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 /nios2 Files generic to Altera NIOS2 architecture
138 /powerpc Files generic to PowerPC architecture
139 /riscv Files generic to RISC-V architecture
140 /sandbox Files generic to HW-independent "sandbox"
141 /sh Files generic to SH architecture
142 /x86 Files generic to x86 architecture
143 /xtensa Files generic to Xtensa architecture
144 /api Machine/arch-independent API for external apps
145 /board Board-dependent files
146 /boot Support for images and booting
147 /cmd U-Boot commands functions
148 /common Misc architecture-independent functions
149 /configs Board default configuration files
150 /disk Code for disk drive partition handling
151 /doc Documentation (a mix of ReST and READMEs)
152 /drivers Device drivers
153 /dts Makefile for building internal U-Boot fdt.
154 /env Environment support
155 /examples Example code for standalone applications, etc.
156 /fs Filesystem code (cramfs, ext2, jffs2, etc.)
157 /include Header Files
158 /lib Library routines generic to all architectures
159 /Licenses Various license files
161 /post Power On Self Test
162 /scripts Various build scripts and Makefiles
163 /test Various unit test files
164 /tools Tools to build and sign FIT images, etc.
166 Software Configuration:
167 =======================
169 Selection of Processor Architecture and Board Type:
170 ---------------------------------------------------
172 For all supported boards there are ready-to-use default
173 configurations available; just type "make <board_name>_defconfig".
175 Example: For a TQM823L module type:
178 make TQM823L_defconfig
180 Note: If you're looking for the default configuration file for a board
181 you're sure used to be there but is now missing, check the file
182 doc/README.scrapyard for a list of no longer supported boards.
187 U-Boot can be built natively to run on a Linux host using the 'sandbox'
188 board. This allows feature development which is not board- or architecture-
189 specific to be undertaken on a native platform. The sandbox is also used to
190 run some of U-Boot's tests.
192 See doc/arch/sandbox.rst for more details.
195 Board Initialisation Flow:
196 --------------------------
198 This is the intended start-up flow for boards. This should apply for both
199 SPL and U-Boot proper (i.e. they both follow the same rules).
201 Note: "SPL" stands for "Secondary Program Loader," which is explained in
202 more detail later in this file.
204 At present, SPL mostly uses a separate code path, but the function names
205 and roles of each function are the same. Some boards or architectures
206 may not conform to this. At least most ARM boards which use
207 CONFIG_SPL_FRAMEWORK conform to this.
209 Execution typically starts with an architecture-specific (and possibly
210 CPU-specific) start.S file, such as:
212 - arch/arm/cpu/armv7/start.S
213 - arch/powerpc/cpu/mpc83xx/start.S
214 - arch/mips/cpu/start.S
216 and so on. From there, three functions are called; the purpose and
217 limitations of each of these functions are described below.
220 - purpose: essential init to permit execution to reach board_init_f()
221 - no global_data or BSS
222 - there is no stack (ARMv7 may have one but it will soon be removed)
223 - must not set up SDRAM or use console
224 - must only do the bare minimum to allow execution to continue to
226 - this is almost never needed
227 - return normally from this function
230 - purpose: set up the machine ready for running board_init_r():
231 i.e. SDRAM and serial UART
232 - global_data is available
234 - BSS is not available, so you cannot use global/static variables,
235 only stack variables and global_data
237 Non-SPL-specific notes:
238 - dram_init() is called to set up DRAM. If already done in SPL this
242 - you can override the entire board_init_f() function with your own
244 - preloader_console_init() can be called here in extremis
245 - should set up SDRAM, and anything needed to make the UART work
246 - there is no need to clear BSS, it will be done by crt0.S
247 - for specific scenarios on certain architectures an early BSS *can*
248 be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
249 of BSS prior to entering board_init_f()) but doing so is discouraged.
250 Instead it is strongly recommended to architect any code changes
251 or additions such to not depend on the availability of BSS during
252 board_init_f() as indicated in other sections of this README to
253 maintain compatibility and consistency across the entire code base.
254 - must return normally from this function (don't call board_init_r()
257 Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
258 this point the stack and global_data are relocated to below
259 CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
263 - purpose: main execution, common code
264 - global_data is available
266 - BSS is available, all static/global variables can be used
267 - execution eventually continues to main_loop()
269 Non-SPL-specific notes:
270 - U-Boot is relocated to the top of memory and is now running from
274 - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
275 CONFIG_SYS_FSL_HAS_CCI400
277 Defined For SoC that has cache coherent interconnect
280 CONFIG_SYS_FSL_HAS_CCN504
282 Defined for SoC that has cache coherent interconnect CCN-504
284 The following options need to be configured:
286 - CPU Type: Define exactly one, e.g. CONFIG_MPC85XX.
288 - Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS.
293 Specifies that the core is a 64-bit PowerPC implementation (implements
294 the "64" category of the Power ISA). This is necessary for ePAPR
295 compliance, among other possible reasons.
297 CONFIG_SYS_FSL_ERRATUM_A004510
299 Enables a workaround for erratum A004510. If set,
300 then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
301 CFG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
303 CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
304 CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
306 Defines one or two SoC revisions (low 8 bits of SVR)
307 for which the A004510 workaround should be applied.
309 The rest of SVR is either not relevant to the decision
310 of whether the erratum is present (e.g. p2040 versus
311 p2041) or is implied by the build target, which controls
312 whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
314 See Freescale App Note 4493 for more information about
317 CFG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
319 This is the value to write into CCSR offset 0x18600
320 according to the A004510 workaround.
322 CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
323 Single Source Clock is clocking mode present in some of FSL SoC's.
324 In this mode, a single differential clock is used to supply
325 clocks to the sysclock, ddrclock and usbclock.
327 - Generic CPU options:
330 Freescale DDR driver in use. This type of DDR controller is
331 found in mpc83xx, mpc85xx as well as some ARM core SoCs.
334 Freescale DDR memory-mapped register base.
336 CONFIG_SYS_FSL_IFC_CLK_DIV
337 Defines divider of platform clock(clock input to IFC controller).
339 CONFIG_SYS_FSL_LBC_CLK_DIV
340 Defines divider of platform clock(clock input to eLBC controller).
342 CFG_SYS_FSL_DDR_SDRAM_BASE_PHY
343 Physical address from the view of DDR controllers. It is the
344 same as CONFIG_SYS_DDR_SDRAM_BASE for all Power SoCs. But
345 it could be different for ARM SoCs.
348 CONFIG_XWAY_SWAP_BYTES
350 Enable compilation of tools/xway-swap-bytes needed for Lantiq
351 XWAY SoCs for booting from NOR flash. The U-Boot image needs to
352 be swapped if a flash programmer is used.
355 CONFIG_SYS_EXCEPTION_VECTORS_HIGH
357 Select high exception vectors of the ARM core, e.g., do not
358 clear the V bit of the c1 register of CP15.
361 Generic timer clock source frequency.
363 COUNTER_FREQUENCY_REAL
364 Generic timer clock source frequency if the real clock is
365 different from COUNTER_FREQUENCY, and can only be determined
369 CONFIG_TEGRA_SUPPORT_NON_SECURE
371 Support executing U-Boot in non-secure (NS) mode. Certain
372 impossible actions will be skipped if the CPU is in NS mode,
373 such as ARM architectural timer initialization.
375 - Linux Kernel Interface:
376 CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]
378 When transferring memsize parameter to Linux, some versions
379 expect it to be in bytes, others in MB.
380 Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
384 New kernel versions are expecting firmware settings to be
385 passed using flattened device trees (based on open firmware
389 * New libfdt-based support
390 * Adds the "fdt" command
391 * The bootm command automatically updates the fdt
393 OF_TBCLK - The timebase frequency.
395 boards with QUICC Engines require OF_QE to set UCC MAC
400 U-Boot can detect if an IDE device is present or not.
401 If not, and this new config option is activated, U-Boot
402 removes the ATA node from the DTS before booting Linux,
403 so the Linux IDE driver does not probe the device and
404 crash. This is needed for buggy hardware (uc101) where
405 no pull down resistor is connected to the signal IDE5V_DD7.
407 - vxWorks boot parameters:
409 bootvx constructs a valid bootline using the following
410 environments variables: bootdev, bootfile, ipaddr, netmask,
411 serverip, gatewayip, hostname, othbootargs.
412 It loads the vxWorks image pointed bootfile.
414 Note: If a "bootargs" environment is defined, it will override
415 the defaults discussed just above.
417 - Cache Configuration for ARM:
418 CONFIG_SYS_PL310_BASE - Physical base address of PL310
419 controller register space
424 If you have Amba PrimeCell PL011 UARTs, set this variable to
425 the clock speed of the UARTs.
429 If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
430 define this to a list of base addresses for each (supported)
431 port. See e.g. include/configs/versatile.h
433 CONFIG_SERIAL_HW_FLOW_CONTROL
435 Define this variable to enable hw flow control in serial driver.
436 Current user of this option is drivers/serial/nsl16550.c driver
438 - Removal of commands
439 If no commands are needed to boot, you can disable
440 CONFIG_CMDLINE to remove them. In this case, the command line
441 will not be available, and when U-Boot wants to execute the
442 boot command (on start-up) it will call board_run_command()
443 instead. This can reduce image size significantly for very
444 simple boot procedures.
446 - Regular expression support:
448 If this variable is defined, U-Boot is linked against
449 the SLRE (Super Light Regular Expression) library,
450 which adds regex support to some commands, as for
451 example "env grep" and "setexpr".
454 CONFIG_SYS_WATCHDOG_FREQ
455 Some platforms automatically call WATCHDOG_RESET()
456 from the timer interrupt handler every
457 CONFIG_SYS_WATCHDOG_FREQ interrupts. If not set by the
458 board configuration file, a default of CONFIG_SYS_HZ/2
459 (i.e. 500) is used. Setting CONFIG_SYS_WATCHDOG_FREQ
460 to 0 disables calling WATCHDOG_RESET() from the timer
465 When CONFIG_CMD_DATE is selected, the type of the RTC
466 has to be selected, too. Define exactly one of the
469 CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
470 CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
471 CONFIG_RTC_MC146818 - use MC146818 RTC
472 CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
473 CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
474 CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
475 CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
476 CONFIG_RTC_DS164x - use Dallas DS164x RTC
477 CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
478 CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
479 CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
480 CONFIG_SYS_RV3029_TCR - enable trickle charger on
483 Note that if the RTC uses I2C, then the I2C interface
484 must also be configured. See I2C Support, below.
487 CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
489 The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
490 chip-ngpio pairs that tell the PCA953X driver the number of
491 pins supported by a particular chip.
493 Note that if the GPIO device uses I2C, then the I2C interface
494 must also be configured. See I2C Support, below.
497 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
498 accesses and can checksum them or write a list of them out
499 to memory. See the 'iotrace' command for details. This is
500 useful for testing device drivers since it can confirm that
501 the driver behaves the same way before and after a code
502 change. Currently this is supported on sandbox and arm. To
503 add support for your architecture, add '#include <iotrace.h>'
504 to the bottom of arch/<arch>/include/asm/io.h and test.
506 Example output from the 'iotrace stats' command is below.
507 Note that if the trace buffer is exhausted, the checksum will
508 still continue to operate.
511 Start: 10000000 (buffer start address)
512 Size: 00010000 (buffer size)
513 Offset: 00000120 (current buffer offset)
514 Output: 10000120 (start + offset)
515 Count: 00000018 (number of trace records)
516 CRC32: 9526fb66 (CRC32 of all trace records)
520 When CONFIG_TIMESTAMP is selected, the timestamp
521 (date and time) of an image is printed by image
522 commands like bootm or iminfo. This option is
523 automatically enabled when you select CONFIG_CMD_DATE .
525 - Partition Labels (disklabels) Supported:
526 Zero or more of the following:
527 CONFIG_MAC_PARTITION Apple's MacOS partition table.
528 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
529 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
530 bootloader. Note 2TB partition limit; see
532 CONFIG_SCSI) you must configure support for at
533 least one non-MTD partition type as well.
535 - NETWORK Support (PCI):
537 Utility code for direct access to the SPI bus on Intel 8257x.
538 This does not do anything useful unless you set at least one
539 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
542 Support for National dp83815 chips.
545 Support for National dp8382[01] gigabit chips.
547 - NETWORK Support (other):
549 Support for the Calxeda XGMAC device
552 Support for SMSC's LAN91C96 chips.
554 CONFIG_LAN91C96_USE_32_BIT
555 Define this to enable 32 bit addressing
557 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
558 Define this if you have more then 3 PHYs.
561 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
563 CONFIG_FTGMAC100_EGIGA
564 Define this to use GE link update with gigabit PHY.
565 Define this if FTGMAC100 is connected to gigabit PHY.
566 If your system has 10/100 PHY only, it might not occur
567 wrong behavior. Because PHY usually return timeout or
568 useless data when polling gigabit status and gigabit
569 control registers. This behavior won't affect the
570 correctnessof 10/100 link speed update.
573 Support for Renesas on-chip Ethernet controller
575 CONFIG_SH_ETHER_USE_PORT
576 Define the number of ports to be used
578 CONFIG_SH_ETHER_PHY_ADDR
579 Define the ETH PHY's address
581 CONFIG_SH_ETHER_CACHE_WRITEBACK
582 If this option is set, the driver enables cache flush.
588 CONFIG_TPM_TIS_INFINEON
589 Support for Infineon i2c bus TPM devices. Only one device
590 per system is supported at this time.
592 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
593 Define the burst count bytes upper limit
596 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
598 CONFIG_TPM_ST33ZP24_I2C
599 Support for STMicroelectronics ST33ZP24 I2C devices.
600 Requires TPM_ST33ZP24 and I2C.
602 CONFIG_TPM_ST33ZP24_SPI
603 Support for STMicroelectronics ST33ZP24 SPI devices.
604 Requires TPM_ST33ZP24 and SPI.
607 Support for Atmel TWI TPM device. Requires I2C support.
610 Support for generic parallel port TPM devices. Only one device
611 per system is supported at this time.
613 CONFIG_TPM_TIS_BASE_ADDRESS
614 Base address where the generic TPM device is mapped
615 to. Contemporary x86 systems usually map it at
619 Define this to enable the TPM support library which provides
620 functional interfaces to some TPM commands.
621 Requires support for a TPM device.
623 CONFIG_TPM_AUTH_SESSIONS
624 Define this to enable authorized functions in the TPM library.
625 Requires CONFIG_TPM and CONFIG_SHA1.
628 At the moment only the UHCI host controller is
629 supported (PIP405, MIP405); define
630 CONFIG_USB_UHCI to enable it.
631 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
632 and define CONFIG_USB_STORAGE to enable the USB
635 Supported are USB Keyboards and USB Floppy drives
638 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
642 Define the below if you wish to use the USB console.
643 Once firmware is rebuilt from a serial console issue the
644 command "setenv stdin usbtty; setenv stdout usbtty" and
645 attach your USB cable. The Unix command "dmesg" should print
646 it has found a new device. The environment variable usbtty
647 can be set to gserial or cdc_acm to enable your device to
648 appear to a USB host as a Linux gserial device or a
649 Common Device Class Abstract Control Model serial device.
650 If you select usbtty = gserial you should be able to enumerate
652 # modprobe usbserial vendor=0xVendorID product=0xProductID
653 else if using cdc_acm, simply setting the environment
654 variable usbtty to be cdc_acm should suffice. The following
655 might be defined in YourBoardName.h
658 Define this to build a UDC device
661 Define this to have a tty type of device available to
662 talk to the UDC device
665 Define this to enable the high speed support for usb
666 device and usbtty. If this feature is enabled, a routine
667 int is_usbd_high_speed(void)
668 also needs to be defined by the driver to dynamically poll
669 whether the enumeration has succeded at high speed or full
672 If you have a USB-IF assigned VendorID then you may wish to
673 define your own vendor specific values either in BoardName.h
674 or directly in usbd_vendor_info.h. If you don't define
675 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
676 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
677 should pretend to be a Linux device to it's target host.
679 CONFIG_USBD_MANUFACTURER
680 Define this string as the name of your company for
681 - CONFIG_USBD_MANUFACTURER "my company"
683 CONFIG_USBD_PRODUCT_NAME
684 Define this string as the name of your product
685 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
688 Define this as your assigned Vendor ID from the USB
689 Implementors Forum. This *must* be a genuine Vendor ID
690 to avoid polluting the USB namespace.
691 - CONFIG_USBD_VENDORID 0xFFFF
693 CONFIG_USBD_PRODUCTID
694 Define this as the unique Product ID
696 - CONFIG_USBD_PRODUCTID 0xFFFF
698 - ULPI Layer Support:
699 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
700 the generic ULPI layer. The generic layer accesses the ULPI PHY
701 via the platform viewport, so you need both the genric layer and
702 the viewport enabled. Currently only Chipidea/ARC based
703 viewport is supported.
704 To enable the ULPI layer support, define CONFIG_USB_ULPI and
705 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
706 If your ULPI phy needs a different reference clock than the
707 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
708 the appropriate value in Hz.
712 Support for Renesas on-chip MMCIF controller
715 Define the base address of MMCIF registers
718 Define the clock frequency for MMCIF
720 - USB Device Firmware Update (DFU) class support:
722 This enables the USB portion of the DFU USB class
725 This enables support for exposing NAND devices via DFU.
728 This enables support for exposing RAM via DFU.
729 Note: DFU spec refer to non-volatile memory usage, but
730 allow usages beyond the scope of spec - here RAM usage,
731 one that would help mostly the developer.
733 CONFIG_SYS_DFU_DATA_BUF_SIZE
734 Dfu transfer uses a buffer before writing data to the
735 raw storage device. Make the size (in bytes) of this buffer
736 configurable. The size of this buffer is also configurable
737 through the "dfu_bufsiz" environment variable.
739 CONFIG_SYS_DFU_MAX_FILE_SIZE
740 When updating files rather than the raw storage device,
741 we use a static buffer to copy the file into and then write
742 the buffer once we've been given the whole file. Define
743 this to the maximum filesize (in bytes) for the buffer.
744 Default is 4 MiB if undefined.
746 DFU_DEFAULT_POLL_TIMEOUT
747 Poll timeout [ms], is the timeout a device can send to the
748 host. The host must wait for this timeout before sending
749 a subsequent DFU_GET_STATUS request to the device.
751 DFU_MANIFEST_POLL_TIMEOUT
752 Poll timeout [ms], which the device sends to the host when
753 entering dfuMANIFEST state. Host waits this timeout, before
754 sending again an USB request to the device.
757 See Kconfig help for available keyboard drivers.
760 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
762 The clock frequency of the MII bus
764 CONFIG_PHY_CMD_DELAY (ppc4xx)
766 Some PHY like Intel LXT971A need extra delay after
767 command issued before MII status register can be read
772 Define a default value for the IP address to use for
773 the default Ethernet interface, in case this is not
774 determined through e.g. bootp.
775 (Environment variable "ipaddr")
780 Defines a default value for the IP address of a TFTP
781 server to contact when using the "tftboot" command.
782 (Environment variable "serverip")
784 - Gateway IP address:
787 Defines a default value for the IP address of the
788 default router where packets to other networks are
790 (Environment variable "gatewayip")
795 Defines a default value for the subnet mask (or
796 routing prefix) which is used to determine if an IP
797 address belongs to the local subnet or needs to be
798 forwarded through a router.
799 (Environment variable "netmask")
801 - BOOTP Recovery Mode:
802 CONFIG_BOOTP_RANDOM_DELAY
804 If you have many targets in a network that try to
805 boot using BOOTP, you may want to avoid that all
806 systems send out BOOTP requests at precisely the same
807 moment (which would happen for instance at recovery
808 from a power failure, when all systems will try to
809 boot, thus flooding the BOOTP server. Defining
810 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
811 inserted before sending out BOOTP requests. The
812 following delays are inserted then:
814 1st BOOTP request: delay 0 ... 1 sec
815 2nd BOOTP request: delay 0 ... 2 sec
816 3rd BOOTP request: delay 0 ... 4 sec
818 BOOTP requests: delay 0 ... 8 sec
820 CONFIG_BOOTP_ID_CACHE_SIZE
822 BOOTP packets are uniquely identified using a 32-bit ID. The
823 server will copy the ID from client requests to responses and
824 U-Boot will use this to determine if it is the destination of
825 an incoming response. Some servers will check that addresses
826 aren't in use before handing them out (usually using an ARP
827 ping) and therefore take up to a few hundred milliseconds to
828 respond. Network congestion may also influence the time it
829 takes for a response to make it back to the client. If that
830 time is too long, U-Boot will retransmit requests. In order
831 to allow earlier responses to still be accepted after these
832 retransmissions, U-Boot's BOOTP client keeps a small cache of
833 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
834 cache. The default is to keep IDs for up to four outstanding
835 requests. Increasing this will allow U-Boot to accept offers
836 from a BOOTP client in networks with unusually high latency.
838 - DHCP Advanced Options:
840 - Link-local IP address negotiation:
841 Negotiate with other link-local clients on the local network
842 for an address that doesn't require explicit configuration.
843 This is especially useful if a DHCP server cannot be guaranteed
844 to exist in all environments that the device must operate.
846 See doc/README.link-local for more information.
848 - MAC address from environment variables
850 FDT_SEQ_MACADDR_FROM_ENV
852 Fix-up device tree with MAC addresses fetched sequentially from
853 environment variables. This config work on assumption that
854 non-usable ethernet node of device-tree are either not present
855 or their status has been marked as "disabled".
860 The device id used in CDP trigger frames.
862 CONFIG_CDP_DEVICE_ID_PREFIX
864 A two character string which is prefixed to the MAC address
869 A printf format string which contains the ascii name of
870 the port. Normally is set to "eth%d" which sets
871 eth0 for the first Ethernet, eth1 for the second etc.
873 CONFIG_CDP_CAPABILITIES
875 A 32bit integer which indicates the device capabilities;
876 0x00000010 for a normal host which does not forwards.
880 An ascii string containing the version of the software.
884 An ascii string containing the name of the platform.
888 A 32bit integer sent on the trigger.
890 CONFIG_CDP_POWER_CONSUMPTION
892 A 16bit integer containing the power consumption of the
893 device in .1 of milliwatts.
895 CONFIG_CDP_APPLIANCE_VLAN_TYPE
897 A byte containing the id of the VLAN.
899 - Status LED: CONFIG_LED_STATUS
901 Several configurations allow to display the current
902 status using a LED. For instance, the LED will blink
903 fast while running U-Boot code, stop blinking as
904 soon as a reply to a BOOTP request was received, and
905 start blinking slow once the Linux kernel is running
906 (supported by a status LED driver in the Linux
907 kernel). Defining CONFIG_LED_STATUS enables this
912 CONFIG_LED_STATUS_GPIO
913 The status LED can be connected to a GPIO pin.
914 In such cases, the gpio_led driver can be used as a
915 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
916 to include the gpio_led driver in the U-Boot binary.
918 CONFIG_GPIO_LED_INVERTED_TABLE
919 Some GPIO connected LEDs may have inverted polarity in which
920 case the GPIO high value corresponds to LED off state and
921 GPIO low value corresponds to LED on state.
922 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
923 with a list of GPIO LEDs that have inverted polarity.
926 CONFIG_SYS_NUM_I2C_BUSES
927 Hold the number of i2c buses you want to use.
929 CONFIG_SYS_I2C_DIRECT_BUS
930 define this, if you don't use i2c muxes on your hardware.
931 if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
934 CONFIG_SYS_I2C_MAX_HOPS
935 define how many muxes are maximal consecutively connected
936 on one i2c bus. If you not use i2c muxes, omit this
940 hold a list of buses you want to use, only used if
941 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
942 a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
943 CONFIG_SYS_NUM_I2C_BUSES = 9:
945 CONFIG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
946 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
947 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
948 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
949 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
950 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
951 {1, {I2C_NULL_HOP}}, \
952 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
953 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
957 bus 0 on adapter 0 without a mux
958 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
959 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
960 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
961 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
962 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
963 bus 6 on adapter 1 without a mux
964 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
965 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
967 If you do not have i2c muxes on your board, omit this define.
969 - Legacy I2C Support:
970 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
971 then the following macros need to be defined (examples are
972 from include/configs/lwmon.h):
976 (Optional). Any commands necessary to enable the I2C
977 controller or configure ports.
979 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
983 The code necessary to make the I2C data line active
984 (driven). If the data line is open collector, this
987 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
991 The code necessary to make the I2C data line tri-stated
992 (inactive). If the data line is open collector, this
995 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
999 Code that returns true if the I2C data line is high,
1002 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1006 If <bit> is true, sets the I2C data line high. If it
1007 is false, it clears it (low).
1009 eg: #define I2C_SDA(bit) \
1010 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
1011 else immr->im_cpm.cp_pbdat &= ~PB_SDA
1015 If <bit> is true, sets the I2C clock line high. If it
1016 is false, it clears it (low).
1018 eg: #define I2C_SCL(bit) \
1019 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
1020 else immr->im_cpm.cp_pbdat &= ~PB_SCL
1024 This delay is invoked four times per clock cycle so this
1025 controls the rate of data transfer. The data rate thus
1026 is 1 / (I2C_DELAY * 4). Often defined to be something
1029 #define I2C_DELAY udelay(2)
1031 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1033 If your arch supports the generic GPIO framework (asm/gpio.h),
1034 then you may alternatively define the two GPIOs that are to be
1035 used as SCL / SDA. Any of the previous I2C_xxx macros will
1036 have GPIO-based defaults assigned to them as appropriate.
1038 You should define these to the GPIO value as given directly to
1039 the generic GPIO functions.
1041 CONFIG_I2C_MULTI_BUS
1043 This option allows the use of multiple I2C buses, each of which
1044 must have a controller. At any point in time, only one bus is
1045 active. To switch to a different bus, use the 'i2c dev' command.
1046 Note that bus numbering is zero-based.
1048 CONFIG_SYS_I2C_NOPROBES
1050 This option specifies a list of I2C devices that will be skipped
1051 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
1052 is set, specify a list of bus-device pairs. Otherwise, specify
1053 a 1D array of device addresses
1056 #undef CONFIG_I2C_MULTI_BUS
1057 #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1059 will skip addresses 0x50 and 0x68 on a board with one I2C bus
1061 #define CONFIG_I2C_MULTI_BUS
1062 #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1064 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1066 CONFIG_SYS_RTC_BUS_NUM
1068 If defined, then this indicates the I2C bus number for the RTC.
1069 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1071 CONFIG_SOFT_I2C_READ_REPEATED_START
1073 defining this will force the i2c_read() function in
1074 the soft_i2c driver to perform an I2C repeated start
1075 between writing the address pointer and reading the
1076 data. If this define is omitted the default behaviour
1077 of doing a stop-start sequence will be used. Most I2C
1078 devices can use either method, but some require one or
1081 - SPI Support: CONFIG_SPI
1083 Enables SPI driver (so far only tested with
1084 SPI EEPROM, also an instance works with Crystal A/D and
1085 D/As on the SACSng board)
1087 CONFIG_SYS_SPI_MXC_WAIT
1088 Timeout for waiting until spi transfer completed.
1089 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1091 - FPGA Support: CONFIG_FPGA
1093 Enables FPGA subsystem.
1095 CONFIG_FPGA_<vendor>
1097 Enables support for specific chip vendors.
1100 CONFIG_FPGA_<family>
1102 Enables support for FPGA family.
1103 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1105 CONFIG_SYS_FPGA_CHECK_BUSY
1107 Enable checks on FPGA configuration interface busy
1108 status by the configuration function. This option
1109 will require a board or device specific function to
1114 If defined, a function that provides delays in the FPGA
1115 configuration driver.
1117 CONFIG_SYS_FPGA_CHECK_ERROR
1119 Check for configuration errors during FPGA bitfile
1120 loading. For example, abort during Virtex II
1121 configuration if the INIT_B line goes low (which
1122 indicated a CRC error).
1124 CONFIG_SYS_FPGA_WAIT_INIT
1126 Maximum time to wait for the INIT_B line to de-assert
1127 after PROB_B has been de-asserted during a Virtex II
1128 FPGA configuration sequence. The default time is 500
1131 CONFIG_SYS_FPGA_WAIT_BUSY
1133 Maximum time to wait for BUSY to de-assert during
1134 Virtex II FPGA configuration. The default is 5 ms.
1136 CONFIG_SYS_FPGA_WAIT_CONFIG
1138 Time to wait after FPGA configuration. The default is
1141 - Vendor Parameter Protection:
1143 U-Boot considers the values of the environment
1144 variables "serial#" (Board Serial Number) and
1145 "ethaddr" (Ethernet Address) to be parameters that
1146 are set once by the board vendor / manufacturer, and
1147 protects these variables from casual modification by
1148 the user. Once set, these variables are read-only,
1149 and write or delete attempts are rejected. You can
1150 change this behaviour:
1152 If CONFIG_ENV_OVERWRITE is #defined in your config
1153 file, the write protection for vendor parameters is
1154 completely disabled. Anybody can change or delete
1157 Alternatively, if you define _both_ an ethaddr in the
1158 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1159 Ethernet address is installed in the environment,
1160 which can be changed exactly ONCE by the user. [The
1161 serial# is unaffected by this, i. e. it remains
1164 The same can be accomplished in a more flexible way
1165 for any variable by configuring the type of access
1166 to allow for those variables in the ".flags" variable
1167 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1172 Define this variable to enable the reservation of
1173 "protected RAM", i. e. RAM which is not overwritten
1174 by U-Boot. Define CONFIG_PRAM to hold the number of
1175 kB you want to reserve for pRAM. You can overwrite
1176 this default value by defining an environment
1177 variable "pram" to the number of kB you want to
1178 reserve. Note that the board info structure will
1179 still show the full amount of RAM. If pRAM is
1180 reserved, a new environment variable "mem" will
1181 automatically be defined to hold the amount of
1182 remaining RAM in a form that can be passed as boot
1183 argument to Linux, for instance like that:
1185 setenv bootargs ... mem=\${mem}
1188 This way you can tell Linux not to use this memory,
1189 either, which results in a memory region that will
1190 not be affected by reboots.
1192 *WARNING* If your board configuration uses automatic
1193 detection of the RAM size, you must make sure that
1194 this memory test is non-destructive. So far, the
1195 following board configurations are known to be
1198 IVMS8, IVML24, SPD8xx,
1199 HERMES, IP860, RPXlite, LWMON,
1205 In the current implementation, the local variables
1206 space and global environment variables space are
1207 separated. Local variables are those you define by
1208 simply typing `name=value'. To access a local
1209 variable later on, you have write `$name' or
1210 `${name}'; to execute the contents of a variable
1211 directly type `$name' at the command prompt.
1213 Global environment variables are those you use
1214 setenv/printenv to work with. To run a command stored
1215 in such a variable, you need to use the run command,
1216 and you must not use the '$' sign to access them.
1218 To store commands and special characters in a
1219 variable, please use double quotation marks
1220 surrounding the whole text of the variable, instead
1221 of the backslashes before semicolons and special
1224 - Default Environment:
1225 CONFIG_EXTRA_ENV_SETTINGS
1227 Define this to contain any number of null terminated
1228 strings (variable = value pairs) that will be part of
1229 the default environment compiled into the boot image.
1231 For example, place something like this in your
1232 board's config file:
1234 #define CONFIG_EXTRA_ENV_SETTINGS \
1238 Warning: This method is based on knowledge about the
1239 internal format how the environment is stored by the
1240 U-Boot code. This is NOT an official, exported
1241 interface! Although it is unlikely that this format
1242 will change soon, there is no guarantee either.
1243 You better know what you are doing here.
1245 Note: overly (ab)use of the default environment is
1246 discouraged. Make sure to check other ways to preset
1247 the environment like the "source" command or the
1250 CONFIG_DELAY_ENVIRONMENT
1252 Normally the environment is loaded when the board is
1253 initialised so that it is available to U-Boot. This inhibits
1254 that so that the environment is not available until
1255 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1256 this is instead controlled by the value of
1257 /config/load-environment.
1259 CONFIG_STANDALONE_LOAD_ADDR
1261 This option defines a board specific value for the
1262 address where standalone program gets loaded, thus
1263 overwriting the architecture dependent default
1266 - Automatic software updates via TFTP server
1268 CONFIG_UPDATE_TFTP_CNT_MAX
1269 CONFIG_UPDATE_TFTP_MSEC_MAX
1271 These options enable and control the auto-update feature;
1272 for a more detailed description refer to doc/README.update.
1274 - MTD Support (mtdparts command, UBI support)
1275 CONFIG_MTD_UBI_WL_THRESHOLD
1276 This parameter defines the maximum difference between the highest
1277 erase counter value and the lowest erase counter value of eraseblocks
1278 of UBI devices. When this threshold is exceeded, UBI starts performing
1279 wear leveling by means of moving data from eraseblock with low erase
1280 counter to eraseblocks with high erase counter.
1282 The default value should be OK for SLC NAND flashes, NOR flashes and
1283 other flashes which have eraseblock life-cycle 100000 or more.
1284 However, in case of MLC NAND flashes which typically have eraseblock
1285 life-cycle less than 10000, the threshold should be lessened (e.g.,
1286 to 128 or 256, although it does not have to be power of 2).
1290 CONFIG_MTD_UBI_BEB_LIMIT
1291 This option specifies the maximum bad physical eraseblocks UBI
1292 expects on the MTD device (per 1024 eraseblocks). If the
1293 underlying flash does not admit of bad eraseblocks (e.g. NOR
1294 flash), this value is ignored.
1296 NAND datasheets often specify the minimum and maximum NVM
1297 (Number of Valid Blocks) for the flashes' endurance lifetime.
1298 The maximum expected bad eraseblocks per 1024 eraseblocks
1299 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1300 which gives 20 for most NANDs (MaxNVB is basically the total
1301 count of eraseblocks on the chip).
1303 To put it differently, if this value is 20, UBI will try to
1304 reserve about 1.9% of physical eraseblocks for bad blocks
1305 handling. And that will be 1.9% of eraseblocks on the entire
1306 NAND chip, not just the MTD partition UBI attaches. This means
1307 that if you have, say, a NAND flash chip admits maximum 40 bad
1308 eraseblocks, and it is split on two MTD partitions of the same
1309 size, UBI will reserve 40 eraseblocks when attaching a
1314 CONFIG_MTD_UBI_FASTMAP
1315 Fastmap is a mechanism which allows attaching an UBI device
1316 in nearly constant time. Instead of scanning the whole MTD device it
1317 only has to locate a checkpoint (called fastmap) on the device.
1318 The on-flash fastmap contains all information needed to attach
1319 the device. Using fastmap makes only sense on large devices where
1320 attaching by scanning takes long. UBI will not automatically install
1321 a fastmap on old images, but you can set the UBI parameter
1322 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1323 that fastmap-enabled images are still usable with UBI implementations
1324 without fastmap support. On typical flash devices the whole fastmap
1325 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1327 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1328 Set this parameter to enable fastmap automatically on images
1332 CONFIG_MTD_UBI_FM_DEBUG
1333 Enable UBI fastmap debug
1338 Enable building of SPL globally.
1340 CONFIG_SPL_PANIC_ON_RAW_IMAGE
1341 When defined, SPL will panic() if the image it has
1342 loaded does not have a signature.
1343 Defining this is useful when code which loads images
1344 in SPL cannot guarantee that absolutely all read errors
1346 An example is the LPC32XX MLC NAND driver, which will
1347 consider that a completely unreadable NAND block is bad,
1348 and thus should be skipped silently.
1350 CONFIG_SPL_DISPLAY_PRINT
1351 For ARM, enable an optional function to print more information
1352 about the running system.
1354 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
1355 Set this for NAND SPL on PPC mpc83xx targets, so that
1356 start.S waits for the rest of the SPL to load before
1357 continuing (the hardware starts execution after just
1358 loading the first page rather than the full 4K).
1361 Support for a lightweight UBI (fastmap) scanner and
1364 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
1365 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
1366 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
1367 CFG_SYS_NAND_ECCPOS, CFG_SYS_NAND_ECCSIZE,
1368 CFG_SYS_NAND_ECCBYTES
1369 Defines the size and behavior of the NAND that SPL uses
1372 CFG_SYS_NAND_U_BOOT_DST
1373 Location in memory to load U-Boot to
1375 CFG_SYS_NAND_U_BOOT_SIZE
1376 Size of image to load
1378 CFG_SYS_NAND_U_BOOT_START
1379 Entry point in loaded image to jump to
1381 CONFIG_SPL_RAM_DEVICE
1382 Support for running image already present in ram, in SPL binary
1384 CONFIG_SPL_FIT_PRINT
1385 Printing information about a FIT image adds quite a bit of
1386 code to SPL. So this is normally disabled in SPL. Use this
1387 option to re-enable it. This will affect the output of the
1388 bootm command when booting a FIT image.
1390 - Interrupt support (PPC):
1392 There are common interrupt_init() and timer_interrupt()
1393 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
1394 for CPU specific initialization. interrupt_init_cpu()
1395 should set decrementer_count to appropriate value. If
1396 CPU resets decrementer automatically after interrupt
1397 (ppc4xx) it should set decrementer_count to zero.
1398 timer_interrupt() calls timer_interrupt_cpu() for CPU
1399 specific handling. If board has watchdog / status_led
1400 / other_activity_monitor it works automatically from
1401 general timer_interrupt().
1404 Board initialization settings:
1405 ------------------------------
1407 During Initialization u-boot calls a number of board specific functions
1408 to allow the preparation of board specific prerequisites, e.g. pin setup
1409 before drivers are initialized. To enable these callbacks the
1410 following configuration macros have to be defined. Currently this is
1411 architecture specific, so please check arch/your_architecture/lib/board.c
1412 typically in board_init_f() and board_init_r().
1414 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
1415 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
1416 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
1418 Configuration Settings:
1419 -----------------------
1421 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
1422 Optionally it can be defined to support 64-bit memory commands.
1424 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
1425 undefine this when you're short of memory.
1427 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
1428 width of the commands listed in the 'help' command output.
1430 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
1431 prompt for user input.
1433 - CONFIG_SYS_BAUDRATE_TABLE:
1434 List of legal baudrate settings for this board.
1436 - CONFIG_SYS_MEM_RESERVE_SECURE
1437 Only implemented for ARMv8 for now.
1438 If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
1439 is substracted from total RAM and won't be reported to OS.
1440 This memory can be used as secure memory. A variable
1441 gd->arch.secure_ram is used to track the location. In systems
1442 the RAM base is not zero, or RAM is divided into banks,
1443 this variable needs to be recalcuated to get the address.
1445 - CONFIG_SYS_SDRAM_BASE:
1446 Physical start address of SDRAM. _Must_ be 0 here.
1448 - CONFIG_SYS_FLASH_BASE:
1449 Physical start address of Flash memory.
1451 - CONFIG_SYS_MALLOC_LEN:
1452 Size of DRAM reserved for malloc() use.
1454 - CONFIG_SYS_MALLOC_F_LEN
1455 Size of the malloc() pool for use before relocation. If
1456 this is defined, then a very simple malloc() implementation
1457 will become available before relocation. The address is just
1458 below the global data, and the stack is moved down to make
1461 This feature allocates regions with increasing addresses
1462 within the region. calloc() is supported, but realloc()
1463 is not available. free() is supported but does nothing.
1464 The memory will be freed (or in fact just forgotten) when
1465 U-Boot relocates itself.
1467 - CONFIG_SYS_MALLOC_SIMPLE
1468 Provides a simple and small malloc() and calloc() for those
1469 boards which do not use the full malloc in SPL (which is
1470 enabled with CONFIG_SYS_SPL_MALLOC).
1472 - CONFIG_SYS_BOOTMAPSZ:
1473 Maximum size of memory mapped by the startup code of
1474 the Linux kernel; all data that must be processed by
1475 the Linux kernel (bd_info, boot arguments, FDT blob if
1476 used) must be put below this limit, unless "bootm_low"
1477 environment variable is defined and non-zero. In such case
1478 all data for the Linux kernel must be between "bootm_low"
1479 and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
1480 variable "bootm_mapsize" will override the value of
1481 CONFIG_SYS_BOOTMAPSZ. If CONFIG_SYS_BOOTMAPSZ is undefined,
1482 then the value in "bootm_size" will be used instead.
1484 - CONFIG_SYS_BOOT_GET_CMDLINE:
1485 Enables allocating and saving kernel cmdline in space between
1486 "bootm_low" and "bootm_low" + BOOTMAPSZ.
1488 - CONFIG_SYS_BOOT_GET_KBD:
1489 Enables allocating and saving a kernel copy of the bd_info in
1490 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
1492 - CONFIG_SYS_FLASH_PROTECTION
1493 If defined, hardware flash sectors protection is used
1494 instead of U-Boot software protection.
1496 - CONFIG_SYS_FLASH_CFI:
1497 Define if the flash driver uses extra elements in the
1498 common flash structure for storing flash geometry.
1500 - CONFIG_FLASH_CFI_DRIVER
1501 This option also enables the building of the cfi_flash driver
1502 in the drivers directory
1504 - CONFIG_FLASH_CFI_MTD
1505 This option enables the building of the cfi_mtd driver
1506 in the drivers directory. The driver exports CFI flash
1509 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
1510 Use buffered writes to flash.
1512 - CONFIG_FLASH_SPANSION_S29WS_N
1513 s29ws-n MirrorBit flash has non-standard addresses for buffered
1516 - CONFIG_FLASH_SHOW_PROGRESS
1517 If defined (must be an integer), print out countdown
1518 digits and dots. Recommended value: 45 (9..1) for 80
1519 column displays, 15 (3..1) for 40 column displays.
1521 - CONFIG_FLASH_VERIFY
1522 If defined, the content of the flash (destination) is compared
1523 against the source after the write operation. An error message
1524 will be printed when the contents are not identical.
1525 Please note that this option is useless in nearly all cases,
1526 since such flash programming errors usually are detected earlier
1527 while unprotecting/erasing/programming. Please only enable
1528 this option if you really know what you are doing.
1530 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1531 - CONFIG_ENV_FLAGS_LIST_STATIC
1532 Enable validation of the values given to environment variables when
1533 calling env set. Variables can be restricted to only decimal,
1534 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
1535 the variables can also be restricted to IP address or MAC address.
1537 The format of the list is:
1538 type_attribute = [s|d|x|b|i|m]
1539 access_attribute = [a|r|o|c]
1540 attributes = type_attribute[access_attribute]
1541 entry = variable_name[:attributes]
1544 The type attributes are:
1545 s - String (default)
1548 b - Boolean ([1yYtT|0nNfF])
1552 The access attributes are:
1558 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1559 Define this to a list (string) to define the ".flags"
1560 environment variable in the default or embedded environment.
1562 - CONFIG_ENV_FLAGS_LIST_STATIC
1563 Define this to a list (string) to define validation that
1564 should be done if an entry is not found in the ".flags"
1565 environment variable. To override a setting in the static
1566 list, simply add an entry for the same variable name to the
1569 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
1570 regular expression. This allows multiple variables to define the same
1571 flags without explicitly listing them for each variable.
1573 The following definitions that deal with the placement and management
1574 of environment data (variable area); in general, we support the
1575 following configurations:
1577 - CONFIG_BUILD_ENVCRC:
1579 Builds up envcrc with the target environment so that external utils
1580 may easily extract it and embed it in final U-Boot images.
1582 BE CAREFUL! The first access to the environment happens quite early
1583 in U-Boot initialization (when we try to get the setting of for the
1584 console baudrate). You *MUST* have mapped your NVRAM area then, or
1587 Please note that even with NVRAM we still use a copy of the
1588 environment in RAM: we could work on NVRAM directly, but we want to
1589 keep settings there always unmodified except somebody uses "saveenv"
1590 to save the current settings.
1592 BE CAREFUL! For some special cases, the local device can not use
1593 "saveenv" command. For example, the local device will get the
1594 environment stored in a remote NOR flash by SRIO or PCIE link,
1595 but it can not erase, write this NOR flash by SRIO or PCIE interface.
1597 - CONFIG_NAND_ENV_DST
1599 Defines address in RAM to which the nand_spl code should copy the
1600 environment. If redundant environment is used, it will be copied to
1601 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
1603 Please note that the environment is read-only until the monitor
1604 has been relocated to RAM and a RAM copy of the environment has been
1605 created; also, when using EEPROM you will have to use env_get_f()
1606 until then to read environment variables.
1608 The environment is protected by a CRC32 checksum. Before the monitor
1609 is relocated into RAM, as a result of a bad CRC you will be working
1610 with the compiled-in default environment - *silently*!!! [This is
1611 necessary, because the first environment variable we need is the
1612 "baudrate" setting for the console - if we have a bad CRC, we don't
1613 have any device yet where we could complain.]
1615 Note: once the monitor has been relocated, then it will complain if
1616 the default environment is used; a new CRC is computed as soon as you
1617 use the "saveenv" command to store a valid environment.
1619 - CONFIG_SYS_FAULT_MII_ADDR:
1620 MII address of the PHY to check for the Ethernet link state.
1622 - CONFIG_NS16550_MIN_FUNCTIONS:
1623 Define this if you desire to only have use of the NS16550_init
1624 and NS16550_putc functions for the serial driver located at
1625 drivers/serial/ns16550.c. This option is useful for saving
1626 space for already greatly restricted images, including but not
1627 limited to NAND_SPL configurations.
1629 - CONFIG_DISPLAY_BOARDINFO
1630 Display information about the board that U-Boot is running on
1631 when U-Boot starts up. The board function checkboard() is called
1634 - CONFIG_DISPLAY_BOARDINFO_LATE
1635 Similar to the previous option, but display this information
1636 later, once stdio is running and output goes to the LCD, if
1639 Low Level (hardware related) configuration options:
1640 ---------------------------------------------------
1642 - CONFIG_SYS_CACHELINE_SIZE:
1643 Cache Line Size of the CPU.
1645 - CONFIG_SYS_CCSRBAR_DEFAULT:
1646 Default (power-on reset) physical address of CCSR on Freescale
1649 - CONFIG_SYS_CCSRBAR:
1650 Virtual address of CCSR. On a 32-bit build, this is typically
1651 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
1653 - CONFIG_SYS_CCSRBAR_PHYS:
1654 Physical address of CCSR. CCSR can be relocated to a new
1655 physical address, if desired. In this case, this macro should
1656 be set to that address. Otherwise, it should be set to the
1657 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
1658 is typically relocated on 36-bit builds. It is recommended
1659 that this macro be defined via the _HIGH and _LOW macros:
1661 #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
1662 * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
1664 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
1665 Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
1666 either 0 (32-bit build) or 0xF (36-bit build). This macro is
1667 used in assembly code, so it must not contain typecasts or
1668 integer size suffixes (e.g. "ULL").
1670 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
1671 Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
1672 used in assembly code, so it must not contain typecasts or
1673 integer size suffixes (e.g. "ULL").
1675 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
1676 DO NOT CHANGE unless you know exactly what you're
1677 doing! (11-4) [MPC8xx systems only]
1679 - CONFIG_SYS_INIT_RAM_ADDR:
1681 Start address of memory area that can be used for
1682 initial data and stack; please note that this must be
1683 writable memory that is working WITHOUT special
1684 initialization, i. e. you CANNOT use normal RAM which
1685 will become available only after programming the
1686 memory controller and running certain initialization
1689 U-Boot uses the following memory types:
1690 - MPC8xx: IMMR (internal memory of the CPU)
1692 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
1694 - CONFIG_SYS_OR_TIMING_SDRAM:
1698 Chip has SRIO or not
1701 Board has SRIO 1 port available
1704 Board has SRIO 2 port available
1706 - CONFIG_SRIO_PCIE_BOOT_MASTER
1707 Board can support master function for Boot from SRIO and PCIE
1709 - CONFIG_SYS_SRIOn_MEM_VIRT:
1710 Virtual Address of SRIO port 'n' memory region
1712 - CONFIG_SYS_SRIOn_MEM_PHYxS:
1713 Physical Address of SRIO port 'n' memory region
1715 - CONFIG_SYS_SRIOn_MEM_SIZE:
1716 Size of SRIO port 'n' memory region
1718 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
1719 Defined to tell the NAND controller that the NAND chip is using
1721 Not all NAND drivers use this symbol.
1722 Example of drivers that use it:
1723 - drivers/mtd/nand/raw/ndfc.c
1724 - drivers/mtd/nand/raw/mxc_nand.c
1726 - CONFIG_SYS_NDFC_EBC0_CFG
1727 Sets the EBC0_CFG register for the NDFC. If not defined
1728 a default value will be used.
1731 Get DDR timing information from an I2C EEPROM. Common
1732 with pluggable memory modules such as SODIMMs
1735 I2C address of the SPD EEPROM
1737 - CONFIG_SYS_SPD_BUS_NUM
1738 If SPD EEPROM is on an I2C bus other than the first
1739 one, specify here. Note that the value must resolve
1740 to something your driver can deal with.
1742 - CONFIG_FSL_DDR_INTERACTIVE
1743 Enable interactive DDR debugging. See doc/README.fsl-ddr.
1745 - CONFIG_FSL_DDR_SYNC_REFRESH
1746 Enable sync of refresh for multiple controllers.
1748 - CONFIG_FSL_DDR_BIST
1749 Enable built-in memory test for Freescale DDR controllers.
1752 Enable RMII mode for all FECs.
1753 Note that this is a global option, we can't
1754 have one FEC in standard MII mode and another in RMII mode.
1756 - CONFIG_CRC32_VERIFY
1757 Add a verify option to the crc32 command.
1760 => crc32 -v <address> <count> <crc32>
1762 Where address/count indicate a memory area
1763 and crc32 is the correct crc32 which the
1767 Add the "loopw" memory command. This only takes effect if
1768 the memory commands are activated globally (CONFIG_CMD_MEMORY).
1770 - CONFIG_CMD_MX_CYCLIC
1771 Add the "mdc" and "mwc" memory commands. These are cyclic
1776 This command will print 4 bytes (10,11,12,13) each 500 ms.
1778 => mwc.l 100 12345678 10
1779 This command will write 12345678 to address 100 all 10 ms.
1781 This only takes effect if the memory commands are activated
1782 globally (CONFIG_CMD_MEMORY).
1785 Set when the currently-running compilation is for an artifact
1786 that will end up in the SPL (as opposed to the TPL or U-Boot
1787 proper). Code that needs stage-specific behavior should check
1791 Set when the currently-running compilation is for an artifact
1792 that will end up in the TPL (as opposed to the SPL or U-Boot
1793 proper). Code that needs stage-specific behavior should check
1796 - CONFIG_ARCH_MAP_SYSMEM
1797 Generally U-Boot (and in particular the md command) uses
1798 effective address. It is therefore not necessary to regard
1799 U-Boot address as virtual addresses that need to be translated
1800 to physical addresses. However, sandbox requires this, since
1801 it maintains its own little RAM buffer which contains all
1802 addressable memory. This option causes some memory accesses
1803 to be mapped through map_sysmem() / unmap_sysmem().
1805 - CONFIG_X86_RESET_VECTOR
1806 If defined, the x86 reset vector code is included. This is not
1807 needed when U-Boot is running from Coreboot.
1809 Freescale QE/FMAN Firmware Support:
1810 -----------------------------------
1812 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
1813 loading of "firmware", which is encoded in the QE firmware binary format.
1814 This firmware often needs to be loaded during U-Boot booting, so macros
1815 are used to identify the storage device (NOR flash, SPI, etc) and the address
1818 - CONFIG_SYS_FMAN_FW_ADDR
1819 The address in the storage device where the FMAN microcode is located. The
1820 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1823 - CONFIG_SYS_QE_FW_ADDR
1824 The address in the storage device where the QE microcode is located. The
1825 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1828 - CONFIG_SYS_QE_FMAN_FW_LENGTH
1829 The maximum possible size of the firmware. The firmware binary format
1830 has a field that specifies the actual size of the firmware, but it
1831 might not be possible to read any part of the firmware unless some
1832 local storage is allocated to hold the entire firmware first.
1834 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
1835 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
1836 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
1837 virtual address in NOR flash.
1839 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
1840 Specifies that QE/FMAN firmware is located in NAND flash.
1841 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
1843 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
1844 Specifies that QE/FMAN firmware is located on the primary SD/MMC
1845 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
1847 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
1848 Specifies that QE/FMAN firmware is located in the remote (master)
1849 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
1850 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
1851 window->master inbound window->master LAW->the ucode address in
1852 master's memory space.
1854 Freescale Layerscape Management Complex Firmware Support:
1855 ---------------------------------------------------------
1856 The Freescale Layerscape Management Complex (MC) supports the loading of
1858 This firmware often needs to be loaded during U-Boot booting, so macros
1859 are used to identify the storage device (NOR flash, SPI, etc) and the address
1862 - CONFIG_FSL_MC_ENET
1863 Enable the MC driver for Layerscape SoCs.
1865 Freescale Layerscape Debug Server Support:
1866 -------------------------------------------
1867 The Freescale Layerscape Debug Server Support supports the loading of
1868 "Debug Server firmware" and triggering SP boot-rom.
1869 This firmware often needs to be loaded during U-Boot booting.
1871 - CONFIG_SYS_MC_RSV_MEM_ALIGN
1872 Define alignment of reserved memory MC requires
1877 In order to achieve reproducible builds, timestamps used in the U-Boot build
1878 process have to be set to a fixed value.
1880 This is done using the SOURCE_DATE_EPOCH environment variable.
1881 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
1882 option for U-Boot or an environment variable in U-Boot.
1884 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
1886 Building the Software:
1887 ======================
1889 Building U-Boot has been tested in several native build environments
1890 and in many different cross environments. Of course we cannot support
1891 all possibly existing versions of cross development tools in all
1892 (potentially obsolete) versions. In case of tool chain problems we
1893 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
1894 which is extensively used to build and test U-Boot.
1896 If you are not using a native environment, it is assumed that you
1897 have GNU cross compiling tools available in your path. In this case,
1898 you must set the environment variable CROSS_COMPILE in your shell.
1899 Note that no changes to the Makefile or any other source files are
1900 necessary. For example using the ELDK on a 4xx CPU, please enter:
1902 $ CROSS_COMPILE=ppc_4xx-
1903 $ export CROSS_COMPILE
1905 U-Boot is intended to be simple to build. After installing the
1906 sources you must configure U-Boot for one specific board type. This
1911 where "NAME_defconfig" is the name of one of the existing configu-
1912 rations; see configs/*_defconfig for supported names.
1914 Note: for some boards special configuration names may exist; check if
1915 additional information is available from the board vendor; for
1916 instance, the TQM823L systems are available without (standard)
1917 or with LCD support. You can select such additional "features"
1918 when choosing the configuration, i. e.
1920 make TQM823L_defconfig
1921 - will configure for a plain TQM823L, i. e. no LCD support
1923 make TQM823L_LCD_defconfig
1924 - will configure for a TQM823L with U-Boot console on LCD
1929 Finally, type "make all", and you should get some working U-Boot
1930 images ready for download to / installation on your system:
1932 - "u-boot.bin" is a raw binary image
1933 - "u-boot" is an image in ELF binary format
1934 - "u-boot.srec" is in Motorola S-Record format
1936 By default the build is performed locally and the objects are saved
1937 in the source directory. One of the two methods can be used to change
1938 this behavior and build U-Boot to some external directory:
1940 1. Add O= to the make command line invocations:
1942 make O=/tmp/build distclean
1943 make O=/tmp/build NAME_defconfig
1944 make O=/tmp/build all
1946 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
1948 export KBUILD_OUTPUT=/tmp/build
1953 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
1956 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
1957 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
1958 For example to treat all compiler warnings as errors:
1960 make KCFLAGS=-Werror
1962 Please be aware that the Makefiles assume you are using GNU make, so
1963 for instance on NetBSD you might need to use "gmake" instead of
1967 If the system board that you have is not listed, then you will need
1968 to port U-Boot to your hardware platform. To do this, follow these
1971 1. Create a new directory to hold your board specific code. Add any
1972 files you need. In your board directory, you will need at least
1973 the "Makefile" and a "<board>.c".
1974 2. Create a new configuration file "include/configs/<board>.h" for
1976 3. If you're porting U-Boot to a new CPU, then also create a new
1977 directory to hold your CPU specific code. Add any files you need.
1978 4. Run "make <board>_defconfig" with your new name.
1979 5. Type "make", and you should get a working "u-boot.srec" file
1980 to be installed on your target system.
1981 6. Debug and solve any problems that might arise.
1982 [Of course, this last step is much harder than it sounds.]
1985 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
1986 ==============================================================
1988 If you have modified U-Boot sources (for instance added a new board
1989 or support for new devices, a new CPU, etc.) you are expected to
1990 provide feedback to the other developers. The feedback normally takes
1991 the form of a "patch", i.e. a context diff against a certain (latest
1992 official or latest in the git repository) version of U-Boot sources.
1994 But before you submit such a patch, please verify that your modifi-
1995 cation did not break existing code. At least make sure that *ALL* of
1996 the supported boards compile WITHOUT ANY compiler warnings. To do so,
1997 just run the buildman script (tools/buildman/buildman), which will
1998 configure and build U-Boot for ALL supported system. Be warned, this
1999 will take a while. Please see the buildman README, or run 'buildman -H'
2003 See also "U-Boot Porting Guide" below.
2006 Monitor Commands - Overview:
2007 ============================
2009 go - start application at address 'addr'
2010 run - run commands in an environment variable
2011 bootm - boot application image from memory
2012 bootp - boot image via network using BootP/TFTP protocol
2013 bootz - boot zImage from memory
2014 tftpboot- boot image via network using TFTP protocol
2015 and env variables "ipaddr" and "serverip"
2016 (and eventually "gatewayip")
2017 tftpput - upload a file via network using TFTP protocol
2018 rarpboot- boot image via network using RARP/TFTP protocol
2019 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
2020 loads - load S-Record file over serial line
2021 loadb - load binary file over serial line (kermit mode)
2022 loadm - load binary blob from source address to destination address
2024 mm - memory modify (auto-incrementing)
2025 nm - memory modify (constant address)
2026 mw - memory write (fill)
2029 cmp - memory compare
2030 crc32 - checksum calculation
2031 i2c - I2C sub-system
2032 sspi - SPI utility commands
2033 base - print or set address offset
2034 printenv- print environment variables
2035 pwm - control pwm channels
2036 setenv - set environment variables
2037 saveenv - save environment variables to persistent storage
2038 protect - enable or disable FLASH write protection
2039 erase - erase FLASH memory
2040 flinfo - print FLASH memory information
2041 nand - NAND memory operations (see doc/README.nand)
2042 bdinfo - print Board Info structure
2043 iminfo - print header information for application image
2044 coninfo - print console devices and informations
2045 ide - IDE sub-system
2046 loop - infinite loop on address range
2047 loopw - infinite write loop on address range
2048 mtest - simple RAM test
2049 icache - enable or disable instruction cache
2050 dcache - enable or disable data cache
2051 reset - Perform RESET of the CPU
2052 echo - echo args to console
2053 version - print monitor version
2054 help - print online help
2055 ? - alias for 'help'
2058 Monitor Commands - Detailed Description:
2059 ========================================
2063 For now: just type "help <command>".
2066 Note for Redundant Ethernet Interfaces:
2067 =======================================
2069 Some boards come with redundant Ethernet interfaces; U-Boot supports
2070 such configurations and is capable of automatic selection of a
2071 "working" interface when needed. MAC assignment works as follows:
2073 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
2074 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
2075 "eth1addr" (=>eth1), "eth2addr", ...
2077 If the network interface stores some valid MAC address (for instance
2078 in SROM), this is used as default address if there is NO correspon-
2079 ding setting in the environment; if the corresponding environment
2080 variable is set, this overrides the settings in the card; that means:
2082 o If the SROM has a valid MAC address, and there is no address in the
2083 environment, the SROM's address is used.
2085 o If there is no valid address in the SROM, and a definition in the
2086 environment exists, then the value from the environment variable is
2089 o If both the SROM and the environment contain a MAC address, and
2090 both addresses are the same, this MAC address is used.
2092 o If both the SROM and the environment contain a MAC address, and the
2093 addresses differ, the value from the environment is used and a
2096 o If neither SROM nor the environment contain a MAC address, an error
2097 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
2098 a random, locally-assigned MAC is used.
2100 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
2101 will be programmed into hardware as part of the initialization process. This
2102 may be skipped by setting the appropriate 'ethmacskip' environment variable.
2103 The naming convention is as follows:
2104 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
2109 U-Boot is capable of booting (and performing other auxiliary operations on)
2110 images in two formats:
2112 New uImage format (FIT)
2113 -----------------------
2115 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
2116 to Flattened Device Tree). It allows the use of images with multiple
2117 components (several kernels, ramdisks, etc.), with contents protected by
2118 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
2124 Old image format is based on binary files which can be basically anything,
2125 preceded by a special header; see the definitions in include/image.h for
2126 details; basically, the header defines the following image properties:
2128 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
2129 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
2130 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
2131 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
2132 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
2133 IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
2134 Currently supported: ARM, Intel x86, MIPS, Nios II, PowerPC).
2135 * Compression Type (uncompressed, gzip, bzip2)
2141 The header is marked by a special Magic Number, and both the header
2142 and the data portions of the image are secured against corruption by
2149 Although U-Boot should support any OS or standalone application
2150 easily, the main focus has always been on Linux during the design of
2153 U-Boot includes many features that so far have been part of some
2154 special "boot loader" code within the Linux kernel. Also, any
2155 "initrd" images to be used are no longer part of one big Linux image;
2156 instead, kernel and "initrd" are separate images. This implementation
2157 serves several purposes:
2159 - the same features can be used for other OS or standalone
2160 applications (for instance: using compressed images to reduce the
2161 Flash memory footprint)
2163 - it becomes much easier to port new Linux kernel versions because
2164 lots of low-level, hardware dependent stuff are done by U-Boot
2166 - the same Linux kernel image can now be used with different "initrd"
2167 images; of course this also means that different kernel images can
2168 be run with the same "initrd". This makes testing easier (you don't
2169 have to build a new "zImage.initrd" Linux image when you just
2170 change a file in your "initrd"). Also, a field-upgrade of the
2171 software is easier now.
2177 Porting Linux to U-Boot based systems:
2178 ---------------------------------------
2180 U-Boot cannot save you from doing all the necessary modifications to
2181 configure the Linux device drivers for use with your target hardware
2182 (no, we don't intend to provide a full virtual machine interface to
2185 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
2187 Just make sure your machine specific header file (for instance
2188 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2189 Information structure as we define in include/asm-<arch>/u-boot.h,
2190 and make sure that your definition of IMAP_ADDR uses the same value
2191 as your U-Boot configuration in CONFIG_SYS_IMMR.
2193 Note that U-Boot now has a driver model, a unified model for drivers.
2194 If you are adding a new driver, plumb it into driver model. If there
2195 is no uclass available, you are encouraged to create one. See
2199 Configuring the Linux kernel:
2200 -----------------------------
2202 No specific requirements for U-Boot. Make sure you have some root
2203 device (initial ramdisk, NFS) for your target system.
2206 Building a Linux Image:
2207 -----------------------
2209 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2210 not used. If you use recent kernel source, a new build target
2211 "uImage" will exist which automatically builds an image usable by
2212 U-Boot. Most older kernels also have support for a "pImage" target,
2213 which was introduced for our predecessor project PPCBoot and uses a
2214 100% compatible format.
2218 make TQM850L_defconfig
2223 The "uImage" build target uses a special tool (in 'tools/mkimage') to
2224 encapsulate a compressed Linux kernel image with header information,
2225 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2227 * build a standard "vmlinux" kernel image (in ELF binary format):
2229 * convert the kernel into a raw binary image:
2231 ${CROSS_COMPILE}-objcopy -O binary \
2232 -R .note -R .comment \
2233 -S vmlinux linux.bin
2235 * compress the binary image:
2239 * package compressed binary image for U-Boot:
2241 mkimage -A ppc -O linux -T kernel -C gzip \
2242 -a 0 -e 0 -n "Linux Kernel Image" \
2243 -d linux.bin.gz uImage
2246 The "mkimage" tool can also be used to create ramdisk images for use
2247 with U-Boot, either separated from the Linux kernel image, or
2248 combined into one file. "mkimage" encapsulates the images with a 64
2249 byte header containing information about target architecture,
2250 operating system, image type, compression method, entry points, time
2251 stamp, CRC32 checksums, etc.
2253 "mkimage" can be called in two ways: to verify existing images and
2254 print the header information, or to build new images.
2256 In the first form (with "-l" option) mkimage lists the information
2257 contained in the header of an existing U-Boot image; this includes
2258 checksum verification:
2260 tools/mkimage -l image
2261 -l ==> list image header information
2263 The second form (with "-d" option) is used to build a U-Boot image
2264 from a "data file" which is used as image payload:
2266 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
2267 -n name -d data_file image
2268 -A ==> set architecture to 'arch'
2269 -O ==> set operating system to 'os'
2270 -T ==> set image type to 'type'
2271 -C ==> set compression type 'comp'
2272 -a ==> set load address to 'addr' (hex)
2273 -e ==> set entry point to 'ep' (hex)
2274 -n ==> set image name to 'name'
2275 -d ==> use image data from 'datafile'
2277 Right now, all Linux kernels for PowerPC systems use the same load
2278 address (0x00000000), but the entry point address depends on the
2281 - 2.2.x kernels have the entry point at 0x0000000C,
2282 - 2.3.x and later kernels have the entry point at 0x00000000.
2284 So a typical call to build a U-Boot image would read:
2286 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2287 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
2288 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
2289 > examples/uImage.TQM850L
2290 Image Name: 2.4.4 kernel for TQM850L
2291 Created: Wed Jul 19 02:34:59 2000
2292 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2293 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2294 Load Address: 0x00000000
2295 Entry Point: 0x00000000
2297 To verify the contents of the image (or check for corruption):
2299 -> tools/mkimage -l examples/uImage.TQM850L
2300 Image Name: 2.4.4 kernel for TQM850L
2301 Created: Wed Jul 19 02:34:59 2000
2302 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2303 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2304 Load Address: 0x00000000
2305 Entry Point: 0x00000000
2307 NOTE: for embedded systems where boot time is critical you can trade
2308 speed for memory and install an UNCOMPRESSED image instead: this
2309 needs more space in Flash, but boots much faster since it does not
2310 need to be uncompressed:
2312 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
2313 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2314 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
2315 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
2316 > examples/uImage.TQM850L-uncompressed
2317 Image Name: 2.4.4 kernel for TQM850L
2318 Created: Wed Jul 19 02:34:59 2000
2319 Image Type: PowerPC Linux Kernel Image (uncompressed)
2320 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
2321 Load Address: 0x00000000
2322 Entry Point: 0x00000000
2325 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
2326 when your kernel is intended to use an initial ramdisk:
2328 -> tools/mkimage -n 'Simple Ramdisk Image' \
2329 > -A ppc -O linux -T ramdisk -C gzip \
2330 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
2331 Image Name: Simple Ramdisk Image
2332 Created: Wed Jan 12 14:01:50 2000
2333 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2334 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
2335 Load Address: 0x00000000
2336 Entry Point: 0x00000000
2338 The "dumpimage" tool can be used to disassemble or list the contents of images
2339 built by mkimage. See dumpimage's help output (-h) for details.
2341 Installing a Linux Image:
2342 -------------------------
2344 To downloading a U-Boot image over the serial (console) interface,
2345 you must convert the image to S-Record format:
2347 objcopy -I binary -O srec examples/image examples/image.srec
2349 The 'objcopy' does not understand the information in the U-Boot
2350 image header, so the resulting S-Record file will be relative to
2351 address 0x00000000. To load it to a given address, you need to
2352 specify the target address as 'offset' parameter with the 'loads'
2355 Example: install the image to address 0x40100000 (which on the
2356 TQM8xxL is in the first Flash bank):
2358 => erase 40100000 401FFFFF
2364 ## Ready for S-Record download ...
2365 ~>examples/image.srec
2366 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
2368 15989 15990 15991 15992
2369 [file transfer complete]
2371 ## Start Addr = 0x00000000
2374 You can check the success of the download using the 'iminfo' command;
2375 this includes a checksum verification so you can be sure no data
2376 corruption happened:
2380 ## Checking Image at 40100000 ...
2381 Image Name: 2.2.13 for initrd on TQM850L
2382 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2383 Data Size: 335725 Bytes = 327 kB = 0 MB
2384 Load Address: 00000000
2385 Entry Point: 0000000c
2386 Verifying Checksum ... OK
2392 The "bootm" command is used to boot an application that is stored in
2393 memory (RAM or Flash). In case of a Linux kernel image, the contents
2394 of the "bootargs" environment variable is passed to the kernel as
2395 parameters. You can check and modify this variable using the
2396 "printenv" and "setenv" commands:
2399 => printenv bootargs
2400 bootargs=root=/dev/ram
2402 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2404 => printenv bootargs
2405 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2408 ## Booting Linux kernel at 40020000 ...
2409 Image Name: 2.2.13 for NFS on TQM850L
2410 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2411 Data Size: 381681 Bytes = 372 kB = 0 MB
2412 Load Address: 00000000
2413 Entry Point: 0000000c
2414 Verifying Checksum ... OK
2415 Uncompressing Kernel Image ... OK
2416 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
2417 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2418 time_init: decrementer frequency = 187500000/60
2419 Calibrating delay loop... 49.77 BogoMIPS
2420 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
2423 If you want to boot a Linux kernel with initial RAM disk, you pass
2424 the memory addresses of both the kernel and the initrd image (PPBCOOT
2425 format!) to the "bootm" command:
2427 => imi 40100000 40200000
2429 ## Checking Image at 40100000 ...
2430 Image Name: 2.2.13 for initrd on TQM850L
2431 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2432 Data Size: 335725 Bytes = 327 kB = 0 MB
2433 Load Address: 00000000
2434 Entry Point: 0000000c
2435 Verifying Checksum ... OK
2437 ## Checking Image at 40200000 ...
2438 Image Name: Simple Ramdisk Image
2439 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2440 Data Size: 566530 Bytes = 553 kB = 0 MB
2441 Load Address: 00000000
2442 Entry Point: 00000000
2443 Verifying Checksum ... OK
2445 => bootm 40100000 40200000
2446 ## Booting Linux kernel at 40100000 ...
2447 Image Name: 2.2.13 for initrd on TQM850L
2448 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2449 Data Size: 335725 Bytes = 327 kB = 0 MB
2450 Load Address: 00000000
2451 Entry Point: 0000000c
2452 Verifying Checksum ... OK
2453 Uncompressing Kernel Image ... OK
2454 ## Loading RAMDisk Image at 40200000 ...
2455 Image Name: Simple Ramdisk Image
2456 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2457 Data Size: 566530 Bytes = 553 kB = 0 MB
2458 Load Address: 00000000
2459 Entry Point: 00000000
2460 Verifying Checksum ... OK
2461 Loading Ramdisk ... OK
2462 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
2463 Boot arguments: root=/dev/ram
2464 time_init: decrementer frequency = 187500000/60
2465 Calibrating delay loop... 49.77 BogoMIPS
2467 RAMDISK: Compressed image found at block 0
2468 VFS: Mounted root (ext2 filesystem).
2472 Boot Linux and pass a flat device tree:
2475 First, U-Boot must be compiled with the appropriate defines. See the section
2476 titled "Linux Kernel Interface" above for a more in depth explanation. The
2477 following is an example of how to start a kernel and pass an updated
2483 oft=oftrees/mpc8540ads.dtb
2484 => tftp $oftaddr $oft
2485 Speed: 1000, full duplex
2487 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
2488 Filename 'oftrees/mpc8540ads.dtb'.
2489 Load address: 0x300000
2492 Bytes transferred = 4106 (100a hex)
2493 => tftp $loadaddr $bootfile
2494 Speed: 1000, full duplex
2496 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
2498 Load address: 0x200000
2499 Loading:############
2501 Bytes transferred = 1029407 (fb51f hex)
2506 => bootm $loadaddr - $oftaddr
2507 ## Booting image at 00200000 ...
2508 Image Name: Linux-2.6.17-dirty
2509 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2510 Data Size: 1029343 Bytes = 1005.2 kB
2511 Load Address: 00000000
2512 Entry Point: 00000000
2513 Verifying Checksum ... OK
2514 Uncompressing Kernel Image ... OK
2515 Booting using flat device tree at 0x300000
2516 Using MPC85xx ADS machine description
2517 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
2521 More About U-Boot Image Types:
2522 ------------------------------
2524 U-Boot supports the following image types:
2526 "Standalone Programs" are directly runnable in the environment
2527 provided by U-Boot; it is expected that (if they behave
2528 well) you can continue to work in U-Boot after return from
2529 the Standalone Program.
2530 "OS Kernel Images" are usually images of some Embedded OS which
2531 will take over control completely. Usually these programs
2532 will install their own set of exception handlers, device
2533 drivers, set up the MMU, etc. - this means, that you cannot
2534 expect to re-enter U-Boot except by resetting the CPU.
2535 "RAMDisk Images" are more or less just data blocks, and their
2536 parameters (address, size) are passed to an OS kernel that is
2538 "Multi-File Images" contain several images, typically an OS
2539 (Linux) kernel image and one or more data images like
2540 RAMDisks. This construct is useful for instance when you want
2541 to boot over the network using BOOTP etc., where the boot
2542 server provides just a single image file, but you want to get
2543 for instance an OS kernel and a RAMDisk image.
2545 "Multi-File Images" start with a list of image sizes, each
2546 image size (in bytes) specified by an "uint32_t" in network
2547 byte order. This list is terminated by an "(uint32_t)0".
2548 Immediately after the terminating 0 follow the images, one by
2549 one, all aligned on "uint32_t" boundaries (size rounded up to
2550 a multiple of 4 bytes).
2552 "Firmware Images" are binary images containing firmware (like
2553 U-Boot or FPGA images) which usually will be programmed to
2556 "Script files" are command sequences that will be executed by
2557 U-Boot's command interpreter; this feature is especially
2558 useful when you configure U-Boot to use a real shell (hush)
2559 as command interpreter.
2561 Booting the Linux zImage:
2562 -------------------------
2564 On some platforms, it's possible to boot Linux zImage. This is done
2565 using the "bootz" command. The syntax of "bootz" command is the same
2566 as the syntax of "bootm" command.
2568 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
2569 kernel with raw initrd images. The syntax is slightly different, the
2570 address of the initrd must be augmented by it's size, in the following
2571 format: "<initrd addres>:<initrd size>".
2577 One of the features of U-Boot is that you can dynamically load and
2578 run "standalone" applications, which can use some resources of
2579 U-Boot like console I/O functions or interrupt services.
2581 Two simple examples are included with the sources:
2586 'examples/hello_world.c' contains a small "Hello World" Demo
2587 application; it is automatically compiled when you build U-Boot.
2588 It's configured to run at address 0x00040004, so you can play with it
2592 ## Ready for S-Record download ...
2593 ~>examples/hello_world.srec
2594 1 2 3 4 5 6 7 8 9 10 11 ...
2595 [file transfer complete]
2597 ## Start Addr = 0x00040004
2599 => go 40004 Hello World! This is a test.
2600 ## Starting application at 0x00040004 ...
2611 Hit any key to exit ...
2613 ## Application terminated, rc = 0x0
2615 Another example, which demonstrates how to register a CPM interrupt
2616 handler with the U-Boot code, can be found in 'examples/timer.c'.
2617 Here, a CPM timer is set up to generate an interrupt every second.
2618 The interrupt service routine is trivial, just printing a '.'
2619 character, but this is just a demo program. The application can be
2620 controlled by the following keys:
2622 ? - print current values og the CPM Timer registers
2623 b - enable interrupts and start timer
2624 e - stop timer and disable interrupts
2625 q - quit application
2628 ## Ready for S-Record download ...
2629 ~>examples/timer.srec
2630 1 2 3 4 5 6 7 8 9 10 11 ...
2631 [file transfer complete]
2633 ## Start Addr = 0x00040004
2636 ## Starting application at 0x00040004 ...
2639 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
2642 [q, b, e, ?] Set interval 1000000 us
2645 [q, b, e, ?] ........
2646 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
2649 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
2652 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
2655 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
2657 [q, b, e, ?] ...Stopping timer
2659 [q, b, e, ?] ## Application terminated, rc = 0x0
2665 Over time, many people have reported problems when trying to use the
2666 "minicom" terminal emulation program for serial download. I (wd)
2667 consider minicom to be broken, and recommend not to use it. Under
2668 Unix, I recommend to use C-Kermit for general purpose use (and
2669 especially for kermit binary protocol download ("loadb" command), and
2670 use "cu" for S-Record download ("loads" command). See
2671 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
2672 for help with kermit.
2675 Nevertheless, if you absolutely want to use it try adding this
2676 configuration to your "File transfer protocols" section:
2678 Name Program Name U/D FullScr IO-Red. Multi
2679 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
2680 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
2686 Starting at version 0.9.2, U-Boot supports NetBSD both as host
2687 (build U-Boot) and target system (boots NetBSD/mpc8xx).
2689 Building requires a cross environment; it is known to work on
2690 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
2691 need gmake since the Makefiles are not compatible with BSD make).
2692 Note that the cross-powerpc package does not install include files;
2693 attempting to build U-Boot will fail because <machine/ansi.h> is
2694 missing. This file has to be installed and patched manually:
2696 # cd /usr/pkg/cross/powerpc-netbsd/include
2698 # ln -s powerpc machine
2699 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
2700 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
2702 Native builds *don't* work due to incompatibilities between native
2703 and U-Boot include files.
2705 Booting assumes that (the first part of) the image booted is a
2706 stage-2 loader which in turn loads and then invokes the kernel
2707 proper. Loader sources will eventually appear in the NetBSD source
2708 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
2709 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
2712 Implementation Internals:
2713 =========================
2715 The following is not intended to be a complete description of every
2716 implementation detail. However, it should help to understand the
2717 inner workings of U-Boot and make it easier to port it to custom
2721 Initial Stack, Global Data:
2722 ---------------------------
2724 The implementation of U-Boot is complicated by the fact that U-Boot
2725 starts running out of ROM (flash memory), usually without access to
2726 system RAM (because the memory controller is not initialized yet).
2727 This means that we don't have writable Data or BSS segments, and BSS
2728 is not initialized as zero. To be able to get a C environment working
2729 at all, we have to allocate at least a minimal stack. Implementation
2730 options for this are defined and restricted by the CPU used: Some CPU
2731 models provide on-chip memory (like the IMMR area on MPC8xx and
2732 MPC826x processors), on others (parts of) the data cache can be
2733 locked as (mis-) used as memory, etc.
2735 Chris Hallinan posted a good summary of these issues to the
2736 U-Boot mailing list:
2738 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
2739 From: "Chris Hallinan" <clh@net1plus.com>
2740 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
2743 Correct me if I'm wrong, folks, but the way I understand it
2744 is this: Using DCACHE as initial RAM for Stack, etc, does not
2745 require any physical RAM backing up the cache. The cleverness
2746 is that the cache is being used as a temporary supply of
2747 necessary storage before the SDRAM controller is setup. It's
2748 beyond the scope of this list to explain the details, but you
2749 can see how this works by studying the cache architecture and
2750 operation in the architecture and processor-specific manuals.
2752 OCM is On Chip Memory, which I believe the 405GP has 4K. It
2753 is another option for the system designer to use as an
2754 initial stack/RAM area prior to SDRAM being available. Either
2755 option should work for you. Using CS 4 should be fine if your
2756 board designers haven't used it for something that would
2757 cause you grief during the initial boot! It is frequently not
2760 CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
2761 with your processor/board/system design. The default value
2762 you will find in any recent u-boot distribution in
2763 walnut.h should work for you. I'd set it to a value larger
2764 than your SDRAM module. If you have a 64MB SDRAM module, set
2765 it above 400_0000. Just make sure your board has no resources
2766 that are supposed to respond to that address! That code in
2767 start.S has been around a while and should work as is when
2768 you get the config right.
2773 It is essential to remember this, since it has some impact on the C
2774 code for the initialization procedures:
2776 * Initialized global data (data segment) is read-only. Do not attempt
2779 * Do not use any uninitialized global data (or implicitly initialized
2780 as zero data - BSS segment) at all - this is undefined, initiali-
2781 zation is performed later (when relocating to RAM).
2783 * Stack space is very limited. Avoid big data buffers or things like
2786 Having only the stack as writable memory limits means we cannot use
2787 normal global data to share information between the code. But it
2788 turned out that the implementation of U-Boot can be greatly
2789 simplified by making a global data structure (gd_t) available to all
2790 functions. We could pass a pointer to this data as argument to _all_
2791 functions, but this would bloat the code. Instead we use a feature of
2792 the GCC compiler (Global Register Variables) to share the data: we
2793 place a pointer (gd) to the global data into a register which we
2794 reserve for this purpose.
2796 When choosing a register for such a purpose we are restricted by the
2797 relevant (E)ABI specifications for the current architecture, and by
2798 GCC's implementation.
2800 For PowerPC, the following registers have specific use:
2802 R2: reserved for system use
2803 R3-R4: parameter passing and return values
2804 R5-R10: parameter passing
2805 R13: small data area pointer
2809 (U-Boot also uses R12 as internal GOT pointer. r12
2810 is a volatile register so r12 needs to be reset when
2811 going back and forth between asm and C)
2813 ==> U-Boot will use R2 to hold a pointer to the global data
2815 Note: on PPC, we could use a static initializer (since the
2816 address of the global data structure is known at compile time),
2817 but it turned out that reserving a register results in somewhat
2818 smaller code - although the code savings are not that big (on
2819 average for all boards 752 bytes for the whole U-Boot image,
2820 624 text + 127 data).
2822 On ARM, the following registers are used:
2824 R0: function argument word/integer result
2825 R1-R3: function argument word
2826 R9: platform specific
2827 R10: stack limit (used only if stack checking is enabled)
2828 R11: argument (frame) pointer
2829 R12: temporary workspace
2832 R15: program counter
2834 ==> U-Boot will use R9 to hold a pointer to the global data
2836 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
2838 On Nios II, the ABI is documented here:
2839 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
2841 ==> U-Boot will use gp to hold a pointer to the global data
2843 Note: on Nios II, we give "-G0" option to gcc and don't use gp
2844 to access small data sections, so gp is free.
2846 On RISC-V, the following registers are used:
2848 x0: hard-wired zero (zero)
2849 x1: return address (ra)
2850 x2: stack pointer (sp)
2851 x3: global pointer (gp)
2852 x4: thread pointer (tp)
2853 x5: link register (t0)
2854 x8: frame pointer (fp)
2855 x10-x11: arguments/return values (a0-1)
2856 x12-x17: arguments (a2-7)
2857 x28-31: temporaries (t3-6)
2858 pc: program counter (pc)
2860 ==> U-Boot will use gp to hold a pointer to the global data
2865 U-Boot runs in system state and uses physical addresses, i.e. the
2866 MMU is not used either for address mapping nor for memory protection.
2868 The available memory is mapped to fixed addresses using the memory
2869 controller. In this process, a contiguous block is formed for each
2870 memory type (Flash, SDRAM, SRAM), even when it consists of several
2871 physical memory banks.
2873 U-Boot is installed in the first 128 kB of the first Flash bank (on
2874 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
2875 booting and sizing and initializing DRAM, the code relocates itself
2876 to the upper end of DRAM. Immediately below the U-Boot code some
2877 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
2878 configuration setting]. Below that, a structure with global Board
2879 Info data is placed, followed by the stack (growing downward).
2881 Additionally, some exception handler code is copied to the low 8 kB
2882 of DRAM (0x00000000 ... 0x00001FFF).
2884 So a typical memory configuration with 16 MB of DRAM could look like
2887 0x0000 0000 Exception Vector code
2890 0x0000 2000 Free for Application Use
2896 0x00FB FF20 Monitor Stack (Growing downward)
2897 0x00FB FFAC Board Info Data and permanent copy of global data
2898 0x00FC 0000 Malloc Arena
2901 0x00FE 0000 RAM Copy of Monitor Code
2902 ... eventually: LCD or video framebuffer
2903 ... eventually: pRAM (Protected RAM - unchanged by reset)
2904 0x00FF FFFF [End of RAM]
2907 System Initialization:
2908 ----------------------
2910 In the reset configuration, U-Boot starts at the reset entry point
2911 (on most PowerPC systems at address 0x00000100). Because of the reset
2912 configuration for CS0# this is a mirror of the on board Flash memory.
2913 To be able to re-map memory U-Boot then jumps to its link address.
2914 To be able to implement the initialization code in C, a (small!)
2915 initial stack is set up in the internal Dual Ported RAM (in case CPUs
2916 which provide such a feature like), or in a locked part of the data
2917 cache. After that, U-Boot initializes the CPU core, the caches and
2920 Next, all (potentially) available memory banks are mapped using a
2921 preliminary mapping. For example, we put them on 512 MB boundaries
2922 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
2923 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
2924 programmed for SDRAM access. Using the temporary configuration, a
2925 simple memory test is run that determines the size of the SDRAM
2928 When there is more than one SDRAM bank, and the banks are of
2929 different size, the largest is mapped first. For equal size, the first
2930 bank (CS2#) is mapped first. The first mapping is always for address
2931 0x00000000, with any additional banks following immediately to create
2932 contiguous memory starting from 0.
2934 Then, the monitor installs itself at the upper end of the SDRAM area
2935 and allocates memory for use by malloc() and for the global Board
2936 Info data; also, the exception vector code is copied to the low RAM
2937 pages, and the final stack is set up.
2939 Only after this relocation will you have a "normal" C environment;
2940 until that you are restricted in several ways, mostly because you are
2941 running from ROM, and because the code will have to be relocated to a
2945 U-Boot Porting Guide:
2946 ----------------------
2948 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
2952 int main(int argc, char *argv[])
2954 sighandler_t no_more_time;
2956 signal(SIGALRM, no_more_time);
2957 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
2959 if (available_money > available_manpower) {
2960 Pay consultant to port U-Boot;
2964 Download latest U-Boot source;
2966 Subscribe to u-boot mailing list;
2969 email("Hi, I am new to U-Boot, how do I get started?");
2972 Read the README file in the top level directory;
2973 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
2974 Read applicable doc/README.*;
2975 Read the source, Luke;
2976 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
2979 if (available_money > toLocalCurrency ($2500))
2982 Add a lot of aggravation and time;
2984 if (a similar board exists) { /* hopefully... */
2985 cp -a board/<similar> board/<myboard>
2986 cp include/configs/<similar>.h include/configs/<myboard>.h
2988 Create your own board support subdirectory;
2989 Create your own board include/configs/<myboard>.h file;
2991 Edit new board/<myboard> files
2992 Edit new include/configs/<myboard>.h
2997 Add / modify source code;
3001 email("Hi, I am having problems...");
3003 Send patch file to the U-Boot email list;
3004 if (reasonable critiques)
3005 Incorporate improvements from email list code review;
3007 Defend code as written;
3013 void no_more_time (int sig)
3022 All contributions to U-Boot should conform to the Linux kernel
3023 coding style; see the kernel coding style guide at
3024 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
3025 script "scripts/Lindent" in your Linux kernel source directory.
3027 Source files originating from a different project (for example the
3028 MTD subsystem) are generally exempt from these guidelines and are not
3029 reformatted to ease subsequent migration to newer versions of those
3032 Please note that U-Boot is implemented in C (and to some small parts in
3033 Assembler); no C++ is used, so please do not use C++ style comments (//)
3036 Please also stick to the following formatting rules:
3037 - remove any trailing white space
3038 - use TAB characters for indentation and vertical alignment, not spaces
3039 - make sure NOT to use DOS '\r\n' line feeds
3040 - do not add more than 2 consecutive empty lines to source files
3041 - do not add trailing empty lines to source files
3043 Submissions which do not conform to the standards may be returned
3044 with a request to reformat the changes.
3050 Since the number of patches for U-Boot is growing, we need to
3051 establish some rules. Submissions which do not conform to these rules
3052 may be rejected, even when they contain important and valuable stuff.
3054 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
3056 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
3057 see https://lists.denx.de/listinfo/u-boot
3059 When you send a patch, please include the following information with
3062 * For bug fixes: a description of the bug and how your patch fixes
3063 this bug. Please try to include a way of demonstrating that the
3064 patch actually fixes something.
3066 * For new features: a description of the feature and your
3069 * For major contributions, add a MAINTAINERS file with your
3070 information and associated file and directory references.
3072 * When you add support for a new board, don't forget to add a
3073 maintainer e-mail address to the boards.cfg file, too.
3075 * If your patch adds new configuration options, don't forget to
3076 document these in the README file.
3078 * The patch itself. If you are using git (which is *strongly*
3079 recommended) you can easily generate the patch using the
3080 "git format-patch". If you then use "git send-email" to send it to
3081 the U-Boot mailing list, you will avoid most of the common problems
3082 with some other mail clients.
3084 If you cannot use git, use "diff -purN OLD NEW". If your version of
3085 diff does not support these options, then get the latest version of
3088 The current directory when running this command shall be the parent
3089 directory of the U-Boot source tree (i. e. please make sure that
3090 your patch includes sufficient directory information for the
3093 We prefer patches as plain text. MIME attachments are discouraged,
3094 and compressed attachments must not be used.
3096 * If one logical set of modifications affects or creates several
3097 files, all these changes shall be submitted in a SINGLE patch file.
3099 * Changesets that contain different, unrelated modifications shall be
3100 submitted as SEPARATE patches, one patch per changeset.
3105 * Before sending the patch, run the buildman script on your patched
3106 source tree and make sure that no errors or warnings are reported
3107 for any of the boards.
3109 * Keep your modifications to the necessary minimum: A patch
3110 containing several unrelated changes or arbitrary reformats will be
3111 returned with a request to re-formatting / split it.
3113 * If you modify existing code, make sure that your new code does not
3114 add to the memory footprint of the code ;-) Small is beautiful!
3115 When adding new features, these should compile conditionally only
3116 (using #ifdef), and the resulting code with the new feature
3117 disabled must not need more memory than the old code without your
3120 * Remember that there is a size limit of 100 kB per message on the
3121 u-boot mailing list. Bigger patches will be moderated. If they are
3122 reasonable and not too big, they will be acknowledged. But patches
3123 bigger than the size limit should be avoided.