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:
378 New kernel versions are expecting firmware settings to be
379 passed using flattened device trees (based on open firmware
383 * New libfdt-based support
384 * Adds the "fdt" command
385 * The bootm command automatically updates the fdt
387 OF_TBCLK - The timebase frequency.
389 boards with QUICC Engines require OF_QE to set UCC MAC
394 U-Boot can detect if an IDE device is present or not.
395 If not, and this new config option is activated, U-Boot
396 removes the ATA node from the DTS before booting Linux,
397 so the Linux IDE driver does not probe the device and
398 crash. This is needed for buggy hardware (uc101) where
399 no pull down resistor is connected to the signal IDE5V_DD7.
401 - vxWorks boot parameters:
403 bootvx constructs a valid bootline using the following
404 environments variables: bootdev, bootfile, ipaddr, netmask,
405 serverip, gatewayip, hostname, othbootargs.
406 It loads the vxWorks image pointed bootfile.
408 Note: If a "bootargs" environment is defined, it will override
409 the defaults discussed just above.
411 - Cache Configuration for ARM:
412 CFG_SYS_PL310_BASE - Physical base address of PL310
413 controller register space
418 If you have Amba PrimeCell PL011 UARTs, set this variable to
419 the clock speed of the UARTs.
423 If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
424 define this to a list of base addresses for each (supported)
425 port. See e.g. include/configs/versatile.h
427 CONFIG_SERIAL_HW_FLOW_CONTROL
429 Define this variable to enable hw flow control in serial driver.
430 Current user of this option is drivers/serial/nsl16550.c driver
432 - Removal of commands
433 If no commands are needed to boot, you can disable
434 CONFIG_CMDLINE to remove them. In this case, the command line
435 will not be available, and when U-Boot wants to execute the
436 boot command (on start-up) it will call board_run_command()
437 instead. This can reduce image size significantly for very
438 simple boot procedures.
440 - Regular expression support:
442 If this variable is defined, U-Boot is linked against
443 the SLRE (Super Light Regular Expression) library,
444 which adds regex support to some commands, as for
445 example "env grep" and "setexpr".
448 CONFIG_SYS_WATCHDOG_FREQ
449 Some platforms automatically call WATCHDOG_RESET()
450 from the timer interrupt handler every
451 CONFIG_SYS_WATCHDOG_FREQ interrupts. If not set by the
452 board configuration file, a default of CONFIG_SYS_HZ/2
453 (i.e. 500) is used. Setting CONFIG_SYS_WATCHDOG_FREQ
454 to 0 disables calling WATCHDOG_RESET() from the timer
458 The CFG_SYS_I2C_PCA953X_WIDTH option specifies a list of
459 chip-ngpio pairs that tell the PCA953X driver the number of
460 pins supported by a particular chip.
462 Note that if the GPIO device uses I2C, then the I2C interface
463 must also be configured. See I2C Support, below.
466 When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
467 accesses and can checksum them or write a list of them out
468 to memory. See the 'iotrace' command for details. This is
469 useful for testing device drivers since it can confirm that
470 the driver behaves the same way before and after a code
471 change. Currently this is supported on sandbox and arm. To
472 add support for your architecture, add '#include <iotrace.h>'
473 to the bottom of arch/<arch>/include/asm/io.h and test.
475 Example output from the 'iotrace stats' command is below.
476 Note that if the trace buffer is exhausted, the checksum will
477 still continue to operate.
480 Start: 10000000 (buffer start address)
481 Size: 00010000 (buffer size)
482 Offset: 00000120 (current buffer offset)
483 Output: 10000120 (start + offset)
484 Count: 00000018 (number of trace records)
485 CRC32: 9526fb66 (CRC32 of all trace records)
489 When CONFIG_TIMESTAMP is selected, the timestamp
490 (date and time) of an image is printed by image
491 commands like bootm or iminfo. This option is
492 automatically enabled when you select CONFIG_CMD_DATE .
494 - Partition Labels (disklabels) Supported:
495 Zero or more of the following:
496 CONFIG_MAC_PARTITION Apple's MacOS partition table.
497 CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
498 CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
499 bootloader. Note 2TB partition limit; see
501 CONFIG_SCSI) you must configure support for at
502 least one non-MTD partition type as well.
504 - NETWORK Support (PCI):
506 Utility code for direct access to the SPI bus on Intel 8257x.
507 This does not do anything useful unless you set at least one
508 of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
511 Support for National dp83815 chips.
514 Support for National dp8382[01] gigabit chips.
516 - NETWORK Support (other):
518 Support for the Calxeda XGMAC device
521 Support for SMSC's LAN91C96 chips.
523 CONFIG_LAN91C96_USE_32_BIT
524 Define this to enable 32 bit addressing
526 CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
527 Define this if you have more then 3 PHYs.
530 Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
532 CONFIG_FTGMAC100_EGIGA
533 Define this to use GE link update with gigabit PHY.
534 Define this if FTGMAC100 is connected to gigabit PHY.
535 If your system has 10/100 PHY only, it might not occur
536 wrong behavior. Because PHY usually return timeout or
537 useless data when polling gigabit status and gigabit
538 control registers. This behavior won't affect the
539 correctnessof 10/100 link speed update.
542 Support for Renesas on-chip Ethernet controller
544 CONFIG_SH_ETHER_USE_PORT
545 Define the number of ports to be used
547 CONFIG_SH_ETHER_PHY_ADDR
548 Define the ETH PHY's address
550 CONFIG_SH_ETHER_CACHE_WRITEBACK
551 If this option is set, the driver enables cache flush.
557 CONFIG_TPM_TIS_INFINEON
558 Support for Infineon i2c bus TPM devices. Only one device
559 per system is supported at this time.
561 CONFIG_TPM_TIS_I2C_BURST_LIMITATION
562 Define the burst count bytes upper limit
565 Support for STMicroelectronics TPM devices. Requires DM_TPM support.
567 CONFIG_TPM_ST33ZP24_I2C
568 Support for STMicroelectronics ST33ZP24 I2C devices.
569 Requires TPM_ST33ZP24 and I2C.
571 CONFIG_TPM_ST33ZP24_SPI
572 Support for STMicroelectronics ST33ZP24 SPI devices.
573 Requires TPM_ST33ZP24 and SPI.
576 Support for Atmel TWI TPM device. Requires I2C support.
579 Support for generic parallel port TPM devices. Only one device
580 per system is supported at this time.
583 Define this to enable the TPM support library which provides
584 functional interfaces to some TPM commands.
585 Requires support for a TPM device.
587 CONFIG_TPM_AUTH_SESSIONS
588 Define this to enable authorized functions in the TPM library.
589 Requires CONFIG_TPM and CONFIG_SHA1.
592 At the moment only the UHCI host controller is
593 supported (PIP405, MIP405); define
594 CONFIG_USB_UHCI to enable it.
595 define CONFIG_USB_KEYBOARD to enable the USB Keyboard
596 and define CONFIG_USB_STORAGE to enable the USB
599 Supported are USB Keyboards and USB Floppy drives
602 CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
606 Define the below if you wish to use the USB console.
607 Once firmware is rebuilt from a serial console issue the
608 command "setenv stdin usbtty; setenv stdout usbtty" and
609 attach your USB cable. The Unix command "dmesg" should print
610 it has found a new device. The environment variable usbtty
611 can be set to gserial or cdc_acm to enable your device to
612 appear to a USB host as a Linux gserial device or a
613 Common Device Class Abstract Control Model serial device.
614 If you select usbtty = gserial you should be able to enumerate
616 # modprobe usbserial vendor=0xVendorID product=0xProductID
617 else if using cdc_acm, simply setting the environment
618 variable usbtty to be cdc_acm should suffice. The following
619 might be defined in YourBoardName.h
622 Define this to enable the high speed support for usb
623 device and usbtty. If this feature is enabled, a routine
624 int is_usbd_high_speed(void)
625 also needs to be defined by the driver to dynamically poll
626 whether the enumeration has succeded at high speed or full
629 If you have a USB-IF assigned VendorID then you may wish to
630 define your own vendor specific values either in BoardName.h
631 or directly in usbd_vendor_info.h. If you don't define
632 CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
633 CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
634 should pretend to be a Linux device to it's target host.
636 CONFIG_USBD_MANUFACTURER
637 Define this string as the name of your company for
638 - CONFIG_USBD_MANUFACTURER "my company"
640 CONFIG_USBD_PRODUCT_NAME
641 Define this string as the name of your product
642 - CONFIG_USBD_PRODUCT_NAME "acme usb device"
645 Define this as your assigned Vendor ID from the USB
646 Implementors Forum. This *must* be a genuine Vendor ID
647 to avoid polluting the USB namespace.
648 - CONFIG_USBD_VENDORID 0xFFFF
650 CONFIG_USBD_PRODUCTID
651 Define this as the unique Product ID
653 - CONFIG_USBD_PRODUCTID 0xFFFF
655 - ULPI Layer Support:
656 The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
657 the generic ULPI layer. The generic layer accesses the ULPI PHY
658 via the platform viewport, so you need both the genric layer and
659 the viewport enabled. Currently only Chipidea/ARC based
660 viewport is supported.
661 To enable the ULPI layer support, define CONFIG_USB_ULPI and
662 CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
663 If your ULPI phy needs a different reference clock than the
664 standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
665 the appropriate value in Hz.
669 Support for Renesas on-chip MMCIF controller
672 Define the base address of MMCIF registers
675 Define the clock frequency for MMCIF
677 - USB Device Firmware Update (DFU) class support:
679 This enables the USB portion of the DFU USB class
682 This enables support for exposing NAND devices via DFU.
685 This enables support for exposing RAM via DFU.
686 Note: DFU spec refer to non-volatile memory usage, but
687 allow usages beyond the scope of spec - here RAM usage,
688 one that would help mostly the developer.
690 CONFIG_SYS_DFU_DATA_BUF_SIZE
691 Dfu transfer uses a buffer before writing data to the
692 raw storage device. Make the size (in bytes) of this buffer
693 configurable. The size of this buffer is also configurable
694 through the "dfu_bufsiz" environment variable.
696 CONFIG_SYS_DFU_MAX_FILE_SIZE
697 When updating files rather than the raw storage device,
698 we use a static buffer to copy the file into and then write
699 the buffer once we've been given the whole file. Define
700 this to the maximum filesize (in bytes) for the buffer.
701 Default is 4 MiB if undefined.
703 DFU_DEFAULT_POLL_TIMEOUT
704 Poll timeout [ms], is the timeout a device can send to the
705 host. The host must wait for this timeout before sending
706 a subsequent DFU_GET_STATUS request to the device.
708 DFU_MANIFEST_POLL_TIMEOUT
709 Poll timeout [ms], which the device sends to the host when
710 entering dfuMANIFEST state. Host waits this timeout, before
711 sending again an USB request to the device.
714 See Kconfig help for available keyboard drivers.
717 CONFIG_PHY_CLOCK_FREQ (ppc4xx)
719 The clock frequency of the MII bus
721 CONFIG_PHY_CMD_DELAY (ppc4xx)
723 Some PHY like Intel LXT971A need extra delay after
724 command issued before MII status register can be read
726 - BOOTP Recovery Mode:
727 CONFIG_BOOTP_RANDOM_DELAY
729 If you have many targets in a network that try to
730 boot using BOOTP, you may want to avoid that all
731 systems send out BOOTP requests at precisely the same
732 moment (which would happen for instance at recovery
733 from a power failure, when all systems will try to
734 boot, thus flooding the BOOTP server. Defining
735 CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
736 inserted before sending out BOOTP requests. The
737 following delays are inserted then:
739 1st BOOTP request: delay 0 ... 1 sec
740 2nd BOOTP request: delay 0 ... 2 sec
741 3rd BOOTP request: delay 0 ... 4 sec
743 BOOTP requests: delay 0 ... 8 sec
745 CONFIG_BOOTP_ID_CACHE_SIZE
747 BOOTP packets are uniquely identified using a 32-bit ID. The
748 server will copy the ID from client requests to responses and
749 U-Boot will use this to determine if it is the destination of
750 an incoming response. Some servers will check that addresses
751 aren't in use before handing them out (usually using an ARP
752 ping) and therefore take up to a few hundred milliseconds to
753 respond. Network congestion may also influence the time it
754 takes for a response to make it back to the client. If that
755 time is too long, U-Boot will retransmit requests. In order
756 to allow earlier responses to still be accepted after these
757 retransmissions, U-Boot's BOOTP client keeps a small cache of
758 IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
759 cache. The default is to keep IDs for up to four outstanding
760 requests. Increasing this will allow U-Boot to accept offers
761 from a BOOTP client in networks with unusually high latency.
763 - DHCP Advanced Options:
765 - Link-local IP address negotiation:
766 Negotiate with other link-local clients on the local network
767 for an address that doesn't require explicit configuration.
768 This is especially useful if a DHCP server cannot be guaranteed
769 to exist in all environments that the device must operate.
771 See doc/README.link-local for more information.
773 - MAC address from environment variables
775 FDT_SEQ_MACADDR_FROM_ENV
777 Fix-up device tree with MAC addresses fetched sequentially from
778 environment variables. This config work on assumption that
779 non-usable ethernet node of device-tree are either not present
780 or their status has been marked as "disabled".
785 The device id used in CDP trigger frames.
787 CONFIG_CDP_DEVICE_ID_PREFIX
789 A two character string which is prefixed to the MAC address
794 A printf format string which contains the ascii name of
795 the port. Normally is set to "eth%d" which sets
796 eth0 for the first Ethernet, eth1 for the second etc.
798 CONFIG_CDP_CAPABILITIES
800 A 32bit integer which indicates the device capabilities;
801 0x00000010 for a normal host which does not forwards.
805 An ascii string containing the version of the software.
809 An ascii string containing the name of the platform.
813 A 32bit integer sent on the trigger.
815 CONFIG_CDP_POWER_CONSUMPTION
817 A 16bit integer containing the power consumption of the
818 device in .1 of milliwatts.
820 CONFIG_CDP_APPLIANCE_VLAN_TYPE
822 A byte containing the id of the VLAN.
824 - Status LED: CONFIG_LED_STATUS
826 Several configurations allow to display the current
827 status using a LED. For instance, the LED will blink
828 fast while running U-Boot code, stop blinking as
829 soon as a reply to a BOOTP request was received, and
830 start blinking slow once the Linux kernel is running
831 (supported by a status LED driver in the Linux
832 kernel). Defining CONFIG_LED_STATUS enables this
837 CONFIG_LED_STATUS_GPIO
838 The status LED can be connected to a GPIO pin.
839 In such cases, the gpio_led driver can be used as a
840 status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
841 to include the gpio_led driver in the U-Boot binary.
843 CONFIG_GPIO_LED_INVERTED_TABLE
844 Some GPIO connected LEDs may have inverted polarity in which
845 case the GPIO high value corresponds to LED off state and
846 GPIO low value corresponds to LED on state.
847 In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
848 with a list of GPIO LEDs that have inverted polarity.
851 CFG_SYS_NUM_I2C_BUSES
852 Hold the number of i2c buses you want to use.
854 CONFIG_SYS_I2C_DIRECT_BUS
855 define this, if you don't use i2c muxes on your hardware.
856 if CFG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
860 define how many muxes are maximal consecutively connected
861 on one i2c bus. If you not use i2c muxes, omit this
865 hold a list of buses you want to use, only used if
866 CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
867 a board with CFG_SYS_I2C_MAX_HOPS = 1 and
868 CFG_SYS_NUM_I2C_BUSES = 9:
870 CFG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \
871 {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
872 {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
873 {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
874 {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
875 {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
876 {1, {I2C_NULL_HOP}}, \
877 {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
878 {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
882 bus 0 on adapter 0 without a mux
883 bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
884 bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
885 bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
886 bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
887 bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
888 bus 6 on adapter 1 without a mux
889 bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
890 bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
892 If you do not have i2c muxes on your board, omit this define.
894 - Legacy I2C Support:
895 If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
896 then the following macros need to be defined (examples are
897 from include/configs/lwmon.h):
901 (Optional). Any commands necessary to enable the I2C
902 controller or configure ports.
904 eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
908 The code necessary to make the I2C data line active
909 (driven). If the data line is open collector, this
912 eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
916 The code necessary to make the I2C data line tri-stated
917 (inactive). If the data line is open collector, this
920 eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
924 Code that returns true if the I2C data line is high,
927 eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
931 If <bit> is true, sets the I2C data line high. If it
932 is false, it clears it (low).
934 eg: #define I2C_SDA(bit) \
935 if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
936 else immr->im_cpm.cp_pbdat &= ~PB_SDA
940 If <bit> is true, sets the I2C clock line high. If it
941 is false, it clears it (low).
943 eg: #define I2C_SCL(bit) \
944 if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
945 else immr->im_cpm.cp_pbdat &= ~PB_SCL
949 This delay is invoked four times per clock cycle so this
950 controls the rate of data transfer. The data rate thus
951 is 1 / (I2C_DELAY * 4). Often defined to be something
954 #define I2C_DELAY udelay(2)
956 CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
958 If your arch supports the generic GPIO framework (asm/gpio.h),
959 then you may alternatively define the two GPIOs that are to be
960 used as SCL / SDA. Any of the previous I2C_xxx macros will
961 have GPIO-based defaults assigned to them as appropriate.
963 You should define these to the GPIO value as given directly to
964 the generic GPIO functions.
968 This option allows the use of multiple I2C buses, each of which
969 must have a controller. At any point in time, only one bus is
970 active. To switch to a different bus, use the 'i2c dev' command.
971 Note that bus numbering is zero-based.
975 This option specifies a list of I2C devices that will be skipped
976 when the 'i2c probe' command is issued.
979 #define CFG_SYS_I2C_NOPROBES {0x50,0x68}
981 will skip addresses 0x50 and 0x68 on a board with one I2C bus
985 If defined, then this indicates the I2C bus number for the RTC.
986 If not defined, then U-Boot assumes that RTC is on I2C bus 0.
988 CONFIG_SOFT_I2C_READ_REPEATED_START
990 defining this will force the i2c_read() function in
991 the soft_i2c driver to perform an I2C repeated start
992 between writing the address pointer and reading the
993 data. If this define is omitted the default behaviour
994 of doing a stop-start sequence will be used. Most I2C
995 devices can use either method, but some require one or
998 - SPI Support: CONFIG_SPI
1000 Enables SPI driver (so far only tested with
1001 SPI EEPROM, also an instance works with Crystal A/D and
1002 D/As on the SACSng board)
1004 CONFIG_SYS_SPI_MXC_WAIT
1005 Timeout for waiting until spi transfer completed.
1006 default: (CONFIG_SYS_HZ/100) /* 10 ms */
1008 - FPGA Support: CONFIG_FPGA
1010 Enables FPGA subsystem.
1012 CONFIG_FPGA_<vendor>
1014 Enables support for specific chip vendors.
1017 CONFIG_FPGA_<family>
1019 Enables support for FPGA family.
1020 (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1022 CONFIG_SYS_FPGA_CHECK_BUSY
1024 Enable checks on FPGA configuration interface busy
1025 status by the configuration function. This option
1026 will require a board or device specific function to
1031 If defined, a function that provides delays in the FPGA
1032 configuration driver.
1034 CONFIG_SYS_FPGA_CHECK_ERROR
1036 Check for configuration errors during FPGA bitfile
1037 loading. For example, abort during Virtex II
1038 configuration if the INIT_B line goes low (which
1039 indicated a CRC error).
1041 CFG_SYS_FPGA_WAIT_INIT
1043 Maximum time to wait for the INIT_B line to de-assert
1044 after PROB_B has been de-asserted during a Virtex II
1045 FPGA configuration sequence. The default time is 500
1048 CFG_SYS_FPGA_WAIT_BUSY
1050 Maximum time to wait for BUSY to de-assert during
1051 Virtex II FPGA configuration. The default is 5 ms.
1053 CFG_SYS_FPGA_WAIT_CONFIG
1055 Time to wait after FPGA configuration. The default is
1058 - Vendor Parameter Protection:
1060 U-Boot considers the values of the environment
1061 variables "serial#" (Board Serial Number) and
1062 "ethaddr" (Ethernet Address) to be parameters that
1063 are set once by the board vendor / manufacturer, and
1064 protects these variables from casual modification by
1065 the user. Once set, these variables are read-only,
1066 and write or delete attempts are rejected. You can
1067 change this behaviour:
1069 If CONFIG_ENV_OVERWRITE is #defined in your config
1070 file, the write protection for vendor parameters is
1071 completely disabled. Anybody can change or delete
1074 Alternatively, if you define _both_ an ethaddr in the
1075 default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1076 Ethernet address is installed in the environment,
1077 which can be changed exactly ONCE by the user. [The
1078 serial# is unaffected by this, i. e. it remains
1081 The same can be accomplished in a more flexible way
1082 for any variable by configuring the type of access
1083 to allow for those variables in the ".flags" variable
1084 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1089 Define this variable to enable the reservation of
1090 "protected RAM", i. e. RAM which is not overwritten
1091 by U-Boot. Define CONFIG_PRAM to hold the number of
1092 kB you want to reserve for pRAM. You can overwrite
1093 this default value by defining an environment
1094 variable "pram" to the number of kB you want to
1095 reserve. Note that the board info structure will
1096 still show the full amount of RAM. If pRAM is
1097 reserved, a new environment variable "mem" will
1098 automatically be defined to hold the amount of
1099 remaining RAM in a form that can be passed as boot
1100 argument to Linux, for instance like that:
1102 setenv bootargs ... mem=\${mem}
1105 This way you can tell Linux not to use this memory,
1106 either, which results in a memory region that will
1107 not be affected by reboots.
1109 *WARNING* If your board configuration uses automatic
1110 detection of the RAM size, you must make sure that
1111 this memory test is non-destructive. So far, the
1112 following board configurations are known to be
1115 IVMS8, IVML24, SPD8xx,
1116 HERMES, IP860, RPXlite, LWMON,
1122 In the current implementation, the local variables
1123 space and global environment variables space are
1124 separated. Local variables are those you define by
1125 simply typing `name=value'. To access a local
1126 variable later on, you have write `$name' or
1127 `${name}'; to execute the contents of a variable
1128 directly type `$name' at the command prompt.
1130 Global environment variables are those you use
1131 setenv/printenv to work with. To run a command stored
1132 in such a variable, you need to use the run command,
1133 and you must not use the '$' sign to access them.
1135 To store commands and special characters in a
1136 variable, please use double quotation marks
1137 surrounding the whole text of the variable, instead
1138 of the backslashes before semicolons and special
1141 - Default Environment:
1142 CONFIG_EXTRA_ENV_SETTINGS
1144 Define this to contain any number of null terminated
1145 strings (variable = value pairs) that will be part of
1146 the default environment compiled into the boot image.
1148 For example, place something like this in your
1149 board's config file:
1151 #define CONFIG_EXTRA_ENV_SETTINGS \
1155 Warning: This method is based on knowledge about the
1156 internal format how the environment is stored by the
1157 U-Boot code. This is NOT an official, exported
1158 interface! Although it is unlikely that this format
1159 will change soon, there is no guarantee either.
1160 You better know what you are doing here.
1162 Note: overly (ab)use of the default environment is
1163 discouraged. Make sure to check other ways to preset
1164 the environment like the "source" command or the
1167 CONFIG_DELAY_ENVIRONMENT
1169 Normally the environment is loaded when the board is
1170 initialised so that it is available to U-Boot. This inhibits
1171 that so that the environment is not available until
1172 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1173 this is instead controlled by the value of
1174 /config/load-environment.
1176 CONFIG_STANDALONE_LOAD_ADDR
1178 This option defines a board specific value for the
1179 address where standalone program gets loaded, thus
1180 overwriting the architecture dependent default
1183 - Automatic software updates via TFTP server
1185 CONFIG_UPDATE_TFTP_CNT_MAX
1186 CONFIG_UPDATE_TFTP_MSEC_MAX
1188 These options enable and control the auto-update feature;
1189 for a more detailed description refer to doc/README.update.
1191 - MTD Support (mtdparts command, UBI support)
1192 CONFIG_MTD_UBI_WL_THRESHOLD
1193 This parameter defines the maximum difference between the highest
1194 erase counter value and the lowest erase counter value of eraseblocks
1195 of UBI devices. When this threshold is exceeded, UBI starts performing
1196 wear leveling by means of moving data from eraseblock with low erase
1197 counter to eraseblocks with high erase counter.
1199 The default value should be OK for SLC NAND flashes, NOR flashes and
1200 other flashes which have eraseblock life-cycle 100000 or more.
1201 However, in case of MLC NAND flashes which typically have eraseblock
1202 life-cycle less than 10000, the threshold should be lessened (e.g.,
1203 to 128 or 256, although it does not have to be power of 2).
1207 CONFIG_MTD_UBI_BEB_LIMIT
1208 This option specifies the maximum bad physical eraseblocks UBI
1209 expects on the MTD device (per 1024 eraseblocks). If the
1210 underlying flash does not admit of bad eraseblocks (e.g. NOR
1211 flash), this value is ignored.
1213 NAND datasheets often specify the minimum and maximum NVM
1214 (Number of Valid Blocks) for the flashes' endurance lifetime.
1215 The maximum expected bad eraseblocks per 1024 eraseblocks
1216 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1217 which gives 20 for most NANDs (MaxNVB is basically the total
1218 count of eraseblocks on the chip).
1220 To put it differently, if this value is 20, UBI will try to
1221 reserve about 1.9% of physical eraseblocks for bad blocks
1222 handling. And that will be 1.9% of eraseblocks on the entire
1223 NAND chip, not just the MTD partition UBI attaches. This means
1224 that if you have, say, a NAND flash chip admits maximum 40 bad
1225 eraseblocks, and it is split on two MTD partitions of the same
1226 size, UBI will reserve 40 eraseblocks when attaching a
1231 CONFIG_MTD_UBI_FASTMAP
1232 Fastmap is a mechanism which allows attaching an UBI device
1233 in nearly constant time. Instead of scanning the whole MTD device it
1234 only has to locate a checkpoint (called fastmap) on the device.
1235 The on-flash fastmap contains all information needed to attach
1236 the device. Using fastmap makes only sense on large devices where
1237 attaching by scanning takes long. UBI will not automatically install
1238 a fastmap on old images, but you can set the UBI parameter
1239 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1240 that fastmap-enabled images are still usable with UBI implementations
1241 without fastmap support. On typical flash devices the whole fastmap
1242 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1244 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1245 Set this parameter to enable fastmap automatically on images
1249 CONFIG_MTD_UBI_FM_DEBUG
1250 Enable UBI fastmap debug
1255 Enable building of SPL globally.
1257 CONFIG_SPL_PANIC_ON_RAW_IMAGE
1258 When defined, SPL will panic() if the image it has
1259 loaded does not have a signature.
1260 Defining this is useful when code which loads images
1261 in SPL cannot guarantee that absolutely all read errors
1263 An example is the LPC32XX MLC NAND driver, which will
1264 consider that a completely unreadable NAND block is bad,
1265 and thus should be skipped silently.
1267 CONFIG_SPL_DISPLAY_PRINT
1268 For ARM, enable an optional function to print more information
1269 about the running system.
1271 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
1272 Set this for NAND SPL on PPC mpc83xx targets, so that
1273 start.S waits for the rest of the SPL to load before
1274 continuing (the hardware starts execution after just
1275 loading the first page rather than the full 4K).
1278 Support for a lightweight UBI (fastmap) scanner and
1281 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
1282 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
1283 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
1284 CFG_SYS_NAND_ECCPOS, CFG_SYS_NAND_ECCSIZE,
1285 CFG_SYS_NAND_ECCBYTES
1286 Defines the size and behavior of the NAND that SPL uses
1289 CFG_SYS_NAND_U_BOOT_DST
1290 Location in memory to load U-Boot to
1292 CFG_SYS_NAND_U_BOOT_SIZE
1293 Size of image to load
1295 CFG_SYS_NAND_U_BOOT_START
1296 Entry point in loaded image to jump to
1298 CONFIG_SPL_RAM_DEVICE
1299 Support for running image already present in ram, in SPL binary
1301 CONFIG_SPL_FIT_PRINT
1302 Printing information about a FIT image adds quite a bit of
1303 code to SPL. So this is normally disabled in SPL. Use this
1304 option to re-enable it. This will affect the output of the
1305 bootm command when booting a FIT image.
1307 - Interrupt support (PPC):
1309 There are common interrupt_init() and timer_interrupt()
1310 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
1311 for CPU specific initialization. interrupt_init_cpu()
1312 should set decrementer_count to appropriate value. If
1313 CPU resets decrementer automatically after interrupt
1314 (ppc4xx) it should set decrementer_count to zero.
1315 timer_interrupt() calls timer_interrupt_cpu() for CPU
1316 specific handling. If board has watchdog / status_led
1317 / other_activity_monitor it works automatically from
1318 general timer_interrupt().
1321 Board initialization settings:
1322 ------------------------------
1324 During Initialization u-boot calls a number of board specific functions
1325 to allow the preparation of board specific prerequisites, e.g. pin setup
1326 before drivers are initialized. To enable these callbacks the
1327 following configuration macros have to be defined. Currently this is
1328 architecture specific, so please check arch/your_architecture/lib/board.c
1329 typically in board_init_f() and board_init_r().
1331 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
1332 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
1333 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
1335 Configuration Settings:
1336 -----------------------
1338 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
1339 Optionally it can be defined to support 64-bit memory commands.
1341 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
1342 undefine this when you're short of memory.
1344 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
1345 width of the commands listed in the 'help' command output.
1347 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
1348 prompt for user input.
1350 - CFG_SYS_BAUDRATE_TABLE:
1351 List of legal baudrate settings for this board.
1353 - CFG_SYS_MEM_RESERVE_SECURE
1354 Only implemented for ARMv8 for now.
1355 If defined, the size of CFG_SYS_MEM_RESERVE_SECURE memory
1356 is substracted from total RAM and won't be reported to OS.
1357 This memory can be used as secure memory. A variable
1358 gd->arch.secure_ram is used to track the location. In systems
1359 the RAM base is not zero, or RAM is divided into banks,
1360 this variable needs to be recalcuated to get the address.
1362 - CFG_SYS_SDRAM_BASE:
1363 Physical start address of SDRAM. _Must_ be 0 here.
1365 - CFG_SYS_FLASH_BASE:
1366 Physical start address of Flash memory.
1368 - CONFIG_SYS_MALLOC_LEN:
1369 Size of DRAM reserved for malloc() use.
1371 - CONFIG_SYS_MALLOC_F_LEN
1372 Size of the malloc() pool for use before relocation. If
1373 this is defined, then a very simple malloc() implementation
1374 will become available before relocation. The address is just
1375 below the global data, and the stack is moved down to make
1378 This feature allocates regions with increasing addresses
1379 within the region. calloc() is supported, but realloc()
1380 is not available. free() is supported but does nothing.
1381 The memory will be freed (or in fact just forgotten) when
1382 U-Boot relocates itself.
1384 - CONFIG_SYS_MALLOC_SIMPLE
1385 Provides a simple and small malloc() and calloc() for those
1386 boards which do not use the full malloc in SPL (which is
1387 enabled with CONFIG_SYS_SPL_MALLOC).
1389 - CFG_SYS_BOOTMAPSZ:
1390 Maximum size of memory mapped by the startup code of
1391 the Linux kernel; all data that must be processed by
1392 the Linux kernel (bd_info, boot arguments, FDT blob if
1393 used) must be put below this limit, unless "bootm_low"
1394 environment variable is defined and non-zero. In such case
1395 all data for the Linux kernel must be between "bootm_low"
1396 and "bootm_low" + CFG_SYS_BOOTMAPSZ. The environment
1397 variable "bootm_mapsize" will override the value of
1398 CFG_SYS_BOOTMAPSZ. If CFG_SYS_BOOTMAPSZ is undefined,
1399 then the value in "bootm_size" will be used instead.
1401 - CONFIG_SYS_BOOT_GET_CMDLINE:
1402 Enables allocating and saving kernel cmdline in space between
1403 "bootm_low" and "bootm_low" + BOOTMAPSZ.
1405 - CONFIG_SYS_BOOT_GET_KBD:
1406 Enables allocating and saving a kernel copy of the bd_info in
1407 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
1409 - CONFIG_SYS_FLASH_PROTECTION
1410 If defined, hardware flash sectors protection is used
1411 instead of U-Boot software protection.
1413 - CONFIG_SYS_FLASH_CFI:
1414 Define if the flash driver uses extra elements in the
1415 common flash structure for storing flash geometry.
1417 - CONFIG_FLASH_CFI_DRIVER
1418 This option also enables the building of the cfi_flash driver
1419 in the drivers directory
1421 - CONFIG_FLASH_CFI_MTD
1422 This option enables the building of the cfi_mtd driver
1423 in the drivers directory. The driver exports CFI flash
1426 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
1427 Use buffered writes to flash.
1429 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1430 - CONFIG_ENV_FLAGS_LIST_STATIC
1431 Enable validation of the values given to environment variables when
1432 calling env set. Variables can be restricted to only decimal,
1433 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
1434 the variables can also be restricted to IP address or MAC address.
1436 The format of the list is:
1437 type_attribute = [s|d|x|b|i|m]
1438 access_attribute = [a|r|o|c]
1439 attributes = type_attribute[access_attribute]
1440 entry = variable_name[:attributes]
1443 The type attributes are:
1444 s - String (default)
1447 b - Boolean ([1yYtT|0nNfF])
1451 The access attributes are:
1457 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1458 Define this to a list (string) to define the ".flags"
1459 environment variable in the default or embedded environment.
1461 - CONFIG_ENV_FLAGS_LIST_STATIC
1462 Define this to a list (string) to define validation that
1463 should be done if an entry is not found in the ".flags"
1464 environment variable. To override a setting in the static
1465 list, simply add an entry for the same variable name to the
1468 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
1469 regular expression. This allows multiple variables to define the same
1470 flags without explicitly listing them for each variable.
1472 The following definitions that deal with the placement and management
1473 of environment data (variable area); in general, we support the
1474 following configurations:
1476 BE CAREFUL! The first access to the environment happens quite early
1477 in U-Boot initialization (when we try to get the setting of for the
1478 console baudrate). You *MUST* have mapped your NVRAM area then, or
1481 Please note that even with NVRAM we still use a copy of the
1482 environment in RAM: we could work on NVRAM directly, but we want to
1483 keep settings there always unmodified except somebody uses "saveenv"
1484 to save the current settings.
1486 BE CAREFUL! For some special cases, the local device can not use
1487 "saveenv" command. For example, the local device will get the
1488 environment stored in a remote NOR flash by SRIO or PCIE link,
1489 but it can not erase, write this NOR flash by SRIO or PCIE interface.
1491 - CONFIG_NAND_ENV_DST
1493 Defines address in RAM to which the nand_spl code should copy the
1494 environment. If redundant environment is used, it will be copied to
1495 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
1497 Please note that the environment is read-only until the monitor
1498 has been relocated to RAM and a RAM copy of the environment has been
1499 created; also, when using EEPROM you will have to use env_get_f()
1500 until then to read environment variables.
1502 The environment is protected by a CRC32 checksum. Before the monitor
1503 is relocated into RAM, as a result of a bad CRC you will be working
1504 with the compiled-in default environment - *silently*!!! [This is
1505 necessary, because the first environment variable we need is the
1506 "baudrate" setting for the console - if we have a bad CRC, we don't
1507 have any device yet where we could complain.]
1509 Note: once the monitor has been relocated, then it will complain if
1510 the default environment is used; a new CRC is computed as soon as you
1511 use the "saveenv" command to store a valid environment.
1513 - CONFIG_SYS_FAULT_MII_ADDR:
1514 MII address of the PHY to check for the Ethernet link state.
1516 - CONFIG_DISPLAY_BOARDINFO
1517 Display information about the board that U-Boot is running on
1518 when U-Boot starts up. The board function checkboard() is called
1521 - CONFIG_DISPLAY_BOARDINFO_LATE
1522 Similar to the previous option, but display this information
1523 later, once stdio is running and output goes to the LCD, if
1526 Low Level (hardware related) configuration options:
1527 ---------------------------------------------------
1529 - CONFIG_SYS_CACHELINE_SIZE:
1530 Cache Line Size of the CPU.
1532 - CONFIG_SYS_CCSRBAR_DEFAULT:
1533 Default (power-on reset) physical address of CCSR on Freescale
1537 Virtual address of CCSR. On a 32-bit build, this is typically
1538 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
1540 - CFG_SYS_CCSRBAR_PHYS:
1541 Physical address of CCSR. CCSR can be relocated to a new
1542 physical address, if desired. In this case, this macro should
1543 be set to that address. Otherwise, it should be set to the
1544 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
1545 is typically relocated on 36-bit builds. It is recommended
1546 that this macro be defined via the _HIGH and _LOW macros:
1548 #define CFG_SYS_CCSRBAR_PHYS ((CFG_SYS_CCSRBAR_PHYS_HIGH
1549 * 1ull) << 32 | CFG_SYS_CCSRBAR_PHYS_LOW)
1551 - CFG_SYS_CCSRBAR_PHYS_HIGH:
1552 Bits 33-36 of CFG_SYS_CCSRBAR_PHYS. This value is typically
1553 either 0 (32-bit build) or 0xF (36-bit build). This macro is
1554 used in assembly code, so it must not contain typecasts or
1555 integer size suffixes (e.g. "ULL").
1557 - CFG_SYS_CCSRBAR_PHYS_LOW:
1558 Lower 32-bits of CFG_SYS_CCSRBAR_PHYS. This macro is
1559 used in assembly code, so it must not contain typecasts or
1560 integer size suffixes (e.g. "ULL").
1562 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
1563 DO NOT CHANGE unless you know exactly what you're
1564 doing! (11-4) [MPC8xx systems only]
1566 - CFG_SYS_INIT_RAM_ADDR:
1568 Start address of memory area that can be used for
1569 initial data and stack; please note that this must be
1570 writable memory that is working WITHOUT special
1571 initialization, i. e. you CANNOT use normal RAM which
1572 will become available only after programming the
1573 memory controller and running certain initialization
1576 U-Boot uses the following memory types:
1577 - MPC8xx: IMMR (internal memory of the CPU)
1579 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
1581 - CONFIG_SYS_OR_TIMING_SDRAM:
1584 - CONFIG_SYS_SRIOn_MEM_VIRT:
1585 Virtual Address of SRIO port 'n' memory region
1587 - CONFIG_SYS_SRIOn_MEM_PHYxS:
1588 Physical Address of SRIO port 'n' memory region
1590 - CONFIG_SYS_SRIOn_MEM_SIZE:
1591 Size of SRIO port 'n' memory region
1593 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
1594 Defined to tell the NAND controller that the NAND chip is using
1596 Not all NAND drivers use this symbol.
1597 Example of drivers that use it:
1598 - drivers/mtd/nand/raw/ndfc.c
1599 - drivers/mtd/nand/raw/mxc_nand.c
1601 - CONFIG_SYS_NDFC_EBC0_CFG
1602 Sets the EBC0_CFG register for the NDFC. If not defined
1603 a default value will be used.
1605 - CONFIG_SYS_SPD_BUS_NUM
1606 If SPD EEPROM is on an I2C bus other than the first
1607 one, specify here. Note that the value must resolve
1608 to something your driver can deal with.
1610 - CONFIG_FSL_DDR_INTERACTIVE
1611 Enable interactive DDR debugging. See doc/README.fsl-ddr.
1613 - CONFIG_FSL_DDR_SYNC_REFRESH
1614 Enable sync of refresh for multiple controllers.
1616 - CONFIG_FSL_DDR_BIST
1617 Enable built-in memory test for Freescale DDR controllers.
1620 Enable RMII mode for all FECs.
1621 Note that this is a global option, we can't
1622 have one FEC in standard MII mode and another in RMII mode.
1624 - CONFIG_CRC32_VERIFY
1625 Add a verify option to the crc32 command.
1628 => crc32 -v <address> <count> <crc32>
1630 Where address/count indicate a memory area
1631 and crc32 is the correct crc32 which the
1635 Add the "loopw" memory command. This only takes effect if
1636 the memory commands are activated globally (CONFIG_CMD_MEMORY).
1638 - CONFIG_CMD_MX_CYCLIC
1639 Add the "mdc" and "mwc" memory commands. These are cyclic
1644 This command will print 4 bytes (10,11,12,13) each 500 ms.
1646 => mwc.l 100 12345678 10
1647 This command will write 12345678 to address 100 all 10 ms.
1649 This only takes effect if the memory commands are activated
1650 globally (CONFIG_CMD_MEMORY).
1653 Set when the currently-running compilation is for an artifact
1654 that will end up in the SPL (as opposed to the TPL or U-Boot
1655 proper). Code that needs stage-specific behavior should check
1659 Set when the currently-running compilation is for an artifact
1660 that will end up in the TPL (as opposed to the SPL or U-Boot
1661 proper). Code that needs stage-specific behavior should check
1664 - CONFIG_ARCH_MAP_SYSMEM
1665 Generally U-Boot (and in particular the md command) uses
1666 effective address. It is therefore not necessary to regard
1667 U-Boot address as virtual addresses that need to be translated
1668 to physical addresses. However, sandbox requires this, since
1669 it maintains its own little RAM buffer which contains all
1670 addressable memory. This option causes some memory accesses
1671 to be mapped through map_sysmem() / unmap_sysmem().
1673 - CONFIG_X86_RESET_VECTOR
1674 If defined, the x86 reset vector code is included. This is not
1675 needed when U-Boot is running from Coreboot.
1677 Freescale QE/FMAN Firmware Support:
1678 -----------------------------------
1680 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
1681 loading of "firmware", which is encoded in the QE firmware binary format.
1682 This firmware often needs to be loaded during U-Boot booting, so macros
1683 are used to identify the storage device (NOR flash, SPI, etc) and the address
1686 - CONFIG_SYS_FMAN_FW_ADDR
1687 The address in the storage device where the FMAN microcode is located. The
1688 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1691 - CONFIG_SYS_QE_FW_ADDR
1692 The address in the storage device where the QE microcode is located. The
1693 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1696 - CONFIG_SYS_QE_FMAN_FW_LENGTH
1697 The maximum possible size of the firmware. The firmware binary format
1698 has a field that specifies the actual size of the firmware, but it
1699 might not be possible to read any part of the firmware unless some
1700 local storage is allocated to hold the entire firmware first.
1702 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
1703 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
1704 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
1705 virtual address in NOR flash.
1707 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
1708 Specifies that QE/FMAN firmware is located in NAND flash.
1709 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
1711 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
1712 Specifies that QE/FMAN firmware is located on the primary SD/MMC
1713 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
1715 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
1716 Specifies that QE/FMAN firmware is located in the remote (master)
1717 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
1718 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
1719 window->master inbound window->master LAW->the ucode address in
1720 master's memory space.
1722 Freescale Layerscape Management Complex Firmware Support:
1723 ---------------------------------------------------------
1724 The Freescale Layerscape Management Complex (MC) supports the loading of
1726 This firmware often needs to be loaded during U-Boot booting, so macros
1727 are used to identify the storage device (NOR flash, SPI, etc) and the address
1730 - CONFIG_FSL_MC_ENET
1731 Enable the MC driver for Layerscape SoCs.
1733 Freescale Layerscape Debug Server Support:
1734 -------------------------------------------
1735 The Freescale Layerscape Debug Server Support supports the loading of
1736 "Debug Server firmware" and triggering SP boot-rom.
1737 This firmware often needs to be loaded during U-Boot booting.
1739 - CONFIG_SYS_MC_RSV_MEM_ALIGN
1740 Define alignment of reserved memory MC requires
1745 In order to achieve reproducible builds, timestamps used in the U-Boot build
1746 process have to be set to a fixed value.
1748 This is done using the SOURCE_DATE_EPOCH environment variable.
1749 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
1750 option for U-Boot or an environment variable in U-Boot.
1752 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
1754 Building the Software:
1755 ======================
1757 Building U-Boot has been tested in several native build environments
1758 and in many different cross environments. Of course we cannot support
1759 all possibly existing versions of cross development tools in all
1760 (potentially obsolete) versions. In case of tool chain problems we
1761 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
1762 which is extensively used to build and test U-Boot.
1764 If you are not using a native environment, it is assumed that you
1765 have GNU cross compiling tools available in your path. In this case,
1766 you must set the environment variable CROSS_COMPILE in your shell.
1767 Note that no changes to the Makefile or any other source files are
1768 necessary. For example using the ELDK on a 4xx CPU, please enter:
1770 $ CROSS_COMPILE=ppc_4xx-
1771 $ export CROSS_COMPILE
1773 U-Boot is intended to be simple to build. After installing the
1774 sources you must configure U-Boot for one specific board type. This
1779 where "NAME_defconfig" is the name of one of the existing configu-
1780 rations; see configs/*_defconfig for supported names.
1782 Note: for some boards special configuration names may exist; check if
1783 additional information is available from the board vendor; for
1784 instance, the TQM823L systems are available without (standard)
1785 or with LCD support. You can select such additional "features"
1786 when choosing the configuration, i. e.
1788 make TQM823L_defconfig
1789 - will configure for a plain TQM823L, i. e. no LCD support
1791 make TQM823L_LCD_defconfig
1792 - will configure for a TQM823L with U-Boot console on LCD
1797 Finally, type "make all", and you should get some working U-Boot
1798 images ready for download to / installation on your system:
1800 - "u-boot.bin" is a raw binary image
1801 - "u-boot" is an image in ELF binary format
1802 - "u-boot.srec" is in Motorola S-Record format
1804 By default the build is performed locally and the objects are saved
1805 in the source directory. One of the two methods can be used to change
1806 this behavior and build U-Boot to some external directory:
1808 1. Add O= to the make command line invocations:
1810 make O=/tmp/build distclean
1811 make O=/tmp/build NAME_defconfig
1812 make O=/tmp/build all
1814 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
1816 export KBUILD_OUTPUT=/tmp/build
1821 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
1824 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
1825 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
1826 For example to treat all compiler warnings as errors:
1828 make KCFLAGS=-Werror
1830 Please be aware that the Makefiles assume you are using GNU make, so
1831 for instance on NetBSD you might need to use "gmake" instead of
1835 If the system board that you have is not listed, then you will need
1836 to port U-Boot to your hardware platform. To do this, follow these
1839 1. Create a new directory to hold your board specific code. Add any
1840 files you need. In your board directory, you will need at least
1841 the "Makefile" and a "<board>.c".
1842 2. Create a new configuration file "include/configs/<board>.h" for
1844 3. If you're porting U-Boot to a new CPU, then also create a new
1845 directory to hold your CPU specific code. Add any files you need.
1846 4. Run "make <board>_defconfig" with your new name.
1847 5. Type "make", and you should get a working "u-boot.srec" file
1848 to be installed on your target system.
1849 6. Debug and solve any problems that might arise.
1850 [Of course, this last step is much harder than it sounds.]
1853 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
1854 ==============================================================
1856 If you have modified U-Boot sources (for instance added a new board
1857 or support for new devices, a new CPU, etc.) you are expected to
1858 provide feedback to the other developers. The feedback normally takes
1859 the form of a "patch", i.e. a context diff against a certain (latest
1860 official or latest in the git repository) version of U-Boot sources.
1862 But before you submit such a patch, please verify that your modifi-
1863 cation did not break existing code. At least make sure that *ALL* of
1864 the supported boards compile WITHOUT ANY compiler warnings. To do so,
1865 just run the buildman script (tools/buildman/buildman), which will
1866 configure and build U-Boot for ALL supported system. Be warned, this
1867 will take a while. Please see the buildman README, or run 'buildman -H'
1871 See also "U-Boot Porting Guide" below.
1874 Monitor Commands - Overview:
1875 ============================
1877 go - start application at address 'addr'
1878 run - run commands in an environment variable
1879 bootm - boot application image from memory
1880 bootp - boot image via network using BootP/TFTP protocol
1881 bootz - boot zImage from memory
1882 tftpboot- boot image via network using TFTP protocol
1883 and env variables "ipaddr" and "serverip"
1884 (and eventually "gatewayip")
1885 tftpput - upload a file via network using TFTP protocol
1886 rarpboot- boot image via network using RARP/TFTP protocol
1887 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
1888 loads - load S-Record file over serial line
1889 loadb - load binary file over serial line (kermit mode)
1890 loadm - load binary blob from source address to destination address
1892 mm - memory modify (auto-incrementing)
1893 nm - memory modify (constant address)
1894 mw - memory write (fill)
1897 cmp - memory compare
1898 crc32 - checksum calculation
1899 i2c - I2C sub-system
1900 sspi - SPI utility commands
1901 base - print or set address offset
1902 printenv- print environment variables
1903 pwm - control pwm channels
1904 setenv - set environment variables
1905 saveenv - save environment variables to persistent storage
1906 protect - enable or disable FLASH write protection
1907 erase - erase FLASH memory
1908 flinfo - print FLASH memory information
1909 nand - NAND memory operations (see doc/README.nand)
1910 bdinfo - print Board Info structure
1911 iminfo - print header information for application image
1912 coninfo - print console devices and informations
1913 ide - IDE sub-system
1914 loop - infinite loop on address range
1915 loopw - infinite write loop on address range
1916 mtest - simple RAM test
1917 icache - enable or disable instruction cache
1918 dcache - enable or disable data cache
1919 reset - Perform RESET of the CPU
1920 echo - echo args to console
1921 version - print monitor version
1922 help - print online help
1923 ? - alias for 'help'
1926 Monitor Commands - Detailed Description:
1927 ========================================
1931 For now: just type "help <command>".
1934 Note for Redundant Ethernet Interfaces:
1935 =======================================
1937 Some boards come with redundant Ethernet interfaces; U-Boot supports
1938 such configurations and is capable of automatic selection of a
1939 "working" interface when needed. MAC assignment works as follows:
1941 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
1942 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
1943 "eth1addr" (=>eth1), "eth2addr", ...
1945 If the network interface stores some valid MAC address (for instance
1946 in SROM), this is used as default address if there is NO correspon-
1947 ding setting in the environment; if the corresponding environment
1948 variable is set, this overrides the settings in the card; that means:
1950 o If the SROM has a valid MAC address, and there is no address in the
1951 environment, the SROM's address is used.
1953 o If there is no valid address in the SROM, and a definition in the
1954 environment exists, then the value from the environment variable is
1957 o If both the SROM and the environment contain a MAC address, and
1958 both addresses are the same, this MAC address is used.
1960 o If both the SROM and the environment contain a MAC address, and the
1961 addresses differ, the value from the environment is used and a
1964 o If neither SROM nor the environment contain a MAC address, an error
1965 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
1966 a random, locally-assigned MAC is used.
1968 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
1969 will be programmed into hardware as part of the initialization process. This
1970 may be skipped by setting the appropriate 'ethmacskip' environment variable.
1971 The naming convention is as follows:
1972 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
1977 U-Boot is capable of booting (and performing other auxiliary operations on)
1978 images in two formats:
1980 New uImage format (FIT)
1981 -----------------------
1983 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
1984 to Flattened Device Tree). It allows the use of images with multiple
1985 components (several kernels, ramdisks, etc.), with contents protected by
1986 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
1992 Old image format is based on binary files which can be basically anything,
1993 preceded by a special header; see the definitions in include/image.h for
1994 details; basically, the header defines the following image properties:
1996 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
1997 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
1998 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
1999 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
2000 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
2001 IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
2002 Currently supported: ARM, Intel x86, MIPS, Nios II, PowerPC).
2003 * Compression Type (uncompressed, gzip, bzip2)
2009 The header is marked by a special Magic Number, and both the header
2010 and the data portions of the image are secured against corruption by
2017 Although U-Boot should support any OS or standalone application
2018 easily, the main focus has always been on Linux during the design of
2021 U-Boot includes many features that so far have been part of some
2022 special "boot loader" code within the Linux kernel. Also, any
2023 "initrd" images to be used are no longer part of one big Linux image;
2024 instead, kernel and "initrd" are separate images. This implementation
2025 serves several purposes:
2027 - the same features can be used for other OS or standalone
2028 applications (for instance: using compressed images to reduce the
2029 Flash memory footprint)
2031 - it becomes much easier to port new Linux kernel versions because
2032 lots of low-level, hardware dependent stuff are done by U-Boot
2034 - the same Linux kernel image can now be used with different "initrd"
2035 images; of course this also means that different kernel images can
2036 be run with the same "initrd". This makes testing easier (you don't
2037 have to build a new "zImage.initrd" Linux image when you just
2038 change a file in your "initrd"). Also, a field-upgrade of the
2039 software is easier now.
2045 Porting Linux to U-Boot based systems:
2046 ---------------------------------------
2048 U-Boot cannot save you from doing all the necessary modifications to
2049 configure the Linux device drivers for use with your target hardware
2050 (no, we don't intend to provide a full virtual machine interface to
2053 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
2055 Just make sure your machine specific header file (for instance
2056 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2057 Information structure as we define in include/asm-<arch>/u-boot.h,
2058 and make sure that your definition of IMAP_ADDR uses the same value
2059 as your U-Boot configuration in CONFIG_SYS_IMMR.
2061 Note that U-Boot now has a driver model, a unified model for drivers.
2062 If you are adding a new driver, plumb it into driver model. If there
2063 is no uclass available, you are encouraged to create one. See
2067 Configuring the Linux kernel:
2068 -----------------------------
2070 No specific requirements for U-Boot. Make sure you have some root
2071 device (initial ramdisk, NFS) for your target system.
2074 Building a Linux Image:
2075 -----------------------
2077 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2078 not used. If you use recent kernel source, a new build target
2079 "uImage" will exist which automatically builds an image usable by
2080 U-Boot. Most older kernels also have support for a "pImage" target,
2081 which was introduced for our predecessor project PPCBoot and uses a
2082 100% compatible format.
2086 make TQM850L_defconfig
2091 The "uImage" build target uses a special tool (in 'tools/mkimage') to
2092 encapsulate a compressed Linux kernel image with header information,
2093 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2095 * build a standard "vmlinux" kernel image (in ELF binary format):
2097 * convert the kernel into a raw binary image:
2099 ${CROSS_COMPILE}-objcopy -O binary \
2100 -R .note -R .comment \
2101 -S vmlinux linux.bin
2103 * compress the binary image:
2107 * package compressed binary image for U-Boot:
2109 mkimage -A ppc -O linux -T kernel -C gzip \
2110 -a 0 -e 0 -n "Linux Kernel Image" \
2111 -d linux.bin.gz uImage
2114 The "mkimage" tool can also be used to create ramdisk images for use
2115 with U-Boot, either separated from the Linux kernel image, or
2116 combined into one file. "mkimage" encapsulates the images with a 64
2117 byte header containing information about target architecture,
2118 operating system, image type, compression method, entry points, time
2119 stamp, CRC32 checksums, etc.
2121 "mkimage" can be called in two ways: to verify existing images and
2122 print the header information, or to build new images.
2124 In the first form (with "-l" option) mkimage lists the information
2125 contained in the header of an existing U-Boot image; this includes
2126 checksum verification:
2128 tools/mkimage -l image
2129 -l ==> list image header information
2131 The second form (with "-d" option) is used to build a U-Boot image
2132 from a "data file" which is used as image payload:
2134 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
2135 -n name -d data_file image
2136 -A ==> set architecture to 'arch'
2137 -O ==> set operating system to 'os'
2138 -T ==> set image type to 'type'
2139 -C ==> set compression type 'comp'
2140 -a ==> set load address to 'addr' (hex)
2141 -e ==> set entry point to 'ep' (hex)
2142 -n ==> set image name to 'name'
2143 -d ==> use image data from 'datafile'
2145 Right now, all Linux kernels for PowerPC systems use the same load
2146 address (0x00000000), but the entry point address depends on the
2149 - 2.2.x kernels have the entry point at 0x0000000C,
2150 - 2.3.x and later kernels have the entry point at 0x00000000.
2152 So a typical call to build a U-Boot image would read:
2154 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2155 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
2156 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
2157 > examples/uImage.TQM850L
2158 Image Name: 2.4.4 kernel for TQM850L
2159 Created: Wed Jul 19 02:34:59 2000
2160 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2161 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2162 Load Address: 0x00000000
2163 Entry Point: 0x00000000
2165 To verify the contents of the image (or check for corruption):
2167 -> tools/mkimage -l examples/uImage.TQM850L
2168 Image Name: 2.4.4 kernel for TQM850L
2169 Created: Wed Jul 19 02:34:59 2000
2170 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2171 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2172 Load Address: 0x00000000
2173 Entry Point: 0x00000000
2175 NOTE: for embedded systems where boot time is critical you can trade
2176 speed for memory and install an UNCOMPRESSED image instead: this
2177 needs more space in Flash, but boots much faster since it does not
2178 need to be uncompressed:
2180 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
2181 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2182 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
2183 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
2184 > examples/uImage.TQM850L-uncompressed
2185 Image Name: 2.4.4 kernel for TQM850L
2186 Created: Wed Jul 19 02:34:59 2000
2187 Image Type: PowerPC Linux Kernel Image (uncompressed)
2188 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
2189 Load Address: 0x00000000
2190 Entry Point: 0x00000000
2193 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
2194 when your kernel is intended to use an initial ramdisk:
2196 -> tools/mkimage -n 'Simple Ramdisk Image' \
2197 > -A ppc -O linux -T ramdisk -C gzip \
2198 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
2199 Image Name: Simple Ramdisk Image
2200 Created: Wed Jan 12 14:01:50 2000
2201 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2202 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
2203 Load Address: 0x00000000
2204 Entry Point: 0x00000000
2206 The "dumpimage" tool can be used to disassemble or list the contents of images
2207 built by mkimage. See dumpimage's help output (-h) for details.
2209 Installing a Linux Image:
2210 -------------------------
2212 To downloading a U-Boot image over the serial (console) interface,
2213 you must convert the image to S-Record format:
2215 objcopy -I binary -O srec examples/image examples/image.srec
2217 The 'objcopy' does not understand the information in the U-Boot
2218 image header, so the resulting S-Record file will be relative to
2219 address 0x00000000. To load it to a given address, you need to
2220 specify the target address as 'offset' parameter with the 'loads'
2223 Example: install the image to address 0x40100000 (which on the
2224 TQM8xxL is in the first Flash bank):
2226 => erase 40100000 401FFFFF
2232 ## Ready for S-Record download ...
2233 ~>examples/image.srec
2234 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
2236 15989 15990 15991 15992
2237 [file transfer complete]
2239 ## Start Addr = 0x00000000
2242 You can check the success of the download using the 'iminfo' command;
2243 this includes a checksum verification so you can be sure no data
2244 corruption happened:
2248 ## Checking Image at 40100000 ...
2249 Image Name: 2.2.13 for initrd on TQM850L
2250 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2251 Data Size: 335725 Bytes = 327 kB = 0 MB
2252 Load Address: 00000000
2253 Entry Point: 0000000c
2254 Verifying Checksum ... OK
2260 The "bootm" command is used to boot an application that is stored in
2261 memory (RAM or Flash). In case of a Linux kernel image, the contents
2262 of the "bootargs" environment variable is passed to the kernel as
2263 parameters. You can check and modify this variable using the
2264 "printenv" and "setenv" commands:
2267 => printenv bootargs
2268 bootargs=root=/dev/ram
2270 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2272 => printenv bootargs
2273 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2276 ## Booting Linux kernel at 40020000 ...
2277 Image Name: 2.2.13 for NFS on TQM850L
2278 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2279 Data Size: 381681 Bytes = 372 kB = 0 MB
2280 Load Address: 00000000
2281 Entry Point: 0000000c
2282 Verifying Checksum ... OK
2283 Uncompressing Kernel Image ... OK
2284 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
2285 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2286 time_init: decrementer frequency = 187500000/60
2287 Calibrating delay loop... 49.77 BogoMIPS
2288 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
2291 If you want to boot a Linux kernel with initial RAM disk, you pass
2292 the memory addresses of both the kernel and the initrd image (PPBCOOT
2293 format!) to the "bootm" command:
2295 => imi 40100000 40200000
2297 ## Checking Image at 40100000 ...
2298 Image Name: 2.2.13 for initrd on TQM850L
2299 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2300 Data Size: 335725 Bytes = 327 kB = 0 MB
2301 Load Address: 00000000
2302 Entry Point: 0000000c
2303 Verifying Checksum ... OK
2305 ## Checking Image at 40200000 ...
2306 Image Name: Simple Ramdisk Image
2307 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2308 Data Size: 566530 Bytes = 553 kB = 0 MB
2309 Load Address: 00000000
2310 Entry Point: 00000000
2311 Verifying Checksum ... OK
2313 => bootm 40100000 40200000
2314 ## Booting Linux kernel at 40100000 ...
2315 Image Name: 2.2.13 for initrd on TQM850L
2316 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2317 Data Size: 335725 Bytes = 327 kB = 0 MB
2318 Load Address: 00000000
2319 Entry Point: 0000000c
2320 Verifying Checksum ... OK
2321 Uncompressing Kernel Image ... OK
2322 ## Loading RAMDisk Image at 40200000 ...
2323 Image Name: Simple Ramdisk Image
2324 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2325 Data Size: 566530 Bytes = 553 kB = 0 MB
2326 Load Address: 00000000
2327 Entry Point: 00000000
2328 Verifying Checksum ... OK
2329 Loading Ramdisk ... OK
2330 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
2331 Boot arguments: root=/dev/ram
2332 time_init: decrementer frequency = 187500000/60
2333 Calibrating delay loop... 49.77 BogoMIPS
2335 RAMDISK: Compressed image found at block 0
2336 VFS: Mounted root (ext2 filesystem).
2340 Boot Linux and pass a flat device tree:
2343 First, U-Boot must be compiled with the appropriate defines. See the section
2344 titled "Linux Kernel Interface" above for a more in depth explanation. The
2345 following is an example of how to start a kernel and pass an updated
2351 oft=oftrees/mpc8540ads.dtb
2352 => tftp $oftaddr $oft
2353 Speed: 1000, full duplex
2355 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
2356 Filename 'oftrees/mpc8540ads.dtb'.
2357 Load address: 0x300000
2360 Bytes transferred = 4106 (100a hex)
2361 => tftp $loadaddr $bootfile
2362 Speed: 1000, full duplex
2364 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
2366 Load address: 0x200000
2367 Loading:############
2369 Bytes transferred = 1029407 (fb51f hex)
2374 => bootm $loadaddr - $oftaddr
2375 ## Booting image at 00200000 ...
2376 Image Name: Linux-2.6.17-dirty
2377 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2378 Data Size: 1029343 Bytes = 1005.2 kB
2379 Load Address: 00000000
2380 Entry Point: 00000000
2381 Verifying Checksum ... OK
2382 Uncompressing Kernel Image ... OK
2383 Booting using flat device tree at 0x300000
2384 Using MPC85xx ADS machine description
2385 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
2389 More About U-Boot Image Types:
2390 ------------------------------
2392 U-Boot supports the following image types:
2394 "Standalone Programs" are directly runnable in the environment
2395 provided by U-Boot; it is expected that (if they behave
2396 well) you can continue to work in U-Boot after return from
2397 the Standalone Program.
2398 "OS Kernel Images" are usually images of some Embedded OS which
2399 will take over control completely. Usually these programs
2400 will install their own set of exception handlers, device
2401 drivers, set up the MMU, etc. - this means, that you cannot
2402 expect to re-enter U-Boot except by resetting the CPU.
2403 "RAMDisk Images" are more or less just data blocks, and their
2404 parameters (address, size) are passed to an OS kernel that is
2406 "Multi-File Images" contain several images, typically an OS
2407 (Linux) kernel image and one or more data images like
2408 RAMDisks. This construct is useful for instance when you want
2409 to boot over the network using BOOTP etc., where the boot
2410 server provides just a single image file, but you want to get
2411 for instance an OS kernel and a RAMDisk image.
2413 "Multi-File Images" start with a list of image sizes, each
2414 image size (in bytes) specified by an "uint32_t" in network
2415 byte order. This list is terminated by an "(uint32_t)0".
2416 Immediately after the terminating 0 follow the images, one by
2417 one, all aligned on "uint32_t" boundaries (size rounded up to
2418 a multiple of 4 bytes).
2420 "Firmware Images" are binary images containing firmware (like
2421 U-Boot or FPGA images) which usually will be programmed to
2424 "Script files" are command sequences that will be executed by
2425 U-Boot's command interpreter; this feature is especially
2426 useful when you configure U-Boot to use a real shell (hush)
2427 as command interpreter.
2429 Booting the Linux zImage:
2430 -------------------------
2432 On some platforms, it's possible to boot Linux zImage. This is done
2433 using the "bootz" command. The syntax of "bootz" command is the same
2434 as the syntax of "bootm" command.
2436 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
2437 kernel with raw initrd images. The syntax is slightly different, the
2438 address of the initrd must be augmented by it's size, in the following
2439 format: "<initrd addres>:<initrd size>".
2445 One of the features of U-Boot is that you can dynamically load and
2446 run "standalone" applications, which can use some resources of
2447 U-Boot like console I/O functions or interrupt services.
2449 Two simple examples are included with the sources:
2454 'examples/hello_world.c' contains a small "Hello World" Demo
2455 application; it is automatically compiled when you build U-Boot.
2456 It's configured to run at address 0x00040004, so you can play with it
2460 ## Ready for S-Record download ...
2461 ~>examples/hello_world.srec
2462 1 2 3 4 5 6 7 8 9 10 11 ...
2463 [file transfer complete]
2465 ## Start Addr = 0x00040004
2467 => go 40004 Hello World! This is a test.
2468 ## Starting application at 0x00040004 ...
2479 Hit any key to exit ...
2481 ## Application terminated, rc = 0x0
2483 Another example, which demonstrates how to register a CPM interrupt
2484 handler with the U-Boot code, can be found in 'examples/timer.c'.
2485 Here, a CPM timer is set up to generate an interrupt every second.
2486 The interrupt service routine is trivial, just printing a '.'
2487 character, but this is just a demo program. The application can be
2488 controlled by the following keys:
2490 ? - print current values og the CPM Timer registers
2491 b - enable interrupts and start timer
2492 e - stop timer and disable interrupts
2493 q - quit application
2496 ## Ready for S-Record download ...
2497 ~>examples/timer.srec
2498 1 2 3 4 5 6 7 8 9 10 11 ...
2499 [file transfer complete]
2501 ## Start Addr = 0x00040004
2504 ## Starting application at 0x00040004 ...
2507 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
2510 [q, b, e, ?] Set interval 1000000 us
2513 [q, b, e, ?] ........
2514 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
2517 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
2520 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
2523 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
2525 [q, b, e, ?] ...Stopping timer
2527 [q, b, e, ?] ## Application terminated, rc = 0x0
2533 Over time, many people have reported problems when trying to use the
2534 "minicom" terminal emulation program for serial download. I (wd)
2535 consider minicom to be broken, and recommend not to use it. Under
2536 Unix, I recommend to use C-Kermit for general purpose use (and
2537 especially for kermit binary protocol download ("loadb" command), and
2538 use "cu" for S-Record download ("loads" command). See
2539 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
2540 for help with kermit.
2543 Nevertheless, if you absolutely want to use it try adding this
2544 configuration to your "File transfer protocols" section:
2546 Name Program Name U/D FullScr IO-Red. Multi
2547 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
2548 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
2554 Starting at version 0.9.2, U-Boot supports NetBSD both as host
2555 (build U-Boot) and target system (boots NetBSD/mpc8xx).
2557 Building requires a cross environment; it is known to work on
2558 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
2559 need gmake since the Makefiles are not compatible with BSD make).
2560 Note that the cross-powerpc package does not install include files;
2561 attempting to build U-Boot will fail because <machine/ansi.h> is
2562 missing. This file has to be installed and patched manually:
2564 # cd /usr/pkg/cross/powerpc-netbsd/include
2566 # ln -s powerpc machine
2567 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
2568 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
2570 Native builds *don't* work due to incompatibilities between native
2571 and U-Boot include files.
2573 Booting assumes that (the first part of) the image booted is a
2574 stage-2 loader which in turn loads and then invokes the kernel
2575 proper. Loader sources will eventually appear in the NetBSD source
2576 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
2577 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
2580 Implementation Internals:
2581 =========================
2583 The following is not intended to be a complete description of every
2584 implementation detail. However, it should help to understand the
2585 inner workings of U-Boot and make it easier to port it to custom
2589 Initial Stack, Global Data:
2590 ---------------------------
2592 The implementation of U-Boot is complicated by the fact that U-Boot
2593 starts running out of ROM (flash memory), usually without access to
2594 system RAM (because the memory controller is not initialized yet).
2595 This means that we don't have writable Data or BSS segments, and BSS
2596 is not initialized as zero. To be able to get a C environment working
2597 at all, we have to allocate at least a minimal stack. Implementation
2598 options for this are defined and restricted by the CPU used: Some CPU
2599 models provide on-chip memory (like the IMMR area on MPC8xx and
2600 MPC826x processors), on others (parts of) the data cache can be
2601 locked as (mis-) used as memory, etc.
2603 Chris Hallinan posted a good summary of these issues to the
2604 U-Boot mailing list:
2606 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
2607 From: "Chris Hallinan" <clh@net1plus.com>
2608 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
2611 Correct me if I'm wrong, folks, but the way I understand it
2612 is this: Using DCACHE as initial RAM for Stack, etc, does not
2613 require any physical RAM backing up the cache. The cleverness
2614 is that the cache is being used as a temporary supply of
2615 necessary storage before the SDRAM controller is setup. It's
2616 beyond the scope of this list to explain the details, but you
2617 can see how this works by studying the cache architecture and
2618 operation in the architecture and processor-specific manuals.
2620 OCM is On Chip Memory, which I believe the 405GP has 4K. It
2621 is another option for the system designer to use as an
2622 initial stack/RAM area prior to SDRAM being available. Either
2623 option should work for you. Using CS 4 should be fine if your
2624 board designers haven't used it for something that would
2625 cause you grief during the initial boot! It is frequently not
2628 CFG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
2629 with your processor/board/system design. The default value
2630 you will find in any recent u-boot distribution in
2631 walnut.h should work for you. I'd set it to a value larger
2632 than your SDRAM module. If you have a 64MB SDRAM module, set
2633 it above 400_0000. Just make sure your board has no resources
2634 that are supposed to respond to that address! That code in
2635 start.S has been around a while and should work as is when
2636 you get the config right.
2641 It is essential to remember this, since it has some impact on the C
2642 code for the initialization procedures:
2644 * Initialized global data (data segment) is read-only. Do not attempt
2647 * Do not use any uninitialized global data (or implicitly initialized
2648 as zero data - BSS segment) at all - this is undefined, initiali-
2649 zation is performed later (when relocating to RAM).
2651 * Stack space is very limited. Avoid big data buffers or things like
2654 Having only the stack as writable memory limits means we cannot use
2655 normal global data to share information between the code. But it
2656 turned out that the implementation of U-Boot can be greatly
2657 simplified by making a global data structure (gd_t) available to all
2658 functions. We could pass a pointer to this data as argument to _all_
2659 functions, but this would bloat the code. Instead we use a feature of
2660 the GCC compiler (Global Register Variables) to share the data: we
2661 place a pointer (gd) to the global data into a register which we
2662 reserve for this purpose.
2664 When choosing a register for such a purpose we are restricted by the
2665 relevant (E)ABI specifications for the current architecture, and by
2666 GCC's implementation.
2668 For PowerPC, the following registers have specific use:
2670 R2: reserved for system use
2671 R3-R4: parameter passing and return values
2672 R5-R10: parameter passing
2673 R13: small data area pointer
2677 (U-Boot also uses R12 as internal GOT pointer. r12
2678 is a volatile register so r12 needs to be reset when
2679 going back and forth between asm and C)
2681 ==> U-Boot will use R2 to hold a pointer to the global data
2683 Note: on PPC, we could use a static initializer (since the
2684 address of the global data structure is known at compile time),
2685 but it turned out that reserving a register results in somewhat
2686 smaller code - although the code savings are not that big (on
2687 average for all boards 752 bytes for the whole U-Boot image,
2688 624 text + 127 data).
2690 On ARM, the following registers are used:
2692 R0: function argument word/integer result
2693 R1-R3: function argument word
2694 R9: platform specific
2695 R10: stack limit (used only if stack checking is enabled)
2696 R11: argument (frame) pointer
2697 R12: temporary workspace
2700 R15: program counter
2702 ==> U-Boot will use R9 to hold a pointer to the global data
2704 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
2706 On Nios II, the ABI is documented here:
2707 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
2709 ==> U-Boot will use gp to hold a pointer to the global data
2711 Note: on Nios II, we give "-G0" option to gcc and don't use gp
2712 to access small data sections, so gp is free.
2714 On RISC-V, the following registers are used:
2716 x0: hard-wired zero (zero)
2717 x1: return address (ra)
2718 x2: stack pointer (sp)
2719 x3: global pointer (gp)
2720 x4: thread pointer (tp)
2721 x5: link register (t0)
2722 x8: frame pointer (fp)
2723 x10-x11: arguments/return values (a0-1)
2724 x12-x17: arguments (a2-7)
2725 x28-31: temporaries (t3-6)
2726 pc: program counter (pc)
2728 ==> U-Boot will use gp to hold a pointer to the global data
2733 U-Boot runs in system state and uses physical addresses, i.e. the
2734 MMU is not used either for address mapping nor for memory protection.
2736 The available memory is mapped to fixed addresses using the memory
2737 controller. In this process, a contiguous block is formed for each
2738 memory type (Flash, SDRAM, SRAM), even when it consists of several
2739 physical memory banks.
2741 U-Boot is installed in the first 128 kB of the first Flash bank (on
2742 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
2743 booting and sizing and initializing DRAM, the code relocates itself
2744 to the upper end of DRAM. Immediately below the U-Boot code some
2745 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
2746 configuration setting]. Below that, a structure with global Board
2747 Info data is placed, followed by the stack (growing downward).
2749 Additionally, some exception handler code is copied to the low 8 kB
2750 of DRAM (0x00000000 ... 0x00001FFF).
2752 So a typical memory configuration with 16 MB of DRAM could look like
2755 0x0000 0000 Exception Vector code
2758 0x0000 2000 Free for Application Use
2764 0x00FB FF20 Monitor Stack (Growing downward)
2765 0x00FB FFAC Board Info Data and permanent copy of global data
2766 0x00FC 0000 Malloc Arena
2769 0x00FE 0000 RAM Copy of Monitor Code
2770 ... eventually: LCD or video framebuffer
2771 ... eventually: pRAM (Protected RAM - unchanged by reset)
2772 0x00FF FFFF [End of RAM]
2775 System Initialization:
2776 ----------------------
2778 In the reset configuration, U-Boot starts at the reset entry point
2779 (on most PowerPC systems at address 0x00000100). Because of the reset
2780 configuration for CS0# this is a mirror of the on board Flash memory.
2781 To be able to re-map memory U-Boot then jumps to its link address.
2782 To be able to implement the initialization code in C, a (small!)
2783 initial stack is set up in the internal Dual Ported RAM (in case CPUs
2784 which provide such a feature like), or in a locked part of the data
2785 cache. After that, U-Boot initializes the CPU core, the caches and
2788 Next, all (potentially) available memory banks are mapped using a
2789 preliminary mapping. For example, we put them on 512 MB boundaries
2790 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
2791 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
2792 programmed for SDRAM access. Using the temporary configuration, a
2793 simple memory test is run that determines the size of the SDRAM
2796 When there is more than one SDRAM bank, and the banks are of
2797 different size, the largest is mapped first. For equal size, the first
2798 bank (CS2#) is mapped first. The first mapping is always for address
2799 0x00000000, with any additional banks following immediately to create
2800 contiguous memory starting from 0.
2802 Then, the monitor installs itself at the upper end of the SDRAM area
2803 and allocates memory for use by malloc() and for the global Board
2804 Info data; also, the exception vector code is copied to the low RAM
2805 pages, and the final stack is set up.
2807 Only after this relocation will you have a "normal" C environment;
2808 until that you are restricted in several ways, mostly because you are
2809 running from ROM, and because the code will have to be relocated to a
2813 U-Boot Porting Guide:
2814 ----------------------
2816 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
2820 int main(int argc, char *argv[])
2822 sighandler_t no_more_time;
2824 signal(SIGALRM, no_more_time);
2825 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
2827 if (available_money > available_manpower) {
2828 Pay consultant to port U-Boot;
2832 Download latest U-Boot source;
2834 Subscribe to u-boot mailing list;
2837 email("Hi, I am new to U-Boot, how do I get started?");
2840 Read the README file in the top level directory;
2841 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
2842 Read applicable doc/README.*;
2843 Read the source, Luke;
2844 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
2847 if (available_money > toLocalCurrency ($2500))
2850 Add a lot of aggravation and time;
2852 if (a similar board exists) { /* hopefully... */
2853 cp -a board/<similar> board/<myboard>
2854 cp include/configs/<similar>.h include/configs/<myboard>.h
2856 Create your own board support subdirectory;
2857 Create your own board include/configs/<myboard>.h file;
2859 Edit new board/<myboard> files
2860 Edit new include/configs/<myboard>.h
2865 Add / modify source code;
2869 email("Hi, I am having problems...");
2871 Send patch file to the U-Boot email list;
2872 if (reasonable critiques)
2873 Incorporate improvements from email list code review;
2875 Defend code as written;
2881 void no_more_time (int sig)
2890 All contributions to U-Boot should conform to the Linux kernel
2891 coding style; see the kernel coding style guide at
2892 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
2893 script "scripts/Lindent" in your Linux kernel source directory.
2895 Source files originating from a different project (for example the
2896 MTD subsystem) are generally exempt from these guidelines and are not
2897 reformatted to ease subsequent migration to newer versions of those
2900 Please note that U-Boot is implemented in C (and to some small parts in
2901 Assembler); no C++ is used, so please do not use C++ style comments (//)
2904 Please also stick to the following formatting rules:
2905 - remove any trailing white space
2906 - use TAB characters for indentation and vertical alignment, not spaces
2907 - make sure NOT to use DOS '\r\n' line feeds
2908 - do not add more than 2 consecutive empty lines to source files
2909 - do not add trailing empty lines to source files
2911 Submissions which do not conform to the standards may be returned
2912 with a request to reformat the changes.
2918 Since the number of patches for U-Boot is growing, we need to
2919 establish some rules. Submissions which do not conform to these rules
2920 may be rejected, even when they contain important and valuable stuff.
2922 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
2924 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
2925 see https://lists.denx.de/listinfo/u-boot
2927 When you send a patch, please include the following information with
2930 * For bug fixes: a description of the bug and how your patch fixes
2931 this bug. Please try to include a way of demonstrating that the
2932 patch actually fixes something.
2934 * For new features: a description of the feature and your
2937 * For major contributions, add a MAINTAINERS file with your
2938 information and associated file and directory references.
2940 * When you add support for a new board, don't forget to add a
2941 maintainer e-mail address to the boards.cfg file, too.
2943 * If your patch adds new configuration options, don't forget to
2944 document these in the README file.
2946 * The patch itself. If you are using git (which is *strongly*
2947 recommended) you can easily generate the patch using the
2948 "git format-patch". If you then use "git send-email" to send it to
2949 the U-Boot mailing list, you will avoid most of the common problems
2950 with some other mail clients.
2952 If you cannot use git, use "diff -purN OLD NEW". If your version of
2953 diff does not support these options, then get the latest version of
2956 The current directory when running this command shall be the parent
2957 directory of the U-Boot source tree (i. e. please make sure that
2958 your patch includes sufficient directory information for the
2961 We prefer patches as plain text. MIME attachments are discouraged,
2962 and compressed attachments must not be used.
2964 * If one logical set of modifications affects or creates several
2965 files, all these changes shall be submitted in a SINGLE patch file.
2967 * Changesets that contain different, unrelated modifications shall be
2968 submitted as SEPARATE patches, one patch per changeset.
2973 * Before sending the patch, run the buildman script on your patched
2974 source tree and make sure that no errors or warnings are reported
2975 for any of the boards.
2977 * Keep your modifications to the necessary minimum: A patch
2978 containing several unrelated changes or arbitrary reformats will be
2979 returned with a request to re-formatting / split it.
2981 * If you modify existing code, make sure that your new code does not
2982 add to the memory footprint of the code ;-) Small is beautiful!
2983 When adding new features, these should compile conditionally only
2984 (using #ifdef), and the resulting code with the new feature
2985 disabled must not need more memory than the old code without your
2988 * Remember that there is a size limit of 100 kB per message on the
2989 u-boot mailing list. Bigger patches will be moderated. If they are
2990 reasonable and not too big, they will be acknowledged. But patches
2991 bigger than the size limit should be avoided.