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 /boot Support for images and booting
148 /cmd U-Boot commands functions
149 /common Misc architecture-independent functions
150 /configs Board default configuration files
151 /disk Code for disk drive partition handling
152 /doc Documentation (a mix of ReST and READMEs)
153 /drivers Device drivers
154 /dts Makefile for building internal U-Boot fdt.
155 /env Environment support
156 /examples Example code for standalone applications, etc.
157 /fs Filesystem code (cramfs, ext2, jffs2, etc.)
158 /include Header Files
159 /lib Library routines generic to all architectures
160 /Licenses Various license files
162 /post Power On Self Test
163 /scripts Various build scripts and Makefiles
164 /test Various unit test files
165 /tools Tools to build and sign FIT images, etc.
167 Software Configuration:
168 =======================
170 Configuration is usually done using C preprocessor defines; the
171 rationale behind that is to avoid dead code whenever possible.
173 There are two classes of configuration variables:
175 * Configuration _OPTIONS_:
176 These are selectable by the user and have names beginning with
179 * Configuration _SETTINGS_:
180 These depend on the hardware etc. and should not be meddled with if
181 you don't know what you're doing; they have names beginning with
184 Previously, all configuration was done by hand, which involved creating
185 symbolic links and editing configuration files manually. More recently,
186 U-Boot has added the Kbuild infrastructure used by the Linux kernel,
187 allowing you to use the "make menuconfig" command to configure your
191 Selection of Processor Architecture and Board Type:
192 ---------------------------------------------------
194 For all supported boards there are ready-to-use default
195 configurations available; just type "make <board_name>_defconfig".
197 Example: For a TQM823L module type:
200 make TQM823L_defconfig
202 Note: If you're looking for the default configuration file for a board
203 you're sure used to be there but is now missing, check the file
204 doc/README.scrapyard for a list of no longer supported boards.
209 U-Boot can be built natively to run on a Linux host using the 'sandbox'
210 board. This allows feature development which is not board- or architecture-
211 specific to be undertaken on a native platform. The sandbox is also used to
212 run some of U-Boot's tests.
214 See doc/arch/sandbox.rst for more details.
217 Board Initialisation Flow:
218 --------------------------
220 This is the intended start-up flow for boards. This should apply for both
221 SPL and U-Boot proper (i.e. they both follow the same rules).
223 Note: "SPL" stands for "Secondary Program Loader," which is explained in
224 more detail later in this file.
226 At present, SPL mostly uses a separate code path, but the function names
227 and roles of each function are the same. Some boards or architectures
228 may not conform to this. At least most ARM boards which use
229 CONFIG_SPL_FRAMEWORK conform to this.
231 Execution typically starts with an architecture-specific (and possibly
232 CPU-specific) start.S file, such as:
234 - arch/arm/cpu/armv7/start.S
235 - arch/powerpc/cpu/mpc83xx/start.S
236 - arch/mips/cpu/start.S
238 and so on. From there, three functions are called; the purpose and
239 limitations of each of these functions are described below.
242 - purpose: essential init to permit execution to reach board_init_f()
243 - no global_data or BSS
244 - there is no stack (ARMv7 may have one but it will soon be removed)
245 - must not set up SDRAM or use console
246 - must only do the bare minimum to allow execution to continue to
248 - this is almost never needed
249 - return normally from this function
252 - purpose: set up the machine ready for running board_init_r():
253 i.e. SDRAM and serial UART
254 - global_data is available
256 - BSS is not available, so you cannot use global/static variables,
257 only stack variables and global_data
259 Non-SPL-specific notes:
260 - dram_init() is called to set up DRAM. If already done in SPL this
264 - you can override the entire board_init_f() function with your own
266 - preloader_console_init() can be called here in extremis
267 - should set up SDRAM, and anything needed to make the UART work
268 - there is no need to clear BSS, it will be done by crt0.S
269 - for specific scenarios on certain architectures an early BSS *can*
270 be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
271 of BSS prior to entering board_init_f()) but doing so is discouraged.
272 Instead it is strongly recommended to architect any code changes
273 or additions such to not depend on the availability of BSS during
274 board_init_f() as indicated in other sections of this README to
275 maintain compatibility and consistency across the entire code base.
276 - must return normally from this function (don't call board_init_r()
279 Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
280 this point the stack and global_data are relocated to below
281 CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
285 - purpose: main execution, common code
286 - global_data is available
288 - BSS is available, all static/global variables can be used
289 - execution eventually continues to main_loop()
291 Non-SPL-specific notes:
292 - U-Boot is relocated to the top of memory and is now running from
296 - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
297 CONFIG_SPL_STACK_R_ADDR points into SDRAM
298 - preloader_console_init() can be called here - typically this is
299 done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
300 spl_board_init() function containing this call
301 - 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_SYS_FSL_CORENET_SNOOPVEC_COREONLY
379 This is the value to write into CCSR offset 0x18600
380 according to the A004510 workaround.
382 CONFIG_SYS_FSL_DSP_DDR_ADDR
383 This value denotes start offset of DDR memory which is
384 connected exclusively to the DSP cores.
386 CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
387 This value denotes start offset of M2 memory
388 which is directly connected to the DSP core.
390 CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
391 This value denotes start offset of M3 memory which is directly
392 connected to the DSP core.
394 CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
395 This value denotes start offset of DSP CCSR space.
397 CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
398 Single Source Clock is clocking mode present in some of FSL SoC's.
399 In this mode, a single differential clock is used to supply
400 clocks to the sysclock, ddrclock and usbclock.
402 CONFIG_SYS_CPC_REINIT_F
403 This CONFIG is defined when the CPC is configured as SRAM at the
404 time of U-Boot entry and is required to be re-initialized.
406 - Generic CPU options:
407 CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
409 Defines the endianess of the CPU. Implementation of those
410 values is arch specific.
413 Freescale DDR driver in use. This type of DDR controller is
414 found in mpc83xx, mpc85xx as well as some ARM core SoCs.
416 CONFIG_SYS_FSL_DDR_ADDR
417 Freescale DDR memory-mapped register base.
419 CONFIG_SYS_FSL_DDR_EMU
420 Specify emulator support for DDR. Some DDR features such as
421 deskew training are not available.
423 CONFIG_SYS_FSL_DDRC_GEN1
424 Freescale DDR1 controller.
426 CONFIG_SYS_FSL_DDRC_GEN2
427 Freescale DDR2 controller.
429 CONFIG_SYS_FSL_DDRC_GEN3
430 Freescale DDR3 controller.
432 CONFIG_SYS_FSL_DDRC_GEN4
433 Freescale DDR4 controller.
435 CONFIG_SYS_FSL_DDRC_ARM_GEN3
436 Freescale DDR3 controller for ARM-based SoCs.
439 Board config to use DDR1. It can be enabled for SoCs with
440 Freescale DDR1 or DDR2 controllers, depending on the board
444 Board config to use DDR2. It can be enabled for SoCs with
445 Freescale DDR2 or DDR3 controllers, depending on the board
449 Board config to use DDR3. It can be enabled for SoCs with
450 Freescale DDR3 or DDR3L controllers.
453 Board config to use DDR3L. It can be enabled for SoCs with
456 CONFIG_SYS_FSL_IFC_BE
457 Defines the IFC controller register space as Big Endian
459 CONFIG_SYS_FSL_IFC_LE
460 Defines the IFC controller register space as Little Endian
462 CONFIG_SYS_FSL_IFC_CLK_DIV
463 Defines divider of platform clock(clock input to IFC controller).
465 CONFIG_SYS_FSL_LBC_CLK_DIV
466 Defines divider of platform clock(clock input to eLBC controller).
468 CONFIG_SYS_FSL_DDR_BE
469 Defines the DDR controller register space as Big Endian
471 CONFIG_SYS_FSL_DDR_LE
472 Defines the DDR controller register space as Little Endian
474 CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
475 Physical address from the view of DDR controllers. It is the
476 same as CONFIG_SYS_DDR_SDRAM_BASE for all Power SoCs. But
477 it could be different for ARM SoCs.
479 CONFIG_SYS_FSL_DDR_INTLV_256B
480 DDR controller interleaving on 256-byte. This is a special
481 interleaving mode, handled by Dickens for Freescale layerscape
484 CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
485 Number of controllers used as main memory.
487 CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
488 Number of controllers used for other than main memory.
490 CONFIG_SYS_FSL_HAS_DP_DDR
491 Defines the SoC has DP-DDR used for DPAA.
493 CONFIG_SYS_FSL_SEC_BE
494 Defines the SEC controller register space as Big Endian
496 CONFIG_SYS_FSL_SEC_LE
497 Defines the SEC controller register space as Little Endian
500 CONFIG_SYS_INIT_SP_OFFSET
502 Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
503 pointer. This is needed for the temporary stack before
506 CONFIG_XWAY_SWAP_BYTES
508 Enable compilation of tools/xway-swap-bytes needed for Lantiq
509 XWAY SoCs for booting from NOR flash. The U-Boot image needs to
510 be swapped if a flash programmer is used.
513 CONFIG_SYS_EXCEPTION_VECTORS_HIGH
515 Select high exception vectors of the ARM core, e.g., do not
516 clear the V bit of the c1 register of CP15.
519 Generic timer clock source frequency.
521 COUNTER_FREQUENCY_REAL
522 Generic timer clock source frequency if the real clock is
523 different from COUNTER_FREQUENCY, and can only be determined
527 CONFIG_TEGRA_SUPPORT_NON_SECURE
529 Support executing U-Boot in non-secure (NS) mode. Certain
530 impossible actions will be skipped if the CPU is in NS mode,
531 such as ARM architectural timer initialization.
533 - Linux Kernel Interface:
534 CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]
536 When transferring memsize parameter to Linux, some versions
537 expect it to be in bytes, others in MB.
538 Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
542 New kernel versions are expecting firmware settings to be
543 passed using flattened device trees (based on open firmware
547 * New libfdt-based support
548 * Adds the "fdt" command
549 * The bootm command automatically updates the fdt
551 OF_TBCLK - The timebase frequency.
553 boards with QUICC Engines require OF_QE to set UCC MAC
558 U-Boot can detect if an IDE device is present or not.
559 If not, and this new config option is activated, U-Boot
560 removes the ATA node from the DTS before booting Linux,
561 so the Linux IDE driver does not probe the device and
562 crash. This is needed for buggy hardware (uc101) where
563 no pull down resistor is connected to the signal IDE5V_DD7.
565 - vxWorks boot parameters:
567 bootvx constructs a valid bootline using the following
568 environments variables: bootdev, bootfile, ipaddr, netmask,
569 serverip, gatewayip, hostname, othbootargs.
570 It loads the vxWorks image pointed bootfile.
572 Note: If a "bootargs" environment is defined, it will override
573 the defaults discussed just above.
575 - Cache Configuration for ARM:
576 CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
578 CONFIG_SYS_PL310_BASE - Physical base address of PL310
579 controller register space
584 If you have Amba PrimeCell PL011 UARTs, set this variable to
585 the clock speed of the UARTs.
589 If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
590 define this to a list of base addresses for each (supported)
591 port. See e.g. include/configs/versatile.h
593 CONFIG_SERIAL_HW_FLOW_CONTROL
595 Define this variable to enable hw flow control in serial driver.
596 Current user of this option is drivers/serial/nsl16550.c driver
598 - Serial Download Echo Mode:
600 If defined to 1, all characters received during a
601 serial download (using the "loads" command) are
602 echoed back. This might be needed by some terminal
603 emulations (like "cu"), but may as well just take
604 time on others. This setting #define's the initial
605 value of the "loads_echo" environment variable.
607 - Removal of commands
608 If no commands are needed to boot, you can disable
609 CONFIG_CMDLINE to remove them. In this case, the command line
610 will not be available, and when U-Boot wants to execute the
611 boot command (on start-up) it will call board_run_command()
612 instead. This can reduce image size significantly for very
613 simple boot procedures.
615 - Regular expression support:
617 If this variable is defined, U-Boot is linked against
618 the SLRE (Super Light Regular Expression) library,
619 which adds regex support to some commands, as for
620 example "env grep" and "setexpr".
623 CONFIG_SYS_WATCHDOG_FREQ
624 Some platforms automatically call WATCHDOG_RESET()
625 from the timer interrupt handler every
626 CONFIG_SYS_WATCHDOG_FREQ interrupts. If not set by the
627 board configuration file, a default of CONFIG_SYS_HZ/2
628 (i.e. 500) is used. Setting CONFIG_SYS_WATCHDOG_FREQ
629 to 0 disables calling WATCHDOG_RESET() from the timer
634 When CONFIG_CMD_DATE is selected, the type of the RTC
635 has to be selected, too. Define exactly one of the
638 CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
639 CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
640 CONFIG_RTC_MC146818 - use MC146818 RTC
641 CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
642 CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
643 CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
644 CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
645 CONFIG_RTC_DS164x - use Dallas DS164x RTC
646 CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
647 CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
648 CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
649 CONFIG_SYS_RV3029_TCR - enable trickle charger on
652 Note that if the RTC uses I2C, then the I2C interface
653 must also be configured. See I2C Support, below.
656 CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
658 The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
659 chip-ngpio pairs that tell the PCA953X driver the number of
660 pins supported by a particular chip.
662 Note that if the GPIO device uses I2C, then the I2C interface
663 must also be configured. See I2C Support, below.
666 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
667 accesses and can checksum them or write a list of them out
668 to memory. See the 'iotrace' command for details. This is
669 useful for testing device drivers since it can confirm that
670 the driver behaves the same way before and after a code
671 change. Currently this is supported on sandbox and arm. To
672 add support for your architecture, add '#include <iotrace.h>'
673 to the bottom of arch/<arch>/include/asm/io.h and test.
675 Example output from the 'iotrace stats' command is below.
676 Note that if the trace buffer is exhausted, the checksum will
677 still continue to operate.
680 Start: 10000000 (buffer start address)
681 Size: 00010000 (buffer size)
682 Offset: 00000120 (current buffer offset)
683 Output: 10000120 (start + offset)
684 Count: 00000018 (number of trace records)
685 CRC32: 9526fb66 (CRC32 of all trace records)
689 When CONFIG_TIMESTAMP is selected, the timestamp
690 (date and time) of an image is printed by image
691 commands like bootm or iminfo. This option is
692 automatically enabled when you select CONFIG_CMD_DATE .
694 - Partition Labels (disklabels) Supported:
695 Zero or more of the following:
696 CONFIG_MAC_PARTITION Apple's MacOS partition table.
697 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
698 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
699 bootloader. Note 2TB partition limit; see
701 CONFIG_SCSI) you must configure support for at
702 least one non-MTD partition type as well.
707 Set this to enable support for disks larger than 137GB
708 Also look at CONFIG_SYS_64BIT_LBA.
709 Whithout these , LBA48 support uses 32bit variables and will 'only'
710 support disks up to 2.1TB.
712 CONFIG_SYS_64BIT_LBA:
713 When enabled, makes the IDE subsystem use 64bit sector addresses.
716 - NETWORK Support (PCI):
718 Utility code for direct access to the SPI bus on Intel 8257x.
719 This does not do anything useful unless you set at least one
720 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
723 Support for National dp83815 chips.
726 Support for National dp8382[01] gigabit chips.
728 - NETWORK Support (other):
730 Support for the Calxeda XGMAC device
733 Support for SMSC's LAN91C96 chips.
735 CONFIG_LAN91C96_USE_32_BIT
736 Define this to enable 32 bit addressing
739 Support for SMSC's LAN91C111 chip
742 Define this to hold the physical address
743 of the device (I/O space)
745 CONFIG_SMC_USE_32_BIT
746 Define this if data bus is 32 bits
748 CONFIG_SMC_USE_IOFUNCS
749 Define this to use i/o functions instead of macros
750 (some hardware wont work with macros)
752 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
753 Define this if you have more then 3 PHYs.
756 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
758 CONFIG_FTGMAC100_EGIGA
759 Define this to use GE link update with gigabit PHY.
760 Define this if FTGMAC100 is connected to gigabit PHY.
761 If your system has 10/100 PHY only, it might not occur
762 wrong behavior. Because PHY usually return timeout or
763 useless data when polling gigabit status and gigabit
764 control registers. This behavior won't affect the
765 correctnessof 10/100 link speed update.
768 Support for Renesas on-chip Ethernet controller
770 CONFIG_SH_ETHER_USE_PORT
771 Define the number of ports to be used
773 CONFIG_SH_ETHER_PHY_ADDR
774 Define the ETH PHY's address
776 CONFIG_SH_ETHER_CACHE_WRITEBACK
777 If this option is set, the driver enables cache flush.
783 CONFIG_TPM_TIS_INFINEON
784 Support for Infineon i2c bus TPM devices. Only one device
785 per system is supported at this time.
787 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
788 Define the burst count bytes upper limit
791 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
793 CONFIG_TPM_ST33ZP24_I2C
794 Support for STMicroelectronics ST33ZP24 I2C devices.
795 Requires TPM_ST33ZP24 and I2C.
797 CONFIG_TPM_ST33ZP24_SPI
798 Support for STMicroelectronics ST33ZP24 SPI devices.
799 Requires TPM_ST33ZP24 and SPI.
802 Support for Atmel TWI TPM device. Requires I2C support.
805 Support for generic parallel port TPM devices. Only one device
806 per system is supported at this time.
808 CONFIG_TPM_TIS_BASE_ADDRESS
809 Base address where the generic TPM device is mapped
810 to. Contemporary x86 systems usually map it at
814 Define this to enable the TPM support library which provides
815 functional interfaces to some TPM commands.
816 Requires support for a TPM device.
818 CONFIG_TPM_AUTH_SESSIONS
819 Define this to enable authorized functions in the TPM library.
820 Requires CONFIG_TPM and CONFIG_SHA1.
823 At the moment only the UHCI host controller is
824 supported (PIP405, MIP405); define
825 CONFIG_USB_UHCI to enable it.
826 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
827 and define CONFIG_USB_STORAGE to enable the USB
830 Supported are USB Keyboards and USB Floppy drives
833 CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
834 txfilltuning field in the EHCI controller on reset.
836 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
840 Define the below if you wish to use the USB console.
841 Once firmware is rebuilt from a serial console issue the
842 command "setenv stdin usbtty; setenv stdout usbtty" and
843 attach your USB cable. The Unix command "dmesg" should print
844 it has found a new device. The environment variable usbtty
845 can be set to gserial or cdc_acm to enable your device to
846 appear to a USB host as a Linux gserial device or a
847 Common Device Class Abstract Control Model serial device.
848 If you select usbtty = gserial you should be able to enumerate
850 # modprobe usbserial vendor=0xVendorID product=0xProductID
851 else if using cdc_acm, simply setting the environment
852 variable usbtty to be cdc_acm should suffice. The following
853 might be defined in YourBoardName.h
856 Define this to build a UDC device
859 Define this to have a tty type of device available to
860 talk to the UDC device
863 Define this to enable the high speed support for usb
864 device and usbtty. If this feature is enabled, a routine
865 int is_usbd_high_speed(void)
866 also needs to be defined by the driver to dynamically poll
867 whether the enumeration has succeded at high speed or full
870 If you have a USB-IF assigned VendorID then you may wish to
871 define your own vendor specific values either in BoardName.h
872 or directly in usbd_vendor_info.h. If you don't define
873 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
874 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
875 should pretend to be a Linux device to it's target host.
877 CONFIG_USBD_MANUFACTURER
878 Define this string as the name of your company for
879 - CONFIG_USBD_MANUFACTURER "my company"
881 CONFIG_USBD_PRODUCT_NAME
882 Define this string as the name of your product
883 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
886 Define this as your assigned Vendor ID from the USB
887 Implementors Forum. This *must* be a genuine Vendor ID
888 to avoid polluting the USB namespace.
889 - CONFIG_USBD_VENDORID 0xFFFF
891 CONFIG_USBD_PRODUCTID
892 Define this as the unique Product ID
894 - CONFIG_USBD_PRODUCTID 0xFFFF
896 - ULPI Layer Support:
897 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
898 the generic ULPI layer. The generic layer accesses the ULPI PHY
899 via the platform viewport, so you need both the genric layer and
900 the viewport enabled. Currently only Chipidea/ARC based
901 viewport is supported.
902 To enable the ULPI layer support, define CONFIG_USB_ULPI and
903 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
904 If your ULPI phy needs a different reference clock than the
905 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
906 the appropriate value in Hz.
909 The MMC controller on the Intel PXA is supported. To
910 enable this define CONFIG_MMC. The MMC can be
911 accessed from the boot prompt by mapping the device
912 to physical memory similar to flash. Command line is
913 enabled with CONFIG_CMD_MMC. The MMC driver also works with
914 the FAT fs. This is enabled with CONFIG_CMD_FAT.
917 Support for Renesas on-chip MMCIF controller
920 Define the base address of MMCIF registers
923 Define the clock frequency for MMCIF
925 - USB Device Firmware Update (DFU) class support:
927 This enables the USB portion of the DFU USB class
930 This enables support for exposing NAND devices via DFU.
933 This enables support for exposing RAM via DFU.
934 Note: DFU spec refer to non-volatile memory usage, but
935 allow usages beyond the scope of spec - here RAM usage,
936 one that would help mostly the developer.
938 CONFIG_SYS_DFU_DATA_BUF_SIZE
939 Dfu transfer uses a buffer before writing data to the
940 raw storage device. Make the size (in bytes) of this buffer
941 configurable. The size of this buffer is also configurable
942 through the "dfu_bufsiz" environment variable.
944 CONFIG_SYS_DFU_MAX_FILE_SIZE
945 When updating files rather than the raw storage device,
946 we use a static buffer to copy the file into and then write
947 the buffer once we've been given the whole file. Define
948 this to the maximum filesize (in bytes) for the buffer.
949 Default is 4 MiB if undefined.
951 DFU_DEFAULT_POLL_TIMEOUT
952 Poll timeout [ms], is the timeout a device can send to the
953 host. The host must wait for this timeout before sending
954 a subsequent DFU_GET_STATUS request to the device.
956 DFU_MANIFEST_POLL_TIMEOUT
957 Poll timeout [ms], which the device sends to the host when
958 entering dfuMANIFEST state. Host waits this timeout, before
959 sending again an USB request to the device.
961 - Journaling Flash filesystem support:
962 CONFIG_SYS_JFFS2_FIRST_SECTOR,
963 CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
964 Define these for a default partition on a NOR device
967 See Kconfig help for available keyboard drivers.
969 - LCD Support: CONFIG_LCD
971 Define this to enable LCD support (for output to LCD
972 display); also select one of the supported displays
973 by defining one of these:
975 CONFIG_NEC_NL6448AC33:
977 NEC NL6448AC33-18. Active, color, single scan.
979 CONFIG_NEC_NL6448BC20
981 NEC NL6448BC20-08. 6.5", 640x480.
982 Active, color, single scan.
984 CONFIG_NEC_NL6448BC33_54
986 NEC NL6448BC33-54. 10.4", 640x480.
987 Active, color, single scan.
991 Sharp 320x240. Active, color, single scan.
992 It isn't 16x9, and I am not sure what it is.
994 CONFIG_SHARP_LQ64D341
996 Sharp LQ64D341 display, 640x480.
997 Active, color, single scan.
1001 HLD1045 display, 640x480.
1002 Active, color, single scan.
1006 Optrex CBL50840-2 NF-FW 99 22 M5
1008 Hitachi LMG6912RPFC-00T
1012 320x240. Black & white.
1014 CONFIG_LCD_ALIGNMENT
1016 Normally the LCD is page-aligned (typically 4KB). If this is
1017 defined then the LCD will be aligned to this value instead.
1018 For ARM it is sometimes useful to use MMU_SECTION_SIZE
1019 here, since it is cheaper to change data cache settings on
1020 a per-section basis.
1025 Sometimes, for example if the display is mounted in portrait
1026 mode or even if it's mounted landscape but rotated by 180degree,
1027 we need to rotate our content of the display relative to the
1028 framebuffer, so that user can read the messages which are
1030 Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1031 initialized with a given rotation from "vl_rot" out of
1032 "vidinfo_t" which is provided by the board specific code.
1033 The value for vl_rot is coded as following (matching to
1034 fbcon=rotate:<n> linux-kernel commandline):
1035 0 = no rotation respectively 0 degree
1036 1 = 90 degree rotation
1037 2 = 180 degree rotation
1038 3 = 270 degree rotation
1040 If CONFIG_LCD_ROTATION is not defined, the console will be
1041 initialized with 0degree rotation.
1044 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1046 The clock frequency of the MII bus
1048 CONFIG_PHY_CMD_DELAY (ppc4xx)
1050 Some PHY like Intel LXT971A need extra delay after
1051 command issued before MII status register can be read
1056 Define a default value for the IP address to use for
1057 the default Ethernet interface, in case this is not
1058 determined through e.g. bootp.
1059 (Environment variable "ipaddr")
1061 - Server IP address:
1064 Defines a default value for the IP address of a TFTP
1065 server to contact when using the "tftboot" command.
1066 (Environment variable "serverip")
1068 - Gateway IP address:
1071 Defines a default value for the IP address of the
1072 default router where packets to other networks are
1074 (Environment variable "gatewayip")
1079 Defines a default value for the subnet mask (or
1080 routing prefix) which is used to determine if an IP
1081 address belongs to the local subnet or needs to be
1082 forwarded through a router.
1083 (Environment variable "netmask")
1085 - BOOTP Recovery Mode:
1086 CONFIG_BOOTP_RANDOM_DELAY
1088 If you have many targets in a network that try to
1089 boot using BOOTP, you may want to avoid that all
1090 systems send out BOOTP requests at precisely the same
1091 moment (which would happen for instance at recovery
1092 from a power failure, when all systems will try to
1093 boot, thus flooding the BOOTP server. Defining
1094 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1095 inserted before sending out BOOTP requests. The
1096 following delays are inserted then:
1098 1st BOOTP request: delay 0 ... 1 sec
1099 2nd BOOTP request: delay 0 ... 2 sec
1100 3rd BOOTP request: delay 0 ... 4 sec
1102 BOOTP requests: delay 0 ... 8 sec
1104 CONFIG_BOOTP_ID_CACHE_SIZE
1106 BOOTP packets are uniquely identified using a 32-bit ID. The
1107 server will copy the ID from client requests to responses and
1108 U-Boot will use this to determine if it is the destination of
1109 an incoming response. Some servers will check that addresses
1110 aren't in use before handing them out (usually using an ARP
1111 ping) and therefore take up to a few hundred milliseconds to
1112 respond. Network congestion may also influence the time it
1113 takes for a response to make it back to the client. If that
1114 time is too long, U-Boot will retransmit requests. In order
1115 to allow earlier responses to still be accepted after these
1116 retransmissions, U-Boot's BOOTP client keeps a small cache of
1117 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1118 cache. The default is to keep IDs for up to four outstanding
1119 requests. Increasing this will allow U-Boot to accept offers
1120 from a BOOTP client in networks with unusually high latency.
1122 - DHCP Advanced Options:
1124 - Link-local IP address negotiation:
1125 Negotiate with other link-local clients on the local network
1126 for an address that doesn't require explicit configuration.
1127 This is especially useful if a DHCP server cannot be guaranteed
1128 to exist in all environments that the device must operate.
1130 See doc/README.link-local for more information.
1132 - MAC address from environment variables
1134 FDT_SEQ_MACADDR_FROM_ENV
1136 Fix-up device tree with MAC addresses fetched sequentially from
1137 environment variables. This config work on assumption that
1138 non-usable ethernet node of device-tree are either not present
1139 or their status has been marked as "disabled".
1142 CONFIG_CDP_DEVICE_ID
1144 The device id used in CDP trigger frames.
1146 CONFIG_CDP_DEVICE_ID_PREFIX
1148 A two character string which is prefixed to the MAC address
1153 A printf format string which contains the ascii name of
1154 the port. Normally is set to "eth%d" which sets
1155 eth0 for the first Ethernet, eth1 for the second etc.
1157 CONFIG_CDP_CAPABILITIES
1159 A 32bit integer which indicates the device capabilities;
1160 0x00000010 for a normal host which does not forwards.
1164 An ascii string containing the version of the software.
1168 An ascii string containing the name of the platform.
1172 A 32bit integer sent on the trigger.
1174 CONFIG_CDP_POWER_CONSUMPTION
1176 A 16bit integer containing the power consumption of the
1177 device in .1 of milliwatts.
1179 CONFIG_CDP_APPLIANCE_VLAN_TYPE
1181 A byte containing the id of the VLAN.
1183 - Status LED: CONFIG_LED_STATUS
1185 Several configurations allow to display the current
1186 status using a LED. For instance, the LED will blink
1187 fast while running U-Boot code, stop blinking as
1188 soon as a reply to a BOOTP request was received, and
1189 start blinking slow once the Linux kernel is running
1190 (supported by a status LED driver in the Linux
1191 kernel). Defining CONFIG_LED_STATUS enables this
1196 CONFIG_LED_STATUS_GPIO
1197 The status LED can be connected to a GPIO pin.
1198 In such cases, the gpio_led driver can be used as a
1199 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1200 to include the gpio_led driver in the U-Boot binary.
1202 CONFIG_GPIO_LED_INVERTED_TABLE
1203 Some GPIO connected LEDs may have inverted polarity in which
1204 case the GPIO high value corresponds to LED off state and
1205 GPIO low value corresponds to LED on state.
1206 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1207 with a list of GPIO LEDs that have inverted polarity.
1210 CONFIG_SYS_NUM_I2C_BUSES
1211 Hold the number of i2c buses you want to use.
1213 CONFIG_SYS_I2C_DIRECT_BUS
1214 define this, if you don't use i2c muxes on your hardware.
1215 if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1218 CONFIG_SYS_I2C_MAX_HOPS
1219 define how many muxes are maximal consecutively connected
1220 on one i2c bus. If you not use i2c muxes, omit this
1223 CONFIG_SYS_I2C_BUSES
1224 hold a list of buses you want to use, only used if
1225 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1226 a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1227 CONFIG_SYS_NUM_I2C_BUSES = 9:
1229 CONFIG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
1230 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1231 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1232 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1233 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1234 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1235 {1, {I2C_NULL_HOP}}, \
1236 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1237 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1241 bus 0 on adapter 0 without a mux
1242 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1243 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1244 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1245 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1246 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1247 bus 6 on adapter 1 without a mux
1248 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1249 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1251 If you do not have i2c muxes on your board, omit this define.
1253 - Legacy I2C Support:
1254 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1255 then the following macros need to be defined (examples are
1256 from include/configs/lwmon.h):
1260 (Optional). Any commands necessary to enable the I2C
1261 controller or configure ports.
1263 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
1267 The code necessary to make the I2C data line active
1268 (driven). If the data line is open collector, this
1271 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
1275 The code necessary to make the I2C data line tri-stated
1276 (inactive). If the data line is open collector, this
1279 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1283 Code that returns true if the I2C data line is high,
1286 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1290 If <bit> is true, sets the I2C data line high. If it
1291 is false, it clears it (low).
1293 eg: #define I2C_SDA(bit) \
1294 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
1295 else immr->im_cpm.cp_pbdat &= ~PB_SDA
1299 If <bit> is true, sets the I2C clock line high. If it
1300 is false, it clears it (low).
1302 eg: #define I2C_SCL(bit) \
1303 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
1304 else immr->im_cpm.cp_pbdat &= ~PB_SCL
1308 This delay is invoked four times per clock cycle so this
1309 controls the rate of data transfer. The data rate thus
1310 is 1 / (I2C_DELAY * 4). Often defined to be something
1313 #define I2C_DELAY udelay(2)
1315 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1317 If your arch supports the generic GPIO framework (asm/gpio.h),
1318 then you may alternatively define the two GPIOs that are to be
1319 used as SCL / SDA. Any of the previous I2C_xxx macros will
1320 have GPIO-based defaults assigned to them as appropriate.
1322 You should define these to the GPIO value as given directly to
1323 the generic GPIO functions.
1325 CONFIG_SYS_I2C_INIT_BOARD
1327 When a board is reset during an i2c bus transfer
1328 chips might think that the current transfer is still
1329 in progress. On some boards it is possible to access
1330 the i2c SCLK line directly, either by using the
1331 processor pin as a GPIO or by having a second pin
1332 connected to the bus. If this option is defined a
1333 custom i2c_init_board() routine in boards/xxx/board.c
1334 is run early in the boot sequence.
1336 CONFIG_I2C_MULTI_BUS
1338 This option allows the use of multiple I2C buses, each of which
1339 must have a controller. At any point in time, only one bus is
1340 active. To switch to a different bus, use the 'i2c dev' command.
1341 Note that bus numbering is zero-based.
1343 CONFIG_SYS_I2C_NOPROBES
1345 This option specifies a list of I2C devices that will be skipped
1346 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
1347 is set, specify a list of bus-device pairs. Otherwise, specify
1348 a 1D array of device addresses
1351 #undef CONFIG_I2C_MULTI_BUS
1352 #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1354 will skip addresses 0x50 and 0x68 on a board with one I2C bus
1356 #define CONFIG_I2C_MULTI_BUS
1357 #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1359 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1361 CONFIG_SYS_SPD_BUS_NUM
1363 If defined, then this indicates the I2C bus number for DDR SPD.
1364 If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1366 CONFIG_SYS_RTC_BUS_NUM
1368 If defined, then this indicates the I2C bus number for the RTC.
1369 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1371 CONFIG_SOFT_I2C_READ_REPEATED_START
1373 defining this will force the i2c_read() function in
1374 the soft_i2c driver to perform an I2C repeated start
1375 between writing the address pointer and reading the
1376 data. If this define is omitted the default behaviour
1377 of doing a stop-start sequence will be used. Most I2C
1378 devices can use either method, but some require one or
1381 - SPI Support: CONFIG_SPI
1383 Enables SPI driver (so far only tested with
1384 SPI EEPROM, also an instance works with Crystal A/D and
1385 D/As on the SACSng board)
1387 CONFIG_SYS_SPI_MXC_WAIT
1388 Timeout for waiting until spi transfer completed.
1389 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1391 - FPGA Support: CONFIG_FPGA
1393 Enables FPGA subsystem.
1395 CONFIG_FPGA_<vendor>
1397 Enables support for specific chip vendors.
1400 CONFIG_FPGA_<family>
1402 Enables support for FPGA family.
1403 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1407 Specify the number of FPGA devices to support.
1409 CONFIG_SYS_FPGA_PROG_FEEDBACK
1411 Enable printing of hash marks during FPGA configuration.
1413 CONFIG_SYS_FPGA_CHECK_BUSY
1415 Enable checks on FPGA configuration interface busy
1416 status by the configuration function. This option
1417 will require a board or device specific function to
1422 If defined, a function that provides delays in the FPGA
1423 configuration driver.
1425 CONFIG_SYS_FPGA_CHECK_CTRLC
1426 Allow Control-C to interrupt FPGA configuration
1428 CONFIG_SYS_FPGA_CHECK_ERROR
1430 Check for configuration errors during FPGA bitfile
1431 loading. For example, abort during Virtex II
1432 configuration if the INIT_B line goes low (which
1433 indicated a CRC error).
1435 CONFIG_SYS_FPGA_WAIT_INIT
1437 Maximum time to wait for the INIT_B line to de-assert
1438 after PROB_B has been de-asserted during a Virtex II
1439 FPGA configuration sequence. The default time is 500
1442 CONFIG_SYS_FPGA_WAIT_BUSY
1444 Maximum time to wait for BUSY to de-assert during
1445 Virtex II FPGA configuration. The default is 5 ms.
1447 CONFIG_SYS_FPGA_WAIT_CONFIG
1449 Time to wait after FPGA configuration. The default is
1452 - Vendor Parameter Protection:
1454 U-Boot considers the values of the environment
1455 variables "serial#" (Board Serial Number) and
1456 "ethaddr" (Ethernet Address) to be parameters that
1457 are set once by the board vendor / manufacturer, and
1458 protects these variables from casual modification by
1459 the user. Once set, these variables are read-only,
1460 and write or delete attempts are rejected. You can
1461 change this behaviour:
1463 If CONFIG_ENV_OVERWRITE is #defined in your config
1464 file, the write protection for vendor parameters is
1465 completely disabled. Anybody can change or delete
1468 Alternatively, if you define _both_ an ethaddr in the
1469 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1470 Ethernet address is installed in the environment,
1471 which can be changed exactly ONCE by the user. [The
1472 serial# is unaffected by this, i. e. it remains
1475 The same can be accomplished in a more flexible way
1476 for any variable by configuring the type of access
1477 to allow for those variables in the ".flags" variable
1478 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1483 Define this variable to enable the reservation of
1484 "protected RAM", i. e. RAM which is not overwritten
1485 by U-Boot. Define CONFIG_PRAM to hold the number of
1486 kB you want to reserve for pRAM. You can overwrite
1487 this default value by defining an environment
1488 variable "pram" to the number of kB you want to
1489 reserve. Note that the board info structure will
1490 still show the full amount of RAM. If pRAM is
1491 reserved, a new environment variable "mem" will
1492 automatically be defined to hold the amount of
1493 remaining RAM in a form that can be passed as boot
1494 argument to Linux, for instance like that:
1496 setenv bootargs ... mem=\${mem}
1499 This way you can tell Linux not to use this memory,
1500 either, which results in a memory region that will
1501 not be affected by reboots.
1503 *WARNING* If your board configuration uses automatic
1504 detection of the RAM size, you must make sure that
1505 this memory test is non-destructive. So far, the
1506 following board configurations are known to be
1509 IVMS8, IVML24, SPD8xx,
1510 HERMES, IP860, RPXlite, LWMON,
1516 In the current implementation, the local variables
1517 space and global environment variables space are
1518 separated. Local variables are those you define by
1519 simply typing `name=value'. To access a local
1520 variable later on, you have write `$name' or
1521 `${name}'; to execute the contents of a variable
1522 directly type `$name' at the command prompt.
1524 Global environment variables are those you use
1525 setenv/printenv to work with. To run a command stored
1526 in such a variable, you need to use the run command,
1527 and you must not use the '$' sign to access them.
1529 To store commands and special characters in a
1530 variable, please use double quotation marks
1531 surrounding the whole text of the variable, instead
1532 of the backslashes before semicolons and special
1535 - Default Environment:
1536 CONFIG_EXTRA_ENV_SETTINGS
1538 Define this to contain any number of null terminated
1539 strings (variable = value pairs) that will be part of
1540 the default environment compiled into the boot image.
1542 For example, place something like this in your
1543 board's config file:
1545 #define CONFIG_EXTRA_ENV_SETTINGS \
1549 Warning: This method is based on knowledge about the
1550 internal format how the environment is stored by the
1551 U-Boot code. This is NOT an official, exported
1552 interface! Although it is unlikely that this format
1553 will change soon, there is no guarantee either.
1554 You better know what you are doing here.
1556 Note: overly (ab)use of the default environment is
1557 discouraged. Make sure to check other ways to preset
1558 the environment like the "source" command or the
1561 CONFIG_DELAY_ENVIRONMENT
1563 Normally the environment is loaded when the board is
1564 initialised so that it is available to U-Boot. This inhibits
1565 that so that the environment is not available until
1566 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1567 this is instead controlled by the value of
1568 /config/load-environment.
1570 CONFIG_STANDALONE_LOAD_ADDR
1572 This option defines a board specific value for the
1573 address where standalone program gets loaded, thus
1574 overwriting the architecture dependent default
1577 - Frame Buffer Address:
1580 Define CONFIG_FB_ADDR if you want to use specific
1581 address for frame buffer. This is typically the case
1582 when using a graphics controller has separate video
1583 memory. U-Boot will then place the frame buffer at
1584 the given address instead of dynamically reserving it
1585 in system RAM by calling lcd_setmem(), which grabs
1586 the memory for the frame buffer depending on the
1587 configured panel size.
1589 Please see board_init_f function.
1591 - Automatic software updates via TFTP server
1593 CONFIG_UPDATE_TFTP_CNT_MAX
1594 CONFIG_UPDATE_TFTP_MSEC_MAX
1596 These options enable and control the auto-update feature;
1597 for a more detailed description refer to doc/README.update.
1599 - MTD Support (mtdparts command, UBI support)
1600 CONFIG_MTD_UBI_WL_THRESHOLD
1601 This parameter defines the maximum difference between the highest
1602 erase counter value and the lowest erase counter value of eraseblocks
1603 of UBI devices. When this threshold is exceeded, UBI starts performing
1604 wear leveling by means of moving data from eraseblock with low erase
1605 counter to eraseblocks with high erase counter.
1607 The default value should be OK for SLC NAND flashes, NOR flashes and
1608 other flashes which have eraseblock life-cycle 100000 or more.
1609 However, in case of MLC NAND flashes which typically have eraseblock
1610 life-cycle less than 10000, the threshold should be lessened (e.g.,
1611 to 128 or 256, although it does not have to be power of 2).
1615 CONFIG_MTD_UBI_BEB_LIMIT
1616 This option specifies the maximum bad physical eraseblocks UBI
1617 expects on the MTD device (per 1024 eraseblocks). If the
1618 underlying flash does not admit of bad eraseblocks (e.g. NOR
1619 flash), this value is ignored.
1621 NAND datasheets often specify the minimum and maximum NVM
1622 (Number of Valid Blocks) for the flashes' endurance lifetime.
1623 The maximum expected bad eraseblocks per 1024 eraseblocks
1624 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1625 which gives 20 for most NANDs (MaxNVB is basically the total
1626 count of eraseblocks on the chip).
1628 To put it differently, if this value is 20, UBI will try to
1629 reserve about 1.9% of physical eraseblocks for bad blocks
1630 handling. And that will be 1.9% of eraseblocks on the entire
1631 NAND chip, not just the MTD partition UBI attaches. This means
1632 that if you have, say, a NAND flash chip admits maximum 40 bad
1633 eraseblocks, and it is split on two MTD partitions of the same
1634 size, UBI will reserve 40 eraseblocks when attaching a
1639 CONFIG_MTD_UBI_FASTMAP
1640 Fastmap is a mechanism which allows attaching an UBI device
1641 in nearly constant time. Instead of scanning the whole MTD device it
1642 only has to locate a checkpoint (called fastmap) on the device.
1643 The on-flash fastmap contains all information needed to attach
1644 the device. Using fastmap makes only sense on large devices where
1645 attaching by scanning takes long. UBI will not automatically install
1646 a fastmap on old images, but you can set the UBI parameter
1647 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1648 that fastmap-enabled images are still usable with UBI implementations
1649 without fastmap support. On typical flash devices the whole fastmap
1650 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1652 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1653 Set this parameter to enable fastmap automatically on images
1657 CONFIG_MTD_UBI_FM_DEBUG
1658 Enable UBI fastmap debug
1663 Enable building of SPL globally.
1665 CONFIG_SPL_MAX_FOOTPRINT
1666 Maximum size in memory allocated to the SPL, BSS included.
1667 When defined, the linker checks that the actual memory
1668 used by SPL from _start to __bss_end does not exceed it.
1669 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
1670 must not be both defined at the same time.
1673 Maximum size of the SPL image (text, data, rodata, and
1674 linker lists sections), BSS excluded.
1675 When defined, the linker checks that the actual size does
1678 CONFIG_SPL_RELOC_TEXT_BASE
1679 Address to relocate to. If unspecified, this is equal to
1680 CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
1682 CONFIG_SPL_BSS_START_ADDR
1683 Link address for the BSS within the SPL binary.
1685 CONFIG_SPL_BSS_MAX_SIZE
1686 Maximum size in memory allocated to the SPL BSS.
1687 When defined, the linker checks that the actual memory used
1688 by SPL from __bss_start to __bss_end does not exceed it.
1689 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
1690 must not be both defined at the same time.
1693 Adress of the start of the stack SPL will use
1695 CONFIG_SPL_PANIC_ON_RAW_IMAGE
1696 When defined, SPL will panic() if the image it has
1697 loaded does not have a signature.
1698 Defining this is useful when code which loads images
1699 in SPL cannot guarantee that absolutely all read errors
1701 An example is the LPC32XX MLC NAND driver, which will
1702 consider that a completely unreadable NAND block is bad,
1703 and thus should be skipped silently.
1705 CONFIG_SPL_RELOC_STACK
1706 Adress of the start of the stack SPL will use after
1707 relocation. If unspecified, this is equal to
1710 CONFIG_SYS_SPL_MALLOC_START
1711 Starting address of the malloc pool used in SPL.
1712 When this option is set the full malloc is used in SPL and
1713 it is set up by spl_init() and before that, the simple malloc()
1714 can be used if CONFIG_SYS_MALLOC_F is defined.
1716 CONFIG_SYS_SPL_MALLOC_SIZE
1717 The size of the malloc pool used in SPL.
1719 CONFIG_SPL_DISPLAY_PRINT
1720 For ARM, enable an optional function to print more information
1721 about the running system.
1723 CONFIG_SPL_INIT_MINIMAL
1724 Arch init code should be built for a very small image
1726 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
1727 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
1728 Sector and number of sectors to load kernel argument
1729 parameters from when MMC is being used in raw mode
1732 CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
1733 Filename to read to load U-Boot when reading from filesystem
1735 CONFIG_SPL_FS_LOAD_KERNEL_NAME
1736 Filename to read to load kernel uImage when reading
1737 from filesystem (for Falcon mode)
1739 CONFIG_SPL_FS_LOAD_ARGS_NAME
1740 Filename to read to load kernel argument parameters
1741 when reading from filesystem (for Falcon mode)
1743 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
1744 Set this for NAND SPL on PPC mpc83xx targets, so that
1745 start.S waits for the rest of the SPL to load before
1746 continuing (the hardware starts execution after just
1747 loading the first page rather than the full 4K).
1749 CONFIG_SPL_SKIP_RELOCATE
1750 Avoid SPL relocation
1753 Support for a lightweight UBI (fastmap) scanner and
1756 CONFIG_SPL_NAND_RAW_ONLY
1757 Support to boot only raw u-boot.bin images. Use this only
1758 if you need to save space.
1760 CONFIG_SPL_COMMON_INIT_DDR
1761 Set for common ddr init with serial presence detect in
1764 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
1765 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
1766 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
1767 CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
1768 CONFIG_SYS_NAND_ECCBYTES
1769 Defines the size and behavior of the NAND that SPL uses
1772 CONFIG_SYS_NAND_U_BOOT_DST
1773 Location in memory to load U-Boot to
1775 CONFIG_SYS_NAND_U_BOOT_SIZE
1776 Size of image to load
1778 CONFIG_SYS_NAND_U_BOOT_START
1779 Entry point in loaded image to jump to
1781 CONFIG_SYS_NAND_HW_ECC_OOBFIRST
1782 Define this if you need to first read the OOB and then the
1783 data. This is used, for example, on davinci platforms.
1785 CONFIG_SPL_RAM_DEVICE
1786 Support for running image already present in ram, in SPL binary
1789 Image offset to which the SPL should be padded before appending
1790 the SPL payload. By default, this is defined as
1791 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
1792 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
1793 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
1796 Final target image containing SPL and payload. Some SPLs
1797 use an arch-specific makefile fragment instead, for
1798 example if more than one image needs to be produced.
1800 CONFIG_SPL_FIT_PRINT
1801 Printing information about a FIT image adds quite a bit of
1802 code to SPL. So this is normally disabled in SPL. Use this
1803 option to re-enable it. This will affect the output of the
1804 bootm command when booting a FIT image.
1808 Enable building of TPL globally.
1811 Image offset to which the TPL should be padded before appending
1812 the TPL payload. By default, this is defined as
1813 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
1814 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
1815 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
1817 - Interrupt support (PPC):
1819 There are common interrupt_init() and timer_interrupt()
1820 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
1821 for CPU specific initialization. interrupt_init_cpu()
1822 should set decrementer_count to appropriate value. If
1823 CPU resets decrementer automatically after interrupt
1824 (ppc4xx) it should set decrementer_count to zero.
1825 timer_interrupt() calls timer_interrupt_cpu() for CPU
1826 specific handling. If board has watchdog / status_led
1827 / other_activity_monitor it works automatically from
1828 general timer_interrupt().
1831 Board initialization settings:
1832 ------------------------------
1834 During Initialization u-boot calls a number of board specific functions
1835 to allow the preparation of board specific prerequisites, e.g. pin setup
1836 before drivers are initialized. To enable these callbacks the
1837 following configuration macros have to be defined. Currently this is
1838 architecture specific, so please check arch/your_architecture/lib/board.c
1839 typically in board_init_f() and board_init_r().
1841 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
1842 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
1843 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
1845 Configuration Settings:
1846 -----------------------
1848 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
1849 Optionally it can be defined to support 64-bit memory commands.
1851 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
1852 undefine this when you're short of memory.
1854 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
1855 width of the commands listed in the 'help' command output.
1857 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
1858 prompt for user input.
1860 - CONFIG_SYS_CBSIZE: Buffer size for input from the Console
1862 - CONFIG_SYS_PBSIZE: Buffer size for Console output
1864 - CONFIG_SYS_MAXARGS: max. Number of arguments accepted for monitor commands
1866 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
1867 the application (usually a Linux kernel) when it is
1870 - CONFIG_SYS_BAUDRATE_TABLE:
1871 List of legal baudrate settings for this board.
1873 - CONFIG_SYS_MEM_RESERVE_SECURE
1874 Only implemented for ARMv8 for now.
1875 If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
1876 is substracted from total RAM and won't be reported to OS.
1877 This memory can be used as secure memory. A variable
1878 gd->arch.secure_ram is used to track the location. In systems
1879 the RAM base is not zero, or RAM is divided into banks,
1880 this variable needs to be recalcuated to get the address.
1882 - CONFIG_SYS_MEM_TOP_HIDE:
1883 If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
1884 this specified memory area will get subtracted from the top
1885 (end) of RAM and won't get "touched" at all by U-Boot. By
1886 fixing up gd->ram_size the Linux kernel should gets passed
1887 the now "corrected" memory size and won't touch it either.
1888 This should work for arch/ppc and arch/powerpc. Only Linux
1889 board ports in arch/powerpc with bootwrapper support that
1890 recalculate the memory size from the SDRAM controller setup
1891 will have to get fixed in Linux additionally.
1893 This option can be used as a workaround for the 440EPx/GRx
1894 CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
1897 WARNING: Please make sure that this value is a multiple of
1898 the Linux page size (normally 4k). If this is not the case,
1899 then the end address of the Linux memory will be located at a
1900 non page size aligned address and this could cause major
1903 - CONFIG_SYS_LOADS_BAUD_CHANGE:
1904 Enable temporary baudrate change while serial download
1906 - CONFIG_SYS_SDRAM_BASE:
1907 Physical start address of SDRAM. _Must_ be 0 here.
1909 - CONFIG_SYS_FLASH_BASE:
1910 Physical start address of Flash memory.
1912 - CONFIG_SYS_MONITOR_LEN:
1913 Size of memory reserved for monitor code, used to
1914 determine _at_compile_time_ (!) if the environment is
1915 embedded within the U-Boot image, or in a separate
1918 - CONFIG_SYS_MALLOC_LEN:
1919 Size of DRAM reserved for malloc() use.
1921 - CONFIG_SYS_MALLOC_F_LEN
1922 Size of the malloc() pool for use before relocation. If
1923 this is defined, then a very simple malloc() implementation
1924 will become available before relocation. The address is just
1925 below the global data, and the stack is moved down to make
1928 This feature allocates regions with increasing addresses
1929 within the region. calloc() is supported, but realloc()
1930 is not available. free() is supported but does nothing.
1931 The memory will be freed (or in fact just forgotten) when
1932 U-Boot relocates itself.
1934 - CONFIG_SYS_MALLOC_SIMPLE
1935 Provides a simple and small malloc() and calloc() for those
1936 boards which do not use the full malloc in SPL (which is
1937 enabled with CONFIG_SYS_SPL_MALLOC_START).
1939 - CONFIG_SYS_NONCACHED_MEMORY:
1940 Size of non-cached memory area. This area of memory will be
1941 typically located right below the malloc() area and mapped
1942 uncached in the MMU. This is useful for drivers that would
1943 otherwise require a lot of explicit cache maintenance. For
1944 some drivers it's also impossible to properly maintain the
1945 cache. For example if the regions that need to be flushed
1946 are not a multiple of the cache-line size, *and* padding
1947 cannot be allocated between the regions to align them (i.e.
1948 if the HW requires a contiguous array of regions, and the
1949 size of each region is not cache-aligned), then a flush of
1950 one region may result in overwriting data that hardware has
1951 written to another region in the same cache-line. This can
1952 happen for example in network drivers where descriptors for
1953 buffers are typically smaller than the CPU cache-line (e.g.
1954 16 bytes vs. 32 or 64 bytes).
1956 Non-cached memory is only supported on 32-bit ARM at present.
1958 - CONFIG_SYS_BOOTM_LEN:
1959 Normally compressed uImages are limited to an
1960 uncompressed size of 8 MBytes. If this is not enough,
1961 you can define CONFIG_SYS_BOOTM_LEN in your board config file
1962 to adjust this setting to your needs.
1964 - CONFIG_SYS_BOOTMAPSZ:
1965 Maximum size of memory mapped by the startup code of
1966 the Linux kernel; all data that must be processed by
1967 the Linux kernel (bd_info, boot arguments, FDT blob if
1968 used) must be put below this limit, unless "bootm_low"
1969 environment variable is defined and non-zero. In such case
1970 all data for the Linux kernel must be between "bootm_low"
1971 and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
1972 variable "bootm_mapsize" will override the value of
1973 CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
1974 then the value in "bootm_size" will be used instead.
1976 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
1977 Enable initrd_high functionality. If defined then the
1978 initrd_high feature is enabled and the bootm ramdisk subcommand
1981 - CONFIG_SYS_BOOT_GET_CMDLINE:
1982 Enables allocating and saving kernel cmdline in space between
1983 "bootm_low" and "bootm_low" + BOOTMAPSZ.
1985 - CONFIG_SYS_BOOT_GET_KBD:
1986 Enables allocating and saving a kernel copy of the bd_info in
1987 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
1989 - CONFIG_SYS_MAX_FLASH_SECT:
1990 Max number of sectors on a Flash chip
1992 - CONFIG_SYS_FLASH_ERASE_TOUT:
1993 Timeout for Flash erase operations (in ms)
1995 - CONFIG_SYS_FLASH_WRITE_TOUT:
1996 Timeout for Flash write operations (in ms)
1998 - CONFIG_SYS_FLASH_LOCK_TOUT
1999 Timeout for Flash set sector lock bit operation (in ms)
2001 - CONFIG_SYS_FLASH_UNLOCK_TOUT
2002 Timeout for Flash clear lock bits operation (in ms)
2004 - CONFIG_SYS_FLASH_PROTECTION
2005 If defined, hardware flash sectors protection is used
2006 instead of U-Boot software protection.
2008 - CONFIG_SYS_DIRECT_FLASH_TFTP:
2010 Enable TFTP transfers directly to flash memory;
2011 without this option such a download has to be
2012 performed in two steps: (1) download to RAM, and (2)
2013 copy from RAM to flash.
2015 The two-step approach is usually more reliable, since
2016 you can check if the download worked before you erase
2017 the flash, but in some situations (when system RAM is
2018 too limited to allow for a temporary copy of the
2019 downloaded image) this option may be very useful.
2021 - CONFIG_SYS_FLASH_CFI:
2022 Define if the flash driver uses extra elements in the
2023 common flash structure for storing flash geometry.
2025 - CONFIG_FLASH_CFI_DRIVER
2026 This option also enables the building of the cfi_flash driver
2027 in the drivers directory
2029 - CONFIG_FLASH_CFI_MTD
2030 This option enables the building of the cfi_mtd driver
2031 in the drivers directory. The driver exports CFI flash
2034 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2035 Use buffered writes to flash.
2037 - CONFIG_FLASH_SPANSION_S29WS_N
2038 s29ws-n MirrorBit flash has non-standard addresses for buffered
2041 - CONFIG_SYS_FLASH_QUIET_TEST
2042 If this option is defined, the common CFI flash doesn't
2043 print it's warning upon not recognized FLASH banks. This
2044 is useful, if some of the configured banks are only
2045 optionally available.
2047 - CONFIG_FLASH_SHOW_PROGRESS
2048 If defined (must be an integer), print out countdown
2049 digits and dots. Recommended value: 45 (9..1) for 80
2050 column displays, 15 (3..1) for 40 column displays.
2052 - CONFIG_FLASH_VERIFY
2053 If defined, the content of the flash (destination) is compared
2054 against the source after the write operation. An error message
2055 will be printed when the contents are not identical.
2056 Please note that this option is useless in nearly all cases,
2057 since such flash programming errors usually are detected earlier
2058 while unprotecting/erasing/programming. Please only enable
2059 this option if you really know what you are doing.
2061 - CONFIG_ENV_MAX_ENTRIES
2063 Maximum number of entries in the hash table that is used
2064 internally to store the environment settings. The default
2065 setting is supposed to be generous and should work in most
2066 cases. This setting can be used to tune behaviour; see
2067 lib/hashtable.c for details.
2069 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2070 - CONFIG_ENV_FLAGS_LIST_STATIC
2071 Enable validation of the values given to environment variables when
2072 calling env set. Variables can be restricted to only decimal,
2073 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
2074 the variables can also be restricted to IP address or MAC address.
2076 The format of the list is:
2077 type_attribute = [s|d|x|b|i|m]
2078 access_attribute = [a|r|o|c]
2079 attributes = type_attribute[access_attribute]
2080 entry = variable_name[:attributes]
2083 The type attributes are:
2084 s - String (default)
2087 b - Boolean ([1yYtT|0nNfF])
2091 The access attributes are:
2097 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2098 Define this to a list (string) to define the ".flags"
2099 environment variable in the default or embedded environment.
2101 - CONFIG_ENV_FLAGS_LIST_STATIC
2102 Define this to a list (string) to define validation that
2103 should be done if an entry is not found in the ".flags"
2104 environment variable. To override a setting in the static
2105 list, simply add an entry for the same variable name to the
2108 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2109 regular expression. This allows multiple variables to define the same
2110 flags without explicitly listing them for each variable.
2112 The following definitions that deal with the placement and management
2113 of environment data (variable area); in general, we support the
2114 following configurations:
2116 - CONFIG_BUILD_ENVCRC:
2118 Builds up envcrc with the target environment so that external utils
2119 may easily extract it and embed it in final U-Boot images.
2121 BE CAREFUL! The first access to the environment happens quite early
2122 in U-Boot initialization (when we try to get the setting of for the
2123 console baudrate). You *MUST* have mapped your NVRAM area then, or
2126 Please note that even with NVRAM we still use a copy of the
2127 environment in RAM: we could work on NVRAM directly, but we want to
2128 keep settings there always unmodified except somebody uses "saveenv"
2129 to save the current settings.
2131 BE CAREFUL! For some special cases, the local device can not use
2132 "saveenv" command. For example, the local device will get the
2133 environment stored in a remote NOR flash by SRIO or PCIE link,
2134 but it can not erase, write this NOR flash by SRIO or PCIE interface.
2136 - CONFIG_NAND_ENV_DST
2138 Defines address in RAM to which the nand_spl code should copy the
2139 environment. If redundant environment is used, it will be copied to
2140 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2142 Please note that the environment is read-only until the monitor
2143 has been relocated to RAM and a RAM copy of the environment has been
2144 created; also, when using EEPROM you will have to use env_get_f()
2145 until then to read environment variables.
2147 The environment is protected by a CRC32 checksum. Before the monitor
2148 is relocated into RAM, as a result of a bad CRC you will be working
2149 with the compiled-in default environment - *silently*!!! [This is
2150 necessary, because the first environment variable we need is the
2151 "baudrate" setting for the console - if we have a bad CRC, we don't
2152 have any device yet where we could complain.]
2154 Note: once the monitor has been relocated, then it will complain if
2155 the default environment is used; a new CRC is computed as soon as you
2156 use the "saveenv" command to store a valid environment.
2158 - CONFIG_SYS_FAULT_MII_ADDR:
2159 MII address of the PHY to check for the Ethernet link state.
2161 - CONFIG_NS16550_MIN_FUNCTIONS:
2162 Define this if you desire to only have use of the NS16550_init
2163 and NS16550_putc functions for the serial driver located at
2164 drivers/serial/ns16550.c. This option is useful for saving
2165 space for already greatly restricted images, including but not
2166 limited to NAND_SPL configurations.
2168 - CONFIG_DISPLAY_BOARDINFO
2169 Display information about the board that U-Boot is running on
2170 when U-Boot starts up. The board function checkboard() is called
2173 - CONFIG_DISPLAY_BOARDINFO_LATE
2174 Similar to the previous option, but display this information
2175 later, once stdio is running and output goes to the LCD, if
2178 Low Level (hardware related) configuration options:
2179 ---------------------------------------------------
2181 - CONFIG_SYS_CACHELINE_SIZE:
2182 Cache Line Size of the CPU.
2184 - CONFIG_SYS_CCSRBAR_DEFAULT:
2185 Default (power-on reset) physical address of CCSR on Freescale
2188 - CONFIG_SYS_CCSRBAR:
2189 Virtual address of CCSR. On a 32-bit build, this is typically
2190 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2192 - CONFIG_SYS_CCSRBAR_PHYS:
2193 Physical address of CCSR. CCSR can be relocated to a new
2194 physical address, if desired. In this case, this macro should
2195 be set to that address. Otherwise, it should be set to the
2196 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
2197 is typically relocated on 36-bit builds. It is recommended
2198 that this macro be defined via the _HIGH and _LOW macros:
2200 #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2201 * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2203 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2204 Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
2205 either 0 (32-bit build) or 0xF (36-bit build). This macro is
2206 used in assembly code, so it must not contain typecasts or
2207 integer size suffixes (e.g. "ULL").
2209 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
2210 Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
2211 used in assembly code, so it must not contain typecasts or
2212 integer size suffixes (e.g. "ULL").
2214 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2215 If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2216 forced to a value that ensures that CCSR is not relocated.
2218 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
2219 DO NOT CHANGE unless you know exactly what you're
2220 doing! (11-4) [MPC8xx systems only]
2222 - CONFIG_SYS_INIT_RAM_ADDR:
2224 Start address of memory area that can be used for
2225 initial data and stack; please note that this must be
2226 writable memory that is working WITHOUT special
2227 initialization, i. e. you CANNOT use normal RAM which
2228 will become available only after programming the
2229 memory controller and running certain initialization
2232 U-Boot uses the following memory types:
2233 - MPC8xx: IMMR (internal memory of the CPU)
2235 - CONFIG_SYS_GBL_DATA_OFFSET:
2237 Offset of the initial data structure in the memory
2238 area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2239 CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2240 data is located at the end of the available space
2241 (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2242 GENERATED_GBL_DATA_SIZE), and the initial stack is just
2243 below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2244 CONFIG_SYS_GBL_DATA_OFFSET) downward.
2247 On the MPC824X (or other systems that use the data
2248 cache for initial memory) the address chosen for
2249 CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2250 point to an otherwise UNUSED address space between
2251 the top of RAM and the start of the PCI space.
2253 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
2255 - CONFIG_SYS_OR_TIMING_SDRAM:
2258 - CONFIG_SYS_MAMR_PTA:
2259 periodic timer for refresh
2262 Chip has SRIO or not
2265 Board has SRIO 1 port available
2268 Board has SRIO 2 port available
2270 - CONFIG_SRIO_PCIE_BOOT_MASTER
2271 Board can support master function for Boot from SRIO and PCIE
2273 - CONFIG_SYS_SRIOn_MEM_VIRT:
2274 Virtual Address of SRIO port 'n' memory region
2276 - CONFIG_SYS_SRIOn_MEM_PHYxS:
2277 Physical Address of SRIO port 'n' memory region
2279 - CONFIG_SYS_SRIOn_MEM_SIZE:
2280 Size of SRIO port 'n' memory region
2282 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
2283 Defined to tell the NAND controller that the NAND chip is using
2285 Not all NAND drivers use this symbol.
2286 Example of drivers that use it:
2287 - drivers/mtd/nand/raw/ndfc.c
2288 - drivers/mtd/nand/raw/mxc_nand.c
2290 - CONFIG_SYS_NDFC_EBC0_CFG
2291 Sets the EBC0_CFG register for the NDFC. If not defined
2292 a default value will be used.
2295 Get DDR timing information from an I2C EEPROM. Common
2296 with pluggable memory modules such as SODIMMs
2299 I2C address of the SPD EEPROM
2301 - CONFIG_SYS_SPD_BUS_NUM
2302 If SPD EEPROM is on an I2C bus other than the first
2303 one, specify here. Note that the value must resolve
2304 to something your driver can deal with.
2306 - CONFIG_SYS_DDR_RAW_TIMING
2307 Get DDR timing information from other than SPD. Common with
2308 soldered DDR chips onboard without SPD. DDR raw timing
2309 parameters are extracted from datasheet and hard-coded into
2310 header files or board specific files.
2312 - CONFIG_FSL_DDR_INTERACTIVE
2313 Enable interactive DDR debugging. See doc/README.fsl-ddr.
2315 - CONFIG_FSL_DDR_SYNC_REFRESH
2316 Enable sync of refresh for multiple controllers.
2318 - CONFIG_FSL_DDR_BIST
2319 Enable built-in memory test for Freescale DDR controllers.
2321 - CONFIG_SYS_83XX_DDR_USES_CS0
2322 Only for 83xx systems. If specified, then DDR should
2323 be configured using CS0 and CS1 instead of CS2 and CS3.
2326 Enable RMII mode for all FECs.
2327 Note that this is a global option, we can't
2328 have one FEC in standard MII mode and another in RMII mode.
2330 - CONFIG_CRC32_VERIFY
2331 Add a verify option to the crc32 command.
2334 => crc32 -v <address> <count> <crc32>
2336 Where address/count indicate a memory area
2337 and crc32 is the correct crc32 which the
2341 Add the "loopw" memory command. This only takes effect if
2342 the memory commands are activated globally (CONFIG_CMD_MEMORY).
2344 - CONFIG_CMD_MX_CYCLIC
2345 Add the "mdc" and "mwc" memory commands. These are cyclic
2350 This command will print 4 bytes (10,11,12,13) each 500 ms.
2352 => mwc.l 100 12345678 10
2353 This command will write 12345678 to address 100 all 10 ms.
2355 This only takes effect if the memory commands are activated
2356 globally (CONFIG_CMD_MEMORY).
2359 Set when the currently-running compilation is for an artifact
2360 that will end up in the SPL (as opposed to the TPL or U-Boot
2361 proper). Code that needs stage-specific behavior should check
2365 Set when the currently-running compilation is for an artifact
2366 that will end up in the TPL (as opposed to the SPL or U-Boot
2367 proper). Code that needs stage-specific behavior should check
2370 - CONFIG_SYS_MPC85XX_NO_RESETVEC
2371 Only for 85xx systems. If this variable is specified, the section
2372 .resetvec is not kept and the section .bootpg is placed in the
2373 previous 4k of the .text section.
2375 - CONFIG_ARCH_MAP_SYSMEM
2376 Generally U-Boot (and in particular the md command) uses
2377 effective address. It is therefore not necessary to regard
2378 U-Boot address as virtual addresses that need to be translated
2379 to physical addresses. However, sandbox requires this, since
2380 it maintains its own little RAM buffer which contains all
2381 addressable memory. This option causes some memory accesses
2382 to be mapped through map_sysmem() / unmap_sysmem().
2384 - CONFIG_X86_RESET_VECTOR
2385 If defined, the x86 reset vector code is included. This is not
2386 needed when U-Boot is running from Coreboot.
2388 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
2389 Option to disable subpage write in NAND driver
2390 driver that uses this:
2391 drivers/mtd/nand/raw/davinci_nand.c
2393 Freescale QE/FMAN Firmware Support:
2394 -----------------------------------
2396 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
2397 loading of "firmware", which is encoded in the QE firmware binary format.
2398 This firmware often needs to be loaded during U-Boot booting, so macros
2399 are used to identify the storage device (NOR flash, SPI, etc) and the address
2402 - CONFIG_SYS_FMAN_FW_ADDR
2403 The address in the storage device where the FMAN microcode is located. The
2404 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2407 - CONFIG_SYS_QE_FW_ADDR
2408 The address in the storage device where the QE microcode is located. The
2409 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2412 - CONFIG_SYS_QE_FMAN_FW_LENGTH
2413 The maximum possible size of the firmware. The firmware binary format
2414 has a field that specifies the actual size of the firmware, but it
2415 might not be possible to read any part of the firmware unless some
2416 local storage is allocated to hold the entire firmware first.
2418 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
2419 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
2420 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
2421 virtual address in NOR flash.
2423 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
2424 Specifies that QE/FMAN firmware is located in NAND flash.
2425 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
2427 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
2428 Specifies that QE/FMAN firmware is located on the primary SD/MMC
2429 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
2431 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
2432 Specifies that QE/FMAN firmware is located in the remote (master)
2433 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
2434 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
2435 window->master inbound window->master LAW->the ucode address in
2436 master's memory space.
2438 Freescale Layerscape Management Complex Firmware Support:
2439 ---------------------------------------------------------
2440 The Freescale Layerscape Management Complex (MC) supports the loading of
2442 This firmware often needs to be loaded during U-Boot booting, so macros
2443 are used to identify the storage device (NOR flash, SPI, etc) and the address
2446 - CONFIG_FSL_MC_ENET
2447 Enable the MC driver for Layerscape SoCs.
2449 Freescale Layerscape Debug Server Support:
2450 -------------------------------------------
2451 The Freescale Layerscape Debug Server Support supports the loading of
2452 "Debug Server firmware" and triggering SP boot-rom.
2453 This firmware often needs to be loaded during U-Boot booting.
2455 - CONFIG_SYS_MC_RSV_MEM_ALIGN
2456 Define alignment of reserved memory MC requires
2461 In order to achieve reproducible builds, timestamps used in the U-Boot build
2462 process have to be set to a fixed value.
2464 This is done using the SOURCE_DATE_EPOCH environment variable.
2465 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
2466 option for U-Boot or an environment variable in U-Boot.
2468 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
2470 Building the Software:
2471 ======================
2473 Building U-Boot has been tested in several native build environments
2474 and in many different cross environments. Of course we cannot support
2475 all possibly existing versions of cross development tools in all
2476 (potentially obsolete) versions. In case of tool chain problems we
2477 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
2478 which is extensively used to build and test U-Boot.
2480 If you are not using a native environment, it is assumed that you
2481 have GNU cross compiling tools available in your path. In this case,
2482 you must set the environment variable CROSS_COMPILE in your shell.
2483 Note that no changes to the Makefile or any other source files are
2484 necessary. For example using the ELDK on a 4xx CPU, please enter:
2486 $ CROSS_COMPILE=ppc_4xx-
2487 $ export CROSS_COMPILE
2489 U-Boot is intended to be simple to build. After installing the
2490 sources you must configure U-Boot for one specific board type. This
2495 where "NAME_defconfig" is the name of one of the existing configu-
2496 rations; see configs/*_defconfig for supported names.
2498 Note: for some boards special configuration names may exist; check if
2499 additional information is available from the board vendor; for
2500 instance, the TQM823L systems are available without (standard)
2501 or with LCD support. You can select such additional "features"
2502 when choosing the configuration, i. e.
2504 make TQM823L_defconfig
2505 - will configure for a plain TQM823L, i. e. no LCD support
2507 make TQM823L_LCD_defconfig
2508 - will configure for a TQM823L with U-Boot console on LCD
2513 Finally, type "make all", and you should get some working U-Boot
2514 images ready for download to / installation on your system:
2516 - "u-boot.bin" is a raw binary image
2517 - "u-boot" is an image in ELF binary format
2518 - "u-boot.srec" is in Motorola S-Record format
2520 By default the build is performed locally and the objects are saved
2521 in the source directory. One of the two methods can be used to change
2522 this behavior and build U-Boot to some external directory:
2524 1. Add O= to the make command line invocations:
2526 make O=/tmp/build distclean
2527 make O=/tmp/build NAME_defconfig
2528 make O=/tmp/build all
2530 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
2532 export KBUILD_OUTPUT=/tmp/build
2537 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
2540 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
2541 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
2542 For example to treat all compiler warnings as errors:
2544 make KCFLAGS=-Werror
2546 Please be aware that the Makefiles assume you are using GNU make, so
2547 for instance on NetBSD you might need to use "gmake" instead of
2551 If the system board that you have is not listed, then you will need
2552 to port U-Boot to your hardware platform. To do this, follow these
2555 1. Create a new directory to hold your board specific code. Add any
2556 files you need. In your board directory, you will need at least
2557 the "Makefile" and a "<board>.c".
2558 2. Create a new configuration file "include/configs/<board>.h" for
2560 3. If you're porting U-Boot to a new CPU, then also create a new
2561 directory to hold your CPU specific code. Add any files you need.
2562 4. Run "make <board>_defconfig" with your new name.
2563 5. Type "make", and you should get a working "u-boot.srec" file
2564 to be installed on your target system.
2565 6. Debug and solve any problems that might arise.
2566 [Of course, this last step is much harder than it sounds.]
2569 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
2570 ==============================================================
2572 If you have modified U-Boot sources (for instance added a new board
2573 or support for new devices, a new CPU, etc.) you are expected to
2574 provide feedback to the other developers. The feedback normally takes
2575 the form of a "patch", i.e. a context diff against a certain (latest
2576 official or latest in the git repository) version of U-Boot sources.
2578 But before you submit such a patch, please verify that your modifi-
2579 cation did not break existing code. At least make sure that *ALL* of
2580 the supported boards compile WITHOUT ANY compiler warnings. To do so,
2581 just run the buildman script (tools/buildman/buildman), which will
2582 configure and build U-Boot for ALL supported system. Be warned, this
2583 will take a while. Please see the buildman README, or run 'buildman -H'
2587 See also "U-Boot Porting Guide" below.
2590 Monitor Commands - Overview:
2591 ============================
2593 go - start application at address 'addr'
2594 run - run commands in an environment variable
2595 bootm - boot application image from memory
2596 bootp - boot image via network using BootP/TFTP protocol
2597 bootz - boot zImage from memory
2598 tftpboot- boot image via network using TFTP protocol
2599 and env variables "ipaddr" and "serverip"
2600 (and eventually "gatewayip")
2601 tftpput - upload a file via network using TFTP protocol
2602 rarpboot- boot image via network using RARP/TFTP protocol
2603 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
2604 loads - load S-Record file over serial line
2605 loadb - load binary file over serial line (kermit mode)
2607 mm - memory modify (auto-incrementing)
2608 nm - memory modify (constant address)
2609 mw - memory write (fill)
2612 cmp - memory compare
2613 crc32 - checksum calculation
2614 i2c - I2C sub-system
2615 sspi - SPI utility commands
2616 base - print or set address offset
2617 printenv- print environment variables
2618 pwm - control pwm channels
2619 setenv - set environment variables
2620 saveenv - save environment variables to persistent storage
2621 protect - enable or disable FLASH write protection
2622 erase - erase FLASH memory
2623 flinfo - print FLASH memory information
2624 nand - NAND memory operations (see doc/README.nand)
2625 bdinfo - print Board Info structure
2626 iminfo - print header information for application image
2627 coninfo - print console devices and informations
2628 ide - IDE sub-system
2629 loop - infinite loop on address range
2630 loopw - infinite write loop on address range
2631 mtest - simple RAM test
2632 icache - enable or disable instruction cache
2633 dcache - enable or disable data cache
2634 reset - Perform RESET of the CPU
2635 echo - echo args to console
2636 version - print monitor version
2637 help - print online help
2638 ? - alias for 'help'
2641 Monitor Commands - Detailed Description:
2642 ========================================
2646 For now: just type "help <command>".
2649 Note for Redundant Ethernet Interfaces:
2650 =======================================
2652 Some boards come with redundant Ethernet interfaces; U-Boot supports
2653 such configurations and is capable of automatic selection of a
2654 "working" interface when needed. MAC assignment works as follows:
2656 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
2657 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
2658 "eth1addr" (=>eth1), "eth2addr", ...
2660 If the network interface stores some valid MAC address (for instance
2661 in SROM), this is used as default address if there is NO correspon-
2662 ding setting in the environment; if the corresponding environment
2663 variable is set, this overrides the settings in the card; that means:
2665 o If the SROM has a valid MAC address, and there is no address in the
2666 environment, the SROM's address is used.
2668 o If there is no valid address in the SROM, and a definition in the
2669 environment exists, then the value from the environment variable is
2672 o If both the SROM and the environment contain a MAC address, and
2673 both addresses are the same, this MAC address is used.
2675 o If both the SROM and the environment contain a MAC address, and the
2676 addresses differ, the value from the environment is used and a
2679 o If neither SROM nor the environment contain a MAC address, an error
2680 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
2681 a random, locally-assigned MAC is used.
2683 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
2684 will be programmed into hardware as part of the initialization process. This
2685 may be skipped by setting the appropriate 'ethmacskip' environment variable.
2686 The naming convention is as follows:
2687 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
2692 U-Boot is capable of booting (and performing other auxiliary operations on)
2693 images in two formats:
2695 New uImage format (FIT)
2696 -----------------------
2698 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
2699 to Flattened Device Tree). It allows the use of images with multiple
2700 components (several kernels, ramdisks, etc.), with contents protected by
2701 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
2707 Old image format is based on binary files which can be basically anything,
2708 preceded by a special header; see the definitions in include/image.h for
2709 details; basically, the header defines the following image properties:
2711 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
2712 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
2713 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
2714 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
2715 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
2716 IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
2717 Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
2718 * Compression Type (uncompressed, gzip, bzip2)
2724 The header is marked by a special Magic Number, and both the header
2725 and the data portions of the image are secured against corruption by
2732 Although U-Boot should support any OS or standalone application
2733 easily, the main focus has always been on Linux during the design of
2736 U-Boot includes many features that so far have been part of some
2737 special "boot loader" code within the Linux kernel. Also, any
2738 "initrd" images to be used are no longer part of one big Linux image;
2739 instead, kernel and "initrd" are separate images. This implementation
2740 serves several purposes:
2742 - the same features can be used for other OS or standalone
2743 applications (for instance: using compressed images to reduce the
2744 Flash memory footprint)
2746 - it becomes much easier to port new Linux kernel versions because
2747 lots of low-level, hardware dependent stuff are done by U-Boot
2749 - the same Linux kernel image can now be used with different "initrd"
2750 images; of course this also means that different kernel images can
2751 be run with the same "initrd". This makes testing easier (you don't
2752 have to build a new "zImage.initrd" Linux image when you just
2753 change a file in your "initrd"). Also, a field-upgrade of the
2754 software is easier now.
2760 Porting Linux to U-Boot based systems:
2761 ---------------------------------------
2763 U-Boot cannot save you from doing all the necessary modifications to
2764 configure the Linux device drivers for use with your target hardware
2765 (no, we don't intend to provide a full virtual machine interface to
2768 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
2770 Just make sure your machine specific header file (for instance
2771 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2772 Information structure as we define in include/asm-<arch>/u-boot.h,
2773 and make sure that your definition of IMAP_ADDR uses the same value
2774 as your U-Boot configuration in CONFIG_SYS_IMMR.
2776 Note that U-Boot now has a driver model, a unified model for drivers.
2777 If you are adding a new driver, plumb it into driver model. If there
2778 is no uclass available, you are encouraged to create one. See
2782 Configuring the Linux kernel:
2783 -----------------------------
2785 No specific requirements for U-Boot. Make sure you have some root
2786 device (initial ramdisk, NFS) for your target system.
2789 Building a Linux Image:
2790 -----------------------
2792 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2793 not used. If you use recent kernel source, a new build target
2794 "uImage" will exist which automatically builds an image usable by
2795 U-Boot. Most older kernels also have support for a "pImage" target,
2796 which was introduced for our predecessor project PPCBoot and uses a
2797 100% compatible format.
2801 make TQM850L_defconfig
2806 The "uImage" build target uses a special tool (in 'tools/mkimage') to
2807 encapsulate a compressed Linux kernel image with header information,
2808 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2810 * build a standard "vmlinux" kernel image (in ELF binary format):
2812 * convert the kernel into a raw binary image:
2814 ${CROSS_COMPILE}-objcopy -O binary \
2815 -R .note -R .comment \
2816 -S vmlinux linux.bin
2818 * compress the binary image:
2822 * package compressed binary image for U-Boot:
2824 mkimage -A ppc -O linux -T kernel -C gzip \
2825 -a 0 -e 0 -n "Linux Kernel Image" \
2826 -d linux.bin.gz uImage
2829 The "mkimage" tool can also be used to create ramdisk images for use
2830 with U-Boot, either separated from the Linux kernel image, or
2831 combined into one file. "mkimage" encapsulates the images with a 64
2832 byte header containing information about target architecture,
2833 operating system, image type, compression method, entry points, time
2834 stamp, CRC32 checksums, etc.
2836 "mkimage" can be called in two ways: to verify existing images and
2837 print the header information, or to build new images.
2839 In the first form (with "-l" option) mkimage lists the information
2840 contained in the header of an existing U-Boot image; this includes
2841 checksum verification:
2843 tools/mkimage -l image
2844 -l ==> list image header information
2846 The second form (with "-d" option) is used to build a U-Boot image
2847 from a "data file" which is used as image payload:
2849 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
2850 -n name -d data_file image
2851 -A ==> set architecture to 'arch'
2852 -O ==> set operating system to 'os'
2853 -T ==> set image type to 'type'
2854 -C ==> set compression type 'comp'
2855 -a ==> set load address to 'addr' (hex)
2856 -e ==> set entry point to 'ep' (hex)
2857 -n ==> set image name to 'name'
2858 -d ==> use image data from 'datafile'
2860 Right now, all Linux kernels for PowerPC systems use the same load
2861 address (0x00000000), but the entry point address depends on the
2864 - 2.2.x kernels have the entry point at 0x0000000C,
2865 - 2.3.x and later kernels have the entry point at 0x00000000.
2867 So a typical call to build a U-Boot image would read:
2869 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2870 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
2871 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
2872 > examples/uImage.TQM850L
2873 Image Name: 2.4.4 kernel for TQM850L
2874 Created: Wed Jul 19 02:34:59 2000
2875 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2876 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2877 Load Address: 0x00000000
2878 Entry Point: 0x00000000
2880 To verify the contents of the image (or check for corruption):
2882 -> tools/mkimage -l examples/uImage.TQM850L
2883 Image Name: 2.4.4 kernel for TQM850L
2884 Created: Wed Jul 19 02:34:59 2000
2885 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2886 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2887 Load Address: 0x00000000
2888 Entry Point: 0x00000000
2890 NOTE: for embedded systems where boot time is critical you can trade
2891 speed for memory and install an UNCOMPRESSED image instead: this
2892 needs more space in Flash, but boots much faster since it does not
2893 need to be uncompressed:
2895 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
2896 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2897 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
2898 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
2899 > examples/uImage.TQM850L-uncompressed
2900 Image Name: 2.4.4 kernel for TQM850L
2901 Created: Wed Jul 19 02:34:59 2000
2902 Image Type: PowerPC Linux Kernel Image (uncompressed)
2903 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
2904 Load Address: 0x00000000
2905 Entry Point: 0x00000000
2908 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
2909 when your kernel is intended to use an initial ramdisk:
2911 -> tools/mkimage -n 'Simple Ramdisk Image' \
2912 > -A ppc -O linux -T ramdisk -C gzip \
2913 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
2914 Image Name: Simple Ramdisk Image
2915 Created: Wed Jan 12 14:01:50 2000
2916 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2917 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
2918 Load Address: 0x00000000
2919 Entry Point: 0x00000000
2921 The "dumpimage" tool can be used to disassemble or list the contents of images
2922 built by mkimage. See dumpimage's help output (-h) for details.
2924 Installing a Linux Image:
2925 -------------------------
2927 To downloading a U-Boot image over the serial (console) interface,
2928 you must convert the image to S-Record format:
2930 objcopy -I binary -O srec examples/image examples/image.srec
2932 The 'objcopy' does not understand the information in the U-Boot
2933 image header, so the resulting S-Record file will be relative to
2934 address 0x00000000. To load it to a given address, you need to
2935 specify the target address as 'offset' parameter with the 'loads'
2938 Example: install the image to address 0x40100000 (which on the
2939 TQM8xxL is in the first Flash bank):
2941 => erase 40100000 401FFFFF
2947 ## Ready for S-Record download ...
2948 ~>examples/image.srec
2949 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
2951 15989 15990 15991 15992
2952 [file transfer complete]
2954 ## Start Addr = 0x00000000
2957 You can check the success of the download using the 'iminfo' command;
2958 this includes a checksum verification so you can be sure no data
2959 corruption happened:
2963 ## Checking Image at 40100000 ...
2964 Image Name: 2.2.13 for initrd on TQM850L
2965 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2966 Data Size: 335725 Bytes = 327 kB = 0 MB
2967 Load Address: 00000000
2968 Entry Point: 0000000c
2969 Verifying Checksum ... OK
2975 The "bootm" command is used to boot an application that is stored in
2976 memory (RAM or Flash). In case of a Linux kernel image, the contents
2977 of the "bootargs" environment variable is passed to the kernel as
2978 parameters. You can check and modify this variable using the
2979 "printenv" and "setenv" commands:
2982 => printenv bootargs
2983 bootargs=root=/dev/ram
2985 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2987 => printenv bootargs
2988 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2991 ## Booting Linux kernel at 40020000 ...
2992 Image Name: 2.2.13 for NFS on TQM850L
2993 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2994 Data Size: 381681 Bytes = 372 kB = 0 MB
2995 Load Address: 00000000
2996 Entry Point: 0000000c
2997 Verifying Checksum ... OK
2998 Uncompressing Kernel Image ... OK
2999 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
3000 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3001 time_init: decrementer frequency = 187500000/60
3002 Calibrating delay loop... 49.77 BogoMIPS
3003 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3006 If you want to boot a Linux kernel with initial RAM disk, you pass
3007 the memory addresses of both the kernel and the initrd image (PPBCOOT
3008 format!) to the "bootm" command:
3010 => imi 40100000 40200000
3012 ## Checking Image at 40100000 ...
3013 Image Name: 2.2.13 for initrd on TQM850L
3014 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3015 Data Size: 335725 Bytes = 327 kB = 0 MB
3016 Load Address: 00000000
3017 Entry Point: 0000000c
3018 Verifying Checksum ... OK
3020 ## Checking Image at 40200000 ...
3021 Image Name: Simple Ramdisk Image
3022 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3023 Data Size: 566530 Bytes = 553 kB = 0 MB
3024 Load Address: 00000000
3025 Entry Point: 00000000
3026 Verifying Checksum ... OK
3028 => bootm 40100000 40200000
3029 ## Booting Linux kernel at 40100000 ...
3030 Image Name: 2.2.13 for initrd on TQM850L
3031 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3032 Data Size: 335725 Bytes = 327 kB = 0 MB
3033 Load Address: 00000000
3034 Entry Point: 0000000c
3035 Verifying Checksum ... OK
3036 Uncompressing Kernel Image ... OK
3037 ## Loading RAMDisk Image at 40200000 ...
3038 Image Name: Simple Ramdisk Image
3039 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3040 Data Size: 566530 Bytes = 553 kB = 0 MB
3041 Load Address: 00000000
3042 Entry Point: 00000000
3043 Verifying Checksum ... OK
3044 Loading Ramdisk ... OK
3045 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
3046 Boot arguments: root=/dev/ram
3047 time_init: decrementer frequency = 187500000/60
3048 Calibrating delay loop... 49.77 BogoMIPS
3050 RAMDISK: Compressed image found at block 0
3051 VFS: Mounted root (ext2 filesystem).
3055 Boot Linux and pass a flat device tree:
3058 First, U-Boot must be compiled with the appropriate defines. See the section
3059 titled "Linux Kernel Interface" above for a more in depth explanation. The
3060 following is an example of how to start a kernel and pass an updated
3066 oft=oftrees/mpc8540ads.dtb
3067 => tftp $oftaddr $oft
3068 Speed: 1000, full duplex
3070 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
3071 Filename 'oftrees/mpc8540ads.dtb'.
3072 Load address: 0x300000
3075 Bytes transferred = 4106 (100a hex)
3076 => tftp $loadaddr $bootfile
3077 Speed: 1000, full duplex
3079 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
3081 Load address: 0x200000
3082 Loading:############
3084 Bytes transferred = 1029407 (fb51f hex)
3089 => bootm $loadaddr - $oftaddr
3090 ## Booting image at 00200000 ...
3091 Image Name: Linux-2.6.17-dirty
3092 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3093 Data Size: 1029343 Bytes = 1005.2 kB
3094 Load Address: 00000000
3095 Entry Point: 00000000
3096 Verifying Checksum ... OK
3097 Uncompressing Kernel Image ... OK
3098 Booting using flat device tree at 0x300000
3099 Using MPC85xx ADS machine description
3100 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
3104 More About U-Boot Image Types:
3105 ------------------------------
3107 U-Boot supports the following image types:
3109 "Standalone Programs" are directly runnable in the environment
3110 provided by U-Boot; it is expected that (if they behave
3111 well) you can continue to work in U-Boot after return from
3112 the Standalone Program.
3113 "OS Kernel Images" are usually images of some Embedded OS which
3114 will take over control completely. Usually these programs
3115 will install their own set of exception handlers, device
3116 drivers, set up the MMU, etc. - this means, that you cannot
3117 expect to re-enter U-Boot except by resetting the CPU.
3118 "RAMDisk Images" are more or less just data blocks, and their
3119 parameters (address, size) are passed to an OS kernel that is
3121 "Multi-File Images" contain several images, typically an OS
3122 (Linux) kernel image and one or more data images like
3123 RAMDisks. This construct is useful for instance when you want
3124 to boot over the network using BOOTP etc., where the boot
3125 server provides just a single image file, but you want to get
3126 for instance an OS kernel and a RAMDisk image.
3128 "Multi-File Images" start with a list of image sizes, each
3129 image size (in bytes) specified by an "uint32_t" in network
3130 byte order. This list is terminated by an "(uint32_t)0".
3131 Immediately after the terminating 0 follow the images, one by
3132 one, all aligned on "uint32_t" boundaries (size rounded up to
3133 a multiple of 4 bytes).
3135 "Firmware Images" are binary images containing firmware (like
3136 U-Boot or FPGA images) which usually will be programmed to
3139 "Script files" are command sequences that will be executed by
3140 U-Boot's command interpreter; this feature is especially
3141 useful when you configure U-Boot to use a real shell (hush)
3142 as command interpreter.
3144 Booting the Linux zImage:
3145 -------------------------
3147 On some platforms, it's possible to boot Linux zImage. This is done
3148 using the "bootz" command. The syntax of "bootz" command is the same
3149 as the syntax of "bootm" command.
3151 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
3152 kernel with raw initrd images. The syntax is slightly different, the
3153 address of the initrd must be augmented by it's size, in the following
3154 format: "<initrd addres>:<initrd size>".
3160 One of the features of U-Boot is that you can dynamically load and
3161 run "standalone" applications, which can use some resources of
3162 U-Boot like console I/O functions or interrupt services.
3164 Two simple examples are included with the sources:
3169 'examples/hello_world.c' contains a small "Hello World" Demo
3170 application; it is automatically compiled when you build U-Boot.
3171 It's configured to run at address 0x00040004, so you can play with it
3175 ## Ready for S-Record download ...
3176 ~>examples/hello_world.srec
3177 1 2 3 4 5 6 7 8 9 10 11 ...
3178 [file transfer complete]
3180 ## Start Addr = 0x00040004
3182 => go 40004 Hello World! This is a test.
3183 ## Starting application at 0x00040004 ...
3194 Hit any key to exit ...
3196 ## Application terminated, rc = 0x0
3198 Another example, which demonstrates how to register a CPM interrupt
3199 handler with the U-Boot code, can be found in 'examples/timer.c'.
3200 Here, a CPM timer is set up to generate an interrupt every second.
3201 The interrupt service routine is trivial, just printing a '.'
3202 character, but this is just a demo program. The application can be
3203 controlled by the following keys:
3205 ? - print current values og the CPM Timer registers
3206 b - enable interrupts and start timer
3207 e - stop timer and disable interrupts
3208 q - quit application
3211 ## Ready for S-Record download ...
3212 ~>examples/timer.srec
3213 1 2 3 4 5 6 7 8 9 10 11 ...
3214 [file transfer complete]
3216 ## Start Addr = 0x00040004
3219 ## Starting application at 0x00040004 ...
3222 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
3225 [q, b, e, ?] Set interval 1000000 us
3228 [q, b, e, ?] ........
3229 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
3232 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
3235 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
3238 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
3240 [q, b, e, ?] ...Stopping timer
3242 [q, b, e, ?] ## Application terminated, rc = 0x0
3248 Over time, many people have reported problems when trying to use the
3249 "minicom" terminal emulation program for serial download. I (wd)
3250 consider minicom to be broken, and recommend not to use it. Under
3251 Unix, I recommend to use C-Kermit for general purpose use (and
3252 especially for kermit binary protocol download ("loadb" command), and
3253 use "cu" for S-Record download ("loads" command). See
3254 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
3255 for help with kermit.
3258 Nevertheless, if you absolutely want to use it try adding this
3259 configuration to your "File transfer protocols" section:
3261 Name Program Name U/D FullScr IO-Red. Multi
3262 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
3263 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
3269 Starting at version 0.9.2, U-Boot supports NetBSD both as host
3270 (build U-Boot) and target system (boots NetBSD/mpc8xx).
3272 Building requires a cross environment; it is known to work on
3273 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
3274 need gmake since the Makefiles are not compatible with BSD make).
3275 Note that the cross-powerpc package does not install include files;
3276 attempting to build U-Boot will fail because <machine/ansi.h> is
3277 missing. This file has to be installed and patched manually:
3279 # cd /usr/pkg/cross/powerpc-netbsd/include
3281 # ln -s powerpc machine
3282 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
3283 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
3285 Native builds *don't* work due to incompatibilities between native
3286 and U-Boot include files.
3288 Booting assumes that (the first part of) the image booted is a
3289 stage-2 loader which in turn loads and then invokes the kernel
3290 proper. Loader sources will eventually appear in the NetBSD source
3291 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
3292 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
3295 Implementation Internals:
3296 =========================
3298 The following is not intended to be a complete description of every
3299 implementation detail. However, it should help to understand the
3300 inner workings of U-Boot and make it easier to port it to custom
3304 Initial Stack, Global Data:
3305 ---------------------------
3307 The implementation of U-Boot is complicated by the fact that U-Boot
3308 starts running out of ROM (flash memory), usually without access to
3309 system RAM (because the memory controller is not initialized yet).
3310 This means that we don't have writable Data or BSS segments, and BSS
3311 is not initialized as zero. To be able to get a C environment working
3312 at all, we have to allocate at least a minimal stack. Implementation
3313 options for this are defined and restricted by the CPU used: Some CPU
3314 models provide on-chip memory (like the IMMR area on MPC8xx and
3315 MPC826x processors), on others (parts of) the data cache can be
3316 locked as (mis-) used as memory, etc.
3318 Chris Hallinan posted a good summary of these issues to the
3319 U-Boot mailing list:
3321 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
3322 From: "Chris Hallinan" <clh@net1plus.com>
3323 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
3326 Correct me if I'm wrong, folks, but the way I understand it
3327 is this: Using DCACHE as initial RAM for Stack, etc, does not
3328 require any physical RAM backing up the cache. The cleverness
3329 is that the cache is being used as a temporary supply of
3330 necessary storage before the SDRAM controller is setup. It's
3331 beyond the scope of this list to explain the details, but you
3332 can see how this works by studying the cache architecture and
3333 operation in the architecture and processor-specific manuals.
3335 OCM is On Chip Memory, which I believe the 405GP has 4K. It
3336 is another option for the system designer to use as an
3337 initial stack/RAM area prior to SDRAM being available. Either
3338 option should work for you. Using CS 4 should be fine if your
3339 board designers haven't used it for something that would
3340 cause you grief during the initial boot! It is frequently not
3343 CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
3344 with your processor/board/system design. The default value
3345 you will find in any recent u-boot distribution in
3346 walnut.h should work for you. I'd set it to a value larger
3347 than your SDRAM module. If you have a 64MB SDRAM module, set
3348 it above 400_0000. Just make sure your board has no resources
3349 that are supposed to respond to that address! That code in
3350 start.S has been around a while and should work as is when
3351 you get the config right.
3356 It is essential to remember this, since it has some impact on the C
3357 code for the initialization procedures:
3359 * Initialized global data (data segment) is read-only. Do not attempt
3362 * Do not use any uninitialized global data (or implicitly initialized
3363 as zero data - BSS segment) at all - this is undefined, initiali-
3364 zation is performed later (when relocating to RAM).
3366 * Stack space is very limited. Avoid big data buffers or things like
3369 Having only the stack as writable memory limits means we cannot use
3370 normal global data to share information between the code. But it
3371 turned out that the implementation of U-Boot can be greatly
3372 simplified by making a global data structure (gd_t) available to all
3373 functions. We could pass a pointer to this data as argument to _all_
3374 functions, but this would bloat the code. Instead we use a feature of
3375 the GCC compiler (Global Register Variables) to share the data: we
3376 place a pointer (gd) to the global data into a register which we
3377 reserve for this purpose.
3379 When choosing a register for such a purpose we are restricted by the
3380 relevant (E)ABI specifications for the current architecture, and by
3381 GCC's implementation.
3383 For PowerPC, the following registers have specific use:
3385 R2: reserved for system use
3386 R3-R4: parameter passing and return values
3387 R5-R10: parameter passing
3388 R13: small data area pointer
3392 (U-Boot also uses R12 as internal GOT pointer. r12
3393 is a volatile register so r12 needs to be reset when
3394 going back and forth between asm and C)
3396 ==> U-Boot will use R2 to hold a pointer to the global data
3398 Note: on PPC, we could use a static initializer (since the
3399 address of the global data structure is known at compile time),
3400 but it turned out that reserving a register results in somewhat
3401 smaller code - although the code savings are not that big (on
3402 average for all boards 752 bytes for the whole U-Boot image,
3403 624 text + 127 data).
3405 On ARM, the following registers are used:
3407 R0: function argument word/integer result
3408 R1-R3: function argument word
3409 R9: platform specific
3410 R10: stack limit (used only if stack checking is enabled)
3411 R11: argument (frame) pointer
3412 R12: temporary workspace
3415 R15: program counter
3417 ==> U-Boot will use R9 to hold a pointer to the global data
3419 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
3421 On Nios II, the ABI is documented here:
3422 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
3424 ==> U-Boot will use gp to hold a pointer to the global data
3426 Note: on Nios II, we give "-G0" option to gcc and don't use gp
3427 to access small data sections, so gp is free.
3429 On NDS32, the following registers are used:
3431 R0-R1: argument/return
3433 R15: temporary register for assembler
3434 R16: trampoline register
3435 R28: frame pointer (FP)
3436 R29: global pointer (GP)
3437 R30: link register (LP)
3438 R31: stack pointer (SP)
3439 PC: program counter (PC)
3441 ==> U-Boot will use R10 to hold a pointer to the global data
3443 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
3444 or current versions of GCC may "optimize" the code too much.
3446 On RISC-V, the following registers are used:
3448 x0: hard-wired zero (zero)
3449 x1: return address (ra)
3450 x2: stack pointer (sp)
3451 x3: global pointer (gp)
3452 x4: thread pointer (tp)
3453 x5: link register (t0)
3454 x8: frame pointer (fp)
3455 x10-x11: arguments/return values (a0-1)
3456 x12-x17: arguments (a2-7)
3457 x28-31: temporaries (t3-6)
3458 pc: program counter (pc)
3460 ==> U-Boot will use gp to hold a pointer to the global data
3465 U-Boot runs in system state and uses physical addresses, i.e. the
3466 MMU is not used either for address mapping nor for memory protection.
3468 The available memory is mapped to fixed addresses using the memory
3469 controller. In this process, a contiguous block is formed for each
3470 memory type (Flash, SDRAM, SRAM), even when it consists of several
3471 physical memory banks.
3473 U-Boot is installed in the first 128 kB of the first Flash bank (on
3474 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
3475 booting and sizing and initializing DRAM, the code relocates itself
3476 to the upper end of DRAM. Immediately below the U-Boot code some
3477 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
3478 configuration setting]. Below that, a structure with global Board
3479 Info data is placed, followed by the stack (growing downward).
3481 Additionally, some exception handler code is copied to the low 8 kB
3482 of DRAM (0x00000000 ... 0x00001FFF).
3484 So a typical memory configuration with 16 MB of DRAM could look like
3487 0x0000 0000 Exception Vector code
3490 0x0000 2000 Free for Application Use
3496 0x00FB FF20 Monitor Stack (Growing downward)
3497 0x00FB FFAC Board Info Data and permanent copy of global data
3498 0x00FC 0000 Malloc Arena
3501 0x00FE 0000 RAM Copy of Monitor Code
3502 ... eventually: LCD or video framebuffer
3503 ... eventually: pRAM (Protected RAM - unchanged by reset)
3504 0x00FF FFFF [End of RAM]
3507 System Initialization:
3508 ----------------------
3510 In the reset configuration, U-Boot starts at the reset entry point
3511 (on most PowerPC systems at address 0x00000100). Because of the reset
3512 configuration for CS0# this is a mirror of the on board Flash memory.
3513 To be able to re-map memory U-Boot then jumps to its link address.
3514 To be able to implement the initialization code in C, a (small!)
3515 initial stack is set up in the internal Dual Ported RAM (in case CPUs
3516 which provide such a feature like), or in a locked part of the data
3517 cache. After that, U-Boot initializes the CPU core, the caches and
3520 Next, all (potentially) available memory banks are mapped using a
3521 preliminary mapping. For example, we put them on 512 MB boundaries
3522 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
3523 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
3524 programmed for SDRAM access. Using the temporary configuration, a
3525 simple memory test is run that determines the size of the SDRAM
3528 When there is more than one SDRAM bank, and the banks are of
3529 different size, the largest is mapped first. For equal size, the first
3530 bank (CS2#) is mapped first. The first mapping is always for address
3531 0x00000000, with any additional banks following immediately to create
3532 contiguous memory starting from 0.
3534 Then, the monitor installs itself at the upper end of the SDRAM area
3535 and allocates memory for use by malloc() and for the global Board
3536 Info data; also, the exception vector code is copied to the low RAM
3537 pages, and the final stack is set up.
3539 Only after this relocation will you have a "normal" C environment;
3540 until that you are restricted in several ways, mostly because you are
3541 running from ROM, and because the code will have to be relocated to a
3545 U-Boot Porting Guide:
3546 ----------------------
3548 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
3552 int main(int argc, char *argv[])
3554 sighandler_t no_more_time;
3556 signal(SIGALRM, no_more_time);
3557 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
3559 if (available_money > available_manpower) {
3560 Pay consultant to port U-Boot;
3564 Download latest U-Boot source;
3566 Subscribe to u-boot mailing list;
3569 email("Hi, I am new to U-Boot, how do I get started?");
3572 Read the README file in the top level directory;
3573 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
3574 Read applicable doc/README.*;
3575 Read the source, Luke;
3576 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
3579 if (available_money > toLocalCurrency ($2500))
3582 Add a lot of aggravation and time;
3584 if (a similar board exists) { /* hopefully... */
3585 cp -a board/<similar> board/<myboard>
3586 cp include/configs/<similar>.h include/configs/<myboard>.h
3588 Create your own board support subdirectory;
3589 Create your own board include/configs/<myboard>.h file;
3591 Edit new board/<myboard> files
3592 Edit new include/configs/<myboard>.h
3597 Add / modify source code;
3601 email("Hi, I am having problems...");
3603 Send patch file to the U-Boot email list;
3604 if (reasonable critiques)
3605 Incorporate improvements from email list code review;
3607 Defend code as written;
3613 void no_more_time (int sig)
3622 All contributions to U-Boot should conform to the Linux kernel
3623 coding style; see the kernel coding style guide at
3624 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
3625 script "scripts/Lindent" in your Linux kernel source directory.
3627 Source files originating from a different project (for example the
3628 MTD subsystem) are generally exempt from these guidelines and are not
3629 reformatted to ease subsequent migration to newer versions of those
3632 Please note that U-Boot is implemented in C (and to some small parts in
3633 Assembler); no C++ is used, so please do not use C++ style comments (//)
3636 Please also stick to the following formatting rules:
3637 - remove any trailing white space
3638 - use TAB characters for indentation and vertical alignment, not spaces
3639 - make sure NOT to use DOS '\r\n' line feeds
3640 - do not add more than 2 consecutive empty lines to source files
3641 - do not add trailing empty lines to source files
3643 Submissions which do not conform to the standards may be returned
3644 with a request to reformat the changes.
3650 Since the number of patches for U-Boot is growing, we need to
3651 establish some rules. Submissions which do not conform to these rules
3652 may be rejected, even when they contain important and valuable stuff.
3654 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
3656 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
3657 see https://lists.denx.de/listinfo/u-boot
3659 When you send a patch, please include the following information with
3662 * For bug fixes: a description of the bug and how your patch fixes
3663 this bug. Please try to include a way of demonstrating that the
3664 patch actually fixes something.
3666 * For new features: a description of the feature and your
3669 * For major contributions, add a MAINTAINERS file with your
3670 information and associated file and directory references.
3672 * When you add support for a new board, don't forget to add a
3673 maintainer e-mail address to the boards.cfg file, too.
3675 * If your patch adds new configuration options, don't forget to
3676 document these in the README file.
3678 * The patch itself. If you are using git (which is *strongly*
3679 recommended) you can easily generate the patch using the
3680 "git format-patch". If you then use "git send-email" to send it to
3681 the U-Boot mailing list, you will avoid most of the common problems
3682 with some other mail clients.
3684 If you cannot use git, use "diff -purN OLD NEW". If your version of
3685 diff does not support these options, then get the latest version of
3688 The current directory when running this command shall be the parent
3689 directory of the U-Boot source tree (i. e. please make sure that
3690 your patch includes sufficient directory information for the
3693 We prefer patches as plain text. MIME attachments are discouraged,
3694 and compressed attachments must not be used.
3696 * If one logical set of modifications affects or creates several
3697 files, all these changes shall be submitted in a SINGLE patch file.
3699 * Changesets that contain different, unrelated modifications shall be
3700 submitted as SEPARATE patches, one patch per changeset.
3705 * Before sending the patch, run the buildman script on your patched
3706 source tree and make sure that no errors or warnings are reported
3707 for any of the boards.
3709 * Keep your modifications to the necessary minimum: A patch
3710 containing several unrelated changes or arbitrary reformats will be
3711 returned with a request to re-formatting / split it.
3713 * If you modify existing code, make sure that your new code does not
3714 add to the memory footprint of the code ;-) Small is beautiful!
3715 When adding new features, these should compile conditionally only
3716 (using #ifdef), and the resulting code with the new feature
3717 disabled must not need more memory than the old code without your
3720 * Remember that there is a size limit of 100 kB per message on the
3721 u-boot mailing list. Bigger patches will be moderated. If they are
3722 reasonable and not too big, they will be acknowledged. But patches
3723 bigger than the size limit should be avoided.