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 - Command Line Editing and History:
1536 CONFIG_CMDLINE_PS_SUPPORT
1538 Enable support for changing the command prompt string
1539 at run-time. Only static string is supported so far.
1540 The string is obtained from environment variables PS1
1543 - Default Environment:
1544 CONFIG_EXTRA_ENV_SETTINGS
1546 Define this to contain any number of null terminated
1547 strings (variable = value pairs) that will be part of
1548 the default environment compiled into the boot image.
1550 For example, place something like this in your
1551 board's config file:
1553 #define CONFIG_EXTRA_ENV_SETTINGS \
1557 Warning: This method is based on knowledge about the
1558 internal format how the environment is stored by the
1559 U-Boot code. This is NOT an official, exported
1560 interface! Although it is unlikely that this format
1561 will change soon, there is no guarantee either.
1562 You better know what you are doing here.
1564 Note: overly (ab)use of the default environment is
1565 discouraged. Make sure to check other ways to preset
1566 the environment like the "source" command or the
1569 CONFIG_DELAY_ENVIRONMENT
1571 Normally the environment is loaded when the board is
1572 initialised so that it is available to U-Boot. This inhibits
1573 that so that the environment is not available until
1574 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1575 this is instead controlled by the value of
1576 /config/load-environment.
1578 CONFIG_STANDALONE_LOAD_ADDR
1580 This option defines a board specific value for the
1581 address where standalone program gets loaded, thus
1582 overwriting the architecture dependent default
1585 - Frame Buffer Address:
1588 Define CONFIG_FB_ADDR if you want to use specific
1589 address for frame buffer. This is typically the case
1590 when using a graphics controller has separate video
1591 memory. U-Boot will then place the frame buffer at
1592 the given address instead of dynamically reserving it
1593 in system RAM by calling lcd_setmem(), which grabs
1594 the memory for the frame buffer depending on the
1595 configured panel size.
1597 Please see board_init_f function.
1599 - Automatic software updates via TFTP server
1601 CONFIG_UPDATE_TFTP_CNT_MAX
1602 CONFIG_UPDATE_TFTP_MSEC_MAX
1604 These options enable and control the auto-update feature;
1605 for a more detailed description refer to doc/README.update.
1607 - MTD Support (mtdparts command, UBI support)
1608 CONFIG_MTD_UBI_WL_THRESHOLD
1609 This parameter defines the maximum difference between the highest
1610 erase counter value and the lowest erase counter value of eraseblocks
1611 of UBI devices. When this threshold is exceeded, UBI starts performing
1612 wear leveling by means of moving data from eraseblock with low erase
1613 counter to eraseblocks with high erase counter.
1615 The default value should be OK for SLC NAND flashes, NOR flashes and
1616 other flashes which have eraseblock life-cycle 100000 or more.
1617 However, in case of MLC NAND flashes which typically have eraseblock
1618 life-cycle less than 10000, the threshold should be lessened (e.g.,
1619 to 128 or 256, although it does not have to be power of 2).
1623 CONFIG_MTD_UBI_BEB_LIMIT
1624 This option specifies the maximum bad physical eraseblocks UBI
1625 expects on the MTD device (per 1024 eraseblocks). If the
1626 underlying flash does not admit of bad eraseblocks (e.g. NOR
1627 flash), this value is ignored.
1629 NAND datasheets often specify the minimum and maximum NVM
1630 (Number of Valid Blocks) for the flashes' endurance lifetime.
1631 The maximum expected bad eraseblocks per 1024 eraseblocks
1632 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1633 which gives 20 for most NANDs (MaxNVB is basically the total
1634 count of eraseblocks on the chip).
1636 To put it differently, if this value is 20, UBI will try to
1637 reserve about 1.9% of physical eraseblocks for bad blocks
1638 handling. And that will be 1.9% of eraseblocks on the entire
1639 NAND chip, not just the MTD partition UBI attaches. This means
1640 that if you have, say, a NAND flash chip admits maximum 40 bad
1641 eraseblocks, and it is split on two MTD partitions of the same
1642 size, UBI will reserve 40 eraseblocks when attaching a
1647 CONFIG_MTD_UBI_FASTMAP
1648 Fastmap is a mechanism which allows attaching an UBI device
1649 in nearly constant time. Instead of scanning the whole MTD device it
1650 only has to locate a checkpoint (called fastmap) on the device.
1651 The on-flash fastmap contains all information needed to attach
1652 the device. Using fastmap makes only sense on large devices where
1653 attaching by scanning takes long. UBI will not automatically install
1654 a fastmap on old images, but you can set the UBI parameter
1655 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1656 that fastmap-enabled images are still usable with UBI implementations
1657 without fastmap support. On typical flash devices the whole fastmap
1658 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1660 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1661 Set this parameter to enable fastmap automatically on images
1665 CONFIG_MTD_UBI_FM_DEBUG
1666 Enable UBI fastmap debug
1671 Enable building of SPL globally.
1673 CONFIG_SPL_MAX_FOOTPRINT
1674 Maximum size in memory allocated to the SPL, BSS included.
1675 When defined, the linker checks that the actual memory
1676 used by SPL from _start to __bss_end does not exceed it.
1677 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
1678 must not be both defined at the same time.
1681 Maximum size of the SPL image (text, data, rodata, and
1682 linker lists sections), BSS excluded.
1683 When defined, the linker checks that the actual size does
1686 CONFIG_SPL_RELOC_TEXT_BASE
1687 Address to relocate to. If unspecified, this is equal to
1688 CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
1690 CONFIG_SPL_BSS_START_ADDR
1691 Link address for the BSS within the SPL binary.
1693 CONFIG_SPL_BSS_MAX_SIZE
1694 Maximum size in memory allocated to the SPL BSS.
1695 When defined, the linker checks that the actual memory used
1696 by SPL from __bss_start to __bss_end does not exceed it.
1697 CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
1698 must not be both defined at the same time.
1701 Adress of the start of the stack SPL will use
1703 CONFIG_SPL_PANIC_ON_RAW_IMAGE
1704 When defined, SPL will panic() if the image it has
1705 loaded does not have a signature.
1706 Defining this is useful when code which loads images
1707 in SPL cannot guarantee that absolutely all read errors
1709 An example is the LPC32XX MLC NAND driver, which will
1710 consider that a completely unreadable NAND block is bad,
1711 and thus should be skipped silently.
1713 CONFIG_SPL_RELOC_STACK
1714 Adress of the start of the stack SPL will use after
1715 relocation. If unspecified, this is equal to
1718 CONFIG_SYS_SPL_MALLOC_START
1719 Starting address of the malloc pool used in SPL.
1720 When this option is set the full malloc is used in SPL and
1721 it is set up by spl_init() and before that, the simple malloc()
1722 can be used if CONFIG_SYS_MALLOC_F is defined.
1724 CONFIG_SYS_SPL_MALLOC_SIZE
1725 The size of the malloc pool used in SPL.
1727 CONFIG_SPL_DISPLAY_PRINT
1728 For ARM, enable an optional function to print more information
1729 about the running system.
1731 CONFIG_SPL_INIT_MINIMAL
1732 Arch init code should be built for a very small image
1734 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
1735 CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
1736 Sector and number of sectors to load kernel argument
1737 parameters from when MMC is being used in raw mode
1740 CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
1741 Filename to read to load U-Boot when reading from filesystem
1743 CONFIG_SPL_FS_LOAD_KERNEL_NAME
1744 Filename to read to load kernel uImage when reading
1745 from filesystem (for Falcon mode)
1747 CONFIG_SPL_FS_LOAD_ARGS_NAME
1748 Filename to read to load kernel argument parameters
1749 when reading from filesystem (for Falcon mode)
1751 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
1752 Set this for NAND SPL on PPC mpc83xx targets, so that
1753 start.S waits for the rest of the SPL to load before
1754 continuing (the hardware starts execution after just
1755 loading the first page rather than the full 4K).
1757 CONFIG_SPL_SKIP_RELOCATE
1758 Avoid SPL relocation
1761 Support for a lightweight UBI (fastmap) scanner and
1764 CONFIG_SPL_NAND_RAW_ONLY
1765 Support to boot only raw u-boot.bin images. Use this only
1766 if you need to save space.
1768 CONFIG_SPL_COMMON_INIT_DDR
1769 Set for common ddr init with serial presence detect in
1772 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
1773 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
1774 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
1775 CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
1776 CONFIG_SYS_NAND_ECCBYTES
1777 Defines the size and behavior of the NAND that SPL uses
1780 CONFIG_SYS_NAND_U_BOOT_DST
1781 Location in memory to load U-Boot to
1783 CONFIG_SYS_NAND_U_BOOT_SIZE
1784 Size of image to load
1786 CONFIG_SYS_NAND_U_BOOT_START
1787 Entry point in loaded image to jump to
1789 CONFIG_SYS_NAND_HW_ECC_OOBFIRST
1790 Define this if you need to first read the OOB and then the
1791 data. This is used, for example, on davinci platforms.
1793 CONFIG_SPL_RAM_DEVICE
1794 Support for running image already present in ram, in SPL binary
1797 Image offset to which the SPL should be padded before appending
1798 the SPL payload. By default, this is defined as
1799 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
1800 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
1801 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
1804 Final target image containing SPL and payload. Some SPLs
1805 use an arch-specific makefile fragment instead, for
1806 example if more than one image needs to be produced.
1808 CONFIG_SPL_FIT_PRINT
1809 Printing information about a FIT image adds quite a bit of
1810 code to SPL. So this is normally disabled in SPL. Use this
1811 option to re-enable it. This will affect the output of the
1812 bootm command when booting a FIT image.
1816 Enable building of TPL globally.
1819 Image offset to which the TPL should be padded before appending
1820 the TPL payload. By default, this is defined as
1821 CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
1822 CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
1823 payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
1825 - Interrupt support (PPC):
1827 There are common interrupt_init() and timer_interrupt()
1828 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
1829 for CPU specific initialization. interrupt_init_cpu()
1830 should set decrementer_count to appropriate value. If
1831 CPU resets decrementer automatically after interrupt
1832 (ppc4xx) it should set decrementer_count to zero.
1833 timer_interrupt() calls timer_interrupt_cpu() for CPU
1834 specific handling. If board has watchdog / status_led
1835 / other_activity_monitor it works automatically from
1836 general timer_interrupt().
1839 Board initialization settings:
1840 ------------------------------
1842 During Initialization u-boot calls a number of board specific functions
1843 to allow the preparation of board specific prerequisites, e.g. pin setup
1844 before drivers are initialized. To enable these callbacks the
1845 following configuration macros have to be defined. Currently this is
1846 architecture specific, so please check arch/your_architecture/lib/board.c
1847 typically in board_init_f() and board_init_r().
1849 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
1850 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
1851 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
1853 Configuration Settings:
1854 -----------------------
1856 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
1857 Optionally it can be defined to support 64-bit memory commands.
1859 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
1860 undefine this when you're short of memory.
1862 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
1863 width of the commands listed in the 'help' command output.
1865 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
1866 prompt for user input.
1868 - CONFIG_SYS_CBSIZE: Buffer size for input from the Console
1870 - CONFIG_SYS_PBSIZE: Buffer size for Console output
1872 - CONFIG_SYS_MAXARGS: max. Number of arguments accepted for monitor commands
1874 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
1875 the application (usually a Linux kernel) when it is
1878 - CONFIG_SYS_BAUDRATE_TABLE:
1879 List of legal baudrate settings for this board.
1881 - CONFIG_SYS_MEM_RESERVE_SECURE
1882 Only implemented for ARMv8 for now.
1883 If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
1884 is substracted from total RAM and won't be reported to OS.
1885 This memory can be used as secure memory. A variable
1886 gd->arch.secure_ram is used to track the location. In systems
1887 the RAM base is not zero, or RAM is divided into banks,
1888 this variable needs to be recalcuated to get the address.
1890 - CONFIG_SYS_MEM_TOP_HIDE:
1891 If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
1892 this specified memory area will get subtracted from the top
1893 (end) of RAM and won't get "touched" at all by U-Boot. By
1894 fixing up gd->ram_size the Linux kernel should gets passed
1895 the now "corrected" memory size and won't touch it either.
1896 This should work for arch/ppc and arch/powerpc. Only Linux
1897 board ports in arch/powerpc with bootwrapper support that
1898 recalculate the memory size from the SDRAM controller setup
1899 will have to get fixed in Linux additionally.
1901 This option can be used as a workaround for the 440EPx/GRx
1902 CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
1905 WARNING: Please make sure that this value is a multiple of
1906 the Linux page size (normally 4k). If this is not the case,
1907 then the end address of the Linux memory will be located at a
1908 non page size aligned address and this could cause major
1911 - CONFIG_SYS_LOADS_BAUD_CHANGE:
1912 Enable temporary baudrate change while serial download
1914 - CONFIG_SYS_SDRAM_BASE:
1915 Physical start address of SDRAM. _Must_ be 0 here.
1917 - CONFIG_SYS_FLASH_BASE:
1918 Physical start address of Flash memory.
1920 - CONFIG_SYS_MONITOR_BASE:
1921 Physical start address of boot monitor code (set by
1922 make config files to be same as the text base address
1923 (CONFIG_SYS_TEXT_BASE) used when linking) - same as
1924 CONFIG_SYS_FLASH_BASE when booting from flash.
1926 - CONFIG_SYS_MONITOR_LEN:
1927 Size of memory reserved for monitor code, used to
1928 determine _at_compile_time_ (!) if the environment is
1929 embedded within the U-Boot image, or in a separate
1932 - CONFIG_SYS_MALLOC_LEN:
1933 Size of DRAM reserved for malloc() use.
1935 - CONFIG_SYS_MALLOC_F_LEN
1936 Size of the malloc() pool for use before relocation. If
1937 this is defined, then a very simple malloc() implementation
1938 will become available before relocation. The address is just
1939 below the global data, and the stack is moved down to make
1942 This feature allocates regions with increasing addresses
1943 within the region. calloc() is supported, but realloc()
1944 is not available. free() is supported but does nothing.
1945 The memory will be freed (or in fact just forgotten) when
1946 U-Boot relocates itself.
1948 - CONFIG_SYS_MALLOC_SIMPLE
1949 Provides a simple and small malloc() and calloc() for those
1950 boards which do not use the full malloc in SPL (which is
1951 enabled with CONFIG_SYS_SPL_MALLOC_START).
1953 - CONFIG_SYS_NONCACHED_MEMORY:
1954 Size of non-cached memory area. This area of memory will be
1955 typically located right below the malloc() area and mapped
1956 uncached in the MMU. This is useful for drivers that would
1957 otherwise require a lot of explicit cache maintenance. For
1958 some drivers it's also impossible to properly maintain the
1959 cache. For example if the regions that need to be flushed
1960 are not a multiple of the cache-line size, *and* padding
1961 cannot be allocated between the regions to align them (i.e.
1962 if the HW requires a contiguous array of regions, and the
1963 size of each region is not cache-aligned), then a flush of
1964 one region may result in overwriting data that hardware has
1965 written to another region in the same cache-line. This can
1966 happen for example in network drivers where descriptors for
1967 buffers are typically smaller than the CPU cache-line (e.g.
1968 16 bytes vs. 32 or 64 bytes).
1970 Non-cached memory is only supported on 32-bit ARM at present.
1972 - CONFIG_SYS_BOOTM_LEN:
1973 Normally compressed uImages are limited to an
1974 uncompressed size of 8 MBytes. If this is not enough,
1975 you can define CONFIG_SYS_BOOTM_LEN in your board config file
1976 to adjust this setting to your needs.
1978 - CONFIG_SYS_BOOTMAPSZ:
1979 Maximum size of memory mapped by the startup code of
1980 the Linux kernel; all data that must be processed by
1981 the Linux kernel (bd_info, boot arguments, FDT blob if
1982 used) must be put below this limit, unless "bootm_low"
1983 environment variable is defined and non-zero. In such case
1984 all data for the Linux kernel must be between "bootm_low"
1985 and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
1986 variable "bootm_mapsize" will override the value of
1987 CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
1988 then the value in "bootm_size" will be used instead.
1990 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
1991 Enable initrd_high functionality. If defined then the
1992 initrd_high feature is enabled and the bootm ramdisk subcommand
1995 - CONFIG_SYS_BOOT_GET_CMDLINE:
1996 Enables allocating and saving kernel cmdline in space between
1997 "bootm_low" and "bootm_low" + BOOTMAPSZ.
1999 - CONFIG_SYS_BOOT_GET_KBD:
2000 Enables allocating and saving a kernel copy of the bd_info in
2001 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2003 - CONFIG_SYS_MAX_FLASH_SECT:
2004 Max number of sectors on a Flash chip
2006 - CONFIG_SYS_FLASH_ERASE_TOUT:
2007 Timeout for Flash erase operations (in ms)
2009 - CONFIG_SYS_FLASH_WRITE_TOUT:
2010 Timeout for Flash write operations (in ms)
2012 - CONFIG_SYS_FLASH_LOCK_TOUT
2013 Timeout for Flash set sector lock bit operation (in ms)
2015 - CONFIG_SYS_FLASH_UNLOCK_TOUT
2016 Timeout for Flash clear lock bits operation (in ms)
2018 - CONFIG_SYS_FLASH_PROTECTION
2019 If defined, hardware flash sectors protection is used
2020 instead of U-Boot software protection.
2022 - CONFIG_SYS_DIRECT_FLASH_TFTP:
2024 Enable TFTP transfers directly to flash memory;
2025 without this option such a download has to be
2026 performed in two steps: (1) download to RAM, and (2)
2027 copy from RAM to flash.
2029 The two-step approach is usually more reliable, since
2030 you can check if the download worked before you erase
2031 the flash, but in some situations (when system RAM is
2032 too limited to allow for a temporary copy of the
2033 downloaded image) this option may be very useful.
2035 - CONFIG_SYS_FLASH_CFI:
2036 Define if the flash driver uses extra elements in the
2037 common flash structure for storing flash geometry.
2039 - CONFIG_FLASH_CFI_DRIVER
2040 This option also enables the building of the cfi_flash driver
2041 in the drivers directory
2043 - CONFIG_FLASH_CFI_MTD
2044 This option enables the building of the cfi_mtd driver
2045 in the drivers directory. The driver exports CFI flash
2048 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2049 Use buffered writes to flash.
2051 - CONFIG_FLASH_SPANSION_S29WS_N
2052 s29ws-n MirrorBit flash has non-standard addresses for buffered
2055 - CONFIG_SYS_FLASH_QUIET_TEST
2056 If this option is defined, the common CFI flash doesn't
2057 print it's warning upon not recognized FLASH banks. This
2058 is useful, if some of the configured banks are only
2059 optionally available.
2061 - CONFIG_FLASH_SHOW_PROGRESS
2062 If defined (must be an integer), print out countdown
2063 digits and dots. Recommended value: 45 (9..1) for 80
2064 column displays, 15 (3..1) for 40 column displays.
2066 - CONFIG_FLASH_VERIFY
2067 If defined, the content of the flash (destination) is compared
2068 against the source after the write operation. An error message
2069 will be printed when the contents are not identical.
2070 Please note that this option is useless in nearly all cases,
2071 since such flash programming errors usually are detected earlier
2072 while unprotecting/erasing/programming. Please only enable
2073 this option if you really know what you are doing.
2075 - CONFIG_ENV_MAX_ENTRIES
2077 Maximum number of entries in the hash table that is used
2078 internally to store the environment settings. The default
2079 setting is supposed to be generous and should work in most
2080 cases. This setting can be used to tune behaviour; see
2081 lib/hashtable.c for details.
2083 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2084 - CONFIG_ENV_FLAGS_LIST_STATIC
2085 Enable validation of the values given to environment variables when
2086 calling env set. Variables can be restricted to only decimal,
2087 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
2088 the variables can also be restricted to IP address or MAC address.
2090 The format of the list is:
2091 type_attribute = [s|d|x|b|i|m]
2092 access_attribute = [a|r|o|c]
2093 attributes = type_attribute[access_attribute]
2094 entry = variable_name[:attributes]
2097 The type attributes are:
2098 s - String (default)
2101 b - Boolean ([1yYtT|0nNfF])
2105 The access attributes are:
2111 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2112 Define this to a list (string) to define the ".flags"
2113 environment variable in the default or embedded environment.
2115 - CONFIG_ENV_FLAGS_LIST_STATIC
2116 Define this to a list (string) to define validation that
2117 should be done if an entry is not found in the ".flags"
2118 environment variable. To override a setting in the static
2119 list, simply add an entry for the same variable name to the
2122 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2123 regular expression. This allows multiple variables to define the same
2124 flags without explicitly listing them for each variable.
2126 The following definitions that deal with the placement and management
2127 of environment data (variable area); in general, we support the
2128 following configurations:
2130 - CONFIG_BUILD_ENVCRC:
2132 Builds up envcrc with the target environment so that external utils
2133 may easily extract it and embed it in final U-Boot images.
2135 BE CAREFUL! The first access to the environment happens quite early
2136 in U-Boot initialization (when we try to get the setting of for the
2137 console baudrate). You *MUST* have mapped your NVRAM area then, or
2140 Please note that even with NVRAM we still use a copy of the
2141 environment in RAM: we could work on NVRAM directly, but we want to
2142 keep settings there always unmodified except somebody uses "saveenv"
2143 to save the current settings.
2145 BE CAREFUL! For some special cases, the local device can not use
2146 "saveenv" command. For example, the local device will get the
2147 environment stored in a remote NOR flash by SRIO or PCIE link,
2148 but it can not erase, write this NOR flash by SRIO or PCIE interface.
2150 - CONFIG_NAND_ENV_DST
2152 Defines address in RAM to which the nand_spl code should copy the
2153 environment. If redundant environment is used, it will be copied to
2154 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2156 Please note that the environment is read-only until the monitor
2157 has been relocated to RAM and a RAM copy of the environment has been
2158 created; also, when using EEPROM you will have to use env_get_f()
2159 until then to read environment variables.
2161 The environment is protected by a CRC32 checksum. Before the monitor
2162 is relocated into RAM, as a result of a bad CRC you will be working
2163 with the compiled-in default environment - *silently*!!! [This is
2164 necessary, because the first environment variable we need is the
2165 "baudrate" setting for the console - if we have a bad CRC, we don't
2166 have any device yet where we could complain.]
2168 Note: once the monitor has been relocated, then it will complain if
2169 the default environment is used; a new CRC is computed as soon as you
2170 use the "saveenv" command to store a valid environment.
2172 - CONFIG_SYS_FAULT_MII_ADDR:
2173 MII address of the PHY to check for the Ethernet link state.
2175 - CONFIG_NS16550_MIN_FUNCTIONS:
2176 Define this if you desire to only have use of the NS16550_init
2177 and NS16550_putc functions for the serial driver located at
2178 drivers/serial/ns16550.c. This option is useful for saving
2179 space for already greatly restricted images, including but not
2180 limited to NAND_SPL configurations.
2182 - CONFIG_DISPLAY_BOARDINFO
2183 Display information about the board that U-Boot is running on
2184 when U-Boot starts up. The board function checkboard() is called
2187 - CONFIG_DISPLAY_BOARDINFO_LATE
2188 Similar to the previous option, but display this information
2189 later, once stdio is running and output goes to the LCD, if
2192 - CONFIG_BOARD_SIZE_LIMIT:
2193 Maximum size of the U-Boot image. When defined, the
2194 build system checks that the actual size does not
2197 Low Level (hardware related) configuration options:
2198 ---------------------------------------------------
2200 - CONFIG_SYS_CACHELINE_SIZE:
2201 Cache Line Size of the CPU.
2203 - CONFIG_SYS_CCSRBAR_DEFAULT:
2204 Default (power-on reset) physical address of CCSR on Freescale
2207 - CONFIG_SYS_CCSRBAR:
2208 Virtual address of CCSR. On a 32-bit build, this is typically
2209 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2211 - CONFIG_SYS_CCSRBAR_PHYS:
2212 Physical address of CCSR. CCSR can be relocated to a new
2213 physical address, if desired. In this case, this macro should
2214 be set to that address. Otherwise, it should be set to the
2215 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
2216 is typically relocated on 36-bit builds. It is recommended
2217 that this macro be defined via the _HIGH and _LOW macros:
2219 #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2220 * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2222 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2223 Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
2224 either 0 (32-bit build) or 0xF (36-bit build). This macro is
2225 used in assembly code, so it must not contain typecasts or
2226 integer size suffixes (e.g. "ULL").
2228 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
2229 Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
2230 used in assembly code, so it must not contain typecasts or
2231 integer size suffixes (e.g. "ULL").
2233 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2234 If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2235 forced to a value that ensures that CCSR is not relocated.
2237 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
2238 DO NOT CHANGE unless you know exactly what you're
2239 doing! (11-4) [MPC8xx systems only]
2241 - CONFIG_SYS_INIT_RAM_ADDR:
2243 Start address of memory area that can be used for
2244 initial data and stack; please note that this must be
2245 writable memory that is working WITHOUT special
2246 initialization, i. e. you CANNOT use normal RAM which
2247 will become available only after programming the
2248 memory controller and running certain initialization
2251 U-Boot uses the following memory types:
2252 - MPC8xx: IMMR (internal memory of the CPU)
2254 - CONFIG_SYS_GBL_DATA_OFFSET:
2256 Offset of the initial data structure in the memory
2257 area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2258 CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2259 data is located at the end of the available space
2260 (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2261 GENERATED_GBL_DATA_SIZE), and the initial stack is just
2262 below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2263 CONFIG_SYS_GBL_DATA_OFFSET) downward.
2266 On the MPC824X (or other systems that use the data
2267 cache for initial memory) the address chosen for
2268 CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2269 point to an otherwise UNUSED address space between
2270 the top of RAM and the start of the PCI space.
2272 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
2274 - CONFIG_SYS_OR_TIMING_SDRAM:
2277 - CONFIG_SYS_MAMR_PTA:
2278 periodic timer for refresh
2281 Chip has SRIO or not
2284 Board has SRIO 1 port available
2287 Board has SRIO 2 port available
2289 - CONFIG_SRIO_PCIE_BOOT_MASTER
2290 Board can support master function for Boot from SRIO and PCIE
2292 - CONFIG_SYS_SRIOn_MEM_VIRT:
2293 Virtual Address of SRIO port 'n' memory region
2295 - CONFIG_SYS_SRIOn_MEM_PHYxS:
2296 Physical Address of SRIO port 'n' memory region
2298 - CONFIG_SYS_SRIOn_MEM_SIZE:
2299 Size of SRIO port 'n' memory region
2301 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
2302 Defined to tell the NAND controller that the NAND chip is using
2304 Not all NAND drivers use this symbol.
2305 Example of drivers that use it:
2306 - drivers/mtd/nand/raw/ndfc.c
2307 - drivers/mtd/nand/raw/mxc_nand.c
2309 - CONFIG_SYS_NDFC_EBC0_CFG
2310 Sets the EBC0_CFG register for the NDFC. If not defined
2311 a default value will be used.
2314 Get DDR timing information from an I2C EEPROM. Common
2315 with pluggable memory modules such as SODIMMs
2318 I2C address of the SPD EEPROM
2320 - CONFIG_SYS_SPD_BUS_NUM
2321 If SPD EEPROM is on an I2C bus other than the first
2322 one, specify here. Note that the value must resolve
2323 to something your driver can deal with.
2325 - CONFIG_SYS_DDR_RAW_TIMING
2326 Get DDR timing information from other than SPD. Common with
2327 soldered DDR chips onboard without SPD. DDR raw timing
2328 parameters are extracted from datasheet and hard-coded into
2329 header files or board specific files.
2331 - CONFIG_FSL_DDR_INTERACTIVE
2332 Enable interactive DDR debugging. See doc/README.fsl-ddr.
2334 - CONFIG_FSL_DDR_SYNC_REFRESH
2335 Enable sync of refresh for multiple controllers.
2337 - CONFIG_FSL_DDR_BIST
2338 Enable built-in memory test for Freescale DDR controllers.
2340 - CONFIG_SYS_83XX_DDR_USES_CS0
2341 Only for 83xx systems. If specified, then DDR should
2342 be configured using CS0 and CS1 instead of CS2 and CS3.
2345 Enable RMII mode for all FECs.
2346 Note that this is a global option, we can't
2347 have one FEC in standard MII mode and another in RMII mode.
2349 - CONFIG_CRC32_VERIFY
2350 Add a verify option to the crc32 command.
2353 => crc32 -v <address> <count> <crc32>
2355 Where address/count indicate a memory area
2356 and crc32 is the correct crc32 which the
2360 Add the "loopw" memory command. This only takes effect if
2361 the memory commands are activated globally (CONFIG_CMD_MEMORY).
2363 - CONFIG_CMD_MX_CYCLIC
2364 Add the "mdc" and "mwc" memory commands. These are cyclic
2369 This command will print 4 bytes (10,11,12,13) each 500 ms.
2371 => mwc.l 100 12345678 10
2372 This command will write 12345678 to address 100 all 10 ms.
2374 This only takes effect if the memory commands are activated
2375 globally (CONFIG_CMD_MEMORY).
2378 Set when the currently-running compilation is for an artifact
2379 that will end up in the SPL (as opposed to the TPL or U-Boot
2380 proper). Code that needs stage-specific behavior should check
2384 Set when the currently-running compilation is for an artifact
2385 that will end up in the TPL (as opposed to the SPL or U-Boot
2386 proper). Code that needs stage-specific behavior should check
2389 - CONFIG_SYS_MPC85XX_NO_RESETVEC
2390 Only for 85xx systems. If this variable is specified, the section
2391 .resetvec is not kept and the section .bootpg is placed in the
2392 previous 4k of the .text section.
2394 - CONFIG_ARCH_MAP_SYSMEM
2395 Generally U-Boot (and in particular the md command) uses
2396 effective address. It is therefore not necessary to regard
2397 U-Boot address as virtual addresses that need to be translated
2398 to physical addresses. However, sandbox requires this, since
2399 it maintains its own little RAM buffer which contains all
2400 addressable memory. This option causes some memory accesses
2401 to be mapped through map_sysmem() / unmap_sysmem().
2403 - CONFIG_X86_RESET_VECTOR
2404 If defined, the x86 reset vector code is included. This is not
2405 needed when U-Boot is running from Coreboot.
2407 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
2408 Option to disable subpage write in NAND driver
2409 driver that uses this:
2410 drivers/mtd/nand/raw/davinci_nand.c
2412 Freescale QE/FMAN Firmware Support:
2413 -----------------------------------
2415 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
2416 loading of "firmware", which is encoded in the QE firmware binary format.
2417 This firmware often needs to be loaded during U-Boot booting, so macros
2418 are used to identify the storage device (NOR flash, SPI, etc) and the address
2421 - CONFIG_SYS_FMAN_FW_ADDR
2422 The address in the storage device where the FMAN microcode is located. The
2423 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2426 - CONFIG_SYS_QE_FW_ADDR
2427 The address in the storage device where the QE microcode is located. The
2428 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2431 - CONFIG_SYS_QE_FMAN_FW_LENGTH
2432 The maximum possible size of the firmware. The firmware binary format
2433 has a field that specifies the actual size of the firmware, but it
2434 might not be possible to read any part of the firmware unless some
2435 local storage is allocated to hold the entire firmware first.
2437 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
2438 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
2439 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
2440 virtual address in NOR flash.
2442 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
2443 Specifies that QE/FMAN firmware is located in NAND flash.
2444 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
2446 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
2447 Specifies that QE/FMAN firmware is located on the primary SD/MMC
2448 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
2450 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
2451 Specifies that QE/FMAN firmware is located in the remote (master)
2452 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
2453 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
2454 window->master inbound window->master LAW->the ucode address in
2455 master's memory space.
2457 Freescale Layerscape Management Complex Firmware Support:
2458 ---------------------------------------------------------
2459 The Freescale Layerscape Management Complex (MC) supports the loading of
2461 This firmware often needs to be loaded during U-Boot booting, so macros
2462 are used to identify the storage device (NOR flash, SPI, etc) and the address
2465 - CONFIG_FSL_MC_ENET
2466 Enable the MC driver for Layerscape SoCs.
2468 Freescale Layerscape Debug Server Support:
2469 -------------------------------------------
2470 The Freescale Layerscape Debug Server Support supports the loading of
2471 "Debug Server firmware" and triggering SP boot-rom.
2472 This firmware often needs to be loaded during U-Boot booting.
2474 - CONFIG_SYS_MC_RSV_MEM_ALIGN
2475 Define alignment of reserved memory MC requires
2480 In order to achieve reproducible builds, timestamps used in the U-Boot build
2481 process have to be set to a fixed value.
2483 This is done using the SOURCE_DATE_EPOCH environment variable.
2484 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
2485 option for U-Boot or an environment variable in U-Boot.
2487 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
2489 Building the Software:
2490 ======================
2492 Building U-Boot has been tested in several native build environments
2493 and in many different cross environments. Of course we cannot support
2494 all possibly existing versions of cross development tools in all
2495 (potentially obsolete) versions. In case of tool chain problems we
2496 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
2497 which is extensively used to build and test U-Boot.
2499 If you are not using a native environment, it is assumed that you
2500 have GNU cross compiling tools available in your path. In this case,
2501 you must set the environment variable CROSS_COMPILE in your shell.
2502 Note that no changes to the Makefile or any other source files are
2503 necessary. For example using the ELDK on a 4xx CPU, please enter:
2505 $ CROSS_COMPILE=ppc_4xx-
2506 $ export CROSS_COMPILE
2508 U-Boot is intended to be simple to build. After installing the
2509 sources you must configure U-Boot for one specific board type. This
2514 where "NAME_defconfig" is the name of one of the existing configu-
2515 rations; see configs/*_defconfig for supported names.
2517 Note: for some boards special configuration names may exist; check if
2518 additional information is available from the board vendor; for
2519 instance, the TQM823L systems are available without (standard)
2520 or with LCD support. You can select such additional "features"
2521 when choosing the configuration, i. e.
2523 make TQM823L_defconfig
2524 - will configure for a plain TQM823L, i. e. no LCD support
2526 make TQM823L_LCD_defconfig
2527 - will configure for a TQM823L with U-Boot console on LCD
2532 Finally, type "make all", and you should get some working U-Boot
2533 images ready for download to / installation on your system:
2535 - "u-boot.bin" is a raw binary image
2536 - "u-boot" is an image in ELF binary format
2537 - "u-boot.srec" is in Motorola S-Record format
2539 By default the build is performed locally and the objects are saved
2540 in the source directory. One of the two methods can be used to change
2541 this behavior and build U-Boot to some external directory:
2543 1. Add O= to the make command line invocations:
2545 make O=/tmp/build distclean
2546 make O=/tmp/build NAME_defconfig
2547 make O=/tmp/build all
2549 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
2551 export KBUILD_OUTPUT=/tmp/build
2556 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
2559 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
2560 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
2561 For example to treat all compiler warnings as errors:
2563 make KCFLAGS=-Werror
2565 Please be aware that the Makefiles assume you are using GNU make, so
2566 for instance on NetBSD you might need to use "gmake" instead of
2570 If the system board that you have is not listed, then you will need
2571 to port U-Boot to your hardware platform. To do this, follow these
2574 1. Create a new directory to hold your board specific code. Add any
2575 files you need. In your board directory, you will need at least
2576 the "Makefile" and a "<board>.c".
2577 2. Create a new configuration file "include/configs/<board>.h" for
2579 3. If you're porting U-Boot to a new CPU, then also create a new
2580 directory to hold your CPU specific code. Add any files you need.
2581 4. Run "make <board>_defconfig" with your new name.
2582 5. Type "make", and you should get a working "u-boot.srec" file
2583 to be installed on your target system.
2584 6. Debug and solve any problems that might arise.
2585 [Of course, this last step is much harder than it sounds.]
2588 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
2589 ==============================================================
2591 If you have modified U-Boot sources (for instance added a new board
2592 or support for new devices, a new CPU, etc.) you are expected to
2593 provide feedback to the other developers. The feedback normally takes
2594 the form of a "patch", i.e. a context diff against a certain (latest
2595 official or latest in the git repository) version of U-Boot sources.
2597 But before you submit such a patch, please verify that your modifi-
2598 cation did not break existing code. At least make sure that *ALL* of
2599 the supported boards compile WITHOUT ANY compiler warnings. To do so,
2600 just run the buildman script (tools/buildman/buildman), which will
2601 configure and build U-Boot for ALL supported system. Be warned, this
2602 will take a while. Please see the buildman README, or run 'buildman -H'
2606 See also "U-Boot Porting Guide" below.
2609 Monitor Commands - Overview:
2610 ============================
2612 go - start application at address 'addr'
2613 run - run commands in an environment variable
2614 bootm - boot application image from memory
2615 bootp - boot image via network using BootP/TFTP protocol
2616 bootz - boot zImage from memory
2617 tftpboot- boot image via network using TFTP protocol
2618 and env variables "ipaddr" and "serverip"
2619 (and eventually "gatewayip")
2620 tftpput - upload a file via network using TFTP protocol
2621 rarpboot- boot image via network using RARP/TFTP protocol
2622 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
2623 loads - load S-Record file over serial line
2624 loadb - load binary file over serial line (kermit mode)
2626 mm - memory modify (auto-incrementing)
2627 nm - memory modify (constant address)
2628 mw - memory write (fill)
2631 cmp - memory compare
2632 crc32 - checksum calculation
2633 i2c - I2C sub-system
2634 sspi - SPI utility commands
2635 base - print or set address offset
2636 printenv- print environment variables
2637 pwm - control pwm channels
2638 setenv - set environment variables
2639 saveenv - save environment variables to persistent storage
2640 protect - enable or disable FLASH write protection
2641 erase - erase FLASH memory
2642 flinfo - print FLASH memory information
2643 nand - NAND memory operations (see doc/README.nand)
2644 bdinfo - print Board Info structure
2645 iminfo - print header information for application image
2646 coninfo - print console devices and informations
2647 ide - IDE sub-system
2648 loop - infinite loop on address range
2649 loopw - infinite write loop on address range
2650 mtest - simple RAM test
2651 icache - enable or disable instruction cache
2652 dcache - enable or disable data cache
2653 reset - Perform RESET of the CPU
2654 echo - echo args to console
2655 version - print monitor version
2656 help - print online help
2657 ? - alias for 'help'
2660 Monitor Commands - Detailed Description:
2661 ========================================
2665 For now: just type "help <command>".
2668 Note for Redundant Ethernet Interfaces:
2669 =======================================
2671 Some boards come with redundant Ethernet interfaces; U-Boot supports
2672 such configurations and is capable of automatic selection of a
2673 "working" interface when needed. MAC assignment works as follows:
2675 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
2676 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
2677 "eth1addr" (=>eth1), "eth2addr", ...
2679 If the network interface stores some valid MAC address (for instance
2680 in SROM), this is used as default address if there is NO correspon-
2681 ding setting in the environment; if the corresponding environment
2682 variable is set, this overrides the settings in the card; that means:
2684 o If the SROM has a valid MAC address, and there is no address in the
2685 environment, the SROM's address is used.
2687 o If there is no valid address in the SROM, and a definition in the
2688 environment exists, then the value from the environment variable is
2691 o If both the SROM and the environment contain a MAC address, and
2692 both addresses are the same, this MAC address is used.
2694 o If both the SROM and the environment contain a MAC address, and the
2695 addresses differ, the value from the environment is used and a
2698 o If neither SROM nor the environment contain a MAC address, an error
2699 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
2700 a random, locally-assigned MAC is used.
2702 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
2703 will be programmed into hardware as part of the initialization process. This
2704 may be skipped by setting the appropriate 'ethmacskip' environment variable.
2705 The naming convention is as follows:
2706 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
2711 U-Boot is capable of booting (and performing other auxiliary operations on)
2712 images in two formats:
2714 New uImage format (FIT)
2715 -----------------------
2717 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
2718 to Flattened Device Tree). It allows the use of images with multiple
2719 components (several kernels, ramdisks, etc.), with contents protected by
2720 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
2726 Old image format is based on binary files which can be basically anything,
2727 preceded by a special header; see the definitions in include/image.h for
2728 details; basically, the header defines the following image properties:
2730 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
2731 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
2732 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
2733 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
2734 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
2735 IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
2736 Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
2737 * Compression Type (uncompressed, gzip, bzip2)
2743 The header is marked by a special Magic Number, and both the header
2744 and the data portions of the image are secured against corruption by
2751 Although U-Boot should support any OS or standalone application
2752 easily, the main focus has always been on Linux during the design of
2755 U-Boot includes many features that so far have been part of some
2756 special "boot loader" code within the Linux kernel. Also, any
2757 "initrd" images to be used are no longer part of one big Linux image;
2758 instead, kernel and "initrd" are separate images. This implementation
2759 serves several purposes:
2761 - the same features can be used for other OS or standalone
2762 applications (for instance: using compressed images to reduce the
2763 Flash memory footprint)
2765 - it becomes much easier to port new Linux kernel versions because
2766 lots of low-level, hardware dependent stuff are done by U-Boot
2768 - the same Linux kernel image can now be used with different "initrd"
2769 images; of course this also means that different kernel images can
2770 be run with the same "initrd". This makes testing easier (you don't
2771 have to build a new "zImage.initrd" Linux image when you just
2772 change a file in your "initrd"). Also, a field-upgrade of the
2773 software is easier now.
2779 Porting Linux to U-Boot based systems:
2780 ---------------------------------------
2782 U-Boot cannot save you from doing all the necessary modifications to
2783 configure the Linux device drivers for use with your target hardware
2784 (no, we don't intend to provide a full virtual machine interface to
2787 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
2789 Just make sure your machine specific header file (for instance
2790 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2791 Information structure as we define in include/asm-<arch>/u-boot.h,
2792 and make sure that your definition of IMAP_ADDR uses the same value
2793 as your U-Boot configuration in CONFIG_SYS_IMMR.
2795 Note that U-Boot now has a driver model, a unified model for drivers.
2796 If you are adding a new driver, plumb it into driver model. If there
2797 is no uclass available, you are encouraged to create one. See
2801 Configuring the Linux kernel:
2802 -----------------------------
2804 No specific requirements for U-Boot. Make sure you have some root
2805 device (initial ramdisk, NFS) for your target system.
2808 Building a Linux Image:
2809 -----------------------
2811 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2812 not used. If you use recent kernel source, a new build target
2813 "uImage" will exist which automatically builds an image usable by
2814 U-Boot. Most older kernels also have support for a "pImage" target,
2815 which was introduced for our predecessor project PPCBoot and uses a
2816 100% compatible format.
2820 make TQM850L_defconfig
2825 The "uImage" build target uses a special tool (in 'tools/mkimage') to
2826 encapsulate a compressed Linux kernel image with header information,
2827 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2829 * build a standard "vmlinux" kernel image (in ELF binary format):
2831 * convert the kernel into a raw binary image:
2833 ${CROSS_COMPILE}-objcopy -O binary \
2834 -R .note -R .comment \
2835 -S vmlinux linux.bin
2837 * compress the binary image:
2841 * package compressed binary image for U-Boot:
2843 mkimage -A ppc -O linux -T kernel -C gzip \
2844 -a 0 -e 0 -n "Linux Kernel Image" \
2845 -d linux.bin.gz uImage
2848 The "mkimage" tool can also be used to create ramdisk images for use
2849 with U-Boot, either separated from the Linux kernel image, or
2850 combined into one file. "mkimage" encapsulates the images with a 64
2851 byte header containing information about target architecture,
2852 operating system, image type, compression method, entry points, time
2853 stamp, CRC32 checksums, etc.
2855 "mkimage" can be called in two ways: to verify existing images and
2856 print the header information, or to build new images.
2858 In the first form (with "-l" option) mkimage lists the information
2859 contained in the header of an existing U-Boot image; this includes
2860 checksum verification:
2862 tools/mkimage -l image
2863 -l ==> list image header information
2865 The second form (with "-d" option) is used to build a U-Boot image
2866 from a "data file" which is used as image payload:
2868 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
2869 -n name -d data_file image
2870 -A ==> set architecture to 'arch'
2871 -O ==> set operating system to 'os'
2872 -T ==> set image type to 'type'
2873 -C ==> set compression type 'comp'
2874 -a ==> set load address to 'addr' (hex)
2875 -e ==> set entry point to 'ep' (hex)
2876 -n ==> set image name to 'name'
2877 -d ==> use image data from 'datafile'
2879 Right now, all Linux kernels for PowerPC systems use the same load
2880 address (0x00000000), but the entry point address depends on the
2883 - 2.2.x kernels have the entry point at 0x0000000C,
2884 - 2.3.x and later kernels have the entry point at 0x00000000.
2886 So a typical call to build a U-Boot image would read:
2888 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2889 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
2890 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
2891 > examples/uImage.TQM850L
2892 Image Name: 2.4.4 kernel for TQM850L
2893 Created: Wed Jul 19 02:34:59 2000
2894 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2895 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2896 Load Address: 0x00000000
2897 Entry Point: 0x00000000
2899 To verify the contents of the image (or check for corruption):
2901 -> tools/mkimage -l examples/uImage.TQM850L
2902 Image Name: 2.4.4 kernel for TQM850L
2903 Created: Wed Jul 19 02:34:59 2000
2904 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2905 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2906 Load Address: 0x00000000
2907 Entry Point: 0x00000000
2909 NOTE: for embedded systems where boot time is critical you can trade
2910 speed for memory and install an UNCOMPRESSED image instead: this
2911 needs more space in Flash, but boots much faster since it does not
2912 need to be uncompressed:
2914 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
2915 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2916 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
2917 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
2918 > examples/uImage.TQM850L-uncompressed
2919 Image Name: 2.4.4 kernel for TQM850L
2920 Created: Wed Jul 19 02:34:59 2000
2921 Image Type: PowerPC Linux Kernel Image (uncompressed)
2922 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
2923 Load Address: 0x00000000
2924 Entry Point: 0x00000000
2927 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
2928 when your kernel is intended to use an initial ramdisk:
2930 -> tools/mkimage -n 'Simple Ramdisk Image' \
2931 > -A ppc -O linux -T ramdisk -C gzip \
2932 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
2933 Image Name: Simple Ramdisk Image
2934 Created: Wed Jan 12 14:01:50 2000
2935 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2936 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
2937 Load Address: 0x00000000
2938 Entry Point: 0x00000000
2940 The "dumpimage" tool can be used to disassemble or list the contents of images
2941 built by mkimage. See dumpimage's help output (-h) for details.
2943 Installing a Linux Image:
2944 -------------------------
2946 To downloading a U-Boot image over the serial (console) interface,
2947 you must convert the image to S-Record format:
2949 objcopy -I binary -O srec examples/image examples/image.srec
2951 The 'objcopy' does not understand the information in the U-Boot
2952 image header, so the resulting S-Record file will be relative to
2953 address 0x00000000. To load it to a given address, you need to
2954 specify the target address as 'offset' parameter with the 'loads'
2957 Example: install the image to address 0x40100000 (which on the
2958 TQM8xxL is in the first Flash bank):
2960 => erase 40100000 401FFFFF
2966 ## Ready for S-Record download ...
2967 ~>examples/image.srec
2968 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
2970 15989 15990 15991 15992
2971 [file transfer complete]
2973 ## Start Addr = 0x00000000
2976 You can check the success of the download using the 'iminfo' command;
2977 this includes a checksum verification so you can be sure no data
2978 corruption happened:
2982 ## Checking Image at 40100000 ...
2983 Image Name: 2.2.13 for initrd on TQM850L
2984 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2985 Data Size: 335725 Bytes = 327 kB = 0 MB
2986 Load Address: 00000000
2987 Entry Point: 0000000c
2988 Verifying Checksum ... OK
2994 The "bootm" command is used to boot an application that is stored in
2995 memory (RAM or Flash). In case of a Linux kernel image, the contents
2996 of the "bootargs" environment variable is passed to the kernel as
2997 parameters. You can check and modify this variable using the
2998 "printenv" and "setenv" commands:
3001 => printenv bootargs
3002 bootargs=root=/dev/ram
3004 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3006 => printenv bootargs
3007 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3010 ## Booting Linux kernel at 40020000 ...
3011 Image Name: 2.2.13 for NFS on TQM850L
3012 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3013 Data Size: 381681 Bytes = 372 kB = 0 MB
3014 Load Address: 00000000
3015 Entry Point: 0000000c
3016 Verifying Checksum ... OK
3017 Uncompressing Kernel Image ... OK
3018 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
3019 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3020 time_init: decrementer frequency = 187500000/60
3021 Calibrating delay loop... 49.77 BogoMIPS
3022 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3025 If you want to boot a Linux kernel with initial RAM disk, you pass
3026 the memory addresses of both the kernel and the initrd image (PPBCOOT
3027 format!) to the "bootm" command:
3029 => imi 40100000 40200000
3031 ## Checking Image at 40100000 ...
3032 Image Name: 2.2.13 for initrd on TQM850L
3033 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3034 Data Size: 335725 Bytes = 327 kB = 0 MB
3035 Load Address: 00000000
3036 Entry Point: 0000000c
3037 Verifying Checksum ... OK
3039 ## Checking Image at 40200000 ...
3040 Image Name: Simple Ramdisk Image
3041 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3042 Data Size: 566530 Bytes = 553 kB = 0 MB
3043 Load Address: 00000000
3044 Entry Point: 00000000
3045 Verifying Checksum ... OK
3047 => bootm 40100000 40200000
3048 ## Booting Linux kernel at 40100000 ...
3049 Image Name: 2.2.13 for initrd on TQM850L
3050 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3051 Data Size: 335725 Bytes = 327 kB = 0 MB
3052 Load Address: 00000000
3053 Entry Point: 0000000c
3054 Verifying Checksum ... OK
3055 Uncompressing Kernel Image ... OK
3056 ## Loading RAMDisk Image at 40200000 ...
3057 Image Name: Simple Ramdisk Image
3058 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
3059 Data Size: 566530 Bytes = 553 kB = 0 MB
3060 Load Address: 00000000
3061 Entry Point: 00000000
3062 Verifying Checksum ... OK
3063 Loading Ramdisk ... OK
3064 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
3065 Boot arguments: root=/dev/ram
3066 time_init: decrementer frequency = 187500000/60
3067 Calibrating delay loop... 49.77 BogoMIPS
3069 RAMDISK: Compressed image found at block 0
3070 VFS: Mounted root (ext2 filesystem).
3074 Boot Linux and pass a flat device tree:
3077 First, U-Boot must be compiled with the appropriate defines. See the section
3078 titled "Linux Kernel Interface" above for a more in depth explanation. The
3079 following is an example of how to start a kernel and pass an updated
3085 oft=oftrees/mpc8540ads.dtb
3086 => tftp $oftaddr $oft
3087 Speed: 1000, full duplex
3089 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
3090 Filename 'oftrees/mpc8540ads.dtb'.
3091 Load address: 0x300000
3094 Bytes transferred = 4106 (100a hex)
3095 => tftp $loadaddr $bootfile
3096 Speed: 1000, full duplex
3098 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
3100 Load address: 0x200000
3101 Loading:############
3103 Bytes transferred = 1029407 (fb51f hex)
3108 => bootm $loadaddr - $oftaddr
3109 ## Booting image at 00200000 ...
3110 Image Name: Linux-2.6.17-dirty
3111 Image Type: PowerPC Linux Kernel Image (gzip compressed)
3112 Data Size: 1029343 Bytes = 1005.2 kB
3113 Load Address: 00000000
3114 Entry Point: 00000000
3115 Verifying Checksum ... OK
3116 Uncompressing Kernel Image ... OK
3117 Booting using flat device tree at 0x300000
3118 Using MPC85xx ADS machine description
3119 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
3123 More About U-Boot Image Types:
3124 ------------------------------
3126 U-Boot supports the following image types:
3128 "Standalone Programs" are directly runnable in the environment
3129 provided by U-Boot; it is expected that (if they behave
3130 well) you can continue to work in U-Boot after return from
3131 the Standalone Program.
3132 "OS Kernel Images" are usually images of some Embedded OS which
3133 will take over control completely. Usually these programs
3134 will install their own set of exception handlers, device
3135 drivers, set up the MMU, etc. - this means, that you cannot
3136 expect to re-enter U-Boot except by resetting the CPU.
3137 "RAMDisk Images" are more or less just data blocks, and their
3138 parameters (address, size) are passed to an OS kernel that is
3140 "Multi-File Images" contain several images, typically an OS
3141 (Linux) kernel image and one or more data images like
3142 RAMDisks. This construct is useful for instance when you want
3143 to boot over the network using BOOTP etc., where the boot
3144 server provides just a single image file, but you want to get
3145 for instance an OS kernel and a RAMDisk image.
3147 "Multi-File Images" start with a list of image sizes, each
3148 image size (in bytes) specified by an "uint32_t" in network
3149 byte order. This list is terminated by an "(uint32_t)0".
3150 Immediately after the terminating 0 follow the images, one by
3151 one, all aligned on "uint32_t" boundaries (size rounded up to
3152 a multiple of 4 bytes).
3154 "Firmware Images" are binary images containing firmware (like
3155 U-Boot or FPGA images) which usually will be programmed to
3158 "Script files" are command sequences that will be executed by
3159 U-Boot's command interpreter; this feature is especially
3160 useful when you configure U-Boot to use a real shell (hush)
3161 as command interpreter.
3163 Booting the Linux zImage:
3164 -------------------------
3166 On some platforms, it's possible to boot Linux zImage. This is done
3167 using the "bootz" command. The syntax of "bootz" command is the same
3168 as the syntax of "bootm" command.
3170 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
3171 kernel with raw initrd images. The syntax is slightly different, the
3172 address of the initrd must be augmented by it's size, in the following
3173 format: "<initrd addres>:<initrd size>".
3179 One of the features of U-Boot is that you can dynamically load and
3180 run "standalone" applications, which can use some resources of
3181 U-Boot like console I/O functions or interrupt services.
3183 Two simple examples are included with the sources:
3188 'examples/hello_world.c' contains a small "Hello World" Demo
3189 application; it is automatically compiled when you build U-Boot.
3190 It's configured to run at address 0x00040004, so you can play with it
3194 ## Ready for S-Record download ...
3195 ~>examples/hello_world.srec
3196 1 2 3 4 5 6 7 8 9 10 11 ...
3197 [file transfer complete]
3199 ## Start Addr = 0x00040004
3201 => go 40004 Hello World! This is a test.
3202 ## Starting application at 0x00040004 ...
3213 Hit any key to exit ...
3215 ## Application terminated, rc = 0x0
3217 Another example, which demonstrates how to register a CPM interrupt
3218 handler with the U-Boot code, can be found in 'examples/timer.c'.
3219 Here, a CPM timer is set up to generate an interrupt every second.
3220 The interrupt service routine is trivial, just printing a '.'
3221 character, but this is just a demo program. The application can be
3222 controlled by the following keys:
3224 ? - print current values og the CPM Timer registers
3225 b - enable interrupts and start timer
3226 e - stop timer and disable interrupts
3227 q - quit application
3230 ## Ready for S-Record download ...
3231 ~>examples/timer.srec
3232 1 2 3 4 5 6 7 8 9 10 11 ...
3233 [file transfer complete]
3235 ## Start Addr = 0x00040004
3238 ## Starting application at 0x00040004 ...
3241 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
3244 [q, b, e, ?] Set interval 1000000 us
3247 [q, b, e, ?] ........
3248 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
3251 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
3254 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
3257 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
3259 [q, b, e, ?] ...Stopping timer
3261 [q, b, e, ?] ## Application terminated, rc = 0x0
3267 Over time, many people have reported problems when trying to use the
3268 "minicom" terminal emulation program for serial download. I (wd)
3269 consider minicom to be broken, and recommend not to use it. Under
3270 Unix, I recommend to use C-Kermit for general purpose use (and
3271 especially for kermit binary protocol download ("loadb" command), and
3272 use "cu" for S-Record download ("loads" command). See
3273 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
3274 for help with kermit.
3277 Nevertheless, if you absolutely want to use it try adding this
3278 configuration to your "File transfer protocols" section:
3280 Name Program Name U/D FullScr IO-Red. Multi
3281 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
3282 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
3288 Starting at version 0.9.2, U-Boot supports NetBSD both as host
3289 (build U-Boot) and target system (boots NetBSD/mpc8xx).
3291 Building requires a cross environment; it is known to work on
3292 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
3293 need gmake since the Makefiles are not compatible with BSD make).
3294 Note that the cross-powerpc package does not install include files;
3295 attempting to build U-Boot will fail because <machine/ansi.h> is
3296 missing. This file has to be installed and patched manually:
3298 # cd /usr/pkg/cross/powerpc-netbsd/include
3300 # ln -s powerpc machine
3301 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
3302 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
3304 Native builds *don't* work due to incompatibilities between native
3305 and U-Boot include files.
3307 Booting assumes that (the first part of) the image booted is a
3308 stage-2 loader which in turn loads and then invokes the kernel
3309 proper. Loader sources will eventually appear in the NetBSD source
3310 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
3311 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
3314 Implementation Internals:
3315 =========================
3317 The following is not intended to be a complete description of every
3318 implementation detail. However, it should help to understand the
3319 inner workings of U-Boot and make it easier to port it to custom
3323 Initial Stack, Global Data:
3324 ---------------------------
3326 The implementation of U-Boot is complicated by the fact that U-Boot
3327 starts running out of ROM (flash memory), usually without access to
3328 system RAM (because the memory controller is not initialized yet).
3329 This means that we don't have writable Data or BSS segments, and BSS
3330 is not initialized as zero. To be able to get a C environment working
3331 at all, we have to allocate at least a minimal stack. Implementation
3332 options for this are defined and restricted by the CPU used: Some CPU
3333 models provide on-chip memory (like the IMMR area on MPC8xx and
3334 MPC826x processors), on others (parts of) the data cache can be
3335 locked as (mis-) used as memory, etc.
3337 Chris Hallinan posted a good summary of these issues to the
3338 U-Boot mailing list:
3340 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
3341 From: "Chris Hallinan" <clh@net1plus.com>
3342 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
3345 Correct me if I'm wrong, folks, but the way I understand it
3346 is this: Using DCACHE as initial RAM for Stack, etc, does not
3347 require any physical RAM backing up the cache. The cleverness
3348 is that the cache is being used as a temporary supply of
3349 necessary storage before the SDRAM controller is setup. It's
3350 beyond the scope of this list to explain the details, but you
3351 can see how this works by studying the cache architecture and
3352 operation in the architecture and processor-specific manuals.
3354 OCM is On Chip Memory, which I believe the 405GP has 4K. It
3355 is another option for the system designer to use as an
3356 initial stack/RAM area prior to SDRAM being available. Either
3357 option should work for you. Using CS 4 should be fine if your
3358 board designers haven't used it for something that would
3359 cause you grief during the initial boot! It is frequently not
3362 CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
3363 with your processor/board/system design. The default value
3364 you will find in any recent u-boot distribution in
3365 walnut.h should work for you. I'd set it to a value larger
3366 than your SDRAM module. If you have a 64MB SDRAM module, set
3367 it above 400_0000. Just make sure your board has no resources
3368 that are supposed to respond to that address! That code in
3369 start.S has been around a while and should work as is when
3370 you get the config right.
3375 It is essential to remember this, since it has some impact on the C
3376 code for the initialization procedures:
3378 * Initialized global data (data segment) is read-only. Do not attempt
3381 * Do not use any uninitialized global data (or implicitly initialized
3382 as zero data - BSS segment) at all - this is undefined, initiali-
3383 zation is performed later (when relocating to RAM).
3385 * Stack space is very limited. Avoid big data buffers or things like
3388 Having only the stack as writable memory limits means we cannot use
3389 normal global data to share information between the code. But it
3390 turned out that the implementation of U-Boot can be greatly
3391 simplified by making a global data structure (gd_t) available to all
3392 functions. We could pass a pointer to this data as argument to _all_
3393 functions, but this would bloat the code. Instead we use a feature of
3394 the GCC compiler (Global Register Variables) to share the data: we
3395 place a pointer (gd) to the global data into a register which we
3396 reserve for this purpose.
3398 When choosing a register for such a purpose we are restricted by the
3399 relevant (E)ABI specifications for the current architecture, and by
3400 GCC's implementation.
3402 For PowerPC, the following registers have specific use:
3404 R2: reserved for system use
3405 R3-R4: parameter passing and return values
3406 R5-R10: parameter passing
3407 R13: small data area pointer
3411 (U-Boot also uses R12 as internal GOT pointer. r12
3412 is a volatile register so r12 needs to be reset when
3413 going back and forth between asm and C)
3415 ==> U-Boot will use R2 to hold a pointer to the global data
3417 Note: on PPC, we could use a static initializer (since the
3418 address of the global data structure is known at compile time),
3419 but it turned out that reserving a register results in somewhat
3420 smaller code - although the code savings are not that big (on
3421 average for all boards 752 bytes for the whole U-Boot image,
3422 624 text + 127 data).
3424 On ARM, the following registers are used:
3426 R0: function argument word/integer result
3427 R1-R3: function argument word
3428 R9: platform specific
3429 R10: stack limit (used only if stack checking is enabled)
3430 R11: argument (frame) pointer
3431 R12: temporary workspace
3434 R15: program counter
3436 ==> U-Boot will use R9 to hold a pointer to the global data
3438 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
3440 On Nios II, the ABI is documented here:
3441 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
3443 ==> U-Boot will use gp to hold a pointer to the global data
3445 Note: on Nios II, we give "-G0" option to gcc and don't use gp
3446 to access small data sections, so gp is free.
3448 On NDS32, the following registers are used:
3450 R0-R1: argument/return
3452 R15: temporary register for assembler
3453 R16: trampoline register
3454 R28: frame pointer (FP)
3455 R29: global pointer (GP)
3456 R30: link register (LP)
3457 R31: stack pointer (SP)
3458 PC: program counter (PC)
3460 ==> U-Boot will use R10 to hold a pointer to the global data
3462 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
3463 or current versions of GCC may "optimize" the code too much.
3465 On RISC-V, the following registers are used:
3467 x0: hard-wired zero (zero)
3468 x1: return address (ra)
3469 x2: stack pointer (sp)
3470 x3: global pointer (gp)
3471 x4: thread pointer (tp)
3472 x5: link register (t0)
3473 x8: frame pointer (fp)
3474 x10-x11: arguments/return values (a0-1)
3475 x12-x17: arguments (a2-7)
3476 x28-31: temporaries (t3-6)
3477 pc: program counter (pc)
3479 ==> U-Boot will use gp to hold a pointer to the global data
3484 U-Boot runs in system state and uses physical addresses, i.e. the
3485 MMU is not used either for address mapping nor for memory protection.
3487 The available memory is mapped to fixed addresses using the memory
3488 controller. In this process, a contiguous block is formed for each
3489 memory type (Flash, SDRAM, SRAM), even when it consists of several
3490 physical memory banks.
3492 U-Boot is installed in the first 128 kB of the first Flash bank (on
3493 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
3494 booting and sizing and initializing DRAM, the code relocates itself
3495 to the upper end of DRAM. Immediately below the U-Boot code some
3496 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
3497 configuration setting]. Below that, a structure with global Board
3498 Info data is placed, followed by the stack (growing downward).
3500 Additionally, some exception handler code is copied to the low 8 kB
3501 of DRAM (0x00000000 ... 0x00001FFF).
3503 So a typical memory configuration with 16 MB of DRAM could look like
3506 0x0000 0000 Exception Vector code
3509 0x0000 2000 Free for Application Use
3515 0x00FB FF20 Monitor Stack (Growing downward)
3516 0x00FB FFAC Board Info Data and permanent copy of global data
3517 0x00FC 0000 Malloc Arena
3520 0x00FE 0000 RAM Copy of Monitor Code
3521 ... eventually: LCD or video framebuffer
3522 ... eventually: pRAM (Protected RAM - unchanged by reset)
3523 0x00FF FFFF [End of RAM]
3526 System Initialization:
3527 ----------------------
3529 In the reset configuration, U-Boot starts at the reset entry point
3530 (on most PowerPC systems at address 0x00000100). Because of the reset
3531 configuration for CS0# this is a mirror of the on board Flash memory.
3532 To be able to re-map memory U-Boot then jumps to its link address.
3533 To be able to implement the initialization code in C, a (small!)
3534 initial stack is set up in the internal Dual Ported RAM (in case CPUs
3535 which provide such a feature like), or in a locked part of the data
3536 cache. After that, U-Boot initializes the CPU core, the caches and
3539 Next, all (potentially) available memory banks are mapped using a
3540 preliminary mapping. For example, we put them on 512 MB boundaries
3541 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
3542 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
3543 programmed for SDRAM access. Using the temporary configuration, a
3544 simple memory test is run that determines the size of the SDRAM
3547 When there is more than one SDRAM bank, and the banks are of
3548 different size, the largest is mapped first. For equal size, the first
3549 bank (CS2#) is mapped first. The first mapping is always for address
3550 0x00000000, with any additional banks following immediately to create
3551 contiguous memory starting from 0.
3553 Then, the monitor installs itself at the upper end of the SDRAM area
3554 and allocates memory for use by malloc() and for the global Board
3555 Info data; also, the exception vector code is copied to the low RAM
3556 pages, and the final stack is set up.
3558 Only after this relocation will you have a "normal" C environment;
3559 until that you are restricted in several ways, mostly because you are
3560 running from ROM, and because the code will have to be relocated to a
3564 U-Boot Porting Guide:
3565 ----------------------
3567 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
3571 int main(int argc, char *argv[])
3573 sighandler_t no_more_time;
3575 signal(SIGALRM, no_more_time);
3576 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
3578 if (available_money > available_manpower) {
3579 Pay consultant to port U-Boot;
3583 Download latest U-Boot source;
3585 Subscribe to u-boot mailing list;
3588 email("Hi, I am new to U-Boot, how do I get started?");
3591 Read the README file in the top level directory;
3592 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
3593 Read applicable doc/README.*;
3594 Read the source, Luke;
3595 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
3598 if (available_money > toLocalCurrency ($2500))
3601 Add a lot of aggravation and time;
3603 if (a similar board exists) { /* hopefully... */
3604 cp -a board/<similar> board/<myboard>
3605 cp include/configs/<similar>.h include/configs/<myboard>.h
3607 Create your own board support subdirectory;
3608 Create your own board include/configs/<myboard>.h file;
3610 Edit new board/<myboard> files
3611 Edit new include/configs/<myboard>.h
3616 Add / modify source code;
3620 email("Hi, I am having problems...");
3622 Send patch file to the U-Boot email list;
3623 if (reasonable critiques)
3624 Incorporate improvements from email list code review;
3626 Defend code as written;
3632 void no_more_time (int sig)
3641 All contributions to U-Boot should conform to the Linux kernel
3642 coding style; see the kernel coding style guide at
3643 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
3644 script "scripts/Lindent" in your Linux kernel source directory.
3646 Source files originating from a different project (for example the
3647 MTD subsystem) are generally exempt from these guidelines and are not
3648 reformatted to ease subsequent migration to newer versions of those
3651 Please note that U-Boot is implemented in C (and to some small parts in
3652 Assembler); no C++ is used, so please do not use C++ style comments (//)
3655 Please also stick to the following formatting rules:
3656 - remove any trailing white space
3657 - use TAB characters for indentation and vertical alignment, not spaces
3658 - make sure NOT to use DOS '\r\n' line feeds
3659 - do not add more than 2 consecutive empty lines to source files
3660 - do not add trailing empty lines to source files
3662 Submissions which do not conform to the standards may be returned
3663 with a request to reformat the changes.
3669 Since the number of patches for U-Boot is growing, we need to
3670 establish some rules. Submissions which do not conform to these rules
3671 may be rejected, even when they contain important and valuable stuff.
3673 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
3675 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
3676 see https://lists.denx.de/listinfo/u-boot
3678 When you send a patch, please include the following information with
3681 * For bug fixes: a description of the bug and how your patch fixes
3682 this bug. Please try to include a way of demonstrating that the
3683 patch actually fixes something.
3685 * For new features: a description of the feature and your
3688 * For major contributions, add a MAINTAINERS file with your
3689 information and associated file and directory references.
3691 * When you add support for a new board, don't forget to add a
3692 maintainer e-mail address to the boards.cfg file, too.
3694 * If your patch adds new configuration options, don't forget to
3695 document these in the README file.
3697 * The patch itself. If you are using git (which is *strongly*
3698 recommended) you can easily generate the patch using the
3699 "git format-patch". If you then use "git send-email" to send it to
3700 the U-Boot mailing list, you will avoid most of the common problems
3701 with some other mail clients.
3703 If you cannot use git, use "diff -purN OLD NEW". If your version of
3704 diff does not support these options, then get the latest version of
3707 The current directory when running this command shall be the parent
3708 directory of the U-Boot source tree (i. e. please make sure that
3709 your patch includes sufficient directory information for the
3712 We prefer patches as plain text. MIME attachments are discouraged,
3713 and compressed attachments must not be used.
3715 * If one logical set of modifications affects or creates several
3716 files, all these changes shall be submitted in a SINGLE patch file.
3718 * Changesets that contain different, unrelated modifications shall be
3719 submitted as SEPARATE patches, one patch per changeset.
3724 * Before sending the patch, run the buildman script on your patched
3725 source tree and make sure that no errors or warnings are reported
3726 for any of the boards.
3728 * Keep your modifications to the necessary minimum: A patch
3729 containing several unrelated changes or arbitrary reformats will be
3730 returned with a request to re-formatting / split it.
3732 * If you modify existing code, make sure that your new code does not
3733 add to the memory footprint of the code ;-) Small is beautiful!
3734 When adding new features, these should compile conditionally only
3735 (using #ifdef), and the resulting code with the new feature
3736 disabled must not need more memory than the old code without your
3739 * Remember that there is a size limit of 100 kB per message on the
3740 u-boot mailing list. Bigger patches will be moderated. If they are
3741 reasonable and not too big, they will be acknowledged. But patches
3742 bigger than the size limit should be avoided.