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 The same can be accomplished in a more flexible way
1075 for any variable by configuring the type of access
1076 to allow for those variables in the ".flags" variable
1077 or define CONFIG_ENV_FLAGS_LIST_STATIC.
1082 Define this variable to enable the reservation of
1083 "protected RAM", i. e. RAM which is not overwritten
1084 by U-Boot. Define CONFIG_PRAM to hold the number of
1085 kB you want to reserve for pRAM. You can overwrite
1086 this default value by defining an environment
1087 variable "pram" to the number of kB you want to
1088 reserve. Note that the board info structure will
1089 still show the full amount of RAM. If pRAM is
1090 reserved, a new environment variable "mem" will
1091 automatically be defined to hold the amount of
1092 remaining RAM in a form that can be passed as boot
1093 argument to Linux, for instance like that:
1095 setenv bootargs ... mem=\${mem}
1098 This way you can tell Linux not to use this memory,
1099 either, which results in a memory region that will
1100 not be affected by reboots.
1102 *WARNING* If your board configuration uses automatic
1103 detection of the RAM size, you must make sure that
1104 this memory test is non-destructive. So far, the
1105 following board configurations are known to be
1108 IVMS8, IVML24, SPD8xx,
1109 HERMES, IP860, RPXlite, LWMON,
1115 In the current implementation, the local variables
1116 space and global environment variables space are
1117 separated. Local variables are those you define by
1118 simply typing `name=value'. To access a local
1119 variable later on, you have write `$name' or
1120 `${name}'; to execute the contents of a variable
1121 directly type `$name' at the command prompt.
1123 Global environment variables are those you use
1124 setenv/printenv to work with. To run a command stored
1125 in such a variable, you need to use the run command,
1126 and you must not use the '$' sign to access them.
1128 To store commands and special characters in a
1129 variable, please use double quotation marks
1130 surrounding the whole text of the variable, instead
1131 of the backslashes before semicolons and special
1134 - Default Environment:
1135 CONFIG_EXTRA_ENV_SETTINGS
1137 Define this to contain any number of null terminated
1138 strings (variable = value pairs) that will be part of
1139 the default environment compiled into the boot image.
1141 For example, place something like this in your
1142 board's config file:
1144 #define CONFIG_EXTRA_ENV_SETTINGS \
1148 Warning: This method is based on knowledge about the
1149 internal format how the environment is stored by the
1150 U-Boot code. This is NOT an official, exported
1151 interface! Although it is unlikely that this format
1152 will change soon, there is no guarantee either.
1153 You better know what you are doing here.
1155 Note: overly (ab)use of the default environment is
1156 discouraged. Make sure to check other ways to preset
1157 the environment like the "source" command or the
1160 CONFIG_DELAY_ENVIRONMENT
1162 Normally the environment is loaded when the board is
1163 initialised so that it is available to U-Boot. This inhibits
1164 that so that the environment is not available until
1165 explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1166 this is instead controlled by the value of
1167 /config/load-environment.
1169 CONFIG_STANDALONE_LOAD_ADDR
1171 This option defines a board specific value for the
1172 address where standalone program gets loaded, thus
1173 overwriting the architecture dependent default
1176 - Automatic software updates via TFTP server
1178 CONFIG_UPDATE_TFTP_CNT_MAX
1179 CONFIG_UPDATE_TFTP_MSEC_MAX
1181 These options enable and control the auto-update feature;
1182 for a more detailed description refer to doc/README.update.
1184 - MTD Support (mtdparts command, UBI support)
1185 CONFIG_MTD_UBI_WL_THRESHOLD
1186 This parameter defines the maximum difference between the highest
1187 erase counter value and the lowest erase counter value of eraseblocks
1188 of UBI devices. When this threshold is exceeded, UBI starts performing
1189 wear leveling by means of moving data from eraseblock with low erase
1190 counter to eraseblocks with high erase counter.
1192 The default value should be OK for SLC NAND flashes, NOR flashes and
1193 other flashes which have eraseblock life-cycle 100000 or more.
1194 However, in case of MLC NAND flashes which typically have eraseblock
1195 life-cycle less than 10000, the threshold should be lessened (e.g.,
1196 to 128 or 256, although it does not have to be power of 2).
1200 CONFIG_MTD_UBI_BEB_LIMIT
1201 This option specifies the maximum bad physical eraseblocks UBI
1202 expects on the MTD device (per 1024 eraseblocks). If the
1203 underlying flash does not admit of bad eraseblocks (e.g. NOR
1204 flash), this value is ignored.
1206 NAND datasheets often specify the minimum and maximum NVM
1207 (Number of Valid Blocks) for the flashes' endurance lifetime.
1208 The maximum expected bad eraseblocks per 1024 eraseblocks
1209 then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
1210 which gives 20 for most NANDs (MaxNVB is basically the total
1211 count of eraseblocks on the chip).
1213 To put it differently, if this value is 20, UBI will try to
1214 reserve about 1.9% of physical eraseblocks for bad blocks
1215 handling. And that will be 1.9% of eraseblocks on the entire
1216 NAND chip, not just the MTD partition UBI attaches. This means
1217 that if you have, say, a NAND flash chip admits maximum 40 bad
1218 eraseblocks, and it is split on two MTD partitions of the same
1219 size, UBI will reserve 40 eraseblocks when attaching a
1224 CONFIG_MTD_UBI_FASTMAP
1225 Fastmap is a mechanism which allows attaching an UBI device
1226 in nearly constant time. Instead of scanning the whole MTD device it
1227 only has to locate a checkpoint (called fastmap) on the device.
1228 The on-flash fastmap contains all information needed to attach
1229 the device. Using fastmap makes only sense on large devices where
1230 attaching by scanning takes long. UBI will not automatically install
1231 a fastmap on old images, but you can set the UBI parameter
1232 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
1233 that fastmap-enabled images are still usable with UBI implementations
1234 without fastmap support. On typical flash devices the whole fastmap
1235 fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
1237 CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
1238 Set this parameter to enable fastmap automatically on images
1242 CONFIG_MTD_UBI_FM_DEBUG
1243 Enable UBI fastmap debug
1248 Enable building of SPL globally.
1250 CONFIG_SPL_PANIC_ON_RAW_IMAGE
1251 When defined, SPL will panic() if the image it has
1252 loaded does not have a signature.
1253 Defining this is useful when code which loads images
1254 in SPL cannot guarantee that absolutely all read errors
1256 An example is the LPC32XX MLC NAND driver, which will
1257 consider that a completely unreadable NAND block is bad,
1258 and thus should be skipped silently.
1260 CONFIG_SPL_DISPLAY_PRINT
1261 For ARM, enable an optional function to print more information
1262 about the running system.
1264 CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
1265 Set this for NAND SPL on PPC mpc83xx targets, so that
1266 start.S waits for the rest of the SPL to load before
1267 continuing (the hardware starts execution after just
1268 loading the first page rather than the full 4K).
1271 Support for a lightweight UBI (fastmap) scanner and
1274 CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
1275 CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
1276 CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
1277 CFG_SYS_NAND_ECCPOS, CFG_SYS_NAND_ECCSIZE,
1278 CFG_SYS_NAND_ECCBYTES
1279 Defines the size and behavior of the NAND that SPL uses
1282 CFG_SYS_NAND_U_BOOT_DST
1283 Location in memory to load U-Boot to
1285 CFG_SYS_NAND_U_BOOT_SIZE
1286 Size of image to load
1288 CFG_SYS_NAND_U_BOOT_START
1289 Entry point in loaded image to jump to
1291 CONFIG_SPL_RAM_DEVICE
1292 Support for running image already present in ram, in SPL binary
1294 CONFIG_SPL_FIT_PRINT
1295 Printing information about a FIT image adds quite a bit of
1296 code to SPL. So this is normally disabled in SPL. Use this
1297 option to re-enable it. This will affect the output of the
1298 bootm command when booting a FIT image.
1300 - Interrupt support (PPC):
1302 There are common interrupt_init() and timer_interrupt()
1303 for all PPC archs. interrupt_init() calls interrupt_init_cpu()
1304 for CPU specific initialization. interrupt_init_cpu()
1305 should set decrementer_count to appropriate value. If
1306 CPU resets decrementer automatically after interrupt
1307 (ppc4xx) it should set decrementer_count to zero.
1308 timer_interrupt() calls timer_interrupt_cpu() for CPU
1309 specific handling. If board has watchdog / status_led
1310 / other_activity_monitor it works automatically from
1311 general timer_interrupt().
1314 Board initialization settings:
1315 ------------------------------
1317 During Initialization u-boot calls a number of board specific functions
1318 to allow the preparation of board specific prerequisites, e.g. pin setup
1319 before drivers are initialized. To enable these callbacks the
1320 following configuration macros have to be defined. Currently this is
1321 architecture specific, so please check arch/your_architecture/lib/board.c
1322 typically in board_init_f() and board_init_r().
1324 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
1325 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
1326 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
1328 Configuration Settings:
1329 -----------------------
1331 - MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
1332 Optionally it can be defined to support 64-bit memory commands.
1334 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
1335 undefine this when you're short of memory.
1337 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
1338 width of the commands listed in the 'help' command output.
1340 - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
1341 prompt for user input.
1343 - CFG_SYS_BAUDRATE_TABLE:
1344 List of legal baudrate settings for this board.
1346 - CFG_SYS_MEM_RESERVE_SECURE
1347 Only implemented for ARMv8 for now.
1348 If defined, the size of CFG_SYS_MEM_RESERVE_SECURE memory
1349 is substracted from total RAM and won't be reported to OS.
1350 This memory can be used as secure memory. A variable
1351 gd->arch.secure_ram is used to track the location. In systems
1352 the RAM base is not zero, or RAM is divided into banks,
1353 this variable needs to be recalcuated to get the address.
1355 - CFG_SYS_SDRAM_BASE:
1356 Physical start address of SDRAM. _Must_ be 0 here.
1358 - CFG_SYS_FLASH_BASE:
1359 Physical start address of Flash memory.
1361 - CONFIG_SYS_MALLOC_LEN:
1362 Size of DRAM reserved for malloc() use.
1364 - CONFIG_SYS_MALLOC_F_LEN
1365 Size of the malloc() pool for use before relocation. If
1366 this is defined, then a very simple malloc() implementation
1367 will become available before relocation. The address is just
1368 below the global data, and the stack is moved down to make
1371 This feature allocates regions with increasing addresses
1372 within the region. calloc() is supported, but realloc()
1373 is not available. free() is supported but does nothing.
1374 The memory will be freed (or in fact just forgotten) when
1375 U-Boot relocates itself.
1377 - CONFIG_SYS_MALLOC_SIMPLE
1378 Provides a simple and small malloc() and calloc() for those
1379 boards which do not use the full malloc in SPL (which is
1380 enabled with CONFIG_SYS_SPL_MALLOC).
1382 - CFG_SYS_BOOTMAPSZ:
1383 Maximum size of memory mapped by the startup code of
1384 the Linux kernel; all data that must be processed by
1385 the Linux kernel (bd_info, boot arguments, FDT blob if
1386 used) must be put below this limit, unless "bootm_low"
1387 environment variable is defined and non-zero. In such case
1388 all data for the Linux kernel must be between "bootm_low"
1389 and "bootm_low" + CFG_SYS_BOOTMAPSZ. The environment
1390 variable "bootm_mapsize" will override the value of
1391 CFG_SYS_BOOTMAPSZ. If CFG_SYS_BOOTMAPSZ is undefined,
1392 then the value in "bootm_size" will be used instead.
1394 - CONFIG_SYS_BOOT_GET_CMDLINE:
1395 Enables allocating and saving kernel cmdline in space between
1396 "bootm_low" and "bootm_low" + BOOTMAPSZ.
1398 - CONFIG_SYS_BOOT_GET_KBD:
1399 Enables allocating and saving a kernel copy of the bd_info in
1400 space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
1402 - CONFIG_SYS_FLASH_PROTECTION
1403 If defined, hardware flash sectors protection is used
1404 instead of U-Boot software protection.
1406 - CONFIG_SYS_FLASH_CFI:
1407 Define if the flash driver uses extra elements in the
1408 common flash structure for storing flash geometry.
1410 - CONFIG_FLASH_CFI_DRIVER
1411 This option also enables the building of the cfi_flash driver
1412 in the drivers directory
1414 - CONFIG_FLASH_CFI_MTD
1415 This option enables the building of the cfi_mtd driver
1416 in the drivers directory. The driver exports CFI flash
1419 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
1420 Use buffered writes to flash.
1422 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1423 - CONFIG_ENV_FLAGS_LIST_STATIC
1424 Enable validation of the values given to environment variables when
1425 calling env set. Variables can be restricted to only decimal,
1426 hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
1427 the variables can also be restricted to IP address or MAC address.
1429 The format of the list is:
1430 type_attribute = [s|d|x|b|i|m]
1431 access_attribute = [a|r|o|c]
1432 attributes = type_attribute[access_attribute]
1433 entry = variable_name[:attributes]
1436 The type attributes are:
1437 s - String (default)
1440 b - Boolean ([1yYtT|0nNfF])
1444 The access attributes are:
1450 - CONFIG_ENV_FLAGS_LIST_DEFAULT
1451 Define this to a list (string) to define the ".flags"
1452 environment variable in the default or embedded environment.
1454 - CONFIG_ENV_FLAGS_LIST_STATIC
1455 Define this to a list (string) to define validation that
1456 should be done if an entry is not found in the ".flags"
1457 environment variable. To override a setting in the static
1458 list, simply add an entry for the same variable name to the
1461 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
1462 regular expression. This allows multiple variables to define the same
1463 flags without explicitly listing them for each variable.
1465 The following definitions that deal with the placement and management
1466 of environment data (variable area); in general, we support the
1467 following configurations:
1469 BE CAREFUL! The first access to the environment happens quite early
1470 in U-Boot initialization (when we try to get the setting of for the
1471 console baudrate). You *MUST* have mapped your NVRAM area then, or
1474 Please note that even with NVRAM we still use a copy of the
1475 environment in RAM: we could work on NVRAM directly, but we want to
1476 keep settings there always unmodified except somebody uses "saveenv"
1477 to save the current settings.
1479 BE CAREFUL! For some special cases, the local device can not use
1480 "saveenv" command. For example, the local device will get the
1481 environment stored in a remote NOR flash by SRIO or PCIE link,
1482 but it can not erase, write this NOR flash by SRIO or PCIE interface.
1484 - CONFIG_NAND_ENV_DST
1486 Defines address in RAM to which the nand_spl code should copy the
1487 environment. If redundant environment is used, it will be copied to
1488 CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
1490 Please note that the environment is read-only until the monitor
1491 has been relocated to RAM and a RAM copy of the environment has been
1492 created; also, when using EEPROM you will have to use env_get_f()
1493 until then to read environment variables.
1495 The environment is protected by a CRC32 checksum. Before the monitor
1496 is relocated into RAM, as a result of a bad CRC you will be working
1497 with the compiled-in default environment - *silently*!!! [This is
1498 necessary, because the first environment variable we need is the
1499 "baudrate" setting for the console - if we have a bad CRC, we don't
1500 have any device yet where we could complain.]
1502 Note: once the monitor has been relocated, then it will complain if
1503 the default environment is used; a new CRC is computed as soon as you
1504 use the "saveenv" command to store a valid environment.
1506 - CONFIG_SYS_FAULT_MII_ADDR:
1507 MII address of the PHY to check for the Ethernet link state.
1509 - CONFIG_DISPLAY_BOARDINFO
1510 Display information about the board that U-Boot is running on
1511 when U-Boot starts up. The board function checkboard() is called
1514 - CONFIG_DISPLAY_BOARDINFO_LATE
1515 Similar to the previous option, but display this information
1516 later, once stdio is running and output goes to the LCD, if
1519 Low Level (hardware related) configuration options:
1520 ---------------------------------------------------
1522 - CONFIG_SYS_CACHELINE_SIZE:
1523 Cache Line Size of the CPU.
1525 - CONFIG_SYS_CCSRBAR_DEFAULT:
1526 Default (power-on reset) physical address of CCSR on Freescale
1530 Virtual address of CCSR. On a 32-bit build, this is typically
1531 the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
1533 - CFG_SYS_CCSRBAR_PHYS:
1534 Physical address of CCSR. CCSR can be relocated to a new
1535 physical address, if desired. In this case, this macro should
1536 be set to that address. Otherwise, it should be set to the
1537 same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
1538 is typically relocated on 36-bit builds. It is recommended
1539 that this macro be defined via the _HIGH and _LOW macros:
1541 #define CFG_SYS_CCSRBAR_PHYS ((CFG_SYS_CCSRBAR_PHYS_HIGH
1542 * 1ull) << 32 | CFG_SYS_CCSRBAR_PHYS_LOW)
1544 - CFG_SYS_CCSRBAR_PHYS_HIGH:
1545 Bits 33-36 of CFG_SYS_CCSRBAR_PHYS. This value is typically
1546 either 0 (32-bit build) or 0xF (36-bit build). This macro is
1547 used in assembly code, so it must not contain typecasts or
1548 integer size suffixes (e.g. "ULL").
1550 - CFG_SYS_CCSRBAR_PHYS_LOW:
1551 Lower 32-bits of CFG_SYS_CCSRBAR_PHYS. This macro is
1552 used in assembly code, so it must not contain typecasts or
1553 integer size suffixes (e.g. "ULL").
1555 - CONFIG_SYS_IMMR: Physical address of the Internal Memory.
1556 DO NOT CHANGE unless you know exactly what you're
1557 doing! (11-4) [MPC8xx systems only]
1559 - CFG_SYS_INIT_RAM_ADDR:
1561 Start address of memory area that can be used for
1562 initial data and stack; please note that this must be
1563 writable memory that is working WITHOUT special
1564 initialization, i. e. you CANNOT use normal RAM which
1565 will become available only after programming the
1566 memory controller and running certain initialization
1569 U-Boot uses the following memory types:
1570 - MPC8xx: IMMR (internal memory of the CPU)
1572 - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27)
1574 - CONFIG_SYS_OR_TIMING_SDRAM:
1577 - CONFIG_SYS_SRIOn_MEM_VIRT:
1578 Virtual Address of SRIO port 'n' memory region
1580 - CONFIG_SYS_SRIOn_MEM_PHYxS:
1581 Physical Address of SRIO port 'n' memory region
1583 - CONFIG_SYS_SRIOn_MEM_SIZE:
1584 Size of SRIO port 'n' memory region
1586 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
1587 Defined to tell the NAND controller that the NAND chip is using
1589 Not all NAND drivers use this symbol.
1590 Example of drivers that use it:
1591 - drivers/mtd/nand/raw/ndfc.c
1592 - drivers/mtd/nand/raw/mxc_nand.c
1594 - CONFIG_SYS_NDFC_EBC0_CFG
1595 Sets the EBC0_CFG register for the NDFC. If not defined
1596 a default value will be used.
1598 - CONFIG_SYS_SPD_BUS_NUM
1599 If SPD EEPROM is on an I2C bus other than the first
1600 one, specify here. Note that the value must resolve
1601 to something your driver can deal with.
1603 - CONFIG_FSL_DDR_INTERACTIVE
1604 Enable interactive DDR debugging. See doc/README.fsl-ddr.
1606 - CONFIG_FSL_DDR_SYNC_REFRESH
1607 Enable sync of refresh for multiple controllers.
1609 - CONFIG_FSL_DDR_BIST
1610 Enable built-in memory test for Freescale DDR controllers.
1613 Enable RMII mode for all FECs.
1614 Note that this is a global option, we can't
1615 have one FEC in standard MII mode and another in RMII mode.
1617 - CONFIG_CRC32_VERIFY
1618 Add a verify option to the crc32 command.
1621 => crc32 -v <address> <count> <crc32>
1623 Where address/count indicate a memory area
1624 and crc32 is the correct crc32 which the
1628 Add the "loopw" memory command. This only takes effect if
1629 the memory commands are activated globally (CONFIG_CMD_MEMORY).
1631 - CONFIG_CMD_MX_CYCLIC
1632 Add the "mdc" and "mwc" memory commands. These are cyclic
1637 This command will print 4 bytes (10,11,12,13) each 500 ms.
1639 => mwc.l 100 12345678 10
1640 This command will write 12345678 to address 100 all 10 ms.
1642 This only takes effect if the memory commands are activated
1643 globally (CONFIG_CMD_MEMORY).
1646 Set when the currently-running compilation is for an artifact
1647 that will end up in the SPL (as opposed to the TPL or U-Boot
1648 proper). Code that needs stage-specific behavior should check
1652 Set when the currently-running compilation is for an artifact
1653 that will end up in the TPL (as opposed to the SPL or U-Boot
1654 proper). Code that needs stage-specific behavior should check
1657 - CONFIG_ARCH_MAP_SYSMEM
1658 Generally U-Boot (and in particular the md command) uses
1659 effective address. It is therefore not necessary to regard
1660 U-Boot address as virtual addresses that need to be translated
1661 to physical addresses. However, sandbox requires this, since
1662 it maintains its own little RAM buffer which contains all
1663 addressable memory. This option causes some memory accesses
1664 to be mapped through map_sysmem() / unmap_sysmem().
1666 - CONFIG_X86_RESET_VECTOR
1667 If defined, the x86 reset vector code is included. This is not
1668 needed when U-Boot is running from Coreboot.
1670 Freescale QE/FMAN Firmware Support:
1671 -----------------------------------
1673 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
1674 loading of "firmware", which is encoded in the QE firmware binary format.
1675 This firmware often needs to be loaded during U-Boot booting, so macros
1676 are used to identify the storage device (NOR flash, SPI, etc) and the address
1679 - CONFIG_SYS_FMAN_FW_ADDR
1680 The address in the storage device where the FMAN microcode is located. The
1681 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1684 - CONFIG_SYS_QE_FW_ADDR
1685 The address in the storage device where the QE microcode is located. The
1686 meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
1689 - CONFIG_SYS_QE_FMAN_FW_LENGTH
1690 The maximum possible size of the firmware. The firmware binary format
1691 has a field that specifies the actual size of the firmware, but it
1692 might not be possible to read any part of the firmware unless some
1693 local storage is allocated to hold the entire firmware first.
1695 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
1696 Specifies that QE/FMAN firmware is located in NOR flash, mapped as
1697 normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the
1698 virtual address in NOR flash.
1700 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
1701 Specifies that QE/FMAN firmware is located in NAND flash.
1702 CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
1704 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
1705 Specifies that QE/FMAN firmware is located on the primary SD/MMC
1706 device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
1708 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
1709 Specifies that QE/FMAN firmware is located in the remote (master)
1710 memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
1711 can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
1712 window->master inbound window->master LAW->the ucode address in
1713 master's memory space.
1715 Freescale Layerscape Management Complex Firmware Support:
1716 ---------------------------------------------------------
1717 The Freescale Layerscape Management Complex (MC) supports the loading of
1719 This firmware often needs to be loaded during U-Boot booting, so macros
1720 are used to identify the storage device (NOR flash, SPI, etc) and the address
1723 - CONFIG_FSL_MC_ENET
1724 Enable the MC driver for Layerscape SoCs.
1726 Freescale Layerscape Debug Server Support:
1727 -------------------------------------------
1728 The Freescale Layerscape Debug Server Support supports the loading of
1729 "Debug Server firmware" and triggering SP boot-rom.
1730 This firmware often needs to be loaded during U-Boot booting.
1732 - CONFIG_SYS_MC_RSV_MEM_ALIGN
1733 Define alignment of reserved memory MC requires
1738 In order to achieve reproducible builds, timestamps used in the U-Boot build
1739 process have to be set to a fixed value.
1741 This is done using the SOURCE_DATE_EPOCH environment variable.
1742 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
1743 option for U-Boot or an environment variable in U-Boot.
1745 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
1747 Building the Software:
1748 ======================
1750 Building U-Boot has been tested in several native build environments
1751 and in many different cross environments. Of course we cannot support
1752 all possibly existing versions of cross development tools in all
1753 (potentially obsolete) versions. In case of tool chain problems we
1754 recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
1755 which is extensively used to build and test U-Boot.
1757 If you are not using a native environment, it is assumed that you
1758 have GNU cross compiling tools available in your path. In this case,
1759 you must set the environment variable CROSS_COMPILE in your shell.
1760 Note that no changes to the Makefile or any other source files are
1761 necessary. For example using the ELDK on a 4xx CPU, please enter:
1763 $ CROSS_COMPILE=ppc_4xx-
1764 $ export CROSS_COMPILE
1766 U-Boot is intended to be simple to build. After installing the
1767 sources you must configure U-Boot for one specific board type. This
1772 where "NAME_defconfig" is the name of one of the existing configu-
1773 rations; see configs/*_defconfig for supported names.
1775 Note: for some boards special configuration names may exist; check if
1776 additional information is available from the board vendor; for
1777 instance, the TQM823L systems are available without (standard)
1778 or with LCD support. You can select such additional "features"
1779 when choosing the configuration, i. e.
1781 make TQM823L_defconfig
1782 - will configure for a plain TQM823L, i. e. no LCD support
1784 make TQM823L_LCD_defconfig
1785 - will configure for a TQM823L with U-Boot console on LCD
1790 Finally, type "make all", and you should get some working U-Boot
1791 images ready for download to / installation on your system:
1793 - "u-boot.bin" is a raw binary image
1794 - "u-boot" is an image in ELF binary format
1795 - "u-boot.srec" is in Motorola S-Record format
1797 By default the build is performed locally and the objects are saved
1798 in the source directory. One of the two methods can be used to change
1799 this behavior and build U-Boot to some external directory:
1801 1. Add O= to the make command line invocations:
1803 make O=/tmp/build distclean
1804 make O=/tmp/build NAME_defconfig
1805 make O=/tmp/build all
1807 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
1809 export KBUILD_OUTPUT=/tmp/build
1814 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
1817 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
1818 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
1819 For example to treat all compiler warnings as errors:
1821 make KCFLAGS=-Werror
1823 Please be aware that the Makefiles assume you are using GNU make, so
1824 for instance on NetBSD you might need to use "gmake" instead of
1828 If the system board that you have is not listed, then you will need
1829 to port U-Boot to your hardware platform. To do this, follow these
1832 1. Create a new directory to hold your board specific code. Add any
1833 files you need. In your board directory, you will need at least
1834 the "Makefile" and a "<board>.c".
1835 2. Create a new configuration file "include/configs/<board>.h" for
1837 3. If you're porting U-Boot to a new CPU, then also create a new
1838 directory to hold your CPU specific code. Add any files you need.
1839 4. Run "make <board>_defconfig" with your new name.
1840 5. Type "make", and you should get a working "u-boot.srec" file
1841 to be installed on your target system.
1842 6. Debug and solve any problems that might arise.
1843 [Of course, this last step is much harder than it sounds.]
1846 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
1847 ==============================================================
1849 If you have modified U-Boot sources (for instance added a new board
1850 or support for new devices, a new CPU, etc.) you are expected to
1851 provide feedback to the other developers. The feedback normally takes
1852 the form of a "patch", i.e. a context diff against a certain (latest
1853 official or latest in the git repository) version of U-Boot sources.
1855 But before you submit such a patch, please verify that your modifi-
1856 cation did not break existing code. At least make sure that *ALL* of
1857 the supported boards compile WITHOUT ANY compiler warnings. To do so,
1858 just run the buildman script (tools/buildman/buildman), which will
1859 configure and build U-Boot for ALL supported system. Be warned, this
1860 will take a while. Please see the buildman README, or run 'buildman -H'
1864 See also "U-Boot Porting Guide" below.
1867 Monitor Commands - Overview:
1868 ============================
1870 go - start application at address 'addr'
1871 run - run commands in an environment variable
1872 bootm - boot application image from memory
1873 bootp - boot image via network using BootP/TFTP protocol
1874 bootz - boot zImage from memory
1875 tftpboot- boot image via network using TFTP protocol
1876 and env variables "ipaddr" and "serverip"
1877 (and eventually "gatewayip")
1878 tftpput - upload a file via network using TFTP protocol
1879 rarpboot- boot image via network using RARP/TFTP protocol
1880 diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
1881 loads - load S-Record file over serial line
1882 loadb - load binary file over serial line (kermit mode)
1883 loadm - load binary blob from source address to destination address
1885 mm - memory modify (auto-incrementing)
1886 nm - memory modify (constant address)
1887 mw - memory write (fill)
1890 cmp - memory compare
1891 crc32 - checksum calculation
1892 i2c - I2C sub-system
1893 sspi - SPI utility commands
1894 base - print or set address offset
1895 printenv- print environment variables
1896 pwm - control pwm channels
1897 setenv - set environment variables
1898 saveenv - save environment variables to persistent storage
1899 protect - enable or disable FLASH write protection
1900 erase - erase FLASH memory
1901 flinfo - print FLASH memory information
1902 nand - NAND memory operations (see doc/README.nand)
1903 bdinfo - print Board Info structure
1904 iminfo - print header information for application image
1905 coninfo - print console devices and informations
1906 ide - IDE sub-system
1907 loop - infinite loop on address range
1908 loopw - infinite write loop on address range
1909 mtest - simple RAM test
1910 icache - enable or disable instruction cache
1911 dcache - enable or disable data cache
1912 reset - Perform RESET of the CPU
1913 echo - echo args to console
1914 version - print monitor version
1915 help - print online help
1916 ? - alias for 'help'
1919 Monitor Commands - Detailed Description:
1920 ========================================
1924 For now: just type "help <command>".
1927 Note for Redundant Ethernet Interfaces:
1928 =======================================
1930 Some boards come with redundant Ethernet interfaces; U-Boot supports
1931 such configurations and is capable of automatic selection of a
1932 "working" interface when needed. MAC assignment works as follows:
1934 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
1935 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
1936 "eth1addr" (=>eth1), "eth2addr", ...
1938 If the network interface stores some valid MAC address (for instance
1939 in SROM), this is used as default address if there is NO correspon-
1940 ding setting in the environment; if the corresponding environment
1941 variable is set, this overrides the settings in the card; that means:
1943 o If the SROM has a valid MAC address, and there is no address in the
1944 environment, the SROM's address is used.
1946 o If there is no valid address in the SROM, and a definition in the
1947 environment exists, then the value from the environment variable is
1950 o If both the SROM and the environment contain a MAC address, and
1951 both addresses are the same, this MAC address is used.
1953 o If both the SROM and the environment contain a MAC address, and the
1954 addresses differ, the value from the environment is used and a
1957 o If neither SROM nor the environment contain a MAC address, an error
1958 is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
1959 a random, locally-assigned MAC is used.
1961 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
1962 will be programmed into hardware as part of the initialization process. This
1963 may be skipped by setting the appropriate 'ethmacskip' environment variable.
1964 The naming convention is as follows:
1965 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
1970 U-Boot is capable of booting (and performing other auxiliary operations on)
1971 images in two formats:
1973 New uImage format (FIT)
1974 -----------------------
1976 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
1977 to Flattened Device Tree). It allows the use of images with multiple
1978 components (several kernels, ramdisks, etc.), with contents protected by
1979 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
1985 Old image format is based on binary files which can be basically anything,
1986 preceded by a special header; see the definitions in include/image.h for
1987 details; basically, the header defines the following image properties:
1989 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
1990 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
1991 LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
1992 Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY).
1993 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
1994 IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
1995 Currently supported: ARM, Intel x86, MIPS, Nios II, PowerPC).
1996 * Compression Type (uncompressed, gzip, bzip2)
2002 The header is marked by a special Magic Number, and both the header
2003 and the data portions of the image are secured against corruption by
2010 Although U-Boot should support any OS or standalone application
2011 easily, the main focus has always been on Linux during the design of
2014 U-Boot includes many features that so far have been part of some
2015 special "boot loader" code within the Linux kernel. Also, any
2016 "initrd" images to be used are no longer part of one big Linux image;
2017 instead, kernel and "initrd" are separate images. This implementation
2018 serves several purposes:
2020 - the same features can be used for other OS or standalone
2021 applications (for instance: using compressed images to reduce the
2022 Flash memory footprint)
2024 - it becomes much easier to port new Linux kernel versions because
2025 lots of low-level, hardware dependent stuff are done by U-Boot
2027 - the same Linux kernel image can now be used with different "initrd"
2028 images; of course this also means that different kernel images can
2029 be run with the same "initrd". This makes testing easier (you don't
2030 have to build a new "zImage.initrd" Linux image when you just
2031 change a file in your "initrd"). Also, a field-upgrade of the
2032 software is easier now.
2038 Porting Linux to U-Boot based systems:
2039 ---------------------------------------
2041 U-Boot cannot save you from doing all the necessary modifications to
2042 configure the Linux device drivers for use with your target hardware
2043 (no, we don't intend to provide a full virtual machine interface to
2046 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
2048 Just make sure your machine specific header file (for instance
2049 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2050 Information structure as we define in include/asm-<arch>/u-boot.h,
2051 and make sure that your definition of IMAP_ADDR uses the same value
2052 as your U-Boot configuration in CONFIG_SYS_IMMR.
2054 Note that U-Boot now has a driver model, a unified model for drivers.
2055 If you are adding a new driver, plumb it into driver model. If there
2056 is no uclass available, you are encouraged to create one. See
2060 Configuring the Linux kernel:
2061 -----------------------------
2063 No specific requirements for U-Boot. Make sure you have some root
2064 device (initial ramdisk, NFS) for your target system.
2067 Building a Linux Image:
2068 -----------------------
2070 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2071 not used. If you use recent kernel source, a new build target
2072 "uImage" will exist which automatically builds an image usable by
2073 U-Boot. Most older kernels also have support for a "pImage" target,
2074 which was introduced for our predecessor project PPCBoot and uses a
2075 100% compatible format.
2079 make TQM850L_defconfig
2084 The "uImage" build target uses a special tool (in 'tools/mkimage') to
2085 encapsulate a compressed Linux kernel image with header information,
2086 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2088 * build a standard "vmlinux" kernel image (in ELF binary format):
2090 * convert the kernel into a raw binary image:
2092 ${CROSS_COMPILE}-objcopy -O binary \
2093 -R .note -R .comment \
2094 -S vmlinux linux.bin
2096 * compress the binary image:
2100 * package compressed binary image for U-Boot:
2102 mkimage -A ppc -O linux -T kernel -C gzip \
2103 -a 0 -e 0 -n "Linux Kernel Image" \
2104 -d linux.bin.gz uImage
2107 The "mkimage" tool can also be used to create ramdisk images for use
2108 with U-Boot, either separated from the Linux kernel image, or
2109 combined into one file. "mkimage" encapsulates the images with a 64
2110 byte header containing information about target architecture,
2111 operating system, image type, compression method, entry points, time
2112 stamp, CRC32 checksums, etc.
2114 "mkimage" can be called in two ways: to verify existing images and
2115 print the header information, or to build new images.
2117 In the first form (with "-l" option) mkimage lists the information
2118 contained in the header of an existing U-Boot image; this includes
2119 checksum verification:
2121 tools/mkimage -l image
2122 -l ==> list image header information
2124 The second form (with "-d" option) is used to build a U-Boot image
2125 from a "data file" which is used as image payload:
2127 tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
2128 -n name -d data_file image
2129 -A ==> set architecture to 'arch'
2130 -O ==> set operating system to 'os'
2131 -T ==> set image type to 'type'
2132 -C ==> set compression type 'comp'
2133 -a ==> set load address to 'addr' (hex)
2134 -e ==> set entry point to 'ep' (hex)
2135 -n ==> set image name to 'name'
2136 -d ==> use image data from 'datafile'
2138 Right now, all Linux kernels for PowerPC systems use the same load
2139 address (0x00000000), but the entry point address depends on the
2142 - 2.2.x kernels have the entry point at 0x0000000C,
2143 - 2.3.x and later kernels have the entry point at 0x00000000.
2145 So a typical call to build a U-Boot image would read:
2147 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2148 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
2149 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
2150 > examples/uImage.TQM850L
2151 Image Name: 2.4.4 kernel for TQM850L
2152 Created: Wed Jul 19 02:34:59 2000
2153 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2154 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2155 Load Address: 0x00000000
2156 Entry Point: 0x00000000
2158 To verify the contents of the image (or check for corruption):
2160 -> tools/mkimage -l examples/uImage.TQM850L
2161 Image Name: 2.4.4 kernel for TQM850L
2162 Created: Wed Jul 19 02:34:59 2000
2163 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2164 Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
2165 Load Address: 0x00000000
2166 Entry Point: 0x00000000
2168 NOTE: for embedded systems where boot time is critical you can trade
2169 speed for memory and install an UNCOMPRESSED image instead: this
2170 needs more space in Flash, but boots much faster since it does not
2171 need to be uncompressed:
2173 -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
2174 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2175 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
2176 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
2177 > examples/uImage.TQM850L-uncompressed
2178 Image Name: 2.4.4 kernel for TQM850L
2179 Created: Wed Jul 19 02:34:59 2000
2180 Image Type: PowerPC Linux Kernel Image (uncompressed)
2181 Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
2182 Load Address: 0x00000000
2183 Entry Point: 0x00000000
2186 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
2187 when your kernel is intended to use an initial ramdisk:
2189 -> tools/mkimage -n 'Simple Ramdisk Image' \
2190 > -A ppc -O linux -T ramdisk -C gzip \
2191 > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
2192 Image Name: Simple Ramdisk Image
2193 Created: Wed Jan 12 14:01:50 2000
2194 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2195 Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
2196 Load Address: 0x00000000
2197 Entry Point: 0x00000000
2199 The "dumpimage" tool can be used to disassemble or list the contents of images
2200 built by mkimage. See dumpimage's help output (-h) for details.
2202 Installing a Linux Image:
2203 -------------------------
2205 To downloading a U-Boot image over the serial (console) interface,
2206 you must convert the image to S-Record format:
2208 objcopy -I binary -O srec examples/image examples/image.srec
2210 The 'objcopy' does not understand the information in the U-Boot
2211 image header, so the resulting S-Record file will be relative to
2212 address 0x00000000. To load it to a given address, you need to
2213 specify the target address as 'offset' parameter with the 'loads'
2216 Example: install the image to address 0x40100000 (which on the
2217 TQM8xxL is in the first Flash bank):
2219 => erase 40100000 401FFFFF
2225 ## Ready for S-Record download ...
2226 ~>examples/image.srec
2227 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
2229 15989 15990 15991 15992
2230 [file transfer complete]
2232 ## Start Addr = 0x00000000
2235 You can check the success of the download using the 'iminfo' command;
2236 this includes a checksum verification so you can be sure no data
2237 corruption happened:
2241 ## Checking Image at 40100000 ...
2242 Image Name: 2.2.13 for initrd on TQM850L
2243 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2244 Data Size: 335725 Bytes = 327 kB = 0 MB
2245 Load Address: 00000000
2246 Entry Point: 0000000c
2247 Verifying Checksum ... OK
2253 The "bootm" command is used to boot an application that is stored in
2254 memory (RAM or Flash). In case of a Linux kernel image, the contents
2255 of the "bootargs" environment variable is passed to the kernel as
2256 parameters. You can check and modify this variable using the
2257 "printenv" and "setenv" commands:
2260 => printenv bootargs
2261 bootargs=root=/dev/ram
2263 => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2265 => printenv bootargs
2266 bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2269 ## Booting Linux kernel at 40020000 ...
2270 Image Name: 2.2.13 for NFS on TQM850L
2271 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2272 Data Size: 381681 Bytes = 372 kB = 0 MB
2273 Load Address: 00000000
2274 Entry Point: 0000000c
2275 Verifying Checksum ... OK
2276 Uncompressing Kernel Image ... OK
2277 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
2278 Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2279 time_init: decrementer frequency = 187500000/60
2280 Calibrating delay loop... 49.77 BogoMIPS
2281 Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
2284 If you want to boot a Linux kernel with initial RAM disk, you pass
2285 the memory addresses of both the kernel and the initrd image (PPBCOOT
2286 format!) to the "bootm" command:
2288 => imi 40100000 40200000
2290 ## Checking Image at 40100000 ...
2291 Image Name: 2.2.13 for initrd on TQM850L
2292 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2293 Data Size: 335725 Bytes = 327 kB = 0 MB
2294 Load Address: 00000000
2295 Entry Point: 0000000c
2296 Verifying Checksum ... OK
2298 ## Checking Image at 40200000 ...
2299 Image Name: Simple Ramdisk Image
2300 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2301 Data Size: 566530 Bytes = 553 kB = 0 MB
2302 Load Address: 00000000
2303 Entry Point: 00000000
2304 Verifying Checksum ... OK
2306 => bootm 40100000 40200000
2307 ## Booting Linux kernel at 40100000 ...
2308 Image Name: 2.2.13 for initrd on TQM850L
2309 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2310 Data Size: 335725 Bytes = 327 kB = 0 MB
2311 Load Address: 00000000
2312 Entry Point: 0000000c
2313 Verifying Checksum ... OK
2314 Uncompressing Kernel Image ... OK
2315 ## Loading RAMDisk Image at 40200000 ...
2316 Image Name: Simple Ramdisk Image
2317 Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
2318 Data Size: 566530 Bytes = 553 kB = 0 MB
2319 Load Address: 00000000
2320 Entry Point: 00000000
2321 Verifying Checksum ... OK
2322 Loading Ramdisk ... OK
2323 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
2324 Boot arguments: root=/dev/ram
2325 time_init: decrementer frequency = 187500000/60
2326 Calibrating delay loop... 49.77 BogoMIPS
2328 RAMDISK: Compressed image found at block 0
2329 VFS: Mounted root (ext2 filesystem).
2333 Boot Linux and pass a flat device tree:
2336 First, U-Boot must be compiled with the appropriate defines. See the section
2337 titled "Linux Kernel Interface" above for a more in depth explanation. The
2338 following is an example of how to start a kernel and pass an updated
2344 oft=oftrees/mpc8540ads.dtb
2345 => tftp $oftaddr $oft
2346 Speed: 1000, full duplex
2348 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
2349 Filename 'oftrees/mpc8540ads.dtb'.
2350 Load address: 0x300000
2353 Bytes transferred = 4106 (100a hex)
2354 => tftp $loadaddr $bootfile
2355 Speed: 1000, full duplex
2357 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
2359 Load address: 0x200000
2360 Loading:############
2362 Bytes transferred = 1029407 (fb51f hex)
2367 => bootm $loadaddr - $oftaddr
2368 ## Booting image at 00200000 ...
2369 Image Name: Linux-2.6.17-dirty
2370 Image Type: PowerPC Linux Kernel Image (gzip compressed)
2371 Data Size: 1029343 Bytes = 1005.2 kB
2372 Load Address: 00000000
2373 Entry Point: 00000000
2374 Verifying Checksum ... OK
2375 Uncompressing Kernel Image ... OK
2376 Booting using flat device tree at 0x300000
2377 Using MPC85xx ADS machine description
2378 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
2382 More About U-Boot Image Types:
2383 ------------------------------
2385 U-Boot supports the following image types:
2387 "Standalone Programs" are directly runnable in the environment
2388 provided by U-Boot; it is expected that (if they behave
2389 well) you can continue to work in U-Boot after return from
2390 the Standalone Program.
2391 "OS Kernel Images" are usually images of some Embedded OS which
2392 will take over control completely. Usually these programs
2393 will install their own set of exception handlers, device
2394 drivers, set up the MMU, etc. - this means, that you cannot
2395 expect to re-enter U-Boot except by resetting the CPU.
2396 "RAMDisk Images" are more or less just data blocks, and their
2397 parameters (address, size) are passed to an OS kernel that is
2399 "Multi-File Images" contain several images, typically an OS
2400 (Linux) kernel image and one or more data images like
2401 RAMDisks. This construct is useful for instance when you want
2402 to boot over the network using BOOTP etc., where the boot
2403 server provides just a single image file, but you want to get
2404 for instance an OS kernel and a RAMDisk image.
2406 "Multi-File Images" start with a list of image sizes, each
2407 image size (in bytes) specified by an "uint32_t" in network
2408 byte order. This list is terminated by an "(uint32_t)0".
2409 Immediately after the terminating 0 follow the images, one by
2410 one, all aligned on "uint32_t" boundaries (size rounded up to
2411 a multiple of 4 bytes).
2413 "Firmware Images" are binary images containing firmware (like
2414 U-Boot or FPGA images) which usually will be programmed to
2417 "Script files" are command sequences that will be executed by
2418 U-Boot's command interpreter; this feature is especially
2419 useful when you configure U-Boot to use a real shell (hush)
2420 as command interpreter.
2422 Booting the Linux zImage:
2423 -------------------------
2425 On some platforms, it's possible to boot Linux zImage. This is done
2426 using the "bootz" command. The syntax of "bootz" command is the same
2427 as the syntax of "bootm" command.
2429 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
2430 kernel with raw initrd images. The syntax is slightly different, the
2431 address of the initrd must be augmented by it's size, in the following
2432 format: "<initrd addres>:<initrd size>".
2438 One of the features of U-Boot is that you can dynamically load and
2439 run "standalone" applications, which can use some resources of
2440 U-Boot like console I/O functions or interrupt services.
2442 Two simple examples are included with the sources:
2447 'examples/hello_world.c' contains a small "Hello World" Demo
2448 application; it is automatically compiled when you build U-Boot.
2449 It's configured to run at address 0x00040004, so you can play with it
2453 ## Ready for S-Record download ...
2454 ~>examples/hello_world.srec
2455 1 2 3 4 5 6 7 8 9 10 11 ...
2456 [file transfer complete]
2458 ## Start Addr = 0x00040004
2460 => go 40004 Hello World! This is a test.
2461 ## Starting application at 0x00040004 ...
2472 Hit any key to exit ...
2474 ## Application terminated, rc = 0x0
2476 Another example, which demonstrates how to register a CPM interrupt
2477 handler with the U-Boot code, can be found in 'examples/timer.c'.
2478 Here, a CPM timer is set up to generate an interrupt every second.
2479 The interrupt service routine is trivial, just printing a '.'
2480 character, but this is just a demo program. The application can be
2481 controlled by the following keys:
2483 ? - print current values og the CPM Timer registers
2484 b - enable interrupts and start timer
2485 e - stop timer and disable interrupts
2486 q - quit application
2489 ## Ready for S-Record download ...
2490 ~>examples/timer.srec
2491 1 2 3 4 5 6 7 8 9 10 11 ...
2492 [file transfer complete]
2494 ## Start Addr = 0x00040004
2497 ## Starting application at 0x00040004 ...
2500 tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
2503 [q, b, e, ?] Set interval 1000000 us
2506 [q, b, e, ?] ........
2507 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
2510 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
2513 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
2516 tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
2518 [q, b, e, ?] ...Stopping timer
2520 [q, b, e, ?] ## Application terminated, rc = 0x0
2526 Over time, many people have reported problems when trying to use the
2527 "minicom" terminal emulation program for serial download. I (wd)
2528 consider minicom to be broken, and recommend not to use it. Under
2529 Unix, I recommend to use C-Kermit for general purpose use (and
2530 especially for kermit binary protocol download ("loadb" command), and
2531 use "cu" for S-Record download ("loads" command). See
2532 https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
2533 for help with kermit.
2536 Nevertheless, if you absolutely want to use it try adding this
2537 configuration to your "File transfer protocols" section:
2539 Name Program Name U/D FullScr IO-Red. Multi
2540 X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
2541 Y kermit /usr/bin/kermit -i -l %l -r N D Y N N
2547 Starting at version 0.9.2, U-Boot supports NetBSD both as host
2548 (build U-Boot) and target system (boots NetBSD/mpc8xx).
2550 Building requires a cross environment; it is known to work on
2551 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
2552 need gmake since the Makefiles are not compatible with BSD make).
2553 Note that the cross-powerpc package does not install include files;
2554 attempting to build U-Boot will fail because <machine/ansi.h> is
2555 missing. This file has to be installed and patched manually:
2557 # cd /usr/pkg/cross/powerpc-netbsd/include
2559 # ln -s powerpc machine
2560 # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
2561 # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
2563 Native builds *don't* work due to incompatibilities between native
2564 and U-Boot include files.
2566 Booting assumes that (the first part of) the image booted is a
2567 stage-2 loader which in turn loads and then invokes the kernel
2568 proper. Loader sources will eventually appear in the NetBSD source
2569 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
2570 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
2573 Implementation Internals:
2574 =========================
2576 The following is not intended to be a complete description of every
2577 implementation detail. However, it should help to understand the
2578 inner workings of U-Boot and make it easier to port it to custom
2582 Initial Stack, Global Data:
2583 ---------------------------
2585 The implementation of U-Boot is complicated by the fact that U-Boot
2586 starts running out of ROM (flash memory), usually without access to
2587 system RAM (because the memory controller is not initialized yet).
2588 This means that we don't have writable Data or BSS segments, and BSS
2589 is not initialized as zero. To be able to get a C environment working
2590 at all, we have to allocate at least a minimal stack. Implementation
2591 options for this are defined and restricted by the CPU used: Some CPU
2592 models provide on-chip memory (like the IMMR area on MPC8xx and
2593 MPC826x processors), on others (parts of) the data cache can be
2594 locked as (mis-) used as memory, etc.
2596 Chris Hallinan posted a good summary of these issues to the
2597 U-Boot mailing list:
2599 Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
2600 From: "Chris Hallinan" <clh@net1plus.com>
2601 Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
2604 Correct me if I'm wrong, folks, but the way I understand it
2605 is this: Using DCACHE as initial RAM for Stack, etc, does not
2606 require any physical RAM backing up the cache. The cleverness
2607 is that the cache is being used as a temporary supply of
2608 necessary storage before the SDRAM controller is setup. It's
2609 beyond the scope of this list to explain the details, but you
2610 can see how this works by studying the cache architecture and
2611 operation in the architecture and processor-specific manuals.
2613 OCM is On Chip Memory, which I believe the 405GP has 4K. It
2614 is another option for the system designer to use as an
2615 initial stack/RAM area prior to SDRAM being available. Either
2616 option should work for you. Using CS 4 should be fine if your
2617 board designers haven't used it for something that would
2618 cause you grief during the initial boot! It is frequently not
2621 CFG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
2622 with your processor/board/system design. The default value
2623 you will find in any recent u-boot distribution in
2624 walnut.h should work for you. I'd set it to a value larger
2625 than your SDRAM module. If you have a 64MB SDRAM module, set
2626 it above 400_0000. Just make sure your board has no resources
2627 that are supposed to respond to that address! That code in
2628 start.S has been around a while and should work as is when
2629 you get the config right.
2634 It is essential to remember this, since it has some impact on the C
2635 code for the initialization procedures:
2637 * Initialized global data (data segment) is read-only. Do not attempt
2640 * Do not use any uninitialized global data (or implicitly initialized
2641 as zero data - BSS segment) at all - this is undefined, initiali-
2642 zation is performed later (when relocating to RAM).
2644 * Stack space is very limited. Avoid big data buffers or things like
2647 Having only the stack as writable memory limits means we cannot use
2648 normal global data to share information between the code. But it
2649 turned out that the implementation of U-Boot can be greatly
2650 simplified by making a global data structure (gd_t) available to all
2651 functions. We could pass a pointer to this data as argument to _all_
2652 functions, but this would bloat the code. Instead we use a feature of
2653 the GCC compiler (Global Register Variables) to share the data: we
2654 place a pointer (gd) to the global data into a register which we
2655 reserve for this purpose.
2657 When choosing a register for such a purpose we are restricted by the
2658 relevant (E)ABI specifications for the current architecture, and by
2659 GCC's implementation.
2661 For PowerPC, the following registers have specific use:
2663 R2: reserved for system use
2664 R3-R4: parameter passing and return values
2665 R5-R10: parameter passing
2666 R13: small data area pointer
2670 (U-Boot also uses R12 as internal GOT pointer. r12
2671 is a volatile register so r12 needs to be reset when
2672 going back and forth between asm and C)
2674 ==> U-Boot will use R2 to hold a pointer to the global data
2676 Note: on PPC, we could use a static initializer (since the
2677 address of the global data structure is known at compile time),
2678 but it turned out that reserving a register results in somewhat
2679 smaller code - although the code savings are not that big (on
2680 average for all boards 752 bytes for the whole U-Boot image,
2681 624 text + 127 data).
2683 On ARM, the following registers are used:
2685 R0: function argument word/integer result
2686 R1-R3: function argument word
2687 R9: platform specific
2688 R10: stack limit (used only if stack checking is enabled)
2689 R11: argument (frame) pointer
2690 R12: temporary workspace
2693 R15: program counter
2695 ==> U-Boot will use R9 to hold a pointer to the global data
2697 Note: on ARM, only R_ARM_RELATIVE relocations are supported.
2699 On Nios II, the ABI is documented here:
2700 https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
2702 ==> U-Boot will use gp to hold a pointer to the global data
2704 Note: on Nios II, we give "-G0" option to gcc and don't use gp
2705 to access small data sections, so gp is free.
2707 On RISC-V, the following registers are used:
2709 x0: hard-wired zero (zero)
2710 x1: return address (ra)
2711 x2: stack pointer (sp)
2712 x3: global pointer (gp)
2713 x4: thread pointer (tp)
2714 x5: link register (t0)
2715 x8: frame pointer (fp)
2716 x10-x11: arguments/return values (a0-1)
2717 x12-x17: arguments (a2-7)
2718 x28-31: temporaries (t3-6)
2719 pc: program counter (pc)
2721 ==> U-Boot will use gp to hold a pointer to the global data
2726 U-Boot runs in system state and uses physical addresses, i.e. the
2727 MMU is not used either for address mapping nor for memory protection.
2729 The available memory is mapped to fixed addresses using the memory
2730 controller. In this process, a contiguous block is formed for each
2731 memory type (Flash, SDRAM, SRAM), even when it consists of several
2732 physical memory banks.
2734 U-Boot is installed in the first 128 kB of the first Flash bank (on
2735 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
2736 booting and sizing and initializing DRAM, the code relocates itself
2737 to the upper end of DRAM. Immediately below the U-Boot code some
2738 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
2739 configuration setting]. Below that, a structure with global Board
2740 Info data is placed, followed by the stack (growing downward).
2742 Additionally, some exception handler code is copied to the low 8 kB
2743 of DRAM (0x00000000 ... 0x00001FFF).
2745 So a typical memory configuration with 16 MB of DRAM could look like
2748 0x0000 0000 Exception Vector code
2751 0x0000 2000 Free for Application Use
2757 0x00FB FF20 Monitor Stack (Growing downward)
2758 0x00FB FFAC Board Info Data and permanent copy of global data
2759 0x00FC 0000 Malloc Arena
2762 0x00FE 0000 RAM Copy of Monitor Code
2763 ... eventually: LCD or video framebuffer
2764 ... eventually: pRAM (Protected RAM - unchanged by reset)
2765 0x00FF FFFF [End of RAM]
2768 System Initialization:
2769 ----------------------
2771 In the reset configuration, U-Boot starts at the reset entry point
2772 (on most PowerPC systems at address 0x00000100). Because of the reset
2773 configuration for CS0# this is a mirror of the on board Flash memory.
2774 To be able to re-map memory U-Boot then jumps to its link address.
2775 To be able to implement the initialization code in C, a (small!)
2776 initial stack is set up in the internal Dual Ported RAM (in case CPUs
2777 which provide such a feature like), or in a locked part of the data
2778 cache. After that, U-Boot initializes the CPU core, the caches and
2781 Next, all (potentially) available memory banks are mapped using a
2782 preliminary mapping. For example, we put them on 512 MB boundaries
2783 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
2784 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
2785 programmed for SDRAM access. Using the temporary configuration, a
2786 simple memory test is run that determines the size of the SDRAM
2789 When there is more than one SDRAM bank, and the banks are of
2790 different size, the largest is mapped first. For equal size, the first
2791 bank (CS2#) is mapped first. The first mapping is always for address
2792 0x00000000, with any additional banks following immediately to create
2793 contiguous memory starting from 0.
2795 Then, the monitor installs itself at the upper end of the SDRAM area
2796 and allocates memory for use by malloc() and for the global Board
2797 Info data; also, the exception vector code is copied to the low RAM
2798 pages, and the final stack is set up.
2800 Only after this relocation will you have a "normal" C environment;
2801 until that you are restricted in several ways, mostly because you are
2802 running from ROM, and because the code will have to be relocated to a
2806 U-Boot Porting Guide:
2807 ----------------------
2809 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
2813 int main(int argc, char *argv[])
2815 sighandler_t no_more_time;
2817 signal(SIGALRM, no_more_time);
2818 alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
2820 if (available_money > available_manpower) {
2821 Pay consultant to port U-Boot;
2825 Download latest U-Boot source;
2827 Subscribe to u-boot mailing list;
2830 email("Hi, I am new to U-Boot, how do I get started?");
2833 Read the README file in the top level directory;
2834 Read https://www.denx.de/wiki/bin/view/DULG/Manual;
2835 Read applicable doc/README.*;
2836 Read the source, Luke;
2837 /* find . -name "*.[chS]" | xargs grep -i <keyword> */
2840 if (available_money > toLocalCurrency ($2500))
2843 Add a lot of aggravation and time;
2845 if (a similar board exists) { /* hopefully... */
2846 cp -a board/<similar> board/<myboard>
2847 cp include/configs/<similar>.h include/configs/<myboard>.h
2849 Create your own board support subdirectory;
2850 Create your own board include/configs/<myboard>.h file;
2852 Edit new board/<myboard> files
2853 Edit new include/configs/<myboard>.h
2858 Add / modify source code;
2862 email("Hi, I am having problems...");
2864 Send patch file to the U-Boot email list;
2865 if (reasonable critiques)
2866 Incorporate improvements from email list code review;
2868 Defend code as written;
2874 void no_more_time (int sig)
2883 All contributions to U-Boot should conform to the Linux kernel
2884 coding style; see the kernel coding style guide at
2885 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
2886 script "scripts/Lindent" in your Linux kernel source directory.
2888 Source files originating from a different project (for example the
2889 MTD subsystem) are generally exempt from these guidelines and are not
2890 reformatted to ease subsequent migration to newer versions of those
2893 Please note that U-Boot is implemented in C (and to some small parts in
2894 Assembler); no C++ is used, so please do not use C++ style comments (//)
2897 Please also stick to the following formatting rules:
2898 - remove any trailing white space
2899 - use TAB characters for indentation and vertical alignment, not spaces
2900 - make sure NOT to use DOS '\r\n' line feeds
2901 - do not add more than 2 consecutive empty lines to source files
2902 - do not add trailing empty lines to source files
2904 Submissions which do not conform to the standards may be returned
2905 with a request to reformat the changes.
2911 Since the number of patches for U-Boot is growing, we need to
2912 establish some rules. Submissions which do not conform to these rules
2913 may be rejected, even when they contain important and valuable stuff.
2915 Please see https://www.denx.de/wiki/U-Boot/Patches for details.
2917 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
2918 see https://lists.denx.de/listinfo/u-boot
2920 When you send a patch, please include the following information with
2923 * For bug fixes: a description of the bug and how your patch fixes
2924 this bug. Please try to include a way of demonstrating that the
2925 patch actually fixes something.
2927 * For new features: a description of the feature and your
2930 * For major contributions, add a MAINTAINERS file with your
2931 information and associated file and directory references.
2933 * When you add support for a new board, don't forget to add a
2934 maintainer e-mail address to the boards.cfg file, too.
2936 * If your patch adds new configuration options, don't forget to
2937 document these in the README file.
2939 * The patch itself. If you are using git (which is *strongly*
2940 recommended) you can easily generate the patch using the
2941 "git format-patch". If you then use "git send-email" to send it to
2942 the U-Boot mailing list, you will avoid most of the common problems
2943 with some other mail clients.
2945 If you cannot use git, use "diff -purN OLD NEW". If your version of
2946 diff does not support these options, then get the latest version of
2949 The current directory when running this command shall be the parent
2950 directory of the U-Boot source tree (i. e. please make sure that
2951 your patch includes sufficient directory information for the
2954 We prefer patches as plain text. MIME attachments are discouraged,
2955 and compressed attachments must not be used.
2957 * If one logical set of modifications affects or creates several
2958 files, all these changes shall be submitted in a SINGLE patch file.
2960 * Changesets that contain different, unrelated modifications shall be
2961 submitted as SEPARATE patches, one patch per changeset.
2966 * Before sending the patch, run the buildman script on your patched
2967 source tree and make sure that no errors or warnings are reported
2968 for any of the boards.
2970 * Keep your modifications to the necessary minimum: A patch
2971 containing several unrelated changes or arbitrary reformats will be
2972 returned with a request to re-formatting / split it.
2974 * If you modify existing code, make sure that your new code does not
2975 add to the memory footprint of the code ;-) Small is beautiful!
2976 When adding new features, these should compile conditionally only
2977 (using #ifdef), and the resulting code with the new feature
2978 disabled must not need more memory than the old code without your
2981 * Remember that there is a size limit of 100 kB per message on the
2982 u-boot mailing list. Bigger patches will be moderated. If they are
2983 reasonable and not too big, they will be acknowledged. But patches
2984 bigger than the size limit should be avoided.