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 CFG_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 CFG_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 CFG_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_ISL1208 - use Intersil ISL1208 RTC
477 CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
478 CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
479 CONFIG_SYS_RV3029_TCR - enable trickle charger on
482 Note that if the RTC uses I2C, then the I2C interface
483 must also be configured. See I2C Support, below.
486 The CFG_SYS_I2C_PCA953X_WIDTH option specifies a list of
487 chip-ngpio pairs that tell the PCA953X driver the number of
488 pins supported by a particular chip.
490 Note that if the GPIO device uses I2C, then the I2C interface
491 must also be configured. See I2C Support, below.
494 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
495 accesses and can checksum them or write a list of them out
496 to memory. See the 'iotrace' command for details. This is
497 useful for testing device drivers since it can confirm that
498 the driver behaves the same way before and after a code
499 change. Currently this is supported on sandbox and arm. To
500 add support for your architecture, add '#include <iotrace.h>'
501 to the bottom of arch/<arch>/include/asm/io.h and test.
503 Example output from the 'iotrace stats' command is below.
504 Note that if the trace buffer is exhausted, the checksum will
505 still continue to operate.
508 Start: 10000000 (buffer start address)
509 Size: 00010000 (buffer size)
510 Offset: 00000120 (current buffer offset)
511 Output: 10000120 (start + offset)
512 Count: 00000018 (number of trace records)
513 CRC32: 9526fb66 (CRC32 of all trace records)
517 When CONFIG_TIMESTAMP is selected, the timestamp
518 (date and time) of an image is printed by image
519 commands like bootm or iminfo. This option is
520 automatically enabled when you select CONFIG_CMD_DATE .
522 - Partition Labels (disklabels) Supported:
523 Zero or more of the following:
524 CONFIG_MAC_PARTITION Apple's MacOS partition table.
525 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
526 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
527 bootloader. Note 2TB partition limit; see
529 CONFIG_SCSI) you must configure support for at
530 least one non-MTD partition type as well.
532 - NETWORK Support (PCI):
534 Utility code for direct access to the SPI bus on Intel 8257x.
535 This does not do anything useful unless you set at least one
536 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
539 Support for National dp83815 chips.
542 Support for National dp8382[01] gigabit chips.
544 - NETWORK Support (other):
546 Support for the Calxeda XGMAC device
549 Support for SMSC's LAN91C96 chips.
551 CONFIG_LAN91C96_USE_32_BIT
552 Define this to enable 32 bit addressing
554 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
555 Define this if you have more then 3 PHYs.
558 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
560 CONFIG_FTGMAC100_EGIGA
561 Define this to use GE link update with gigabit PHY.
562 Define this if FTGMAC100 is connected to gigabit PHY.
563 If your system has 10/100 PHY only, it might not occur
564 wrong behavior. Because PHY usually return timeout or
565 useless data when polling gigabit status and gigabit
566 control registers. This behavior won't affect the
567 correctnessof 10/100 link speed update.
570 Support for Renesas on-chip Ethernet controller
572 CONFIG_SH_ETHER_USE_PORT
573 Define the number of ports to be used
575 CONFIG_SH_ETHER_PHY_ADDR
576 Define the ETH PHY's address
578 CONFIG_SH_ETHER_CACHE_WRITEBACK
579 If this option is set, the driver enables cache flush.
585 CONFIG_TPM_TIS_INFINEON
586 Support for Infineon i2c bus TPM devices. Only one device
587 per system is supported at this time.
589 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
590 Define the burst count bytes upper limit
593 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
595 CONFIG_TPM_ST33ZP24_I2C
596 Support for STMicroelectronics ST33ZP24 I2C devices.
597 Requires TPM_ST33ZP24 and I2C.
599 CONFIG_TPM_ST33ZP24_SPI
600 Support for STMicroelectronics ST33ZP24 SPI devices.
601 Requires TPM_ST33ZP24 and SPI.
604 Support for Atmel TWI TPM device. Requires I2C support.
607 Support for generic parallel port TPM devices. Only one device
608 per system is supported at this time.
610 CONFIG_TPM_TIS_BASE_ADDRESS
611 Base address where the generic TPM device is mapped
612 to. Contemporary x86 systems usually map it at
616 Define this to enable the TPM support library which provides
617 functional interfaces to some TPM commands.
618 Requires support for a TPM device.
620 CONFIG_TPM_AUTH_SESSIONS
621 Define this to enable authorized functions in the TPM library.
622 Requires CONFIG_TPM and CONFIG_SHA1.
625 At the moment only the UHCI host controller is
626 supported (PIP405, MIP405); define
627 CONFIG_USB_UHCI to enable it.
628 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
629 and define CONFIG_USB_STORAGE to enable the USB
632 Supported are USB Keyboards and USB Floppy drives
635 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
639 Define the below if you wish to use the USB console.
640 Once firmware is rebuilt from a serial console issue the
641 command "setenv stdin usbtty; setenv stdout usbtty" and
642 attach your USB cable. The Unix command "dmesg" should print
643 it has found a new device. The environment variable usbtty
644 can be set to gserial or cdc_acm to enable your device to
645 appear to a USB host as a Linux gserial device or a
646 Common Device Class Abstract Control Model serial device.
647 If you select usbtty = gserial you should be able to enumerate
649 # modprobe usbserial vendor=0xVendorID product=0xProductID
650 else if using cdc_acm, simply setting the environment
651 variable usbtty to be cdc_acm should suffice. The following
652 might be defined in YourBoardName.h
655 Define this to build a UDC device
658 Define this to have a tty type of device available to
659 talk to the UDC device
662 Define this to enable the high speed support for usb
663 device and usbtty. If this feature is enabled, a routine
664 int is_usbd_high_speed(void)
665 also needs to be defined by the driver to dynamically poll
666 whether the enumeration has succeded at high speed or full
669 If you have a USB-IF assigned VendorID then you may wish to
670 define your own vendor specific values either in BoardName.h
671 or directly in usbd_vendor_info.h. If you don't define
672 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
673 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
674 should pretend to be a Linux device to it's target host.
676 CONFIG_USBD_MANUFACTURER
677 Define this string as the name of your company for
678 - CONFIG_USBD_MANUFACTURER "my company"
680 CONFIG_USBD_PRODUCT_NAME
681 Define this string as the name of your product
682 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
685 Define this as your assigned Vendor ID from the USB
686 Implementors Forum. This *must* be a genuine Vendor ID
687 to avoid polluting the USB namespace.
688 - CONFIG_USBD_VENDORID 0xFFFF
690 CONFIG_USBD_PRODUCTID
691 Define this as the unique Product ID
693 - CONFIG_USBD_PRODUCTID 0xFFFF
695 - ULPI Layer Support:
696 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
697 the generic ULPI layer. The generic layer accesses the ULPI PHY
698 via the platform viewport, so you need both the genric layer and
699 the viewport enabled. Currently only Chipidea/ARC based
700 viewport is supported.
701 To enable the ULPI layer support, define CONFIG_USB_ULPI and
702 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
703 If your ULPI phy needs a different reference clock than the
704 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
705 the appropriate value in Hz.
709 Support for Renesas on-chip MMCIF controller
712 Define the base address of MMCIF registers
715 Define the clock frequency for MMCIF
717 - USB Device Firmware Update (DFU) class support:
719 This enables the USB portion of the DFU USB class
722 This enables support for exposing NAND devices via DFU.
725 This enables support for exposing RAM via DFU.
726 Note: DFU spec refer to non-volatile memory usage, but
727 allow usages beyond the scope of spec - here RAM usage,
728 one that would help mostly the developer.
730 CONFIG_SYS_DFU_DATA_BUF_SIZE
731 Dfu transfer uses a buffer before writing data to the
732 raw storage device. Make the size (in bytes) of this buffer
733 configurable. The size of this buffer is also configurable
734 through the "dfu_bufsiz" environment variable.
736 CONFIG_SYS_DFU_MAX_FILE_SIZE
737 When updating files rather than the raw storage device,
738 we use a static buffer to copy the file into and then write
739 the buffer once we've been given the whole file. Define
740 this to the maximum filesize (in bytes) for the buffer.
741 Default is 4 MiB if undefined.
743 DFU_DEFAULT_POLL_TIMEOUT
744 Poll timeout [ms], is the timeout a device can send to the
745 host. The host must wait for this timeout before sending
746 a subsequent DFU_GET_STATUS request to the device.
748 DFU_MANIFEST_POLL_TIMEOUT
749 Poll timeout [ms], which the device sends to the host when
750 entering dfuMANIFEST state. Host waits this timeout, before
751 sending again an USB request to the device.
754 See Kconfig help for available keyboard drivers.
757 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
759 The clock frequency of the MII bus
761 CONFIG_PHY_CMD_DELAY (ppc4xx)
763 Some PHY like Intel LXT971A need extra delay after
764 command issued before MII status register can be read
769 Define a default value for the IP address to use for
770 the default Ethernet interface, in case this is not
771 determined through e.g. bootp.
772 (Environment variable "ipaddr")
777 Defines a default value for the IP address of a TFTP
778 server to contact when using the "tftboot" command.
779 (Environment variable "serverip")
781 - Gateway IP address:
784 Defines a default value for the IP address of the
785 default router where packets to other networks are
787 (Environment variable "gatewayip")
792 Defines a default value for the subnet mask (or
793 routing prefix) which is used to determine if an IP
794 address belongs to the local subnet or needs to be
795 forwarded through a router.
796 (Environment variable "netmask")
798 - BOOTP Recovery Mode:
799 CONFIG_BOOTP_RANDOM_DELAY
801 If you have many targets in a network that try to
802 boot using BOOTP, you may want to avoid that all
803 systems send out BOOTP requests at precisely the same
804 moment (which would happen for instance at recovery
805 from a power failure, when all systems will try to
806 boot, thus flooding the BOOTP server. Defining
807 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
808 inserted before sending out BOOTP requests. The
809 following delays are inserted then:
811 1st BOOTP request: delay 0 ... 1 sec
812 2nd BOOTP request: delay 0 ... 2 sec
813 3rd BOOTP request: delay 0 ... 4 sec
815 BOOTP requests: delay 0 ... 8 sec
817 CONFIG_BOOTP_ID_CACHE_SIZE
819 BOOTP packets are uniquely identified using a 32-bit ID. The
820 server will copy the ID from client requests to responses and
821 U-Boot will use this to determine if it is the destination of
822 an incoming response. Some servers will check that addresses
823 aren't in use before handing them out (usually using an ARP
824 ping) and therefore take up to a few hundred milliseconds to
825 respond. Network congestion may also influence the time it
826 takes for a response to make it back to the client. If that
827 time is too long, U-Boot will retransmit requests. In order
828 to allow earlier responses to still be accepted after these
829 retransmissions, U-Boot's BOOTP client keeps a small cache of
830 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
831 cache. The default is to keep IDs for up to four outstanding
832 requests. Increasing this will allow U-Boot to accept offers
833 from a BOOTP client in networks with unusually high latency.
835 - DHCP Advanced Options:
837 - Link-local IP address negotiation:
838 Negotiate with other link-local clients on the local network
839 for an address that doesn't require explicit configuration.
840 This is especially useful if a DHCP server cannot be guaranteed
841 to exist in all environments that the device must operate.
843 See doc/README.link-local for more information.
845 - MAC address from environment variables
847 FDT_SEQ_MACADDR_FROM_ENV
849 Fix-up device tree with MAC addresses fetched sequentially from
850 environment variables. This config work on assumption that
851 non-usable ethernet node of device-tree are either not present
852 or their status has been marked as "disabled".
857 The device id used in CDP trigger frames.
859 CONFIG_CDP_DEVICE_ID_PREFIX
861 A two character string which is prefixed to the MAC address
866 A printf format string which contains the ascii name of
867 the port. Normally is set to "eth%d" which sets
868 eth0 for the first Ethernet, eth1 for the second etc.
870 CONFIG_CDP_CAPABILITIES
872 A 32bit integer which indicates the device capabilities;
873 0x00000010 for a normal host which does not forwards.
877 An ascii string containing the version of the software.
881 An ascii string containing the name of the platform.
885 A 32bit integer sent on the trigger.
887 CONFIG_CDP_POWER_CONSUMPTION
889 A 16bit integer containing the power consumption of the
890 device in .1 of milliwatts.
892 CONFIG_CDP_APPLIANCE_VLAN_TYPE
894 A byte containing the id of the VLAN.
896 - Status LED: CONFIG_LED_STATUS
898 Several configurations allow to display the current
899 status using a LED. For instance, the LED will blink
900 fast while running U-Boot code, stop blinking as
901 soon as a reply to a BOOTP request was received, and
902 start blinking slow once the Linux kernel is running
903 (supported by a status LED driver in the Linux
904 kernel). Defining CONFIG_LED_STATUS enables this
909 CONFIG_LED_STATUS_GPIO
910 The status LED can be connected to a GPIO pin.
911 In such cases, the gpio_led driver can be used as a
912 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
913 to include the gpio_led driver in the U-Boot binary.
915 CONFIG_GPIO_LED_INVERTED_TABLE
916 Some GPIO connected LEDs may have inverted polarity in which
917 case the GPIO high value corresponds to LED off state and
918 GPIO low value corresponds to LED on state.
919 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
920 with a list of GPIO LEDs that have inverted polarity.
923 CFG_SYS_NUM_I2C_BUSES
924 Hold the number of i2c buses you want to use.
926 CONFIG_SYS_I2C_DIRECT_BUS
927 define this, if you don't use i2c muxes on your hardware.
928 if CFG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
932 define how many muxes are maximal consecutively connected
933 on one i2c bus. If you not use i2c muxes, omit this
937 hold a list of buses you want to use, only used if
938 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
939 a board with CFG_SYS_I2C_MAX_HOPS = 1 and
940 CFG_SYS_NUM_I2C_BUSES = 9:
942 CFG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
943 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
944 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
945 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
946 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
947 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
948 {1, {I2C_NULL_HOP}}, \
949 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
950 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
954 bus 0 on adapter 0 without a mux
955 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
956 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
957 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
958 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
959 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
960 bus 6 on adapter 1 without a mux
961 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
962 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
964 If you do not have i2c muxes on your board, omit this define.
966 - Legacy I2C Support:
967 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
968 then the following macros need to be defined (examples are
969 from include/configs/lwmon.h):
973 (Optional). Any commands necessary to enable the I2C
974 controller or configure ports.
976 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
980 The code necessary to make the I2C data line active
981 (driven). If the data line is open collector, this
984 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
988 The code necessary to make the I2C data line tri-stated
989 (inactive). If the data line is open collector, this
992 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
996 Code that returns true if the I2C data line is high,
999 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1003 If <bit> is true, sets the I2C data line high. If it
1004 is false, it clears it (low).
1006 eg: #define I2C_SDA(bit) \
1007 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
1008 else immr->im_cpm.cp_pbdat &= ~PB_SDA
1012 If <bit> is true, sets the I2C clock line high. If it
1013 is false, it clears it (low).
1015 eg: #define I2C_SCL(bit) \
1016 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
1017 else immr->im_cpm.cp_pbdat &= ~PB_SCL
1021 This delay is invoked four times per clock cycle so this
1022 controls the rate of data transfer. The data rate thus
1023 is 1 / (I2C_DELAY * 4). Often defined to be something
1026 #define I2C_DELAY udelay(2)
1028 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1030 If your arch supports the generic GPIO framework (asm/gpio.h),
1031 then you may alternatively define the two GPIOs that are to be
1032 used as SCL / SDA. Any of the previous I2C_xxx macros will
1033 have GPIO-based defaults assigned to them as appropriate.
1035 You should define these to the GPIO value as given directly to
1036 the generic GPIO functions.
1038 CONFIG_I2C_MULTI_BUS
1040 This option allows the use of multiple I2C buses, each of which
1041 must have a controller. At any point in time, only one bus is
1042 active. To switch to a different bus, use the 'i2c dev' command.
1043 Note that bus numbering is zero-based.
1045 CFG_SYS_I2C_NOPROBES
1047 This option specifies a list of I2C devices that will be skipped
1048 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
1049 is set, specify a list of bus-device pairs. Otherwise, specify
1050 a 1D array of device addresses
1053 #undef CONFIG_I2C_MULTI_BUS
1054 #define CFG_SYS_I2C_NOPROBES {0x50,0x68}
1056 will skip addresses 0x50 and 0x68 on a board with one I2C bus
1058 #define CONFIG_I2C_MULTI_BUS
1059 #define CFG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1061 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1065 If defined, then this indicates the I2C bus number for the RTC.
1066 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1068 CONFIG_SOFT_I2C_READ_REPEATED_START
1070 defining this will force the i2c_read() function in
1071 the soft_i2c driver to perform an I2C repeated start
1072 between writing the address pointer and reading the
1073 data. If this define is omitted the default behaviour
1074 of doing a stop-start sequence will be used. Most I2C
1075 devices can use either method, but some require one or
1078 - SPI Support: CONFIG_SPI
1080 Enables SPI driver (so far only tested with
1081 SPI EEPROM, also an instance works with Crystal A/D and
1082 D/As on the SACSng board)
1084 CONFIG_SYS_SPI_MXC_WAIT
1085 Timeout for waiting until spi transfer completed.
1086 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1088 - FPGA Support: CONFIG_FPGA
1090 Enables FPGA subsystem.
1092 CONFIG_FPGA_<vendor>
1094 Enables support for specific chip vendors.
1097 CONFIG_FPGA_<family>
1099 Enables support for FPGA family.
1100 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1102 CONFIG_SYS_FPGA_CHECK_BUSY
1104 Enable checks on FPGA configuration interface busy
1105 status by the configuration function. This option
1106 will require a board or device specific function to
1111 If defined, a function that provides delays in the FPGA
1112 configuration driver.
1114 CONFIG_SYS_FPGA_CHECK_ERROR
1116 Check for configuration errors during FPGA bitfile
1117 loading. For example, abort during Virtex II
1118 configuration if the INIT_B line goes low (which
1119 indicated a CRC error).
1121 CFG_SYS_FPGA_WAIT_INIT
1123 Maximum time to wait for the INIT_B line to de-assert
1124 after PROB_B has been de-asserted during a Virtex II
1125 FPGA configuration sequence. The default time is 500
1128 CFG_SYS_FPGA_WAIT_BUSY
1130 Maximum time to wait for BUSY to de-assert during
1131 Virtex II FPGA configuration. The default is 5 ms.
1133 CFG_SYS_FPGA_WAIT_CONFIG
1135 Time to wait after FPGA configuration. The default is
1138 - Vendor Parameter Protection:
1140 U-Boot considers the values of the environment
1141 variables "serial#" (Board Serial Number) and
1142 "ethaddr" (Ethernet Address) to be parameters that
1143 are set once by the board vendor / manufacturer, and
1144 protects these variables from casual modification by
1145 the user. Once set, these variables are read-only,
1146 and write or delete attempts are rejected. You can
1147 change this behaviour:
1149 If CONFIG_ENV_OVERWRITE is #defined in your config
1150 file, the write protection for vendor parameters is
1151 completely disabled. Anybody can change or delete
1154 Alternatively, if you define _both_ an ethaddr in the
1155 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1156 Ethernet address is installed in the environment,
1157 which can be changed exactly ONCE by the user. [The
1158 serial# is unaffected by this, i. e. it remains
1161 The same can be accomplished in a more flexible way
1162 for any variable by configuring the type of access
1163 to allow for those variables in the ".flags" variable
1164 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1169 Define this variable to enable the reservation of
1170 "protected RAM", i. e. RAM which is not overwritten
1171 by U-Boot. Define CONFIG_PRAM to hold the number of
1172 kB you want to reserve for pRAM. You can overwrite
1173 this default value by defining an environment
1174 variable "pram" to the number of kB you want to
1175 reserve. Note that the board info structure will
1176 still show the full amount of RAM. If pRAM is
1177 reserved, a new environment variable "mem" will
1178 automatically be defined to hold the amount of
1179 remaining RAM in a form that can be passed as boot
1180 argument to Linux, for instance like that:
1182 setenv bootargs ... mem=\${mem}
1185 This way you can tell Linux not to use this memory,
1186 either, which results in a memory region that will
1187 not be affected by reboots.
1189 *WARNING* If your board configuration uses automatic
1190 detection of the RAM size, you must make sure that
1191 this memory test is non-destructive. So far, the
1192 following board configurations are known to be
1195 IVMS8, IVML24, SPD8xx,
1196 HERMES, IP860, RPXlite, LWMON,
1202 In the current implementation, the local variables
1203 space and global environment variables space are
1204 separated. Local variables are those you define by
1205 simply typing `name=value'. To access a local
1206 variable later on, you have write `$name' or
1207 `${name}'; to execute the contents of a variable
1208 directly type `$name' at the command prompt.
1210 Global environment variables are those you use
1211 setenv/printenv to work with. To run a command stored
1212 in such a variable, you need to use the run command,
1213 and you must not use the '$' sign to access them.
1215 To store commands and special characters in a
1216 variable, please use double quotation marks
1217 surrounding the whole text of the variable, instead
1218 of the backslashes before semicolons and special
1221 - Default Environment:
1222 CONFIG_EXTRA_ENV_SETTINGS
1224 Define this to contain any number of null terminated
1225 strings (variable = value pairs) that will be part of
1226 the default environment compiled into the boot image.
1228 For example, place something like this in your
1229 board's config file:
1231 #define CONFIG_EXTRA_ENV_SETTINGS \
1235 Warning: This method is based on knowledge about the
1236 internal format how the environment is stored by the
1237 U-Boot code. This is NOT an official, exported
1238 interface! Although it is unlikely that this format
1239 will change soon, there is no guarantee either.
1240 You better know what you are doing here.
1242 Note: overly (ab)use of the default environment is
1243 discouraged. Make sure to check other ways to preset
1244 the environment like the "source" command or the
1247 CONFIG_DELAY_ENVIRONMENT
1249 Normally the environment is loaded when the board is
1250 initialised so that it is available to U-Boot. This inhibits
1251 that so that the environment is not available until
1252 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1253 this is instead controlled by the value of
1254 /config/load-environment.
1256 CONFIG_STANDALONE_LOAD_ADDR
1258 This option defines a board specific value for the
1259 address where standalone program gets loaded, thus
1260 overwriting the architecture dependent default
1263 - Automatic software updates via TFTP server
1265 CONFIG_UPDATE_TFTP_CNT_MAX
1266 CONFIG_UPDATE_TFTP_MSEC_MAX
1268 These options enable and control the auto-update feature;
1269 for a more detailed description refer to doc/README.update.
1271 - MTD Support (mtdparts command, UBI support)
1272 CONFIG_MTD_UBI_WL_THRESHOLD
1273 This parameter defines the maximum difference between the highest
1274 erase counter value and the lowest erase counter value of eraseblocks
1275 of UBI devices. When this threshold is exceeded, UBI starts performing
1276 wear leveling by means of moving data from eraseblock with low erase
1277 counter to eraseblocks with high erase counter.
1279 The default value should be OK for SLC NAND flashes, NOR flashes and
1280 other flashes which have eraseblock life-cycle 100000 or more.
1281 However, in case of MLC NAND flashes which typically have eraseblock
1282 life-cycle less than 10000, the threshold should be lessened (e.g.,
1283 to 128 or 256, although it does not have to be power of 2).
1287 CONFIG_MTD_UBI_BEB_LIMIT
1288 This option specifies the maximum bad physical eraseblocks UBI
1289 expects on the MTD device (per 1024 eraseblocks). If the
1290 underlying flash does not admit of bad eraseblocks (e.g. NOR
1291 flash), this value is ignored.
1293 NAND datasheets often specify the minimum and maximum NVM
1294 (Number of Valid Blocks) for the flashes' endurance lifetime.
1295 The maximum expected bad eraseblocks per 1024 eraseblocks
1296 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1297 which gives 20 for most NANDs (MaxNVB is basically the total
1298 count of eraseblocks on the chip).
1300 To put it differently, if this value is 20, UBI will try to
1301 reserve about 1.9% of physical eraseblocks for bad blocks
1302 handling. And that will be 1.9% of eraseblocks on the entire
1303 NAND chip, not just the MTD partition UBI attaches. This means
1304 that if you have, say, a NAND flash chip admits maximum 40 bad
1305 eraseblocks, and it is split on two MTD partitions of the same
1306 size, UBI will reserve 40 eraseblocks when attaching a
1311 CONFIG_MTD_UBI_FASTMAP
1312 Fastmap is a mechanism which allows attaching an UBI device
1313 in nearly constant time. Instead of scanning the whole MTD device it
1314 only has to locate a checkpoint (called fastmap) on the device.
1315 The on-flash fastmap contains all information needed to attach
1316 the device. Using fastmap makes only sense on large devices where
1317 attaching by scanning takes long. UBI will not automatically install
1318 a fastmap on old images, but you can set the UBI parameter
1319 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1320 that fastmap-enabled images are still usable with UBI implementations
1321 without fastmap support. On typical flash devices the whole fastmap
1322 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1324 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1325 Set this parameter to enable fastmap automatically on images
1329 CONFIG_MTD_UBI_FM_DEBUG
1330 Enable UBI fastmap debug
1335 Enable building of SPL globally.
1337 CONFIG_SPL_PANIC_ON_RAW_IMAGE
1338 When defined, SPL will panic() if the image it has
1339 loaded does not have a signature.
1340 Defining this is useful when code which loads images
1341 in SPL cannot guarantee that absolutely all read errors
1343 An example is the LPC32XX MLC NAND driver, which will
1344 consider that a completely unreadable NAND block is bad,
1345 and thus should be skipped silently.
1347 CONFIG_SPL_DISPLAY_PRINT
1348 For ARM, enable an optional function to print more information
1349 about the running system.
1351 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
1352 Set this for NAND SPL on PPC mpc83xx targets, so that
1353 start.S waits for the rest of the SPL to load before
1354 continuing (the hardware starts execution after just
1355 loading the first page rather than the full 4K).
1358 Support for a lightweight UBI (fastmap) scanner and
1361 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
1362 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
1363 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
1364 CFG_SYS_NAND_ECCPOS, CFG_SYS_NAND_ECCSIZE,
1365 CFG_SYS_NAND_ECCBYTES
1366 Defines the size and behavior of the NAND that SPL uses
1369 CFG_SYS_NAND_U_BOOT_DST
1370 Location in memory to load U-Boot to
1372 CFG_SYS_NAND_U_BOOT_SIZE
1373 Size of image to load
1375 CFG_SYS_NAND_U_BOOT_START
1376 Entry point in loaded image to jump to
1378 CONFIG_SPL_RAM_DEVICE
1379 Support for running image already present in ram, in SPL binary
1381 CONFIG_SPL_FIT_PRINT
1382 Printing information about a FIT image adds quite a bit of
1383 code to SPL. So this is normally disabled in SPL. Use this
1384 option to re-enable it. This will affect the output of the
1385 bootm command when booting a FIT image.
1387 - Interrupt support (PPC):
1389 There are common interrupt_init() and timer_interrupt()
1390 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
1391 for CPU specific initialization. interrupt_init_cpu()
1392 should set decrementer_count to appropriate value. If
1393 CPU resets decrementer automatically after interrupt
1394 (ppc4xx) it should set decrementer_count to zero.
1395 timer_interrupt() calls timer_interrupt_cpu() for CPU
1396 specific handling. If board has watchdog / status_led
1397 / other_activity_monitor it works automatically from
1398 general timer_interrupt().
1401 Board initialization settings:
1402 ------------------------------
1404 During Initialization u-boot calls a number of board specific functions
1405 to allow the preparation of board specific prerequisites, e.g. pin setup
1406 before drivers are initialized. To enable these callbacks the
1407 following configuration macros have to be defined. Currently this is
1408 architecture specific, so please check arch/your_architecture/lib/board.c
1409 typically in board_init_f() and board_init_r().
1411 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
1412 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
1413 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
1415 Configuration Settings:
1416 -----------------------
1418 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
1419 Optionally it can be defined to support 64-bit memory commands.
1421 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
1422 undefine this when you're short of memory.
1424 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
1425 width of the commands listed in the 'help' command output.
1427 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
1428 prompt for user input.
1430 - CFG_SYS_BAUDRATE_TABLE:
1431 List of legal baudrate settings for this board.
1433 - CFG_SYS_MEM_RESERVE_SECURE
1434 Only implemented for ARMv8 for now.
1435 If defined, the size of CFG_SYS_MEM_RESERVE_SECURE memory
1436 is substracted from total RAM and won't be reported to OS.
1437 This memory can be used as secure memory. A variable
1438 gd->arch.secure_ram is used to track the location. In systems
1439 the RAM base is not zero, or RAM is divided into banks,
1440 this variable needs to be recalcuated to get the address.
1442 - CFG_SYS_SDRAM_BASE:
1443 Physical start address of SDRAM. _Must_ be 0 here.
1445 - CFG_SYS_FLASH_BASE:
1446 Physical start address of Flash memory.
1448 - CONFIG_SYS_MALLOC_LEN:
1449 Size of DRAM reserved for malloc() use.
1451 - CONFIG_SYS_MALLOC_F_LEN
1452 Size of the malloc() pool for use before relocation. If
1453 this is defined, then a very simple malloc() implementation
1454 will become available before relocation. The address is just
1455 below the global data, and the stack is moved down to make
1458 This feature allocates regions with increasing addresses
1459 within the region. calloc() is supported, but realloc()
1460 is not available. free() is supported but does nothing.
1461 The memory will be freed (or in fact just forgotten) when
1462 U-Boot relocates itself.
1464 - CONFIG_SYS_MALLOC_SIMPLE
1465 Provides a simple and small malloc() and calloc() for those
1466 boards which do not use the full malloc in SPL (which is
1467 enabled with CONFIG_SYS_SPL_MALLOC).
1469 - CFG_SYS_BOOTMAPSZ:
1470 Maximum size of memory mapped by the startup code of
1471 the Linux kernel; all data that must be processed by
1472 the Linux kernel (bd_info, boot arguments, FDT blob if
1473 used) must be put below this limit, unless "bootm_low"
1474 environment variable is defined and non-zero. In such case
1475 all data for the Linux kernel must be between "bootm_low"
1476 and "bootm_low" + CFG_SYS_BOOTMAPSZ. The environment
1477 variable "bootm_mapsize" will override the value of
1478 CFG_SYS_BOOTMAPSZ. If CFG_SYS_BOOTMAPSZ is undefined,
1479 then the value in "bootm_size" will be used instead.
1481 - CONFIG_SYS_BOOT_GET_CMDLINE:
1482 Enables allocating and saving kernel cmdline in space between
1483 "bootm_low" and "bootm_low" + BOOTMAPSZ.
1485 - CONFIG_SYS_BOOT_GET_KBD:
1486 Enables allocating and saving a kernel copy of the bd_info in
1487 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
1489 - CONFIG_SYS_FLASH_PROTECTION
1490 If defined, hardware flash sectors protection is used
1491 instead of U-Boot software protection.
1493 - CONFIG_SYS_FLASH_CFI:
1494 Define if the flash driver uses extra elements in the
1495 common flash structure for storing flash geometry.
1497 - CONFIG_FLASH_CFI_DRIVER
1498 This option also enables the building of the cfi_flash driver
1499 in the drivers directory
1501 - CONFIG_FLASH_CFI_MTD
1502 This option enables the building of the cfi_mtd driver
1503 in the drivers directory. The driver exports CFI flash
1506 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
1507 Use buffered writes to flash.
1509 - CONFIG_FLASH_SPANSION_S29WS_N
1510 s29ws-n MirrorBit flash has non-standard addresses for buffered
1513 - CONFIG_FLASH_SHOW_PROGRESS
1514 If defined (must be an integer), print out countdown
1515 digits and dots. Recommended value: 45 (9..1) for 80
1516 column displays, 15 (3..1) for 40 column displays.
1518 - CONFIG_FLASH_VERIFY
1519 If defined, the content of the flash (destination) is compared
1520 against the source after the write operation. An error message
1521 will be printed when the contents are not identical.
1522 Please note that this option is useless in nearly all cases,
1523 since such flash programming errors usually are detected earlier
1524 while unprotecting/erasing/programming. Please only enable
1525 this option if you really know what you are doing.
1527 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1528 - CONFIG_ENV_FLAGS_LIST_STATIC
1529 Enable validation of the values given to environment variables when
1530 calling env set. Variables can be restricted to only decimal,
1531 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
1532 the variables can also be restricted to IP address or MAC address.
1534 The format of the list is:
1535 type_attribute = [s|d|x|b|i|m]
1536 access_attribute = [a|r|o|c]
1537 attributes = type_attribute[access_attribute]
1538 entry = variable_name[:attributes]
1541 The type attributes are:
1542 s - String (default)
1545 b - Boolean ([1yYtT|0nNfF])
1549 The access attributes are:
1555 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1556 Define this to a list (string) to define the ".flags"
1557 environment variable in the default or embedded environment.
1559 - CONFIG_ENV_FLAGS_LIST_STATIC
1560 Define this to a list (string) to define validation that
1561 should be done if an entry is not found in the ".flags"
1562 environment variable. To override a setting in the static
1563 list, simply add an entry for the same variable name to the
1566 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
1567 regular expression. This allows multiple variables to define the same
1568 flags without explicitly listing them for each variable.
1570 The following definitions that deal with the placement and management
1571 of environment data (variable area); in general, we support the
1572 following configurations:
1574 - CONFIG_BUILD_ENVCRC:
1576 Builds up envcrc with the target environment so that external utils
1577 may easily extract it and embed it in final U-Boot images.
1579 BE CAREFUL! The first access to the environment happens quite early
1580 in U-Boot initialization (when we try to get the setting of for the
1581 console baudrate). You *MUST* have mapped your NVRAM area then, or
1584 Please note that even with NVRAM we still use a copy of the
1585 environment in RAM: we could work on NVRAM directly, but we want to
1586 keep settings there always unmodified except somebody uses "saveenv"
1587 to save the current settings.
1589 BE CAREFUL! For some special cases, the local device can not use
1590 "saveenv" command. For example, the local device will get the
1591 environment stored in a remote NOR flash by SRIO or PCIE link,
1592 but it can not erase, write this NOR flash by SRIO or PCIE interface.
1594 - CONFIG_NAND_ENV_DST
1596 Defines address in RAM to which the nand_spl code should copy the
1597 environment. If redundant environment is used, it will be copied to
1598 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
1600 Please note that the environment is read-only until the monitor
1601 has been relocated to RAM and a RAM copy of the environment has been
1602 created; also, when using EEPROM you will have to use env_get_f()
1603 until then to read environment variables.
1605 The environment is protected by a CRC32 checksum. Before the monitor
1606 is relocated into RAM, as a result of a bad CRC you will be working
1607 with the compiled-in default environment - *silently*!!! [This is
1608 necessary, because the first environment variable we need is the
1609 "baudrate" setting for the console - if we have a bad CRC, we don't
1610 have any device yet where we could complain.]
1612 Note: once the monitor has been relocated, then it will complain if
1613 the default environment is used; a new CRC is computed as soon as you
1614 use the "saveenv" command to store a valid environment.
1616 - CONFIG_SYS_FAULT_MII_ADDR:
1617 MII address of the PHY to check for the Ethernet link state.
1619 - CONFIG_DISPLAY_BOARDINFO
1620 Display information about the board that U-Boot is running on
1621 when U-Boot starts up. The board function checkboard() is called
1624 - CONFIG_DISPLAY_BOARDINFO_LATE
1625 Similar to the previous option, but display this information
1626 later, once stdio is running and output goes to the LCD, if
1629 Low Level (hardware related) configuration options:
1630 ---------------------------------------------------
1632 - CONFIG_SYS_CACHELINE_SIZE:
1633 Cache Line Size of the CPU.
1635 - CONFIG_SYS_CCSRBAR_DEFAULT:
1636 Default (power-on reset) physical address of CCSR on Freescale
1640 Virtual address of CCSR. On a 32-bit build, this is typically
1641 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
1643 - CFG_SYS_CCSRBAR_PHYS:
1644 Physical address of CCSR. CCSR can be relocated to a new
1645 physical address, if desired. In this case, this macro should
1646 be set to that address. Otherwise, it should be set to the
1647 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
1648 is typically relocated on 36-bit builds. It is recommended
1649 that this macro be defined via the _HIGH and _LOW macros:
1651 #define CFG_SYS_CCSRBAR_PHYS ((CFG_SYS_CCSRBAR_PHYS_HIGH
1652 * 1ull) << 32 | CFG_SYS_CCSRBAR_PHYS_LOW)
1654 - CFG_SYS_CCSRBAR_PHYS_HIGH:
1655 Bits 33-36 of CFG_SYS_CCSRBAR_PHYS. This value is typically
1656 either 0 (32-bit build) or 0xF (36-bit build). This macro is
1657 used in assembly code, so it must not contain typecasts or
1658 integer size suffixes (e.g. "ULL").
1660 - CFG_SYS_CCSRBAR_PHYS_LOW:
1661 Lower 32-bits of CFG_SYS_CCSRBAR_PHYS. This macro is
1662 used in assembly code, so it must not contain typecasts or
1663 integer size suffixes (e.g. "ULL").
1665 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
1666 DO NOT CHANGE unless you know exactly what you're
1667 doing! (11-4) [MPC8xx systems only]
1669 - CFG_SYS_INIT_RAM_ADDR:
1671 Start address of memory area that can be used for
1672 initial data and stack; please note that this must be
1673 writable memory that is working WITHOUT special
1674 initialization, i. e. you CANNOT use normal RAM which
1675 will become available only after programming the
1676 memory controller and running certain initialization
1679 U-Boot uses the following memory types:
1680 - MPC8xx: IMMR (internal memory of the CPU)
1682 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
1684 - CONFIG_SYS_OR_TIMING_SDRAM:
1687 - CONFIG_SYS_SRIOn_MEM_VIRT:
1688 Virtual Address of SRIO port 'n' memory region
1690 - CONFIG_SYS_SRIOn_MEM_PHYxS:
1691 Physical Address of SRIO port 'n' memory region
1693 - CONFIG_SYS_SRIOn_MEM_SIZE:
1694 Size of SRIO port 'n' memory region
1696 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
1697 Defined to tell the NAND controller that the NAND chip is using
1699 Not all NAND drivers use this symbol.
1700 Example of drivers that use it:
1701 - drivers/mtd/nand/raw/ndfc.c
1702 - drivers/mtd/nand/raw/mxc_nand.c
1704 - CONFIG_SYS_NDFC_EBC0_CFG
1705 Sets the EBC0_CFG register for the NDFC. If not defined
1706 a default value will be used.
1709 Get DDR timing information from an I2C EEPROM. Common
1710 with pluggable memory modules such as SODIMMs
1713 I2C address of the SPD EEPROM
1715 - CONFIG_SYS_SPD_BUS_NUM
1716 If SPD EEPROM is on an I2C bus other than the first
1717 one, specify here. Note that the value must resolve
1718 to something your driver can deal with.
1720 - CONFIG_FSL_DDR_INTERACTIVE
1721 Enable interactive DDR debugging. See doc/README.fsl-ddr.
1723 - CONFIG_FSL_DDR_SYNC_REFRESH
1724 Enable sync of refresh for multiple controllers.
1726 - CONFIG_FSL_DDR_BIST
1727 Enable built-in memory test for Freescale DDR controllers.
1730 Enable RMII mode for all FECs.
1731 Note that this is a global option, we can't
1732 have one FEC in standard MII mode and another in RMII mode.
1734 - CONFIG_CRC32_VERIFY
1735 Add a verify option to the crc32 command.
1738 => crc32 -v <address> <count> <crc32>
1740 Where address/count indicate a memory area
1741 and crc32 is the correct crc32 which the
1745 Add the "loopw" memory command. This only takes effect if
1746 the memory commands are activated globally (CONFIG_CMD_MEMORY).
1748 - CONFIG_CMD_MX_CYCLIC
1749 Add the "mdc" and "mwc" memory commands. These are cyclic
1754 This command will print 4 bytes (10,11,12,13) each 500 ms.
1756 => mwc.l 100 12345678 10
1757 This command will write 12345678 to address 100 all 10 ms.
1759 This only takes effect if the memory commands are activated
1760 globally (CONFIG_CMD_MEMORY).
1763 Set when the currently-running compilation is for an artifact
1764 that will end up in the SPL (as opposed to the TPL or U-Boot
1765 proper). Code that needs stage-specific behavior should check
1769 Set when the currently-running compilation is for an artifact
1770 that will end up in the TPL (as opposed to the SPL or U-Boot
1771 proper). Code that needs stage-specific behavior should check
1774 - CONFIG_ARCH_MAP_SYSMEM
1775 Generally U-Boot (and in particular the md command) uses
1776 effective address. It is therefore not necessary to regard
1777 U-Boot address as virtual addresses that need to be translated
1778 to physical addresses. However, sandbox requires this, since
1779 it maintains its own little RAM buffer which contains all
1780 addressable memory. This option causes some memory accesses
1781 to be mapped through map_sysmem() / unmap_sysmem().
1783 - CONFIG_X86_RESET_VECTOR
1784 If defined, the x86 reset vector code is included. This is not
1785 needed when U-Boot is running from Coreboot.
1787 Freescale QE/FMAN Firmware Support:
1788 -----------------------------------
1790 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
1791 loading of "firmware", which is encoded in the QE firmware binary format.
1792 This firmware often needs to be loaded during U-Boot booting, so macros
1793 are used to identify the storage device (NOR flash, SPI, etc) and the address
1796 - CONFIG_SYS_FMAN_FW_ADDR
1797 The address in the storage device where the FMAN microcode is located. The
1798 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1801 - CONFIG_SYS_QE_FW_ADDR
1802 The address in the storage device where the QE microcode is located. The
1803 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1806 - CONFIG_SYS_QE_FMAN_FW_LENGTH
1807 The maximum possible size of the firmware. The firmware binary format
1808 has a field that specifies the actual size of the firmware, but it
1809 might not be possible to read any part of the firmware unless some
1810 local storage is allocated to hold the entire firmware first.
1812 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
1813 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
1814 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
1815 virtual address in NOR flash.
1817 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
1818 Specifies that QE/FMAN firmware is located in NAND flash.
1819 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
1821 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
1822 Specifies that QE/FMAN firmware is located on the primary SD/MMC
1823 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
1825 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
1826 Specifies that QE/FMAN firmware is located in the remote (master)
1827 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
1828 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
1829 window->master inbound window->master LAW->the ucode address in
1830 master's memory space.
1832 Freescale Layerscape Management Complex Firmware Support:
1833 ---------------------------------------------------------
1834 The Freescale Layerscape Management Complex (MC) supports the loading of
1836 This firmware often needs to be loaded during U-Boot booting, so macros
1837 are used to identify the storage device (NOR flash, SPI, etc) and the address
1840 - CONFIG_FSL_MC_ENET
1841 Enable the MC driver for Layerscape SoCs.
1843 Freescale Layerscape Debug Server Support:
1844 -------------------------------------------
1845 The Freescale Layerscape Debug Server Support supports the loading of
1846 "Debug Server firmware" and triggering SP boot-rom.
1847 This firmware often needs to be loaded during U-Boot booting.
1849 - CONFIG_SYS_MC_RSV_MEM_ALIGN
1850 Define alignment of reserved memory MC requires
1855 In order to achieve reproducible builds, timestamps used in the U-Boot build
1856 process have to be set to a fixed value.
1858 This is done using the SOURCE_DATE_EPOCH environment variable.
1859 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
1860 option for U-Boot or an environment variable in U-Boot.
1862 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
1864 Building the Software:
1865 ======================
1867 Building U-Boot has been tested in several native build environments
1868 and in many different cross environments. Of course we cannot support
1869 all possibly existing versions of cross development tools in all
1870 (potentially obsolete) versions. In case of tool chain problems we
1871 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
1872 which is extensively used to build and test U-Boot.
1874 If you are not using a native environment, it is assumed that you
1875 have GNU cross compiling tools available in your path. In this case,
1876 you must set the environment variable CROSS_COMPILE in your shell.
1877 Note that no changes to the Makefile or any other source files are
1878 necessary. For example using the ELDK on a 4xx CPU, please enter:
1880 $ CROSS_COMPILE=ppc_4xx-
1881 $ export CROSS_COMPILE
1883 U-Boot is intended to be simple to build. After installing the
1884 sources you must configure U-Boot for one specific board type. This
1889 where "NAME_defconfig" is the name of one of the existing configu-
1890 rations; see configs/*_defconfig for supported names.
1892 Note: for some boards special configuration names may exist; check if
1893 additional information is available from the board vendor; for
1894 instance, the TQM823L systems are available without (standard)
1895 or with LCD support. You can select such additional "features"
1896 when choosing the configuration, i. e.
1898 make TQM823L_defconfig
1899 - will configure for a plain TQM823L, i. e. no LCD support
1901 make TQM823L_LCD_defconfig
1902 - will configure for a TQM823L with U-Boot console on LCD
1907 Finally, type "make all", and you should get some working U-Boot
1908 images ready for download to / installation on your system:
1910 - "u-boot.bin" is a raw binary image
1911 - "u-boot" is an image in ELF binary format
1912 - "u-boot.srec" is in Motorola S-Record format
1914 By default the build is performed locally and the objects are saved
1915 in the source directory. One of the two methods can be used to change
1916 this behavior and build U-Boot to some external directory:
1918 1. Add O= to the make command line invocations:
1920 make O=/tmp/build distclean
1921 make O=/tmp/build NAME_defconfig
1922 make O=/tmp/build all
1924 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
1926 export KBUILD_OUTPUT=/tmp/build
1931 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
1934 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
1935 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
1936 For example to treat all compiler warnings as errors:
1938 make KCFLAGS=-Werror
1940 Please be aware that the Makefiles assume you are using GNU make, so
1941 for instance on NetBSD you might need to use "gmake" instead of
1945 If the system board that you have is not listed, then you will need
1946 to port U-Boot to your hardware platform. To do this, follow these
1949 1. Create a new directory to hold your board specific code. Add any
1950 files you need. In your board directory, you will need at least
1951 the "Makefile" and a "<board>.c".
1952 2. Create a new configuration file "include/configs/<board>.h" for
1954 3. If you're porting U-Boot to a new CPU, then also create a new
1955 directory to hold your CPU specific code. Add any files you need.
1956 4. Run "make <board>_defconfig" with your new name.
1957 5. Type "make", and you should get a working "u-boot.srec" file
1958 to be installed on your target system.
1959 6. Debug and solve any problems that might arise.
1960 [Of course, this last step is much harder than it sounds.]
1963 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
1964 ==============================================================
1966 If you have modified U-Boot sources (for instance added a new board
1967 or support for new devices, a new CPU, etc.) you are expected to
1968 provide feedback to the other developers. The feedback normally takes
1969 the form of a "patch", i.e. a context diff against a certain (latest
1970 official or latest in the git repository) version of U-Boot sources.
1972 But before you submit such a patch, please verify that your modifi-
1973 cation did not break existing code. At least make sure that *ALL* of
1974 the supported boards compile WITHOUT ANY compiler warnings. To do so,
1975 just run the buildman script (tools/buildman/buildman), which will
1976 configure and build U-Boot for ALL supported system. Be warned, this
1977 will take a while. Please see the buildman README, or run 'buildman -H'
1981 See also "U-Boot Porting Guide" below.
1984 Monitor Commands - Overview:
1985 ============================
1987 go - start application at address 'addr'
1988 run - run commands in an environment variable
1989 bootm - boot application image from memory
1990 bootp - boot image via network using BootP/TFTP protocol
1991 bootz - boot zImage from memory
1992 tftpboot- boot image via network using TFTP protocol
1993 and env variables "ipaddr" and "serverip"
1994 (and eventually "gatewayip")
1995 tftpput - upload a file via network using TFTP protocol
1996 rarpboot- boot image via network using RARP/TFTP protocol
1997 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
1998 loads - load S-Record file over serial line
1999 loadb - load binary file over serial line (kermit mode)
2000 loadm - load binary blob from source address to destination address
2002 mm - memory modify (auto-incrementing)
2003 nm - memory modify (constant address)
2004 mw - memory write (fill)
2007 cmp - memory compare
2008 crc32 - checksum calculation
2009 i2c - I2C sub-system
2010 sspi - SPI utility commands
2011 base - print or set address offset
2012 printenv- print environment variables
2013 pwm - control pwm channels
2014 setenv - set environment variables
2015 saveenv - save environment variables to persistent storage
2016 protect - enable or disable FLASH write protection
2017 erase - erase FLASH memory
2018 flinfo - print FLASH memory information
2019 nand - NAND memory operations (see doc/README.nand)
2020 bdinfo - print Board Info structure
2021 iminfo - print header information for application image
2022 coninfo - print console devices and informations
2023 ide - IDE sub-system
2024 loop - infinite loop on address range
2025 loopw - infinite write loop on address range
2026 mtest - simple RAM test
2027 icache - enable or disable instruction cache
2028 dcache - enable or disable data cache
2029 reset - Perform RESET of the CPU
2030 echo - echo args to console
2031 version - print monitor version
2032 help - print online help
2033 ? - alias for 'help'
2036 Monitor Commands - Detailed Description:
2037 ========================================
2041 For now: just type "help <command>".
2044 Note for Redundant Ethernet Interfaces:
2045 =======================================
2047 Some boards come with redundant Ethernet interfaces; U-Boot supports
2048 such configurations and is capable of automatic selection of a
2049 "working" interface when needed. MAC assignment works as follows:
2051 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
2052 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
2053 "eth1addr" (=>eth1), "eth2addr", ...
2055 If the network interface stores some valid MAC address (for instance
2056 in SROM), this is used as default address if there is NO correspon-
2057 ding setting in the environment; if the corresponding environment
2058 variable is set, this overrides the settings in the card; that means:
2060 o If the SROM has a valid MAC address, and there is no address in the
2061 environment, the SROM's address is used.
2063 o If there is no valid address in the SROM, and a definition in the
2064 environment exists, then the value from the environment variable is
2067 o If both the SROM and the environment contain a MAC address, and
2068 both addresses are the same, this MAC address is used.
2070 o If both the SROM and the environment contain a MAC address, and the
2071 addresses differ, the value from the environment is used and a
2074 o If neither SROM nor the environment contain a MAC address, an error
2075 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
2076 a random, locally-assigned MAC is used.
2078 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
2079 will be programmed into hardware as part of the initialization process. This
2080 may be skipped by setting the appropriate 'ethmacskip' environment variable.
2081 The naming convention is as follows:
2082 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
2087 U-Boot is capable of booting (and performing other auxiliary operations on)
2088 images in two formats:
2090 New uImage format (FIT)
2091 -----------------------
2093 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
2094 to Flattened Device Tree). It allows the use of images with multiple
2095 components (several kernels, ramdisks, etc.), with contents protected by
2096 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
2102 Old image format is based on binary files which can be basically anything,
2103 preceded by a special header; see the definitions in include/image.h for
2104 details; basically, the header defines the following image properties:
2106 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
2107 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
2108 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
2109 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
2110 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
2111 IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
2112 Currently supported: ARM, Intel x86, MIPS, Nios II, PowerPC).
2113 * Compression Type (uncompressed, gzip, bzip2)
2119 The header is marked by a special Magic Number, and both the header
2120 and the data portions of the image are secured against corruption by
2127 Although U-Boot should support any OS or standalone application
2128 easily, the main focus has always been on Linux during the design of
2131 U-Boot includes many features that so far have been part of some
2132 special "boot loader" code within the Linux kernel. Also, any
2133 "initrd" images to be used are no longer part of one big Linux image;
2134 instead, kernel and "initrd" are separate images. This implementation
2135 serves several purposes:
2137 - the same features can be used for other OS or standalone
2138 applications (for instance: using compressed images to reduce the
2139 Flash memory footprint)
2141 - it becomes much easier to port new Linux kernel versions because
2142 lots of low-level, hardware dependent stuff are done by U-Boot
2144 - the same Linux kernel image can now be used with different "initrd"
2145 images; of course this also means that different kernel images can
2146 be run with the same "initrd". This makes testing easier (you don't
2147 have to build a new "zImage.initrd" Linux image when you just
2148 change a file in your "initrd"). Also, a field-upgrade of the
2149 software is easier now.
2155 Porting Linux to U-Boot based systems:
2156 ---------------------------------------
2158 U-Boot cannot save you from doing all the necessary modifications to
2159 configure the Linux device drivers for use with your target hardware
2160 (no, we don't intend to provide a full virtual machine interface to
2163 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
2165 Just make sure your machine specific header file (for instance
2166 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2167 Information structure as we define in include/asm-<arch>/u-boot.h,
2168 and make sure that your definition of IMAP_ADDR uses the same value
2169 as your U-Boot configuration in CONFIG_SYS_IMMR.
2171 Note that U-Boot now has a driver model, a unified model for drivers.
2172 If you are adding a new driver, plumb it into driver model. If there
2173 is no uclass available, you are encouraged to create one. See
2177 Configuring the Linux kernel:
2178 -----------------------------
2180 No specific requirements for U-Boot. Make sure you have some root
2181 device (initial ramdisk, NFS) for your target system.
2184 Building a Linux Image:
2185 -----------------------
2187 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2188 not used. If you use recent kernel source, a new build target
2189 "uImage" will exist which automatically builds an image usable by
2190 U-Boot. Most older kernels also have support for a "pImage" target,
2191 which was introduced for our predecessor project PPCBoot and uses a
2192 100% compatible format.
2196 make TQM850L_defconfig
2201 The "uImage" build target uses a special tool (in 'tools/mkimage') to
2202 encapsulate a compressed Linux kernel image with header information,
2203 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2205 * build a standard "vmlinux" kernel image (in ELF binary format):
2207 * convert the kernel into a raw binary image:
2209 ${CROSS_COMPILE}-objcopy -O binary \
2210 -R .note -R .comment \
2211 -S vmlinux linux.bin
2213 * compress the binary image:
2217 * package compressed binary image for U-Boot:
2219 mkimage -A ppc -O linux -T kernel -C gzip \
2220 -a 0 -e 0 -n "Linux Kernel Image" \
2221 -d linux.bin.gz uImage
2224 The "mkimage" tool can also be used to create ramdisk images for use
2225 with U-Boot, either separated from the Linux kernel image, or
2226 combined into one file. "mkimage" encapsulates the images with a 64
2227 byte header containing information about target architecture,
2228 operating system, image type, compression method, entry points, time
2229 stamp, CRC32 checksums, etc.
2231 "mkimage" can be called in two ways: to verify existing images and
2232 print the header information, or to build new images.
2234 In the first form (with "-l" option) mkimage lists the information
2235 contained in the header of an existing U-Boot image; this includes
2236 checksum verification:
2238 tools/mkimage -l image
2239 -l ==> list image header information
2241 The second form (with "-d" option) is used to build a U-Boot image
2242 from a "data file" which is used as image payload:
2244 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
2245 -n name -d data_file image
2246 -A ==> set architecture to 'arch'
2247 -O ==> set operating system to 'os'
2248 -T ==> set image type to 'type'
2249 -C ==> set compression type 'comp'
2250 -a ==> set load address to 'addr' (hex)
2251 -e ==> set entry point to 'ep' (hex)
2252 -n ==> set image name to 'name'
2253 -d ==> use image data from 'datafile'
2255 Right now, all Linux kernels for PowerPC systems use the same load
2256 address (0x00000000), but the entry point address depends on the
2259 - 2.2.x kernels have the entry point at 0x0000000C,
2260 - 2.3.x and later kernels have the entry point at 0x00000000.
2262 So a typical call to build a U-Boot image would read:
2264 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2265 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
2266 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
2267 > examples/uImage.TQM850L
2268 Image Name: 2.4.4 kernel for TQM850L
2269 Created: Wed Jul 19 02:34:59 2000
2270 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2271 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2272 Load Address: 0x00000000
2273 Entry Point: 0x00000000
2275 To verify the contents of the image (or check for corruption):
2277 -> tools/mkimage -l examples/uImage.TQM850L
2278 Image Name: 2.4.4 kernel for TQM850L
2279 Created: Wed Jul 19 02:34:59 2000
2280 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2281 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2282 Load Address: 0x00000000
2283 Entry Point: 0x00000000
2285 NOTE: for embedded systems where boot time is critical you can trade
2286 speed for memory and install an UNCOMPRESSED image instead: this
2287 needs more space in Flash, but boots much faster since it does not
2288 need to be uncompressed:
2290 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
2291 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2292 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
2293 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
2294 > examples/uImage.TQM850L-uncompressed
2295 Image Name: 2.4.4 kernel for TQM850L
2296 Created: Wed Jul 19 02:34:59 2000
2297 Image Type: PowerPC Linux Kernel Image (uncompressed)
2298 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
2299 Load Address: 0x00000000
2300 Entry Point: 0x00000000
2303 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
2304 when your kernel is intended to use an initial ramdisk:
2306 -> tools/mkimage -n 'Simple Ramdisk Image' \
2307 > -A ppc -O linux -T ramdisk -C gzip \
2308 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
2309 Image Name: Simple Ramdisk Image
2310 Created: Wed Jan 12 14:01:50 2000
2311 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2312 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
2313 Load Address: 0x00000000
2314 Entry Point: 0x00000000
2316 The "dumpimage" tool can be used to disassemble or list the contents of images
2317 built by mkimage. See dumpimage's help output (-h) for details.
2319 Installing a Linux Image:
2320 -------------------------
2322 To downloading a U-Boot image over the serial (console) interface,
2323 you must convert the image to S-Record format:
2325 objcopy -I binary -O srec examples/image examples/image.srec
2327 The 'objcopy' does not understand the information in the U-Boot
2328 image header, so the resulting S-Record file will be relative to
2329 address 0x00000000. To load it to a given address, you need to
2330 specify the target address as 'offset' parameter with the 'loads'
2333 Example: install the image to address 0x40100000 (which on the
2334 TQM8xxL is in the first Flash bank):
2336 => erase 40100000 401FFFFF
2342 ## Ready for S-Record download ...
2343 ~>examples/image.srec
2344 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
2346 15989 15990 15991 15992
2347 [file transfer complete]
2349 ## Start Addr = 0x00000000
2352 You can check the success of the download using the 'iminfo' command;
2353 this includes a checksum verification so you can be sure no data
2354 corruption happened:
2358 ## Checking Image at 40100000 ...
2359 Image Name: 2.2.13 for initrd on TQM850L
2360 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2361 Data Size: 335725 Bytes = 327 kB = 0 MB
2362 Load Address: 00000000
2363 Entry Point: 0000000c
2364 Verifying Checksum ... OK
2370 The "bootm" command is used to boot an application that is stored in
2371 memory (RAM or Flash). In case of a Linux kernel image, the contents
2372 of the "bootargs" environment variable is passed to the kernel as
2373 parameters. You can check and modify this variable using the
2374 "printenv" and "setenv" commands:
2377 => printenv bootargs
2378 bootargs=root=/dev/ram
2380 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2382 => printenv bootargs
2383 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2386 ## Booting Linux kernel at 40020000 ...
2387 Image Name: 2.2.13 for NFS on TQM850L
2388 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2389 Data Size: 381681 Bytes = 372 kB = 0 MB
2390 Load Address: 00000000
2391 Entry Point: 0000000c
2392 Verifying Checksum ... OK
2393 Uncompressing Kernel Image ... OK
2394 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
2395 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2396 time_init: decrementer frequency = 187500000/60
2397 Calibrating delay loop... 49.77 BogoMIPS
2398 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
2401 If you want to boot a Linux kernel with initial RAM disk, you pass
2402 the memory addresses of both the kernel and the initrd image (PPBCOOT
2403 format!) to the "bootm" command:
2405 => imi 40100000 40200000
2407 ## Checking Image at 40100000 ...
2408 Image Name: 2.2.13 for initrd on TQM850L
2409 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2410 Data Size: 335725 Bytes = 327 kB = 0 MB
2411 Load Address: 00000000
2412 Entry Point: 0000000c
2413 Verifying Checksum ... OK
2415 ## Checking Image at 40200000 ...
2416 Image Name: Simple Ramdisk Image
2417 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2418 Data Size: 566530 Bytes = 553 kB = 0 MB
2419 Load Address: 00000000
2420 Entry Point: 00000000
2421 Verifying Checksum ... OK
2423 => bootm 40100000 40200000
2424 ## Booting Linux kernel at 40100000 ...
2425 Image Name: 2.2.13 for initrd on TQM850L
2426 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2427 Data Size: 335725 Bytes = 327 kB = 0 MB
2428 Load Address: 00000000
2429 Entry Point: 0000000c
2430 Verifying Checksum ... OK
2431 Uncompressing Kernel Image ... OK
2432 ## Loading RAMDisk Image at 40200000 ...
2433 Image Name: Simple Ramdisk Image
2434 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2435 Data Size: 566530 Bytes = 553 kB = 0 MB
2436 Load Address: 00000000
2437 Entry Point: 00000000
2438 Verifying Checksum ... OK
2439 Loading Ramdisk ... OK
2440 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
2441 Boot arguments: root=/dev/ram
2442 time_init: decrementer frequency = 187500000/60
2443 Calibrating delay loop... 49.77 BogoMIPS
2445 RAMDISK: Compressed image found at block 0
2446 VFS: Mounted root (ext2 filesystem).
2450 Boot Linux and pass a flat device tree:
2453 First, U-Boot must be compiled with the appropriate defines. See the section
2454 titled "Linux Kernel Interface" above for a more in depth explanation. The
2455 following is an example of how to start a kernel and pass an updated
2461 oft=oftrees/mpc8540ads.dtb
2462 => tftp $oftaddr $oft
2463 Speed: 1000, full duplex
2465 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
2466 Filename 'oftrees/mpc8540ads.dtb'.
2467 Load address: 0x300000
2470 Bytes transferred = 4106 (100a hex)
2471 => tftp $loadaddr $bootfile
2472 Speed: 1000, full duplex
2474 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
2476 Load address: 0x200000
2477 Loading:############
2479 Bytes transferred = 1029407 (fb51f hex)
2484 => bootm $loadaddr - $oftaddr
2485 ## Booting image at 00200000 ...
2486 Image Name: Linux-2.6.17-dirty
2487 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2488 Data Size: 1029343 Bytes = 1005.2 kB
2489 Load Address: 00000000
2490 Entry Point: 00000000
2491 Verifying Checksum ... OK
2492 Uncompressing Kernel Image ... OK
2493 Booting using flat device tree at 0x300000
2494 Using MPC85xx ADS machine description
2495 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
2499 More About U-Boot Image Types:
2500 ------------------------------
2502 U-Boot supports the following image types:
2504 "Standalone Programs" are directly runnable in the environment
2505 provided by U-Boot; it is expected that (if they behave
2506 well) you can continue to work in U-Boot after return from
2507 the Standalone Program.
2508 "OS Kernel Images" are usually images of some Embedded OS which
2509 will take over control completely. Usually these programs
2510 will install their own set of exception handlers, device
2511 drivers, set up the MMU, etc. - this means, that you cannot
2512 expect to re-enter U-Boot except by resetting the CPU.
2513 "RAMDisk Images" are more or less just data blocks, and their
2514 parameters (address, size) are passed to an OS kernel that is
2516 "Multi-File Images" contain several images, typically an OS
2517 (Linux) kernel image and one or more data images like
2518 RAMDisks. This construct is useful for instance when you want
2519 to boot over the network using BOOTP etc., where the boot
2520 server provides just a single image file, but you want to get
2521 for instance an OS kernel and a RAMDisk image.
2523 "Multi-File Images" start with a list of image sizes, each
2524 image size (in bytes) specified by an "uint32_t" in network
2525 byte order. This list is terminated by an "(uint32_t)0".
2526 Immediately after the terminating 0 follow the images, one by
2527 one, all aligned on "uint32_t" boundaries (size rounded up to
2528 a multiple of 4 bytes).
2530 "Firmware Images" are binary images containing firmware (like
2531 U-Boot or FPGA images) which usually will be programmed to
2534 "Script files" are command sequences that will be executed by
2535 U-Boot's command interpreter; this feature is especially
2536 useful when you configure U-Boot to use a real shell (hush)
2537 as command interpreter.
2539 Booting the Linux zImage:
2540 -------------------------
2542 On some platforms, it's possible to boot Linux zImage. This is done
2543 using the "bootz" command. The syntax of "bootz" command is the same
2544 as the syntax of "bootm" command.
2546 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
2547 kernel with raw initrd images. The syntax is slightly different, the
2548 address of the initrd must be augmented by it's size, in the following
2549 format: "<initrd addres>:<initrd size>".
2555 One of the features of U-Boot is that you can dynamically load and
2556 run "standalone" applications, which can use some resources of
2557 U-Boot like console I/O functions or interrupt services.
2559 Two simple examples are included with the sources:
2564 'examples/hello_world.c' contains a small "Hello World" Demo
2565 application; it is automatically compiled when you build U-Boot.
2566 It's configured to run at address 0x00040004, so you can play with it
2570 ## Ready for S-Record download ...
2571 ~>examples/hello_world.srec
2572 1 2 3 4 5 6 7 8 9 10 11 ...
2573 [file transfer complete]
2575 ## Start Addr = 0x00040004
2577 => go 40004 Hello World! This is a test.
2578 ## Starting application at 0x00040004 ...
2589 Hit any key to exit ...
2591 ## Application terminated, rc = 0x0
2593 Another example, which demonstrates how to register a CPM interrupt
2594 handler with the U-Boot code, can be found in 'examples/timer.c'.
2595 Here, a CPM timer is set up to generate an interrupt every second.
2596 The interrupt service routine is trivial, just printing a '.'
2597 character, but this is just a demo program. The application can be
2598 controlled by the following keys:
2600 ? - print current values og the CPM Timer registers
2601 b - enable interrupts and start timer
2602 e - stop timer and disable interrupts
2603 q - quit application
2606 ## Ready for S-Record download ...
2607 ~>examples/timer.srec
2608 1 2 3 4 5 6 7 8 9 10 11 ...
2609 [file transfer complete]
2611 ## Start Addr = 0x00040004
2614 ## Starting application at 0x00040004 ...
2617 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
2620 [q, b, e, ?] Set interval 1000000 us
2623 [q, b, e, ?] ........
2624 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
2627 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
2630 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
2633 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
2635 [q, b, e, ?] ...Stopping timer
2637 [q, b, e, ?] ## Application terminated, rc = 0x0
2643 Over time, many people have reported problems when trying to use the
2644 "minicom" terminal emulation program for serial download. I (wd)
2645 consider minicom to be broken, and recommend not to use it. Under
2646 Unix, I recommend to use C-Kermit for general purpose use (and
2647 especially for kermit binary protocol download ("loadb" command), and
2648 use "cu" for S-Record download ("loads" command). See
2649 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
2650 for help with kermit.
2653 Nevertheless, if you absolutely want to use it try adding this
2654 configuration to your "File transfer protocols" section:
2656 Name Program Name U/D FullScr IO-Red. Multi
2657 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
2658 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
2664 Starting at version 0.9.2, U-Boot supports NetBSD both as host
2665 (build U-Boot) and target system (boots NetBSD/mpc8xx).
2667 Building requires a cross environment; it is known to work on
2668 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
2669 need gmake since the Makefiles are not compatible with BSD make).
2670 Note that the cross-powerpc package does not install include files;
2671 attempting to build U-Boot will fail because <machine/ansi.h> is
2672 missing. This file has to be installed and patched manually:
2674 # cd /usr/pkg/cross/powerpc-netbsd/include
2676 # ln -s powerpc machine
2677 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
2678 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
2680 Native builds *don't* work due to incompatibilities between native
2681 and U-Boot include files.
2683 Booting assumes that (the first part of) the image booted is a
2684 stage-2 loader which in turn loads and then invokes the kernel
2685 proper. Loader sources will eventually appear in the NetBSD source
2686 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
2687 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
2690 Implementation Internals:
2691 =========================
2693 The following is not intended to be a complete description of every
2694 implementation detail. However, it should help to understand the
2695 inner workings of U-Boot and make it easier to port it to custom
2699 Initial Stack, Global Data:
2700 ---------------------------
2702 The implementation of U-Boot is complicated by the fact that U-Boot
2703 starts running out of ROM (flash memory), usually without access to
2704 system RAM (because the memory controller is not initialized yet).
2705 This means that we don't have writable Data or BSS segments, and BSS
2706 is not initialized as zero. To be able to get a C environment working
2707 at all, we have to allocate at least a minimal stack. Implementation
2708 options for this are defined and restricted by the CPU used: Some CPU
2709 models provide on-chip memory (like the IMMR area on MPC8xx and
2710 MPC826x processors), on others (parts of) the data cache can be
2711 locked as (mis-) used as memory, etc.
2713 Chris Hallinan posted a good summary of these issues to the
2714 U-Boot mailing list:
2716 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
2717 From: "Chris Hallinan" <clh@net1plus.com>
2718 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
2721 Correct me if I'm wrong, folks, but the way I understand it
2722 is this: Using DCACHE as initial RAM for Stack, etc, does not
2723 require any physical RAM backing up the cache. The cleverness
2724 is that the cache is being used as a temporary supply of
2725 necessary storage before the SDRAM controller is setup. It's
2726 beyond the scope of this list to explain the details, but you
2727 can see how this works by studying the cache architecture and
2728 operation in the architecture and processor-specific manuals.
2730 OCM is On Chip Memory, which I believe the 405GP has 4K. It
2731 is another option for the system designer to use as an
2732 initial stack/RAM area prior to SDRAM being available. Either
2733 option should work for you. Using CS 4 should be fine if your
2734 board designers haven't used it for something that would
2735 cause you grief during the initial boot! It is frequently not
2738 CFG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
2739 with your processor/board/system design. The default value
2740 you will find in any recent u-boot distribution in
2741 walnut.h should work for you. I'd set it to a value larger
2742 than your SDRAM module. If you have a 64MB SDRAM module, set
2743 it above 400_0000. Just make sure your board has no resources
2744 that are supposed to respond to that address! That code in
2745 start.S has been around a while and should work as is when
2746 you get the config right.
2751 It is essential to remember this, since it has some impact on the C
2752 code for the initialization procedures:
2754 * Initialized global data (data segment) is read-only. Do not attempt
2757 * Do not use any uninitialized global data (or implicitly initialized
2758 as zero data - BSS segment) at all - this is undefined, initiali-
2759 zation is performed later (when relocating to RAM).
2761 * Stack space is very limited. Avoid big data buffers or things like
2764 Having only the stack as writable memory limits means we cannot use
2765 normal global data to share information between the code. But it
2766 turned out that the implementation of U-Boot can be greatly
2767 simplified by making a global data structure (gd_t) available to all
2768 functions. We could pass a pointer to this data as argument to _all_
2769 functions, but this would bloat the code. Instead we use a feature of
2770 the GCC compiler (Global Register Variables) to share the data: we
2771 place a pointer (gd) to the global data into a register which we
2772 reserve for this purpose.
2774 When choosing a register for such a purpose we are restricted by the
2775 relevant (E)ABI specifications for the current architecture, and by
2776 GCC's implementation.
2778 For PowerPC, the following registers have specific use:
2780 R2: reserved for system use
2781 R3-R4: parameter passing and return values
2782 R5-R10: parameter passing
2783 R13: small data area pointer
2787 (U-Boot also uses R12 as internal GOT pointer. r12
2788 is a volatile register so r12 needs to be reset when
2789 going back and forth between asm and C)
2791 ==> U-Boot will use R2 to hold a pointer to the global data
2793 Note: on PPC, we could use a static initializer (since the
2794 address of the global data structure is known at compile time),
2795 but it turned out that reserving a register results in somewhat
2796 smaller code - although the code savings are not that big (on
2797 average for all boards 752 bytes for the whole U-Boot image,
2798 624 text + 127 data).
2800 On ARM, the following registers are used:
2802 R0: function argument word/integer result
2803 R1-R3: function argument word
2804 R9: platform specific
2805 R10: stack limit (used only if stack checking is enabled)
2806 R11: argument (frame) pointer
2807 R12: temporary workspace
2810 R15: program counter
2812 ==> U-Boot will use R9 to hold a pointer to the global data
2814 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
2816 On Nios II, the ABI is documented here:
2817 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
2819 ==> U-Boot will use gp to hold a pointer to the global data
2821 Note: on Nios II, we give "-G0" option to gcc and don't use gp
2822 to access small data sections, so gp is free.
2824 On RISC-V, the following registers are used:
2826 x0: hard-wired zero (zero)
2827 x1: return address (ra)
2828 x2: stack pointer (sp)
2829 x3: global pointer (gp)
2830 x4: thread pointer (tp)
2831 x5: link register (t0)
2832 x8: frame pointer (fp)
2833 x10-x11: arguments/return values (a0-1)
2834 x12-x17: arguments (a2-7)
2835 x28-31: temporaries (t3-6)
2836 pc: program counter (pc)
2838 ==> U-Boot will use gp to hold a pointer to the global data
2843 U-Boot runs in system state and uses physical addresses, i.e. the
2844 MMU is not used either for address mapping nor for memory protection.
2846 The available memory is mapped to fixed addresses using the memory
2847 controller. In this process, a contiguous block is formed for each
2848 memory type (Flash, SDRAM, SRAM), even when it consists of several
2849 physical memory banks.
2851 U-Boot is installed in the first 128 kB of the first Flash bank (on
2852 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
2853 booting and sizing and initializing DRAM, the code relocates itself
2854 to the upper end of DRAM. Immediately below the U-Boot code some
2855 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
2856 configuration setting]. Below that, a structure with global Board
2857 Info data is placed, followed by the stack (growing downward).
2859 Additionally, some exception handler code is copied to the low 8 kB
2860 of DRAM (0x00000000 ... 0x00001FFF).
2862 So a typical memory configuration with 16 MB of DRAM could look like
2865 0x0000 0000 Exception Vector code
2868 0x0000 2000 Free for Application Use
2874 0x00FB FF20 Monitor Stack (Growing downward)
2875 0x00FB FFAC Board Info Data and permanent copy of global data
2876 0x00FC 0000 Malloc Arena
2879 0x00FE 0000 RAM Copy of Monitor Code
2880 ... eventually: LCD or video framebuffer
2881 ... eventually: pRAM (Protected RAM - unchanged by reset)
2882 0x00FF FFFF [End of RAM]
2885 System Initialization:
2886 ----------------------
2888 In the reset configuration, U-Boot starts at the reset entry point
2889 (on most PowerPC systems at address 0x00000100). Because of the reset
2890 configuration for CS0# this is a mirror of the on board Flash memory.
2891 To be able to re-map memory U-Boot then jumps to its link address.
2892 To be able to implement the initialization code in C, a (small!)
2893 initial stack is set up in the internal Dual Ported RAM (in case CPUs
2894 which provide such a feature like), or in a locked part of the data
2895 cache. After that, U-Boot initializes the CPU core, the caches and
2898 Next, all (potentially) available memory banks are mapped using a
2899 preliminary mapping. For example, we put them on 512 MB boundaries
2900 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
2901 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
2902 programmed for SDRAM access. Using the temporary configuration, a
2903 simple memory test is run that determines the size of the SDRAM
2906 When there is more than one SDRAM bank, and the banks are of
2907 different size, the largest is mapped first. For equal size, the first
2908 bank (CS2#) is mapped first. The first mapping is always for address
2909 0x00000000, with any additional banks following immediately to create
2910 contiguous memory starting from 0.
2912 Then, the monitor installs itself at the upper end of the SDRAM area
2913 and allocates memory for use by malloc() and for the global Board
2914 Info data; also, the exception vector code is copied to the low RAM
2915 pages, and the final stack is set up.
2917 Only after this relocation will you have a "normal" C environment;
2918 until that you are restricted in several ways, mostly because you are
2919 running from ROM, and because the code will have to be relocated to a
2923 U-Boot Porting Guide:
2924 ----------------------
2926 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
2930 int main(int argc, char *argv[])
2932 sighandler_t no_more_time;
2934 signal(SIGALRM, no_more_time);
2935 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
2937 if (available_money > available_manpower) {
2938 Pay consultant to port U-Boot;
2942 Download latest U-Boot source;
2944 Subscribe to u-boot mailing list;
2947 email("Hi, I am new to U-Boot, how do I get started?");
2950 Read the README file in the top level directory;
2951 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
2952 Read applicable doc/README.*;
2953 Read the source, Luke;
2954 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
2957 if (available_money > toLocalCurrency ($2500))
2960 Add a lot of aggravation and time;
2962 if (a similar board exists) { /* hopefully... */
2963 cp -a board/<similar> board/<myboard>
2964 cp include/configs/<similar>.h include/configs/<myboard>.h
2966 Create your own board support subdirectory;
2967 Create your own board include/configs/<myboard>.h file;
2969 Edit new board/<myboard> files
2970 Edit new include/configs/<myboard>.h
2975 Add / modify source code;
2979 email("Hi, I am having problems...");
2981 Send patch file to the U-Boot email list;
2982 if (reasonable critiques)
2983 Incorporate improvements from email list code review;
2985 Defend code as written;
2991 void no_more_time (int sig)
3000 All contributions to U-Boot should conform to the Linux kernel
3001 coding style; see the kernel coding style guide at
3002 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
3003 script "scripts/Lindent" in your Linux kernel source directory.
3005 Source files originating from a different project (for example the
3006 MTD subsystem) are generally exempt from these guidelines and are not
3007 reformatted to ease subsequent migration to newer versions of those
3010 Please note that U-Boot is implemented in C (and to some small parts in
3011 Assembler); no C++ is used, so please do not use C++ style comments (//)
3014 Please also stick to the following formatting rules:
3015 - remove any trailing white space
3016 - use TAB characters for indentation and vertical alignment, not spaces
3017 - make sure NOT to use DOS '\r\n' line feeds
3018 - do not add more than 2 consecutive empty lines to source files
3019 - do not add trailing empty lines to source files
3021 Submissions which do not conform to the standards may be returned
3022 with a request to reformat the changes.
3028 Since the number of patches for U-Boot is growing, we need to
3029 establish some rules. Submissions which do not conform to these rules
3030 may be rejected, even when they contain important and valuable stuff.
3032 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
3034 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
3035 see https://lists.denx.de/listinfo/u-boot
3037 When you send a patch, please include the following information with
3040 * For bug fixes: a description of the bug and how your patch fixes
3041 this bug. Please try to include a way of demonstrating that the
3042 patch actually fixes something.
3044 * For new features: a description of the feature and your
3047 * For major contributions, add a MAINTAINERS file with your
3048 information and associated file and directory references.
3050 * When you add support for a new board, don't forget to add a
3051 maintainer e-mail address to the boards.cfg file, too.
3053 * If your patch adds new configuration options, don't forget to
3054 document these in the README file.
3056 * The patch itself. If you are using git (which is *strongly*
3057 recommended) you can easily generate the patch using the
3058 "git format-patch". If you then use "git send-email" to send it to
3059 the U-Boot mailing list, you will avoid most of the common problems
3060 with some other mail clients.
3062 If you cannot use git, use "diff -purN OLD NEW". If your version of
3063 diff does not support these options, then get the latest version of
3066 The current directory when running this command shall be the parent
3067 directory of the U-Boot source tree (i. e. please make sure that
3068 your patch includes sufficient directory information for the
3071 We prefer patches as plain text. MIME attachments are discouraged,
3072 and compressed attachments must not be used.
3074 * If one logical set of modifications affects or creates several
3075 files, all these changes shall be submitted in a SINGLE patch file.
3077 * Changesets that contain different, unrelated modifications shall be
3078 submitted as SEPARATE patches, one patch per changeset.
3083 * Before sending the patch, run the buildman script on your patched
3084 source tree and make sure that no errors or warnings are reported
3085 for any of the boards.
3087 * Keep your modifications to the necessary minimum: A patch
3088 containing several unrelated changes or arbitrary reformats will be
3089 returned with a request to re-formatting / split it.
3091 * If you modify existing code, make sure that your new code does not
3092 add to the memory footprint of the code ;-) Small is beautiful!
3093 When adding new features, these should compile conditionally only
3094 (using #ifdef), and the resulting code with the new feature
3095 disabled must not need more memory than the old code without your
3098 * Remember that there is a size limit of 100 kB per message on the
3099 u-boot mailing list. Bigger patches will be moderated. If they are
3100 reasonable and not too big, they will be acknowledged. But patches
3101 bigger than the size limit should be avoided.