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
464 The CFG_SYS_I2C_PCA953X_WIDTH option specifies a list of
465 chip-ngpio pairs that tell the PCA953X driver the number of
466 pins supported by a particular chip.
468 Note that if the GPIO device uses I2C, then the I2C interface
469 must also be configured. See I2C Support, below.
472 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
473 accesses and can checksum them or write a list of them out
474 to memory. See the 'iotrace' command for details. This is
475 useful for testing device drivers since it can confirm that
476 the driver behaves the same way before and after a code
477 change. Currently this is supported on sandbox and arm. To
478 add support for your architecture, add '#include <iotrace.h>'
479 to the bottom of arch/<arch>/include/asm/io.h and test.
481 Example output from the 'iotrace stats' command is below.
482 Note that if the trace buffer is exhausted, the checksum will
483 still continue to operate.
486 Start: 10000000 (buffer start address)
487 Size: 00010000 (buffer size)
488 Offset: 00000120 (current buffer offset)
489 Output: 10000120 (start + offset)
490 Count: 00000018 (number of trace records)
491 CRC32: 9526fb66 (CRC32 of all trace records)
495 When CONFIG_TIMESTAMP is selected, the timestamp
496 (date and time) of an image is printed by image
497 commands like bootm or iminfo. This option is
498 automatically enabled when you select CONFIG_CMD_DATE .
500 - Partition Labels (disklabels) Supported:
501 Zero or more of the following:
502 CONFIG_MAC_PARTITION Apple's MacOS partition table.
503 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
504 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
505 bootloader. Note 2TB partition limit; see
507 CONFIG_SCSI) you must configure support for at
508 least one non-MTD partition type as well.
510 - NETWORK Support (PCI):
512 Utility code for direct access to the SPI bus on Intel 8257x.
513 This does not do anything useful unless you set at least one
514 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
517 Support for National dp83815 chips.
520 Support for National dp8382[01] gigabit chips.
522 - NETWORK Support (other):
524 Support for the Calxeda XGMAC device
527 Support for SMSC's LAN91C96 chips.
529 CONFIG_LAN91C96_USE_32_BIT
530 Define this to enable 32 bit addressing
532 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
533 Define this if you have more then 3 PHYs.
536 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
538 CONFIG_FTGMAC100_EGIGA
539 Define this to use GE link update with gigabit PHY.
540 Define this if FTGMAC100 is connected to gigabit PHY.
541 If your system has 10/100 PHY only, it might not occur
542 wrong behavior. Because PHY usually return timeout or
543 useless data when polling gigabit status and gigabit
544 control registers. This behavior won't affect the
545 correctnessof 10/100 link speed update.
548 Support for Renesas on-chip Ethernet controller
550 CONFIG_SH_ETHER_USE_PORT
551 Define the number of ports to be used
553 CONFIG_SH_ETHER_PHY_ADDR
554 Define the ETH PHY's address
556 CONFIG_SH_ETHER_CACHE_WRITEBACK
557 If this option is set, the driver enables cache flush.
563 CONFIG_TPM_TIS_INFINEON
564 Support for Infineon i2c bus TPM devices. Only one device
565 per system is supported at this time.
567 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
568 Define the burst count bytes upper limit
571 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
573 CONFIG_TPM_ST33ZP24_I2C
574 Support for STMicroelectronics ST33ZP24 I2C devices.
575 Requires TPM_ST33ZP24 and I2C.
577 CONFIG_TPM_ST33ZP24_SPI
578 Support for STMicroelectronics ST33ZP24 SPI devices.
579 Requires TPM_ST33ZP24 and SPI.
582 Support for Atmel TWI TPM device. Requires I2C support.
585 Support for generic parallel port TPM devices. Only one device
586 per system is supported at this time.
588 CONFIG_TPM_TIS_BASE_ADDRESS
589 Base address where the generic TPM device is mapped
590 to. Contemporary x86 systems usually map it at
594 Define this to enable the TPM support library which provides
595 functional interfaces to some TPM commands.
596 Requires support for a TPM device.
598 CONFIG_TPM_AUTH_SESSIONS
599 Define this to enable authorized functions in the TPM library.
600 Requires CONFIG_TPM and CONFIG_SHA1.
603 At the moment only the UHCI host controller is
604 supported (PIP405, MIP405); define
605 CONFIG_USB_UHCI to enable it.
606 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
607 and define CONFIG_USB_STORAGE to enable the USB
610 Supported are USB Keyboards and USB Floppy drives
613 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
617 Define the below if you wish to use the USB console.
618 Once firmware is rebuilt from a serial console issue the
619 command "setenv stdin usbtty; setenv stdout usbtty" and
620 attach your USB cable. The Unix command "dmesg" should print
621 it has found a new device. The environment variable usbtty
622 can be set to gserial or cdc_acm to enable your device to
623 appear to a USB host as a Linux gserial device or a
624 Common Device Class Abstract Control Model serial device.
625 If you select usbtty = gserial you should be able to enumerate
627 # modprobe usbserial vendor=0xVendorID product=0xProductID
628 else if using cdc_acm, simply setting the environment
629 variable usbtty to be cdc_acm should suffice. The following
630 might be defined in YourBoardName.h
633 Define this to enable the high speed support for usb
634 device and usbtty. If this feature is enabled, a routine
635 int is_usbd_high_speed(void)
636 also needs to be defined by the driver to dynamically poll
637 whether the enumeration has succeded at high speed or full
640 If you have a USB-IF assigned VendorID then you may wish to
641 define your own vendor specific values either in BoardName.h
642 or directly in usbd_vendor_info.h. If you don't define
643 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
644 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
645 should pretend to be a Linux device to it's target host.
647 CONFIG_USBD_MANUFACTURER
648 Define this string as the name of your company for
649 - CONFIG_USBD_MANUFACTURER "my company"
651 CONFIG_USBD_PRODUCT_NAME
652 Define this string as the name of your product
653 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
656 Define this as your assigned Vendor ID from the USB
657 Implementors Forum. This *must* be a genuine Vendor ID
658 to avoid polluting the USB namespace.
659 - CONFIG_USBD_VENDORID 0xFFFF
661 CONFIG_USBD_PRODUCTID
662 Define this as the unique Product ID
664 - CONFIG_USBD_PRODUCTID 0xFFFF
666 - ULPI Layer Support:
667 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
668 the generic ULPI layer. The generic layer accesses the ULPI PHY
669 via the platform viewport, so you need both the genric layer and
670 the viewport enabled. Currently only Chipidea/ARC based
671 viewport is supported.
672 To enable the ULPI layer support, define CONFIG_USB_ULPI and
673 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
674 If your ULPI phy needs a different reference clock than the
675 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
676 the appropriate value in Hz.
680 Support for Renesas on-chip MMCIF controller
683 Define the base address of MMCIF registers
686 Define the clock frequency for MMCIF
688 - USB Device Firmware Update (DFU) class support:
690 This enables the USB portion of the DFU USB class
693 This enables support for exposing NAND devices via DFU.
696 This enables support for exposing RAM via DFU.
697 Note: DFU spec refer to non-volatile memory usage, but
698 allow usages beyond the scope of spec - here RAM usage,
699 one that would help mostly the developer.
701 CONFIG_SYS_DFU_DATA_BUF_SIZE
702 Dfu transfer uses a buffer before writing data to the
703 raw storage device. Make the size (in bytes) of this buffer
704 configurable. The size of this buffer is also configurable
705 through the "dfu_bufsiz" environment variable.
707 CONFIG_SYS_DFU_MAX_FILE_SIZE
708 When updating files rather than the raw storage device,
709 we use a static buffer to copy the file into and then write
710 the buffer once we've been given the whole file. Define
711 this to the maximum filesize (in bytes) for the buffer.
712 Default is 4 MiB if undefined.
714 DFU_DEFAULT_POLL_TIMEOUT
715 Poll timeout [ms], is the timeout a device can send to the
716 host. The host must wait for this timeout before sending
717 a subsequent DFU_GET_STATUS request to the device.
719 DFU_MANIFEST_POLL_TIMEOUT
720 Poll timeout [ms], which the device sends to the host when
721 entering dfuMANIFEST state. Host waits this timeout, before
722 sending again an USB request to the device.
725 See Kconfig help for available keyboard drivers.
728 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
730 The clock frequency of the MII bus
732 CONFIG_PHY_CMD_DELAY (ppc4xx)
734 Some PHY like Intel LXT971A need extra delay after
735 command issued before MII status register can be read
737 - BOOTP Recovery Mode:
738 CONFIG_BOOTP_RANDOM_DELAY
740 If you have many targets in a network that try to
741 boot using BOOTP, you may want to avoid that all
742 systems send out BOOTP requests at precisely the same
743 moment (which would happen for instance at recovery
744 from a power failure, when all systems will try to
745 boot, thus flooding the BOOTP server. Defining
746 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
747 inserted before sending out BOOTP requests. The
748 following delays are inserted then:
750 1st BOOTP request: delay 0 ... 1 sec
751 2nd BOOTP request: delay 0 ... 2 sec
752 3rd BOOTP request: delay 0 ... 4 sec
754 BOOTP requests: delay 0 ... 8 sec
756 CONFIG_BOOTP_ID_CACHE_SIZE
758 BOOTP packets are uniquely identified using a 32-bit ID. The
759 server will copy the ID from client requests to responses and
760 U-Boot will use this to determine if it is the destination of
761 an incoming response. Some servers will check that addresses
762 aren't in use before handing them out (usually using an ARP
763 ping) and therefore take up to a few hundred milliseconds to
764 respond. Network congestion may also influence the time it
765 takes for a response to make it back to the client. If that
766 time is too long, U-Boot will retransmit requests. In order
767 to allow earlier responses to still be accepted after these
768 retransmissions, U-Boot's BOOTP client keeps a small cache of
769 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
770 cache. The default is to keep IDs for up to four outstanding
771 requests. Increasing this will allow U-Boot to accept offers
772 from a BOOTP client in networks with unusually high latency.
774 - DHCP Advanced Options:
776 - Link-local IP address negotiation:
777 Negotiate with other link-local clients on the local network
778 for an address that doesn't require explicit configuration.
779 This is especially useful if a DHCP server cannot be guaranteed
780 to exist in all environments that the device must operate.
782 See doc/README.link-local for more information.
784 - MAC address from environment variables
786 FDT_SEQ_MACADDR_FROM_ENV
788 Fix-up device tree with MAC addresses fetched sequentially from
789 environment variables. This config work on assumption that
790 non-usable ethernet node of device-tree are either not present
791 or their status has been marked as "disabled".
796 The device id used in CDP trigger frames.
798 CONFIG_CDP_DEVICE_ID_PREFIX
800 A two character string which is prefixed to the MAC address
805 A printf format string which contains the ascii name of
806 the port. Normally is set to "eth%d" which sets
807 eth0 for the first Ethernet, eth1 for the second etc.
809 CONFIG_CDP_CAPABILITIES
811 A 32bit integer which indicates the device capabilities;
812 0x00000010 for a normal host which does not forwards.
816 An ascii string containing the version of the software.
820 An ascii string containing the name of the platform.
824 A 32bit integer sent on the trigger.
826 CONFIG_CDP_POWER_CONSUMPTION
828 A 16bit integer containing the power consumption of the
829 device in .1 of milliwatts.
831 CONFIG_CDP_APPLIANCE_VLAN_TYPE
833 A byte containing the id of the VLAN.
835 - Status LED: CONFIG_LED_STATUS
837 Several configurations allow to display the current
838 status using a LED. For instance, the LED will blink
839 fast while running U-Boot code, stop blinking as
840 soon as a reply to a BOOTP request was received, and
841 start blinking slow once the Linux kernel is running
842 (supported by a status LED driver in the Linux
843 kernel). Defining CONFIG_LED_STATUS enables this
848 CONFIG_LED_STATUS_GPIO
849 The status LED can be connected to a GPIO pin.
850 In such cases, the gpio_led driver can be used as a
851 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
852 to include the gpio_led driver in the U-Boot binary.
854 CONFIG_GPIO_LED_INVERTED_TABLE
855 Some GPIO connected LEDs may have inverted polarity in which
856 case the GPIO high value corresponds to LED off state and
857 GPIO low value corresponds to LED on state.
858 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
859 with a list of GPIO LEDs that have inverted polarity.
862 CFG_SYS_NUM_I2C_BUSES
863 Hold the number of i2c buses you want to use.
865 CONFIG_SYS_I2C_DIRECT_BUS
866 define this, if you don't use i2c muxes on your hardware.
867 if CFG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
871 define how many muxes are maximal consecutively connected
872 on one i2c bus. If you not use i2c muxes, omit this
876 hold a list of buses you want to use, only used if
877 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
878 a board with CFG_SYS_I2C_MAX_HOPS = 1 and
879 CFG_SYS_NUM_I2C_BUSES = 9:
881 CFG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
882 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
883 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
884 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
885 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
886 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
887 {1, {I2C_NULL_HOP}}, \
888 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
889 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
893 bus 0 on adapter 0 without a mux
894 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
895 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
896 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
897 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
898 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
899 bus 6 on adapter 1 without a mux
900 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
901 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
903 If you do not have i2c muxes on your board, omit this define.
905 - Legacy I2C Support:
906 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
907 then the following macros need to be defined (examples are
908 from include/configs/lwmon.h):
912 (Optional). Any commands necessary to enable the I2C
913 controller or configure ports.
915 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
919 The code necessary to make the I2C data line active
920 (driven). If the data line is open collector, this
923 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
927 The code necessary to make the I2C data line tri-stated
928 (inactive). If the data line is open collector, this
931 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
935 Code that returns true if the I2C data line is high,
938 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
942 If <bit> is true, sets the I2C data line high. If it
943 is false, it clears it (low).
945 eg: #define I2C_SDA(bit) \
946 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
947 else immr->im_cpm.cp_pbdat &= ~PB_SDA
951 If <bit> is true, sets the I2C clock line high. If it
952 is false, it clears it (low).
954 eg: #define I2C_SCL(bit) \
955 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
956 else immr->im_cpm.cp_pbdat &= ~PB_SCL
960 This delay is invoked four times per clock cycle so this
961 controls the rate of data transfer. The data rate thus
962 is 1 / (I2C_DELAY * 4). Often defined to be something
965 #define I2C_DELAY udelay(2)
967 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
969 If your arch supports the generic GPIO framework (asm/gpio.h),
970 then you may alternatively define the two GPIOs that are to be
971 used as SCL / SDA. Any of the previous I2C_xxx macros will
972 have GPIO-based defaults assigned to them as appropriate.
974 You should define these to the GPIO value as given directly to
975 the generic GPIO functions.
979 This option allows the use of multiple I2C buses, each of which
980 must have a controller. At any point in time, only one bus is
981 active. To switch to a different bus, use the 'i2c dev' command.
982 Note that bus numbering is zero-based.
986 This option specifies a list of I2C devices that will be skipped
987 when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
988 is set, specify a list of bus-device pairs. Otherwise, specify
989 a 1D array of device addresses
992 #undef CONFIG_I2C_MULTI_BUS
993 #define CFG_SYS_I2C_NOPROBES {0x50,0x68}
995 will skip addresses 0x50 and 0x68 on a board with one I2C bus
997 #define CONFIG_I2C_MULTI_BUS
998 #define CFG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1000 will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1004 If defined, then this indicates the I2C bus number for the RTC.
1005 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1007 CONFIG_SOFT_I2C_READ_REPEATED_START
1009 defining this will force the i2c_read() function in
1010 the soft_i2c driver to perform an I2C repeated start
1011 between writing the address pointer and reading the
1012 data. If this define is omitted the default behaviour
1013 of doing a stop-start sequence will be used. Most I2C
1014 devices can use either method, but some require one or
1017 - SPI Support: CONFIG_SPI
1019 Enables SPI driver (so far only tested with
1020 SPI EEPROM, also an instance works with Crystal A/D and
1021 D/As on the SACSng board)
1023 CONFIG_SYS_SPI_MXC_WAIT
1024 Timeout for waiting until spi transfer completed.
1025 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1027 - FPGA Support: CONFIG_FPGA
1029 Enables FPGA subsystem.
1031 CONFIG_FPGA_<vendor>
1033 Enables support for specific chip vendors.
1036 CONFIG_FPGA_<family>
1038 Enables support for FPGA family.
1039 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1041 CONFIG_SYS_FPGA_CHECK_BUSY
1043 Enable checks on FPGA configuration interface busy
1044 status by the configuration function. This option
1045 will require a board or device specific function to
1050 If defined, a function that provides delays in the FPGA
1051 configuration driver.
1053 CONFIG_SYS_FPGA_CHECK_ERROR
1055 Check for configuration errors during FPGA bitfile
1056 loading. For example, abort during Virtex II
1057 configuration if the INIT_B line goes low (which
1058 indicated a CRC error).
1060 CFG_SYS_FPGA_WAIT_INIT
1062 Maximum time to wait for the INIT_B line to de-assert
1063 after PROB_B has been de-asserted during a Virtex II
1064 FPGA configuration sequence. The default time is 500
1067 CFG_SYS_FPGA_WAIT_BUSY
1069 Maximum time to wait for BUSY to de-assert during
1070 Virtex II FPGA configuration. The default is 5 ms.
1072 CFG_SYS_FPGA_WAIT_CONFIG
1074 Time to wait after FPGA configuration. The default is
1077 - Vendor Parameter Protection:
1079 U-Boot considers the values of the environment
1080 variables "serial#" (Board Serial Number) and
1081 "ethaddr" (Ethernet Address) to be parameters that
1082 are set once by the board vendor / manufacturer, and
1083 protects these variables from casual modification by
1084 the user. Once set, these variables are read-only,
1085 and write or delete attempts are rejected. You can
1086 change this behaviour:
1088 If CONFIG_ENV_OVERWRITE is #defined in your config
1089 file, the write protection for vendor parameters is
1090 completely disabled. Anybody can change or delete
1093 Alternatively, if you define _both_ an ethaddr in the
1094 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1095 Ethernet address is installed in the environment,
1096 which can be changed exactly ONCE by the user. [The
1097 serial# is unaffected by this, i. e. it remains
1100 The same can be accomplished in a more flexible way
1101 for any variable by configuring the type of access
1102 to allow for those variables in the ".flags" variable
1103 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1108 Define this variable to enable the reservation of
1109 "protected RAM", i. e. RAM which is not overwritten
1110 by U-Boot. Define CONFIG_PRAM to hold the number of
1111 kB you want to reserve for pRAM. You can overwrite
1112 this default value by defining an environment
1113 variable "pram" to the number of kB you want to
1114 reserve. Note that the board info structure will
1115 still show the full amount of RAM. If pRAM is
1116 reserved, a new environment variable "mem" will
1117 automatically be defined to hold the amount of
1118 remaining RAM in a form that can be passed as boot
1119 argument to Linux, for instance like that:
1121 setenv bootargs ... mem=\${mem}
1124 This way you can tell Linux not to use this memory,
1125 either, which results in a memory region that will
1126 not be affected by reboots.
1128 *WARNING* If your board configuration uses automatic
1129 detection of the RAM size, you must make sure that
1130 this memory test is non-destructive. So far, the
1131 following board configurations are known to be
1134 IVMS8, IVML24, SPD8xx,
1135 HERMES, IP860, RPXlite, LWMON,
1141 In the current implementation, the local variables
1142 space and global environment variables space are
1143 separated. Local variables are those you define by
1144 simply typing `name=value'. To access a local
1145 variable later on, you have write `$name' or
1146 `${name}'; to execute the contents of a variable
1147 directly type `$name' at the command prompt.
1149 Global environment variables are those you use
1150 setenv/printenv to work with. To run a command stored
1151 in such a variable, you need to use the run command,
1152 and you must not use the '$' sign to access them.
1154 To store commands and special characters in a
1155 variable, please use double quotation marks
1156 surrounding the whole text of the variable, instead
1157 of the backslashes before semicolons and special
1160 - Default Environment:
1161 CONFIG_EXTRA_ENV_SETTINGS
1163 Define this to contain any number of null terminated
1164 strings (variable = value pairs) that will be part of
1165 the default environment compiled into the boot image.
1167 For example, place something like this in your
1168 board's config file:
1170 #define CONFIG_EXTRA_ENV_SETTINGS \
1174 Warning: This method is based on knowledge about the
1175 internal format how the environment is stored by the
1176 U-Boot code. This is NOT an official, exported
1177 interface! Although it is unlikely that this format
1178 will change soon, there is no guarantee either.
1179 You better know what you are doing here.
1181 Note: overly (ab)use of the default environment is
1182 discouraged. Make sure to check other ways to preset
1183 the environment like the "source" command or the
1186 CONFIG_DELAY_ENVIRONMENT
1188 Normally the environment is loaded when the board is
1189 initialised so that it is available to U-Boot. This inhibits
1190 that so that the environment is not available until
1191 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1192 this is instead controlled by the value of
1193 /config/load-environment.
1195 CONFIG_STANDALONE_LOAD_ADDR
1197 This option defines a board specific value for the
1198 address where standalone program gets loaded, thus
1199 overwriting the architecture dependent default
1202 - Automatic software updates via TFTP server
1204 CONFIG_UPDATE_TFTP_CNT_MAX
1205 CONFIG_UPDATE_TFTP_MSEC_MAX
1207 These options enable and control the auto-update feature;
1208 for a more detailed description refer to doc/README.update.
1210 - MTD Support (mtdparts command, UBI support)
1211 CONFIG_MTD_UBI_WL_THRESHOLD
1212 This parameter defines the maximum difference between the highest
1213 erase counter value and the lowest erase counter value of eraseblocks
1214 of UBI devices. When this threshold is exceeded, UBI starts performing
1215 wear leveling by means of moving data from eraseblock with low erase
1216 counter to eraseblocks with high erase counter.
1218 The default value should be OK for SLC NAND flashes, NOR flashes and
1219 other flashes which have eraseblock life-cycle 100000 or more.
1220 However, in case of MLC NAND flashes which typically have eraseblock
1221 life-cycle less than 10000, the threshold should be lessened (e.g.,
1222 to 128 or 256, although it does not have to be power of 2).
1226 CONFIG_MTD_UBI_BEB_LIMIT
1227 This option specifies the maximum bad physical eraseblocks UBI
1228 expects on the MTD device (per 1024 eraseblocks). If the
1229 underlying flash does not admit of bad eraseblocks (e.g. NOR
1230 flash), this value is ignored.
1232 NAND datasheets often specify the minimum and maximum NVM
1233 (Number of Valid Blocks) for the flashes' endurance lifetime.
1234 The maximum expected bad eraseblocks per 1024 eraseblocks
1235 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1236 which gives 20 for most NANDs (MaxNVB is basically the total
1237 count of eraseblocks on the chip).
1239 To put it differently, if this value is 20, UBI will try to
1240 reserve about 1.9% of physical eraseblocks for bad blocks
1241 handling. And that will be 1.9% of eraseblocks on the entire
1242 NAND chip, not just the MTD partition UBI attaches. This means
1243 that if you have, say, a NAND flash chip admits maximum 40 bad
1244 eraseblocks, and it is split on two MTD partitions of the same
1245 size, UBI will reserve 40 eraseblocks when attaching a
1250 CONFIG_MTD_UBI_FASTMAP
1251 Fastmap is a mechanism which allows attaching an UBI device
1252 in nearly constant time. Instead of scanning the whole MTD device it
1253 only has to locate a checkpoint (called fastmap) on the device.
1254 The on-flash fastmap contains all information needed to attach
1255 the device. Using fastmap makes only sense on large devices where
1256 attaching by scanning takes long. UBI will not automatically install
1257 a fastmap on old images, but you can set the UBI parameter
1258 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1259 that fastmap-enabled images are still usable with UBI implementations
1260 without fastmap support. On typical flash devices the whole fastmap
1261 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1263 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1264 Set this parameter to enable fastmap automatically on images
1268 CONFIG_MTD_UBI_FM_DEBUG
1269 Enable UBI fastmap debug
1274 Enable building of SPL globally.
1276 CONFIG_SPL_PANIC_ON_RAW_IMAGE
1277 When defined, SPL will panic() if the image it has
1278 loaded does not have a signature.
1279 Defining this is useful when code which loads images
1280 in SPL cannot guarantee that absolutely all read errors
1282 An example is the LPC32XX MLC NAND driver, which will
1283 consider that a completely unreadable NAND block is bad,
1284 and thus should be skipped silently.
1286 CONFIG_SPL_DISPLAY_PRINT
1287 For ARM, enable an optional function to print more information
1288 about the running system.
1290 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
1291 Set this for NAND SPL on PPC mpc83xx targets, so that
1292 start.S waits for the rest of the SPL to load before
1293 continuing (the hardware starts execution after just
1294 loading the first page rather than the full 4K).
1297 Support for a lightweight UBI (fastmap) scanner and
1300 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
1301 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
1302 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
1303 CFG_SYS_NAND_ECCPOS, CFG_SYS_NAND_ECCSIZE,
1304 CFG_SYS_NAND_ECCBYTES
1305 Defines the size and behavior of the NAND that SPL uses
1308 CFG_SYS_NAND_U_BOOT_DST
1309 Location in memory to load U-Boot to
1311 CFG_SYS_NAND_U_BOOT_SIZE
1312 Size of image to load
1314 CFG_SYS_NAND_U_BOOT_START
1315 Entry point in loaded image to jump to
1317 CONFIG_SPL_RAM_DEVICE
1318 Support for running image already present in ram, in SPL binary
1320 CONFIG_SPL_FIT_PRINT
1321 Printing information about a FIT image adds quite a bit of
1322 code to SPL. So this is normally disabled in SPL. Use this
1323 option to re-enable it. This will affect the output of the
1324 bootm command when booting a FIT image.
1326 - Interrupt support (PPC):
1328 There are common interrupt_init() and timer_interrupt()
1329 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
1330 for CPU specific initialization. interrupt_init_cpu()
1331 should set decrementer_count to appropriate value. If
1332 CPU resets decrementer automatically after interrupt
1333 (ppc4xx) it should set decrementer_count to zero.
1334 timer_interrupt() calls timer_interrupt_cpu() for CPU
1335 specific handling. If board has watchdog / status_led
1336 / other_activity_monitor it works automatically from
1337 general timer_interrupt().
1340 Board initialization settings:
1341 ------------------------------
1343 During Initialization u-boot calls a number of board specific functions
1344 to allow the preparation of board specific prerequisites, e.g. pin setup
1345 before drivers are initialized. To enable these callbacks the
1346 following configuration macros have to be defined. Currently this is
1347 architecture specific, so please check arch/your_architecture/lib/board.c
1348 typically in board_init_f() and board_init_r().
1350 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
1351 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
1352 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
1354 Configuration Settings:
1355 -----------------------
1357 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
1358 Optionally it can be defined to support 64-bit memory commands.
1360 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
1361 undefine this when you're short of memory.
1363 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
1364 width of the commands listed in the 'help' command output.
1366 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
1367 prompt for user input.
1369 - CFG_SYS_BAUDRATE_TABLE:
1370 List of legal baudrate settings for this board.
1372 - CFG_SYS_MEM_RESERVE_SECURE
1373 Only implemented for ARMv8 for now.
1374 If defined, the size of CFG_SYS_MEM_RESERVE_SECURE memory
1375 is substracted from total RAM and won't be reported to OS.
1376 This memory can be used as secure memory. A variable
1377 gd->arch.secure_ram is used to track the location. In systems
1378 the RAM base is not zero, or RAM is divided into banks,
1379 this variable needs to be recalcuated to get the address.
1381 - CFG_SYS_SDRAM_BASE:
1382 Physical start address of SDRAM. _Must_ be 0 here.
1384 - CFG_SYS_FLASH_BASE:
1385 Physical start address of Flash memory.
1387 - CONFIG_SYS_MALLOC_LEN:
1388 Size of DRAM reserved for malloc() use.
1390 - CONFIG_SYS_MALLOC_F_LEN
1391 Size of the malloc() pool for use before relocation. If
1392 this is defined, then a very simple malloc() implementation
1393 will become available before relocation. The address is just
1394 below the global data, and the stack is moved down to make
1397 This feature allocates regions with increasing addresses
1398 within the region. calloc() is supported, but realloc()
1399 is not available. free() is supported but does nothing.
1400 The memory will be freed (or in fact just forgotten) when
1401 U-Boot relocates itself.
1403 - CONFIG_SYS_MALLOC_SIMPLE
1404 Provides a simple and small malloc() and calloc() for those
1405 boards which do not use the full malloc in SPL (which is
1406 enabled with CONFIG_SYS_SPL_MALLOC).
1408 - CFG_SYS_BOOTMAPSZ:
1409 Maximum size of memory mapped by the startup code of
1410 the Linux kernel; all data that must be processed by
1411 the Linux kernel (bd_info, boot arguments, FDT blob if
1412 used) must be put below this limit, unless "bootm_low"
1413 environment variable is defined and non-zero. In such case
1414 all data for the Linux kernel must be between "bootm_low"
1415 and "bootm_low" + CFG_SYS_BOOTMAPSZ. The environment
1416 variable "bootm_mapsize" will override the value of
1417 CFG_SYS_BOOTMAPSZ. If CFG_SYS_BOOTMAPSZ is undefined,
1418 then the value in "bootm_size" will be used instead.
1420 - CONFIG_SYS_BOOT_GET_CMDLINE:
1421 Enables allocating and saving kernel cmdline in space between
1422 "bootm_low" and "bootm_low" + BOOTMAPSZ.
1424 - CONFIG_SYS_BOOT_GET_KBD:
1425 Enables allocating and saving a kernel copy of the bd_info in
1426 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
1428 - CONFIG_SYS_FLASH_PROTECTION
1429 If defined, hardware flash sectors protection is used
1430 instead of U-Boot software protection.
1432 - CONFIG_SYS_FLASH_CFI:
1433 Define if the flash driver uses extra elements in the
1434 common flash structure for storing flash geometry.
1436 - CONFIG_FLASH_CFI_DRIVER
1437 This option also enables the building of the cfi_flash driver
1438 in the drivers directory
1440 - CONFIG_FLASH_CFI_MTD
1441 This option enables the building of the cfi_mtd driver
1442 in the drivers directory. The driver exports CFI flash
1445 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
1446 Use buffered writes to flash.
1448 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1449 - CONFIG_ENV_FLAGS_LIST_STATIC
1450 Enable validation of the values given to environment variables when
1451 calling env set. Variables can be restricted to only decimal,
1452 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
1453 the variables can also be restricted to IP address or MAC address.
1455 The format of the list is:
1456 type_attribute = [s|d|x|b|i|m]
1457 access_attribute = [a|r|o|c]
1458 attributes = type_attribute[access_attribute]
1459 entry = variable_name[:attributes]
1462 The type attributes are:
1463 s - String (default)
1466 b - Boolean ([1yYtT|0nNfF])
1470 The access attributes are:
1476 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1477 Define this to a list (string) to define the ".flags"
1478 environment variable in the default or embedded environment.
1480 - CONFIG_ENV_FLAGS_LIST_STATIC
1481 Define this to a list (string) to define validation that
1482 should be done if an entry is not found in the ".flags"
1483 environment variable. To override a setting in the static
1484 list, simply add an entry for the same variable name to the
1487 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
1488 regular expression. This allows multiple variables to define the same
1489 flags without explicitly listing them for each variable.
1491 The following definitions that deal with the placement and management
1492 of environment data (variable area); in general, we support the
1493 following configurations:
1495 BE CAREFUL! The first access to the environment happens quite early
1496 in U-Boot initialization (when we try to get the setting of for the
1497 console baudrate). You *MUST* have mapped your NVRAM area then, or
1500 Please note that even with NVRAM we still use a copy of the
1501 environment in RAM: we could work on NVRAM directly, but we want to
1502 keep settings there always unmodified except somebody uses "saveenv"
1503 to save the current settings.
1505 BE CAREFUL! For some special cases, the local device can not use
1506 "saveenv" command. For example, the local device will get the
1507 environment stored in a remote NOR flash by SRIO or PCIE link,
1508 but it can not erase, write this NOR flash by SRIO or PCIE interface.
1510 - CONFIG_NAND_ENV_DST
1512 Defines address in RAM to which the nand_spl code should copy the
1513 environment. If redundant environment is used, it will be copied to
1514 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
1516 Please note that the environment is read-only until the monitor
1517 has been relocated to RAM and a RAM copy of the environment has been
1518 created; also, when using EEPROM you will have to use env_get_f()
1519 until then to read environment variables.
1521 The environment is protected by a CRC32 checksum. Before the monitor
1522 is relocated into RAM, as a result of a bad CRC you will be working
1523 with the compiled-in default environment - *silently*!!! [This is
1524 necessary, because the first environment variable we need is the
1525 "baudrate" setting for the console - if we have a bad CRC, we don't
1526 have any device yet where we could complain.]
1528 Note: once the monitor has been relocated, then it will complain if
1529 the default environment is used; a new CRC is computed as soon as you
1530 use the "saveenv" command to store a valid environment.
1532 - CONFIG_SYS_FAULT_MII_ADDR:
1533 MII address of the PHY to check for the Ethernet link state.
1535 - CONFIG_DISPLAY_BOARDINFO
1536 Display information about the board that U-Boot is running on
1537 when U-Boot starts up. The board function checkboard() is called
1540 - CONFIG_DISPLAY_BOARDINFO_LATE
1541 Similar to the previous option, but display this information
1542 later, once stdio is running and output goes to the LCD, if
1545 Low Level (hardware related) configuration options:
1546 ---------------------------------------------------
1548 - CONFIG_SYS_CACHELINE_SIZE:
1549 Cache Line Size of the CPU.
1551 - CONFIG_SYS_CCSRBAR_DEFAULT:
1552 Default (power-on reset) physical address of CCSR on Freescale
1556 Virtual address of CCSR. On a 32-bit build, this is typically
1557 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
1559 - CFG_SYS_CCSRBAR_PHYS:
1560 Physical address of CCSR. CCSR can be relocated to a new
1561 physical address, if desired. In this case, this macro should
1562 be set to that address. Otherwise, it should be set to the
1563 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
1564 is typically relocated on 36-bit builds. It is recommended
1565 that this macro be defined via the _HIGH and _LOW macros:
1567 #define CFG_SYS_CCSRBAR_PHYS ((CFG_SYS_CCSRBAR_PHYS_HIGH
1568 * 1ull) << 32 | CFG_SYS_CCSRBAR_PHYS_LOW)
1570 - CFG_SYS_CCSRBAR_PHYS_HIGH:
1571 Bits 33-36 of CFG_SYS_CCSRBAR_PHYS. This value is typically
1572 either 0 (32-bit build) or 0xF (36-bit build). This macro is
1573 used in assembly code, so it must not contain typecasts or
1574 integer size suffixes (e.g. "ULL").
1576 - CFG_SYS_CCSRBAR_PHYS_LOW:
1577 Lower 32-bits of CFG_SYS_CCSRBAR_PHYS. This macro is
1578 used in assembly code, so it must not contain typecasts or
1579 integer size suffixes (e.g. "ULL").
1581 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
1582 DO NOT CHANGE unless you know exactly what you're
1583 doing! (11-4) [MPC8xx systems only]
1585 - CFG_SYS_INIT_RAM_ADDR:
1587 Start address of memory area that can be used for
1588 initial data and stack; please note that this must be
1589 writable memory that is working WITHOUT special
1590 initialization, i. e. you CANNOT use normal RAM which
1591 will become available only after programming the
1592 memory controller and running certain initialization
1595 U-Boot uses the following memory types:
1596 - MPC8xx: IMMR (internal memory of the CPU)
1598 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
1600 - CONFIG_SYS_OR_TIMING_SDRAM:
1603 - CONFIG_SYS_SRIOn_MEM_VIRT:
1604 Virtual Address of SRIO port 'n' memory region
1606 - CONFIG_SYS_SRIOn_MEM_PHYxS:
1607 Physical Address of SRIO port 'n' memory region
1609 - CONFIG_SYS_SRIOn_MEM_SIZE:
1610 Size of SRIO port 'n' memory region
1612 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
1613 Defined to tell the NAND controller that the NAND chip is using
1615 Not all NAND drivers use this symbol.
1616 Example of drivers that use it:
1617 - drivers/mtd/nand/raw/ndfc.c
1618 - drivers/mtd/nand/raw/mxc_nand.c
1620 - CONFIG_SYS_NDFC_EBC0_CFG
1621 Sets the EBC0_CFG register for the NDFC. If not defined
1622 a default value will be used.
1624 - CONFIG_SYS_SPD_BUS_NUM
1625 If SPD EEPROM is on an I2C bus other than the first
1626 one, specify here. Note that the value must resolve
1627 to something your driver can deal with.
1629 - CONFIG_FSL_DDR_INTERACTIVE
1630 Enable interactive DDR debugging. See doc/README.fsl-ddr.
1632 - CONFIG_FSL_DDR_SYNC_REFRESH
1633 Enable sync of refresh for multiple controllers.
1635 - CONFIG_FSL_DDR_BIST
1636 Enable built-in memory test for Freescale DDR controllers.
1639 Enable RMII mode for all FECs.
1640 Note that this is a global option, we can't
1641 have one FEC in standard MII mode and another in RMII mode.
1643 - CONFIG_CRC32_VERIFY
1644 Add a verify option to the crc32 command.
1647 => crc32 -v <address> <count> <crc32>
1649 Where address/count indicate a memory area
1650 and crc32 is the correct crc32 which the
1654 Add the "loopw" memory command. This only takes effect if
1655 the memory commands are activated globally (CONFIG_CMD_MEMORY).
1657 - CONFIG_CMD_MX_CYCLIC
1658 Add the "mdc" and "mwc" memory commands. These are cyclic
1663 This command will print 4 bytes (10,11,12,13) each 500 ms.
1665 => mwc.l 100 12345678 10
1666 This command will write 12345678 to address 100 all 10 ms.
1668 This only takes effect if the memory commands are activated
1669 globally (CONFIG_CMD_MEMORY).
1672 Set when the currently-running compilation is for an artifact
1673 that will end up in the SPL (as opposed to the TPL or U-Boot
1674 proper). Code that needs stage-specific behavior should check
1678 Set when the currently-running compilation is for an artifact
1679 that will end up in the TPL (as opposed to the SPL or U-Boot
1680 proper). Code that needs stage-specific behavior should check
1683 - CONFIG_ARCH_MAP_SYSMEM
1684 Generally U-Boot (and in particular the md command) uses
1685 effective address. It is therefore not necessary to regard
1686 U-Boot address as virtual addresses that need to be translated
1687 to physical addresses. However, sandbox requires this, since
1688 it maintains its own little RAM buffer which contains all
1689 addressable memory. This option causes some memory accesses
1690 to be mapped through map_sysmem() / unmap_sysmem().
1692 - CONFIG_X86_RESET_VECTOR
1693 If defined, the x86 reset vector code is included. This is not
1694 needed when U-Boot is running from Coreboot.
1696 Freescale QE/FMAN Firmware Support:
1697 -----------------------------------
1699 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
1700 loading of "firmware", which is encoded in the QE firmware binary format.
1701 This firmware often needs to be loaded during U-Boot booting, so macros
1702 are used to identify the storage device (NOR flash, SPI, etc) and the address
1705 - CONFIG_SYS_FMAN_FW_ADDR
1706 The address in the storage device where the FMAN microcode is located. The
1707 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1710 - CONFIG_SYS_QE_FW_ADDR
1711 The address in the storage device where the QE microcode is located. The
1712 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1715 - CONFIG_SYS_QE_FMAN_FW_LENGTH
1716 The maximum possible size of the firmware. The firmware binary format
1717 has a field that specifies the actual size of the firmware, but it
1718 might not be possible to read any part of the firmware unless some
1719 local storage is allocated to hold the entire firmware first.
1721 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
1722 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
1723 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
1724 virtual address in NOR flash.
1726 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
1727 Specifies that QE/FMAN firmware is located in NAND flash.
1728 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
1730 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
1731 Specifies that QE/FMAN firmware is located on the primary SD/MMC
1732 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
1734 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
1735 Specifies that QE/FMAN firmware is located in the remote (master)
1736 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
1737 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
1738 window->master inbound window->master LAW->the ucode address in
1739 master's memory space.
1741 Freescale Layerscape Management Complex Firmware Support:
1742 ---------------------------------------------------------
1743 The Freescale Layerscape Management Complex (MC) supports the loading of
1745 This firmware often needs to be loaded during U-Boot booting, so macros
1746 are used to identify the storage device (NOR flash, SPI, etc) and the address
1749 - CONFIG_FSL_MC_ENET
1750 Enable the MC driver for Layerscape SoCs.
1752 Freescale Layerscape Debug Server Support:
1753 -------------------------------------------
1754 The Freescale Layerscape Debug Server Support supports the loading of
1755 "Debug Server firmware" and triggering SP boot-rom.
1756 This firmware often needs to be loaded during U-Boot booting.
1758 - CONFIG_SYS_MC_RSV_MEM_ALIGN
1759 Define alignment of reserved memory MC requires
1764 In order to achieve reproducible builds, timestamps used in the U-Boot build
1765 process have to be set to a fixed value.
1767 This is done using the SOURCE_DATE_EPOCH environment variable.
1768 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
1769 option for U-Boot or an environment variable in U-Boot.
1771 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
1773 Building the Software:
1774 ======================
1776 Building U-Boot has been tested in several native build environments
1777 and in many different cross environments. Of course we cannot support
1778 all possibly existing versions of cross development tools in all
1779 (potentially obsolete) versions. In case of tool chain problems we
1780 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
1781 which is extensively used to build and test U-Boot.
1783 If you are not using a native environment, it is assumed that you
1784 have GNU cross compiling tools available in your path. In this case,
1785 you must set the environment variable CROSS_COMPILE in your shell.
1786 Note that no changes to the Makefile or any other source files are
1787 necessary. For example using the ELDK on a 4xx CPU, please enter:
1789 $ CROSS_COMPILE=ppc_4xx-
1790 $ export CROSS_COMPILE
1792 U-Boot is intended to be simple to build. After installing the
1793 sources you must configure U-Boot for one specific board type. This
1798 where "NAME_defconfig" is the name of one of the existing configu-
1799 rations; see configs/*_defconfig for supported names.
1801 Note: for some boards special configuration names may exist; check if
1802 additional information is available from the board vendor; for
1803 instance, the TQM823L systems are available without (standard)
1804 or with LCD support. You can select such additional "features"
1805 when choosing the configuration, i. e.
1807 make TQM823L_defconfig
1808 - will configure for a plain TQM823L, i. e. no LCD support
1810 make TQM823L_LCD_defconfig
1811 - will configure for a TQM823L with U-Boot console on LCD
1816 Finally, type "make all", and you should get some working U-Boot
1817 images ready for download to / installation on your system:
1819 - "u-boot.bin" is a raw binary image
1820 - "u-boot" is an image in ELF binary format
1821 - "u-boot.srec" is in Motorola S-Record format
1823 By default the build is performed locally and the objects are saved
1824 in the source directory. One of the two methods can be used to change
1825 this behavior and build U-Boot to some external directory:
1827 1. Add O= to the make command line invocations:
1829 make O=/tmp/build distclean
1830 make O=/tmp/build NAME_defconfig
1831 make O=/tmp/build all
1833 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
1835 export KBUILD_OUTPUT=/tmp/build
1840 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
1843 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
1844 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
1845 For example to treat all compiler warnings as errors:
1847 make KCFLAGS=-Werror
1849 Please be aware that the Makefiles assume you are using GNU make, so
1850 for instance on NetBSD you might need to use "gmake" instead of
1854 If the system board that you have is not listed, then you will need
1855 to port U-Boot to your hardware platform. To do this, follow these
1858 1. Create a new directory to hold your board specific code. Add any
1859 files you need. In your board directory, you will need at least
1860 the "Makefile" and a "<board>.c".
1861 2. Create a new configuration file "include/configs/<board>.h" for
1863 3. If you're porting U-Boot to a new CPU, then also create a new
1864 directory to hold your CPU specific code. Add any files you need.
1865 4. Run "make <board>_defconfig" with your new name.
1866 5. Type "make", and you should get a working "u-boot.srec" file
1867 to be installed on your target system.
1868 6. Debug and solve any problems that might arise.
1869 [Of course, this last step is much harder than it sounds.]
1872 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
1873 ==============================================================
1875 If you have modified U-Boot sources (for instance added a new board
1876 or support for new devices, a new CPU, etc.) you are expected to
1877 provide feedback to the other developers. The feedback normally takes
1878 the form of a "patch", i.e. a context diff against a certain (latest
1879 official or latest in the git repository) version of U-Boot sources.
1881 But before you submit such a patch, please verify that your modifi-
1882 cation did not break existing code. At least make sure that *ALL* of
1883 the supported boards compile WITHOUT ANY compiler warnings. To do so,
1884 just run the buildman script (tools/buildman/buildman), which will
1885 configure and build U-Boot for ALL supported system. Be warned, this
1886 will take a while. Please see the buildman README, or run 'buildman -H'
1890 See also "U-Boot Porting Guide" below.
1893 Monitor Commands - Overview:
1894 ============================
1896 go - start application at address 'addr'
1897 run - run commands in an environment variable
1898 bootm - boot application image from memory
1899 bootp - boot image via network using BootP/TFTP protocol
1900 bootz - boot zImage from memory
1901 tftpboot- boot image via network using TFTP protocol
1902 and env variables "ipaddr" and "serverip"
1903 (and eventually "gatewayip")
1904 tftpput - upload a file via network using TFTP protocol
1905 rarpboot- boot image via network using RARP/TFTP protocol
1906 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
1907 loads - load S-Record file over serial line
1908 loadb - load binary file over serial line (kermit mode)
1909 loadm - load binary blob from source address to destination address
1911 mm - memory modify (auto-incrementing)
1912 nm - memory modify (constant address)
1913 mw - memory write (fill)
1916 cmp - memory compare
1917 crc32 - checksum calculation
1918 i2c - I2C sub-system
1919 sspi - SPI utility commands
1920 base - print or set address offset
1921 printenv- print environment variables
1922 pwm - control pwm channels
1923 setenv - set environment variables
1924 saveenv - save environment variables to persistent storage
1925 protect - enable or disable FLASH write protection
1926 erase - erase FLASH memory
1927 flinfo - print FLASH memory information
1928 nand - NAND memory operations (see doc/README.nand)
1929 bdinfo - print Board Info structure
1930 iminfo - print header information for application image
1931 coninfo - print console devices and informations
1932 ide - IDE sub-system
1933 loop - infinite loop on address range
1934 loopw - infinite write loop on address range
1935 mtest - simple RAM test
1936 icache - enable or disable instruction cache
1937 dcache - enable or disable data cache
1938 reset - Perform RESET of the CPU
1939 echo - echo args to console
1940 version - print monitor version
1941 help - print online help
1942 ? - alias for 'help'
1945 Monitor Commands - Detailed Description:
1946 ========================================
1950 For now: just type "help <command>".
1953 Note for Redundant Ethernet Interfaces:
1954 =======================================
1956 Some boards come with redundant Ethernet interfaces; U-Boot supports
1957 such configurations and is capable of automatic selection of a
1958 "working" interface when needed. MAC assignment works as follows:
1960 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
1961 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
1962 "eth1addr" (=>eth1), "eth2addr", ...
1964 If the network interface stores some valid MAC address (for instance
1965 in SROM), this is used as default address if there is NO correspon-
1966 ding setting in the environment; if the corresponding environment
1967 variable is set, this overrides the settings in the card; that means:
1969 o If the SROM has a valid MAC address, and there is no address in the
1970 environment, the SROM's address is used.
1972 o If there is no valid address in the SROM, and a definition in the
1973 environment exists, then the value from the environment variable is
1976 o If both the SROM and the environment contain a MAC address, and
1977 both addresses are the same, this MAC address is used.
1979 o If both the SROM and the environment contain a MAC address, and the
1980 addresses differ, the value from the environment is used and a
1983 o If neither SROM nor the environment contain a MAC address, an error
1984 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
1985 a random, locally-assigned MAC is used.
1987 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
1988 will be programmed into hardware as part of the initialization process. This
1989 may be skipped by setting the appropriate 'ethmacskip' environment variable.
1990 The naming convention is as follows:
1991 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
1996 U-Boot is capable of booting (and performing other auxiliary operations on)
1997 images in two formats:
1999 New uImage format (FIT)
2000 -----------------------
2002 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
2003 to Flattened Device Tree). It allows the use of images with multiple
2004 components (several kernels, ramdisks, etc.), with contents protected by
2005 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
2011 Old image format is based on binary files which can be basically anything,
2012 preceded by a special header; see the definitions in include/image.h for
2013 details; basically, the header defines the following image properties:
2015 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
2016 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
2017 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
2018 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
2019 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
2020 IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
2021 Currently supported: ARM, Intel x86, MIPS, Nios II, PowerPC).
2022 * Compression Type (uncompressed, gzip, bzip2)
2028 The header is marked by a special Magic Number, and both the header
2029 and the data portions of the image are secured against corruption by
2036 Although U-Boot should support any OS or standalone application
2037 easily, the main focus has always been on Linux during the design of
2040 U-Boot includes many features that so far have been part of some
2041 special "boot loader" code within the Linux kernel. Also, any
2042 "initrd" images to be used are no longer part of one big Linux image;
2043 instead, kernel and "initrd" are separate images. This implementation
2044 serves several purposes:
2046 - the same features can be used for other OS or standalone
2047 applications (for instance: using compressed images to reduce the
2048 Flash memory footprint)
2050 - it becomes much easier to port new Linux kernel versions because
2051 lots of low-level, hardware dependent stuff are done by U-Boot
2053 - the same Linux kernel image can now be used with different "initrd"
2054 images; of course this also means that different kernel images can
2055 be run with the same "initrd". This makes testing easier (you don't
2056 have to build a new "zImage.initrd" Linux image when you just
2057 change a file in your "initrd"). Also, a field-upgrade of the
2058 software is easier now.
2064 Porting Linux to U-Boot based systems:
2065 ---------------------------------------
2067 U-Boot cannot save you from doing all the necessary modifications to
2068 configure the Linux device drivers for use with your target hardware
2069 (no, we don't intend to provide a full virtual machine interface to
2072 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
2074 Just make sure your machine specific header file (for instance
2075 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2076 Information structure as we define in include/asm-<arch>/u-boot.h,
2077 and make sure that your definition of IMAP_ADDR uses the same value
2078 as your U-Boot configuration in CONFIG_SYS_IMMR.
2080 Note that U-Boot now has a driver model, a unified model for drivers.
2081 If you are adding a new driver, plumb it into driver model. If there
2082 is no uclass available, you are encouraged to create one. See
2086 Configuring the Linux kernel:
2087 -----------------------------
2089 No specific requirements for U-Boot. Make sure you have some root
2090 device (initial ramdisk, NFS) for your target system.
2093 Building a Linux Image:
2094 -----------------------
2096 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2097 not used. If you use recent kernel source, a new build target
2098 "uImage" will exist which automatically builds an image usable by
2099 U-Boot. Most older kernels also have support for a "pImage" target,
2100 which was introduced for our predecessor project PPCBoot and uses a
2101 100% compatible format.
2105 make TQM850L_defconfig
2110 The "uImage" build target uses a special tool (in 'tools/mkimage') to
2111 encapsulate a compressed Linux kernel image with header information,
2112 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2114 * build a standard "vmlinux" kernel image (in ELF binary format):
2116 * convert the kernel into a raw binary image:
2118 ${CROSS_COMPILE}-objcopy -O binary \
2119 -R .note -R .comment \
2120 -S vmlinux linux.bin
2122 * compress the binary image:
2126 * package compressed binary image for U-Boot:
2128 mkimage -A ppc -O linux -T kernel -C gzip \
2129 -a 0 -e 0 -n "Linux Kernel Image" \
2130 -d linux.bin.gz uImage
2133 The "mkimage" tool can also be used to create ramdisk images for use
2134 with U-Boot, either separated from the Linux kernel image, or
2135 combined into one file. "mkimage" encapsulates the images with a 64
2136 byte header containing information about target architecture,
2137 operating system, image type, compression method, entry points, time
2138 stamp, CRC32 checksums, etc.
2140 "mkimage" can be called in two ways: to verify existing images and
2141 print the header information, or to build new images.
2143 In the first form (with "-l" option) mkimage lists the information
2144 contained in the header of an existing U-Boot image; this includes
2145 checksum verification:
2147 tools/mkimage -l image
2148 -l ==> list image header information
2150 The second form (with "-d" option) is used to build a U-Boot image
2151 from a "data file" which is used as image payload:
2153 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
2154 -n name -d data_file image
2155 -A ==> set architecture to 'arch'
2156 -O ==> set operating system to 'os'
2157 -T ==> set image type to 'type'
2158 -C ==> set compression type 'comp'
2159 -a ==> set load address to 'addr' (hex)
2160 -e ==> set entry point to 'ep' (hex)
2161 -n ==> set image name to 'name'
2162 -d ==> use image data from 'datafile'
2164 Right now, all Linux kernels for PowerPC systems use the same load
2165 address (0x00000000), but the entry point address depends on the
2168 - 2.2.x kernels have the entry point at 0x0000000C,
2169 - 2.3.x and later kernels have the entry point at 0x00000000.
2171 So a typical call to build a U-Boot image would read:
2173 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2174 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
2175 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
2176 > examples/uImage.TQM850L
2177 Image Name: 2.4.4 kernel for TQM850L
2178 Created: Wed Jul 19 02:34:59 2000
2179 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2180 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2181 Load Address: 0x00000000
2182 Entry Point: 0x00000000
2184 To verify the contents of the image (or check for corruption):
2186 -> tools/mkimage -l examples/uImage.TQM850L
2187 Image Name: 2.4.4 kernel for TQM850L
2188 Created: Wed Jul 19 02:34:59 2000
2189 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2190 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2191 Load Address: 0x00000000
2192 Entry Point: 0x00000000
2194 NOTE: for embedded systems where boot time is critical you can trade
2195 speed for memory and install an UNCOMPRESSED image instead: this
2196 needs more space in Flash, but boots much faster since it does not
2197 need to be uncompressed:
2199 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
2200 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2201 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
2202 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
2203 > examples/uImage.TQM850L-uncompressed
2204 Image Name: 2.4.4 kernel for TQM850L
2205 Created: Wed Jul 19 02:34:59 2000
2206 Image Type: PowerPC Linux Kernel Image (uncompressed)
2207 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
2208 Load Address: 0x00000000
2209 Entry Point: 0x00000000
2212 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
2213 when your kernel is intended to use an initial ramdisk:
2215 -> tools/mkimage -n 'Simple Ramdisk Image' \
2216 > -A ppc -O linux -T ramdisk -C gzip \
2217 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
2218 Image Name: Simple Ramdisk Image
2219 Created: Wed Jan 12 14:01:50 2000
2220 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2221 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
2222 Load Address: 0x00000000
2223 Entry Point: 0x00000000
2225 The "dumpimage" tool can be used to disassemble or list the contents of images
2226 built by mkimage. See dumpimage's help output (-h) for details.
2228 Installing a Linux Image:
2229 -------------------------
2231 To downloading a U-Boot image over the serial (console) interface,
2232 you must convert the image to S-Record format:
2234 objcopy -I binary -O srec examples/image examples/image.srec
2236 The 'objcopy' does not understand the information in the U-Boot
2237 image header, so the resulting S-Record file will be relative to
2238 address 0x00000000. To load it to a given address, you need to
2239 specify the target address as 'offset' parameter with the 'loads'
2242 Example: install the image to address 0x40100000 (which on the
2243 TQM8xxL is in the first Flash bank):
2245 => erase 40100000 401FFFFF
2251 ## Ready for S-Record download ...
2252 ~>examples/image.srec
2253 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
2255 15989 15990 15991 15992
2256 [file transfer complete]
2258 ## Start Addr = 0x00000000
2261 You can check the success of the download using the 'iminfo' command;
2262 this includes a checksum verification so you can be sure no data
2263 corruption happened:
2267 ## Checking Image at 40100000 ...
2268 Image Name: 2.2.13 for initrd on TQM850L
2269 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2270 Data Size: 335725 Bytes = 327 kB = 0 MB
2271 Load Address: 00000000
2272 Entry Point: 0000000c
2273 Verifying Checksum ... OK
2279 The "bootm" command is used to boot an application that is stored in
2280 memory (RAM or Flash). In case of a Linux kernel image, the contents
2281 of the "bootargs" environment variable is passed to the kernel as
2282 parameters. You can check and modify this variable using the
2283 "printenv" and "setenv" commands:
2286 => printenv bootargs
2287 bootargs=root=/dev/ram
2289 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2291 => printenv bootargs
2292 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2295 ## Booting Linux kernel at 40020000 ...
2296 Image Name: 2.2.13 for NFS on TQM850L
2297 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2298 Data Size: 381681 Bytes = 372 kB = 0 MB
2299 Load Address: 00000000
2300 Entry Point: 0000000c
2301 Verifying Checksum ... OK
2302 Uncompressing Kernel Image ... OK
2303 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
2304 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2305 time_init: decrementer frequency = 187500000/60
2306 Calibrating delay loop... 49.77 BogoMIPS
2307 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
2310 If you want to boot a Linux kernel with initial RAM disk, you pass
2311 the memory addresses of both the kernel and the initrd image (PPBCOOT
2312 format!) to the "bootm" command:
2314 => imi 40100000 40200000
2316 ## Checking Image at 40100000 ...
2317 Image Name: 2.2.13 for initrd on TQM850L
2318 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2319 Data Size: 335725 Bytes = 327 kB = 0 MB
2320 Load Address: 00000000
2321 Entry Point: 0000000c
2322 Verifying Checksum ... OK
2324 ## Checking Image at 40200000 ...
2325 Image Name: Simple Ramdisk Image
2326 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2327 Data Size: 566530 Bytes = 553 kB = 0 MB
2328 Load Address: 00000000
2329 Entry Point: 00000000
2330 Verifying Checksum ... OK
2332 => bootm 40100000 40200000
2333 ## Booting Linux kernel at 40100000 ...
2334 Image Name: 2.2.13 for initrd on TQM850L
2335 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2336 Data Size: 335725 Bytes = 327 kB = 0 MB
2337 Load Address: 00000000
2338 Entry Point: 0000000c
2339 Verifying Checksum ... OK
2340 Uncompressing Kernel Image ... OK
2341 ## Loading RAMDisk Image at 40200000 ...
2342 Image Name: Simple Ramdisk Image
2343 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2344 Data Size: 566530 Bytes = 553 kB = 0 MB
2345 Load Address: 00000000
2346 Entry Point: 00000000
2347 Verifying Checksum ... OK
2348 Loading Ramdisk ... OK
2349 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
2350 Boot arguments: root=/dev/ram
2351 time_init: decrementer frequency = 187500000/60
2352 Calibrating delay loop... 49.77 BogoMIPS
2354 RAMDISK: Compressed image found at block 0
2355 VFS: Mounted root (ext2 filesystem).
2359 Boot Linux and pass a flat device tree:
2362 First, U-Boot must be compiled with the appropriate defines. See the section
2363 titled "Linux Kernel Interface" above for a more in depth explanation. The
2364 following is an example of how to start a kernel and pass an updated
2370 oft=oftrees/mpc8540ads.dtb
2371 => tftp $oftaddr $oft
2372 Speed: 1000, full duplex
2374 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
2375 Filename 'oftrees/mpc8540ads.dtb'.
2376 Load address: 0x300000
2379 Bytes transferred = 4106 (100a hex)
2380 => tftp $loadaddr $bootfile
2381 Speed: 1000, full duplex
2383 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
2385 Load address: 0x200000
2386 Loading:############
2388 Bytes transferred = 1029407 (fb51f hex)
2393 => bootm $loadaddr - $oftaddr
2394 ## Booting image at 00200000 ...
2395 Image Name: Linux-2.6.17-dirty
2396 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2397 Data Size: 1029343 Bytes = 1005.2 kB
2398 Load Address: 00000000
2399 Entry Point: 00000000
2400 Verifying Checksum ... OK
2401 Uncompressing Kernel Image ... OK
2402 Booting using flat device tree at 0x300000
2403 Using MPC85xx ADS machine description
2404 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
2408 More About U-Boot Image Types:
2409 ------------------------------
2411 U-Boot supports the following image types:
2413 "Standalone Programs" are directly runnable in the environment
2414 provided by U-Boot; it is expected that (if they behave
2415 well) you can continue to work in U-Boot after return from
2416 the Standalone Program.
2417 "OS Kernel Images" are usually images of some Embedded OS which
2418 will take over control completely. Usually these programs
2419 will install their own set of exception handlers, device
2420 drivers, set up the MMU, etc. - this means, that you cannot
2421 expect to re-enter U-Boot except by resetting the CPU.
2422 "RAMDisk Images" are more or less just data blocks, and their
2423 parameters (address, size) are passed to an OS kernel that is
2425 "Multi-File Images" contain several images, typically an OS
2426 (Linux) kernel image and one or more data images like
2427 RAMDisks. This construct is useful for instance when you want
2428 to boot over the network using BOOTP etc., where the boot
2429 server provides just a single image file, but you want to get
2430 for instance an OS kernel and a RAMDisk image.
2432 "Multi-File Images" start with a list of image sizes, each
2433 image size (in bytes) specified by an "uint32_t" in network
2434 byte order. This list is terminated by an "(uint32_t)0".
2435 Immediately after the terminating 0 follow the images, one by
2436 one, all aligned on "uint32_t" boundaries (size rounded up to
2437 a multiple of 4 bytes).
2439 "Firmware Images" are binary images containing firmware (like
2440 U-Boot or FPGA images) which usually will be programmed to
2443 "Script files" are command sequences that will be executed by
2444 U-Boot's command interpreter; this feature is especially
2445 useful when you configure U-Boot to use a real shell (hush)
2446 as command interpreter.
2448 Booting the Linux zImage:
2449 -------------------------
2451 On some platforms, it's possible to boot Linux zImage. This is done
2452 using the "bootz" command. The syntax of "bootz" command is the same
2453 as the syntax of "bootm" command.
2455 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
2456 kernel with raw initrd images. The syntax is slightly different, the
2457 address of the initrd must be augmented by it's size, in the following
2458 format: "<initrd addres>:<initrd size>".
2464 One of the features of U-Boot is that you can dynamically load and
2465 run "standalone" applications, which can use some resources of
2466 U-Boot like console I/O functions or interrupt services.
2468 Two simple examples are included with the sources:
2473 'examples/hello_world.c' contains a small "Hello World" Demo
2474 application; it is automatically compiled when you build U-Boot.
2475 It's configured to run at address 0x00040004, so you can play with it
2479 ## Ready for S-Record download ...
2480 ~>examples/hello_world.srec
2481 1 2 3 4 5 6 7 8 9 10 11 ...
2482 [file transfer complete]
2484 ## Start Addr = 0x00040004
2486 => go 40004 Hello World! This is a test.
2487 ## Starting application at 0x00040004 ...
2498 Hit any key to exit ...
2500 ## Application terminated, rc = 0x0
2502 Another example, which demonstrates how to register a CPM interrupt
2503 handler with the U-Boot code, can be found in 'examples/timer.c'.
2504 Here, a CPM timer is set up to generate an interrupt every second.
2505 The interrupt service routine is trivial, just printing a '.'
2506 character, but this is just a demo program. The application can be
2507 controlled by the following keys:
2509 ? - print current values og the CPM Timer registers
2510 b - enable interrupts and start timer
2511 e - stop timer and disable interrupts
2512 q - quit application
2515 ## Ready for S-Record download ...
2516 ~>examples/timer.srec
2517 1 2 3 4 5 6 7 8 9 10 11 ...
2518 [file transfer complete]
2520 ## Start Addr = 0x00040004
2523 ## Starting application at 0x00040004 ...
2526 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
2529 [q, b, e, ?] Set interval 1000000 us
2532 [q, b, e, ?] ........
2533 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
2536 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
2539 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
2542 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
2544 [q, b, e, ?] ...Stopping timer
2546 [q, b, e, ?] ## Application terminated, rc = 0x0
2552 Over time, many people have reported problems when trying to use the
2553 "minicom" terminal emulation program for serial download. I (wd)
2554 consider minicom to be broken, and recommend not to use it. Under
2555 Unix, I recommend to use C-Kermit for general purpose use (and
2556 especially for kermit binary protocol download ("loadb" command), and
2557 use "cu" for S-Record download ("loads" command). See
2558 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
2559 for help with kermit.
2562 Nevertheless, if you absolutely want to use it try adding this
2563 configuration to your "File transfer protocols" section:
2565 Name Program Name U/D FullScr IO-Red. Multi
2566 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
2567 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
2573 Starting at version 0.9.2, U-Boot supports NetBSD both as host
2574 (build U-Boot) and target system (boots NetBSD/mpc8xx).
2576 Building requires a cross environment; it is known to work on
2577 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
2578 need gmake since the Makefiles are not compatible with BSD make).
2579 Note that the cross-powerpc package does not install include files;
2580 attempting to build U-Boot will fail because <machine/ansi.h> is
2581 missing. This file has to be installed and patched manually:
2583 # cd /usr/pkg/cross/powerpc-netbsd/include
2585 # ln -s powerpc machine
2586 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
2587 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
2589 Native builds *don't* work due to incompatibilities between native
2590 and U-Boot include files.
2592 Booting assumes that (the first part of) the image booted is a
2593 stage-2 loader which in turn loads and then invokes the kernel
2594 proper. Loader sources will eventually appear in the NetBSD source
2595 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
2596 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
2599 Implementation Internals:
2600 =========================
2602 The following is not intended to be a complete description of every
2603 implementation detail. However, it should help to understand the
2604 inner workings of U-Boot and make it easier to port it to custom
2608 Initial Stack, Global Data:
2609 ---------------------------
2611 The implementation of U-Boot is complicated by the fact that U-Boot
2612 starts running out of ROM (flash memory), usually without access to
2613 system RAM (because the memory controller is not initialized yet).
2614 This means that we don't have writable Data or BSS segments, and BSS
2615 is not initialized as zero. To be able to get a C environment working
2616 at all, we have to allocate at least a minimal stack. Implementation
2617 options for this are defined and restricted by the CPU used: Some CPU
2618 models provide on-chip memory (like the IMMR area on MPC8xx and
2619 MPC826x processors), on others (parts of) the data cache can be
2620 locked as (mis-) used as memory, etc.
2622 Chris Hallinan posted a good summary of these issues to the
2623 U-Boot mailing list:
2625 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
2626 From: "Chris Hallinan" <clh@net1plus.com>
2627 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
2630 Correct me if I'm wrong, folks, but the way I understand it
2631 is this: Using DCACHE as initial RAM for Stack, etc, does not
2632 require any physical RAM backing up the cache. The cleverness
2633 is that the cache is being used as a temporary supply of
2634 necessary storage before the SDRAM controller is setup. It's
2635 beyond the scope of this list to explain the details, but you
2636 can see how this works by studying the cache architecture and
2637 operation in the architecture and processor-specific manuals.
2639 OCM is On Chip Memory, which I believe the 405GP has 4K. It
2640 is another option for the system designer to use as an
2641 initial stack/RAM area prior to SDRAM being available. Either
2642 option should work for you. Using CS 4 should be fine if your
2643 board designers haven't used it for something that would
2644 cause you grief during the initial boot! It is frequently not
2647 CFG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
2648 with your processor/board/system design. The default value
2649 you will find in any recent u-boot distribution in
2650 walnut.h should work for you. I'd set it to a value larger
2651 than your SDRAM module. If you have a 64MB SDRAM module, set
2652 it above 400_0000. Just make sure your board has no resources
2653 that are supposed to respond to that address! That code in
2654 start.S has been around a while and should work as is when
2655 you get the config right.
2660 It is essential to remember this, since it has some impact on the C
2661 code for the initialization procedures:
2663 * Initialized global data (data segment) is read-only. Do not attempt
2666 * Do not use any uninitialized global data (or implicitly initialized
2667 as zero data - BSS segment) at all - this is undefined, initiali-
2668 zation is performed later (when relocating to RAM).
2670 * Stack space is very limited. Avoid big data buffers or things like
2673 Having only the stack as writable memory limits means we cannot use
2674 normal global data to share information between the code. But it
2675 turned out that the implementation of U-Boot can be greatly
2676 simplified by making a global data structure (gd_t) available to all
2677 functions. We could pass a pointer to this data as argument to _all_
2678 functions, but this would bloat the code. Instead we use a feature of
2679 the GCC compiler (Global Register Variables) to share the data: we
2680 place a pointer (gd) to the global data into a register which we
2681 reserve for this purpose.
2683 When choosing a register for such a purpose we are restricted by the
2684 relevant (E)ABI specifications for the current architecture, and by
2685 GCC's implementation.
2687 For PowerPC, the following registers have specific use:
2689 R2: reserved for system use
2690 R3-R4: parameter passing and return values
2691 R5-R10: parameter passing
2692 R13: small data area pointer
2696 (U-Boot also uses R12 as internal GOT pointer. r12
2697 is a volatile register so r12 needs to be reset when
2698 going back and forth between asm and C)
2700 ==> U-Boot will use R2 to hold a pointer to the global data
2702 Note: on PPC, we could use a static initializer (since the
2703 address of the global data structure is known at compile time),
2704 but it turned out that reserving a register results in somewhat
2705 smaller code - although the code savings are not that big (on
2706 average for all boards 752 bytes for the whole U-Boot image,
2707 624 text + 127 data).
2709 On ARM, the following registers are used:
2711 R0: function argument word/integer result
2712 R1-R3: function argument word
2713 R9: platform specific
2714 R10: stack limit (used only if stack checking is enabled)
2715 R11: argument (frame) pointer
2716 R12: temporary workspace
2719 R15: program counter
2721 ==> U-Boot will use R9 to hold a pointer to the global data
2723 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
2725 On Nios II, the ABI is documented here:
2726 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
2728 ==> U-Boot will use gp to hold a pointer to the global data
2730 Note: on Nios II, we give "-G0" option to gcc and don't use gp
2731 to access small data sections, so gp is free.
2733 On RISC-V, the following registers are used:
2735 x0: hard-wired zero (zero)
2736 x1: return address (ra)
2737 x2: stack pointer (sp)
2738 x3: global pointer (gp)
2739 x4: thread pointer (tp)
2740 x5: link register (t0)
2741 x8: frame pointer (fp)
2742 x10-x11: arguments/return values (a0-1)
2743 x12-x17: arguments (a2-7)
2744 x28-31: temporaries (t3-6)
2745 pc: program counter (pc)
2747 ==> U-Boot will use gp to hold a pointer to the global data
2752 U-Boot runs in system state and uses physical addresses, i.e. the
2753 MMU is not used either for address mapping nor for memory protection.
2755 The available memory is mapped to fixed addresses using the memory
2756 controller. In this process, a contiguous block is formed for each
2757 memory type (Flash, SDRAM, SRAM), even when it consists of several
2758 physical memory banks.
2760 U-Boot is installed in the first 128 kB of the first Flash bank (on
2761 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
2762 booting and sizing and initializing DRAM, the code relocates itself
2763 to the upper end of DRAM. Immediately below the U-Boot code some
2764 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
2765 configuration setting]. Below that, a structure with global Board
2766 Info data is placed, followed by the stack (growing downward).
2768 Additionally, some exception handler code is copied to the low 8 kB
2769 of DRAM (0x00000000 ... 0x00001FFF).
2771 So a typical memory configuration with 16 MB of DRAM could look like
2774 0x0000 0000 Exception Vector code
2777 0x0000 2000 Free for Application Use
2783 0x00FB FF20 Monitor Stack (Growing downward)
2784 0x00FB FFAC Board Info Data and permanent copy of global data
2785 0x00FC 0000 Malloc Arena
2788 0x00FE 0000 RAM Copy of Monitor Code
2789 ... eventually: LCD or video framebuffer
2790 ... eventually: pRAM (Protected RAM - unchanged by reset)
2791 0x00FF FFFF [End of RAM]
2794 System Initialization:
2795 ----------------------
2797 In the reset configuration, U-Boot starts at the reset entry point
2798 (on most PowerPC systems at address 0x00000100). Because of the reset
2799 configuration for CS0# this is a mirror of the on board Flash memory.
2800 To be able to re-map memory U-Boot then jumps to its link address.
2801 To be able to implement the initialization code in C, a (small!)
2802 initial stack is set up in the internal Dual Ported RAM (in case CPUs
2803 which provide such a feature like), or in a locked part of the data
2804 cache. After that, U-Boot initializes the CPU core, the caches and
2807 Next, all (potentially) available memory banks are mapped using a
2808 preliminary mapping. For example, we put them on 512 MB boundaries
2809 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
2810 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
2811 programmed for SDRAM access. Using the temporary configuration, a
2812 simple memory test is run that determines the size of the SDRAM
2815 When there is more than one SDRAM bank, and the banks are of
2816 different size, the largest is mapped first. For equal size, the first
2817 bank (CS2#) is mapped first. The first mapping is always for address
2818 0x00000000, with any additional banks following immediately to create
2819 contiguous memory starting from 0.
2821 Then, the monitor installs itself at the upper end of the SDRAM area
2822 and allocates memory for use by malloc() and for the global Board
2823 Info data; also, the exception vector code is copied to the low RAM
2824 pages, and the final stack is set up.
2826 Only after this relocation will you have a "normal" C environment;
2827 until that you are restricted in several ways, mostly because you are
2828 running from ROM, and because the code will have to be relocated to a
2832 U-Boot Porting Guide:
2833 ----------------------
2835 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
2839 int main(int argc, char *argv[])
2841 sighandler_t no_more_time;
2843 signal(SIGALRM, no_more_time);
2844 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
2846 if (available_money > available_manpower) {
2847 Pay consultant to port U-Boot;
2851 Download latest U-Boot source;
2853 Subscribe to u-boot mailing list;
2856 email("Hi, I am new to U-Boot, how do I get started?");
2859 Read the README file in the top level directory;
2860 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
2861 Read applicable doc/README.*;
2862 Read the source, Luke;
2863 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
2866 if (available_money > toLocalCurrency ($2500))
2869 Add a lot of aggravation and time;
2871 if (a similar board exists) { /* hopefully... */
2872 cp -a board/<similar> board/<myboard>
2873 cp include/configs/<similar>.h include/configs/<myboard>.h
2875 Create your own board support subdirectory;
2876 Create your own board include/configs/<myboard>.h file;
2878 Edit new board/<myboard> files
2879 Edit new include/configs/<myboard>.h
2884 Add / modify source code;
2888 email("Hi, I am having problems...");
2890 Send patch file to the U-Boot email list;
2891 if (reasonable critiques)
2892 Incorporate improvements from email list code review;
2894 Defend code as written;
2900 void no_more_time (int sig)
2909 All contributions to U-Boot should conform to the Linux kernel
2910 coding style; see the kernel coding style guide at
2911 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
2912 script "scripts/Lindent" in your Linux kernel source directory.
2914 Source files originating from a different project (for example the
2915 MTD subsystem) are generally exempt from these guidelines and are not
2916 reformatted to ease subsequent migration to newer versions of those
2919 Please note that U-Boot is implemented in C (and to some small parts in
2920 Assembler); no C++ is used, so please do not use C++ style comments (//)
2923 Please also stick to the following formatting rules:
2924 - remove any trailing white space
2925 - use TAB characters for indentation and vertical alignment, not spaces
2926 - make sure NOT to use DOS '\r\n' line feeds
2927 - do not add more than 2 consecutive empty lines to source files
2928 - do not add trailing empty lines to source files
2930 Submissions which do not conform to the standards may be returned
2931 with a request to reformat the changes.
2937 Since the number of patches for U-Boot is growing, we need to
2938 establish some rules. Submissions which do not conform to these rules
2939 may be rejected, even when they contain important and valuable stuff.
2941 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
2943 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
2944 see https://lists.denx.de/listinfo/u-boot
2946 When you send a patch, please include the following information with
2949 * For bug fixes: a description of the bug and how your patch fixes
2950 this bug. Please try to include a way of demonstrating that the
2951 patch actually fixes something.
2953 * For new features: a description of the feature and your
2956 * For major contributions, add a MAINTAINERS file with your
2957 information and associated file and directory references.
2959 * When you add support for a new board, don't forget to add a
2960 maintainer e-mail address to the boards.cfg file, too.
2962 * If your patch adds new configuration options, don't forget to
2963 document these in the README file.
2965 * The patch itself. If you are using git (which is *strongly*
2966 recommended) you can easily generate the patch using the
2967 "git format-patch". If you then use "git send-email" to send it to
2968 the U-Boot mailing list, you will avoid most of the common problems
2969 with some other mail clients.
2971 If you cannot use git, use "diff -purN OLD NEW". If your version of
2972 diff does not support these options, then get the latest version of
2975 The current directory when running this command shall be the parent
2976 directory of the U-Boot source tree (i. e. please make sure that
2977 your patch includes sufficient directory information for the
2980 We prefer patches as plain text. MIME attachments are discouraged,
2981 and compressed attachments must not be used.
2983 * If one logical set of modifications affects or creates several
2984 files, all these changes shall be submitted in a SINGLE patch file.
2986 * Changesets that contain different, unrelated modifications shall be
2987 submitted as SEPARATE patches, one patch per changeset.
2992 * Before sending the patch, run the buildman script on your patched
2993 source tree and make sure that no errors or warnings are reported
2994 for any of the boards.
2996 * Keep your modifications to the necessary minimum: A patch
2997 containing several unrelated changes or arbitrary reformats will be
2998 returned with a request to re-formatting / split it.
3000 * If you modify existing code, make sure that your new code does not
3001 add to the memory footprint of the code ;-) Small is beautiful!
3002 When adding new features, these should compile conditionally only
3003 (using #ifdef), and the resulting code with the new feature
3004 disabled must not need more memory than the old code without your
3007 * Remember that there is a size limit of 100 kB per message on the
3008 u-boot mailing list. Bigger patches will be moderated. If they are
3009 reasonable and not too big, they will be acknowledged. But patches
3010 bigger than the size limit should be avoided.