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 main bootloader
51 ------------------------------------------------
53 Intel Edison instructions:
55 Simple you can build U-Boot and obtain u-boot.bin
57 $ make edison_defconfig
60 Build Instructions for U-Boot as BIOS replacement (bare mode)
61 -------------------------------------------------------------
62 Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a
63 little bit tricky, as generally it requires several binary blobs which are not
64 shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build is
65 not turned on by default in the U-Boot source tree. Firstly, you need turn it
66 on by enabling the ROM build either via an environment variable
74 Both tell the Makefile to build u-boot.rom as a target.
78 Chromebook Link specific instructions for bare mode:
80 First, you need the following binary blobs:
82 * descriptor.bin - Intel flash descriptor
83 * me.bin - Intel Management Engine
84 * mrc.bin - Memory Reference Code, which sets up SDRAM
85 * video ROM - sets up the display
87 You can get these binary blobs by:
89 $ git clone http://review.coreboot.org/p/blobs.git
92 Find the following files:
94 * ./mainboard/google/link/descriptor.bin
95 * ./mainboard/google/link/me.bin
96 * ./northbridge/intel/sandybridge/systemagent-r6.bin
98 The 3rd one should be renamed to mrc.bin.
99 As for the video ROM, you can get it here [3] and rename it to vga.bin.
100 Make sure all these binary blobs are put in the board directory.
102 Now you can build U-Boot and obtain u-boot.rom:
104 $ make chromebook_link_defconfig
109 Chromebook Samus (2015 Pixel) instructions for bare mode:
111 First, you need the following binary blobs:
113 * descriptor.bin - Intel flash descriptor
114 * me.bin - Intel Management Engine
115 * mrc.bin - Memory Reference Code, which sets up SDRAM
116 * refcode.elf - Additional Reference code
117 * vga.bin - video ROM, which sets up the display
119 If you have a samus you can obtain them from your flash, for example, in
120 developer mode on the Chromebook (use Ctrl-Alt-F2 to obtain a terminal and
124 flashrom -w samus.bin
125 scp samus.bin username@ip_address:/path/to/somewhere
127 If not see the coreboot tree [4] where you can use:
129 bash crosfirmware.sh samus
131 to get the image. There is also an 'extract_blobs.sh' scripts that you can use
132 on the 'coreboot-Google_Samus.*' file to short-circuit some of the below.
134 Then 'ifdtool -x samus.bin' on your development machine will produce:
136 flashregion_0_flashdescriptor.bin
137 flashregion_1_bios.bin
138 flashregion_2_intel_me.bin
140 Rename flashregion_0_flashdescriptor.bin to descriptor.bin
141 Rename flashregion_2_intel_me.bin to me.bin
142 You can ignore flashregion_1_bios.bin - it is not used.
144 To get the rest, use 'cbfstool samus.bin print':
146 samus.bin: 8192 kB, bootblocksize 2864, romsize 8388608, offset 0x700000
147 alignment: 64 bytes, architecture: x86
149 Name Offset Type Size
150 cmos_layout.bin 0x700000 cmos_layout 1164
151 pci8086,0406.rom 0x7004c0 optionrom 65536
152 spd.bin 0x710500 (unknown) 4096
153 cpu_microcode_blob.bin 0x711540 microcode 70720
154 fallback/romstage 0x722a00 stage 54210
155 fallback/ramstage 0x72fe00 stage 96382
156 config 0x7476c0 raw 6075
157 fallback/vboot 0x748ec0 stage 15980
158 fallback/refcode 0x74cd80 stage 75578
159 fallback/payload 0x75f500 payload 62878
160 u-boot.dtb 0x76eb00 (unknown) 5318
161 (empty) 0x770000 null 196504
162 mrc.bin 0x79ffc0 (unknown) 222876
163 (empty) 0x7d66c0 null 167320
165 You can extract what you need:
167 cbfstool samus.bin extract -n pci8086,0406.rom -f vga.bin
168 cbfstool samus.bin extract -n fallback/refcode -f refcode.rmod
169 cbfstool samus.bin extract -n mrc.bin -f mrc.bin
170 cbfstool samus.bin extract -n fallback/refcode -f refcode.bin -U
172 Note that the -U flag is only supported by the latest cbfstool. It unpacks
173 and decompresses the stage to produce a coreboot rmodule. This is a simple
174 representation of an ELF file. You need the patch "Support decoding a stage
177 Put all 5 files into board/google/chromebook_samus.
179 Now you can build U-Boot and obtain u-boot.rom:
181 $ make chromebook_link_defconfig
184 If you are using em100, then this command will flash write -Boot:
186 em100 -s -d filename.rom -c W25Q64CV -r
188 Flash map for samus / broadwell:
190 fffff800 SYS_X86_START16
191 ffff0000 RESET_SEG_START
192 fffd8000 TPL_TEXT_BASE
193 fffa0000 X86_MRC_ADDR
194 fff90000 VGA_BIOS_ADDR
195 ffed0000 SYS_TEXT_BASE
196 ffea0000 X86_REFCODE_ADDR
197 ffe70000 SPL_TEXT_BASE
198 ffbf8000 CONFIG_ENV_OFFSET (environemnt offset)
199 ffbe0000 rw-mrc-cache (Memory-reference-code cache)
201 ff801000 intel-me (address set by descriptor.bin)
202 ff800000 intel-descriptor
206 Intel Cougar Canyon 2 specific instructions for bare mode:
208 This uses Intel FSP for 3rd generation Intel Core and Intel Celeron processors
209 with mobile Intel HM76 and QM77 chipsets platform. Download it from Intel FSP
210 website and put the .fd file (CHIEFRIVER_FSP_GOLD_001_09-OCTOBER-2013.fd at the
211 time of writing) in the board directory and rename it to fsp.bin.
213 Now build U-Boot and obtain u-boot.rom
215 $ make cougarcanyon2_defconfig
218 The board has two 8MB SPI flashes mounted, which are called SPI-0 and SPI-1 in
219 the board manual. The SPI-0 flash should have flash descriptor plus ME firmware
220 and SPI-1 flash is used to store U-Boot. For convenience, the complete 8MB SPI-0
221 flash image is included in the FSP package (named Rom00_8M_MB_PPT.bin). Program
222 this image to the SPI-0 flash according to the board manual just once and we are
223 all set. For programming U-Boot we just need to program SPI-1 flash. Since the
224 default u-boot.rom image for this board is set to 2MB, it should be programmed
225 to the last 2MB of the 8MB chip, address range [600000, 7FFFFF].
229 Intel Galileo instructions for bare mode:
231 Only one binary blob is needed for Remote Management Unit (RMU) within Intel
232 Quark SoC. Not like FSP, U-Boot does not call into the binary. The binary is
233 needed by the Quark SoC itself.
235 You can get the binary blob from Quark Board Support Package from Intel website:
237 * ./QuarkSocPkg/QuarkNorthCluster/Binary/QuarkMicrocode/RMU.bin
239 Rename the file and put it to the board directory by:
241 $ cp RMU.bin board/intel/galileo/rmu.bin
243 Now you can build U-Boot and obtain u-boot.rom
245 $ make galileo_defconfig
250 QEMU x86 target instructions for bare mode:
252 To build u-boot.rom for QEMU x86 targets, just simply run
254 $ make qemu-x86_defconfig (for 32-bit)
256 $ make qemu-x86_64_defconfig (for 64-bit)
259 Note this default configuration will build a U-Boot for the QEMU x86 i440FX
260 board. To build a U-Boot against QEMU x86 Q35 board, you can change the build
261 configuration during the 'make menuconfig' process like below:
263 Device Tree Control --->
265 (qemu-x86_q35) Default Device Tree for DT control
269 For testing U-Boot as the coreboot payload, there are things that need be paid
270 attention to. coreboot supports loading an ELF executable and a 32-bit plain
271 binary, as well as other supported payloads. With the default configuration,
272 U-Boot is set up to use a separate Device Tree Blob (dtb). As of today, the
273 generated u-boot-dtb.bin needs to be packaged by the cbfstool utility (a tool
274 provided by coreboot) manually as coreboot's 'make menuconfig' does not provide
275 this capability yet. The command is as follows:
277 # in the coreboot root directory
278 $ ./build/util/cbfstool/cbfstool build/coreboot.rom add-flat-binary \
279 -f u-boot-dtb.bin -n fallback/payload -c lzma -l 0x1110000 -e 0x1110000
281 Make sure 0x1110000 matches CONFIG_SYS_TEXT_BASE, which is the symbol address
282 of _x86boot_start (in arch/x86/cpu/start.S).
284 If you want to use ELF as the coreboot payload, change U-Boot configuration to
285 use CONFIG_OF_EMBED instead of CONFIG_OF_SEPARATE.
287 To enable video you must enable these options in coreboot:
289 - Set framebuffer graphics resolution (1280x1024 32k-color (1:5:5))
290 - Keep VESA framebuffer
292 At present it seems that for Minnowboard Max, coreboot does not pass through
293 the video information correctly (it always says the resolution is 0x0). This
294 works correctly for link though.
296 Test with QEMU for bare mode
297 ----------------------------
298 QEMU is a fancy emulator that can enable us to test U-Boot without access to
299 a real x86 board. Please make sure your QEMU version is 2.3.0 or above test
300 U-Boot. To launch QEMU with u-boot.rom, call QEMU as follows:
302 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom
304 This will instantiate an emulated x86 board with i440FX and PIIX chipset. QEMU
305 also supports emulating an x86 board with Q35 and ICH9 based chipset, which is
306 also supported by U-Boot. To instantiate such a machine, call QEMU with:
308 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -M q35
310 Note by default QEMU instantiated boards only have 128 MiB system memory. But
311 it is enough to have U-Boot boot and function correctly. You can increase the
312 system memory by pass '-m' parameter to QEMU if you want more memory:
314 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024
316 This creates a board with 1 GiB system memory. Currently U-Boot for QEMU only
317 supports 3 GiB maximum system memory and reserves the last 1 GiB address space
318 for PCI device memory-mapped I/O and other stuff, so the maximum value of '-m'
321 QEMU emulates a graphic card which U-Boot supports. Removing '-nographic' will
322 show QEMU's VGA console window. Note this will disable QEMU's serial output.
323 If you want to check both consoles, use '-serial stdio'.
325 Multicore is also supported by QEMU via '-smp n' where n is the number of cores
326 to instantiate. Note, the maximum supported CPU number in QEMU is 255.
328 The fw_cfg interface in QEMU also provides information about kernel data,
329 initrd, command-line arguments and more. U-Boot supports directly accessing
330 these informtion from fw_cfg interface, which saves the time of loading them
331 from hard disk or network again, through emulated devices. To use it , simply
332 providing them in QEMU command line:
334 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024 -kernel /path/to/bzImage
335 -append 'root=/dev/ram console=ttyS0' -initrd /path/to/initrd -smp 8
337 Note: -initrd and -smp are both optional
339 Then start QEMU, in U-Boot command line use the following U-Boot command to
343 qfw - QEMU firmware interface
347 - list : print firmware(s) currently loaded
348 - cpus : print online cpu number
349 - load <kernel addr> <initrd addr> : load kernel and initrd (if any) and setup for zboot
352 loading kernel to address 01000000 size 5d9d30 initrd 04000000 size 1b1ab50
354 Here the kernel (bzImage) is loaded to 01000000 and initrd is to 04000000. Then,
355 'zboot' can be used to boot the kernel:
357 => zboot 01000000 - 04000000 1b1ab50
359 To run 64-bit U-Boot, qemu-system-x86_64 should be used instead, e.g.:
360 $ qemu-system-x86_64 -nographic -bios path/to/u-boot.rom
362 A specific CPU can be specified via the '-cpu' parameter but please make
363 sure the specified CPU supports 64-bit like '-cpu core2duo'. Conversely
364 '-cpu pentium' won't work for obvious reasons that the processor only
367 Note 64-bit support is very preliminary at this point. Lots of features
368 are missing in the 64-bit world. One notable feature is the VGA console
369 support which is currently missing, so that you must specify '-nographic'
370 to get 64-bit U-Boot up and running.
372 Updating U-Boot on Edison
373 -------------------------
374 By default Intel Edison boards are shipped with preinstalled heavily
375 patched U-Boot v2014.04. Though it supports DFU which we may be able to
378 1. Prepare u-boot.bin as described in chapter above. You still need one
379 more step (if and only if you have original U-Boot), i.e. run the
382 $ truncate -s %4096 u-boot.bin
384 2. Run your board and interrupt booting to U-Boot console. In the console
387 => run do_force_flash_os
389 3. Wait for few seconds, it will prepare environment variable and runs
390 DFU. Run DFU command from the host system:
392 $ dfu-util -v -d 8087:0a99 --alt u-boot0 -D u-boot.bin
394 4. Return to U-Boot console and following hint. i.e. push Ctrl+C, and
401 Modern CPUs usually require a special bit stream called microcode [8] to be
402 loaded on the processor after power up in order to function properly. U-Boot
403 has already integrated these as hex dumps in the source tree.
407 On a multicore system, U-Boot is executed on the bootstrap processor (BSP).
408 Additional application processors (AP) can be brought up by U-Boot. In order to
409 have an SMP kernel to discover all of the available processors, U-Boot needs to
410 prepare configuration tables which contain the multi-CPUs information before
411 loading the OS kernel. Currently U-Boot supports generating two types of tables
412 for SMP, called Simple Firmware Interface (SFI) [9] and Multi-Processor (MP)
413 [10] tables. The writing of these two tables are controlled by two Kconfig
414 options GENERATE_SFI_TABLE and GENERATE_MP_TABLE.
418 x86 has been converted to use driver model for serial, GPIO, SPI, SPI flash,
419 keyboard, real-time clock, USB. Video is in progress.
423 x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to
424 be turned on. Not every device on the board is configured via device tree, but
425 more and more devices will be added as time goes by. Check out the directory
426 arch/x86/dts/ for these device tree source files.
430 In keeping with the U-Boot philosophy of providing functions to check and
431 adjust internal settings, there are several x86-specific commands that may be
434 fsp - Display information about Intel Firmware Support Package (FSP).
435 This is only available on platforms which use FSP, mostly Atom.
436 iod - Display I/O memory
437 iow - Write I/O memory
438 mtrr - List and set the Memory Type Range Registers (MTRR). These are used to
439 tell the CPU whether memory is cacheable and if so the cache write
440 mode to use. U-Boot sets up some reasonable values but you can
441 adjust then with this command.
445 As an example of how to set up your boot flow with U-Boot, here are
446 instructions for starting Ubuntu from U-Boot. These instructions have been
447 tested on Minnowboard MAX with a SATA drive but are equally applicable on
448 other platforms and other media. There are really only four steps and it's a
449 very simple script, but a more detailed explanation is provided here for
452 Note: It is possible to set up U-Boot to boot automatically using syslinux.
453 It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the
454 GUID. If you figure these out, please post patches to this README.
456 Firstly, you will need Ubuntu installed on an available disk. It should be
457 possible to make U-Boot start a USB start-up disk but for now let's assume
458 that you used another boot loader to install Ubuntu.
460 Use the U-Boot command line to find the UUID of the partition you want to
461 boot. For example our disk is SCSI device 0:
465 Partition Map for SCSI device 0 -- Partition Type: EFI
467 Part Start LBA End LBA Name
471 1 0x00000800 0x001007ff ""
472 attrs: 0x0000000000000000
473 type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b
474 guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c
475 2 0x00100800 0x037d8fff ""
476 attrs: 0x0000000000000000
477 type: 0fc63daf-8483-4772-8e79-3d69d8477de4
478 guid: 965c59ee-1822-4326-90d2-b02446050059
479 3 0x037d9000 0x03ba27ff ""
480 attrs: 0x0000000000000000
481 type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f
482 guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17
485 This shows that your SCSI disk has three partitions. The really long hex
486 strings are called Globally Unique Identifiers (GUIDs). You can look up the
487 'type' ones here [11]. On this disk the first partition is for EFI and is in
488 VFAT format (DOS/Windows):
496 Partition 2 is 'Linux filesystem data' so that will be our root disk. It is
502 <DIR> 16384 lost+found
525 <SYM> 33 initrd.img.old
528 and if you look in the /boot directory you will see the kernel:
530 => ext2ls scsi 0:2 /boot
535 3381262 System.map-3.13.0-32-generic
536 1162712 abi-3.13.0-32-generic
537 165611 config-3.13.0-32-generic
538 176500 memtest86+.bin
539 178176 memtest86+.elf
540 178680 memtest86+_multiboot.bin
541 5798112 vmlinuz-3.13.0-32-generic
542 165762 config-3.13.0-58-generic
543 1165129 abi-3.13.0-58-generic
544 5823136 vmlinuz-3.13.0-58-generic
545 19215259 initrd.img-3.13.0-58-generic
546 3391763 System.map-3.13.0-58-generic
547 5825048 vmlinuz-3.13.0-58-generic.efi.signed
548 28304443 initrd.img-3.13.0-32-generic
551 The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of
552 self-extracting compressed file mixed with some 'setup' configuration data.
553 Despite its size (uncompressed it is >10MB) this only includes a basic set of
554 device drivers, enough to boot on most hardware types.
556 The 'initrd' files contain a RAM disk. This is something that can be loaded
557 into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots
558 of drivers for whatever hardware you might have. It is loaded before the
559 real root disk is accessed.
561 The numbers after the end of each file are the version. Here it is Linux
562 version 3.13. You can find the source code for this in the Linux tree with
563 the tag v3.13. The '.0' allows for additional Linux releases to fix problems,
564 but normally this is not needed. The '-58' is used by Ubuntu. Each time they
565 release a new kernel they increment this number. New Ubuntu versions might
566 include kernel patches to fix reported bugs. Stable kernels can exist for
567 some years so this number can get quite high.
569 The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own
570 secure boot mechanism - see [12] [13] and cannot read .efi files at present.
572 To boot Ubuntu from U-Boot the steps are as follows:
574 1. Set up the boot arguments. Use the GUID for the partition you want to
577 => setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro
579 Here root= tells Linux the location of its root disk. The disk is specified
580 by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory'
581 containing all the GUIDs Linux has found. When it starts up, there will be a
582 file in that directory with this name in it. It is also possible to use a
583 device name here, see later.
585 2. Load the kernel. Since it is an ext2/4 filesystem we can do:
587 => ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic
589 The address 30000000 is arbitrary, but there seem to be problems with using
590 small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into
591 the start of RAM (which is at 0 on x86).
593 3. Load the ramdisk (to 64MB):
595 => ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic
597 4. Start up the kernel. We need to know the size of the ramdisk, but can use
598 a variable for that. U-Boot sets 'filesize' to the size of the last file it
601 => zboot 03000000 0 04000000 ${filesize}
603 Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is
604 quite verbose when it boots a kernel. You should see these messages from
608 Setup Size = 0x00004400
609 Magic signature found
610 Using boot protocol version 2.0c
611 Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015
612 Building boot_params at 0x00090000
613 Loading bzImage at address 100000 (5805728 bytes)
614 Magic signature found
615 Initial RAM disk at linear address 0x04000000, size 19215259 bytes
616 Kernel command line: "root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro"
620 U-Boot prints out some bootstage timing. This is more useful if you put the
621 above commands into a script since then it will be faster.
623 Timer summary in microseconds:
626 241,535 241,535 board_init_r
627 2,421,611 2,180,076 id=64
629 2,428,215 6,425 main_loop
630 48,860,584 46,432,369 start_kernel
634 1,422,704 vesa display
636 Now the kernel actually starts: (if you want to examine kernel boot up message
637 on the serial console, append "console=ttyS0,115200" to the kernel command line)
639 [ 0.000000] Initializing cgroup subsys cpuset
640 [ 0.000000] Initializing cgroup subsys cpu
641 [ 0.000000] Initializing cgroup subsys cpuacct
642 [ 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)
643 [ 0.000000] Command line: root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro console=ttyS0,115200
645 It continues for a long time. Along the way you will see it pick up your
648 [ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff]
650 [ 0.788540] Trying to unpack rootfs image as initramfs...
651 [ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000)
654 Later it actually starts using it:
656 Begin: Running /scripts/local-premount ... done.
658 You should also see your boot disk turn up:
660 [ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5
661 [ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB)
662 [ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0
663 [ 4.381859] sd 1:0:0:0: [sda] Write Protect is off
664 [ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
665 [ 4.399535] sda: sda1 sda2 sda3
667 Linux has found the three partitions (sda1-3). Mercifully it doesn't print out
668 the GUIDs. In step 1 above we could have used:
670 setenv bootargs root=/dev/sda2 ro
672 instead of the GUID. However if you add another drive to your board the
673 numbering may change whereas the GUIDs will not. So if your boot partition
674 becomes sdb2, it will still boot. For embedded systems where you just want to
675 boot the first disk, you have that option.
677 The last thing you will see on the console is mention of plymouth (which
678 displays the Ubuntu start-up screen) and a lot of 'Starting' messages:
680 * Starting Mount filesystems on boot [ OK ]
682 After a pause you should see a login screen on your display and you are done.
684 If you want to put this in a script you can use something like this:
686 setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro
687 setenv boot zboot 03000000 0 04000000 \${filesize}
688 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"
691 The \ is to tell the shell not to evaluate ${filesize} as part of the setenv
694 You can also bake this behaviour into your build by hard-coding the
695 environment variables if you add this to minnowmax.h:
697 #undef CONFIG_BOOTCOMMAND
698 #define CONFIG_BOOTCOMMAND \
699 "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \
700 "ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \
703 #undef CONFIG_EXTRA_ENV_SETTINGS
704 #define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}"
706 and change CONFIG_BOOTARGS value in configs/minnowmax_defconfig to:
708 CONFIG_BOOTARGS="root=/dev/sda2 ro"
712 SeaBIOS [14] is an open source implementation of a 16-bit x86 BIOS. It can run
713 in an emulator or natively on x86 hardware with the use of U-Boot. With its
714 help, we can boot some OSes that require 16-bit BIOS services like Windows/DOS.
716 As U-Boot, we have to manually create a table where SeaBIOS gets various system
717 information (eg: E820) from. The table unfortunately has to follow the coreboot
718 table format as SeaBIOS currently supports booting as a coreboot payload.
720 To support loading SeaBIOS, U-Boot should be built with CONFIG_SEABIOS on.
721 Booting SeaBIOS is done via U-Boot's bootelf command, like below:
723 => tftp bios.bin.elf;bootelf
725 TFTP from server 10.10.0.100; our IP address is 10.10.0.108
727 Bytes transferred = 122124 (1dd0c hex)
728 ## Starting application at 0x000ff06e ...
729 SeaBIOS (version rel-1.9.0)
732 bios.bin.elf is the SeaBIOS image built from SeaBIOS source tree.
733 Make sure it is built as follows:
737 Inside the "General Features" menu, select "Build for coreboot" as the
738 "Build Target". Inside the "Debugging" menu, turn on "Serial port debugging"
739 so that we can see something as soon as SeaBIOS boots. Leave other options
740 as in their default state. Then,
744 Total size: 121888 Fixed: 66496 Free: 9184 (used 93.0% of 128KiB rom)
745 Creating out/bios.bin.elf
747 Currently this is tested on QEMU x86 target with U-Boot chain-loading SeaBIOS
748 to install/boot a Windows XP OS (below for example command to install Windows).
750 # Create a 10G disk.img as the virtual hard disk
751 $ qemu-img create -f qcow2 disk.img 10G
753 # Install a Windows XP OS from an ISO image 'winxp.iso'
754 $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -cdrom winxp.iso -smp 2 -m 512
756 # Boot a Windows XP OS installed on the virutal hard disk
757 $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -smp 2 -m 512
759 This is also tested on Intel Crown Bay board with a PCIe graphics card, booting
760 SeaBIOS then chain-loading a GRUB on a USB drive, then Linux kernel finally.
762 If you are using Intel Integrated Graphics Device (IGD) as the primary display
763 device on your board, SeaBIOS needs to be patched manually to get its VGA ROM
764 loaded and run by SeaBIOS. SeaBIOS locates VGA ROM via the PCI expansion ROM
765 register, but IGD device does not have its VGA ROM mapped by this register.
766 Its VGA ROM is packaged as part of u-boot.rom at a configurable flash address
767 which is unknown to SeaBIOS. An example patch is needed for SeaBIOS below:
769 diff --git a/src/optionroms.c b/src/optionroms.c
770 index 65f7fe0..c7b6f5e 100644
771 --- a/src/optionroms.c
772 +++ b/src/optionroms.c
773 @@ -324,6 +324,8 @@ init_pcirom(struct pci_device *pci, int isvga, u64 *sources)
774 rom = deploy_romfile(file);
775 else if (RunPCIroms > 1 || (RunPCIroms == 1 && isvga))
776 rom = map_pcirom(pci);
777 + if (pci->bdf == pci_to_bdf(0, 2, 0))
778 + rom = (struct rom_header *)0xfff90000;
783 Note: the patch above expects IGD device is at PCI b.d.f 0.2.0 and its VGA ROM
784 is at 0xfff90000 which corresponds to CONFIG_VGA_BIOS_ADDR on Minnowboard MAX.
785 Change these two accordingly if this is not the case on your board.
789 These notes are for those who want to port U-Boot to a new x86 platform.
791 Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment.
792 The Dediprog em100 can be used on Linux. The em100 tool is available here:
794 http://review.coreboot.org/p/em100.git
796 On Minnowboard Max the following command line can be used:
798 sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r
800 A suitable clip for connecting over the SPI flash chip is here:
802 http://www.dediprog.com/pd/programmer-accessories/EM-TC-8
804 This allows you to override the SPI flash contents for development purposes.
805 Typically you can write to the em100 in around 1200ms, considerably faster
806 than programming the real flash device each time. The only important
807 limitation of the em100 is that it only supports SPI bus speeds up to 20MHz.
808 This means that images must be set to boot with that speed. This is an
809 Intel-specific feature - e.g. tools/ifttool has an option to set the SPI
810 speed in the SPI descriptor region.
812 If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly
813 easy to fit it in. You can follow the Minnowboard Max implementation, for
814 example. Hopefully you will just need to create new files similar to those
815 in arch/x86/cpu/baytrail which provide Bay Trail support.
817 If you are not using an FSP you have more freedom and more responsibility.
818 The ivybridge support works this way, although it still uses a ROM for
819 graphics and still has binary blobs containing Intel code. You should aim to
820 support all important peripherals on your platform including video and storage.
821 Use the device tree for configuration where possible.
823 For the microcode you can create a suitable device tree file using the
826 ./tools/microcode-tool -d microcode.dat -m <model> create
828 or if you only have header files and not the full Intel microcode.dat database:
830 ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \
831 -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h \
834 These are written to arch/x86/dts/microcode/ by default.
836 Note that it is possible to just add the micrcode for your CPU if you know its
837 model. U-Boot prints this information when it starts
839 CPU: x86_64, vendor Intel, device 30673h
841 so here we can use the M0130673322 file.
843 If you platform can display POST codes on two little 7-segment displays on
844 the board, then you can use post_code() calls from C or assembler to monitor
845 boot progress. This can be good for debugging.
847 If not, you can try to get serial working as early as possible. The early
848 debug serial port may be useful here. See setup_internal_uart() for an example.
850 During the U-Boot porting, one of the important steps is to write correct PIRQ
851 routing information in the board device tree. Without it, device drivers in the
852 Linux kernel won't function correctly due to interrupt is not working. Please
853 refer to U-Boot doc [15] for the device tree bindings of Intel interrupt router.
854 Here we have more details on the intel,pirq-routing property below.
856 intel,pirq-routing = <
857 PCI_BDF(0, 2, 0) INTA PIRQA
861 As you see each entry has 3 cells. For the first one, we need describe all pci
862 devices mounted on the board. For SoC devices, normally there is a chapter on
863 the chipset datasheet which lists all the available PCI devices. For example on
864 Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we
865 can get the interrupt pin either from datasheet or hardware via U-Boot shell.
866 The reliable source is the hardware as sometimes chipset datasheet is not 100%
867 up-to-date. Type 'pci header' plus the device's pci bus/device/function number
868 from U-Boot shell below.
874 interrupt line = 0x09
878 It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin
879 register. Repeat this until you get interrupt pins for all the devices. The last
880 cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel
881 chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This
882 can be changed by registers in LPC bridge. So far Intel FSP does not touch those
883 registers so we can write down the PIRQ according to the default mapping rule.
885 Once we get the PIRQ routing information in the device tree, the interrupt
886 allocation and assignment will be done by U-Boot automatically. Now you can
887 enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and
888 CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC.
890 This script might be useful. If you feed it the output of 'pci long' from
891 U-Boot then it will generate a device tree fragment with the interrupt
892 configuration for each device (note it needs gawk 4.0.0):
894 $ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \
895 /interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \
896 {patsplit(device, bdf, "[0-9a-f]+"); \
897 printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \
898 strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}'
901 PCI_BDF(0, 2, 0) INTA PIRQA
902 PCI_BDF(0, 3, 0) INTA PIRQA
908 Quark-specific considerations:
910 To port U-Boot to other boards based on the Intel Quark SoC, a few things need
911 to be taken care of. The first important part is the Memory Reference Code (MRC)
912 parameters. Quark MRC supports memory-down configuration only. All these MRC
913 parameters are supplied via the board device tree. To get started, first copy
914 the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then
915 change these values by consulting board manuals or your hardware vendor.
916 Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h.
917 The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports,
918 but by default they are held in reset after power on. In U-Boot, PCIe
919 initialization is properly handled as per Quark's firmware writer guide.
920 In your board support codes, you need provide two routines to aid PCIe
921 initialization, which are board_assert_perst() and board_deassert_perst().
922 The two routines need implement a board-specific mechanism to assert/deassert
923 PCIe PERST# pin. Care must be taken that in those routines that any APIs that
924 may trigger PCI enumeration process are strictly forbidden, as any access to
925 PCIe root port's configuration registers will cause system hang while it is
926 held in reset. For more details, check how they are implemented by the Intel
927 Galileo board support codes in board/intel/galileo/galileo.c.
931 See scripts/coreboot.sed which can assist with porting coreboot code into
932 U-Boot drivers. It will not resolve all build errors, but will perform common
933 transformations. Remember to add attribution to coreboot for new files added
934 to U-Boot. This should go at the top of each file and list the coreboot
935 filename where the code originated.
937 Debugging ACPI issues with Windows:
939 Windows might cache system information and only detect ACPI changes if you
940 modify the ACPI table versions. So tweak them liberally when debugging ACPI
945 Advanced Configuration and Power Interface (ACPI) [16] aims to establish
946 industry-standard interfaces enabling OS-directed configuration, power
947 management, and thermal management of mobile, desktop, and server platforms.
949 Linux can boot without ACPI with "acpi=off" command line parameter, but
950 with ACPI the kernel gains the capabilities to handle power management.
951 For Windows, ACPI is a must-have firmware feature since Windows Vista.
952 CONFIG_GENERATE_ACPI_TABLE is the config option to turn on ACPI support in
953 U-Boot. This requires Intel ACPI compiler to be installed on your host to
954 compile ACPI DSDT table written in ASL format to AML format. You can get
955 the compiler via "apt-get install iasl" if you are on Ubuntu or download
956 the source from [17] to compile one by yourself.
958 Current ACPI support in U-Boot is basically complete. More optional features
959 can be added in the future. The status as of today is:
961 * Support generating RSDT, XSDT, FACS, FADT, MADT, MCFG tables.
962 * Support one static DSDT table only, compiled by Intel ACPI compiler.
963 * Support S0/S3/S4/S5, reboot and shutdown from OS.
964 * Support booting a pre-installed Ubuntu distribution via 'zboot' command.
965 * Support installing and booting Ubuntu 14.04 (or above) from U-Boot with
966 the help of SeaBIOS using legacy interface (non-UEFI mode).
967 * Support installing and booting Windows 8.1/10 from U-Boot with the help
968 of SeaBIOS using legacy interface (non-UEFI mode).
969 * Support ACPI interrupts with SCI only.
971 Features that are optional:
972 * Dynamic AML bytecodes insertion at run-time. We may need this to support
973 SSDT table generation and DSDT fix up.
974 * SMI support. Since U-Boot is a modern bootloader, we don't want to bring
975 those legacy stuff into U-Boot. ACPI spec allows a system that does not
976 support SMI (a legacy-free system).
978 ACPI was initially enabled on BayTrail based boards. Testing was done by booting
979 a pre-installed Ubuntu 14.04 from a SATA drive. Installing Ubuntu 14.04 and
980 Windows 8.1/10 to a SATA drive and booting from there is also tested. Most
981 devices seem to work correctly and the board can respond a reboot/shutdown
984 For other platform boards, ACPI support status can be checked by examining their
985 board defconfig files to see if CONFIG_GENERATE_ACPI_TABLE is set to y.
987 The S3 sleeping state is a low wake latency sleeping state defined by ACPI
988 spec where all system context is lost except system memory. To test S3 resume
989 with a Linux kernel, simply run "echo mem > /sys/power/state" and kernel will
990 put the board to S3 state where the power is off. So when the power button is
991 pressed again, U-Boot runs as it does in cold boot and detects the sleeping
992 state via ACPI register to see if it is S3, if yes it means we are waking up.
993 U-Boot is responsible for restoring the machine state as it is before sleep.
994 When everything is done, U-Boot finds out the wakeup vector provided by OSes
995 and jump there. To determine whether ACPI S3 resume is supported, check to
996 see if CONFIG_HAVE_ACPI_RESUME is set for that specific board.
998 Note for testing S3 resume with Windows, correct graphics driver must be
999 installed for your platform, otherwise you won't find "Sleep" option in
1000 the "Power" submenu from the Windows start menu.
1004 U-Boot supports booting as a 32-bit or 64-bit EFI payload, e.g. with UEFI.
1005 This is enabled with CONFIG_EFI_STUB to boot from both 32-bit and 64-bit
1006 UEFI BIOS. U-Boot can also run as an EFI application, with CONFIG_EFI_APP.
1007 The CONFIG_EFI_LOADER option, where U-Boot provides an EFI environment to
1008 the kernel (i.e. replaces UEFI completely but provides the same EFI run-time
1009 services) is supported too. For example, we can even use 'bootefi' command
1010 to load a 'u-boot-payload.efi', see below test logs on QEMU.
1012 => load ide 0 3000000 u-boot-payload.efi
1013 489787 bytes read in 138 ms (3.4 MiB/s)
1015 Scanning disk ide.blk#0...
1017 WARNING: booting without device tree
1018 ## Starting EFI application at 03000000 ...
1022 U-Boot 2018.07-rc2 (Jun 23 2018 - 17:12:58 +0800)
1024 CPU: x86_64, vendor AMD, device 663h
1028 Model: EFI x86 Payload
1029 Net: e1000: 52:54:00:12:34:56
1031 Warning: e1000#0 using MAC address from ROM
1033 No controllers found
1034 Hit any key to stop autoboot: 0
1036 See README.u-boot_on_efi and README.uefi for details of EFI support in U-Boot.
1041 - Chrome OS verified boot
1045 [1] http://www.coreboot.org
1046 [2] http://www.qemu.org
1047 [3] http://www.coreboot.org/~stepan/pci8086,0166.rom
1048 [4] http://www.intel.com/content/www/us/en/embedded/design-tools/evaluation-platforms/atom-e660-eg20t-development-kit.html
1049 [5] http://www.intel.com/fsp
1050 [6] http://www.intel.com/content/www/us/en/secure/intelligent-systems/privileged/e6xx-35-b1-cmc22211.html
1051 [7] http://www.ami.com/products/bios-uefi-tools-and-utilities/bios-uefi-utilities/
1052 [8] http://en.wikipedia.org/wiki/Microcode
1053 [9] http://simplefirmware.org
1054 [10] http://www.intel.com/design/archives/processors/pro/docs/242016.htm
1055 [11] https://en.wikipedia.org/wiki/GUID_Partition_Table
1056 [12] http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf
1057 [13] http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf
1058 [14] http://www.seabios.org/SeaBIOS
1059 [15] doc/device-tree-bindings/misc/intel,irq-router.txt
1060 [16] http://www.acpi.info
1061 [17] https://www.acpica.org/downloads