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 QEMU x86 target instructions for bare mode:
70 To build u-boot.rom for QEMU x86 targets, just simply run
72 $ make qemu-x86_defconfig (for 32-bit)
74 $ make qemu-x86_64_defconfig (for 64-bit)
77 Note this default configuration will build a U-Boot for the QEMU x86 i440FX
78 board. To build a U-Boot against QEMU x86 Q35 board, you can change the build
79 configuration during the 'make menuconfig' process like below:
81 Device Tree Control --->
83 (qemu-x86_q35) Default Device Tree for DT control
87 For testing U-Boot as the coreboot payload, there are things that need be paid
88 attention to. coreboot supports loading an ELF executable and a 32-bit plain
89 binary, as well as other supported payloads. With the default configuration,
90 U-Boot is set up to use a separate Device Tree Blob (dtb). As of today, the
91 generated u-boot-dtb.bin needs to be packaged by the cbfstool utility (a tool
92 provided by coreboot) manually as coreboot's 'make menuconfig' does not provide
93 this capability yet. The command is as follows:
95 # in the coreboot root directory
96 $ ./build/util/cbfstool/cbfstool build/coreboot.rom add-flat-binary \
97 -f u-boot-dtb.bin -n fallback/payload -c lzma -l 0x1110000 -e 0x1110000
99 Make sure 0x1110000 matches CONFIG_SYS_TEXT_BASE, which is the symbol address
100 of _x86boot_start (in arch/x86/cpu/start.S).
102 If you want to use ELF as the coreboot payload, change U-Boot configuration to
103 use CONFIG_OF_EMBED instead of CONFIG_OF_SEPARATE.
105 To enable video you must enable these options in coreboot:
107 - Set framebuffer graphics resolution (1280x1024 32k-color (1:5:5))
108 - Keep VESA framebuffer
110 At present it seems that for Minnowboard Max, coreboot does not pass through
111 the video information correctly (it always says the resolution is 0x0). This
112 works correctly for link though.
114 Test with QEMU for bare mode
115 ----------------------------
116 QEMU is a fancy emulator that can enable us to test U-Boot without access to
117 a real x86 board. Please make sure your QEMU version is 2.3.0 or above test
118 U-Boot. To launch QEMU with u-boot.rom, call QEMU as follows:
120 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom
122 This will instantiate an emulated x86 board with i440FX and PIIX chipset. QEMU
123 also supports emulating an x86 board with Q35 and ICH9 based chipset, which is
124 also supported by U-Boot. To instantiate such a machine, call QEMU with:
126 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -M q35
128 Note by default QEMU instantiated boards only have 128 MiB system memory. But
129 it is enough to have U-Boot boot and function correctly. You can increase the
130 system memory by pass '-m' parameter to QEMU if you want more memory:
132 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024
134 This creates a board with 1 GiB system memory. Currently U-Boot for QEMU only
135 supports 3 GiB maximum system memory and reserves the last 1 GiB address space
136 for PCI device memory-mapped I/O and other stuff, so the maximum value of '-m'
139 QEMU emulates a graphic card which U-Boot supports. Removing '-nographic' will
140 show QEMU's VGA console window. Note this will disable QEMU's serial output.
141 If you want to check both consoles, use '-serial stdio'.
143 Multicore is also supported by QEMU via '-smp n' where n is the number of cores
144 to instantiate. Note, the maximum supported CPU number in QEMU is 255.
146 The fw_cfg interface in QEMU also provides information about kernel data,
147 initrd, command-line arguments and more. U-Boot supports directly accessing
148 these informtion from fw_cfg interface, which saves the time of loading them
149 from hard disk or network again, through emulated devices. To use it , simply
150 providing them in QEMU command line:
152 $ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024 -kernel /path/to/bzImage
153 -append 'root=/dev/ram console=ttyS0' -initrd /path/to/initrd -smp 8
155 Note: -initrd and -smp are both optional
157 Then start QEMU, in U-Boot command line use the following U-Boot command to
161 qfw - QEMU firmware interface
165 - list : print firmware(s) currently loaded
166 - cpus : print online cpu number
167 - load <kernel addr> <initrd addr> : load kernel and initrd (if any) and setup for zboot
170 loading kernel to address 01000000 size 5d9d30 initrd 04000000 size 1b1ab50
172 Here the kernel (bzImage) is loaded to 01000000 and initrd is to 04000000. Then,
173 'zboot' can be used to boot the kernel:
175 => zboot 01000000 - 04000000 1b1ab50
177 To run 64-bit U-Boot, qemu-system-x86_64 should be used instead, e.g.:
178 $ qemu-system-x86_64 -nographic -bios path/to/u-boot.rom
180 A specific CPU can be specified via the '-cpu' parameter but please make
181 sure the specified CPU supports 64-bit like '-cpu core2duo'. Conversely
182 '-cpu pentium' won't work for obvious reasons that the processor only
185 Note 64-bit support is very preliminary at this point. Lots of features
186 are missing in the 64-bit world. One notable feature is the VGA console
187 support which is currently missing, so that you must specify '-nographic'
188 to get 64-bit U-Boot up and running.
192 Modern CPUs usually require a special bit stream called microcode [8] to be
193 loaded on the processor after power up in order to function properly. U-Boot
194 has already integrated these as hex dumps in the source tree.
198 On a multicore system, U-Boot is executed on the bootstrap processor (BSP).
199 Additional application processors (AP) can be brought up by U-Boot. In order to
200 have an SMP kernel to discover all of the available processors, U-Boot needs to
201 prepare configuration tables which contain the multi-CPUs information before
202 loading the OS kernel. Currently U-Boot supports generating two types of tables
203 for SMP, called Simple Firmware Interface (SFI) [9] and Multi-Processor (MP)
204 [10] tables. The writing of these two tables are controlled by two Kconfig
205 options GENERATE_SFI_TABLE and GENERATE_MP_TABLE.
209 x86 has been converted to use driver model for serial, GPIO, SPI, SPI flash,
210 keyboard, real-time clock, USB. Video is in progress.
214 x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to
215 be turned on. Not every device on the board is configured via device tree, but
216 more and more devices will be added as time goes by. Check out the directory
217 arch/x86/dts/ for these device tree source files.
221 In keeping with the U-Boot philosophy of providing functions to check and
222 adjust internal settings, there are several x86-specific commands that may be
225 fsp - Display information about Intel Firmware Support Package (FSP).
226 This is only available on platforms which use FSP, mostly Atom.
227 iod - Display I/O memory
228 iow - Write I/O memory
229 mtrr - List and set the Memory Type Range Registers (MTRR). These are used to
230 tell the CPU whether memory is cacheable and if so the cache write
231 mode to use. U-Boot sets up some reasonable values but you can
232 adjust then with this command.
236 As an example of how to set up your boot flow with U-Boot, here are
237 instructions for starting Ubuntu from U-Boot. These instructions have been
238 tested on Minnowboard MAX with a SATA drive but are equally applicable on
239 other platforms and other media. There are really only four steps and it's a
240 very simple script, but a more detailed explanation is provided here for
243 Note: It is possible to set up U-Boot to boot automatically using syslinux.
244 It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the
245 GUID. If you figure these out, please post patches to this README.
247 Firstly, you will need Ubuntu installed on an available disk. It should be
248 possible to make U-Boot start a USB start-up disk but for now let's assume
249 that you used another boot loader to install Ubuntu.
251 Use the U-Boot command line to find the UUID of the partition you want to
252 boot. For example our disk is SCSI device 0:
256 Partition Map for SCSI device 0 -- Partition Type: EFI
258 Part Start LBA End LBA Name
262 1 0x00000800 0x001007ff ""
263 attrs: 0x0000000000000000
264 type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b
265 guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c
266 2 0x00100800 0x037d8fff ""
267 attrs: 0x0000000000000000
268 type: 0fc63daf-8483-4772-8e79-3d69d8477de4
269 guid: 965c59ee-1822-4326-90d2-b02446050059
270 3 0x037d9000 0x03ba27ff ""
271 attrs: 0x0000000000000000
272 type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f
273 guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17
276 This shows that your SCSI disk has three partitions. The really long hex
277 strings are called Globally Unique Identifiers (GUIDs). You can look up the
278 'type' ones here [11]. On this disk the first partition is for EFI and is in
279 VFAT format (DOS/Windows):
287 Partition 2 is 'Linux filesystem data' so that will be our root disk. It is
293 <DIR> 16384 lost+found
316 <SYM> 33 initrd.img.old
319 and if you look in the /boot directory you will see the kernel:
321 => ext2ls scsi 0:2 /boot
326 3381262 System.map-3.13.0-32-generic
327 1162712 abi-3.13.0-32-generic
328 165611 config-3.13.0-32-generic
329 176500 memtest86+.bin
330 178176 memtest86+.elf
331 178680 memtest86+_multiboot.bin
332 5798112 vmlinuz-3.13.0-32-generic
333 165762 config-3.13.0-58-generic
334 1165129 abi-3.13.0-58-generic
335 5823136 vmlinuz-3.13.0-58-generic
336 19215259 initrd.img-3.13.0-58-generic
337 3391763 System.map-3.13.0-58-generic
338 5825048 vmlinuz-3.13.0-58-generic.efi.signed
339 28304443 initrd.img-3.13.0-32-generic
342 The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of
343 self-extracting compressed file mixed with some 'setup' configuration data.
344 Despite its size (uncompressed it is >10MB) this only includes a basic set of
345 device drivers, enough to boot on most hardware types.
347 The 'initrd' files contain a RAM disk. This is something that can be loaded
348 into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots
349 of drivers for whatever hardware you might have. It is loaded before the
350 real root disk is accessed.
352 The numbers after the end of each file are the version. Here it is Linux
353 version 3.13. You can find the source code for this in the Linux tree with
354 the tag v3.13. The '.0' allows for additional Linux releases to fix problems,
355 but normally this is not needed. The '-58' is used by Ubuntu. Each time they
356 release a new kernel they increment this number. New Ubuntu versions might
357 include kernel patches to fix reported bugs. Stable kernels can exist for
358 some years so this number can get quite high.
360 The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own
361 secure boot mechanism - see [12] [13] and cannot read .efi files at present.
363 To boot Ubuntu from U-Boot the steps are as follows:
365 1. Set up the boot arguments. Use the GUID for the partition you want to
368 => setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro
370 Here root= tells Linux the location of its root disk. The disk is specified
371 by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory'
372 containing all the GUIDs Linux has found. When it starts up, there will be a
373 file in that directory with this name in it. It is also possible to use a
374 device name here, see later.
376 2. Load the kernel. Since it is an ext2/4 filesystem we can do:
378 => ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic
380 The address 30000000 is arbitrary, but there seem to be problems with using
381 small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into
382 the start of RAM (which is at 0 on x86).
384 3. Load the ramdisk (to 64MB):
386 => ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic
388 4. Start up the kernel. We need to know the size of the ramdisk, but can use
389 a variable for that. U-Boot sets 'filesize' to the size of the last file it
392 => zboot 03000000 0 04000000 ${filesize}
394 Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is
395 quite verbose when it boots a kernel. You should see these messages from
399 Setup Size = 0x00004400
400 Magic signature found
401 Using boot protocol version 2.0c
402 Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015
403 Building boot_params at 0x00090000
404 Loading bzImage at address 100000 (5805728 bytes)
405 Magic signature found
406 Initial RAM disk at linear address 0x04000000, size 19215259 bytes
407 Kernel command line: "root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro"
411 U-Boot prints out some bootstage timing. This is more useful if you put the
412 above commands into a script since then it will be faster.
414 Timer summary in microseconds:
417 241,535 241,535 board_init_r
418 2,421,611 2,180,076 id=64
420 2,428,215 6,425 main_loop
421 48,860,584 46,432,369 start_kernel
425 1,422,704 vesa display
427 Now the kernel actually starts: (if you want to examine kernel boot up message
428 on the serial console, append "console=ttyS0,115200" to the kernel command line)
430 [ 0.000000] Initializing cgroup subsys cpuset
431 [ 0.000000] Initializing cgroup subsys cpu
432 [ 0.000000] Initializing cgroup subsys cpuacct
433 [ 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)
434 [ 0.000000] Command line: root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro console=ttyS0,115200
436 It continues for a long time. Along the way you will see it pick up your
439 [ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff]
441 [ 0.788540] Trying to unpack rootfs image as initramfs...
442 [ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000)
445 Later it actually starts using it:
447 Begin: Running /scripts/local-premount ... done.
449 You should also see your boot disk turn up:
451 [ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5
452 [ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB)
453 [ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0
454 [ 4.381859] sd 1:0:0:0: [sda] Write Protect is off
455 [ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
456 [ 4.399535] sda: sda1 sda2 sda3
458 Linux has found the three partitions (sda1-3). Mercifully it doesn't print out
459 the GUIDs. In step 1 above we could have used:
461 setenv bootargs root=/dev/sda2 ro
463 instead of the GUID. However if you add another drive to your board the
464 numbering may change whereas the GUIDs will not. So if your boot partition
465 becomes sdb2, it will still boot. For embedded systems where you just want to
466 boot the first disk, you have that option.
468 The last thing you will see on the console is mention of plymouth (which
469 displays the Ubuntu start-up screen) and a lot of 'Starting' messages:
471 * Starting Mount filesystems on boot [ OK ]
473 After a pause you should see a login screen on your display and you are done.
475 If you want to put this in a script you can use something like this:
477 setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro
478 setenv boot zboot 03000000 0 04000000 \${filesize}
479 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"
482 The \ is to tell the shell not to evaluate ${filesize} as part of the setenv
485 You can also bake this behaviour into your build by hard-coding the
486 environment variables if you add this to minnowmax.h:
488 #undef CONFIG_BOOTCOMMAND
489 #define CONFIG_BOOTCOMMAND \
490 "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \
491 "ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \
494 #undef CONFIG_EXTRA_ENV_SETTINGS
495 #define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}"
497 and change CONFIG_BOOTARGS value in configs/minnowmax_defconfig to:
499 CONFIG_BOOTARGS="root=/dev/sda2 ro"
503 SeaBIOS [14] is an open source implementation of a 16-bit x86 BIOS. It can run
504 in an emulator or natively on x86 hardware with the use of U-Boot. With its
505 help, we can boot some OSes that require 16-bit BIOS services like Windows/DOS.
507 As U-Boot, we have to manually create a table where SeaBIOS gets various system
508 information (eg: E820) from. The table unfortunately has to follow the coreboot
509 table format as SeaBIOS currently supports booting as a coreboot payload.
511 To support loading SeaBIOS, U-Boot should be built with CONFIG_SEABIOS on.
512 Booting SeaBIOS is done via U-Boot's bootelf command, like below:
514 => tftp bios.bin.elf;bootelf
516 TFTP from server 10.10.0.100; our IP address is 10.10.0.108
518 Bytes transferred = 122124 (1dd0c hex)
519 ## Starting application at 0x000ff06e ...
520 SeaBIOS (version rel-1.9.0)
523 bios.bin.elf is the SeaBIOS image built from SeaBIOS source tree.
524 Make sure it is built as follows:
528 Inside the "General Features" menu, select "Build for coreboot" as the
529 "Build Target". Inside the "Debugging" menu, turn on "Serial port debugging"
530 so that we can see something as soon as SeaBIOS boots. Leave other options
531 as in their default state. Then,
535 Total size: 121888 Fixed: 66496 Free: 9184 (used 93.0% of 128KiB rom)
536 Creating out/bios.bin.elf
538 Currently this is tested on QEMU x86 target with U-Boot chain-loading SeaBIOS
539 to install/boot a Windows XP OS (below for example command to install Windows).
541 # Create a 10G disk.img as the virtual hard disk
542 $ qemu-img create -f qcow2 disk.img 10G
544 # Install a Windows XP OS from an ISO image 'winxp.iso'
545 $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -cdrom winxp.iso -smp 2 -m 512
547 # Boot a Windows XP OS installed on the virutal hard disk
548 $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -smp 2 -m 512
550 This is also tested on Intel Crown Bay board with a PCIe graphics card, booting
551 SeaBIOS then chain-loading a GRUB on a USB drive, then Linux kernel finally.
553 If you are using Intel Integrated Graphics Device (IGD) as the primary display
554 device on your board, SeaBIOS needs to be patched manually to get its VGA ROM
555 loaded and run by SeaBIOS. SeaBIOS locates VGA ROM via the PCI expansion ROM
556 register, but IGD device does not have its VGA ROM mapped by this register.
557 Its VGA ROM is packaged as part of u-boot.rom at a configurable flash address
558 which is unknown to SeaBIOS. An example patch is needed for SeaBIOS below:
560 diff --git a/src/optionroms.c b/src/optionroms.c
561 index 65f7fe0..c7b6f5e 100644
562 --- a/src/optionroms.c
563 +++ b/src/optionroms.c
564 @@ -324,6 +324,8 @@ init_pcirom(struct pci_device *pci, int isvga, u64 *sources)
565 rom = deploy_romfile(file);
566 else if (RunPCIroms > 1 || (RunPCIroms == 1 && isvga))
567 rom = map_pcirom(pci);
568 + if (pci->bdf == pci_to_bdf(0, 2, 0))
569 + rom = (struct rom_header *)0xfff90000;
574 Note: the patch above expects IGD device is at PCI b.d.f 0.2.0 and its VGA ROM
575 is at 0xfff90000 which corresponds to CONFIG_VGA_BIOS_ADDR on Minnowboard MAX.
576 Change these two accordingly if this is not the case on your board.
580 These notes are for those who want to port U-Boot to a new x86 platform.
582 Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment.
583 The Dediprog em100 can be used on Linux. The em100 tool is available here:
585 http://review.coreboot.org/p/em100.git
587 On Minnowboard Max the following command line can be used:
589 sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r
591 A suitable clip for connecting over the SPI flash chip is here:
593 http://www.dediprog.com/pd/programmer-accessories/EM-TC-8
595 This allows you to override the SPI flash contents for development purposes.
596 Typically you can write to the em100 in around 1200ms, considerably faster
597 than programming the real flash device each time. The only important
598 limitation of the em100 is that it only supports SPI bus speeds up to 20MHz.
599 This means that images must be set to boot with that speed. This is an
600 Intel-specific feature - e.g. tools/ifttool has an option to set the SPI
601 speed in the SPI descriptor region.
603 If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly
604 easy to fit it in. You can follow the Minnowboard Max implementation, for
605 example. Hopefully you will just need to create new files similar to those
606 in arch/x86/cpu/baytrail which provide Bay Trail support.
608 If you are not using an FSP you have more freedom and more responsibility.
609 The ivybridge support works this way, although it still uses a ROM for
610 graphics and still has binary blobs containing Intel code. You should aim to
611 support all important peripherals on your platform including video and storage.
612 Use the device tree for configuration where possible.
614 For the microcode you can create a suitable device tree file using the
617 ./tools/microcode-tool -d microcode.dat -m <model> create
619 or if you only have header files and not the full Intel microcode.dat database:
621 ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \
622 -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h \
625 These are written to arch/x86/dts/microcode/ by default.
627 Note that it is possible to just add the micrcode for your CPU if you know its
628 model. U-Boot prints this information when it starts
630 CPU: x86_64, vendor Intel, device 30673h
632 so here we can use the M0130673322 file.
634 If you platform can display POST codes on two little 7-segment displays on
635 the board, then you can use post_code() calls from C or assembler to monitor
636 boot progress. This can be good for debugging.
638 If not, you can try to get serial working as early as possible. The early
639 debug serial port may be useful here. See setup_internal_uart() for an example.
641 During the U-Boot porting, one of the important steps is to write correct PIRQ
642 routing information in the board device tree. Without it, device drivers in the
643 Linux kernel won't function correctly due to interrupt is not working. Please
644 refer to U-Boot doc [15] for the device tree bindings of Intel interrupt router.
645 Here we have more details on the intel,pirq-routing property below.
647 intel,pirq-routing = <
648 PCI_BDF(0, 2, 0) INTA PIRQA
652 As you see each entry has 3 cells. For the first one, we need describe all pci
653 devices mounted on the board. For SoC devices, normally there is a chapter on
654 the chipset datasheet which lists all the available PCI devices. For example on
655 Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we
656 can get the interrupt pin either from datasheet or hardware via U-Boot shell.
657 The reliable source is the hardware as sometimes chipset datasheet is not 100%
658 up-to-date. Type 'pci header' plus the device's pci bus/device/function number
659 from U-Boot shell below.
665 interrupt line = 0x09
669 It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin
670 register. Repeat this until you get interrupt pins for all the devices. The last
671 cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel
672 chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This
673 can be changed by registers in LPC bridge. So far Intel FSP does not touch those
674 registers so we can write down the PIRQ according to the default mapping rule.
676 Once we get the PIRQ routing information in the device tree, the interrupt
677 allocation and assignment will be done by U-Boot automatically. Now you can
678 enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and
679 CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC.
681 This script might be useful. If you feed it the output of 'pci long' from
682 U-Boot then it will generate a device tree fragment with the interrupt
683 configuration for each device (note it needs gawk 4.0.0):
685 $ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \
686 /interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \
687 {patsplit(device, bdf, "[0-9a-f]+"); \
688 printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \
689 strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}'
692 PCI_BDF(0, 2, 0) INTA PIRQA
693 PCI_BDF(0, 3, 0) INTA PIRQA
699 Quark-specific considerations:
701 To port U-Boot to other boards based on the Intel Quark SoC, a few things need
702 to be taken care of. The first important part is the Memory Reference Code (MRC)
703 parameters. Quark MRC supports memory-down configuration only. All these MRC
704 parameters are supplied via the board device tree. To get started, first copy
705 the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then
706 change these values by consulting board manuals or your hardware vendor.
707 Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h.
708 The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports,
709 but by default they are held in reset after power on. In U-Boot, PCIe
710 initialization is properly handled as per Quark's firmware writer guide.
711 In your board support codes, you need provide two routines to aid PCIe
712 initialization, which are board_assert_perst() and board_deassert_perst().
713 The two routines need implement a board-specific mechanism to assert/deassert
714 PCIe PERST# pin. Care must be taken that in those routines that any APIs that
715 may trigger PCI enumeration process are strictly forbidden, as any access to
716 PCIe root port's configuration registers will cause system hang while it is
717 held in reset. For more details, check how they are implemented by the Intel
718 Galileo board support codes in board/intel/galileo/galileo.c.
722 See scripts/coreboot.sed which can assist with porting coreboot code into
723 U-Boot drivers. It will not resolve all build errors, but will perform common
724 transformations. Remember to add attribution to coreboot for new files added
725 to U-Boot. This should go at the top of each file and list the coreboot
726 filename where the code originated.
728 Debugging ACPI issues with Windows:
730 Windows might cache system information and only detect ACPI changes if you
731 modify the ACPI table versions. So tweak them liberally when debugging ACPI
736 Advanced Configuration and Power Interface (ACPI) [16] aims to establish
737 industry-standard interfaces enabling OS-directed configuration, power
738 management, and thermal management of mobile, desktop, and server platforms.
740 Linux can boot without ACPI with "acpi=off" command line parameter, but
741 with ACPI the kernel gains the capabilities to handle power management.
742 For Windows, ACPI is a must-have firmware feature since Windows Vista.
743 CONFIG_GENERATE_ACPI_TABLE is the config option to turn on ACPI support in
744 U-Boot. This requires Intel ACPI compiler to be installed on your host to
745 compile ACPI DSDT table written in ASL format to AML format. You can get
746 the compiler via "apt-get install iasl" if you are on Ubuntu or download
747 the source from [17] to compile one by yourself.
749 Current ACPI support in U-Boot is basically complete. More optional features
750 can be added in the future. The status as of today is:
752 * Support generating RSDT, XSDT, FACS, FADT, MADT, MCFG tables.
753 * Support one static DSDT table only, compiled by Intel ACPI compiler.
754 * Support S0/S3/S4/S5, reboot and shutdown from OS.
755 * Support booting a pre-installed Ubuntu distribution via 'zboot' command.
756 * Support installing and booting Ubuntu 14.04 (or above) from U-Boot with
757 the help of SeaBIOS using legacy interface (non-UEFI mode).
758 * Support installing and booting Windows 8.1/10 from U-Boot with the help
759 of SeaBIOS using legacy interface (non-UEFI mode).
760 * Support ACPI interrupts with SCI only.
762 Features that are optional:
763 * Dynamic AML bytecodes insertion at run-time. We may need this to support
764 SSDT table generation and DSDT fix up.
765 * SMI support. Since U-Boot is a modern bootloader, we don't want to bring
766 those legacy stuff into U-Boot. ACPI spec allows a system that does not
767 support SMI (a legacy-free system).
769 ACPI was initially enabled on BayTrail based boards. Testing was done by booting
770 a pre-installed Ubuntu 14.04 from a SATA drive. Installing Ubuntu 14.04 and
771 Windows 8.1/10 to a SATA drive and booting from there is also tested. Most
772 devices seem to work correctly and the board can respond a reboot/shutdown
775 For other platform boards, ACPI support status can be checked by examining their
776 board defconfig files to see if CONFIG_GENERATE_ACPI_TABLE is set to y.
778 The S3 sleeping state is a low wake latency sleeping state defined by ACPI
779 spec where all system context is lost except system memory. To test S3 resume
780 with a Linux kernel, simply run "echo mem > /sys/power/state" and kernel will
781 put the board to S3 state where the power is off. So when the power button is
782 pressed again, U-Boot runs as it does in cold boot and detects the sleeping
783 state via ACPI register to see if it is S3, if yes it means we are waking up.
784 U-Boot is responsible for restoring the machine state as it is before sleep.
785 When everything is done, U-Boot finds out the wakeup vector provided by OSes
786 and jump there. To determine whether ACPI S3 resume is supported, check to
787 see if CONFIG_HAVE_ACPI_RESUME is set for that specific board.
789 Note for testing S3 resume with Windows, correct graphics driver must be
790 installed for your platform, otherwise you won't find "Sleep" option in
791 the "Power" submenu from the Windows start menu.
795 U-Boot supports booting as a 32-bit or 64-bit EFI payload, e.g. with UEFI.
796 This is enabled with CONFIG_EFI_STUB to boot from both 32-bit and 64-bit
797 UEFI BIOS. U-Boot can also run as an EFI application, with CONFIG_EFI_APP.
798 The CONFIG_EFI_LOADER option, where U-Boot provides an EFI environment to
799 the kernel (i.e. replaces UEFI completely but provides the same EFI run-time
800 services) is supported too. For example, we can even use 'bootefi' command
801 to load a 'u-boot-payload.efi', see below test logs on QEMU.
803 => load ide 0 3000000 u-boot-payload.efi
804 489787 bytes read in 138 ms (3.4 MiB/s)
806 Scanning disk ide.blk#0...
808 WARNING: booting without device tree
809 ## Starting EFI application at 03000000 ...
813 U-Boot 2018.07-rc2 (Jun 23 2018 - 17:12:58 +0800)
815 CPU: x86_64, vendor AMD, device 663h
819 Model: EFI x86 Payload
820 Net: e1000: 52:54:00:12:34:56
822 Warning: e1000#0 using MAC address from ROM
825 Hit any key to stop autoboot: 0
827 See README.u-boot_on_efi and README.uefi for details of EFI support in U-Boot.
832 - Chrome OS verified boot
836 [1] http://www.coreboot.org
837 [2] http://www.qemu.org
838 [3] http://www.coreboot.org/~stepan/pci8086,0166.rom
839 [4] http://www.intel.com/content/www/us/en/embedded/design-tools/evaluation-platforms/atom-e660-eg20t-development-kit.html
840 [5] http://www.intel.com/fsp
841 [6] http://www.intel.com/content/www/us/en/secure/intelligent-systems/privileged/e6xx-35-b1-cmc22211.html
842 [7] http://www.ami.com/products/bios-uefi-tools-and-utilities/bios-uefi-utilities/
843 [8] http://en.wikipedia.org/wiki/Microcode
844 [9] http://simplefirmware.org
845 [10] http://www.intel.com/design/archives/processors/pro/docs/242016.htm
846 [11] https://en.wikipedia.org/wiki/GUID_Partition_Table
847 [12] http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf
848 [13] http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf
849 [14] http://www.seabios.org/SeaBIOS
850 [15] doc/device-tree-bindings/misc/intel,irq-router.txt
851 [16] http://www.acpi.info
852 [17] https://www.acpica.org/downloads