
827 CONFIG_IDE_RESET_ROUTINE - this is defined in several
828 board configurations files but used nowhere!
830 CONFIG_IDE_RESET - is this is defined, IDE Reset will
831 be performed by calling the function
832 ide_set_reset(int reset)
833 which has to be defined in a board specific file
838 Set this to enable ATAPI support.
843 Set this to enable support for disks larger than 137GB
844 Also look at CONFIG_SYS_64BIT_LBA.
845 Whithout these , LBA48 support uses 32bit variables and will 'only'
846 support disks up to 2.1TB.
848 CONFIG_SYS_64BIT_LBA:
849 When enabled, makes the IDE subsystem use 64bit sector addresses.
853 CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
854 CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
855 CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
856 maximum numbers of LUNs, SCSI ID's and target
859 The environment variable 'scsidevs' is set to the number of
860 SCSI devices found during the last scan.
862 - NETWORK Support (PCI):
864 Support for Intel 8254x/8257x gigabit chips.
867 Utility code for direct access to the SPI bus on Intel 8257x.
868 This does not do anything useful unless you set at least one
869 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
871 CONFIG_E1000_SPI_GENERIC
872 Allow generic access to the SPI bus on the Intel 8257x, for
873 example with the "sspi" command.
876 Support for National dp83815 chips.
879 Support for National dp8382[01] gigabit chips.
881 - NETWORK Support (other):
883 CONFIG_DRIVER_AT91EMAC
884 Support for AT91RM9200 EMAC.
887 Define this to use reduced MII inteface
889 CONFIG_DRIVER_AT91EMAC_QUIET
890 If this defined, the driver is quiet.
891 The driver doen't show link status messages.
894 Support for the Calxeda XGMAC device
897 Support for SMSC's LAN91C96 chips.
899 CONFIG_LAN91C96_USE_32_BIT
900 Define this to enable 32 bit addressing
903 Support for SMSC's LAN91C111 chip
906 Define this to hold the physical address
907 of the device (I/O space)
909 CONFIG_SMC_USE_32_BIT
910 Define this if data bus is 32 bits
912 CONFIG_SMC_USE_IOFUNCS
913 Define this to use i/o functions instead of macros
914 (some hardware wont work with macros)
916 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
917 Define this if you have more then 3 PHYs.
920 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
922 CONFIG_FTGMAC100_EGIGA
923 Define this to use GE link update with gigabit PHY.
924 Define this if FTGMAC100 is connected to gigabit PHY.
925 If your system has 10/100 PHY only, it might not occur
926 wrong behavior. Because PHY usually return timeout or
927 useless data when polling gigabit status and gigabit
928 control registers. This behavior won't affect the
929 correctnessof 10/100 link speed update.
932 Support for Renesas on-chip Ethernet controller
934 CONFIG_SH_ETHER_USE_PORT
935 Define the number of ports to be used
937 CONFIG_SH_ETHER_PHY_ADDR
938 Define the ETH PHY's address
940 CONFIG_SH_ETHER_CACHE_WRITEBACK
941 If this option is set, the driver enables cache flush.
947 CONFIG_TPM_TIS_INFINEON
948 Support for Infineon i2c bus TPM devices. Only one device
949 per system is supported at this time.
951 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
952 Define the burst count bytes upper limit
955 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
957 CONFIG_TPM_ST33ZP24_I2C
958 Support for STMicroelectronics ST33ZP24 I2C devices.
959 Requires TPM_ST33ZP24 and I2C.
961 CONFIG_TPM_ST33ZP24_SPI
962 Support for STMicroelectronics ST33ZP24 SPI devices.
963 Requires TPM_ST33ZP24 and SPI.
966 Support for Atmel TWI TPM device. Requires I2C support.
969 Support for generic parallel port TPM devices. Only one device
970 per system is supported at this time.
972 CONFIG_TPM_TIS_BASE_ADDRESS
973 Base address where the generic TPM device is mapped
974 to. Contemporary x86 systems usually map it at
978 Define this to enable the TPM support library which provides
979 functional interfaces to some TPM commands.
980 Requires support for a TPM device.
982 CONFIG_TPM_AUTH_SESSIONS
983 Define this to enable authorized functions in the TPM library.
984 Requires CONFIG_TPM and CONFIG_SHA1.
987 At the moment only the UHCI host controller is
988 supported (PIP405, MIP405); define
989 CONFIG_USB_UHCI to enable it.
990 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
991 and define CONFIG_USB_STORAGE to enable the USB
994 Supported are USB Keyboards and USB Floppy drives
997 CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
998 txfilltuning field in the EHCI controller on reset.
1000 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1001 HW module registers.
1004 Define the below if you wish to use the USB console.
1005 Once firmware is rebuilt from a serial console issue the
1006 command "setenv stdin usbtty; setenv stdout usbtty" and
1007 attach your USB cable. The Unix command "dmesg" should print
1008 it has found a new device. The environment variable usbtty
1009 can be set to gserial or cdc_acm to enable your device to
1010 appear to a USB host as a Linux gserial device or a
1011 Common Device Class Abstract Control Model serial device.
1012 If you select usbtty = gserial you should be able to enumerate
1014 # modprobe usbserial vendor=0xVendorID product=0xProductID
1015 else if using cdc_acm, simply setting the environment
1016 variable usbtty to be cdc_acm should suffice. The following
1017 might be defined in YourBoardName.h
1020 Define this to build a UDC device
1023 Define this to have a tty type of device available to
1024 talk to the UDC device
1027 Define this to enable the high speed support for usb
1028 device and usbtty. If this feature is enabled, a routine
1029 int is_usbd_high_speed(void)
1030 also needs to be defined by the driver to dynamically poll
1031 whether the enumeration has succeded at high speed or full
1034 CONFIG_SYS_CONSOLE_IS_IN_ENV
1035 Define this if you want stdin, stdout &/or stderr to
1038 If you have a USB-IF assigned VendorID then you may wish to
1039 define your own vendor specific values either in BoardName.h
1040 or directly in usbd_vendor_info.h. If you don't define
1041 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1042 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1043 should pretend to be a Linux device to it's target host.
1045 CONFIG_USBD_MANUFACTURER
1046 Define this string as the name of your company for
1047 - CONFIG_USBD_MANUFACTURER "my company"
1049 CONFIG_USBD_PRODUCT_NAME
1050 Define this string as the name of your product
1051 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1053 CONFIG_USBD_VENDORID
1054 Define this as your assigned Vendor ID from the USB
1055 Implementors Forum. This *must* be a genuine Vendor ID
1056 to avoid polluting the USB namespace.
1057 - CONFIG_USBD_VENDORID 0xFFFF
1059 CONFIG_USBD_PRODUCTID
1060 Define this as the unique Product ID
1062 - CONFIG_USBD_PRODUCTID 0xFFFF
1064 - ULPI Layer Support:
1065 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1066 the generic ULPI layer. The generic layer accesses the ULPI PHY
1067 via the platform viewport, so you need both the genric layer and
1068 the viewport enabled. Currently only Chipidea/ARC based
1069 viewport is supported.
1070 To enable the ULPI layer support, define CONFIG_USB_ULPI and
1071 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1072 If your ULPI phy needs a different reference clock than the
1073 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1074 the appropriate value in Hz.
1077 The MMC controller on the Intel PXA is supported. To
1078 enable this define CONFIG_MMC. The MMC can be
1079 accessed from the boot prompt by mapping the device
1080 to physical memory similar to flash. Command line is
1081 enabled with CONFIG_CMD_MMC. The MMC driver also works with
1082 the FAT fs. This is enabled with CONFIG_CMD_FAT.
1085 Support for Renesas on-chip MMCIF controller
1087 CONFIG_SH_MMCIF_ADDR
1088 Define the base address of MMCIF registers
1091 Define the clock frequency for MMCIF
1093 - USB Device Firmware Update (DFU) class support:
1095 This enables the USB portion of the DFU USB class
1098 This enables support for exposing NAND devices via DFU.
1101 This enables support for exposing RAM via DFU.
1102 Note: DFU spec refer to non-volatile memory usage, but
1103 allow usages beyond the scope of spec - here RAM usage,
1104 one that would help mostly the developer.
1106 CONFIG_SYS_DFU_DATA_BUF_SIZE
1107 Dfu transfer uses a buffer before writing data to the
1108 raw storage device. Make the size (in bytes) of this buffer
1109 configurable. The size of this buffer is also configurable
1110 through the "dfu_bufsiz" environment variable.
1112 CONFIG_SYS_DFU_MAX_FILE_SIZE
1113 When updating files rather than the raw storage device,
1114 we use a static buffer to copy the file into and then write
1115 the buffer once we've been given the whole file. Define
1116 this to the maximum filesize (in bytes) for the buffer.
1117 Default is 4 MiB if undefined.
1119 DFU_DEFAULT_POLL_TIMEOUT
1120 Poll timeout [ms], is the timeout a device can send to the
1121 host. The host must wait for this timeout before sending
1122 a subsequent DFU_GET_STATUS request to the device.
1124 DFU_MANIFEST_POLL_TIMEOUT
1125 Poll timeout [ms], which the device sends to the host when
1126 entering dfuMANIFEST state. Host waits this timeout, before
1127 sending again an USB request to the device.
1129 - Journaling Flash filesystem support:
1131 Define these for a default partition on a NAND device
1133 CONFIG_SYS_JFFS2_FIRST_SECTOR,
1134 CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1135 Define these for a default partition on a NOR device
1138 See Kconfig help for available keyboard drivers.
1142 Define this to enable a custom keyboard support.
1143 This simply calls drv_keyboard_init() which must be
1144 defined in your board-specific files. This option is deprecated
1145 and is only used by novena. For new boards, use driver model
1150 Enable the Freescale DIU video driver. Reference boards for
1151 SOCs that have a DIU should define this macro to enable DIU
1152 support, and should also define these other macros:
1157 CONFIG_VIDEO_SW_CURSOR
1158 CONFIG_VGA_AS_SINGLE_DEVICE
1160 CONFIG_VIDEO_BMP_LOGO
1162 The DIU driver will look for the 'video-mode' environment
1163 variable, and if defined, enable the DIU as a console during
1164 boot. See the documentation file doc/README.video for a
1165 description of this variable.
1167 - LCD Support: CONFIG_LCD
1169 Define this to enable LCD support (for output to LCD
1170 display); also select one of the supported displays
1171 by defining one of these:
1175 HITACHI TX09D70VM1CCA, 3.5", 240x320.
1177 CONFIG_NEC_NL6448AC33:
1179 NEC NL6448AC33-18. Active, color, single scan.
1181 CONFIG_NEC_NL6448BC20
1183 NEC NL6448BC20-08. 6.5", 640x480.
1184 Active, color, single scan.
1186 CONFIG_NEC_NL6448BC33_54
1188 NEC NL6448BC33-54. 10.4", 640x480.
1189 Active, color, single scan.
1193 Sharp 320x240. Active, color, single scan.
1194 It isn't 16x9, and I am not sure what it is.
1196 CONFIG_SHARP_LQ64D341
1198 Sharp LQ64D341 display, 640x480.
1199 Active, color, single scan.
1203 HLD1045 display, 640x480.
1204 Active, color, single scan.
1208 Optrex CBL50840-2 NF-FW 99 22 M5
1210 Hitachi LMG6912RPFC-00T
1214 320x240. Black & white.
1216 CONFIG_LCD_ALIGNMENT
1218 Normally the LCD is page-aligned (typically 4KB). If this is
1219 defined then the LCD will be aligned to this value instead.
1220 For ARM it is sometimes useful to use MMU_SECTION_SIZE
1221 here, since it is cheaper to change data cache settings on
1222 a per-section basis.
1227 Sometimes, for example if the display is mounted in portrait
1228 mode or even if it's mounted landscape but rotated by 180degree,
1229 we need to rotate our content of the display relative to the
1230 framebuffer, so that user can read the messages which are
1232 Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1233 initialized with a given rotation from "vl_rot" out of
1234 "vidinfo_t" which is provided by the board specific code.
1235 The value for vl_rot is coded as following (matching to
1236 fbcon=rotate:<n> linux-kernel commandline):
1237 0 = no rotation respectively 0 degree
1238 1 = 90 degree rotation
1239 2 = 180 degree rotation
1240 3 = 270 degree rotation
1242 If CONFIG_LCD_ROTATION is not defined, the console will be
1243 initialized with 0degree rotation.
1247 Support drawing of RLE8-compressed bitmaps on the LCD.
1251 Enables an 'i2c edid' command which can read EDID
1252 information over I2C from an attached LCD display.
1255 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1257 The clock frequency of the MII bus
1259 CONFIG_PHY_RESET_DELAY
1261 Some PHY like Intel LXT971A need extra delay after
1262 reset before any MII register access is possible.
1263 For such PHY, set this option to the usec delay
1264 required. (minimum 300usec for LXT971A)
1266 CONFIG_PHY_CMD_DELAY (ppc4xx)
1268 Some PHY like Intel LXT971A need extra delay after
1269 command issued before MII status register can be read
1274 Define a default value for the IP address to use for
1275 the default Ethernet interface, in case this is not
1276 determined through e.g. bootp.
1277 (Environment variable "ipaddr")
1279 - Server IP address:
1282 Defines a default value for the IP address of a TFTP
1283 server to contact when using the "tftboot" command.
1284 (Environment variable "serverip")
1286 CONFIG_KEEP_SERVERADDR
1288 Keeps the server's MAC address, in the env 'serveraddr'
1289 for passing to bootargs (like Linux's netconsole option)
1291 - Gateway IP address:
1294 Defines a default value for the IP address of the
1295 default router where packets to other networks are
1297 (Environment variable "gatewayip")
1302 Defines a default value for the subnet mask (or
1303 routing prefix) which is used to determine if an IP
1304 address belongs to the local subnet or needs to be
1305 forwarded through a router.
1306 (Environment variable "netmask")
1308 - BOOTP Recovery Mode:
1309 CONFIG_BOOTP_RANDOM_DELAY
1311 If you have many targets in a network that try to
1312 boot using BOOTP, you may want to avoid that all
1313 systems send out BOOTP requests at precisely the same
1314 moment (which would happen for instance at recovery
1315 from a power failure, when all systems will try to
1316 boot, thus flooding the BOOTP server. Defining
1317 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1318 inserted before sending out BOOTP requests. The
1319 following delays are inserted then:
1321 1st BOOTP request: delay 0 ... 1 sec
1322 2nd BOOTP request: delay 0 ... 2 sec
1323 3rd BOOTP request: delay 0 ... 4 sec
1325 BOOTP requests: delay 0 ... 8 sec
1327 CONFIG_BOOTP_ID_CACHE_SIZE
1329 BOOTP packets are uniquely identified using a 32-bit ID. The
1330 server will copy the ID from client requests to responses and
1331 U-Boot will use this to determine if it is the destination of
1332 an incoming response. Some servers will check that addresses
1333 aren't in use before handing them out (usually using an ARP
1334 ping) and therefore take up to a few hundred milliseconds to
1335 respond. Network congestion may also influence the time it
1336 takes for a response to make it back to the client. If that
1337 time is too long, U-Boot will retransmit requests. In order
1338 to allow earlier responses to still be accepted after these
1339 retransmissions, U-Boot's BOOTP client keeps a small cache of
1340 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1341 cache. The default is to keep IDs for up to four outstanding
1342 requests. Increasing this will allow U-Boot to accept offers
1343 from a BOOTP client in networks with unusually high latency.
1345 - DHCP Advanced Options:
1346 You can fine tune the DHCP functionality by defining
1347 CONFIG_BOOTP_* symbols:
1349 CONFIG_BOOTP_NISDOMAIN
1350 CONFIG_BOOTP_BOOTFILESIZE
1351 CONFIG_BOOTP_NTPSERVER
1352 CONFIG_BOOTP_TIMEOFFSET
1353 CONFIG_BOOTP_VENDOREX
1354 CONFIG_BOOTP_MAY_FAIL
1356 CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1357 environment variable, not the BOOTP server.
1359 CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1360 after the configured retry count, the call will fail
1361 instead of starting over. This can be used to fail over
1362 to Link-local IP address configuration if the DHCP server
1365 CONFIG_BOOTP_DHCP_REQUEST_DELAY
1367 A 32bit value in microseconds for a delay between
1368 receiving a "DHCP Offer" and sending the "DHCP Request".
1369 This fixes a problem with certain DHCP servers that don't
1370 respond 100% of the time to a "DHCP request". E.g. On an
1371 AT91RM9200 processor running at 180MHz, this delay needed
1372 to be *at least* 15,000 usec before a Windows Server 2003
1373 DHCP server would reply 100% of the time. I recommend at
1374 least 50,000 usec to be safe. The alternative is to hope
1375 that one of the retries will be successful but note that
1376 the DHCP timeout and retry process takes a longer than
1379 - Link-local IP address negotiation:
1380 Negotiate with other link-local clients on the local network
1381 for an address that doesn't require explicit configuration.
1382 This is especially useful if a DHCP server cannot be guaranteed
1383 to exist in all environments that the device must operate.
1385 See doc/README.link-local for more information.
1387 - MAC address from environment variables
1389 FDT_SEQ_MACADDR_FROM_ENV
1391 Fix-up device tree with MAC addresses fetched sequentially from
1392 environment variables. This config work on assumption that
1393 non-usable ethernet node of device-tree are either not present
1394 or their status has been marked as "disabled".
1397 CONFIG_CDP_DEVICE_ID
1399 The device id used in CDP trigger frames.
1401 CONFIG_CDP_DEVICE_ID_PREFIX
1403 A two character string which is prefixed to the MAC address
1408 A printf format string which contains the ascii name of
1409 the port. Normally is set to "eth%d" which sets
1410 eth0 for the first Ethernet, eth1 for the second etc.
1412 CONFIG_CDP_CAPABILITIES
1414 A 32bit integer which indicates the device capabilities;
1415 0x00000010 for a normal host which does not forwards.
1419 An ascii string containing the version of the software.
1423 An ascii string containing the name of the platform.
1427 A 32bit integer sent on the trigger.
1429 CONFIG_CDP_POWER_CONSUMPTION
1431 A 16bit integer containing the power consumption of the
1432 device in .1 of milliwatts.
1434 CONFIG_CDP_APPLIANCE_VLAN_TYPE
1436 A byte containing the id of the VLAN.
1438 - Status LED: CONFIG_LED_STATUS
1440 Several configurations allow to display the current
1441 status using a LED. For instance, the LED will blink
1442 fast while running U-Boot code, stop blinking as
1443 soon as a reply to a BOOTP request was received, and
1444 start blinking slow once the Linux kernel is running
1445 (supported by a status LED driver in the Linux
1446 kernel). Defining CONFIG_LED_STATUS enables this
1451 CONFIG_LED_STATUS_GPIO
1452 The status LED can be connected to a GPIO pin.
1453 In such cases, the gpio_led driver can be used as a
1454 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1455 to include the gpio_led driver in the U-Boot binary.
1457 CONFIG_GPIO_LED_INVERTED_TABLE
1458 Some GPIO connected LEDs may have inverted polarity in which
1459 case the GPIO high value corresponds to LED off state and
1460 GPIO low value corresponds to LED on state.
1461 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1462 with a list of GPIO LEDs that have inverted polarity.
1465 CONFIG_SYS_NUM_I2C_BUSES
1466 Hold the number of i2c buses you want to use.
1468 CONFIG_SYS_I2C_DIRECT_BUS
1469 define this, if you don't use i2c muxes on your hardware.
1470 if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1473 CONFIG_SYS_I2C_MAX_HOPS
1474 define how many muxes are maximal consecutively connected
1475 on one i2c bus. If you not use i2c muxes, omit this
1478 CONFIG_SYS_I2C_BUSES
1479 hold a list of buses you want to use, only used if
1480 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1481 a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1482 CONFIG_SYS_NUM_I2C_BUSES = 9:
1484 CONFIG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
1485 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1486 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1487 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1488 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1489 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1490 {1, {I2C_NULL_HOP}}, \
1491 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1492 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1496 bus 0 on adapter 0 without a mux
1497 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1498 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1499 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1500 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1501 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1502 bus 6 on adapter 1 without a mux
1503 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1504 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1506 If you do not have i2c muxes on your board, omit this define.
1508 - Legacy I2C Support:
1509 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1510 then the following macros need to be defined (examples are
1511 from include/configs/lwmon.h):
1515 (Optional). Any commands necessary to enable the I2C
1516 controller or configure ports.
1518 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
1522 The code necessary to make the I2C data line active
1523 (driven). If the data line is open collector, this
1526 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
1530 The code necessary to make the I2C data line tri-stated
1531 (inactive). If the data line is open collector, this
1534 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1538 Code that returns true if the I2C data line is high,
1541 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1545 If <bit> is true, sets the I2C data line high. If it
1546 is false, it clears it (low).
1548 eg: #define I2C_SDA(bit) \
1549 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
1550 else immr->im_cpm.cp_pbdat &= ~PB_SDA
1554 If <bit> is true, sets the I2C clock line high. If it
1555 is false, it clears it (low).
1557 eg: #define I2C_SCL(bit) \
1558 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
1559 else immr->im_cpm.cp_pbdat &= ~PB_SCL
1563 This delay is invoked four times per clock cycle so this
1564 controls the rate of data transfer. The data rate thus
1565 is 1 / (I2C_DELAY * 4). Often defined to be something
1568 #define I2C_DELAY udelay(2)
1570 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1572 If your arch supports the generic GPIO framework (asm/gpio.h),
1573 then you may alternatively define the two GPIOs that are to be
1574 used as SCL / SDA. Any of the previous I2C_xxx macros will
1575 have GPIO-based defaults assigned to them as appropriate.
1577 You should define these to the GPIO value as given directly to
1578 the generic GPIO functions.
1580 CONFIG_SYS_I2C_INIT_BOARD
1582 When a board is reset during an i2c bus transfer
1583 chips might think that the current transfer is still
1584 in progress. On some boards it is possible to access
1585 the i2c SCLK line directly, either by using the
1586 processor pin as a GPIO or by having a second pin
1587 connected to the bus. If this option is defined a
1588 custom i2c_init_board() routine in boards/xxx/board.c
1589 is run early in the boot sequence.
1591 CONFIG_I2C_MULTI_BUS
1593 This option allows the use of multiple I2C buses, each of which
1594 must have a controller. At any point in time, only one bus is
1595 active. To switch to a different bus, use the 'i2c dev' command.
1596 Note that bus numbering is zero-based.
1598 CONFIG_SYS_I2C_NOPROBES
1600 This option specifies a list of I2C devices that will be skipped
1601 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
1602 is set, specify a list of bus-device pairs. Otherwise, specify
1603 a 1D array of device addresses
1606 #undef CONFIG_I2C_MULTI_BUS
1607 #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1609 will skip addresses 0x50 and 0x68 on a board with one I2C bus
1611 #define CONFIG_I2C_MULTI_BUS
1612 #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1614 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1616 CONFIG_SYS_SPD_BUS_NUM
1618 If defined, then this indicates the I2C bus number for DDR SPD.
1619 If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1621 CONFIG_SYS_RTC_BUS_NUM
1623 If defined, then this indicates the I2C bus number for the RTC.
1624 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1626 CONFIG_SOFT_I2C_READ_REPEATED_START
1628 defining this will force the i2c_read() function in
1629 the soft_i2c driver to perform an I2C repeated start
1630 between writing the address pointer and reading the
1631 data. If this define is omitted the default behaviour
1632 of doing a stop-start sequence will be used. Most I2C
1633 devices can use either method, but some require one or
1636 - SPI Support: CONFIG_SPI
1638 Enables SPI driver (so far only tested with
1639 SPI EEPROM, also an instance works with Crystal A/D and
1640 D/As on the SACSng board)
1644 Enables a software (bit-bang) SPI driver rather than
1645 using hardware support. This is a general purpose
1646 driver that only requires three general I/O port pins
1647 (two outputs, one input) to function. If this is
1648 defined, the board configuration must define several
1649 SPI configuration items (port pins to use, etc). For
1650 an example, see include/configs/sacsng.h.
1652 CONFIG_SYS_SPI_MXC_WAIT
1653 Timeout for waiting until spi transfer completed.
1654 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1656 - FPGA Support: CONFIG_FPGA
1658 Enables FPGA subsystem.
1660 CONFIG_FPGA_<vendor>
1662 Enables support for specific chip vendors.
1665 CONFIG_FPGA_<family>
1667 Enables support for FPGA family.
1668 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1672 Specify the number of FPGA devices to support.
1674 CONFIG_SYS_FPGA_PROG_FEEDBACK
1676 Enable printing of hash marks during FPGA configuration.
1678 CONFIG_SYS_FPGA_CHECK_BUSY
1680 Enable checks on FPGA configuration interface busy
1681 status by the configuration function. This option
1682 will require a board or device specific function to
1687 If defined, a function that provides delays in the FPGA
1688 configuration driver.
1690 CONFIG_SYS_FPGA_CHECK_CTRLC
1691 Allow Control-C to interrupt FPGA configuration
1693 CONFIG_SYS_FPGA_CHECK_ERROR
1695 Check for configuration errors during FPGA bitfile
1696 loading. For example, abort during Virtex II
1697 configuration if the INIT_B line goes low (which
1698 indicated a CRC error).
1700 CONFIG_SYS_FPGA_WAIT_INIT
1702 Maximum time to wait for the INIT_B line to de-assert
1703 after PROB_B has been de-asserted during a Virtex II
1704 FPGA configuration sequence. The default time is 500
1707 CONFIG_SYS_FPGA_WAIT_BUSY
1709 Maximum time to wait for BUSY to de-assert during
1710 Virtex II FPGA configuration. The default is 5 ms.
1712 CONFIG_SYS_FPGA_WAIT_CONFIG
1714 Time to wait after FPGA configuration. The default is
1717 - Configuration Management:
1721 If defined, this string will be added to the U-Boot
1722 version information (U_BOOT_VERSION)
1724 - Vendor Parameter Protection:
1726 U-Boot considers the values of the environment
1727 variables "serial#" (Board Serial Number) and
1728 "ethaddr" (Ethernet Address) to be parameters that
1729 are set once by the board vendor / manufacturer, and
1730 protects these variables from casual modification by
1731 the user. Once set, these variables are read-only,
1732 and write or delete attempts are rejected. You can
1733 change this behaviour:
1735 If CONFIG_ENV_OVERWRITE is #defined in your config
1736 file, the write protection for vendor parameters is
1737 completely disabled. Anybody can change or delete
1740 Alternatively, if you define _both_ an ethaddr in the
1741 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1742 Ethernet address is installed in the environment,
1743 which can be changed exactly ONCE by the user. [The
1744 serial# is unaffected by this, i. e. it remains
1747 The same can be accomplished in a more flexible way
1748 for any variable by configuring the type of access
1749 to allow for those variables in the ".flags" variable
1750 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1755 Define this variable to enable the reservation of
1756 "protected RAM", i. e. RAM which is not overwritten
1757 by U-Boot. Define CONFIG_PRAM to hold the number of
1758 kB you want to reserve for pRAM. You can overwrite
1759 this default value by defining an environment
1760 variable "pram" to the number of kB you want to
1761 reserve. Note that the board info structure will
1762 still show the full amount of RAM. If pRAM is
1763 reserved, a new environment variable "mem" will
1764 automatically be defined to hold the amount of
1765 remaining RAM in a form that can be passed as boot
1766 argument to Linux, for instance like that:
1768 setenv bootargs ... mem=\${mem}
1771 This way you can tell Linux not to use this memory,
1772 either, which results in a memory region that will
1773 not be affected by reboots.
1775 *WARNING* If your board configuration uses automatic
1776 detection of the RAM size, you must make sure that
1777 this memory test is non-destructive. So far, the
1778 following board configurations are known to be
1781 IVMS8, IVML24, SPD8xx,
1782 HERMES, IP860, RPXlite, LWMON,
1785 - Access to physical memory region (> 4GB)
1786 Some basic support is provided for operations on memory not
1787 normally accessible to U-Boot - e.g. some architectures
1788 support access to more than 4GB of memory on 32-bit
1789 machines using physical address extension or similar.
1790 Define CONFIG_PHYSMEM to access this basic support, which
1791 currently only supports clearing the memory.
1794 CONFIG_NET_RETRY_COUNT
1796 This variable defines the number of retries for
1797 network operations like ARP, RARP, TFTP, or BOOTP
1798 before giving up the operation. If not defined, a
1799 default value of 5 is used.
1803 Timeout waiting for an ARP reply in milliseconds.
1807 Timeout in milliseconds used in NFS protocol.
1808 If you encounter "ERROR: Cannot umount" in nfs command,
1809 try longer timeout such as
1810 #define CONFIG_NFS_TIMEOUT 10000UL
1814 In the current implementation, the local variables
1815 space and global environment variables space are
1816 separated. Local variables are those you define by
1817 simply typing `name=value'. To access a local
1818 variable later on, you have write `$name' or
1819 `${name}'; to execute the contents of a variable
1820 directly type `$name' at the command prompt.
1822 Global environment variables are those you use
1823 setenv/printenv to work with. To run a command stored
1824 in such a variable, you need to use the run command,
1825 and you must not use the '$' sign to access them.
1827 To store commands and special characters in a
1828 variable, please use double quotation marks
1829 surrounding the whole text of the variable, instead
1830 of the backslashes before semicolons and special
1833 - Command Line Editing and History:
1834 CONFIG_CMDLINE_PS_SUPPORT
1836 Enable support for changing the command prompt string
1837 at run-time. Only static string is supported so far.
1838 The string is obtained from environment variables PS1
1841 - Default Environment:
1842 CONFIG_EXTRA_ENV_SETTINGS
1844 Define this to contain any number of null terminated
1845 strings (variable = value pairs) that will be part of
1846 the default environment compiled into the boot image.
1848 For example, place something like this in your
1849 board's config file:
1851 #define CONFIG_EXTRA_ENV_SETTINGS \
1855 Warning: This method is based on knowledge about the
1856 internal format how the environment is stored by the
1857 U-Boot code. This is NOT an official, exported
1858 interface! Although it is unlikely that this format
1859 will change soon, there is no guarantee either.
1860 You better know what you are doing here.
1862 Note: overly (ab)use of the default environment is
1863 discouraged. Make sure to check other ways to preset
1864 the environment like the "source" command or the
1867 CONFIG_DELAY_ENVIRONMENT
1869 Normally the environment is loaded when the board is
1870 initialised so that it is available to U-Boot. This inhibits
1871 that so that the environment is not available until
1872 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1873 this is instead controlled by the value of
1874 /config/load-environment.
1876 - TFTP Fixed UDP Port:
1879 If this is defined, the environment variable tftpsrcp
1880 is used to supply the TFTP UDP source port value.
1881 If tftpsrcp isn't defined, the normal pseudo-random port
1882 number generator is used.
1884 Also, the environment variable tftpdstp is used to supply
1885 the TFTP UDP destination port value. If tftpdstp isn't
1886 defined, the normal port 69 is used.
1888 The purpose for tftpsrcp is to allow a TFTP server to
1889 blindly start the TFTP transfer using the pre-configured
1890 target IP address and UDP port. This has the effect of
1891 "punching through" the (Windows XP) firewall, allowing
1892 the remainder of the TFTP transfer to proceed normally.
1893 A better solution is to properly configure the firewall,
1894 but sometimes that is not allowed.
1896 CONFIG_STANDALONE_LOAD_ADDR
1898 This option defines a board specific value for the
1899 address where standalone program gets loaded, thus
1900 overwriting the architecture dependent default
1903 - Frame Buffer Address:
1906 Define CONFIG_FB_ADDR if you want to use specific
1907 address for frame buffer. This is typically the case
1908 when using a graphics controller has separate video
1909 memory. U-Boot will then place the frame buffer at
1910 the given address instead of dynamically reserving it
1911 in system RAM by calling lcd_setmem(), which grabs
1912 the memory for the frame buffer depending on the
1913 configured panel size.
1915 Please see board_init_f function.
1917 - Automatic software updates via TFTP server
1919 CONFIG_UPDATE_TFTP_CNT_MAX
1920 CONFIG_UPDATE_TFTP_MSEC_MAX
1922 These options enable and control the auto-update feature;
1923 for a more detailed description refer to doc/README.update.
1925 - MTD Support (mtdparts command, UBI support)
1926 CONFIG_MTD_UBI_WL_THRESHOLD
1927 This parameter defines the maximum difference between the highest
1928 erase counter value and the lowest erase counter value of eraseblocks
1929 of UBI devices. When this threshold is exceeded, UBI starts performing
1930 wear leveling by means of moving data from eraseblock with low erase
1931 counter to eraseblocks with high erase counter.
1933 The default value should be OK for SLC NAND flashes, NOR flashes and
1934 other flashes which have eraseblock life-cycle 100000 or more.
1935 However, in case of MLC NAND flashes which typically have eraseblock
1936 life-cycle less than 10000, the threshold should be lessened (e.g.,
1937 to 128 or 256, although it does not have to be power of 2).
1941 CONFIG_MTD_UBI_BEB_LIMIT
1942 This option specifies the maximum bad physical eraseblocks UBI
1943 expects on the MTD device (per 1024 eraseblocks). If the
1944 underlying flash does not admit of bad eraseblocks (e.g. NOR
1945 flash), this value is ignored.
1947 NAND datasheets often specify the minimum and maximum NVM
1948 (Number of Valid Blocks) for the flashes' endurance lifetime.
1949 The maximum expected bad eraseblocks per 1024 eraseblocks
1950 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1951 which gives 20 for most NANDs (MaxNVB is basically the total
1952 count of eraseblocks on the chip).
1954 To put it differently, if this value is 20, UBI will try to
1955 reserve about 1.9% of physical eraseblocks for bad blocks
1956 handling. And that will be 1.9% of eraseblocks on the entire
1957 NAND chip, not just the MTD partition UBI attaches. This means
1958 that if you have, say, a NAND flash chip admits maximum 40 bad
1959 eraseblocks, and it is split on two MTD partitions of the same
1960 size, UBI will reserve 40 eraseblocks when attaching a
1965 CONFIG_MTD_UBI_FASTMAP
1966 Fastmap is a mechanism which allows attaching an UBI device
1967 in nearly constant time. Instead of scanning the whole MTD device it
1968 only has to locate a checkpoint (called fastmap) on the device.
1969 The on-flash fastmap contains all information needed to attach
1970 the device. Using fastmap makes only sense on large devices where
1971 attaching by scanning takes long. UBI will not automatically install
1972 a fastmap on old images, but you can set the UBI parameter
1973 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1974 that fastmap-enabled images are still usable with UBI implementations
1975 without fastmap support. On typical flash devices the whole fastmap
1976 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1978 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1979 Set this parameter to enable fastmap automatically on images
1983 CONFIG_MTD_UBI_FM_DEBUG
1984 Enable UBI fastmap debug
1989 Enable building of SPL globally.
1992 LDSCRIPT for linking the SPL binary.
1994 CONFIG_SPL_MAX_FOOTPRINT
1995 Maximum size in memory allocated to the SPL, BSS included.
1996 When defined, the linker checks that the actual memory
1997 used by SPL from _start to __bss_end does not exceed it.
1998 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
1999 must not be both defined at the same time.
2002 Maximum size of the SPL image (text, data, rodata, and
2003 linker lists sections), BSS excluded.
2004 When defined, the linker checks that the actual size does
2007 CONFIG_SPL_RELOC_TEXT_BASE
2008 Address to relocate to. If unspecified, this is equal to
2009 CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2011 CONFIG_SPL_BSS_START_ADDR
2012 Link address for the BSS within the SPL binary.
2014 CONFIG_SPL_BSS_MAX_SIZE
2015 Maximum size in memory allocated to the SPL BSS.
2016 When defined, the linker checks that the actual memory used
2017 by SPL from __bss_start to __bss_end does not exceed it.
2018 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2019 must not be both defined at the same time.
2022 Adress of the start of the stack SPL will use
2024 CONFIG_SPL_PANIC_ON_RAW_IMAGE
2025 When defined, SPL will panic() if the image it has
2026 loaded does not have a signature.
2027 Defining this is useful when code which loads images
2028 in SPL cannot guarantee that absolutely all read errors
2030 An example is the LPC32XX MLC NAND driver, which will
2031 consider that a completely unreadable NAND block is bad,
2032 and thus should be skipped silently.
2034 CONFIG_SPL_RELOC_STACK
2035 Adress of the start of the stack SPL will use after
2036 relocation. If unspecified, this is equal to
2039 CONFIG_SYS_SPL_MALLOC_START
2040 Starting address of the malloc pool used in SPL.
2041 When this option is set the full malloc is used in SPL and
2042 it is set up by spl_init() and before that, the simple malloc()
2043 can be used if CONFIG_SYS_MALLOC_F is defined.
2045 CONFIG_SYS_SPL_MALLOC_SIZE
2046 The size of the malloc pool used in SPL.
2049 Enable booting directly to an OS from SPL.
2050 See also: doc/README.falcon
2052 CONFIG_SPL_DISPLAY_PRINT
2053 For ARM, enable an optional function to print more information
2054 about the running system.
2056 CONFIG_SPL_INIT_MINIMAL
2057 Arch init code should be built for a very small image
2059 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2060 Partition on the MMC to load U-Boot from when the MMC is being
2063 CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2064 Sector to load kernel uImage from when MMC is being
2065 used in raw mode (for Falcon mode)
2067 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2068 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2069 Sector and number of sectors to load kernel argument
2070 parameters from when MMC is being used in raw mode
2073 CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2074 Filename to read to load U-Boot when reading from filesystem
2076 CONFIG_SPL_FS_LOAD_KERNEL_NAME
2077 Filename to read to load kernel uImage when reading
2078 from filesystem (for Falcon mode)
2080 CONFIG_SPL_FS_LOAD_ARGS_NAME
2081 Filename to read to load kernel argument parameters
2082 when reading from filesystem (for Falcon mode)
2084 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2085 Set this for NAND SPL on PPC mpc83xx targets, so that
2086 start.S waits for the rest of the SPL to load before
2087 continuing (the hardware starts execution after just
2088 loading the first page rather than the full 4K).
2090 CONFIG_SPL_SKIP_RELOCATE
2091 Avoid SPL relocation
2093 CONFIG_SPL_NAND_IDENT
2094 SPL uses the chip ID list to identify the NAND flash.
2095 Requires CONFIG_SPL_NAND_BASE.
2098 Support for a lightweight UBI (fastmap) scanner and
2101 CONFIG_SPL_NAND_RAW_ONLY
2102 Support to boot only raw u-boot.bin images. Use this only
2103 if you need to save space.
2105 CONFIG_SPL_COMMON_INIT_DDR
2106 Set for common ddr init with serial presence detect in
2109 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2110 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2111 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2112 CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2113 CONFIG_SYS_NAND_ECCBYTES
2114 Defines the size and behavior of the NAND that SPL uses
2117 CONFIG_SYS_NAND_U_BOOT_OFFS
2118 Location in NAND to read U-Boot from
2120 CONFIG_SYS_NAND_U_BOOT_DST
2121 Location in memory to load U-Boot to
2123 CONFIG_SYS_NAND_U_BOOT_SIZE
2124 Size of image to load
2126 CONFIG_SYS_NAND_U_BOOT_START
2127 Entry point in loaded image to jump to
2129 CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2130 Define this if you need to first read the OOB and then the
2131 data. This is used, for example, on davinci platforms.
2133 CONFIG_SPL_RAM_DEVICE
2134 Support for running image already present in ram, in SPL binary
2137 Image offset to which the SPL should be padded before appending
2138 the SPL payload. By default, this is defined as
2139 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2140 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2141 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2144 Final target image containing SPL and payload. Some SPLs
2145 use an arch-specific makefile fragment instead, for
2146 example if more than one image needs to be produced.
2148 CONFIG_SPL_FIT_PRINT
2149 Printing information about a FIT image adds quite a bit of
2150 code to SPL. So this is normally disabled in SPL. Use this
2151 option to re-enable it. This will affect the output of the
2152 bootm command when booting a FIT image.
2156 Enable building of TPL globally.
2159 Image offset to which the TPL should be padded before appending
2160 the TPL payload. By default, this is defined as
2161 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2162 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2163 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2165 - Interrupt support (PPC):
2167 There are common interrupt_init() and timer_interrupt()
2168 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2169 for CPU specific initialization. interrupt_init_cpu()
2170 should set decrementer_count to appropriate value. If
2171 CPU resets decrementer automatically after interrupt
2172 (ppc4xx) it should set decrementer_count to zero.
2173 timer_interrupt() calls timer_interrupt_cpu() for CPU
2174 specific handling. If board has watchdog / status_led
2175 / other_activity_monitor it works automatically from
2176 general timer_interrupt().
2179 Board initialization settings:
2180 ------------------------------
2182 During Initialization u-boot calls a number of board specific functions
2183 to allow the preparation of board specific prerequisites, e.g. pin setup
2184 before drivers are initialized. To enable these callbacks the
2185 following configuration macros have to be defined. Currently this is
2186 architecture specific, so please check arch/your_architecture/lib/board.c
2187 typically in board_init_f() and board_init_r().
2189 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2190 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2191 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
2192 - CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2194 Configuration Settings:
2195 -----------------------
2197 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2198 Optionally it can be defined to support 64-bit memory commands.
2200 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2201 undefine this when you're short of memory.
2203 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2204 width of the commands listed in the 'help' command output.
2206 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
2207 prompt for user input.
2209 - CONFIG_SYS_CBSIZE: Buffer size for input from the Console
2211 - CONFIG_SYS_PBSIZE: Buffer size for Console output
2213 - CONFIG_SYS_MAXARGS: max. Number of arguments accepted for monitor commands
2215 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2216 the application (usually a Linux kernel) when it is
2219 - CONFIG_SYS_BAUDRATE_TABLE:
2220 List of legal baudrate settings for this board.
2222 - CONFIG_SYS_MEM_RESERVE_SECURE
2223 Only implemented for ARMv8 for now.
2224 If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2225 is substracted from total RAM and won't be reported to OS.
2226 This memory can be used as secure memory. A variable
2227 gd->arch.secure_ram is used to track the location. In systems
2228 the RAM base is not zero, or RAM is divided into banks,
2229 this variable needs to be recalcuated to get the address.
2231 - CONFIG_SYS_MEM_TOP_HIDE:
2232 If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2233 this specified memory area will get subtracted from the top
2234 (end) of RAM and won't get "touched" at all by U-Boot. By
2235 fixing up gd->ram_size the Linux kernel should gets passed
2236 the now "corrected" memory size and won't touch it either.
2237 This should work for arch/ppc and arch/powerpc. Only Linux
2238 board ports in arch/powerpc with bootwrapper support that
2239 recalculate the memory size from the SDRAM controller setup
2240 will have to get fixed in Linux additionally.
2242 This option can be used as a workaround for the 440EPx/GRx
2243 CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2246 WARNING: Please make sure that this value is a multiple of
2247 the Linux page size (normally 4k). If this is not the case,
2248 then the end address of the Linux memory will be located at a
2249 non page size aligned address and this could cause major
2252 - CONFIG_SYS_LOADS_BAUD_CHANGE:
2253 Enable temporary baudrate change while serial download
2255 - CONFIG_SYS_SDRAM_BASE:
2256 Physical start address of SDRAM. _Must_ be 0 here.
2258 - CONFIG_SYS_FLASH_BASE:
2259 Physical start address of Flash memory.
2261 - CONFIG_SYS_MONITOR_BASE:
2262 Physical start address of boot monitor code (set by
2263 make config files to be same as the text base address
2264 (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2265 CONFIG_SYS_FLASH_BASE when booting from flash.
2267 - CONFIG_SYS_MONITOR_LEN:
2268 Size of memory reserved for monitor code, used to
2269 determine _at_compile_time_ (!) if the environment is
2270 embedded within the U-Boot image, or in a separate
2273 - CONFIG_SYS_MALLOC_LEN:
2274 Size of DRAM reserved for malloc() use.
2276 - CONFIG_SYS_MALLOC_F_LEN
2277 Size of the malloc() pool for use before relocation. If
2278 this is defined, then a very simple malloc() implementation
2279 will become available before relocation. The address is just
2280 below the global data, and the stack is moved down to make
2283 This feature allocates regions with increasing addresses
2284 within the region. calloc() is supported, but realloc()
2285 is not available. free() is supported but does nothing.
2286 The memory will be freed (or in fact just forgotten) when
2287 U-Boot relocates itself.
2289 - CONFIG_SYS_MALLOC_SIMPLE
2290 Provides a simple and small malloc() and calloc() for those
2291 boards which do not use the full malloc in SPL (which is
2292 enabled with CONFIG_SYS_SPL_MALLOC_START).
2294 - CONFIG_SYS_NONCACHED_MEMORY:
2295 Size of non-cached memory area. This area of memory will be
2296 typically located right below the malloc() area and mapped
2297 uncached in the MMU. This is useful for drivers that would
2298 otherwise require a lot of explicit cache maintenance. For
2299 some drivers it's also impossible to properly maintain the
2300 cache. For example if the regions that need to be flushed
2301 are not a multiple of the cache-line size, *and* padding
2302 cannot be allocated between the regions to align them (i.e.
2303 if the HW requires a contiguous array of regions, and the
2304 size of each region is not cache-aligned), then a flush of
2305 one region may result in overwriting data that hardware has
2306 written to another region in the same cache-line. This can
2307 happen for example in network drivers where descriptors for
2308 buffers are typically smaller than the CPU cache-line (e.g.
2309 16 bytes vs. 32 or 64 bytes).
2311 Non-cached memory is only supported on 32-bit ARM at present.
2313 - CONFIG_SYS_BOOTM_LEN:
2314 Normally compressed uImages are limited to an
2315 uncompressed size of 8 MBytes. If this is not enough,
2316 you can define CONFIG_SYS_BOOTM_LEN in your board config file
2317 to adjust this setting to your needs.
2319 - CONFIG_SYS_BOOTMAPSZ:
2320 Maximum size of memory mapped by the startup code of
2321 the Linux kernel; all data that must be processed by
2322 the Linux kernel (bd_info, boot arguments, FDT blob if
2323 used) must be put below this limit, unless "bootm_low"
2324 environment variable is defined and non-zero. In such case
2325 all data for the Linux kernel must be between "bootm_low"
2326 and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
2327 variable "bootm_mapsize" will override the value of
2328 CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
2329 then the value in "bootm_size" will be used instead.
2331 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
2332 Enable initrd_high functionality. If defined then the
2333 initrd_high feature is enabled and the bootm ramdisk subcommand
2336 - CONFIG_SYS_BOOT_GET_CMDLINE:
2337 Enables allocating and saving kernel cmdline in space between
2338 "bootm_low" and "bootm_low" + BOOTMAPSZ.
2340 - CONFIG_SYS_BOOT_GET_KBD:
2341 Enables allocating and saving a kernel copy of the bd_info in
2342 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2344 - CONFIG_SYS_MAX_FLASH_BANKS:
2345 Max number of Flash memory banks
2347 - CONFIG_SYS_MAX_FLASH_SECT:
2348 Max number of sectors on a Flash chip
2350 - CONFIG_SYS_FLASH_ERASE_TOUT:
2351 Timeout for Flash erase operations (in ms)
2353 - CONFIG_SYS_FLASH_WRITE_TOUT:
2354 Timeout for Flash write operations (in ms)
2356 - CONFIG_SYS_FLASH_LOCK_TOUT
2357 Timeout for Flash set sector lock bit operation (in ms)
2359 - CONFIG_SYS_FLASH_UNLOCK_TOUT
2360 Timeout for Flash clear lock bits operation (in ms)
2362 - CONFIG_SYS_FLASH_PROTECTION
2363 If defined, hardware flash sectors protection is used
2364 instead of U-Boot software protection.
2366 - CONFIG_SYS_DIRECT_FLASH_TFTP:
2368 Enable TFTP transfers directly to flash memory;
2369 without this option such a download has to be
2370 performed in two steps: (1) download to RAM, and (2)
2371 copy from RAM to flash.
2373 The two-step approach is usually more reliable, since
2374 you can check if the download worked before you erase
2375 the flash, but in some situations (when system RAM is
2376 too limited to allow for a temporary copy of the
2377 downloaded image) this option may be very useful.
2379 - CONFIG_SYS_FLASH_CFI:
2380 Define if the flash driver uses extra elements in the
2381 common flash structure for storing flash geometry.
2383 - CONFIG_FLASH_CFI_DRIVER
2384 This option also enables the building of the cfi_flash driver
2385 in the drivers directory
2387 - CONFIG_FLASH_CFI_MTD
2388 This option enables the building of the cfi_mtd driver
2389 in the drivers directory. The driver exports CFI flash
2392 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2393 Use buffered writes to flash.
2395 - CONFIG_FLASH_SPANSION_S29WS_N
2396 s29ws-n MirrorBit flash has non-standard addresses for buffered
2399 - CONFIG_SYS_FLASH_QUIET_TEST
2400 If this option is defined, the common CFI flash doesn't
2401 print it's warning upon not recognized FLASH banks. This
2402 is useful, if some of the configured banks are only
2403 optionally available.
2405 - CONFIG_FLASH_SHOW_PROGRESS
2406 If defined (must be an integer), print out countdown
2407 digits and dots. Recommended value: 45 (9..1) for 80
2408 column displays, 15 (3..1) for 40 column displays.
2410 - CONFIG_FLASH_VERIFY
2411 If defined, the content of the flash (destination) is compared
2412 against the source after the write operation. An error message
2413 will be printed when the contents are not identical.
2414 Please note that this option is useless in nearly all cases,
2415 since such flash programming errors usually are detected earlier
2416 while unprotecting/erasing/programming. Please only enable
2417 this option if you really know what you are doing.
2419 - CONFIG_SYS_RX_ETH_BUFFER:
2420 Defines the number of Ethernet receive buffers. On some
2421 Ethernet controllers it is recommended to set this value
2422 to 8 or even higher (EEPRO100 or 405 EMAC), since all
2423 buffers can be full shortly after enabling the interface
2424 on high Ethernet traffic.
2425 Defaults to 4 if not defined.
2427 - CONFIG_ENV_MAX_ENTRIES
2429 Maximum number of entries in the hash table that is used
2430 internally to store the environment settings. The default
2431 setting is supposed to be generous and should work in most
2432 cases. This setting can be used to tune behaviour; see
2433 lib/hashtable.c for details.
2435 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2436 - CONFIG_ENV_FLAGS_LIST_STATIC
2437 Enable validation of the values given to environment variables when
2438 calling env set. Variables can be restricted to only decimal,
2439 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
2440 the variables can also be restricted to IP address or MAC address.
2442 The format of the list is:
2443 type_attribute = [s|d|x|b|i|m]
2444 access_attribute = [a|r|o|c]
2445 attributes = type_attribute[access_attribute]
2446 entry = variable_name[:attributes]
2449 The type attributes are:
2450 s - String (default)
2453 b - Boolean ([1yYtT|0nNfF])
2457 The access attributes are:
2463 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2464 Define this to a list (string) to define the ".flags"
2465 environment variable in the default or embedded environment.
2467 - CONFIG_ENV_FLAGS_LIST_STATIC
2468 Define this to a list (string) to define validation that
2469 should be done if an entry is not found in the ".flags"
2470 environment variable. To override a setting in the static
2471 list, simply add an entry for the same variable name to the
2474 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2475 regular expression. This allows multiple variables to define the same
2476 flags without explicitly listing them for each variable.
2478 The following definitions that deal with the placement and management
2479 of environment data (variable area); in general, we support the
2480 following configurations:
2482 - CONFIG_BUILD_ENVCRC:
2484 Builds up envcrc with the target environment so that external utils
2485 may easily extract it and embed it in final U-Boot images.
2487 BE CAREFUL! The first access to the environment happens quite early
2488 in U-Boot initialization (when we try to get the setting of for the
2489 console baudrate). You *MUST* have mapped your NVRAM area then, or
2492 Please note that even with NVRAM we still use a copy of the
2493 environment in RAM: we could work on NVRAM directly, but we want to
2494 keep settings there always unmodified except somebody uses "saveenv"
2495 to save the current settings.
2497 BE CAREFUL! For some special cases, the local device can not use
2498 "saveenv" command. For example, the local device will get the
2499 environment stored in a remote NOR flash by SRIO or PCIE link,
2500 but it can not erase, write this NOR flash by SRIO or PCIE interface.
2502 - CONFIG_NAND_ENV_DST
2504 Defines address in RAM to which the nand_spl code should copy the
2505 environment. If redundant environment is used, it will be copied to
2506 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2508 Please note that the environment is read-only until the monitor
2509 has been relocated to RAM and a RAM copy of the environment has been
2510 created; also, when using EEPROM you will have to use env_get_f()
2511 until then to read environment variables.
2513 The environment is protected by a CRC32 checksum. Before the monitor
2514 is relocated into RAM, as a result of a bad CRC you will be working
2515 with the compiled-in default environment - *silently*!!! [This is
2516 necessary, because the first environment variable we need is the
2517 "baudrate" setting for the console - if we have a bad CRC, we don't
2518 have any device yet where we could complain.]
2520 Note: once the monitor has been relocated, then it will complain if
2521 the default environment is used; a new CRC is computed as soon as you
2522 use the "saveenv" command to store a valid environment.
2524 - CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2525 Echo the inverted Ethernet link state to the fault LED.
2527 Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2528 also needs to be defined.
2530 - CONFIG_SYS_FAULT_MII_ADDR:
2531 MII address of the PHY to check for the Ethernet link state.
2533 - CONFIG_NS16550_MIN_FUNCTIONS:
2534 Define this if you desire to only have use of the NS16550_init
2535 and NS16550_putc functions for the serial driver located at
2536 drivers/serial/ns16550.c. This option is useful for saving
2537 space for already greatly restricted images, including but not
2538 limited to NAND_SPL configurations.
2540 - CONFIG_DISPLAY_BOARDINFO
2541 Display information about the board that U-Boot is running on
2542 when U-Boot starts up. The board function checkboard() is called
2545 - CONFIG_DISPLAY_BOARDINFO_LATE
2546 Similar to the previous option, but display this information
2547 later, once stdio is running and output goes to the LCD, if
2550 - CONFIG_BOARD_SIZE_LIMIT:
2551 Maximum size of the U-Boot image. When defined, the
2552 build system checks that the actual size does not
2555 Low Level (hardware related) configuration options:
2556 ---------------------------------------------------
2558 - CONFIG_SYS_CACHELINE_SIZE:
2559 Cache Line Size of the CPU.
2561 - CONFIG_SYS_CCSRBAR_DEFAULT:
2562 Default (power-on reset) physical address of CCSR on Freescale
2565 - CONFIG_SYS_CCSRBAR:
2566 Virtual address of CCSR. On a 32-bit build, this is typically
2567 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2569 - CONFIG_SYS_CCSRBAR_PHYS:
2570 Physical address of CCSR. CCSR can be relocated to a new
2571 physical address, if desired. In this case, this macro should
2572 be set to that address. Otherwise, it should be set to the
2573 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
2574 is typically relocated on 36-bit builds. It is recommended
2575 that this macro be defined via the _HIGH and _LOW macros:
2577 #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2578 * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2580 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2581 Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
2582 either 0 (32-bit build) or 0xF (36-bit build). This macro is
2583 used in assembly code, so it must not contain typecasts or
2584 integer size suffixes (e.g. "ULL").
2586 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
2587 Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
2588 used in assembly code, so it must not contain typecasts or
2589 integer size suffixes (e.g. "ULL").
2591 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2592 If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2593 forced to a value that ensures that CCSR is not relocated.
2596 Most IDE controllers were designed to be connected with PCI
2597 interface. Only few of them were designed for AHB interface.
2598 When software is doing ATA command and data transfer to
2599 IDE devices through IDE-AHB controller, some additional
2600 registers accessing to these kind of IDE-AHB controller
2603 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
2604 DO NOT CHANGE unless you know exactly what you're
2605 doing! (11-4) [MPC8xx systems only]
2607 - CONFIG_SYS_INIT_RAM_ADDR:
2609 Start address of memory area that can be used for
2610 initial data and stack; please note that this must be
2611 writable memory that is working WITHOUT special
2612 initialization, i. e. you CANNOT use normal RAM which
2613 will become available only after programming the
2614 memory controller and running certain initialization
2617 U-Boot uses the following memory types:
2618 - MPC8xx: IMMR (internal memory of the CPU)
2620 - CONFIG_SYS_GBL_DATA_OFFSET:
2622 Offset of the initial data structure in the memory
2623 area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2624 CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2625 data is located at the end of the available space
2626 (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2627 GENERATED_GBL_DATA_SIZE), and the initial stack is just
2628 below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2629 CONFIG_SYS_GBL_DATA_OFFSET) downward.
2632 On the MPC824X (or other systems that use the data
2633 cache for initial memory) the address chosen for
2634 CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2635 point to an otherwise UNUSED address space between
2636 the top of RAM and the start of the PCI space.
2638 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
2640 - CONFIG_SYS_OR_TIMING_SDRAM:
2643 - CONFIG_SYS_MAMR_PTA:
2644 periodic timer for refresh
2646 - FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2647 CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2648 CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2649 CONFIG_SYS_BR1_PRELIM:
2650 Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2652 - SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2653 CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2654 CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2655 Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2657 - CONFIG_PCI_INDIRECT_BRIDGE:
2658 Enable support for indirect PCI bridges.
2661 Chip has SRIO or not
2664 Board has SRIO 1 port available
2667 Board has SRIO 2 port available
2669 - CONFIG_SRIO_PCIE_BOOT_MASTER
2670 Board can support master function for Boot from SRIO and PCIE
2672 - CONFIG_SYS_SRIOn_MEM_VIRT:
2673 Virtual Address of SRIO port 'n' memory region
2675 - CONFIG_SYS_SRIOn_MEM_PHYxS:
2676 Physical Address of SRIO port 'n' memory region
2678 - CONFIG_SYS_SRIOn_MEM_SIZE:
2679 Size of SRIO port 'n' memory region
2681 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
2682 Defined to tell the NAND controller that the NAND chip is using
2684 Not all NAND drivers use this symbol.
2685 Example of drivers that use it:
2686 - drivers/mtd/nand/raw/ndfc.c
2687 - drivers/mtd/nand/raw/mxc_nand.c
2689 - CONFIG_SYS_NDFC_EBC0_CFG
2690 Sets the EBC0_CFG register for the NDFC. If not defined
2691 a default value will be used.
2694 Get DDR timing information from an I2C EEPROM. Common
2695 with pluggable memory modules such as SODIMMs
2698 I2C address of the SPD EEPROM
2700 - CONFIG_SYS_SPD_BUS_NUM
2701 If SPD EEPROM is on an I2C bus other than the first
2702 one, specify here. Note that the value must resolve
2703 to something your driver can deal with.
2705 - CONFIG_SYS_DDR_RAW_TIMING
2706 Get DDR timing information from other than SPD. Common with
2707 soldered DDR chips onboard without SPD. DDR raw timing
2708 parameters are extracted from datasheet and hard-coded into
2709 header files or board specific files.
2711 - CONFIG_FSL_DDR_INTERACTIVE
2712 Enable interactive DDR debugging. See doc/README.fsl-ddr.
2714 - CONFIG_FSL_DDR_SYNC_REFRESH
2715 Enable sync of refresh for multiple controllers.
2717 - CONFIG_FSL_DDR_BIST
2718 Enable built-in memory test for Freescale DDR controllers.
2720 - CONFIG_SYS_83XX_DDR_USES_CS0
2721 Only for 83xx systems. If specified, then DDR should
2722 be configured using CS0 and CS1 instead of CS2 and CS3.
2725 Enable RMII mode for all FECs.
2726 Note that this is a global option, we can't
2727 have one FEC in standard MII mode and another in RMII mode.
2729 - CONFIG_CRC32_VERIFY
2730 Add a verify option to the crc32 command.
2733 => crc32 -v <address> <count> <crc32>
2735 Where address/count indicate a memory area
2736 and crc32 is the correct crc32 which the
2740 Add the "loopw" memory command. This only takes effect if
2741 the memory commands are activated globally (CONFIG_CMD_MEMORY).
2743 - CONFIG_CMD_MX_CYCLIC
2744 Add the "mdc" and "mwc" memory commands. These are cyclic
2749 This command will print 4 bytes (10,11,12,13) each 500 ms.
2751 => mwc.l 100 12345678 10
2752 This command will write 12345678 to address 100 all 10 ms.
2754 This only takes effect if the memory commands are activated
2755 globally (CONFIG_CMD_MEMORY).
2757 - CONFIG_SKIP_LOWLEVEL_INIT
2758 [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
2759 low level initializations (like setting up the memory
2760 controller) are omitted and/or U-Boot does not
2761 relocate itself into RAM.
2763 Normally this variable MUST NOT be defined. The only
2764 exception is when U-Boot is loaded (to RAM) by some
2765 other boot loader or by a debugger which performs
2766 these initializations itself.
2768 - CONFIG_SKIP_LOWLEVEL_INIT_ONLY
2769 [ARM926EJ-S only] This allows just the call to lowlevel_init()
2770 to be skipped. The normal CP15 init (such as enabling the
2771 instruction cache) is still performed.
2774 Set when the currently-running compilation is for an artifact
2775 that will end up in the SPL (as opposed to the TPL or U-Boot
2776 proper). Code that needs stage-specific behavior should check
2780 Set when the currently-running compilation is for an artifact
2781 that will end up in the TPL (as opposed to the SPL or U-Boot
2782 proper). Code that needs stage-specific behavior should check
2785 - CONFIG_SYS_MPC85XX_NO_RESETVEC
2786 Only for 85xx systems. If this variable is specified, the section
2787 .resetvec is not kept and the section .bootpg is placed in the
2788 previous 4k of the .text section.
2790 - CONFIG_ARCH_MAP_SYSMEM
2791 Generally U-Boot (and in particular the md command) uses
2792 effective address. It is therefore not necessary to regard
2793 U-Boot address as virtual addresses that need to be translated
2794 to physical addresses. However, sandbox requires this, since
2795 it maintains its own little RAM buffer which contains all
2796 addressable memory. This option causes some memory accesses
2797 to be mapped through map_sysmem() / unmap_sysmem().
2799 - CONFIG_X86_RESET_VECTOR
2800 If defined, the x86 reset vector code is included. This is not
2801 needed when U-Boot is running from Coreboot.
2803 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
2804 Option to disable subpage write in NAND driver
2805 driver that uses this:
2806 drivers/mtd/nand/raw/davinci_nand.c
2808 Freescale QE/FMAN Firmware Support:
2809 -----------------------------------
2811 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
2812 loading of "firmware", which is encoded in the QE firmware binary format.
2813 This firmware often needs to be loaded during U-Boot booting, so macros
2814 are used to identify the storage device (NOR flash, SPI, etc) and the address
2817 - CONFIG_SYS_FMAN_FW_ADDR
2818 The address in the storage device where the FMAN microcode is located. The
2819 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2822 - CONFIG_SYS_QE_FW_ADDR
2823 The address in the storage device where the QE microcode is located. The
2824 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2827 - CONFIG_SYS_QE_FMAN_FW_LENGTH
2828 The maximum possible size of the firmware. The firmware binary format
2829 has a field that specifies the actual size of the firmware, but it
2830 might not be possible to read any part of the firmware unless some
2831 local storage is allocated to hold the entire firmware first.
2833 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
2834 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
2835 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
2836 virtual address in NOR flash.
2838 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
2839 Specifies that QE/FMAN firmware is located in NAND flash.
2840 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
2842 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
2843 Specifies that QE/FMAN firmware is located on the primary SD/MMC
2844 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
2846 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
2847 Specifies that QE/FMAN firmware is located in the remote (master)
2848 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
2849 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
2850 window->master inbound window->master LAW->the ucode address in
2851 master's memory space.
2853 Freescale Layerscape Management Complex Firmware Support:
2854 ---------------------------------------------------------
2855 The Freescale Layerscape Management Complex (MC) supports the loading of
2857 This firmware often needs to be loaded during U-Boot booting, so macros
2858 are used to identify the storage device (NOR flash, SPI, etc) and the address
2861 - CONFIG_FSL_MC_ENET
2862 Enable the MC driver for Layerscape SoCs.
2864 Freescale Layerscape Debug Server Support:
2865 -------------------------------------------
2866 The Freescale Layerscape Debug Server Support supports the loading of
2867 "Debug Server firmware" and triggering SP boot-rom.
2868 This firmware often needs to be loaded during U-Boot booting.
2870 - CONFIG_SYS_MC_RSV_MEM_ALIGN
2871 Define alignment of reserved memory MC requires
2876 In order to achieve reproducible builds, timestamps used in the U-Boot build
2877 process have to be set to a fixed value.
2879 This is done using the SOURCE_DATE_EPOCH environment variable.
2880 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
2881 option for U-Boot or an environment variable in U-Boot.
2883 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
2885 Building the Software:
2886 ======================
2888 Building U-Boot has been tested in several native build environments
2889 and in many different cross environments. Of course we cannot support
2890 all possibly existing versions of cross development tools in all
2891 (potentially obsolete) versions. In case of tool chain problems we
2892 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
2893 which is extensively used to build and test U-Boot.
2895 If you are not using a native environment, it is assumed that you
2896 have GNU cross compiling tools available in your path. In this case,
2897 you must set the environment variable CROSS_COMPILE in your shell.
2898 Note that no changes to the Makefile or any other source files are
2899 necessary. For example using the ELDK on a 4xx CPU, please enter:
2901 $ CROSS_COMPILE=ppc_4xx-
2902 $ export CROSS_COMPILE
2904 U-Boot is intended to be simple to build. After installing the
2905 sources you must configure U-Boot for one specific board type. This
2910 where "NAME_defconfig" is the name of one of the existing configu-
2911 rations; see configs/*_defconfig for supported names.
2913 Note: for some boards special configuration names may exist; check if
2914 additional information is available from the board vendor; for
2915 instance, the TQM823L systems are available without (standard)
2916 or with LCD support. You can select such additional "features"
2917 when choosing the configuration, i. e.
2919 make TQM823L_defconfig
2920 - will configure for a plain TQM823L, i. e. no LCD support
2922 make TQM823L_LCD_defconfig
2923 - will configure for a TQM823L with U-Boot console on LCD
2928 Finally, type "make all", and you should get some working U-Boot
2929 images ready for download to / installation on your system:
2931 - "u-boot.bin" is a raw binary image
2932 - "u-boot" is an image in ELF binary format
2933 - "u-boot.srec" is in Motorola S-Record format
2935 By default the build is performed locally and the objects are saved
2936 in the source directory. One of the two methods can be used to change
2937 this behavior and build U-Boot to some external directory:
2939 1. Add O= to the make command line invocations:
2941 make O=/tmp/build distclean
2942 make O=/tmp/build NAME_defconfig
2943 make O=/tmp/build all
2945 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
2947 export KBUILD_OUTPUT=/tmp/build
2952 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
2955 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
2956 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
2957 For example to treat all compiler warnings as errors:
2959 make KCFLAGS=-Werror
2961 Please be aware that the Makefiles assume you are using GNU make, so
2962 for instance on NetBSD you might need to use "gmake" instead of
2966 If the system board that you have is not listed, then you will need
2967 to port U-Boot to your hardware platform. To do this, follow these
2970 1. Create a new directory to hold your board specific code. Add any
2971 files you need. In your board directory, you will need at least
2972 the "Makefile" and a "<board>.c".
2973 2. Create a new configuration file "include/configs/<board>.h" for
2975 3. If you're porting U-Boot to a new CPU, then also create a new
2976 directory to hold your CPU specific code. Add any files you need.
2977 4. Run "make <board>_defconfig" with your new name.
2978 5. Type "make", and you should get a working "u-boot.srec" file
2979 to be installed on your target system.
2980 6. Debug and solve any problems that might arise.
2981 [Of course, this last step is much harder than it sounds.]
2984 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
2985 ==============================================================
2987 If you have modified U-Boot sources (for instance added a new board
2988 or support for new devices, a new CPU, etc.) you are expected to
2989 provide feedback to the other developers. The feedback normally takes
2990 the form of a "patch", i.e. a context diff against a certain (latest
2991 official or latest in the git repository) version of U-Boot sources.
2993 But before you submit such a patch, please verify that your modifi-
2994 cation did not break existing code. At least make sure that *ALL* of
2995 the supported boards compile WITHOUT ANY compiler warnings. To do so,
2996 just run the buildman script (tools/buildman/buildman), which will
2997 configure and build U-Boot for ALL supported system. Be warned, this
2998 will take a while. Please see the buildman README, or run 'buildman -H'
3002 See also "U-Boot Porting Guide" below.
3005 Monitor Commands - Overview:
3006 ============================
3008 go - start application at address 'addr'
3009 run - run commands in an environment variable
3010 bootm - boot application image from memory
3011 bootp - boot image via network using BootP/TFTP protocol
3012 bootz - boot zImage from memory
3013 tftpboot- boot image via network using TFTP protocol
3014 and env variables "ipaddr" and "serverip"
3015 (and eventually "gatewayip")
3016 tftpput - upload a file via network using TFTP protocol
3017 rarpboot- boot image via network using RARP/TFTP protocol
3018 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
3019 loads - load S-Record file over serial line
3020 loadb - load binary file over serial line (kermit mode)
3022 mm - memory modify (auto-incrementing)
3023 nm - memory modify (constant address)
3024 mw - memory write (fill)
3027 cmp - memory compare
3028 crc32 - checksum calculation
3029 i2c - I2C sub-system
3030 sspi - SPI utility commands
3031 base - print or set address offset
3032 printenv- print environment variables
3033 pwm - control pwm channels
3034 setenv - set environment variables
3035 saveenv - save environment variables to persistent storage
3036 protect - enable or disable FLASH write protection
3037 erase - erase FLASH memory
3038 flinfo - print FLASH memory information
3039 nand - NAND memory operations (see doc/README.nand)
3040 bdinfo - print Board Info structure
3041 iminfo - print header information for application image
3042 coninfo - print console devices and informations
3043 ide - IDE sub-system
3044 loop - infinite loop on address range
3045 loopw - infinite write loop on address range
3046 mtest - simple RAM test
3047 icache - enable or disable instruction cache
3048 dcache - enable or disable data cache
3049 reset - Perform RESET of the CPU
3050 echo - echo args to console
3051 version - print monitor version
3052 help - print online help
3053 ? - alias for 'help'
3056 Monitor Commands - Detailed Description:
3057 ========================================
3061 For now: just type "help <command>".
3064 Environment Variables:
3065 ======================
3067 U-Boot supports user configuration using Environment Variables which
3068 can be made persistent by saving to Flash memory.
3070 Environment Variables are set using "setenv", printed using
3071 "printenv", and saved to Flash using "saveenv". Using "setenv"
3072 without a value can be used to delete a variable from the
3073 environment. As long as you don't save the environment you are
3074 working with an in-memory copy. In case the Flash area containing the
3075 environment is erased by accident, a default environment is provided.
3077 Some configuration options can be set using Environment Variables.
3079 List of environment variables (most likely not complete):
3081 baudrate - see CONFIG_BAUDRATE
3083 bootdelay - see CONFIG_BOOTDELAY
3085 bootcmd - see CONFIG_BOOTCOMMAND
3087 bootargs - Boot arguments when booting an RTOS image
3089 bootfile - Name of the image to load with TFTP
3091 bootm_low - Memory range available for image processing in the bootm
3092 command can be restricted. This variable is given as
3093 a hexadecimal number and defines lowest address allowed
3094 for use by the bootm command. See also "bootm_size"
3095 environment variable. Address defined by "bootm_low" is
3096 also the base of the initial memory mapping for the Linux
3097 kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3100 bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3101 This variable is given as a hexadecimal number and it
3102 defines the size of the memory region starting at base
3103 address bootm_low that is accessible by the Linux kernel
3104 during early boot. If unset, CONFIG_SYS_BOOTMAPSZ is used
3105 as the default value if it is defined, and bootm_size is
3108 bootm_size - Memory range available for image processing in the bootm
3109 command can be restricted. This variable is given as
3110 a hexadecimal number and defines the size of the region
3111 allowed for use by the bootm command. See also "bootm_low"
3112 environment variable.
3114 bootstopkeysha256, bootdelaykey, bootstopkey - See README.autoboot
3116 updatefile - Location of the software update file on a TFTP server, used
3117 by the automatic software update feature. Please refer to
3118 documentation in doc/README.update for more details.
3120 autoload - if set to "no" (any string beginning with 'n'),
3121 "bootp" will just load perform a lookup of the
3122 configuration from the BOOTP server, but not try to
3123 load any image using TFTP
3125 autostart - if set to "yes", an image loaded using the "bootp",
3126 "rarpboot", "tftpboot" or "diskboot" commands will
3127 be automatically started (by internally calling
3130 If set to "no", a standalone image passed to the
3131 "bootm" command will be copied to the load address
3132 (and eventually uncompressed), but NOT be started.
3133 This can be used to load and uncompress arbitrary
3136 fdt_high - if set this restricts the maximum address that the
3137 flattened device tree will be copied into upon boot.
3138 For example, if you have a system with 1 GB memory
3139 at physical address 0x10000000, while Linux kernel
3140 only recognizes the first 704 MB as low memory, you
3141 may need to set fdt_high as 0x3C000000 to have the
3142 device tree blob be copied to the maximum address
3143 of the 704 MB low memory, so that Linux kernel can
3144 access it during the boot procedure.
3146 If this is set to the special value 0xFFFFFFFF then
3147 the fdt will not be copied at all on boot. For this
3148 to work it must reside in writable memory, have
3149 sufficient padding on the end of it for u-boot to
3150 add the information it needs into it, and the memory
3151 must be accessible by the kernel.
3153 fdtcontroladdr- if set this is the address of the control flattened
3154 device tree used by U-Boot when CONFIG_OF_CONTROL is
3157 i2cfast - (PPC405GP|PPC405EP only)
3158 if set to 'y' configures Linux I2C driver for fast
3159 mode (400kHZ). This environment variable is used in
3160 initialization code. So, for changes to be effective
3161 it must be saved and board must be reset.
3163 initrd_high - restrict positioning of initrd images:
3164 If this variable is not set, initrd images will be
3165 copied to the highest possible address in RAM; this
3166 is usually what you want since it allows for
3167 maximum initrd size. If for some reason you want to
3168 make sure that the initrd image is loaded below the
3169 CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3170 variable to a value of "no" or "off" or "0".
3171 Alternatively, you can set it to a maximum upper
3172 address to use (U-Boot will still check that it
3173 does not overwrite the U-Boot stack and data).
3175 For instance, when you have a system with 16 MB
3176 RAM, and want to reserve 4 MB from use by Linux,
3177 you can do this by adding "mem=12M" to the value of
3178 the "bootargs" variable. However, now you must make
3179 sure that the initrd image is placed in the first
3180 12 MB as well - this can be done with
3182 setenv initrd_high 00c00000
3184 If you set initrd_high to 0xFFFFFFFF, this is an
3185 indication to U-Boot that all addresses are legal
3186 for the Linux kernel, including addresses in flash
3187 memory. In this case U-Boot will NOT COPY the
3188 ramdisk at all. This may be useful to reduce the
3189 boot time on your system, but requires that this
3190 feature is supported by your Linux kernel.
3192 ipaddr - IP address; needed for tftpboot command
3194 loadaddr - Default load address for commands like "bootp",
3195 "rarpboot", "tftpboot", "loadb" or "diskboot"
3197 loads_echo - see CONFIG_LOADS_ECHO
3199 serverip - TFTP server IP address; needed for tftpboot command
3201 bootretry - see CONFIG_BOOT_RETRY_TIME
3203 bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR
3205 bootstopkey - see CONFIG_AUTOBOOT_STOP_STR
3207 ethprime - controls which interface is used first.
3209 ethact - controls which interface is currently active.
3210 For example you can do the following
3212 => setenv ethact FEC
3213 => ping 192.168.0.1 # traffic sent on FEC
3214 => setenv ethact SCC
3215 => ping 10.0.0.1 # traffic sent on SCC
3217 ethrotate - When set to "no" U-Boot does not go through all
3218 available network interfaces.
3219 It just stays at the currently selected interface.
3221 netretry - When set to "no" each network operation will
3222 either succeed or fail without retrying.
3223 When set to "once" the network operation will
3224 fail when all the available network interfaces
3225 are tried once without success.
3226 Useful on scripts which control the retry operation
3229 npe_ucode - set load address for the NPE microcode
3231 silent_linux - If set then Linux will be told to boot silently, by
3232 changing the console to be empty. If "yes" it will be
3233 made silent. If "no" it will not be made silent. If
3234 unset, then it will be made silent if the U-Boot console
3237 tftpsrcp - If this is set, the value is used for TFTP's
3240 tftpdstp - If this is set, the value is used for TFTP's UDP
3241 destination port instead of the Well Know Port 69.
3243 tftpblocksize - Block size to use for TFTP transfers; if not set,
3244 we use the TFTP server's default block size
3246 tftptimeout - Retransmission timeout for TFTP packets (in milli-
3247 seconds, minimum value is 1000 = 1 second). Defines
3248 when a packet is considered to be lost so it has to
3249 be retransmitted. The default is 5000 = 5 seconds.
3250 Lowering this value may make downloads succeed
3251 faster in networks with high packet loss rates or
3252 with unreliable TFTP servers.
3254 tftptimeoutcountmax - maximum count of TFTP timeouts (no
3255 unit, minimum value = 0). Defines how many timeouts
3256 can happen during a single file transfer before that
3257 transfer is aborted. The default is 10, and 0 means
3258 'no timeouts allowed'. Increasing this value may help
3259 downloads succeed with high packet loss rates, or with
3260 unreliable TFTP servers or client hardware.
3262 tftpwindowsize - if this is set, the value is used for TFTP's
3263 window size as described by RFC 7440.
3264 This means the count of blocks we can receive before
3265 sending ack to server.
3267 vlan - When set to a value < 4095 the traffic over
3268 Ethernet is encapsulated/received over 802.1q
3271 bootpretryperiod - Period during which BOOTP/DHCP sends retries.
3272 Unsigned value, in milliseconds. If not set, the period will
3273 be either the default (28000), or a value based on
3274 CONFIG_NET_RETRY_COUNT, if defined. This value has
3275 precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3277 memmatches - Number of matches found by the last 'ms' command, in hex
3279 memaddr - Address of the last match found by the 'ms' command, in hex,
3282 mempos - Index position of the last match found by the 'ms' command,
3283 in units of the size (.b, .w, .l) of the search
3285 zbootbase - (x86 only) Base address of the bzImage 'setup' block
3287 zbootaddr - (x86 only) Address of the loaded bzImage, typically
3288 BZIMAGE_LOAD_ADDR which is 0x100000
3290 The following image location variables contain the location of images
3291 used in booting. The "Image" column gives the role of the image and is
3292 not an environment variable name. The other columns are environment
3293 variable names. "File Name" gives the name of the file on a TFTP
3294 server, "RAM Address" gives the location in RAM the image will be
3295 loaded to, and "Flash Location" gives the image's address in NOR
3296 flash or offset in NAND flash.
3298 *Note* - these variables don't have to be defined for all boards, some
3299 boards currently use other variables for these purposes, and some
3300 boards use these variables for other purposes.
3302 Image File Name RAM Address Flash Location
3303 ----- --------- ----------- --------------
3304 u-boot u-boot u-boot_addr_r u-boot_addr
3305 Linux kernel bootfile kernel_addr_r kernel_addr
3306 device tree blob fdtfile fdt_addr_r fdt_addr
3307 ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr
3309 The following environment variables may be used and automatically
3310 updated by the network boot commands ("bootp" and "rarpboot"),
3311 depending the information provided by your boot server:
3313 bootfile - see above
3314 dnsip - IP address of your Domain Name Server
3315 dnsip2 - IP address of your secondary Domain Name Server
3316 gatewayip - IP address of the Gateway (Router) to use
3317 hostname - Target hostname
3319 netmask - Subnet Mask
3320 rootpath - Pathname of the root filesystem on the NFS server
3321 serverip - see above
3324 There are two special Environment Variables:
3326 serial# - contains hardware identification information such
3327 as type string and/or serial number
3328 ethaddr - Ethernet address
3330 These variables can be set only once (usually during manufacturing of
3331 the board). U-Boot refuses to delete or overwrite these variables
3332 once they have been set once.
3335 Further special Environment Variables:
3337 ver - Contains the U-Boot version string as printed
3338 with the "version" command. This variable is
3339 readonly (see CONFIG_VERSION_VARIABLE).
3342 Please note that changes to some configuration parameters may take
3343 only effect after the next boot (yes, that's just like Windoze :-).
3346 Callback functions for environment variables:
3347 ---------------------------------------------
3349 For some environment variables, the behavior of u-boot needs to change
3350 when their values are changed. This functionality allows functions to
3351 be associated with arbitrary variables. On creation, overwrite, or
3352 deletion, the callback will provide the opportunity for some side
3353 effect to happen or for the change to be rejected.
3355 The callbacks are named and associated with a function using the
3356 U_BOOT_ENV_CALLBACK macro in your board or driver code.
3358 These callbacks are associated with variables in one of two ways. The
3359 static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3360 in the board configuration to a string that defines a list of
3361 associations. The list must be in the following format:
3363 entry = variable_name[:callback_name]
3366 If the callback name is not specified, then the callback is deleted.
3367 Spaces are also allowed anywhere in the list.
3369 Callbacks can also be associated by defining the ".callbacks" variable
3370 with the same list format above. Any association in ".callbacks" will
3371 override any association in the static list. You can define
3372 CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3373 ".callbacks" environment variable in the default or embedded environment.
3375 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3376 regular expression. This allows multiple variables to be connected to
3377 the same callback without explicitly listing them all out.
3379 The signature of the callback functions is:
3381 int callback(const char *name, const char *value, enum env_op op, int flags)
3383 * name - changed environment variable
3384 * value - new value of the environment variable
3385 * op - operation (create, overwrite, or delete)
3386 * flags - attributes of the environment variable change, see flags H_* in
3389 The return value is 0 if the variable change is accepted and 1 otherwise.
3392 Note for Redundant Ethernet Interfaces:
3393 =======================================
3395 Some boards come with redundant Ethernet interfaces; U-Boot supports
3396 such configurations and is capable of automatic selection of a
3397 "working" interface when needed. MAC assignment works as follows:
3399 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3400 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3401 "eth1addr" (=>eth1), "eth2addr", ...
3403 If the network interface stores some valid MAC address (for instance
3404 in SROM), this is used as default address if there is NO correspon-
3405 ding setting in the environment; if the corresponding environment
3406 variable is set, this overrides the settings in the card; that means:
3408 o If the SROM has a valid MAC address, and there is no address in the
3409 environment, the SROM's address is used.
3411 o If there is no valid address in the SROM, and a definition in the
3412 environment exists, then the value from the environment variable is
3415 o If both the SROM and the environment contain a MAC address, and
3416 both addresses are the same, this MAC address is used.
3418 o If both the SROM and the environment contain a MAC address, and the
3419 addresses differ, the value from the environment is used and a
3422 o If neither SROM nor the environment contain a MAC address, an error
3423 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3424 a random, locally-assigned MAC is used.
3426 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3427 will be programmed into hardware as part of the initialization process. This
3428 may be skipped by setting the appropriate 'ethmacskip' environment variable.
3429 The naming convention is as follows:
3430 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3435 U-Boot is capable of booting (and performing other auxiliary operations on)
3436 images in two formats:
3438 New uImage format (FIT)
3439 -----------------------
3441 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3442 to Flattened Device Tree). It allows the use of images with multiple
3443 components (several kernels, ramdisks, etc.), with contents protected by
3444 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3450 Old image format is based on binary files which can be basically anything,
3451 preceded by a special header; see the definitions in include/image.h for
3452 details; basically, the header defines the following image properties:
3454 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3455 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3456 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3457 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3459 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3460 IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3461 Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3462 * Compression Type (uncompressed, gzip, bzip2)
3468 The header is marked by a special Magic Number, and both the header
3469 and the data portions of the image are secured against corruption by
3476 Although U-Boot should support any OS or standalone application
3477 easily, the main focus has always been on Linux during the design of
3480 U-Boot includes many features that so far have been part of some
3481 special "boot loader" code within the Linux kernel. Also, any
3482 "initrd" images to be used are no longer part of one big Linux image;
3483 instead, kernel and "initrd" are separate images. This implementation
3484 serves several purposes:
3486 - the same features can be used for other OS or standalone
3487 applications (for instance: using compressed images to reduce the
3488 Flash memory footprint)
3490 - it becomes much easier to port new Linux kernel versions because
3491 lots of low-level, hardware dependent stuff are done by U-Boot
3493 - the same Linux kernel image can now be used with different "initrd"
3494 images; of course this also means that different kernel images can
3495 be run with the same "initrd". This makes testing easier (you don't
3496 have to build a new "zImage.initrd" Linux image when you just
3497 change a file in your "initrd"). Also, a field-upgrade of the
3498 software is easier now.
3504 Porting Linux to U-Boot based systems:
3505 ---------------------------------------
3507 U-Boot cannot save you from doing all the necessary modifications to
3508 configure the Linux device drivers for use with your target hardware
3509 (no, we don't intend to provide a full virtual machine interface to
3512 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3514 Just make sure your machine specific header file (for instance
3515 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3516 Information structure as we define in include/asm-<arch>/u-boot.h,
3517 and make sure that your definition of IMAP_ADDR uses the same value
3518 as your U-Boot configuration in CONFIG_SYS_IMMR.
3520 Note that U-Boot now has a driver model, a unified model for drivers.
3521 If you are adding a new driver, plumb it into driver model. If there
3522 is no uclass available, you are encouraged to create one. See
3526 Configuring the Linux kernel:
3527 -----------------------------
3529 No specific requirements for U-Boot. Make sure you have some root
3530 device (initial ramdisk, NFS) for your target system.
3533 Building a Linux Image:
3534 -----------------------
3536 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3537 not used. If you use recent kernel source, a new build target
3538 "uImage" will exist which automatically builds an image usable by
3539 U-Boot. Most older kernels also have support for a "pImage" target,
3540 which was introduced for our predecessor project PPCBoot and uses a
3541 100% compatible format.
3545 make TQM850L_defconfig
3550 The "uImage" build target uses a special tool (in 'tools/mkimage') to
3551 encapsulate a compressed Linux kernel image with header information,
3552 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3554 * build a standard "vmlinux" kernel image (in ELF binary format):
3556 * convert the kernel into a raw binary image:
3558 ${CROSS_COMPILE}-objcopy -O binary \
3559 -R .note -R .comment \
3560 -S vmlinux linux.bin
3562 * compress the binary image:
3566 * package compressed binary image for U-Boot:
3568 mkimage -A ppc -O linux -T kernel -C gzip \
3569 -a 0 -e 0 -n "Linux Kernel Image" \
3570 -d linux.bin.gz uImage
3573 The "mkimage" tool can also be used to create ramdisk images for use
3574 with U-Boot, either separated from the Linux kernel image, or
3575 combined into one file. "mkimage" encapsulates the images with a 64
3576 byte header containing information about target architecture,
3577 operating system, image type, compression method, entry points, time
3578 stamp, CRC32 checksums, etc.
3580 "mkimage" can be called in two ways: to verify existing images and
3581 print the header information, or to build new images.
3583 In the first form (with "-l" option) mkimage lists the information
3584 contained in the header of an existing U-Boot image; this includes
3585 checksum verification:
3587 tools/mkimage -l image
3588 -l ==> list image header information
3590 The second form (with "-d" option) is used to build a U-Boot image
3591 from a "data file" which is used as image payload:
3593 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3594 -n name -d data_file image
3595 -A ==> set architecture to 'arch'
3596 -O ==> set operating system to 'os'
3597 -T ==> set image type to 'type'
3598 -C ==> set compression type 'comp'
3599 -a ==> set load address to 'addr' (hex)
3600 -e ==> set entry point to 'ep' (hex)
3601 -n ==> set image name to 'name'
3602 -d ==> use image data from 'datafile'
3604 Right now, all Linux kernels for PowerPC systems use the same load
3605 address (0x00000000), but the entry point address depends on the
3608 - 2.2.x kernels have the entry point at 0x0000000C,
3609 - 2.3.x and later kernels have the entry point at 0x00000000.
3611 So a typical call to build a U-Boot image would read:
3613 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3614 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3615 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3616 > examples/uImage.TQM850L
3617 Image Name: 2.4.4 kernel for TQM850L
3618 Created: Wed Jul 19 02:34:59 2000
3619 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3620 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3621 Load Address: 0x00000000
3622 Entry Point: 0x00000000
3624 To verify the contents of the image (or check for corruption):
3626 -> tools/mkimage -l examples/uImage.TQM850L
3627 Image Name: 2.4.4 kernel for TQM850L
3628 Created: Wed Jul 19 02:34:59 2000
3629 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3630 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3631 Load Address: 0x00000000
3632 Entry Point: 0x00000000
3634 NOTE: for embedded systems where boot time is critical you can trade
3635 speed for memory and install an UNCOMPRESSED image instead: this
3636 needs more space in Flash, but boots much faster since it does not
3637 need to be uncompressed:
3639 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3640 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3641 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3642 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3643 > examples/uImage.TQM850L-uncompressed
3644 Image Name: 2.4.4 kernel for TQM850L
3645 Created: Wed Jul 19 02:34:59 2000
3646 Image Type: PowerPC Linux Kernel Image (uncompressed)
3647 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
3648 Load Address: 0x00000000
3649 Entry Point: 0x00000000
3652 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3653 when your kernel is intended to use an initial ramdisk:
3655 -> tools/mkimage -n 'Simple Ramdisk Image' \
3656 > -A ppc -O linux -T ramdisk -C gzip \
3657 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3658 Image Name: Simple Ramdisk Image
3659 Created: Wed Jan 12 14:01:50 2000
3660 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3661 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
3662 Load Address: 0x00000000
3663 Entry Point: 0x00000000
3665 The "dumpimage" tool can be used to disassemble or list the contents of images
3666 built by mkimage. See dumpimage's help output (-h) for details.
3668 Installing a Linux Image:
3669 -------------------------
3671 To downloading a U-Boot image over the serial (console) interface,
3672 you must convert the image to S-Record format:
3674 objcopy -I binary -O srec examples/image examples/image.srec
3676 The 'objcopy' does not understand the information in the U-Boot
3677 image header, so the resulting S-Record file will be relative to
3678 address 0x00000000. To load it to a given address, you need to
3679 specify the target address as 'offset' parameter with the 'loads'
3682 Example: install the image to address 0x40100000 (which on the
3683 TQM8xxL is in the first Flash bank):
3685 => erase 40100000 401FFFFF
3691 ## Ready for S-Record download ...
3692 ~>examples/image.srec
3693 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3695 15989 15990 15991 15992
3696 [file transfer complete]
3698 ## Start Addr = 0x00000000
3701 You can check the success of the download using the 'iminfo' command;
3702 this includes a checksum verification so you can be sure no data
3703 corruption happened:
3707 ## Checking Image at 40100000 ...
3708 Image Name: 2.2.13 for initrd on TQM850L
3709 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3710 Data Size: 335725 Bytes = 327 kB = 0 MB
3711 Load Address: 00000000
3712 Entry Point: 0000000c
3713 Verifying Checksum ... OK
3719 The "bootm" command is used to boot an application that is stored in
3720 memory (RAM or Flash). In case of a Linux kernel image, the contents
3721 of the "bootargs" environment variable is passed to the kernel as
3722 parameters. You can check and modify this variable using the
3723 "printenv" and "setenv" commands:
3726 => printenv bootargs
3727 bootargs=root=/dev/ram
3729 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3731 => printenv bootargs
3732 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3735 ## Booting Linux kernel at 40020000 ...
3736 Image Name: 2.2.13 for NFS on TQM850L
3737 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3738 Data Size: 381681 Bytes = 372 kB = 0 MB
3739 Load Address: 00000000
3740 Entry Point: 0000000c
3741 Verifying Checksum ... OK
3742 Uncompressing Kernel Image ... OK
3743 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
3744 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3745 time_init: decrementer frequency = 187500000/60
3746 Calibrating delay loop... 49.77 BogoMIPS
3747 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3750 If you want to boot a Linux kernel with initial RAM disk, you pass
3751 the memory addresses of both the kernel and the initrd image (PPBCOOT
3752 format!) to the "bootm" command:
3754 => imi 40100000 40200000
3756 ## Checking Image at 40100000 ...
3757 Image Name: 2.2.13 for initrd on TQM850L
3758 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3759 Data Size: 335725 Bytes = 327 kB = 0 MB
3760 Load Address: 00000000
3761 Entry Point: 0000000c
3762 Verifying Checksum ... OK
3764 ## Checking Image at 40200000 ...
3765 Image Name: Simple Ramdisk Image
3766 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3767 Data Size: 566530 Bytes = 553 kB = 0 MB
3768 Load Address: 00000000
3769 Entry Point: 00000000
3770 Verifying Checksum ... OK
3772 => bootm 40100000 40200000
3773 ## Booting Linux kernel at 40100000 ...
3774 Image Name: 2.2.13 for initrd on TQM850L
3775 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3776 Data Size: 335725 Bytes = 327 kB = 0 MB
3777 Load Address: 00000000
3778 Entry Point: 0000000c
3779 Verifying Checksum ... OK
3780 Uncompressing Kernel Image ... OK
3781 ## Loading RAMDisk Image at 40200000 ...
3782 Image Name: Simple Ramdisk Image
3783 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3784 Data Size: 566530 Bytes = 553 kB = 0 MB
3785 Load Address: 00000000
3786 Entry Point: 00000000
3787 Verifying Checksum ... OK
3788 Loading Ramdisk ... OK
3789 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
3790 Boot arguments: root=/dev/ram
3791 time_init: decrementer frequency = 187500000/60
3792 Calibrating delay loop... 49.77 BogoMIPS
3794 RAMDISK: Compressed image found at block 0
3795 VFS: Mounted root (ext2 filesystem).
3799 Boot Linux and pass a flat device tree:
3802 First, U-Boot must be compiled with the appropriate defines. See the section
3803 titled "Linux Kernel Interface" above for a more in depth explanation. The
3804 following is an example of how to start a kernel and pass an updated
3810 oft=oftrees/mpc8540ads.dtb
3811 => tftp $oftaddr $oft
3812 Speed: 1000, full duplex
3814 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
3815 Filename 'oftrees/mpc8540ads.dtb'.
3816 Load address: 0x300000
3819 Bytes transferred = 4106 (100a hex)
3820 => tftp $loadaddr $bootfile
3821 Speed: 1000, full duplex
3823 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
3825 Load address: 0x200000
3826 Loading:############
3828 Bytes transferred = 1029407 (fb51f hex)
3833 => bootm $loadaddr - $oftaddr
3834 ## Booting image at 00200000 ...
3835 Image Name: Linux-2.6.17-dirty
3836 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3837 Data Size: 1029343 Bytes = 1005.2 kB
3838 Load Address: 00000000
3839 Entry Point: 00000000
3840 Verifying Checksum ... OK
3841 Uncompressing Kernel Image ... OK
3842 Booting using flat device tree at 0x300000
3843 Using MPC85xx ADS machine description
3844 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
3848 More About U-Boot Image Types:
3849 ------------------------------
3851 U-Boot supports the following image types:
3853 "Standalone Programs" are directly runnable in the environment
3854 provided by U-Boot; it is expected that (if they behave
3855 well) you can continue to work in U-Boot after return from
3856 the Standalone Program.
3857 "OS Kernel Images" are usually images of some Embedded OS which
3858 will take over control completely. Usually these programs
3859 will install their own set of exception handlers, device
3860 drivers, set up the MMU, etc. - this means, that you cannot
3861 expect to re-enter U-Boot except by resetting the CPU.
3862 "RAMDisk Images" are more or less just data blocks, and their
3863 parameters (address, size) are passed to an OS kernel that is
3865 "Multi-File Images" contain several images, typically an OS
3866 (Linux) kernel image and one or more data images like
3867 RAMDisks. This construct is useful for instance when you want
3868 to boot over the network using BOOTP etc., where the boot
3869 server provides just a single image file, but you want to get
3870 for instance an OS kernel and a RAMDisk image.
3872 "Multi-File Images" start with a list of image sizes, each
3873 image size (in bytes) specified by an "uint32_t" in network
3874 byte order. This list is terminated by an "(uint32_t)0".
3875 Immediately after the terminating 0 follow the images, one by
3876 one, all aligned on "uint32_t" boundaries (size rounded up to
3877 a multiple of 4 bytes).
3879 "Firmware Images" are binary images containing firmware (like
3880 U-Boot or FPGA images) which usually will be programmed to
3883 "Script files" are command sequences that will be executed by
3884 U-Boot's command interpreter; this feature is especially
3885 useful when you configure U-Boot to use a real shell (hush)
3886 as command interpreter.
3888 Booting the Linux zImage:
3889 -------------------------
3891 On some platforms, it's possible to boot Linux zImage. This is done
3892 using the "bootz" command. The syntax of "bootz" command is the same
3893 as the syntax of "bootm" command.
3895 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
3896 kernel with raw initrd images. The syntax is slightly different, the
3897 address of the initrd must be augmented by it's size, in the following
3898 format: "<initrd addres>:<initrd size>".
3904 One of the features of U-Boot is that you can dynamically load and
3905 run "standalone" applications, which can use some resources of
3906 U-Boot like console I/O functions or interrupt services.
3908 Two simple examples are included with the sources:
3913 'examples/hello_world.c' contains a small "Hello World" Demo
3914 application; it is automatically compiled when you build U-Boot.
3915 It's configured to run at address 0x00040004, so you can play with it
3919 ## Ready for S-Record download ...
3920 ~>examples/hello_world.srec
3921 1 2 3 4 5 6 7 8 9 10 11 ...
3922 [file transfer complete]
3924 ## Start Addr = 0x00040004
3926 => go 40004 Hello World! This is a test.
3927 ## Starting application at 0x00040004 ...
3938 Hit any key to exit ...
3940 ## Application terminated, rc = 0x0
3942 Another example, which demonstrates how to register a CPM interrupt
3943 handler with the U-Boot code, can be found in 'examples/timer.c'.
3944 Here, a CPM timer is set up to generate an interrupt every second.
3945 The interrupt service routine is trivial, just printing a '.'
3946 character, but this is just a demo program. The application can be
3947 controlled by the following keys:
3949 ? - print current values og the CPM Timer registers
3950 b - enable interrupts and start timer
3951 e - stop timer and disable interrupts
3952 q - quit application
3955 ## Ready for S-Record download ...
3956 ~>examples/timer.srec
3957 1 2 3 4 5 6 7 8 9 10 11 ...
3958 [file transfer complete]
3960 ## Start Addr = 0x00040004
3963 ## Starting application at 0x00040004 ...
3966 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
3969 [q, b, e, ?] Set interval 1000000 us
3972 [q, b, e, ?] ........
3973 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
3976 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
3979 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
3982 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
3984 [q, b, e, ?] ...Stopping timer
3986 [q, b, e, ?] ## Application terminated, rc = 0x0
3992 Over time, many people have reported problems when trying to use the
3993 "minicom" terminal emulation program for serial download. I (wd)
3994 consider minicom to be broken, and recommend not to use it. Under
3995 Unix, I recommend to use C-Kermit for general purpose use (and
3996 especially for kermit binary protocol download ("loadb" command), and
3997 use "cu" for S-Record download ("loads" command). See
3998 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
3999 for help with kermit.
4002 Nevertheless, if you absolutely want to use it try adding this
4003 configuration to your "File transfer protocols" section:
4005 Name Program Name U/D FullScr IO-Red. Multi
4006 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
4007 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
4013 Starting at version 0.9.2, U-Boot supports NetBSD both as host
4014 (build U-Boot) and target system (boots NetBSD/mpc8xx).
4016 Building requires a cross environment; it is known to work on
4017 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4018 need gmake since the Makefiles are not compatible with BSD make).
4019 Note that the cross-powerpc package does not install include files;
4020 attempting to build U-Boot will fail because <machine/ansi.h> is
4021 missing. This file has to be installed and patched manually:
4023 # cd /usr/pkg/cross/powerpc-netbsd/include
4025 # ln -s powerpc machine
4026 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4027 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
4029 Native builds *don't* work due to incompatibilities between native
4030 and U-Boot include files.
4032 Booting assumes that (the first part of) the image booted is a
4033 stage-2 loader which in turn loads and then invokes the kernel
4034 proper. Loader sources will eventually appear in the NetBSD source
4035 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4036 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4039 Implementation Internals:
4040 =========================
4042 The following is not intended to be a complete description of every
4043 implementation detail. However, it should help to understand the
4044 inner workings of U-Boot and make it easier to port it to custom
4048 Initial Stack, Global Data:
4049 ---------------------------
4051 The implementation of U-Boot is complicated by the fact that U-Boot
4052 starts running out of ROM (flash memory), usually without access to
4053 system RAM (because the memory controller is not initialized yet).
4054 This means that we don't have writable Data or BSS segments, and BSS
4055 is not initialized as zero. To be able to get a C environment working
4056 at all, we have to allocate at least a minimal stack. Implementation
4057 options for this are defined and restricted by the CPU used: Some CPU
4058 models provide on-chip memory (like the IMMR area on MPC8xx and
4059 MPC826x processors), on others (parts of) the data cache can be
4060 locked as (mis-) used as memory, etc.
4062 Chris Hallinan posted a good summary of these issues to the
4063 U-Boot mailing list:
4065 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4066 From: "Chris Hallinan" <clh@net1plus.com>
4067 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4070 Correct me if I'm wrong, folks, but the way I understand it
4071 is this: Using DCACHE as initial RAM for Stack, etc, does not
4072 require any physical RAM backing up the cache. The cleverness
4073 is that the cache is being used as a temporary supply of
4074 necessary storage before the SDRAM controller is setup. It's
4075 beyond the scope of this list to explain the details, but you
4076 can see how this works by studying the cache architecture and
4077 operation in the architecture and processor-specific manuals.
4079 OCM is On Chip Memory, which I believe the 405GP has 4K. It
4080 is another option for the system designer to use as an
4081 initial stack/RAM area prior to SDRAM being available. Either
4082 option should work for you. Using CS 4 should be fine if your
4083 board designers haven't used it for something that would
4084 cause you grief during the initial boot! It is frequently not
4087 CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4088 with your processor/board/system design. The default value
4089 you will find in any recent u-boot distribution in
4090 walnut.h should work for you. I'd set it to a value larger
4091 than your SDRAM module. If you have a 64MB SDRAM module, set
4092 it above 400_0000. Just make sure your board has no resources
4093 that are supposed to respond to that address! That code in
4094 start.S has been around a while and should work as is when
4095 you get the config right.
4100 It is essential to remember this, since it has some impact on the C
4101 code for the initialization procedures:
4103 * Initialized global data (data segment) is read-only. Do not attempt
4106 * Do not use any uninitialized global data (or implicitly initialized
4107 as zero data - BSS segment) at all - this is undefined, initiali-
4108 zation is performed later (when relocating to RAM).
4110 * Stack space is very limited. Avoid big data buffers or things like
4113 Having only the stack as writable memory limits means we cannot use
4114 normal global data to share information between the code. But it
4115 turned out that the implementation of U-Boot can be greatly
4116 simplified by making a global data structure (gd_t) available to all
4117 functions. We could pass a pointer to this data as argument to _all_
4118 functions, but this would bloat the code. Instead we use a feature of
4119 the GCC compiler (Global Register Variables) to share the data: we
4120 place a pointer (gd) to the global data into a register which we
4121 reserve for this purpose.
4123 When choosing a register for such a purpose we are restricted by the
4124 relevant (E)ABI specifications for the current architecture, and by
4125 GCC's implementation.
4127 For PowerPC, the following registers have specific use:
4129 R2: reserved for system use
4130 R3-R4: parameter passing and return values
4131 R5-R10: parameter passing
4132 R13: small data area pointer
4136 (U-Boot also uses R12 as internal GOT pointer. r12
4137 is a volatile register so r12 needs to be reset when
4138 going back and forth between asm and C)
4140 ==> U-Boot will use R2 to hold a pointer to the global data
4142 Note: on PPC, we could use a static initializer (since the
4143 address of the global data structure is known at compile time),
4144 but it turned out that reserving a register results in somewhat
4145 smaller code - although the code savings are not that big (on
4146 average for all boards 752 bytes for the whole U-Boot image,
4147 624 text + 127 data).
4149 On ARM, the following registers are used:
4151 R0: function argument word/integer result
4152 R1-R3: function argument word
4153 R9: platform specific
4154 R10: stack limit (used only if stack checking is enabled)
4155 R11: argument (frame) pointer
4156 R12: temporary workspace
4159 R15: program counter
4161 ==> U-Boot will use R9 to hold a pointer to the global data
4163 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4165 On Nios II, the ABI is documented here:
4166 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4168 ==> U-Boot will use gp to hold a pointer to the global data
4170 Note: on Nios II, we give "-G0" option to gcc and don't use gp
4171 to access small data sections, so gp is free.
4173 On NDS32, the following registers are used:
4175 R0-R1: argument/return
4177 R15: temporary register for assembler
4178 R16: trampoline register
4179 R28: frame pointer (FP)
4180 R29: global pointer (GP)
4181 R30: link register (LP)
4182 R31: stack pointer (SP)
4183 PC: program counter (PC)
4185 ==> U-Boot will use R10 to hold a pointer to the global data
4187 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4188 or current versions of GCC may "optimize" the code too much.
4190 On RISC-V, the following registers are used:
4192 x0: hard-wired zero (zero)
4193 x1: return address (ra)
4194 x2: stack pointer (sp)
4195 x3: global pointer (gp)
4196 x4: thread pointer (tp)
4197 x5: link register (t0)
4198 x8: frame pointer (fp)
4199 x10-x11: arguments/return values (a0-1)
4200 x12-x17: arguments (a2-7)
4201 x28-31: temporaries (t3-6)
4202 pc: program counter (pc)
4204 ==> U-Boot will use gp to hold a pointer to the global data
4209 U-Boot runs in system state and uses physical addresses, i.e. the
4210 MMU is not used either for address mapping nor for memory protection.
4212 The available memory is mapped to fixed addresses using the memory
4213 controller. In this process, a contiguous block is formed for each
4214 memory type (Flash, SDRAM, SRAM), even when it consists of several
4215 physical memory banks.
4217 U-Boot is installed in the first 128 kB of the first Flash bank (on
4218 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4219 booting and sizing and initializing DRAM, the code relocates itself
4220 to the upper end of DRAM. Immediately below the U-Boot code some
4221 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4222 configuration setting]. Below that, a structure with global Board
4223 Info data is placed, followed by the stack (growing downward).
4225 Additionally, some exception handler code is copied to the low 8 kB
4226 of DRAM (0x00000000 ... 0x00001FFF).
4228 So a typical memory configuration with 16 MB of DRAM could look like
4231 0x0000 0000 Exception Vector code
4234 0x0000 2000 Free for Application Use
4240 0x00FB FF20 Monitor Stack (Growing downward)
4241 0x00FB FFAC Board Info Data and permanent copy of global data
4242 0x00FC 0000 Malloc Arena
4245 0x00FE 0000 RAM Copy of Monitor Code
4246 ... eventually: LCD or video framebuffer
4247 ... eventually: pRAM (Protected RAM - unchanged by reset)
4248 0x00FF FFFF [End of RAM]
4251 System Initialization:
4252 ----------------------
4254 In the reset configuration, U-Boot starts at the reset entry point
4255 (on most PowerPC systems at address 0x00000100). Because of the reset
4256 configuration for CS0# this is a mirror of the on board Flash memory.
4257 To be able to re-map memory U-Boot then jumps to its link address.
4258 To be able to implement the initialization code in C, a (small!)
4259 initial stack is set up in the internal Dual Ported RAM (in case CPUs
4260 which provide such a feature like), or in a locked part of the data
4261 cache. After that, U-Boot initializes the CPU core, the caches and
4264 Next, all (potentially) available memory banks are mapped using a
4265 preliminary mapping. For example, we put them on 512 MB boundaries
4266 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4267 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4268 programmed for SDRAM access. Using the temporary configuration, a
4269 simple memory test is run that determines the size of the SDRAM
4272 When there is more than one SDRAM bank, and the banks are of
4273 different size, the largest is mapped first. For equal size, the first
4274 bank (CS2#) is mapped first. The first mapping is always for address
4275 0x00000000, with any additional banks following immediately to create
4276 contiguous memory starting from 0.
4278 Then, the monitor installs itself at the upper end of the SDRAM area
4279 and allocates memory for use by malloc() and for the global Board
4280 Info data; also, the exception vector code is copied to the low RAM
4281 pages, and the final stack is set up.
4283 Only after this relocation will you have a "normal" C environment;
4284 until that you are restricted in several ways, mostly because you are
4285 running from ROM, and because the code will have to be relocated to a
4289 U-Boot Porting Guide:
4290 ----------------------
4292 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4296 int main(int argc, char *argv[])
4298 sighandler_t no_more_time;
4300 signal(SIGALRM, no_more_time);
4301 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4303 if (available_money > available_manpower) {
4304 Pay consultant to port U-Boot;
4308 Download latest U-Boot source;
4310 Subscribe to u-boot mailing list;
4313 email("Hi, I am new to U-Boot, how do I get started?");
4316 Read the README file in the top level directory;
4317 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
4318 Read applicable doc/README.*;
4319 Read the source, Luke;
4320 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4323 if (available_money > toLocalCurrency ($2500))
4326 Add a lot of aggravation and time;
4328 if (a similar board exists) { /* hopefully... */
4329 cp -a board/<similar> board/<myboard>
4330 cp include/configs/<similar>.h include/configs/<myboard>.h
4332 Create your own board support subdirectory;
4333 Create your own board include/configs/<myboard>.h file;
4335 Edit new board/<myboard> files
4336 Edit new include/configs/<myboard>.h
4341 Add / modify source code;
4345 email("Hi, I am having problems...");
4347 Send patch file to the U-Boot email list;
4348 if (reasonable critiques)
4349 Incorporate improvements from email list code review;
4351 Defend code as written;
4357 void no_more_time (int sig)
4366 All contributions to U-Boot should conform to the Linux kernel
4367 coding style; see the kernel coding style guide at
4368 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4369 script "scripts/Lindent" in your Linux kernel source directory.
4371 Source files originating from a different project (for example the
4372 MTD subsystem) are generally exempt from these guidelines and are not
4373 reformatted to ease subsequent migration to newer versions of those
4376 Please note that U-Boot is implemented in C (and to some small parts in
4377 Assembler); no C++ is used, so please do not use C++ style comments (//)
4380 Please also stick to the following formatting rules:
4381 - remove any trailing white space
4382 - use TAB characters for indentation and vertical alignment, not spaces
4383 - make sure NOT to use DOS '\r\n' line feeds
4384 - do not add more than 2 consecutive empty lines to source files
4385 - do not add trailing empty lines to source files
4387 Submissions which do not conform to the standards may be returned
4388 with a request to reformat the changes.
4394 Since the number of patches for U-Boot is growing, we need to
4395 establish some rules. Submissions which do not conform to these rules
4396 may be rejected, even when they contain important and valuable stuff.
4398 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
4400 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4401 see https://lists.denx.de/listinfo/u-boot
4403 When you send a patch, please include the following information with
4406 * For bug fixes: a description of the bug and how your patch fixes
4407 this bug. Please try to include a way of demonstrating that the
4408 patch actually fixes something.
4410 * For new features: a description of the feature and your
4413 * For major contributions, add a MAINTAINERS file with your
4414 information and associated file and directory references.
4416 * When you add support for a new board, don't forget to add a
4417 maintainer e-mail address to the boards.cfg file, too.
4419 * If your patch adds new configuration options, don't forget to
4420 document these in the README file.
4422 * The patch itself. If you are using git (which is *strongly*
4423 recommended) you can easily generate the patch using the
4424 "git format-patch". If you then use "git send-email" to send it to
4425 the U-Boot mailing list, you will avoid most of the common problems
4426 with some other mail clients.
4428 If you cannot use git, use "diff -purN OLD NEW". If your version of
4429 diff does not support these options, then get the latest version of
4432 The current directory when running this command shall be the parent
4433 directory of the U-Boot source tree (i. e. please make sure that
4434 your patch includes sufficient directory information for the
4437 We prefer patches as plain text. MIME attachments are discouraged,
4438 and compressed attachments must not be used.
4440 * If one logical set of modifications affects or creates several
4441 files, all these changes shall be submitted in a SINGLE patch file.
4443 * Changesets that contain different, unrelated modifications shall be
4444 submitted as SEPARATE patches, one patch per changeset.
4449 * Before sending the patch, run the buildman script on your patched
4450 source tree and make sure that no errors or warnings are reported
4451 for any of the boards.
4453 * Keep your modifications to the necessary minimum: A patch
4454 containing several unrelated changes or arbitrary reformats will be
4455 returned with a request to re-formatting / split it.
4457 * If you modify existing code, make sure that your new code does not
4458 add to the memory footprint of the code ;-) Small is beautiful!
4459 When adding new features, these should compile conditionally only
4460 (using #ifdef), and the resulting code with the new feature
4461 disabled must not need more memory than the old code without your
4464 * Remember that there is a size limit of 100 kB per message on the
4465 u-boot mailing list. Bigger patches will be moderated. If they are
4466 reasonable and not too big, they will be acknowledged. But patches
4467 bigger than the size limit should be avoided.
projects / platform / kernel / u-boot.git / blob