1 # SPDX-License-Identifier: GPL-2.0+
3 # Copyright (C) 2014, Simon Glass <sjg@chromium.org>
4 # Copyright (C) 2014, Bin Meng <bmeng.cn@gmail.com>
9 This document describes the information about U-Boot running on x86 targets,
10 including supported boards, build instructions, todo list, etc.
14 U-Boot supports running as a coreboot [1] payload on x86. So far only Link
15 (Chromebook Pixel) and QEMU [2] x86 targets have been tested, but it should
16 work with minimal adjustments on other x86 boards since coreboot deals with
17 most of the low-level details.
19 U-Boot is a main bootloader on Intel Edison board.
21 U-Boot also supports booting directly from x86 reset vector, without coreboot.
22 In this case, known as bare mode, from the fact that it runs on the
23 'bare metal', U-Boot acts like a BIOS replacement. The following platforms
28 - Congatec QEVAL 2.0 & conga-QA3/E3845
32 - Link (Chromebook Pixel)
34 - Samus (Chromebook Pixel 2015)
35 - QEMU x86 (32-bit & 64-bit)
37 As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit
38 Linux kernel as part of a FIT image. It also supports a compressed zImage.
39 U-Boot supports loading an x86 VxWorks kernel. Please check README.vxworks
42 Build Instructions for U-Boot as coreboot payload
43 -------------------------------------------------
44 Building U-Boot as a coreboot payload is just like building U-Boot for targets
45 on other architectures, like below:
47 $ make coreboot_defconfig
50 Build Instructions for U-Boot as BIOS replacement (bare mode)
51 -------------------------------------------------------------
52 Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a
53 little bit tricky, as generally it requires several binary blobs which are not
54 shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build is
55 not turned on by default in the U-Boot source tree. Firstly, you need turn it
56 on by enabling the ROM build either via an environment variable
64 Both tell the Makefile to build u-boot.rom as a target.
68 Chromebook Link specific instructions for bare mode:
70 First, you need the following binary blobs:
72 * descriptor.bin - Intel flash descriptor
73 * me.bin - Intel Management Engine
74 * mrc.bin - Memory Reference Code, which sets up SDRAM
75 * video ROM - sets up the display
77 You can get these binary blobs by:
79 $ git clone http://review.coreboot.org/p/blobs.git
82 Find the following files:
84 * ./mainboard/google/link/descriptor.bin
85 * ./mainboard/google/link/me.bin
86 * ./northbridge/intel/sandybridge/systemagent-r6.bin
88 The 3rd one should be renamed to mrc.bin.
89 As for the video ROM, you can get it here [3] and rename it to vga.bin.
90 Make sure all these binary blobs are put in the board directory.
92 Now you can build U-Boot and obtain u-boot.rom:
94 $ make chromebook_link_defconfig
99 Chromebook Samus (2015 Pixel) instructions for bare mode:
101 First, you need the following binary blobs:
103 * descriptor.bin - Intel flash descriptor
104 * me.bin - Intel Management Engine
105 * mrc.bin - Memory Reference Code, which sets up SDRAM
106 * refcode.elf - Additional Reference code
107 * vga.bin - video ROM, which sets up the display
109 If you have a samus you can obtain them from your flash, for example, in
110 developer mode on the Chromebook (use Ctrl-Alt-F2 to obtain a terminal and
114 flashrom -w samus.bin
115 scp samus.bin username@ip_address:/path/to/somewhere
117 If not see the coreboot tree [4] where you can use:
119 bash crosfirmware.sh samus
121 to get the image. There is also an 'extract_blobs.sh' scripts that you can use
122 on the 'coreboot-Google_Samus.*' file to short-circuit some of the below.
124 Then 'ifdtool -x samus.bin' on your development machine will produce:
126 flashregion_0_flashdescriptor.bin
127 flashregion_1_bios.bin
128 flashregion_2_intel_me.bin
130 Rename flashregion_0_flashdescriptor.bin to descriptor.bin
131 Rename flashregion_2_intel_me.bin to me.bin
132 You can ignore flashregion_1_bios.bin - it is not used.
134 To get the rest, use 'cbfstool samus.bin print':
136 samus.bin: 8192 kB, bootblocksize 2864, romsize 8388608, offset 0x700000
137 alignment: 64 bytes, architecture: x86
139 Name Offset Type Size
140 cmos_layout.bin 0x700000 cmos_layout 1164
141 pci8086,0406.rom 0x7004c0 optionrom 65536
142 spd.bin 0x710500 (unknown) 4096
143 cpu_microcode_blob.bin 0x711540 microcode 70720
144 fallback/romstage 0x722a00 stage 54210
145 fallback/ramstage 0x72fe00 stage 96382
146 config 0x7476c0 raw 6075
147 fallback/vboot 0x748ec0 stage 15980
148 fallback/refcode 0x74cd80 stage 75578
149 fallback/payload 0x75f500 payload 62878
150 u-boot.dtb 0x76eb00 (unknown) 5318
151 (empty) 0x770000 null 196504
152 mrc.bin 0x79ffc0 (unknown) 222876
153 (empty) 0x7d66c0 null 167320
155 You can extract what you need:
157 cbfstool samus.bin extract -n pci8086,0406.rom -f vga.bin
158 cbfstool samus.bin extract -n fallback/refcode -f refcode.rmod
159 cbfstool samus.bin extract -n mrc.bin -f mrc.bin
160 cbfstool samus.bin extract -n fallback/refcode -f refcode.bin -U
162 Note that the -U flag is only supported by the latest cbfstool. It unpacks
163 and decompresses the stage to produce a coreboot rmodule. This is a simple
164 representation of an ELF file. You need the patch "Support decoding a stage
167 Put all 5 files into board/google/chromebook_samus.
169 Now you can build U-Boot and obtain u-boot.rom:
171 $ make chromebook_link_defconfig
174 If you are using em100, then this command will flash write -Boot:
176 em100 -s -d filename.rom -c W25Q64CV -r
178 Flash map for samus / broadwell:
180 fffff800 SYS_X86_START16
181 ffff0000 RESET_SEG_START
182 fffd8000 TPL_TEXT_BASE
183 fffa0000 X86_MRC_ADDR
184 fff90000 VGA_BIOS_ADDR
185 ffed0000 SYS_TEXT_BASE
186 ffea0000 X86_REFCODE_ADDR
187 ffe70000 SPL_TEXT_BASE
188 ffbf8000 CONFIG_ENV_OFFSET (environemnt offset)
189 ffbe0000 rw-mrc-cache (Memory-reference-code cache)
191 ff801000 intel-me (address set by descriptor.bin)
192 ff800000 intel-descriptor
196 Intel Galileo instructions for bare mode:
198 Only one binary blob is needed for Remote Management Unit (RMU) within Intel
199 Quark SoC. Not like FSP, U-Boot does not call into the binary. The binary is
200 needed by the Quark SoC itself.
202 You can get the binary blob from Quark Board Support Package from Intel website:
204 * ./QuarkSocPkg/QuarkNorthCluster/Binary/QuarkMicrocode/RMU.bin
206 Rename the file and put it to the board directory by:
208 $ cp RMU.bin board/intel/galileo/rmu.bin
210 Now you can build U-Boot and obtain u-boot.rom
212 $ make galileo_defconfig
217 QEMU x86 target instructions for bare mode:
219 To build u-boot.rom for QEMU x86 targets, just simply run
221 $ make qemu-x86_defconfig (for 32-bit)
223 $ make qemu-x86_64_defconfig (for 64-bit)
226 Note this default configuration will build a U-Boot for the QEMU x86 i440FX
227 board. To build a U-Boot against QEMU x86 Q35 board, you can change the build
228 configuration during the 'make menuconfig' process like below:
230 Device Tree Control --->
232 (qemu-x86_q35) Default Device Tree for DT control
236 For testing U-Boot as the coreboot payload, there are things that need be paid
237 attention to. coreboot supports loading an ELF executable and a 32-bit plain
238 binary, as well as other supported payloads. With the default configuration,
239 U-Boot is set up to use a separate Device Tree Blob (dtb). As of today, the
240 generated u-boot-dtb.bin needs to be packaged by the cbfstool utility (a tool
241 provided by coreboot) manually as coreboot's 'make menuconfig' does not provide
242 this capability yet. The command is as follows:
244 # in the coreboot root directory
245 $ ./build/util/cbfstool/cbfstool build/coreboot.rom add-flat-binary \
246 -f u-boot-dtb.bin -n fallback/payload -c lzma -l 0x1110000 -e 0x1110000
248 Make sure 0x1110000 matches CONFIG_SYS_TEXT_BASE, which is the symbol address
249 of _x86boot_start (in arch/x86/cpu/start.S).
251 If you want to use ELF as the coreboot payload, change U-Boot configuration to
252 use CONFIG_OF_EMBED instead of CONFIG_OF_SEPARATE.
254 To enable video you must enable these options in coreboot:
256 - Set framebuffer graphics resolution (1280x1024 32k-color (1:5:5))
257 - Keep VESA framebuffer
259 At present it seems that for Minnowboard Max, coreboot does not pass through
260 the video information correctly (it always says the resolution is 0x0). This
261 works correctly for link though.
263 Test with QEMU for bare mode
264 ----------------------------
265 QEMU is a fancy emulator that can enable us to test U-Boot without access to
266 a real x86 board. Please make sure your QEMU version is 2.3.0 or above test
267 U-Boot. To launch QEMU with u-boot.rom, call QEMU as follows:
269 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom
271 This will instantiate an emulated x86 board with i440FX and PIIX chipset. QEMU
272 also supports emulating an x86 board with Q35 and ICH9 based chipset, which is
273 also supported by U-Boot. To instantiate such a machine, call QEMU with:
275 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -M q35
277 Note by default QEMU instantiated boards only have 128 MiB system memory. But
278 it is enough to have U-Boot boot and function correctly. You can increase the
279 system memory by pass '-m' parameter to QEMU if you want more memory:
281 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024
283 This creates a board with 1 GiB system memory. Currently U-Boot for QEMU only
284 supports 3 GiB maximum system memory and reserves the last 1 GiB address space
285 for PCI device memory-mapped I/O and other stuff, so the maximum value of '-m'
288 QEMU emulates a graphic card which U-Boot supports. Removing '-nographic' will
289 show QEMU's VGA console window. Note this will disable QEMU's serial output.
290 If you want to check both consoles, use '-serial stdio'.
292 Multicore is also supported by QEMU via '-smp n' where n is the number of cores
293 to instantiate. Note, the maximum supported CPU number in QEMU is 255.
295 The fw_cfg interface in QEMU also provides information about kernel data,
296 initrd, command-line arguments and more. U-Boot supports directly accessing
297 these informtion from fw_cfg interface, which saves the time of loading them
298 from hard disk or network again, through emulated devices. To use it , simply
299 providing them in QEMU command line:
301 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024 -kernel /path/to/bzImage
302 -append 'root=/dev/ram console=ttyS0' -initrd /path/to/initrd -smp 8
304 Note: -initrd and -smp are both optional
306 Then start QEMU, in U-Boot command line use the following U-Boot command to
310 qfw - QEMU firmware interface
314 - list : print firmware(s) currently loaded
315 - cpus : print online cpu number
316 - load <kernel addr> <initrd addr> : load kernel and initrd (if any) and setup for zboot
319 loading kernel to address 01000000 size 5d9d30 initrd 04000000 size 1b1ab50
321 Here the kernel (bzImage) is loaded to 01000000 and initrd is to 04000000. Then,
322 'zboot' can be used to boot the kernel:
324 => zboot 01000000 - 04000000 1b1ab50
326 To run 64-bit U-Boot, qemu-system-x86_64 should be used instead, e.g.:
327 $ qemu-system-x86_64 -nographic -bios path/to/u-boot.rom
329 A specific CPU can be specified via the '-cpu' parameter but please make
330 sure the specified CPU supports 64-bit like '-cpu core2duo'. Conversely
331 '-cpu pentium' won't work for obvious reasons that the processor only
334 Note 64-bit support is very preliminary at this point. Lots of features
335 are missing in the 64-bit world. One notable feature is the VGA console
336 support which is currently missing, so that you must specify '-nographic'
337 to get 64-bit U-Boot up and running.
341 Modern CPUs usually require a special bit stream called microcode [8] to be
342 loaded on the processor after power up in order to function properly. U-Boot
343 has already integrated these as hex dumps in the source tree.
347 On a multicore system, U-Boot is executed on the bootstrap processor (BSP).
348 Additional application processors (AP) can be brought up by U-Boot. In order to
349 have an SMP kernel to discover all of the available processors, U-Boot needs to
350 prepare configuration tables which contain the multi-CPUs information before
351 loading the OS kernel. Currently U-Boot supports generating two types of tables
352 for SMP, called Simple Firmware Interface (SFI) [9] and Multi-Processor (MP)
353 [10] tables. The writing of these two tables are controlled by two Kconfig
354 options GENERATE_SFI_TABLE and GENERATE_MP_TABLE.
358 x86 has been converted to use driver model for serial, GPIO, SPI, SPI flash,
359 keyboard, real-time clock, USB. Video is in progress.
363 x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to
364 be turned on. Not every device on the board is configured via device tree, but
365 more and more devices will be added as time goes by. Check out the directory
366 arch/x86/dts/ for these device tree source files.
370 In keeping with the U-Boot philosophy of providing functions to check and
371 adjust internal settings, there are several x86-specific commands that may be
374 fsp - Display information about Intel Firmware Support Package (FSP).
375 This is only available on platforms which use FSP, mostly Atom.
376 iod - Display I/O memory
377 iow - Write I/O memory
378 mtrr - List and set the Memory Type Range Registers (MTRR). These are used to
379 tell the CPU whether memory is cacheable and if so the cache write
380 mode to use. U-Boot sets up some reasonable values but you can
381 adjust then with this command.
385 As an example of how to set up your boot flow with U-Boot, here are
386 instructions for starting Ubuntu from U-Boot. These instructions have been
387 tested on Minnowboard MAX with a SATA drive but are equally applicable on
388 other platforms and other media. There are really only four steps and it's a
389 very simple script, but a more detailed explanation is provided here for
392 Note: It is possible to set up U-Boot to boot automatically using syslinux.
393 It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the
394 GUID. If you figure these out, please post patches to this README.
396 Firstly, you will need Ubuntu installed on an available disk. It should be
397 possible to make U-Boot start a USB start-up disk but for now let's assume
398 that you used another boot loader to install Ubuntu.
400 Use the U-Boot command line to find the UUID of the partition you want to
401 boot. For example our disk is SCSI device 0:
405 Partition Map for SCSI device 0 -- Partition Type: EFI
407 Part Start LBA End LBA Name
411 1 0x00000800 0x001007ff ""
412 attrs: 0x0000000000000000
413 type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b
414 guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c
415 2 0x00100800 0x037d8fff ""
416 attrs: 0x0000000000000000
417 type: 0fc63daf-8483-4772-8e79-3d69d8477de4
418 guid: 965c59ee-1822-4326-90d2-b02446050059
419 3 0x037d9000 0x03ba27ff ""
420 attrs: 0x0000000000000000
421 type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f
422 guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17
425 This shows that your SCSI disk has three partitions. The really long hex
426 strings are called Globally Unique Identifiers (GUIDs). You can look up the
427 'type' ones here [11]. On this disk the first partition is for EFI and is in
428 VFAT format (DOS/Windows):
436 Partition 2 is 'Linux filesystem data' so that will be our root disk. It is
442 <DIR> 16384 lost+found
465 <SYM> 33 initrd.img.old
468 and if you look in the /boot directory you will see the kernel:
470 => ext2ls scsi 0:2 /boot
475 3381262 System.map-3.13.0-32-generic
476 1162712 abi-3.13.0-32-generic
477 165611 config-3.13.0-32-generic
478 176500 memtest86+.bin
479 178176 memtest86+.elf
480 178680 memtest86+_multiboot.bin
481 5798112 vmlinuz-3.13.0-32-generic
482 165762 config-3.13.0-58-generic
483 1165129 abi-3.13.0-58-generic
484 5823136 vmlinuz-3.13.0-58-generic
485 19215259 initrd.img-3.13.0-58-generic
486 3391763 System.map-3.13.0-58-generic
487 5825048 vmlinuz-3.13.0-58-generic.efi.signed
488 28304443 initrd.img-3.13.0-32-generic
491 The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of
492 self-extracting compressed file mixed with some 'setup' configuration data.
493 Despite its size (uncompressed it is >10MB) this only includes a basic set of
494 device drivers, enough to boot on most hardware types.
496 The 'initrd' files contain a RAM disk. This is something that can be loaded
497 into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots
498 of drivers for whatever hardware you might have. It is loaded before the
499 real root disk is accessed.
501 The numbers after the end of each file are the version. Here it is Linux
502 version 3.13. You can find the source code for this in the Linux tree with
503 the tag v3.13. The '.0' allows for additional Linux releases to fix problems,
504 but normally this is not needed. The '-58' is used by Ubuntu. Each time they
505 release a new kernel they increment this number. New Ubuntu versions might
506 include kernel patches to fix reported bugs. Stable kernels can exist for
507 some years so this number can get quite high.
509 The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own
510 secure boot mechanism - see [12] [13] and cannot read .efi files at present.
512 To boot Ubuntu from U-Boot the steps are as follows:
514 1. Set up the boot arguments. Use the GUID for the partition you want to
517 => setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro
519 Here root= tells Linux the location of its root disk. The disk is specified
520 by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory'
521 containing all the GUIDs Linux has found. When it starts up, there will be a
522 file in that directory with this name in it. It is also possible to use a
523 device name here, see later.
525 2. Load the kernel. Since it is an ext2/4 filesystem we can do:
527 => ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic
529 The address 30000000 is arbitrary, but there seem to be problems with using
530 small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into
531 the start of RAM (which is at 0 on x86).
533 3. Load the ramdisk (to 64MB):
535 => ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic
537 4. Start up the kernel. We need to know the size of the ramdisk, but can use
538 a variable for that. U-Boot sets 'filesize' to the size of the last file it
541 => zboot 03000000 0 04000000 ${filesize}
543 Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is
544 quite verbose when it boots a kernel. You should see these messages from
548 Setup Size = 0x00004400
549 Magic signature found
550 Using boot protocol version 2.0c
551 Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015
552 Building boot_params at 0x00090000
553 Loading bzImage at address 100000 (5805728 bytes)
554 Magic signature found
555 Initial RAM disk at linear address 0x04000000, size 19215259 bytes
556 Kernel command line: "root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro"
560 U-Boot prints out some bootstage timing. This is more useful if you put the
561 above commands into a script since then it will be faster.
563 Timer summary in microseconds:
566 241,535 241,535 board_init_r
567 2,421,611 2,180,076 id=64
569 2,428,215 6,425 main_loop
570 48,860,584 46,432,369 start_kernel
574 1,422,704 vesa display
576 Now the kernel actually starts: (if you want to examine kernel boot up message
577 on the serial console, append "console=ttyS0,115200" to the kernel command line)
579 [ 0.000000] Initializing cgroup subsys cpuset
580 [ 0.000000] Initializing cgroup subsys cpu
581 [ 0.000000] Initializing cgroup subsys cpuacct
582 [ 0.000000] Linux version 3.13.0-58-generic (buildd@allspice) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) ) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015 (Ubuntu 3.13.0-58.97-generic 3.13.11-ckt22)
583 [ 0.000000] Command line: root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro console=ttyS0,115200
585 It continues for a long time. Along the way you will see it pick up your
588 [ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff]
590 [ 0.788540] Trying to unpack rootfs image as initramfs...
591 [ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000)
594 Later it actually starts using it:
596 Begin: Running /scripts/local-premount ... done.
598 You should also see your boot disk turn up:
600 [ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5
601 [ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB)
602 [ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0
603 [ 4.381859] sd 1:0:0:0: [sda] Write Protect is off
604 [ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
605 [ 4.399535] sda: sda1 sda2 sda3
607 Linux has found the three partitions (sda1-3). Mercifully it doesn't print out
608 the GUIDs. In step 1 above we could have used:
610 setenv bootargs root=/dev/sda2 ro
612 instead of the GUID. However if you add another drive to your board the
613 numbering may change whereas the GUIDs will not. So if your boot partition
614 becomes sdb2, it will still boot. For embedded systems where you just want to
615 boot the first disk, you have that option.
617 The last thing you will see on the console is mention of plymouth (which
618 displays the Ubuntu start-up screen) and a lot of 'Starting' messages:
620 * Starting Mount filesystems on boot [ OK ]
622 After a pause you should see a login screen on your display and you are done.
624 If you want to put this in a script you can use something like this:
626 setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro
627 setenv boot zboot 03000000 0 04000000 \${filesize}
628 setenv bootcmd "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; run boot"
631 The \ is to tell the shell not to evaluate ${filesize} as part of the setenv
634 You can also bake this behaviour into your build by hard-coding the
635 environment variables if you add this to minnowmax.h:
637 #undef CONFIG_BOOTCOMMAND
638 #define CONFIG_BOOTCOMMAND \
639 "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \
640 "ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \
643 #undef CONFIG_EXTRA_ENV_SETTINGS
644 #define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}"
646 and change CONFIG_BOOTARGS value in configs/minnowmax_defconfig to:
648 CONFIG_BOOTARGS="root=/dev/sda2 ro"
652 SeaBIOS [14] is an open source implementation of a 16-bit x86 BIOS. It can run
653 in an emulator or natively on x86 hardware with the use of U-Boot. With its
654 help, we can boot some OSes that require 16-bit BIOS services like Windows/DOS.
656 As U-Boot, we have to manually create a table where SeaBIOS gets various system
657 information (eg: E820) from. The table unfortunately has to follow the coreboot
658 table format as SeaBIOS currently supports booting as a coreboot payload.
660 To support loading SeaBIOS, U-Boot should be built with CONFIG_SEABIOS on.
661 Booting SeaBIOS is done via U-Boot's bootelf command, like below:
663 => tftp bios.bin.elf;bootelf
665 TFTP from server 10.10.0.100; our IP address is 10.10.0.108
667 Bytes transferred = 122124 (1dd0c hex)
668 ## Starting application at 0x000ff06e ...
669 SeaBIOS (version rel-1.9.0)
672 bios.bin.elf is the SeaBIOS image built from SeaBIOS source tree.
673 Make sure it is built as follows:
677 Inside the "General Features" menu, select "Build for coreboot" as the
678 "Build Target". Inside the "Debugging" menu, turn on "Serial port debugging"
679 so that we can see something as soon as SeaBIOS boots. Leave other options
680 as in their default state. Then,
684 Total size: 121888 Fixed: 66496 Free: 9184 (used 93.0% of 128KiB rom)
685 Creating out/bios.bin.elf
687 Currently this is tested on QEMU x86 target with U-Boot chain-loading SeaBIOS
688 to install/boot a Windows XP OS (below for example command to install Windows).
690 # Create a 10G disk.img as the virtual hard disk
691 $ qemu-img create -f qcow2 disk.img 10G
693 # Install a Windows XP OS from an ISO image 'winxp.iso'
694 $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -cdrom winxp.iso -smp 2 -m 512
696 # Boot a Windows XP OS installed on the virutal hard disk
697 $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -smp 2 -m 512
699 This is also tested on Intel Crown Bay board with a PCIe graphics card, booting
700 SeaBIOS then chain-loading a GRUB on a USB drive, then Linux kernel finally.
702 If you are using Intel Integrated Graphics Device (IGD) as the primary display
703 device on your board, SeaBIOS needs to be patched manually to get its VGA ROM
704 loaded and run by SeaBIOS. SeaBIOS locates VGA ROM via the PCI expansion ROM
705 register, but IGD device does not have its VGA ROM mapped by this register.
706 Its VGA ROM is packaged as part of u-boot.rom at a configurable flash address
707 which is unknown to SeaBIOS. An example patch is needed for SeaBIOS below:
709 diff --git a/src/optionroms.c b/src/optionroms.c
710 index 65f7fe0..c7b6f5e 100644
711 --- a/src/optionroms.c
712 +++ b/src/optionroms.c
713 @@ -324,6 +324,8 @@ init_pcirom(struct pci_device *pci, int isvga, u64 *sources)
714 rom = deploy_romfile(file);
715 else if (RunPCIroms > 1 || (RunPCIroms == 1 && isvga))
716 rom = map_pcirom(pci);
717 + if (pci->bdf == pci_to_bdf(0, 2, 0))
718 + rom = (struct rom_header *)0xfff90000;
723 Note: the patch above expects IGD device is at PCI b.d.f 0.2.0 and its VGA ROM
724 is at 0xfff90000 which corresponds to CONFIG_VGA_BIOS_ADDR on Minnowboard MAX.
725 Change these two accordingly if this is not the case on your board.
729 These notes are for those who want to port U-Boot to a new x86 platform.
731 Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment.
732 The Dediprog em100 can be used on Linux. The em100 tool is available here:
734 http://review.coreboot.org/p/em100.git
736 On Minnowboard Max the following command line can be used:
738 sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r
740 A suitable clip for connecting over the SPI flash chip is here:
742 http://www.dediprog.com/pd/programmer-accessories/EM-TC-8
744 This allows you to override the SPI flash contents for development purposes.
745 Typically you can write to the em100 in around 1200ms, considerably faster
746 than programming the real flash device each time. The only important
747 limitation of the em100 is that it only supports SPI bus speeds up to 20MHz.
748 This means that images must be set to boot with that speed. This is an
749 Intel-specific feature - e.g. tools/ifttool has an option to set the SPI
750 speed in the SPI descriptor region.
752 If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly
753 easy to fit it in. You can follow the Minnowboard Max implementation, for
754 example. Hopefully you will just need to create new files similar to those
755 in arch/x86/cpu/baytrail which provide Bay Trail support.
757 If you are not using an FSP you have more freedom and more responsibility.
758 The ivybridge support works this way, although it still uses a ROM for
759 graphics and still has binary blobs containing Intel code. You should aim to
760 support all important peripherals on your platform including video and storage.
761 Use the device tree for configuration where possible.
763 For the microcode you can create a suitable device tree file using the
766 ./tools/microcode-tool -d microcode.dat -m <model> create
768 or if you only have header files and not the full Intel microcode.dat database:
770 ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \
771 -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h \
774 These are written to arch/x86/dts/microcode/ by default.
776 Note that it is possible to just add the micrcode for your CPU if you know its
777 model. U-Boot prints this information when it starts
779 CPU: x86_64, vendor Intel, device 30673h
781 so here we can use the M0130673322 file.
783 If you platform can display POST codes on two little 7-segment displays on
784 the board, then you can use post_code() calls from C or assembler to monitor
785 boot progress. This can be good for debugging.
787 If not, you can try to get serial working as early as possible. The early
788 debug serial port may be useful here. See setup_internal_uart() for an example.
790 During the U-Boot porting, one of the important steps is to write correct PIRQ
791 routing information in the board device tree. Without it, device drivers in the
792 Linux kernel won't function correctly due to interrupt is not working. Please
793 refer to U-Boot doc [15] for the device tree bindings of Intel interrupt router.
794 Here we have more details on the intel,pirq-routing property below.
796 intel,pirq-routing = <
797 PCI_BDF(0, 2, 0) INTA PIRQA
801 As you see each entry has 3 cells. For the first one, we need describe all pci
802 devices mounted on the board. For SoC devices, normally there is a chapter on
803 the chipset datasheet which lists all the available PCI devices. For example on
804 Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we
805 can get the interrupt pin either from datasheet or hardware via U-Boot shell.
806 The reliable source is the hardware as sometimes chipset datasheet is not 100%
807 up-to-date. Type 'pci header' plus the device's pci bus/device/function number
808 from U-Boot shell below.
814 interrupt line = 0x09
818 It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin
819 register. Repeat this until you get interrupt pins for all the devices. The last
820 cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel
821 chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This
822 can be changed by registers in LPC bridge. So far Intel FSP does not touch those
823 registers so we can write down the PIRQ according to the default mapping rule.
825 Once we get the PIRQ routing information in the device tree, the interrupt
826 allocation and assignment will be done by U-Boot automatically. Now you can
827 enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and
828 CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC.
830 This script might be useful. If you feed it the output of 'pci long' from
831 U-Boot then it will generate a device tree fragment with the interrupt
832 configuration for each device (note it needs gawk 4.0.0):
834 $ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \
835 /interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \
836 {patsplit(device, bdf, "[0-9a-f]+"); \
837 printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \
838 strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}'
841 PCI_BDF(0, 2, 0) INTA PIRQA
842 PCI_BDF(0, 3, 0) INTA PIRQA
848 Quark-specific considerations:
850 To port U-Boot to other boards based on the Intel Quark SoC, a few things need
851 to be taken care of. The first important part is the Memory Reference Code (MRC)
852 parameters. Quark MRC supports memory-down configuration only. All these MRC
853 parameters are supplied via the board device tree. To get started, first copy
854 the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then
855 change these values by consulting board manuals or your hardware vendor.
856 Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h.
857 The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports,
858 but by default they are held in reset after power on. In U-Boot, PCIe
859 initialization is properly handled as per Quark's firmware writer guide.
860 In your board support codes, you need provide two routines to aid PCIe
861 initialization, which are board_assert_perst() and board_deassert_perst().
862 The two routines need implement a board-specific mechanism to assert/deassert
863 PCIe PERST# pin. Care must be taken that in those routines that any APIs that
864 may trigger PCI enumeration process are strictly forbidden, as any access to
865 PCIe root port's configuration registers will cause system hang while it is
866 held in reset. For more details, check how they are implemented by the Intel
867 Galileo board support codes in board/intel/galileo/galileo.c.
871 See scripts/coreboot.sed which can assist with porting coreboot code into
872 U-Boot drivers. It will not resolve all build errors, but will perform common
873 transformations. Remember to add attribution to coreboot for new files added
874 to U-Boot. This should go at the top of each file and list the coreboot
875 filename where the code originated.
877 Debugging ACPI issues with Windows:
879 Windows might cache system information and only detect ACPI changes if you
880 modify the ACPI table versions. So tweak them liberally when debugging ACPI
885 Advanced Configuration and Power Interface (ACPI) [16] aims to establish
886 industry-standard interfaces enabling OS-directed configuration, power
887 management, and thermal management of mobile, desktop, and server platforms.
889 Linux can boot without ACPI with "acpi=off" command line parameter, but
890 with ACPI the kernel gains the capabilities to handle power management.
891 For Windows, ACPI is a must-have firmware feature since Windows Vista.
892 CONFIG_GENERATE_ACPI_TABLE is the config option to turn on ACPI support in
893 U-Boot. This requires Intel ACPI compiler to be installed on your host to
894 compile ACPI DSDT table written in ASL format to AML format. You can get
895 the compiler via "apt-get install iasl" if you are on Ubuntu or download
896 the source from [17] to compile one by yourself.
898 Current ACPI support in U-Boot is basically complete. More optional features
899 can be added in the future. The status as of today is:
901 * Support generating RSDT, XSDT, FACS, FADT, MADT, MCFG tables.
902 * Support one static DSDT table only, compiled by Intel ACPI compiler.
903 * Support S0/S3/S4/S5, reboot and shutdown from OS.
904 * Support booting a pre-installed Ubuntu distribution via 'zboot' command.
905 * Support installing and booting Ubuntu 14.04 (or above) from U-Boot with
906 the help of SeaBIOS using legacy interface (non-UEFI mode).
907 * Support installing and booting Windows 8.1/10 from U-Boot with the help
908 of SeaBIOS using legacy interface (non-UEFI mode).
909 * Support ACPI interrupts with SCI only.
911 Features that are optional:
912 * Dynamic AML bytecodes insertion at run-time. We may need this to support
913 SSDT table generation and DSDT fix up.
914 * SMI support. Since U-Boot is a modern bootloader, we don't want to bring
915 those legacy stuff into U-Boot. ACPI spec allows a system that does not
916 support SMI (a legacy-free system).
918 ACPI was initially enabled on BayTrail based boards. Testing was done by booting
919 a pre-installed Ubuntu 14.04 from a SATA drive. Installing Ubuntu 14.04 and
920 Windows 8.1/10 to a SATA drive and booting from there is also tested. Most
921 devices seem to work correctly and the board can respond a reboot/shutdown
924 For other platform boards, ACPI support status can be checked by examining their
925 board defconfig files to see if CONFIG_GENERATE_ACPI_TABLE is set to y.
927 The S3 sleeping state is a low wake latency sleeping state defined by ACPI
928 spec where all system context is lost except system memory. To test S3 resume
929 with a Linux kernel, simply run "echo mem > /sys/power/state" and kernel will
930 put the board to S3 state where the power is off. So when the power button is
931 pressed again, U-Boot runs as it does in cold boot and detects the sleeping
932 state via ACPI register to see if it is S3, if yes it means we are waking up.
933 U-Boot is responsible for restoring the machine state as it is before sleep.
934 When everything is done, U-Boot finds out the wakeup vector provided by OSes
935 and jump there. To determine whether ACPI S3 resume is supported, check to
936 see if CONFIG_HAVE_ACPI_RESUME is set for that specific board.
938 Note for testing S3 resume with Windows, correct graphics driver must be
939 installed for your platform, otherwise you won't find "Sleep" option in
940 the "Power" submenu from the Windows start menu.
944 U-Boot supports booting as a 32-bit or 64-bit EFI payload, e.g. with UEFI.
945 This is enabled with CONFIG_EFI_STUB to boot from both 32-bit and 64-bit
946 UEFI BIOS. U-Boot can also run as an EFI application, with CONFIG_EFI_APP.
947 The CONFIG_EFI_LOADER option, where U-Boot provides an EFI environment to
948 the kernel (i.e. replaces UEFI completely but provides the same EFI run-time
949 services) is supported too. For example, we can even use 'bootefi' command
950 to load a 'u-boot-payload.efi', see below test logs on QEMU.
952 => load ide 0 3000000 u-boot-payload.efi
953 489787 bytes read in 138 ms (3.4 MiB/s)
955 Scanning disk ide.blk#0...
957 WARNING: booting without device tree
958 ## Starting EFI application at 03000000 ...
962 U-Boot 2018.07-rc2 (Jun 23 2018 - 17:12:58 +0800)
964 CPU: x86_64, vendor AMD, device 663h
968 Model: EFI x86 Payload
969 Net: e1000: 52:54:00:12:34:56
971 Warning: e1000#0 using MAC address from ROM
974 Hit any key to stop autoboot: 0
976 See README.u-boot_on_efi and README.uefi for details of EFI support in U-Boot.
981 - Chrome OS verified boot
985 [1] http://www.coreboot.org
986 [2] http://www.qemu.org
987 [3] http://www.coreboot.org/~stepan/pci8086,0166.rom
988 [4] http://www.intel.com/content/www/us/en/embedded/design-tools/evaluation-platforms/atom-e660-eg20t-development-kit.html
989 [5] http://www.intel.com/fsp
990 [6] http://www.intel.com/content/www/us/en/secure/intelligent-systems/privileged/e6xx-35-b1-cmc22211.html
991 [7] http://www.ami.com/products/bios-uefi-tools-and-utilities/bios-uefi-utilities/
992 [8] http://en.wikipedia.org/wiki/Microcode
993 [9] http://simplefirmware.org
994 [10] http://www.intel.com/design/archives/processors/pro/docs/242016.htm
995 [11] https://en.wikipedia.org/wiki/GUID_Partition_Table
996 [12] http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf
997 [13] http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf
998 [14] http://www.seabios.org/SeaBIOS
999 [15] doc/device-tree-bindings/misc/intel,irq-router.txt
1000 [16] http://www.acpi.info
1001 [17] https://www.acpica.org/downloads