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
468 CONFIG_SYS_FSL_IFC_BE
469 Defines the IFC controller register space as Big Endian
471 CONFIG_SYS_FSL_IFC_LE
472 Defines the IFC controller register space as Little Endian
474 CONFIG_SYS_FSL_IFC_CLK_DIV
475 Defines divider of platform clock(clock input to IFC controller).
477 CONFIG_SYS_FSL_LBC_CLK_DIV
478 Defines divider of platform clock(clock input to eLBC controller).
480 CONFIG_SYS_FSL_DDR_BE
481 Defines the DDR controller register space as Big Endian
483 CONFIG_SYS_FSL_DDR_LE
484 Defines the DDR controller register space as Little Endian
486 CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
487 Physical address from the view of DDR controllers. It is the
488 same as CONFIG_SYS_DDR_SDRAM_BASE for all Power SoCs. But
489 it could be different for ARM SoCs.
491 CONFIG_SYS_FSL_DDR_INTLV_256B
492 DDR controller interleaving on 256-byte. This is a special
493 interleaving mode, handled by Dickens for Freescale layerscape
496 CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
497 Number of controllers used as main memory.
499 CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
500 Number of controllers used for other than main memory.
502 CONFIG_SYS_FSL_HAS_DP_DDR
503 Defines the SoC has DP-DDR used for DPAA.
505 CONFIG_SYS_FSL_SEC_BE
506 Defines the SEC controller register space as Big Endian
508 CONFIG_SYS_FSL_SEC_LE
509 Defines the SEC controller register space as Little Endian
512 CONFIG_SYS_INIT_SP_OFFSET
514 Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
515 pointer. This is needed for the temporary stack before
518 CONFIG_XWAY_SWAP_BYTES
520 Enable compilation of tools/xway-swap-bytes needed for Lantiq
521 XWAY SoCs for booting from NOR flash. The U-Boot image needs to
522 be swapped if a flash programmer is used.
525 CONFIG_SYS_EXCEPTION_VECTORS_HIGH
527 Select high exception vectors of the ARM core, e.g., do not
528 clear the V bit of the c1 register of CP15.
531 Generic timer clock source frequency.
533 COUNTER_FREQUENCY_REAL
534 Generic timer clock source frequency if the real clock is
535 different from COUNTER_FREQUENCY, and can only be determined
539 CONFIG_TEGRA_SUPPORT_NON_SECURE
541 Support executing U-Boot in non-secure (NS) mode. Certain
542 impossible actions will be skipped if the CPU is in NS mode,
543 such as ARM architectural timer initialization.
545 - Linux Kernel Interface:
546 CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]
548 When transferring memsize parameter to Linux, some versions
549 expect it to be in bytes, others in MB.
550 Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
554 New kernel versions are expecting firmware settings to be
555 passed using flattened device trees (based on open firmware
559 * New libfdt-based support
560 * Adds the "fdt" command
561 * The bootm command automatically updates the fdt
563 OF_TBCLK - The timebase frequency.
565 boards with QUICC Engines require OF_QE to set UCC MAC
568 CONFIG_OF_BOARD_SETUP
570 Board code has addition modification that it wants to make
571 to the flat device tree before handing it off to the kernel
573 CONFIG_OF_SYSTEM_SETUP
575 Other code has addition modification that it wants to make
576 to the flat device tree before handing it off to the kernel.
577 This causes ft_system_setup() to be called before booting
582 U-Boot can detect if an IDE device is present or not.
583 If not, and this new config option is activated, U-Boot
584 removes the ATA node from the DTS before booting Linux,
585 so the Linux IDE driver does not probe the device and
586 crash. This is needed for buggy hardware (uc101) where
587 no pull down resistor is connected to the signal IDE5V_DD7.
589 - vxWorks boot parameters:
591 bootvx constructs a valid bootline using the following
592 environments variables: bootdev, bootfile, ipaddr, netmask,
593 serverip, gatewayip, hostname, othbootargs.
594 It loads the vxWorks image pointed bootfile.
596 Note: If a "bootargs" environment is defined, it will override
597 the defaults discussed just above.
599 - Cache Configuration:
600 CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
602 - Cache Configuration for ARM:
603 CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
605 CONFIG_SYS_PL310_BASE - Physical base address of PL310
606 controller register space
611 Define this if you want support for Amba PrimeCell PL011 UARTs.
615 If you have Amba PrimeCell PL011 UARTs, set this variable to
616 the clock speed of the UARTs.
620 If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
621 define this to a list of base addresses for each (supported)
622 port. See e.g. include/configs/versatile.h
624 CONFIG_SERIAL_HW_FLOW_CONTROL
626 Define this variable to enable hw flow control in serial driver.
627 Current user of this option is drivers/serial/nsl16550.c driver
631 Only needed when CONFIG_BOOTDELAY is enabled;
632 define a command string that is automatically executed
633 when no character is read on the console interface
634 within "Boot Delay" after reset.
636 CONFIG_RAMBOOT and CONFIG_NFSBOOT
637 The value of these goes into the environment as
638 "ramboot" and "nfsboot" respectively, and can be used
639 as a convenience, when switching between booting from
642 - Serial Download Echo Mode:
644 If defined to 1, all characters received during a
645 serial download (using the "loads" command) are
646 echoed back. This might be needed by some terminal
647 emulations (like "cu"), but may as well just take
648 time on others. This setting #define's the initial
649 value of the "loads_echo" environment variable.
651 - Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
653 Select one of the baudrates listed in
654 CONFIG_SYS_BAUDRATE_TABLE, see below.
656 - Removal of commands
657 If no commands are needed to boot, you can disable
658 CONFIG_CMDLINE to remove them. In this case, the command line
659 will not be available, and when U-Boot wants to execute the
660 boot command (on start-up) it will call board_run_command()
661 instead. This can reduce image size significantly for very
662 simple boot procedures.
664 - Regular expression support:
666 If this variable is defined, U-Boot is linked against
667 the SLRE (Super Light Regular Expression) library,
668 which adds regex support to some commands, as for
669 example "env grep" and "setexpr".
673 If this variable is defined, U-Boot will use a device tree
674 to configure its devices, instead of relying on statically
675 compiled #defines in the board file. This option is
676 experimental and only available on a few boards. The device
677 tree is available in the global data as gd->fdt_blob.
679 U-Boot needs to get its device tree from somewhere. This can
680 be done using one of the three options below:
683 If this variable is defined, U-Boot will embed a device tree
684 binary in its image. This device tree file should be in the
685 board directory and called <soc>-<board>.dts. The binary file
686 is then picked up in board_init_f() and made available through
687 the global data structure as gd->fdt_blob.
690 If this variable is defined, U-Boot will build a device tree
691 binary. It will be called u-boot.dtb. Architecture-specific
692 code will locate it at run-time. Generally this works by:
694 cat u-boot.bin u-boot.dtb >image.bin
696 and in fact, U-Boot does this for you, creating a file called
697 u-boot-dtb.bin which is useful in the common case. You can
698 still use the individual files if you need something more
702 If this variable is defined, U-Boot will use the device tree
703 provided by the board at runtime instead of embedding one with
704 the image. Only boards defining board_fdt_blob_setup() support
705 this option (see include/fdtdec.h file).
709 If this variable is defined, it enables watchdog
710 support for the SoC. There must be support in the SoC
711 specific code for a watchdog. For the 8xx
712 CPUs, the SIU Watchdog feature is enabled in the SYPCR
713 register. When supported for a specific SoC is
714 available, then no further board specific code should
718 When using a watchdog circuitry external to the used
719 SoC, then define this variable and provide board
720 specific code for the "hw_watchdog_reset" function.
722 CONFIG_SYS_WATCHDOG_FREQ
723 Some platforms automatically call WATCHDOG_RESET()
724 from the timer interrupt handler every
725 CONFIG_SYS_WATCHDOG_FREQ interrupts. If not set by the
726 board configuration file, a default of CONFIG_SYS_HZ/2
727 (i.e. 500) is used. Setting CONFIG_SYS_WATCHDOG_FREQ
728 to 0 disables calling WATCHDOG_RESET() from the timer
733 When CONFIG_CMD_DATE is selected, the type of the RTC
734 has to be selected, too. Define exactly one of the
737 CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
738 CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
739 CONFIG_RTC_MC146818 - use MC146818 RTC
740 CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
741 CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
742 CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
743 CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
744 CONFIG_RTC_DS164x - use Dallas DS164x RTC
745 CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
746 CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
747 CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
748 CONFIG_SYS_RV3029_TCR - enable trickle charger on
751 Note that if the RTC uses I2C, then the I2C interface
752 must also be configured. See I2C Support, below.
755 CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
757 The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
758 chip-ngpio pairs that tell the PCA953X driver the number of
759 pins supported by a particular chip.
761 Note that if the GPIO device uses I2C, then the I2C interface
762 must also be configured. See I2C Support, below.
765 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
766 accesses and can checksum them or write a list of them out
767 to memory. See the 'iotrace' command for details. This is
768 useful for testing device drivers since it can confirm that
769 the driver behaves the same way before and after a code
770 change. Currently this is supported on sandbox and arm. To
771 add support for your architecture, add '#include <iotrace.h>'
772 to the bottom of arch/<arch>/include/asm/io.h and test.
774 Example output from the 'iotrace stats' command is below.
775 Note that if the trace buffer is exhausted, the checksum will
776 still continue to operate.
779 Start: 10000000 (buffer start address)
780 Size: 00010000 (buffer size)
781 Offset: 00000120 (current buffer offset)
782 Output: 10000120 (start + offset)
783 Count: 00000018 (number of trace records)
784 CRC32: 9526fb66 (CRC32 of all trace records)
788 When CONFIG_TIMESTAMP is selected, the timestamp
789 (date and time) of an image is printed by image
790 commands like bootm or iminfo. This option is
791 automatically enabled when you select CONFIG_CMD_DATE .
793 - Partition Labels (disklabels) Supported:
794 Zero or more of the following:
795 CONFIG_MAC_PARTITION Apple's MacOS partition table.
796 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
797 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
798 bootloader. Note 2TB partition limit; see
800 CONFIG_SCSI) you must configure support for at
801 least one non-MTD partition type as well.
804 CONFIG_IDE_RESET_ROUTINE - this is defined in several
805 board configurations files but used nowhere!
807 CONFIG_IDE_RESET - is this is defined, IDE Reset will
808 be performed by calling the function
809 ide_set_reset(int reset)
810 which has to be defined in a board specific file
815 Set this to enable ATAPI support.
820 Set this to enable support for disks larger than 137GB
821 Also look at CONFIG_SYS_64BIT_LBA.
822 Whithout these , LBA48 support uses 32bit variables and will 'only'
823 support disks up to 2.1TB.
825 CONFIG_SYS_64BIT_LBA:
826 When enabled, makes the IDE subsystem use 64bit sector addresses.
830 CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
831 CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
832 CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
833 maximum numbers of LUNs, SCSI ID's and target
836 The environment variable 'scsidevs' is set to the number of
837 SCSI devices found during the last scan.
839 - NETWORK Support (PCI):
841 Support for Intel 8254x/8257x gigabit chips.
844 Utility code for direct access to the SPI bus on Intel 8257x.
845 This does not do anything useful unless you set at least one
846 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
848 CONFIG_E1000_SPI_GENERIC
849 Allow generic access to the SPI bus on the Intel 8257x, for
850 example with the "sspi" command.
853 Support for National dp83815 chips.
856 Support for National dp8382[01] gigabit chips.
858 - NETWORK Support (other):
860 CONFIG_DRIVER_AT91EMAC
861 Support for AT91RM9200 EMAC.
864 Define this to use reduced MII inteface
866 CONFIG_DRIVER_AT91EMAC_QUIET
867 If this defined, the driver is quiet.
868 The driver doen't show link status messages.
871 Support for the Calxeda XGMAC device
874 Support for SMSC's LAN91C96 chips.
876 CONFIG_LAN91C96_USE_32_BIT
877 Define this to enable 32 bit addressing
880 Support for SMSC's LAN91C111 chip
883 Define this to hold the physical address
884 of the device (I/O space)
886 CONFIG_SMC_USE_32_BIT
887 Define this if data bus is 32 bits
889 CONFIG_SMC_USE_IOFUNCS
890 Define this to use i/o functions instead of macros
891 (some hardware wont work with macros)
893 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
894 Define this if you have more then 3 PHYs.
897 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
899 CONFIG_FTGMAC100_EGIGA
900 Define this to use GE link update with gigabit PHY.
901 Define this if FTGMAC100 is connected to gigabit PHY.
902 If your system has 10/100 PHY only, it might not occur
903 wrong behavior. Because PHY usually return timeout or
904 useless data when polling gigabit status and gigabit
905 control registers. This behavior won't affect the
906 correctnessof 10/100 link speed update.
909 Support for Renesas on-chip Ethernet controller
911 CONFIG_SH_ETHER_USE_PORT
912 Define the number of ports to be used
914 CONFIG_SH_ETHER_PHY_ADDR
915 Define the ETH PHY's address
917 CONFIG_SH_ETHER_CACHE_WRITEBACK
918 If this option is set, the driver enables cache flush.
924 CONFIG_TPM_TIS_INFINEON
925 Support for Infineon i2c bus TPM devices. Only one device
926 per system is supported at this time.
928 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
929 Define the burst count bytes upper limit
932 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
934 CONFIG_TPM_ST33ZP24_I2C
935 Support for STMicroelectronics ST33ZP24 I2C devices.
936 Requires TPM_ST33ZP24 and I2C.
938 CONFIG_TPM_ST33ZP24_SPI
939 Support for STMicroelectronics ST33ZP24 SPI devices.
940 Requires TPM_ST33ZP24 and SPI.
943 Support for Atmel TWI TPM device. Requires I2C support.
946 Support for generic parallel port TPM devices. Only one device
947 per system is supported at this time.
949 CONFIG_TPM_TIS_BASE_ADDRESS
950 Base address where the generic TPM device is mapped
951 to. Contemporary x86 systems usually map it at
955 Define this to enable the TPM support library which provides
956 functional interfaces to some TPM commands.
957 Requires support for a TPM device.
959 CONFIG_TPM_AUTH_SESSIONS
960 Define this to enable authorized functions in the TPM library.
961 Requires CONFIG_TPM and CONFIG_SHA1.
964 At the moment only the UHCI host controller is
965 supported (PIP405, MIP405); define
966 CONFIG_USB_UHCI to enable it.
967 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
968 and define CONFIG_USB_STORAGE to enable the USB
971 Supported are USB Keyboards and USB Floppy drives
974 CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
975 txfilltuning field in the EHCI controller on reset.
977 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
981 Define the below if you wish to use the USB console.
982 Once firmware is rebuilt from a serial console issue the
983 command "setenv stdin usbtty; setenv stdout usbtty" and
984 attach your USB cable. The Unix command "dmesg" should print
985 it has found a new device. The environment variable usbtty
986 can be set to gserial or cdc_acm to enable your device to
987 appear to a USB host as a Linux gserial device or a
988 Common Device Class Abstract Control Model serial device.
989 If you select usbtty = gserial you should be able to enumerate
991 # modprobe usbserial vendor=0xVendorID product=0xProductID
992 else if using cdc_acm, simply setting the environment
993 variable usbtty to be cdc_acm should suffice. The following
994 might be defined in YourBoardName.h
997 Define this to build a UDC device
1000 Define this to have a tty type of device available to
1001 talk to the UDC device
1004 Define this to enable the high speed support for usb
1005 device and usbtty. If this feature is enabled, a routine
1006 int is_usbd_high_speed(void)
1007 also needs to be defined by the driver to dynamically poll
1008 whether the enumeration has succeded at high speed or full
1011 CONFIG_SYS_CONSOLE_IS_IN_ENV
1012 Define this if you want stdin, stdout &/or stderr to
1015 If you have a USB-IF assigned VendorID then you may wish to
1016 define your own vendor specific values either in BoardName.h
1017 or directly in usbd_vendor_info.h. If you don't define
1018 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1019 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1020 should pretend to be a Linux device to it's target host.
1022 CONFIG_USBD_MANUFACTURER
1023 Define this string as the name of your company for
1024 - CONFIG_USBD_MANUFACTURER "my company"
1026 CONFIG_USBD_PRODUCT_NAME
1027 Define this string as the name of your product
1028 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1030 CONFIG_USBD_VENDORID
1031 Define this as your assigned Vendor ID from the USB
1032 Implementors Forum. This *must* be a genuine Vendor ID
1033 to avoid polluting the USB namespace.
1034 - CONFIG_USBD_VENDORID 0xFFFF
1036 CONFIG_USBD_PRODUCTID
1037 Define this as the unique Product ID
1039 - CONFIG_USBD_PRODUCTID 0xFFFF
1041 - ULPI Layer Support:
1042 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1043 the generic ULPI layer. The generic layer accesses the ULPI PHY
1044 via the platform viewport, so you need both the genric layer and
1045 the viewport enabled. Currently only Chipidea/ARC based
1046 viewport is supported.
1047 To enable the ULPI layer support, define CONFIG_USB_ULPI and
1048 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1049 If your ULPI phy needs a different reference clock than the
1050 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1051 the appropriate value in Hz.
1054 The MMC controller on the Intel PXA is supported. To
1055 enable this define CONFIG_MMC. The MMC can be
1056 accessed from the boot prompt by mapping the device
1057 to physical memory similar to flash. Command line is
1058 enabled with CONFIG_CMD_MMC. The MMC driver also works with
1059 the FAT fs. This is enabled with CONFIG_CMD_FAT.
1062 Support for Renesas on-chip MMCIF controller
1064 CONFIG_SH_MMCIF_ADDR
1065 Define the base address of MMCIF registers
1068 Define the clock frequency for MMCIF
1070 - USB Device Firmware Update (DFU) class support:
1072 This enables the USB portion of the DFU USB class
1075 This enables support for exposing NAND devices via DFU.
1078 This enables support for exposing RAM via DFU.
1079 Note: DFU spec refer to non-volatile memory usage, but
1080 allow usages beyond the scope of spec - here RAM usage,
1081 one that would help mostly the developer.
1083 CONFIG_SYS_DFU_DATA_BUF_SIZE
1084 Dfu transfer uses a buffer before writing data to the
1085 raw storage device. Make the size (in bytes) of this buffer
1086 configurable. The size of this buffer is also configurable
1087 through the "dfu_bufsiz" environment variable.
1089 CONFIG_SYS_DFU_MAX_FILE_SIZE
1090 When updating files rather than the raw storage device,
1091 we use a static buffer to copy the file into and then write
1092 the buffer once we've been given the whole file. Define
1093 this to the maximum filesize (in bytes) for the buffer.
1094 Default is 4 MiB if undefined.
1096 DFU_DEFAULT_POLL_TIMEOUT
1097 Poll timeout [ms], is the timeout a device can send to the
1098 host. The host must wait for this timeout before sending
1099 a subsequent DFU_GET_STATUS request to the device.
1101 DFU_MANIFEST_POLL_TIMEOUT
1102 Poll timeout [ms], which the device sends to the host when
1103 entering dfuMANIFEST state. Host waits this timeout, before
1104 sending again an USB request to the device.
1106 - Journaling Flash filesystem support:
1108 Define these for a default partition on a NAND device
1110 CONFIG_SYS_JFFS2_FIRST_SECTOR,
1111 CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1112 Define these for a default partition on a NOR device
1115 See Kconfig help for available keyboard drivers.
1119 Define this to enable a custom keyboard support.
1120 This simply calls drv_keyboard_init() which must be
1121 defined in your board-specific files. This option is deprecated
1122 and is only used by novena. For new boards, use driver model
1127 Enable the Freescale DIU video driver. Reference boards for
1128 SOCs that have a DIU should define this macro to enable DIU
1129 support, and should also define these other macros:
1134 CONFIG_VIDEO_SW_CURSOR
1135 CONFIG_VGA_AS_SINGLE_DEVICE
1137 CONFIG_VIDEO_BMP_LOGO
1139 The DIU driver will look for the 'video-mode' environment
1140 variable, and if defined, enable the DIU as a console during
1141 boot. See the documentation file doc/README.video for a
1142 description of this variable.
1144 - LCD Support: CONFIG_LCD
1146 Define this to enable LCD support (for output to LCD
1147 display); also select one of the supported displays
1148 by defining one of these:
1152 HITACHI TX09D70VM1CCA, 3.5", 240x320.
1154 CONFIG_NEC_NL6448AC33:
1156 NEC NL6448AC33-18. Active, color, single scan.
1158 CONFIG_NEC_NL6448BC20
1160 NEC NL6448BC20-08. 6.5", 640x480.
1161 Active, color, single scan.
1163 CONFIG_NEC_NL6448BC33_54
1165 NEC NL6448BC33-54. 10.4", 640x480.
1166 Active, color, single scan.
1170 Sharp 320x240. Active, color, single scan.
1171 It isn't 16x9, and I am not sure what it is.
1173 CONFIG_SHARP_LQ64D341
1175 Sharp LQ64D341 display, 640x480.
1176 Active, color, single scan.
1180 HLD1045 display, 640x480.
1181 Active, color, single scan.
1185 Optrex CBL50840-2 NF-FW 99 22 M5
1187 Hitachi LMG6912RPFC-00T
1191 320x240. Black & white.
1193 CONFIG_LCD_ALIGNMENT
1195 Normally the LCD is page-aligned (typically 4KB). If this is
1196 defined then the LCD will be aligned to this value instead.
1197 For ARM it is sometimes useful to use MMU_SECTION_SIZE
1198 here, since it is cheaper to change data cache settings on
1199 a per-section basis.
1204 Sometimes, for example if the display is mounted in portrait
1205 mode or even if it's mounted landscape but rotated by 180degree,
1206 we need to rotate our content of the display relative to the
1207 framebuffer, so that user can read the messages which are
1209 Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1210 initialized with a given rotation from "vl_rot" out of
1211 "vidinfo_t" which is provided by the board specific code.
1212 The value for vl_rot is coded as following (matching to
1213 fbcon=rotate:<n> linux-kernel commandline):
1214 0 = no rotation respectively 0 degree
1215 1 = 90 degree rotation
1216 2 = 180 degree rotation
1217 3 = 270 degree rotation
1219 If CONFIG_LCD_ROTATION is not defined, the console will be
1220 initialized with 0degree rotation.
1224 Support drawing of RLE8-compressed bitmaps on the LCD.
1228 Enables an 'i2c edid' command which can read EDID
1229 information over I2C from an attached LCD display.
1232 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1234 The clock frequency of the MII bus
1236 CONFIG_PHY_RESET_DELAY
1238 Some PHY like Intel LXT971A need extra delay after
1239 reset before any MII register access is possible.
1240 For such PHY, set this option to the usec delay
1241 required. (minimum 300usec for LXT971A)
1243 CONFIG_PHY_CMD_DELAY (ppc4xx)
1245 Some PHY like Intel LXT971A need extra delay after
1246 command issued before MII status register can be read
1251 Define a default value for the IP address to use for
1252 the default Ethernet interface, in case this is not
1253 determined through e.g. bootp.
1254 (Environment variable "ipaddr")
1256 - Server IP address:
1259 Defines a default value for the IP address of a TFTP
1260 server to contact when using the "tftboot" command.
1261 (Environment variable "serverip")
1263 CONFIG_KEEP_SERVERADDR
1265 Keeps the server's MAC address, in the env 'serveraddr'
1266 for passing to bootargs (like Linux's netconsole option)
1268 - Gateway IP address:
1271 Defines a default value for the IP address of the
1272 default router where packets to other networks are
1274 (Environment variable "gatewayip")
1279 Defines a default value for the subnet mask (or
1280 routing prefix) which is used to determine if an IP
1281 address belongs to the local subnet or needs to be
1282 forwarded through a router.
1283 (Environment variable "netmask")
1285 - BOOTP Recovery Mode:
1286 CONFIG_BOOTP_RANDOM_DELAY
1288 If you have many targets in a network that try to
1289 boot using BOOTP, you may want to avoid that all
1290 systems send out BOOTP requests at precisely the same
1291 moment (which would happen for instance at recovery
1292 from a power failure, when all systems will try to
1293 boot, thus flooding the BOOTP server. Defining
1294 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1295 inserted before sending out BOOTP requests. The
1296 following delays are inserted then:
1298 1st BOOTP request: delay 0 ... 1 sec
1299 2nd BOOTP request: delay 0 ... 2 sec
1300 3rd BOOTP request: delay 0 ... 4 sec
1302 BOOTP requests: delay 0 ... 8 sec
1304 CONFIG_BOOTP_ID_CACHE_SIZE
1306 BOOTP packets are uniquely identified using a 32-bit ID. The
1307 server will copy the ID from client requests to responses and
1308 U-Boot will use this to determine if it is the destination of
1309 an incoming response. Some servers will check that addresses
1310 aren't in use before handing them out (usually using an ARP
1311 ping) and therefore take up to a few hundred milliseconds to
1312 respond. Network congestion may also influence the time it
1313 takes for a response to make it back to the client. If that
1314 time is too long, U-Boot will retransmit requests. In order
1315 to allow earlier responses to still be accepted after these
1316 retransmissions, U-Boot's BOOTP client keeps a small cache of
1317 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1318 cache. The default is to keep IDs for up to four outstanding
1319 requests. Increasing this will allow U-Boot to accept offers
1320 from a BOOTP client in networks with unusually high latency.
1322 - DHCP Advanced Options:
1323 You can fine tune the DHCP functionality by defining
1324 CONFIG_BOOTP_* symbols:
1326 CONFIG_BOOTP_NISDOMAIN
1327 CONFIG_BOOTP_BOOTFILESIZE
1328 CONFIG_BOOTP_NTPSERVER
1329 CONFIG_BOOTP_TIMEOFFSET
1330 CONFIG_BOOTP_VENDOREX
1331 CONFIG_BOOTP_MAY_FAIL
1333 CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1334 environment variable, not the BOOTP server.
1336 CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1337 after the configured retry count, the call will fail
1338 instead of starting over. This can be used to fail over
1339 to Link-local IP address configuration if the DHCP server
1342 CONFIG_BOOTP_DHCP_REQUEST_DELAY
1344 A 32bit value in microseconds for a delay between
1345 receiving a "DHCP Offer" and sending the "DHCP Request".
1346 This fixes a problem with certain DHCP servers that don't
1347 respond 100% of the time to a "DHCP request". E.g. On an
1348 AT91RM9200 processor running at 180MHz, this delay needed
1349 to be *at least* 15,000 usec before a Windows Server 2003
1350 DHCP server would reply 100% of the time. I recommend at
1351 least 50,000 usec to be safe. The alternative is to hope
1352 that one of the retries will be successful but note that
1353 the DHCP timeout and retry process takes a longer than
1356 - Link-local IP address negotiation:
1357 Negotiate with other link-local clients on the local network
1358 for an address that doesn't require explicit configuration.
1359 This is especially useful if a DHCP server cannot be guaranteed
1360 to exist in all environments that the device must operate.
1362 See doc/README.link-local for more information.
1364 - MAC address from environment variables
1366 FDT_SEQ_MACADDR_FROM_ENV
1368 Fix-up device tree with MAC addresses fetched sequentially from
1369 environment variables. This config work on assumption that
1370 non-usable ethernet node of device-tree are either not present
1371 or their status has been marked as "disabled".
1374 CONFIG_CDP_DEVICE_ID
1376 The device id used in CDP trigger frames.
1378 CONFIG_CDP_DEVICE_ID_PREFIX
1380 A two character string which is prefixed to the MAC address
1385 A printf format string which contains the ascii name of
1386 the port. Normally is set to "eth%d" which sets
1387 eth0 for the first Ethernet, eth1 for the second etc.
1389 CONFIG_CDP_CAPABILITIES
1391 A 32bit integer which indicates the device capabilities;
1392 0x00000010 for a normal host which does not forwards.
1396 An ascii string containing the version of the software.
1400 An ascii string containing the name of the platform.
1404 A 32bit integer sent on the trigger.
1406 CONFIG_CDP_POWER_CONSUMPTION
1408 A 16bit integer containing the power consumption of the
1409 device in .1 of milliwatts.
1411 CONFIG_CDP_APPLIANCE_VLAN_TYPE
1413 A byte containing the id of the VLAN.
1415 - Status LED: CONFIG_LED_STATUS
1417 Several configurations allow to display the current
1418 status using a LED. For instance, the LED will blink
1419 fast while running U-Boot code, stop blinking as
1420 soon as a reply to a BOOTP request was received, and
1421 start blinking slow once the Linux kernel is running
1422 (supported by a status LED driver in the Linux
1423 kernel). Defining CONFIG_LED_STATUS enables this
1428 CONFIG_LED_STATUS_GPIO
1429 The status LED can be connected to a GPIO pin.
1430 In such cases, the gpio_led driver can be used as a
1431 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1432 to include the gpio_led driver in the U-Boot binary.
1434 CONFIG_GPIO_LED_INVERTED_TABLE
1435 Some GPIO connected LEDs may have inverted polarity in which
1436 case the GPIO high value corresponds to LED off state and
1437 GPIO low value corresponds to LED on state.
1438 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1439 with a list of GPIO LEDs that have inverted polarity.
1442 CONFIG_SYS_NUM_I2C_BUSES
1443 Hold the number of i2c buses you want to use.
1445 CONFIG_SYS_I2C_DIRECT_BUS
1446 define this, if you don't use i2c muxes on your hardware.
1447 if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1450 CONFIG_SYS_I2C_MAX_HOPS
1451 define how many muxes are maximal consecutively connected
1452 on one i2c bus. If you not use i2c muxes, omit this
1455 CONFIG_SYS_I2C_BUSES
1456 hold a list of buses you want to use, only used if
1457 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1458 a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1459 CONFIG_SYS_NUM_I2C_BUSES = 9:
1461 CONFIG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
1462 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1463 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1464 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1465 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1466 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1467 {1, {I2C_NULL_HOP}}, \
1468 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1469 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1473 bus 0 on adapter 0 without a mux
1474 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1475 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1476 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1477 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1478 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1479 bus 6 on adapter 1 without a mux
1480 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1481 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1483 If you do not have i2c muxes on your board, omit this define.
1485 - Legacy I2C Support:
1486 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1487 then the following macros need to be defined (examples are
1488 from include/configs/lwmon.h):
1492 (Optional). Any commands necessary to enable the I2C
1493 controller or configure ports.
1495 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
1499 The code necessary to make the I2C data line active
1500 (driven). If the data line is open collector, this
1503 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
1507 The code necessary to make the I2C data line tri-stated
1508 (inactive). If the data line is open collector, this
1511 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1515 Code that returns true if the I2C data line is high,
1518 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1522 If <bit> is true, sets the I2C data line high. If it
1523 is false, it clears it (low).
1525 eg: #define I2C_SDA(bit) \
1526 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
1527 else immr->im_cpm.cp_pbdat &= ~PB_SDA
1531 If <bit> is true, sets the I2C clock line high. If it
1532 is false, it clears it (low).
1534 eg: #define I2C_SCL(bit) \
1535 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
1536 else immr->im_cpm.cp_pbdat &= ~PB_SCL
1540 This delay is invoked four times per clock cycle so this
1541 controls the rate of data transfer. The data rate thus
1542 is 1 / (I2C_DELAY * 4). Often defined to be something
1545 #define I2C_DELAY udelay(2)
1547 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1549 If your arch supports the generic GPIO framework (asm/gpio.h),
1550 then you may alternatively define the two GPIOs that are to be
1551 used as SCL / SDA. Any of the previous I2C_xxx macros will
1552 have GPIO-based defaults assigned to them as appropriate.
1554 You should define these to the GPIO value as given directly to
1555 the generic GPIO functions.
1557 CONFIG_SYS_I2C_INIT_BOARD
1559 When a board is reset during an i2c bus transfer
1560 chips might think that the current transfer is still
1561 in progress. On some boards it is possible to access
1562 the i2c SCLK line directly, either by using the
1563 processor pin as a GPIO or by having a second pin
1564 connected to the bus. If this option is defined a
1565 custom i2c_init_board() routine in boards/xxx/board.c
1566 is run early in the boot sequence.
1568 CONFIG_I2C_MULTI_BUS
1570 This option allows the use of multiple I2C buses, each of which
1571 must have a controller. At any point in time, only one bus is
1572 active. To switch to a different bus, use the 'i2c dev' command.
1573 Note that bus numbering is zero-based.
1575 CONFIG_SYS_I2C_NOPROBES
1577 This option specifies a list of I2C devices that will be skipped
1578 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
1579 is set, specify a list of bus-device pairs. Otherwise, specify
1580 a 1D array of device addresses
1583 #undef CONFIG_I2C_MULTI_BUS
1584 #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1586 will skip addresses 0x50 and 0x68 on a board with one I2C bus
1588 #define CONFIG_I2C_MULTI_BUS
1589 #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1591 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1593 CONFIG_SYS_SPD_BUS_NUM
1595 If defined, then this indicates the I2C bus number for DDR SPD.
1596 If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1598 CONFIG_SYS_RTC_BUS_NUM
1600 If defined, then this indicates the I2C bus number for the RTC.
1601 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1603 CONFIG_SOFT_I2C_READ_REPEATED_START
1605 defining this will force the i2c_read() function in
1606 the soft_i2c driver to perform an I2C repeated start
1607 between writing the address pointer and reading the
1608 data. If this define is omitted the default behaviour
1609 of doing a stop-start sequence will be used. Most I2C
1610 devices can use either method, but some require one or
1613 - SPI Support: CONFIG_SPI
1615 Enables SPI driver (so far only tested with
1616 SPI EEPROM, also an instance works with Crystal A/D and
1617 D/As on the SACSng board)
1621 Enables a software (bit-bang) SPI driver rather than
1622 using hardware support. This is a general purpose
1623 driver that only requires three general I/O port pins
1624 (two outputs, one input) to function. If this is
1625 defined, the board configuration must define several
1626 SPI configuration items (port pins to use, etc). For
1627 an example, see include/configs/sacsng.h.
1629 CONFIG_SYS_SPI_MXC_WAIT
1630 Timeout for waiting until spi transfer completed.
1631 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1633 - FPGA Support: CONFIG_FPGA
1635 Enables FPGA subsystem.
1637 CONFIG_FPGA_<vendor>
1639 Enables support for specific chip vendors.
1642 CONFIG_FPGA_<family>
1644 Enables support for FPGA family.
1645 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1649 Specify the number of FPGA devices to support.
1651 CONFIG_SYS_FPGA_PROG_FEEDBACK
1653 Enable printing of hash marks during FPGA configuration.
1655 CONFIG_SYS_FPGA_CHECK_BUSY
1657 Enable checks on FPGA configuration interface busy
1658 status by the configuration function. This option
1659 will require a board or device specific function to
1664 If defined, a function that provides delays in the FPGA
1665 configuration driver.
1667 CONFIG_SYS_FPGA_CHECK_CTRLC
1668 Allow Control-C to interrupt FPGA configuration
1670 CONFIG_SYS_FPGA_CHECK_ERROR
1672 Check for configuration errors during FPGA bitfile
1673 loading. For example, abort during Virtex II
1674 configuration if the INIT_B line goes low (which
1675 indicated a CRC error).
1677 CONFIG_SYS_FPGA_WAIT_INIT
1679 Maximum time to wait for the INIT_B line to de-assert
1680 after PROB_B has been de-asserted during a Virtex II
1681 FPGA configuration sequence. The default time is 500
1684 CONFIG_SYS_FPGA_WAIT_BUSY
1686 Maximum time to wait for BUSY to de-assert during
1687 Virtex II FPGA configuration. The default is 5 ms.
1689 CONFIG_SYS_FPGA_WAIT_CONFIG
1691 Time to wait after FPGA configuration. The default is
1694 - Configuration Management:
1698 If defined, this string will be added to the U-Boot
1699 version information (U_BOOT_VERSION)
1701 - Vendor Parameter Protection:
1703 U-Boot considers the values of the environment
1704 variables "serial#" (Board Serial Number) and
1705 "ethaddr" (Ethernet Address) to be parameters that
1706 are set once by the board vendor / manufacturer, and
1707 protects these variables from casual modification by
1708 the user. Once set, these variables are read-only,
1709 and write or delete attempts are rejected. You can
1710 change this behaviour:
1712 If CONFIG_ENV_OVERWRITE is #defined in your config
1713 file, the write protection for vendor parameters is
1714 completely disabled. Anybody can change or delete
1717 Alternatively, if you define _both_ an ethaddr in the
1718 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1719 Ethernet address is installed in the environment,
1720 which can be changed exactly ONCE by the user. [The
1721 serial# is unaffected by this, i. e. it remains
1724 The same can be accomplished in a more flexible way
1725 for any variable by configuring the type of access
1726 to allow for those variables in the ".flags" variable
1727 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1732 Define this variable to enable the reservation of
1733 "protected RAM", i. e. RAM which is not overwritten
1734 by U-Boot. Define CONFIG_PRAM to hold the number of
1735 kB you want to reserve for pRAM. You can overwrite
1736 this default value by defining an environment
1737 variable "pram" to the number of kB you want to
1738 reserve. Note that the board info structure will
1739 still show the full amount of RAM. If pRAM is
1740 reserved, a new environment variable "mem" will
1741 automatically be defined to hold the amount of
1742 remaining RAM in a form that can be passed as boot
1743 argument to Linux, for instance like that:
1745 setenv bootargs ... mem=\${mem}
1748 This way you can tell Linux not to use this memory,
1749 either, which results in a memory region that will
1750 not be affected by reboots.
1752 *WARNING* If your board configuration uses automatic
1753 detection of the RAM size, you must make sure that
1754 this memory test is non-destructive. So far, the
1755 following board configurations are known to be
1758 IVMS8, IVML24, SPD8xx,
1759 HERMES, IP860, RPXlite, LWMON,
1762 - Access to physical memory region (> 4GB)
1763 Some basic support is provided for operations on memory not
1764 normally accessible to U-Boot - e.g. some architectures
1765 support access to more than 4GB of memory on 32-bit
1766 machines using physical address extension or similar.
1767 Define CONFIG_PHYSMEM to access this basic support, which
1768 currently only supports clearing the memory.
1771 CONFIG_NET_RETRY_COUNT
1773 This variable defines the number of retries for
1774 network operations like ARP, RARP, TFTP, or BOOTP
1775 before giving up the operation. If not defined, a
1776 default value of 5 is used.
1780 Timeout waiting for an ARP reply in milliseconds.
1784 Timeout in milliseconds used in NFS protocol.
1785 If you encounter "ERROR: Cannot umount" in nfs command,
1786 try longer timeout such as
1787 #define CONFIG_NFS_TIMEOUT 10000UL
1791 In the current implementation, the local variables
1792 space and global environment variables space are
1793 separated. Local variables are those you define by
1794 simply typing `name=value'. To access a local
1795 variable later on, you have write `$name' or
1796 `${name}'; to execute the contents of a variable
1797 directly type `$name' at the command prompt.
1799 Global environment variables are those you use
1800 setenv/printenv to work with. To run a command stored
1801 in such a variable, you need to use the run command,
1802 and you must not use the '$' sign to access them.
1804 To store commands and special characters in a
1805 variable, please use double quotation marks
1806 surrounding the whole text of the variable, instead
1807 of the backslashes before semicolons and special
1810 - Command Line Editing and History:
1811 CONFIG_CMDLINE_PS_SUPPORT
1813 Enable support for changing the command prompt string
1814 at run-time. Only static string is supported so far.
1815 The string is obtained from environment variables PS1
1818 - Default Environment:
1819 CONFIG_EXTRA_ENV_SETTINGS
1821 Define this to contain any number of null terminated
1822 strings (variable = value pairs) that will be part of
1823 the default environment compiled into the boot image.
1825 For example, place something like this in your
1826 board's config file:
1828 #define CONFIG_EXTRA_ENV_SETTINGS \
1832 Warning: This method is based on knowledge about the
1833 internal format how the environment is stored by the
1834 U-Boot code. This is NOT an official, exported
1835 interface! Although it is unlikely that this format
1836 will change soon, there is no guarantee either.
1837 You better know what you are doing here.
1839 Note: overly (ab)use of the default environment is
1840 discouraged. Make sure to check other ways to preset
1841 the environment like the "source" command or the
1844 CONFIG_DELAY_ENVIRONMENT
1846 Normally the environment is loaded when the board is
1847 initialised so that it is available to U-Boot. This inhibits
1848 that so that the environment is not available until
1849 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1850 this is instead controlled by the value of
1851 /config/load-environment.
1853 - TFTP Fixed UDP Port:
1856 If this is defined, the environment variable tftpsrcp
1857 is used to supply the TFTP UDP source port value.
1858 If tftpsrcp isn't defined, the normal pseudo-random port
1859 number generator is used.
1861 Also, the environment variable tftpdstp is used to supply
1862 the TFTP UDP destination port value. If tftpdstp isn't
1863 defined, the normal port 69 is used.
1865 The purpose for tftpsrcp is to allow a TFTP server to
1866 blindly start the TFTP transfer using the pre-configured
1867 target IP address and UDP port. This has the effect of
1868 "punching through" the (Windows XP) firewall, allowing
1869 the remainder of the TFTP transfer to proceed normally.
1870 A better solution is to properly configure the firewall,
1871 but sometimes that is not allowed.
1873 CONFIG_STANDALONE_LOAD_ADDR
1875 This option defines a board specific value for the
1876 address where standalone program gets loaded, thus
1877 overwriting the architecture dependent default
1880 - Frame Buffer Address:
1883 Define CONFIG_FB_ADDR if you want to use specific
1884 address for frame buffer. This is typically the case
1885 when using a graphics controller has separate video
1886 memory. U-Boot will then place the frame buffer at
1887 the given address instead of dynamically reserving it
1888 in system RAM by calling lcd_setmem(), which grabs
1889 the memory for the frame buffer depending on the
1890 configured panel size.
1892 Please see board_init_f function.
1894 - Automatic software updates via TFTP server
1896 CONFIG_UPDATE_TFTP_CNT_MAX
1897 CONFIG_UPDATE_TFTP_MSEC_MAX
1899 These options enable and control the auto-update feature;
1900 for a more detailed description refer to doc/README.update.
1902 - MTD Support (mtdparts command, UBI support)
1903 CONFIG_MTD_UBI_WL_THRESHOLD
1904 This parameter defines the maximum difference between the highest
1905 erase counter value and the lowest erase counter value of eraseblocks
1906 of UBI devices. When this threshold is exceeded, UBI starts performing
1907 wear leveling by means of moving data from eraseblock with low erase
1908 counter to eraseblocks with high erase counter.
1910 The default value should be OK for SLC NAND flashes, NOR flashes and
1911 other flashes which have eraseblock life-cycle 100000 or more.
1912 However, in case of MLC NAND flashes which typically have eraseblock
1913 life-cycle less than 10000, the threshold should be lessened (e.g.,
1914 to 128 or 256, although it does not have to be power of 2).
1918 CONFIG_MTD_UBI_BEB_LIMIT
1919 This option specifies the maximum bad physical eraseblocks UBI
1920 expects on the MTD device (per 1024 eraseblocks). If the
1921 underlying flash does not admit of bad eraseblocks (e.g. NOR
1922 flash), this value is ignored.
1924 NAND datasheets often specify the minimum and maximum NVM
1925 (Number of Valid Blocks) for the flashes' endurance lifetime.
1926 The maximum expected bad eraseblocks per 1024 eraseblocks
1927 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1928 which gives 20 for most NANDs (MaxNVB is basically the total
1929 count of eraseblocks on the chip).
1931 To put it differently, if this value is 20, UBI will try to
1932 reserve about 1.9% of physical eraseblocks for bad blocks
1933 handling. And that will be 1.9% of eraseblocks on the entire
1934 NAND chip, not just the MTD partition UBI attaches. This means
1935 that if you have, say, a NAND flash chip admits maximum 40 bad
1936 eraseblocks, and it is split on two MTD partitions of the same
1937 size, UBI will reserve 40 eraseblocks when attaching a
1942 CONFIG_MTD_UBI_FASTMAP
1943 Fastmap is a mechanism which allows attaching an UBI device
1944 in nearly constant time. Instead of scanning the whole MTD device it
1945 only has to locate a checkpoint (called fastmap) on the device.
1946 The on-flash fastmap contains all information needed to attach
1947 the device. Using fastmap makes only sense on large devices where
1948 attaching by scanning takes long. UBI will not automatically install
1949 a fastmap on old images, but you can set the UBI parameter
1950 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1951 that fastmap-enabled images are still usable with UBI implementations
1952 without fastmap support. On typical flash devices the whole fastmap
1953 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1955 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1956 Set this parameter to enable fastmap automatically on images
1960 CONFIG_MTD_UBI_FM_DEBUG
1961 Enable UBI fastmap debug
1966 Enable building of SPL globally.
1969 LDSCRIPT for linking the SPL binary.
1971 CONFIG_SPL_MAX_FOOTPRINT
1972 Maximum size in memory allocated to the SPL, BSS included.
1973 When defined, the linker checks that the actual memory
1974 used by SPL from _start to __bss_end does not exceed it.
1975 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
1976 must not be both defined at the same time.
1979 Maximum size of the SPL image (text, data, rodata, and
1980 linker lists sections), BSS excluded.
1981 When defined, the linker checks that the actual size does
1984 CONFIG_SPL_RELOC_TEXT_BASE
1985 Address to relocate to. If unspecified, this is equal to
1986 CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
1988 CONFIG_SPL_BSS_START_ADDR
1989 Link address for the BSS within the SPL binary.
1991 CONFIG_SPL_BSS_MAX_SIZE
1992 Maximum size in memory allocated to the SPL BSS.
1993 When defined, the linker checks that the actual memory used
1994 by SPL from __bss_start to __bss_end does not exceed it.
1995 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
1996 must not be both defined at the same time.
1999 Adress of the start of the stack SPL will use
2001 CONFIG_SPL_PANIC_ON_RAW_IMAGE
2002 When defined, SPL will panic() if the image it has
2003 loaded does not have a signature.
2004 Defining this is useful when code which loads images
2005 in SPL cannot guarantee that absolutely all read errors
2007 An example is the LPC32XX MLC NAND driver, which will
2008 consider that a completely unreadable NAND block is bad,
2009 and thus should be skipped silently.
2011 CONFIG_SPL_RELOC_STACK
2012 Adress of the start of the stack SPL will use after
2013 relocation. If unspecified, this is equal to
2016 CONFIG_SYS_SPL_MALLOC_START
2017 Starting address of the malloc pool used in SPL.
2018 When this option is set the full malloc is used in SPL and
2019 it is set up by spl_init() and before that, the simple malloc()
2020 can be used if CONFIG_SYS_MALLOC_F is defined.
2022 CONFIG_SYS_SPL_MALLOC_SIZE
2023 The size of the malloc pool used in SPL.
2026 Enable booting directly to an OS from SPL.
2027 See also: doc/README.falcon
2029 CONFIG_SPL_DISPLAY_PRINT
2030 For ARM, enable an optional function to print more information
2031 about the running system.
2033 CONFIG_SPL_INIT_MINIMAL
2034 Arch init code should be built for a very small image
2036 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2037 Partition on the MMC to load U-Boot from when the MMC is being
2040 CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2041 Sector to load kernel uImage from when MMC is being
2042 used in raw mode (for Falcon mode)
2044 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2045 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2046 Sector and number of sectors to load kernel argument
2047 parameters from when MMC is being used in raw mode
2050 CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2051 Filename to read to load U-Boot when reading from filesystem
2053 CONFIG_SPL_FS_LOAD_KERNEL_NAME
2054 Filename to read to load kernel uImage when reading
2055 from filesystem (for Falcon mode)
2057 CONFIG_SPL_FS_LOAD_ARGS_NAME
2058 Filename to read to load kernel argument parameters
2059 when reading from filesystem (for Falcon mode)
2061 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2062 Set this for NAND SPL on PPC mpc83xx targets, so that
2063 start.S waits for the rest of the SPL to load before
2064 continuing (the hardware starts execution after just
2065 loading the first page rather than the full 4K).
2067 CONFIG_SPL_SKIP_RELOCATE
2068 Avoid SPL relocation
2070 CONFIG_SPL_NAND_IDENT
2071 SPL uses the chip ID list to identify the NAND flash.
2072 Requires CONFIG_SPL_NAND_BASE.
2075 Support for a lightweight UBI (fastmap) scanner and
2078 CONFIG_SPL_NAND_RAW_ONLY
2079 Support to boot only raw u-boot.bin images. Use this only
2080 if you need to save space.
2082 CONFIG_SPL_COMMON_INIT_DDR
2083 Set for common ddr init with serial presence detect in
2086 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2087 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2088 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2089 CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2090 CONFIG_SYS_NAND_ECCBYTES
2091 Defines the size and behavior of the NAND that SPL uses
2094 CONFIG_SYS_NAND_U_BOOT_OFFS
2095 Location in NAND to read U-Boot from
2097 CONFIG_SYS_NAND_U_BOOT_DST
2098 Location in memory to load U-Boot to
2100 CONFIG_SYS_NAND_U_BOOT_SIZE
2101 Size of image to load
2103 CONFIG_SYS_NAND_U_BOOT_START
2104 Entry point in loaded image to jump to
2106 CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2107 Define this if you need to first read the OOB and then the
2108 data. This is used, for example, on davinci platforms.
2110 CONFIG_SPL_RAM_DEVICE
2111 Support for running image already present in ram, in SPL binary
2114 Image offset to which the SPL should be padded before appending
2115 the SPL payload. By default, this is defined as
2116 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2117 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2118 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2121 Final target image containing SPL and payload. Some SPLs
2122 use an arch-specific makefile fragment instead, for
2123 example if more than one image needs to be produced.
2125 CONFIG_SPL_FIT_PRINT
2126 Printing information about a FIT image adds quite a bit of
2127 code to SPL. So this is normally disabled in SPL. Use this
2128 option to re-enable it. This will affect the output of the
2129 bootm command when booting a FIT image.
2133 Enable building of TPL globally.
2136 Image offset to which the TPL should be padded before appending
2137 the TPL payload. By default, this is defined as
2138 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2139 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2140 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2142 - Interrupt support (PPC):
2144 There are common interrupt_init() and timer_interrupt()
2145 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2146 for CPU specific initialization. interrupt_init_cpu()
2147 should set decrementer_count to appropriate value. If
2148 CPU resets decrementer automatically after interrupt
2149 (ppc4xx) it should set decrementer_count to zero.
2150 timer_interrupt() calls timer_interrupt_cpu() for CPU
2151 specific handling. If board has watchdog / status_led
2152 / other_activity_monitor it works automatically from
2153 general timer_interrupt().
2156 Board initialization settings:
2157 ------------------------------
2159 During Initialization u-boot calls a number of board specific functions
2160 to allow the preparation of board specific prerequisites, e.g. pin setup
2161 before drivers are initialized. To enable these callbacks the
2162 following configuration macros have to be defined. Currently this is
2163 architecture specific, so please check arch/your_architecture/lib/board.c
2164 typically in board_init_f() and board_init_r().
2166 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2167 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2168 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
2169 - CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2171 Configuration Settings:
2172 -----------------------
2174 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2175 Optionally it can be defined to support 64-bit memory commands.
2177 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2178 undefine this when you're short of memory.
2180 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2181 width of the commands listed in the 'help' command output.
2183 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
2184 prompt for user input.
2186 - CONFIG_SYS_CBSIZE: Buffer size for input from the Console
2188 - CONFIG_SYS_PBSIZE: Buffer size for Console output
2190 - CONFIG_SYS_MAXARGS: max. Number of arguments accepted for monitor commands
2192 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2193 the application (usually a Linux kernel) when it is
2196 - CONFIG_SYS_BAUDRATE_TABLE:
2197 List of legal baudrate settings for this board.
2199 - CONFIG_SYS_MEM_RESERVE_SECURE
2200 Only implemented for ARMv8 for now.
2201 If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2202 is substracted from total RAM and won't be reported to OS.
2203 This memory can be used as secure memory. A variable
2204 gd->arch.secure_ram is used to track the location. In systems
2205 the RAM base is not zero, or RAM is divided into banks,
2206 this variable needs to be recalcuated to get the address.
2208 - CONFIG_SYS_MEM_TOP_HIDE:
2209 If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2210 this specified memory area will get subtracted from the top
2211 (end) of RAM and won't get "touched" at all by U-Boot. By
2212 fixing up gd->ram_size the Linux kernel should gets passed
2213 the now "corrected" memory size and won't touch it either.
2214 This should work for arch/ppc and arch/powerpc. Only Linux
2215 board ports in arch/powerpc with bootwrapper support that
2216 recalculate the memory size from the SDRAM controller setup
2217 will have to get fixed in Linux additionally.
2219 This option can be used as a workaround for the 440EPx/GRx
2220 CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2223 WARNING: Please make sure that this value is a multiple of
2224 the Linux page size (normally 4k). If this is not the case,
2225 then the end address of the Linux memory will be located at a
2226 non page size aligned address and this could cause major
2229 - CONFIG_SYS_LOADS_BAUD_CHANGE:
2230 Enable temporary baudrate change while serial download
2232 - CONFIG_SYS_SDRAM_BASE:
2233 Physical start address of SDRAM. _Must_ be 0 here.
2235 - CONFIG_SYS_FLASH_BASE:
2236 Physical start address of Flash memory.
2238 - CONFIG_SYS_MONITOR_BASE:
2239 Physical start address of boot monitor code (set by
2240 make config files to be same as the text base address
2241 (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2242 CONFIG_SYS_FLASH_BASE when booting from flash.
2244 - CONFIG_SYS_MONITOR_LEN:
2245 Size of memory reserved for monitor code, used to
2246 determine _at_compile_time_ (!) if the environment is
2247 embedded within the U-Boot image, or in a separate
2250 - CONFIG_SYS_MALLOC_LEN:
2251 Size of DRAM reserved for malloc() use.
2253 - CONFIG_SYS_MALLOC_F_LEN
2254 Size of the malloc() pool for use before relocation. If
2255 this is defined, then a very simple malloc() implementation
2256 will become available before relocation. The address is just
2257 below the global data, and the stack is moved down to make
2260 This feature allocates regions with increasing addresses
2261 within the region. calloc() is supported, but realloc()
2262 is not available. free() is supported but does nothing.
2263 The memory will be freed (or in fact just forgotten) when
2264 U-Boot relocates itself.
2266 - CONFIG_SYS_MALLOC_SIMPLE
2267 Provides a simple and small malloc() and calloc() for those
2268 boards which do not use the full malloc in SPL (which is
2269 enabled with CONFIG_SYS_SPL_MALLOC_START).
2271 - CONFIG_SYS_NONCACHED_MEMORY:
2272 Size of non-cached memory area. This area of memory will be
2273 typically located right below the malloc() area and mapped
2274 uncached in the MMU. This is useful for drivers that would
2275 otherwise require a lot of explicit cache maintenance. For
2276 some drivers it's also impossible to properly maintain the
2277 cache. For example if the regions that need to be flushed
2278 are not a multiple of the cache-line size, *and* padding
2279 cannot be allocated between the regions to align them (i.e.
2280 if the HW requires a contiguous array of regions, and the
2281 size of each region is not cache-aligned), then a flush of
2282 one region may result in overwriting data that hardware has
2283 written to another region in the same cache-line. This can
2284 happen for example in network drivers where descriptors for
2285 buffers are typically smaller than the CPU cache-line (e.g.
2286 16 bytes vs. 32 or 64 bytes).
2288 Non-cached memory is only supported on 32-bit ARM at present.
2290 - CONFIG_SYS_BOOTM_LEN:
2291 Normally compressed uImages are limited to an
2292 uncompressed size of 8 MBytes. If this is not enough,
2293 you can define CONFIG_SYS_BOOTM_LEN in your board config file
2294 to adjust this setting to your needs.
2296 - CONFIG_SYS_BOOTMAPSZ:
2297 Maximum size of memory mapped by the startup code of
2298 the Linux kernel; all data that must be processed by
2299 the Linux kernel (bd_info, boot arguments, FDT blob if
2300 used) must be put below this limit, unless "bootm_low"
2301 environment variable is defined and non-zero. In such case
2302 all data for the Linux kernel must be between "bootm_low"
2303 and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
2304 variable "bootm_mapsize" will override the value of
2305 CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
2306 then the value in "bootm_size" will be used instead.
2308 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
2309 Enable initrd_high functionality. If defined then the
2310 initrd_high feature is enabled and the bootm ramdisk subcommand
2313 - CONFIG_SYS_BOOT_GET_CMDLINE:
2314 Enables allocating and saving kernel cmdline in space between
2315 "bootm_low" and "bootm_low" + BOOTMAPSZ.
2317 - CONFIG_SYS_BOOT_GET_KBD:
2318 Enables allocating and saving a kernel copy of the bd_info in
2319 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2321 - CONFIG_SYS_MAX_FLASH_BANKS:
2322 Max number of Flash memory banks
2324 - CONFIG_SYS_MAX_FLASH_SECT:
2325 Max number of sectors on a Flash chip
2327 - CONFIG_SYS_FLASH_ERASE_TOUT:
2328 Timeout for Flash erase operations (in ms)
2330 - CONFIG_SYS_FLASH_WRITE_TOUT:
2331 Timeout for Flash write operations (in ms)
2333 - CONFIG_SYS_FLASH_LOCK_TOUT
2334 Timeout for Flash set sector lock bit operation (in ms)
2336 - CONFIG_SYS_FLASH_UNLOCK_TOUT
2337 Timeout for Flash clear lock bits operation (in ms)
2339 - CONFIG_SYS_FLASH_PROTECTION
2340 If defined, hardware flash sectors protection is used
2341 instead of U-Boot software protection.
2343 - CONFIG_SYS_DIRECT_FLASH_TFTP:
2345 Enable TFTP transfers directly to flash memory;
2346 without this option such a download has to be
2347 performed in two steps: (1) download to RAM, and (2)
2348 copy from RAM to flash.
2350 The two-step approach is usually more reliable, since
2351 you can check if the download worked before you erase
2352 the flash, but in some situations (when system RAM is
2353 too limited to allow for a temporary copy of the
2354 downloaded image) this option may be very useful.
2356 - CONFIG_SYS_FLASH_CFI:
2357 Define if the flash driver uses extra elements in the
2358 common flash structure for storing flash geometry.
2360 - CONFIG_FLASH_CFI_DRIVER
2361 This option also enables the building of the cfi_flash driver
2362 in the drivers directory
2364 - CONFIG_FLASH_CFI_MTD
2365 This option enables the building of the cfi_mtd driver
2366 in the drivers directory. The driver exports CFI flash
2369 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2370 Use buffered writes to flash.
2372 - CONFIG_FLASH_SPANSION_S29WS_N
2373 s29ws-n MirrorBit flash has non-standard addresses for buffered
2376 - CONFIG_SYS_FLASH_QUIET_TEST
2377 If this option is defined, the common CFI flash doesn't
2378 print it's warning upon not recognized FLASH banks. This
2379 is useful, if some of the configured banks are only
2380 optionally available.
2382 - CONFIG_FLASH_SHOW_PROGRESS
2383 If defined (must be an integer), print out countdown
2384 digits and dots. Recommended value: 45 (9..1) for 80
2385 column displays, 15 (3..1) for 40 column displays.
2387 - CONFIG_FLASH_VERIFY
2388 If defined, the content of the flash (destination) is compared
2389 against the source after the write operation. An error message
2390 will be printed when the contents are not identical.
2391 Please note that this option is useless in nearly all cases,
2392 since such flash programming errors usually are detected earlier
2393 while unprotecting/erasing/programming. Please only enable
2394 this option if you really know what you are doing.
2396 - CONFIG_SYS_RX_ETH_BUFFER:
2397 Defines the number of Ethernet receive buffers. On some
2398 Ethernet controllers it is recommended to set this value
2399 to 8 or even higher (EEPRO100 or 405 EMAC), since all
2400 buffers can be full shortly after enabling the interface
2401 on high Ethernet traffic.
2402 Defaults to 4 if not defined.
2404 - CONFIG_ENV_MAX_ENTRIES
2406 Maximum number of entries in the hash table that is used
2407 internally to store the environment settings. The default
2408 setting is supposed to be generous and should work in most
2409 cases. This setting can be used to tune behaviour; see
2410 lib/hashtable.c for details.
2412 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2413 - CONFIG_ENV_FLAGS_LIST_STATIC
2414 Enable validation of the values given to environment variables when
2415 calling env set. Variables can be restricted to only decimal,
2416 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
2417 the variables can also be restricted to IP address or MAC address.
2419 The format of the list is:
2420 type_attribute = [s|d|x|b|i|m]
2421 access_attribute = [a|r|o|c]
2422 attributes = type_attribute[access_attribute]
2423 entry = variable_name[:attributes]
2426 The type attributes are:
2427 s - String (default)
2430 b - Boolean ([1yYtT|0nNfF])
2434 The access attributes are:
2440 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2441 Define this to a list (string) to define the ".flags"
2442 environment variable in the default or embedded environment.
2444 - CONFIG_ENV_FLAGS_LIST_STATIC
2445 Define this to a list (string) to define validation that
2446 should be done if an entry is not found in the ".flags"
2447 environment variable. To override a setting in the static
2448 list, simply add an entry for the same variable name to the
2451 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2452 regular expression. This allows multiple variables to define the same
2453 flags without explicitly listing them for each variable.
2455 The following definitions that deal with the placement and management
2456 of environment data (variable area); in general, we support the
2457 following configurations:
2459 - CONFIG_BUILD_ENVCRC:
2461 Builds up envcrc with the target environment so that external utils
2462 may easily extract it and embed it in final U-Boot images.
2464 BE CAREFUL! The first access to the environment happens quite early
2465 in U-Boot initialization (when we try to get the setting of for the
2466 console baudrate). You *MUST* have mapped your NVRAM area then, or
2469 Please note that even with NVRAM we still use a copy of the
2470 environment in RAM: we could work on NVRAM directly, but we want to
2471 keep settings there always unmodified except somebody uses "saveenv"
2472 to save the current settings.
2474 BE CAREFUL! For some special cases, the local device can not use
2475 "saveenv" command. For example, the local device will get the
2476 environment stored in a remote NOR flash by SRIO or PCIE link,
2477 but it can not erase, write this NOR flash by SRIO or PCIE interface.
2479 - CONFIG_NAND_ENV_DST
2481 Defines address in RAM to which the nand_spl code should copy the
2482 environment. If redundant environment is used, it will be copied to
2483 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2485 Please note that the environment is read-only until the monitor
2486 has been relocated to RAM and a RAM copy of the environment has been
2487 created; also, when using EEPROM you will have to use env_get_f()
2488 until then to read environment variables.
2490 The environment is protected by a CRC32 checksum. Before the monitor
2491 is relocated into RAM, as a result of a bad CRC you will be working
2492 with the compiled-in default environment - *silently*!!! [This is
2493 necessary, because the first environment variable we need is the
2494 "baudrate" setting for the console - if we have a bad CRC, we don't
2495 have any device yet where we could complain.]
2497 Note: once the monitor has been relocated, then it will complain if
2498 the default environment is used; a new CRC is computed as soon as you
2499 use the "saveenv" command to store a valid environment.
2501 - CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2502 Echo the inverted Ethernet link state to the fault LED.
2504 Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2505 also needs to be defined.
2507 - CONFIG_SYS_FAULT_MII_ADDR:
2508 MII address of the PHY to check for the Ethernet link state.
2510 - CONFIG_NS16550_MIN_FUNCTIONS:
2511 Define this if you desire to only have use of the NS16550_init
2512 and NS16550_putc functions for the serial driver located at
2513 drivers/serial/ns16550.c. This option is useful for saving
2514 space for already greatly restricted images, including but not
2515 limited to NAND_SPL configurations.
2517 - CONFIG_DISPLAY_BOARDINFO
2518 Display information about the board that U-Boot is running on
2519 when U-Boot starts up. The board function checkboard() is called
2522 - CONFIG_DISPLAY_BOARDINFO_LATE
2523 Similar to the previous option, but display this information
2524 later, once stdio is running and output goes to the LCD, if
2527 - CONFIG_BOARD_SIZE_LIMIT:
2528 Maximum size of the U-Boot image. When defined, the
2529 build system checks that the actual size does not
2532 Low Level (hardware related) configuration options:
2533 ---------------------------------------------------
2535 - CONFIG_SYS_CACHELINE_SIZE:
2536 Cache Line Size of the CPU.
2538 - CONFIG_SYS_CCSRBAR_DEFAULT:
2539 Default (power-on reset) physical address of CCSR on Freescale
2542 - CONFIG_SYS_CCSRBAR:
2543 Virtual address of CCSR. On a 32-bit build, this is typically
2544 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2546 - CONFIG_SYS_CCSRBAR_PHYS:
2547 Physical address of CCSR. CCSR can be relocated to a new
2548 physical address, if desired. In this case, this macro should
2549 be set to that address. Otherwise, it should be set to the
2550 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
2551 is typically relocated on 36-bit builds. It is recommended
2552 that this macro be defined via the _HIGH and _LOW macros:
2554 #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2555 * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2557 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2558 Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
2559 either 0 (32-bit build) or 0xF (36-bit build). This macro is
2560 used in assembly code, so it must not contain typecasts or
2561 integer size suffixes (e.g. "ULL").
2563 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
2564 Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
2565 used in assembly code, so it must not contain typecasts or
2566 integer size suffixes (e.g. "ULL").
2568 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2569 If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2570 forced to a value that ensures that CCSR is not relocated.
2573 Most IDE controllers were designed to be connected with PCI
2574 interface. Only few of them were designed for AHB interface.
2575 When software is doing ATA command and data transfer to
2576 IDE devices through IDE-AHB controller, some additional
2577 registers accessing to these kind of IDE-AHB controller
2580 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
2581 DO NOT CHANGE unless you know exactly what you're
2582 doing! (11-4) [MPC8xx systems only]
2584 - CONFIG_SYS_INIT_RAM_ADDR:
2586 Start address of memory area that can be used for
2587 initial data and stack; please note that this must be
2588 writable memory that is working WITHOUT special
2589 initialization, i. e. you CANNOT use normal RAM which
2590 will become available only after programming the
2591 memory controller and running certain initialization
2594 U-Boot uses the following memory types:
2595 - MPC8xx: IMMR (internal memory of the CPU)
2597 - CONFIG_SYS_GBL_DATA_OFFSET:
2599 Offset of the initial data structure in the memory
2600 area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2601 CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2602 data is located at the end of the available space
2603 (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2604 GENERATED_GBL_DATA_SIZE), and the initial stack is just
2605 below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2606 CONFIG_SYS_GBL_DATA_OFFSET) downward.
2609 On the MPC824X (or other systems that use the data
2610 cache for initial memory) the address chosen for
2611 CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2612 point to an otherwise UNUSED address space between
2613 the top of RAM and the start of the PCI space.
2615 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
2617 - CONFIG_SYS_OR_TIMING_SDRAM:
2620 - CONFIG_SYS_MAMR_PTA:
2621 periodic timer for refresh
2623 - FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2624 CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2625 CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2626 CONFIG_SYS_BR1_PRELIM:
2627 Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2629 - SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2630 CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2631 CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2632 Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2634 - CONFIG_PCI_INDIRECT_BRIDGE:
2635 Enable support for indirect PCI bridges.
2638 Chip has SRIO or not
2641 Board has SRIO 1 port available
2644 Board has SRIO 2 port available
2646 - CONFIG_SRIO_PCIE_BOOT_MASTER
2647 Board can support master function for Boot from SRIO and PCIE
2649 - CONFIG_SYS_SRIOn_MEM_VIRT:
2650 Virtual Address of SRIO port 'n' memory region
2652 - CONFIG_SYS_SRIOn_MEM_PHYxS:
2653 Physical Address of SRIO port 'n' memory region
2655 - CONFIG_SYS_SRIOn_MEM_SIZE:
2656 Size of SRIO port 'n' memory region
2658 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
2659 Defined to tell the NAND controller that the NAND chip is using
2661 Not all NAND drivers use this symbol.
2662 Example of drivers that use it:
2663 - drivers/mtd/nand/raw/ndfc.c
2664 - drivers/mtd/nand/raw/mxc_nand.c
2666 - CONFIG_SYS_NDFC_EBC0_CFG
2667 Sets the EBC0_CFG register for the NDFC. If not defined
2668 a default value will be used.
2671 Get DDR timing information from an I2C EEPROM. Common
2672 with pluggable memory modules such as SODIMMs
2675 I2C address of the SPD EEPROM
2677 - CONFIG_SYS_SPD_BUS_NUM
2678 If SPD EEPROM is on an I2C bus other than the first
2679 one, specify here. Note that the value must resolve
2680 to something your driver can deal with.
2682 - CONFIG_SYS_DDR_RAW_TIMING
2683 Get DDR timing information from other than SPD. Common with
2684 soldered DDR chips onboard without SPD. DDR raw timing
2685 parameters are extracted from datasheet and hard-coded into
2686 header files or board specific files.
2688 - CONFIG_FSL_DDR_INTERACTIVE
2689 Enable interactive DDR debugging. See doc/README.fsl-ddr.
2691 - CONFIG_FSL_DDR_SYNC_REFRESH
2692 Enable sync of refresh for multiple controllers.
2694 - CONFIG_FSL_DDR_BIST
2695 Enable built-in memory test for Freescale DDR controllers.
2697 - CONFIG_SYS_83XX_DDR_USES_CS0
2698 Only for 83xx systems. If specified, then DDR should
2699 be configured using CS0 and CS1 instead of CS2 and CS3.
2702 Enable RMII mode for all FECs.
2703 Note that this is a global option, we can't
2704 have one FEC in standard MII mode and another in RMII mode.
2706 - CONFIG_CRC32_VERIFY
2707 Add a verify option to the crc32 command.
2710 => crc32 -v <address> <count> <crc32>
2712 Where address/count indicate a memory area
2713 and crc32 is the correct crc32 which the
2717 Add the "loopw" memory command. This only takes effect if
2718 the memory commands are activated globally (CONFIG_CMD_MEMORY).
2720 - CONFIG_CMD_MX_CYCLIC
2721 Add the "mdc" and "mwc" memory commands. These are cyclic
2726 This command will print 4 bytes (10,11,12,13) each 500 ms.
2728 => mwc.l 100 12345678 10
2729 This command will write 12345678 to address 100 all 10 ms.
2731 This only takes effect if the memory commands are activated
2732 globally (CONFIG_CMD_MEMORY).
2735 Set when the currently-running compilation is for an artifact
2736 that will end up in the SPL (as opposed to the TPL or U-Boot
2737 proper). Code that needs stage-specific behavior should check
2741 Set when the currently-running compilation is for an artifact
2742 that will end up in the TPL (as opposed to the SPL or U-Boot
2743 proper). Code that needs stage-specific behavior should check
2746 - CONFIG_SYS_MPC85XX_NO_RESETVEC
2747 Only for 85xx systems. If this variable is specified, the section
2748 .resetvec is not kept and the section .bootpg is placed in the
2749 previous 4k of the .text section.
2751 - CONFIG_ARCH_MAP_SYSMEM
2752 Generally U-Boot (and in particular the md command) uses
2753 effective address. It is therefore not necessary to regard
2754 U-Boot address as virtual addresses that need to be translated
2755 to physical addresses. However, sandbox requires this, since
2756 it maintains its own little RAM buffer which contains all
2757 addressable memory. This option causes some memory accesses
2758 to be mapped through map_sysmem() / unmap_sysmem().
2760 - CONFIG_X86_RESET_VECTOR
2761 If defined, the x86 reset vector code is included. This is not
2762 needed when U-Boot is running from Coreboot.
2764 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
2765 Option to disable subpage write in NAND driver
2766 driver that uses this:
2767 drivers/mtd/nand/raw/davinci_nand.c
2769 Freescale QE/FMAN Firmware Support:
2770 -----------------------------------
2772 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
2773 loading of "firmware", which is encoded in the QE firmware binary format.
2774 This firmware often needs to be loaded during U-Boot booting, so macros
2775 are used to identify the storage device (NOR flash, SPI, etc) and the address
2778 - CONFIG_SYS_FMAN_FW_ADDR
2779 The address in the storage device where the FMAN microcode is located. The
2780 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2783 - CONFIG_SYS_QE_FW_ADDR
2784 The address in the storage device where the QE microcode is located. The
2785 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2788 - CONFIG_SYS_QE_FMAN_FW_LENGTH
2789 The maximum possible size of the firmware. The firmware binary format
2790 has a field that specifies the actual size of the firmware, but it
2791 might not be possible to read any part of the firmware unless some
2792 local storage is allocated to hold the entire firmware first.
2794 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
2795 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
2796 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
2797 virtual address in NOR flash.
2799 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
2800 Specifies that QE/FMAN firmware is located in NAND flash.
2801 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
2803 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
2804 Specifies that QE/FMAN firmware is located on the primary SD/MMC
2805 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
2807 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
2808 Specifies that QE/FMAN firmware is located in the remote (master)
2809 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
2810 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
2811 window->master inbound window->master LAW->the ucode address in
2812 master's memory space.
2814 Freescale Layerscape Management Complex Firmware Support:
2815 ---------------------------------------------------------
2816 The Freescale Layerscape Management Complex (MC) supports the loading of
2818 This firmware often needs to be loaded during U-Boot booting, so macros
2819 are used to identify the storage device (NOR flash, SPI, etc) and the address
2822 - CONFIG_FSL_MC_ENET
2823 Enable the MC driver for Layerscape SoCs.
2825 Freescale Layerscape Debug Server Support:
2826 -------------------------------------------
2827 The Freescale Layerscape Debug Server Support supports the loading of
2828 "Debug Server firmware" and triggering SP boot-rom.
2829 This firmware often needs to be loaded during U-Boot booting.
2831 - CONFIG_SYS_MC_RSV_MEM_ALIGN
2832 Define alignment of reserved memory MC requires
2837 In order to achieve reproducible builds, timestamps used in the U-Boot build
2838 process have to be set to a fixed value.
2840 This is done using the SOURCE_DATE_EPOCH environment variable.
2841 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
2842 option for U-Boot or an environment variable in U-Boot.
2844 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
2846 Building the Software:
2847 ======================
2849 Building U-Boot has been tested in several native build environments
2850 and in many different cross environments. Of course we cannot support
2851 all possibly existing versions of cross development tools in all
2852 (potentially obsolete) versions. In case of tool chain problems we
2853 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
2854 which is extensively used to build and test U-Boot.
2856 If you are not using a native environment, it is assumed that you
2857 have GNU cross compiling tools available in your path. In this case,
2858 you must set the environment variable CROSS_COMPILE in your shell.
2859 Note that no changes to the Makefile or any other source files are
2860 necessary. For example using the ELDK on a 4xx CPU, please enter:
2862 $ CROSS_COMPILE=ppc_4xx-
2863 $ export CROSS_COMPILE
2865 U-Boot is intended to be simple to build. After installing the
2866 sources you must configure U-Boot for one specific board type. This
2871 where "NAME_defconfig" is the name of one of the existing configu-
2872 rations; see configs/*_defconfig for supported names.
2874 Note: for some boards special configuration names may exist; check if
2875 additional information is available from the board vendor; for
2876 instance, the TQM823L systems are available without (standard)
2877 or with LCD support. You can select such additional "features"
2878 when choosing the configuration, i. e.
2880 make TQM823L_defconfig
2881 - will configure for a plain TQM823L, i. e. no LCD support
2883 make TQM823L_LCD_defconfig
2884 - will configure for a TQM823L with U-Boot console on LCD
2889 Finally, type "make all", and you should get some working U-Boot
2890 images ready for download to / installation on your system:
2892 - "u-boot.bin" is a raw binary image
2893 - "u-boot" is an image in ELF binary format
2894 - "u-boot.srec" is in Motorola S-Record format
2896 By default the build is performed locally and the objects are saved
2897 in the source directory. One of the two methods can be used to change
2898 this behavior and build U-Boot to some external directory:
2900 1. Add O= to the make command line invocations:
2902 make O=/tmp/build distclean
2903 make O=/tmp/build NAME_defconfig
2904 make O=/tmp/build all
2906 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
2908 export KBUILD_OUTPUT=/tmp/build
2913 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
2916 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
2917 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
2918 For example to treat all compiler warnings as errors:
2920 make KCFLAGS=-Werror
2922 Please be aware that the Makefiles assume you are using GNU make, so
2923 for instance on NetBSD you might need to use "gmake" instead of
2927 If the system board that you have is not listed, then you will need
2928 to port U-Boot to your hardware platform. To do this, follow these
2931 1. Create a new directory to hold your board specific code. Add any
2932 files you need. In your board directory, you will need at least
2933 the "Makefile" and a "<board>.c".
2934 2. Create a new configuration file "include/configs/<board>.h" for
2936 3. If you're porting U-Boot to a new CPU, then also create a new
2937 directory to hold your CPU specific code. Add any files you need.
2938 4. Run "make <board>_defconfig" with your new name.
2939 5. Type "make", and you should get a working "u-boot.srec" file
2940 to be installed on your target system.
2941 6. Debug and solve any problems that might arise.
2942 [Of course, this last step is much harder than it sounds.]
2945 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
2946 ==============================================================
2948 If you have modified U-Boot sources (for instance added a new board
2949 or support for new devices, a new CPU, etc.) you are expected to
2950 provide feedback to the other developers. The feedback normally takes
2951 the form of a "patch", i.e. a context diff against a certain (latest
2952 official or latest in the git repository) version of U-Boot sources.
2954 But before you submit such a patch, please verify that your modifi-
2955 cation did not break existing code. At least make sure that *ALL* of
2956 the supported boards compile WITHOUT ANY compiler warnings. To do so,
2957 just run the buildman script (tools/buildman/buildman), which will
2958 configure and build U-Boot for ALL supported system. Be warned, this
2959 will take a while. Please see the buildman README, or run 'buildman -H'
2963 See also "U-Boot Porting Guide" below.
2966 Monitor Commands - Overview:
2967 ============================
2969 go - start application at address 'addr'
2970 run - run commands in an environment variable
2971 bootm - boot application image from memory
2972 bootp - boot image via network using BootP/TFTP protocol
2973 bootz - boot zImage from memory
2974 tftpboot- boot image via network using TFTP protocol
2975 and env variables "ipaddr" and "serverip"
2976 (and eventually "gatewayip")
2977 tftpput - upload a file via network using TFTP protocol
2978 rarpboot- boot image via network using RARP/TFTP protocol
2979 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
2980 loads - load S-Record file over serial line
2981 loadb - load binary file over serial line (kermit mode)
2983 mm - memory modify (auto-incrementing)
2984 nm - memory modify (constant address)
2985 mw - memory write (fill)
2988 cmp - memory compare
2989 crc32 - checksum calculation
2990 i2c - I2C sub-system
2991 sspi - SPI utility commands
2992 base - print or set address offset
2993 printenv- print environment variables
2994 pwm - control pwm channels
2995 setenv - set environment variables
2996 saveenv - save environment variables to persistent storage
2997 protect - enable or disable FLASH write protection
2998 erase - erase FLASH memory
2999 flinfo - print FLASH memory information
3000 nand - NAND memory operations (see doc/README.nand)
3001 bdinfo - print Board Info structure
3002 iminfo - print header information for application image
3003 coninfo - print console devices and informations
3004 ide - IDE sub-system
3005 loop - infinite loop on address range
3006 loopw - infinite write loop on address range
3007 mtest - simple RAM test
3008 icache - enable or disable instruction cache
3009 dcache - enable or disable data cache
3010 reset - Perform RESET of the CPU
3011 echo - echo args to console
3012 version - print monitor version
3013 help - print online help
3014 ? - alias for 'help'
3017 Monitor Commands - Detailed Description:
3018 ========================================
3022 For now: just type "help <command>".
3025 Environment Variables:
3026 ======================
3028 U-Boot supports user configuration using Environment Variables which
3029 can be made persistent by saving to Flash memory.
3031 Environment Variables are set using "setenv", printed using
3032 "printenv", and saved to Flash using "saveenv". Using "setenv"
3033 without a value can be used to delete a variable from the
3034 environment. As long as you don't save the environment you are
3035 working with an in-memory copy. In case the Flash area containing the
3036 environment is erased by accident, a default environment is provided.
3038 Some configuration options can be set using Environment Variables.
3040 List of environment variables (most likely not complete):
3042 baudrate - see CONFIG_BAUDRATE
3044 bootdelay - see CONFIG_BOOTDELAY
3046 bootcmd - see CONFIG_BOOTCOMMAND
3048 bootargs - Boot arguments when booting an RTOS image
3050 bootfile - Name of the image to load with TFTP
3052 bootm_low - Memory range available for image processing in the bootm
3053 command can be restricted. This variable is given as
3054 a hexadecimal number and defines lowest address allowed
3055 for use by the bootm command. See also "bootm_size"
3056 environment variable. Address defined by "bootm_low" is
3057 also the base of the initial memory mapping for the Linux
3058 kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3061 bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3062 This variable is given as a hexadecimal number and it
3063 defines the size of the memory region starting at base
3064 address bootm_low that is accessible by the Linux kernel
3065 during early boot. If unset, CONFIG_SYS_BOOTMAPSZ is used
3066 as the default value if it is defined, and bootm_size is
3069 bootm_size - Memory range available for image processing in the bootm
3070 command can be restricted. This variable is given as
3071 a hexadecimal number and defines the size of the region
3072 allowed for use by the bootm command. See also "bootm_low"
3073 environment variable.
3075 bootstopkeysha256, bootdelaykey, bootstopkey - See README.autoboot
3077 updatefile - Location of the software update file on a TFTP server, used
3078 by the automatic software update feature. Please refer to
3079 documentation in doc/README.update for more details.
3081 autoload - if set to "no" (any string beginning with 'n'),
3082 "bootp" will just load perform a lookup of the
3083 configuration from the BOOTP server, but not try to
3084 load any image using TFTP
3086 autostart - if set to "yes", an image loaded using the "bootp",
3087 "rarpboot", "tftpboot" or "diskboot" commands will
3088 be automatically started (by internally calling
3091 If set to "no", a standalone image passed to the
3092 "bootm" command will be copied to the load address
3093 (and eventually uncompressed), but NOT be started.
3094 This can be used to load and uncompress arbitrary
3097 fdt_high - if set this restricts the maximum address that the
3098 flattened device tree will be copied into upon boot.
3099 For example, if you have a system with 1 GB memory
3100 at physical address 0x10000000, while Linux kernel
3101 only recognizes the first 704 MB as low memory, you
3102 may need to set fdt_high as 0x3C000000 to have the
3103 device tree blob be copied to the maximum address
3104 of the 704 MB low memory, so that Linux kernel can
3105 access it during the boot procedure.
3107 If this is set to the special value 0xFFFFFFFF then
3108 the fdt will not be copied at all on boot. For this
3109 to work it must reside in writable memory, have
3110 sufficient padding on the end of it for u-boot to
3111 add the information it needs into it, and the memory
3112 must be accessible by the kernel.
3114 fdtcontroladdr- if set this is the address of the control flattened
3115 device tree used by U-Boot when CONFIG_OF_CONTROL is
3118 i2cfast - (PPC405GP|PPC405EP only)
3119 if set to 'y' configures Linux I2C driver for fast
3120 mode (400kHZ). This environment variable is used in
3121 initialization code. So, for changes to be effective
3122 it must be saved and board must be reset.
3124 initrd_high - restrict positioning of initrd images:
3125 If this variable is not set, initrd images will be
3126 copied to the highest possible address in RAM; this
3127 is usually what you want since it allows for
3128 maximum initrd size. If for some reason you want to
3129 make sure that the initrd image is loaded below the
3130 CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3131 variable to a value of "no" or "off" or "0".
3132 Alternatively, you can set it to a maximum upper
3133 address to use (U-Boot will still check that it
3134 does not overwrite the U-Boot stack and data).
3136 For instance, when you have a system with 16 MB
3137 RAM, and want to reserve 4 MB from use by Linux,
3138 you can do this by adding "mem=12M" to the value of
3139 the "bootargs" variable. However, now you must make
3140 sure that the initrd image is placed in the first
3141 12 MB as well - this can be done with
3143 setenv initrd_high 00c00000
3145 If you set initrd_high to 0xFFFFFFFF, this is an
3146 indication to U-Boot that all addresses are legal
3147 for the Linux kernel, including addresses in flash
3148 memory. In this case U-Boot will NOT COPY the
3149 ramdisk at all. This may be useful to reduce the
3150 boot time on your system, but requires that this
3151 feature is supported by your Linux kernel.
3153 ipaddr - IP address; needed for tftpboot command
3155 loadaddr - Default load address for commands like "bootp",
3156 "rarpboot", "tftpboot", "loadb" or "diskboot"
3158 loads_echo - see CONFIG_LOADS_ECHO
3160 serverip - TFTP server IP address; needed for tftpboot command
3162 bootretry - see CONFIG_BOOT_RETRY_TIME
3164 bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR
3166 bootstopkey - see CONFIG_AUTOBOOT_STOP_STR
3168 ethprime - controls which interface is used first.
3170 ethact - controls which interface is currently active.
3171 For example you can do the following
3173 => setenv ethact FEC
3174 => ping 192.168.0.1 # traffic sent on FEC
3175 => setenv ethact SCC
3176 => ping 10.0.0.1 # traffic sent on SCC
3178 ethrotate - When set to "no" U-Boot does not go through all
3179 available network interfaces.
3180 It just stays at the currently selected interface.
3182 netretry - When set to "no" each network operation will
3183 either succeed or fail without retrying.
3184 When set to "once" the network operation will
3185 fail when all the available network interfaces
3186 are tried once without success.
3187 Useful on scripts which control the retry operation
3190 npe_ucode - set load address for the NPE microcode
3192 silent_linux - If set then Linux will be told to boot silently, by
3193 changing the console to be empty. If "yes" it will be
3194 made silent. If "no" it will not be made silent. If
3195 unset, then it will be made silent if the U-Boot console
3198 tftpsrcp - If this is set, the value is used for TFTP's
3201 tftpdstp - If this is set, the value is used for TFTP's UDP
3202 destination port instead of the Well Know Port 69.
3204 tftpblocksize - Block size to use for TFTP transfers; if not set,
3205 we use the TFTP server's default block size
3207 tftptimeout - Retransmission timeout for TFTP packets (in milli-
3208 seconds, minimum value is 1000 = 1 second). Defines
3209 when a packet is considered to be lost so it has to
3210 be retransmitted. The default is 5000 = 5 seconds.
3211 Lowering this value may make downloads succeed
3212 faster in networks with high packet loss rates or
3213 with unreliable TFTP servers.
3215 tftptimeoutcountmax - maximum count of TFTP timeouts (no
3216 unit, minimum value = 0). Defines how many timeouts
3217 can happen during a single file transfer before that
3218 transfer is aborted. The default is 10, and 0 means
3219 'no timeouts allowed'. Increasing this value may help
3220 downloads succeed with high packet loss rates, or with
3221 unreliable TFTP servers or client hardware.
3223 tftpwindowsize - if this is set, the value is used for TFTP's
3224 window size as described by RFC 7440.
3225 This means the count of blocks we can receive before
3226 sending ack to server.
3228 vlan - When set to a value < 4095 the traffic over
3229 Ethernet is encapsulated/received over 802.1q
3232 bootpretryperiod - Period during which BOOTP/DHCP sends retries.
3233 Unsigned value, in milliseconds. If not set, the period will
3234 be either the default (28000), or a value based on
3235 CONFIG_NET_RETRY_COUNT, if defined. This value has
3236 precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3238 memmatches - Number of matches found by the last 'ms' command, in hex
3240 memaddr - Address of the last match found by the 'ms' command, in hex,
3243 mempos - Index position of the last match found by the 'ms' command,
3244 in units of the size (.b, .w, .l) of the search
3246 zbootbase - (x86 only) Base address of the bzImage 'setup' block
3248 zbootaddr - (x86 only) Address of the loaded bzImage, typically
3249 BZIMAGE_LOAD_ADDR which is 0x100000
3251 The following image location variables contain the location of images
3252 used in booting. The "Image" column gives the role of the image and is
3253 not an environment variable name. The other columns are environment
3254 variable names. "File Name" gives the name of the file on a TFTP
3255 server, "RAM Address" gives the location in RAM the image will be
3256 loaded to, and "Flash Location" gives the image's address in NOR
3257 flash or offset in NAND flash.
3259 *Note* - these variables don't have to be defined for all boards, some
3260 boards currently use other variables for these purposes, and some
3261 boards use these variables for other purposes.
3263 Image File Name RAM Address Flash Location
3264 ----- --------- ----------- --------------
3265 u-boot u-boot u-boot_addr_r u-boot_addr
3266 Linux kernel bootfile kernel_addr_r kernel_addr
3267 device tree blob fdtfile fdt_addr_r fdt_addr
3268 ramdisk ramdiskfile ramdisk_addr_r ramdisk_addr
3270 The following environment variables may be used and automatically
3271 updated by the network boot commands ("bootp" and "rarpboot"),
3272 depending the information provided by your boot server:
3274 bootfile - see above
3275 dnsip - IP address of your Domain Name Server
3276 dnsip2 - IP address of your secondary Domain Name Server
3277 gatewayip - IP address of the Gateway (Router) to use
3278 hostname - Target hostname
3280 netmask - Subnet Mask
3281 rootpath - Pathname of the root filesystem on the NFS server
3282 serverip - see above
3285 There are two special Environment Variables:
3287 serial# - contains hardware identification information such
3288 as type string and/or serial number
3289 ethaddr - Ethernet address
3291 These variables can be set only once (usually during manufacturing of
3292 the board). U-Boot refuses to delete or overwrite these variables
3293 once they have been set once.
3296 Further special Environment Variables:
3298 ver - Contains the U-Boot version string as printed
3299 with the "version" command. This variable is
3300 readonly (see CONFIG_VERSION_VARIABLE).
3303 Please note that changes to some configuration parameters may take
3304 only effect after the next boot (yes, that's just like Windoze :-).
3307 Callback functions for environment variables:
3308 ---------------------------------------------
3310 For some environment variables, the behavior of u-boot needs to change
3311 when their values are changed. This functionality allows functions to
3312 be associated with arbitrary variables. On creation, overwrite, or
3313 deletion, the callback will provide the opportunity for some side
3314 effect to happen or for the change to be rejected.
3316 The callbacks are named and associated with a function using the
3317 U_BOOT_ENV_CALLBACK macro in your board or driver code.
3319 These callbacks are associated with variables in one of two ways. The
3320 static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3321 in the board configuration to a string that defines a list of
3322 associations. The list must be in the following format:
3324 entry = variable_name[:callback_name]
3327 If the callback name is not specified, then the callback is deleted.
3328 Spaces are also allowed anywhere in the list.
3330 Callbacks can also be associated by defining the ".callbacks" variable
3331 with the same list format above. Any association in ".callbacks" will
3332 override any association in the static list. You can define
3333 CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3334 ".callbacks" environment variable in the default or embedded environment.
3336 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3337 regular expression. This allows multiple variables to be connected to
3338 the same callback without explicitly listing them all out.
3340 The signature of the callback functions is:
3342 int callback(const char *name, const char *value, enum env_op op, int flags)
3344 * name - changed environment variable
3345 * value - new value of the environment variable
3346 * op - operation (create, overwrite, or delete)
3347 * flags - attributes of the environment variable change, see flags H_* in
3350 The return value is 0 if the variable change is accepted and 1 otherwise.
3353 Note for Redundant Ethernet Interfaces:
3354 =======================================
3356 Some boards come with redundant Ethernet interfaces; U-Boot supports
3357 such configurations and is capable of automatic selection of a
3358 "working" interface when needed. MAC assignment works as follows:
3360 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3361 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3362 "eth1addr" (=>eth1), "eth2addr", ...
3364 If the network interface stores some valid MAC address (for instance
3365 in SROM), this is used as default address if there is NO correspon-
3366 ding setting in the environment; if the corresponding environment
3367 variable is set, this overrides the settings in the card; that means:
3369 o If the SROM has a valid MAC address, and there is no address in the
3370 environment, the SROM's address is used.
3372 o If there is no valid address in the SROM, and a definition in the
3373 environment exists, then the value from the environment variable is
3376 o If both the SROM and the environment contain a MAC address, and
3377 both addresses are the same, this MAC address is used.
3379 o If both the SROM and the environment contain a MAC address, and the
3380 addresses differ, the value from the environment is used and a
3383 o If neither SROM nor the environment contain a MAC address, an error
3384 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3385 a random, locally-assigned MAC is used.
3387 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3388 will be programmed into hardware as part of the initialization process. This
3389 may be skipped by setting the appropriate 'ethmacskip' environment variable.
3390 The naming convention is as follows:
3391 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3396 U-Boot is capable of booting (and performing other auxiliary operations on)
3397 images in two formats:
3399 New uImage format (FIT)
3400 -----------------------
3402 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3403 to Flattened Device Tree). It allows the use of images with multiple
3404 components (several kernels, ramdisks, etc.), with contents protected by
3405 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3411 Old image format is based on binary files which can be basically anything,
3412 preceded by a special header; see the definitions in include/image.h for
3413 details; basically, the header defines the following image properties:
3415 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3416 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3417 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3418 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3420 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3421 IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3422 Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3423 * Compression Type (uncompressed, gzip, bzip2)
3429 The header is marked by a special Magic Number, and both the header
3430 and the data portions of the image are secured against corruption by
3437 Although U-Boot should support any OS or standalone application
3438 easily, the main focus has always been on Linux during the design of
3441 U-Boot includes many features that so far have been part of some
3442 special "boot loader" code within the Linux kernel. Also, any
3443 "initrd" images to be used are no longer part of one big Linux image;
3444 instead, kernel and "initrd" are separate images. This implementation
3445 serves several purposes:
3447 - the same features can be used for other OS or standalone
3448 applications (for instance: using compressed images to reduce the
3449 Flash memory footprint)
3451 - it becomes much easier to port new Linux kernel versions because
3452 lots of low-level, hardware dependent stuff are done by U-Boot
3454 - the same Linux kernel image can now be used with different "initrd"
3455 images; of course this also means that different kernel images can
3456 be run with the same "initrd". This makes testing easier (you don't
3457 have to build a new "zImage.initrd" Linux image when you just
3458 change a file in your "initrd"). Also, a field-upgrade of the
3459 software is easier now.
3465 Porting Linux to U-Boot based systems:
3466 ---------------------------------------
3468 U-Boot cannot save you from doing all the necessary modifications to
3469 configure the Linux device drivers for use with your target hardware
3470 (no, we don't intend to provide a full virtual machine interface to
3473 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3475 Just make sure your machine specific header file (for instance
3476 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3477 Information structure as we define in include/asm-<arch>/u-boot.h,
3478 and make sure that your definition of IMAP_ADDR uses the same value
3479 as your U-Boot configuration in CONFIG_SYS_IMMR.
3481 Note that U-Boot now has a driver model, a unified model for drivers.
3482 If you are adding a new driver, plumb it into driver model. If there
3483 is no uclass available, you are encouraged to create one. See
3487 Configuring the Linux kernel:
3488 -----------------------------
3490 No specific requirements for U-Boot. Make sure you have some root
3491 device (initial ramdisk, NFS) for your target system.
3494 Building a Linux Image:
3495 -----------------------
3497 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3498 not used. If you use recent kernel source, a new build target
3499 "uImage" will exist which automatically builds an image usable by
3500 U-Boot. Most older kernels also have support for a "pImage" target,
3501 which was introduced for our predecessor project PPCBoot and uses a
3502 100% compatible format.
3506 make TQM850L_defconfig
3511 The "uImage" build target uses a special tool (in 'tools/mkimage') to
3512 encapsulate a compressed Linux kernel image with header information,
3513 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3515 * build a standard "vmlinux" kernel image (in ELF binary format):
3517 * convert the kernel into a raw binary image:
3519 ${CROSS_COMPILE}-objcopy -O binary \
3520 -R .note -R .comment \
3521 -S vmlinux linux.bin
3523 * compress the binary image:
3527 * package compressed binary image for U-Boot:
3529 mkimage -A ppc -O linux -T kernel -C gzip \
3530 -a 0 -e 0 -n "Linux Kernel Image" \
3531 -d linux.bin.gz uImage
3534 The "mkimage" tool can also be used to create ramdisk images for use
3535 with U-Boot, either separated from the Linux kernel image, or
3536 combined into one file. "mkimage" encapsulates the images with a 64
3537 byte header containing information about target architecture,
3538 operating system, image type, compression method, entry points, time
3539 stamp, CRC32 checksums, etc.
3541 "mkimage" can be called in two ways: to verify existing images and
3542 print the header information, or to build new images.
3544 In the first form (with "-l" option) mkimage lists the information
3545 contained in the header of an existing U-Boot image; this includes
3546 checksum verification:
3548 tools/mkimage -l image
3549 -l ==> list image header information
3551 The second form (with "-d" option) is used to build a U-Boot image
3552 from a "data file" which is used as image payload:
3554 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3555 -n name -d data_file image
3556 -A ==> set architecture to 'arch'
3557 -O ==> set operating system to 'os'
3558 -T ==> set image type to 'type'
3559 -C ==> set compression type 'comp'
3560 -a ==> set load address to 'addr' (hex)
3561 -e ==> set entry point to 'ep' (hex)
3562 -n ==> set image name to 'name'
3563 -d ==> use image data from 'datafile'
3565 Right now, all Linux kernels for PowerPC systems use the same load
3566 address (0x00000000), but the entry point address depends on the
3569 - 2.2.x kernels have the entry point at 0x0000000C,
3570 - 2.3.x and later kernels have the entry point at 0x00000000.
3572 So a typical call to build a U-Boot image would read:
3574 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3575 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3576 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3577 > examples/uImage.TQM850L
3578 Image Name: 2.4.4 kernel for TQM850L
3579 Created: Wed Jul 19 02:34:59 2000
3580 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3581 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3582 Load Address: 0x00000000
3583 Entry Point: 0x00000000
3585 To verify the contents of the image (or check for corruption):
3587 -> tools/mkimage -l examples/uImage.TQM850L
3588 Image Name: 2.4.4 kernel for TQM850L
3589 Created: Wed Jul 19 02:34:59 2000
3590 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3591 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
3592 Load Address: 0x00000000
3593 Entry Point: 0x00000000
3595 NOTE: for embedded systems where boot time is critical you can trade
3596 speed for memory and install an UNCOMPRESSED image instead: this
3597 needs more space in Flash, but boots much faster since it does not
3598 need to be uncompressed:
3600 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3601 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3602 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3603 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3604 > examples/uImage.TQM850L-uncompressed
3605 Image Name: 2.4.4 kernel for TQM850L
3606 Created: Wed Jul 19 02:34:59 2000
3607 Image Type: PowerPC Linux Kernel Image (uncompressed)
3608 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
3609 Load Address: 0x00000000
3610 Entry Point: 0x00000000
3613 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3614 when your kernel is intended to use an initial ramdisk:
3616 -> tools/mkimage -n 'Simple Ramdisk Image' \
3617 > -A ppc -O linux -T ramdisk -C gzip \
3618 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3619 Image Name: Simple Ramdisk Image
3620 Created: Wed Jan 12 14:01:50 2000
3621 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3622 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
3623 Load Address: 0x00000000
3624 Entry Point: 0x00000000
3626 The "dumpimage" tool can be used to disassemble or list the contents of images
3627 built by mkimage. See dumpimage's help output (-h) for details.
3629 Installing a Linux Image:
3630 -------------------------
3632 To downloading a U-Boot image over the serial (console) interface,
3633 you must convert the image to S-Record format:
3635 objcopy -I binary -O srec examples/image examples/image.srec
3637 The 'objcopy' does not understand the information in the U-Boot
3638 image header, so the resulting S-Record file will be relative to
3639 address 0x00000000. To load it to a given address, you need to
3640 specify the target address as 'offset' parameter with the 'loads'
3643 Example: install the image to address 0x40100000 (which on the
3644 TQM8xxL is in the first Flash bank):
3646 => erase 40100000 401FFFFF
3652 ## Ready for S-Record download ...
3653 ~>examples/image.srec
3654 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3656 15989 15990 15991 15992
3657 [file transfer complete]
3659 ## Start Addr = 0x00000000
3662 You can check the success of the download using the 'iminfo' command;
3663 this includes a checksum verification so you can be sure no data
3664 corruption happened:
3668 ## Checking Image at 40100000 ...
3669 Image Name: 2.2.13 for initrd on TQM850L
3670 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3671 Data Size: 335725 Bytes = 327 kB = 0 MB
3672 Load Address: 00000000
3673 Entry Point: 0000000c
3674 Verifying Checksum ... OK
3680 The "bootm" command is used to boot an application that is stored in
3681 memory (RAM or Flash). In case of a Linux kernel image, the contents
3682 of the "bootargs" environment variable is passed to the kernel as
3683 parameters. You can check and modify this variable using the
3684 "printenv" and "setenv" commands:
3687 => printenv bootargs
3688 bootargs=root=/dev/ram
3690 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3692 => printenv bootargs
3693 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3696 ## Booting Linux kernel at 40020000 ...
3697 Image Name: 2.2.13 for NFS on TQM850L
3698 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3699 Data Size: 381681 Bytes = 372 kB = 0 MB
3700 Load Address: 00000000
3701 Entry Point: 0000000c
3702 Verifying Checksum ... OK
3703 Uncompressing Kernel Image ... OK
3704 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
3705 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3706 time_init: decrementer frequency = 187500000/60
3707 Calibrating delay loop... 49.77 BogoMIPS
3708 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3711 If you want to boot a Linux kernel with initial RAM disk, you pass
3712 the memory addresses of both the kernel and the initrd image (PPBCOOT
3713 format!) to the "bootm" command:
3715 => imi 40100000 40200000
3717 ## Checking Image at 40100000 ...
3718 Image Name: 2.2.13 for initrd on TQM850L
3719 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3720 Data Size: 335725 Bytes = 327 kB = 0 MB
3721 Load Address: 00000000
3722 Entry Point: 0000000c
3723 Verifying Checksum ... OK
3725 ## Checking Image at 40200000 ...
3726 Image Name: Simple Ramdisk Image
3727 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3728 Data Size: 566530 Bytes = 553 kB = 0 MB
3729 Load Address: 00000000
3730 Entry Point: 00000000
3731 Verifying Checksum ... OK
3733 => bootm 40100000 40200000
3734 ## Booting Linux kernel at 40100000 ...
3735 Image Name: 2.2.13 for initrd on TQM850L
3736 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3737 Data Size: 335725 Bytes = 327 kB = 0 MB
3738 Load Address: 00000000
3739 Entry Point: 0000000c
3740 Verifying Checksum ... OK
3741 Uncompressing Kernel Image ... OK
3742 ## Loading RAMDisk Image at 40200000 ...
3743 Image Name: Simple Ramdisk Image
3744 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3745 Data Size: 566530 Bytes = 553 kB = 0 MB
3746 Load Address: 00000000
3747 Entry Point: 00000000
3748 Verifying Checksum ... OK
3749 Loading Ramdisk ... OK
3750 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
3751 Boot arguments: root=/dev/ram
3752 time_init: decrementer frequency = 187500000/60
3753 Calibrating delay loop... 49.77 BogoMIPS
3755 RAMDISK: Compressed image found at block 0
3756 VFS: Mounted root (ext2 filesystem).
3760 Boot Linux and pass a flat device tree:
3763 First, U-Boot must be compiled with the appropriate defines. See the section
3764 titled "Linux Kernel Interface" above for a more in depth explanation. The
3765 following is an example of how to start a kernel and pass an updated
3771 oft=oftrees/mpc8540ads.dtb
3772 => tftp $oftaddr $oft
3773 Speed: 1000, full duplex
3775 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
3776 Filename 'oftrees/mpc8540ads.dtb'.
3777 Load address: 0x300000
3780 Bytes transferred = 4106 (100a hex)
3781 => tftp $loadaddr $bootfile
3782 Speed: 1000, full duplex
3784 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
3786 Load address: 0x200000
3787 Loading:############
3789 Bytes transferred = 1029407 (fb51f hex)
3794 => bootm $loadaddr - $oftaddr
3795 ## Booting image at 00200000 ...
3796 Image Name: Linux-2.6.17-dirty
3797 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3798 Data Size: 1029343 Bytes = 1005.2 kB
3799 Load Address: 00000000
3800 Entry Point: 00000000
3801 Verifying Checksum ... OK
3802 Uncompressing Kernel Image ... OK
3803 Booting using flat device tree at 0x300000
3804 Using MPC85xx ADS machine description
3805 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
3809 More About U-Boot Image Types:
3810 ------------------------------
3812 U-Boot supports the following image types:
3814 "Standalone Programs" are directly runnable in the environment
3815 provided by U-Boot; it is expected that (if they behave
3816 well) you can continue to work in U-Boot after return from
3817 the Standalone Program.
3818 "OS Kernel Images" are usually images of some Embedded OS which
3819 will take over control completely. Usually these programs
3820 will install their own set of exception handlers, device
3821 drivers, set up the MMU, etc. - this means, that you cannot
3822 expect to re-enter U-Boot except by resetting the CPU.
3823 "RAMDisk Images" are more or less just data blocks, and their
3824 parameters (address, size) are passed to an OS kernel that is
3826 "Multi-File Images" contain several images, typically an OS
3827 (Linux) kernel image and one or more data images like
3828 RAMDisks. This construct is useful for instance when you want
3829 to boot over the network using BOOTP etc., where the boot
3830 server provides just a single image file, but you want to get
3831 for instance an OS kernel and a RAMDisk image.
3833 "Multi-File Images" start with a list of image sizes, each
3834 image size (in bytes) specified by an "uint32_t" in network
3835 byte order. This list is terminated by an "(uint32_t)0".
3836 Immediately after the terminating 0 follow the images, one by
3837 one, all aligned on "uint32_t" boundaries (size rounded up to
3838 a multiple of 4 bytes).
3840 "Firmware Images" are binary images containing firmware (like
3841 U-Boot or FPGA images) which usually will be programmed to
3844 "Script files" are command sequences that will be executed by
3845 U-Boot's command interpreter; this feature is especially
3846 useful when you configure U-Boot to use a real shell (hush)
3847 as command interpreter.
3849 Booting the Linux zImage:
3850 -------------------------
3852 On some platforms, it's possible to boot Linux zImage. This is done
3853 using the "bootz" command. The syntax of "bootz" command is the same
3854 as the syntax of "bootm" command.
3856 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
3857 kernel with raw initrd images. The syntax is slightly different, the
3858 address of the initrd must be augmented by it's size, in the following
3859 format: "<initrd addres>:<initrd size>".
3865 One of the features of U-Boot is that you can dynamically load and
3866 run "standalone" applications, which can use some resources of
3867 U-Boot like console I/O functions or interrupt services.
3869 Two simple examples are included with the sources:
3874 'examples/hello_world.c' contains a small "Hello World" Demo
3875 application; it is automatically compiled when you build U-Boot.
3876 It's configured to run at address 0x00040004, so you can play with it
3880 ## Ready for S-Record download ...
3881 ~>examples/hello_world.srec
3882 1 2 3 4 5 6 7 8 9 10 11 ...
3883 [file transfer complete]
3885 ## Start Addr = 0x00040004
3887 => go 40004 Hello World! This is a test.
3888 ## Starting application at 0x00040004 ...
3899 Hit any key to exit ...
3901 ## Application terminated, rc = 0x0
3903 Another example, which demonstrates how to register a CPM interrupt
3904 handler with the U-Boot code, can be found in 'examples/timer.c'.
3905 Here, a CPM timer is set up to generate an interrupt every second.
3906 The interrupt service routine is trivial, just printing a '.'
3907 character, but this is just a demo program. The application can be
3908 controlled by the following keys:
3910 ? - print current values og the CPM Timer registers
3911 b - enable interrupts and start timer
3912 e - stop timer and disable interrupts
3913 q - quit application
3916 ## Ready for S-Record download ...
3917 ~>examples/timer.srec
3918 1 2 3 4 5 6 7 8 9 10 11 ...
3919 [file transfer complete]
3921 ## Start Addr = 0x00040004
3924 ## Starting application at 0x00040004 ...
3927 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
3930 [q, b, e, ?] Set interval 1000000 us
3933 [q, b, e, ?] ........
3934 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
3937 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
3940 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
3943 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
3945 [q, b, e, ?] ...Stopping timer
3947 [q, b, e, ?] ## Application terminated, rc = 0x0
3953 Over time, many people have reported problems when trying to use the
3954 "minicom" terminal emulation program for serial download. I (wd)
3955 consider minicom to be broken, and recommend not to use it. Under
3956 Unix, I recommend to use C-Kermit for general purpose use (and
3957 especially for kermit binary protocol download ("loadb" command), and
3958 use "cu" for S-Record download ("loads" command). See
3959 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
3960 for help with kermit.
3963 Nevertheless, if you absolutely want to use it try adding this
3964 configuration to your "File transfer protocols" section:
3966 Name Program Name U/D FullScr IO-Red. Multi
3967 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
3968 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
3974 Starting at version 0.9.2, U-Boot supports NetBSD both as host
3975 (build U-Boot) and target system (boots NetBSD/mpc8xx).
3977 Building requires a cross environment; it is known to work on
3978 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
3979 need gmake since the Makefiles are not compatible with BSD make).
3980 Note that the cross-powerpc package does not install include files;
3981 attempting to build U-Boot will fail because <machine/ansi.h> is
3982 missing. This file has to be installed and patched manually:
3984 # cd /usr/pkg/cross/powerpc-netbsd/include
3986 # ln -s powerpc machine
3987 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
3988 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
3990 Native builds *don't* work due to incompatibilities between native
3991 and U-Boot include files.
3993 Booting assumes that (the first part of) the image booted is a
3994 stage-2 loader which in turn loads and then invokes the kernel
3995 proper. Loader sources will eventually appear in the NetBSD source
3996 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
3997 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4000 Implementation Internals:
4001 =========================
4003 The following is not intended to be a complete description of every
4004 implementation detail. However, it should help to understand the
4005 inner workings of U-Boot and make it easier to port it to custom
4009 Initial Stack, Global Data:
4010 ---------------------------
4012 The implementation of U-Boot is complicated by the fact that U-Boot
4013 starts running out of ROM (flash memory), usually without access to
4014 system RAM (because the memory controller is not initialized yet).
4015 This means that we don't have writable Data or BSS segments, and BSS
4016 is not initialized as zero. To be able to get a C environment working
4017 at all, we have to allocate at least a minimal stack. Implementation
4018 options for this are defined and restricted by the CPU used: Some CPU
4019 models provide on-chip memory (like the IMMR area on MPC8xx and
4020 MPC826x processors), on others (parts of) the data cache can be
4021 locked as (mis-) used as memory, etc.
4023 Chris Hallinan posted a good summary of these issues to the
4024 U-Boot mailing list:
4026 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4027 From: "Chris Hallinan" <clh@net1plus.com>
4028 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4031 Correct me if I'm wrong, folks, but the way I understand it
4032 is this: Using DCACHE as initial RAM for Stack, etc, does not
4033 require any physical RAM backing up the cache. The cleverness
4034 is that the cache is being used as a temporary supply of
4035 necessary storage before the SDRAM controller is setup. It's
4036 beyond the scope of this list to explain the details, but you
4037 can see how this works by studying the cache architecture and
4038 operation in the architecture and processor-specific manuals.
4040 OCM is On Chip Memory, which I believe the 405GP has 4K. It
4041 is another option for the system designer to use as an
4042 initial stack/RAM area prior to SDRAM being available. Either
4043 option should work for you. Using CS 4 should be fine if your
4044 board designers haven't used it for something that would
4045 cause you grief during the initial boot! It is frequently not
4048 CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4049 with your processor/board/system design. The default value
4050 you will find in any recent u-boot distribution in
4051 walnut.h should work for you. I'd set it to a value larger
4052 than your SDRAM module. If you have a 64MB SDRAM module, set
4053 it above 400_0000. Just make sure your board has no resources
4054 that are supposed to respond to that address! That code in
4055 start.S has been around a while and should work as is when
4056 you get the config right.
4061 It is essential to remember this, since it has some impact on the C
4062 code for the initialization procedures:
4064 * Initialized global data (data segment) is read-only. Do not attempt
4067 * Do not use any uninitialized global data (or implicitly initialized
4068 as zero data - BSS segment) at all - this is undefined, initiali-
4069 zation is performed later (when relocating to RAM).
4071 * Stack space is very limited. Avoid big data buffers or things like
4074 Having only the stack as writable memory limits means we cannot use
4075 normal global data to share information between the code. But it
4076 turned out that the implementation of U-Boot can be greatly
4077 simplified by making a global data structure (gd_t) available to all
4078 functions. We could pass a pointer to this data as argument to _all_
4079 functions, but this would bloat the code. Instead we use a feature of
4080 the GCC compiler (Global Register Variables) to share the data: we
4081 place a pointer (gd) to the global data into a register which we
4082 reserve for this purpose.
4084 When choosing a register for such a purpose we are restricted by the
4085 relevant (E)ABI specifications for the current architecture, and by
4086 GCC's implementation.
4088 For PowerPC, the following registers have specific use:
4090 R2: reserved for system use
4091 R3-R4: parameter passing and return values
4092 R5-R10: parameter passing
4093 R13: small data area pointer
4097 (U-Boot also uses R12 as internal GOT pointer. r12
4098 is a volatile register so r12 needs to be reset when
4099 going back and forth between asm and C)
4101 ==> U-Boot will use R2 to hold a pointer to the global data
4103 Note: on PPC, we could use a static initializer (since the
4104 address of the global data structure is known at compile time),
4105 but it turned out that reserving a register results in somewhat
4106 smaller code - although the code savings are not that big (on
4107 average for all boards 752 bytes for the whole U-Boot image,
4108 624 text + 127 data).
4110 On ARM, the following registers are used:
4112 R0: function argument word/integer result
4113 R1-R3: function argument word
4114 R9: platform specific
4115 R10: stack limit (used only if stack checking is enabled)
4116 R11: argument (frame) pointer
4117 R12: temporary workspace
4120 R15: program counter
4122 ==> U-Boot will use R9 to hold a pointer to the global data
4124 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4126 On Nios II, the ABI is documented here:
4127 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4129 ==> U-Boot will use gp to hold a pointer to the global data
4131 Note: on Nios II, we give "-G0" option to gcc and don't use gp
4132 to access small data sections, so gp is free.
4134 On NDS32, the following registers are used:
4136 R0-R1: argument/return
4138 R15: temporary register for assembler
4139 R16: trampoline register
4140 R28: frame pointer (FP)
4141 R29: global pointer (GP)
4142 R30: link register (LP)
4143 R31: stack pointer (SP)
4144 PC: program counter (PC)
4146 ==> U-Boot will use R10 to hold a pointer to the global data
4148 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4149 or current versions of GCC may "optimize" the code too much.
4151 On RISC-V, the following registers are used:
4153 x0: hard-wired zero (zero)
4154 x1: return address (ra)
4155 x2: stack pointer (sp)
4156 x3: global pointer (gp)
4157 x4: thread pointer (tp)
4158 x5: link register (t0)
4159 x8: frame pointer (fp)
4160 x10-x11: arguments/return values (a0-1)
4161 x12-x17: arguments (a2-7)
4162 x28-31: temporaries (t3-6)
4163 pc: program counter (pc)
4165 ==> U-Boot will use gp to hold a pointer to the global data
4170 U-Boot runs in system state and uses physical addresses, i.e. the
4171 MMU is not used either for address mapping nor for memory protection.
4173 The available memory is mapped to fixed addresses using the memory
4174 controller. In this process, a contiguous block is formed for each
4175 memory type (Flash, SDRAM, SRAM), even when it consists of several
4176 physical memory banks.
4178 U-Boot is installed in the first 128 kB of the first Flash bank (on
4179 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4180 booting and sizing and initializing DRAM, the code relocates itself
4181 to the upper end of DRAM. Immediately below the U-Boot code some
4182 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4183 configuration setting]. Below that, a structure with global Board
4184 Info data is placed, followed by the stack (growing downward).
4186 Additionally, some exception handler code is copied to the low 8 kB
4187 of DRAM (0x00000000 ... 0x00001FFF).
4189 So a typical memory configuration with 16 MB of DRAM could look like
4192 0x0000 0000 Exception Vector code
4195 0x0000 2000 Free for Application Use
4201 0x00FB FF20 Monitor Stack (Growing downward)
4202 0x00FB FFAC Board Info Data and permanent copy of global data
4203 0x00FC 0000 Malloc Arena
4206 0x00FE 0000 RAM Copy of Monitor Code
4207 ... eventually: LCD or video framebuffer
4208 ... eventually: pRAM (Protected RAM - unchanged by reset)
4209 0x00FF FFFF [End of RAM]
4212 System Initialization:
4213 ----------------------
4215 In the reset configuration, U-Boot starts at the reset entry point
4216 (on most PowerPC systems at address 0x00000100). Because of the reset
4217 configuration for CS0# this is a mirror of the on board Flash memory.
4218 To be able to re-map memory U-Boot then jumps to its link address.
4219 To be able to implement the initialization code in C, a (small!)
4220 initial stack is set up in the internal Dual Ported RAM (in case CPUs
4221 which provide such a feature like), or in a locked part of the data
4222 cache. After that, U-Boot initializes the CPU core, the caches and
4225 Next, all (potentially) available memory banks are mapped using a
4226 preliminary mapping. For example, we put them on 512 MB boundaries
4227 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4228 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4229 programmed for SDRAM access. Using the temporary configuration, a
4230 simple memory test is run that determines the size of the SDRAM
4233 When there is more than one SDRAM bank, and the banks are of
4234 different size, the largest is mapped first. For equal size, the first
4235 bank (CS2#) is mapped first. The first mapping is always for address
4236 0x00000000, with any additional banks following immediately to create
4237 contiguous memory starting from 0.
4239 Then, the monitor installs itself at the upper end of the SDRAM area
4240 and allocates memory for use by malloc() and for the global Board
4241 Info data; also, the exception vector code is copied to the low RAM
4242 pages, and the final stack is set up.
4244 Only after this relocation will you have a "normal" C environment;
4245 until that you are restricted in several ways, mostly because you are
4246 running from ROM, and because the code will have to be relocated to a
4250 U-Boot Porting Guide:
4251 ----------------------
4253 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4257 int main(int argc, char *argv[])
4259 sighandler_t no_more_time;
4261 signal(SIGALRM, no_more_time);
4262 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4264 if (available_money > available_manpower) {
4265 Pay consultant to port U-Boot;
4269 Download latest U-Boot source;
4271 Subscribe to u-boot mailing list;
4274 email("Hi, I am new to U-Boot, how do I get started?");
4277 Read the README file in the top level directory;
4278 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
4279 Read applicable doc/README.*;
4280 Read the source, Luke;
4281 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4284 if (available_money > toLocalCurrency ($2500))
4287 Add a lot of aggravation and time;
4289 if (a similar board exists) { /* hopefully... */
4290 cp -a board/<similar> board/<myboard>
4291 cp include/configs/<similar>.h include/configs/<myboard>.h
4293 Create your own board support subdirectory;
4294 Create your own board include/configs/<myboard>.h file;
4296 Edit new board/<myboard> files
4297 Edit new include/configs/<myboard>.h
4302 Add / modify source code;
4306 email("Hi, I am having problems...");
4308 Send patch file to the U-Boot email list;
4309 if (reasonable critiques)
4310 Incorporate improvements from email list code review;
4312 Defend code as written;
4318 void no_more_time (int sig)
4327 All contributions to U-Boot should conform to the Linux kernel
4328 coding style; see the kernel coding style guide at
4329 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4330 script "scripts/Lindent" in your Linux kernel source directory.
4332 Source files originating from a different project (for example the
4333 MTD subsystem) are generally exempt from these guidelines and are not
4334 reformatted to ease subsequent migration to newer versions of those
4337 Please note that U-Boot is implemented in C (and to some small parts in
4338 Assembler); no C++ is used, so please do not use C++ style comments (//)
4341 Please also stick to the following formatting rules:
4342 - remove any trailing white space
4343 - use TAB characters for indentation and vertical alignment, not spaces
4344 - make sure NOT to use DOS '\r\n' line feeds
4345 - do not add more than 2 consecutive empty lines to source files
4346 - do not add trailing empty lines to source files
4348 Submissions which do not conform to the standards may be returned
4349 with a request to reformat the changes.
4355 Since the number of patches for U-Boot is growing, we need to
4356 establish some rules. Submissions which do not conform to these rules
4357 may be rejected, even when they contain important and valuable stuff.
4359 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
4361 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4362 see https://lists.denx.de/listinfo/u-boot
4364 When you send a patch, please include the following information with
4367 * For bug fixes: a description of the bug and how your patch fixes
4368 this bug. Please try to include a way of demonstrating that the
4369 patch actually fixes something.
4371 * For new features: a description of the feature and your
4374 * For major contributions, add a MAINTAINERS file with your
4375 information and associated file and directory references.
4377 * When you add support for a new board, don't forget to add a
4378 maintainer e-mail address to the boards.cfg file, too.
4380 * If your patch adds new configuration options, don't forget to
4381 document these in the README file.
4383 * The patch itself. If you are using git (which is *strongly*
4384 recommended) you can easily generate the patch using the
4385 "git format-patch". If you then use "git send-email" to send it to
4386 the U-Boot mailing list, you will avoid most of the common problems
4387 with some other mail clients.
4389 If you cannot use git, use "diff -purN OLD NEW". If your version of
4390 diff does not support these options, then get the latest version of
4393 The current directory when running this command shall be the parent
4394 directory of the U-Boot source tree (i. e. please make sure that
4395 your patch includes sufficient directory information for the
4398 We prefer patches as plain text. MIME attachments are discouraged,
4399 and compressed attachments must not be used.
4401 * If one logical set of modifications affects or creates several
4402 files, all these changes shall be submitted in a SINGLE patch file.
4404 * Changesets that contain different, unrelated modifications shall be
4405 submitted as SEPARATE patches, one patch per changeset.
4410 * Before sending the patch, run the buildman script on your patched
4411 source tree and make sure that no errors or warnings are reported
4412 for any of the boards.
4414 * Keep your modifications to the necessary minimum: A patch
4415 containing several unrelated changes or arbitrary reformats will be
4416 returned with a request to re-formatting / split it.
4418 * If you modify existing code, make sure that your new code does not
4419 add to the memory footprint of the code ;-) Small is beautiful!
4420 When adding new features, these should compile conditionally only
4421 (using #ifdef), and the resulting code with the new feature
4422 disabled must not need more memory than the old code without your
4425 * Remember that there is a size limit of 100 kB per message on the
4426 u-boot mailing list. Bigger patches will be moderated. If they are
4427 reasonable and not too big, they will be acknowledged. But patches
4428 bigger than the size limit should be avoided.