1 .. SPDX-License-Identifier: GPL-2.0+
2 .. Copyright (C) 2014, Simon Glass <sjg@chromium.org>
3 .. Copyright (C) 2014, Bin Meng <bmeng.cn@gmail.com>
8 This document describes the information about U-Boot running on x86 targets,
9 including supported boards, build instructions, todo list, etc.
13 U-Boot supports running as a `coreboot`_ payload on x86. So far only Link
14 (Chromebook Pixel) and `QEMU`_ x86 targets have been tested, but it should
15 work with minimal adjustments on other x86 boards since coreboot deals with
16 most of the low-level details.
18 U-Boot is a main bootloader on Intel Edison board.
20 U-Boot also supports booting directly from x86 reset vector, without coreboot.
21 In this case, known as bare mode, from the fact that it runs on the
22 'bare metal', U-Boot acts like a BIOS replacement. The following platforms
27 - Congatec QEVAL 2.0 & conga-QA3/E3845
31 - Link (Chromebook Pixel)
33 - Samus (Chromebook Pixel 2015)
34 - QEMU x86 (32-bit & 64-bit)
36 As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit
37 Linux kernel as part of a FIT image. It also supports a compressed zImage.
38 U-Boot supports loading an x86 VxWorks kernel. Please check README.vxworks
41 Build Instructions for U-Boot as BIOS replacement (bare mode)
42 -------------------------------------------------------------
43 Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a
44 little bit tricky, as generally it requires several binary blobs which are not
45 shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build may
46 print some warnings if required binary blobs (e.g.: FSP) are not present.
50 Modern CPUs usually require a special bit stream called `microcode`_ to be
51 loaded on the processor after power up in order to function properly. U-Boot
52 has already integrated these as hex dumps in the source tree.
56 On a multicore system, U-Boot is executed on the bootstrap processor (BSP).
57 Additional application processors (AP) can be brought up by U-Boot. In order to
58 have an SMP kernel to discover all of the available processors, U-Boot needs to
59 prepare configuration tables which contain the multi-CPUs information before
60 loading the OS kernel. Currently U-Boot supports generating two types of tables
61 for SMP, called Simple Firmware Interface (`SFI`_) and Multi-Processor (`MP`_)
62 tables. The writing of these two tables are controlled by two Kconfig
63 options GENERATE_SFI_TABLE and GENERATE_MP_TABLE.
67 x86 has been converted to use driver model for serial, GPIO, SPI, SPI flash,
68 keyboard, real-time clock, USB. Video is in progress.
72 x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to
73 be turned on. Not every device on the board is configured via device tree, but
74 more and more devices will be added as time goes by. Check out the directory
75 arch/x86/dts/ for these device tree source files.
79 In keeping with the U-Boot philosophy of providing functions to check and
80 adjust internal settings, there are several x86-specific commands that may be
84 Display information about Intel Firmware Support Package (FSP).
85 This is only available on platforms which use FSP, mostly Atom.
91 List and set the Memory Type Range Registers (MTRR). These are used to
92 tell the CPU whether memory is cacheable and if so the cache write
93 mode to use. U-Boot sets up some reasonable values but you can
94 adjust then with this command.
98 As an example of how to set up your boot flow with U-Boot, here are
99 instructions for starting Ubuntu from U-Boot. These instructions have been
100 tested on Minnowboard MAX with a SATA drive but are equally applicable on
101 other platforms and other media. There are really only four steps and it's a
102 very simple script, but a more detailed explanation is provided here for
105 Note: It is possible to set up U-Boot to boot automatically using syslinux.
106 It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the
107 GUID. If you figure these out, please post patches to this README.
109 Firstly, you will need Ubuntu installed on an available disk. It should be
110 possible to make U-Boot start a USB start-up disk but for now let's assume
111 that you used another boot loader to install Ubuntu.
113 Use the U-Boot command line to find the UUID of the partition you want to
114 boot. For example our disk is SCSI device 0::
118 Partition Map for SCSI device 0 -- Partition Type: EFI
120 Part Start LBA End LBA Name
124 1 0x00000800 0x001007ff ""
125 attrs: 0x0000000000000000
126 type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b
127 guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c
128 2 0x00100800 0x037d8fff ""
129 attrs: 0x0000000000000000
130 type: 0fc63daf-8483-4772-8e79-3d69d8477de4
131 guid: 965c59ee-1822-4326-90d2-b02446050059
132 3 0x037d9000 0x03ba27ff ""
133 attrs: 0x0000000000000000
134 type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f
135 guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17
138 This shows that your SCSI disk has three partitions. The really long hex
139 strings are called Globally Unique Identifiers (GUIDs). You can look up the
140 'type' ones `here`_. On this disk the first partition is for EFI and is in
141 VFAT format (DOS/Windows)::
149 Partition 2 is 'Linux filesystem data' so that will be our root disk. It is
155 <DIR> 16384 lost+found
178 <SYM> 33 initrd.img.old
181 and if you look in the /boot directory you will see the kernel::
183 => ext2ls scsi 0:2 /boot
188 3381262 System.map-3.13.0-32-generic
189 1162712 abi-3.13.0-32-generic
190 165611 config-3.13.0-32-generic
191 176500 memtest86+.bin
192 178176 memtest86+.elf
193 178680 memtest86+_multiboot.bin
194 5798112 vmlinuz-3.13.0-32-generic
195 165762 config-3.13.0-58-generic
196 1165129 abi-3.13.0-58-generic
197 5823136 vmlinuz-3.13.0-58-generic
198 19215259 initrd.img-3.13.0-58-generic
199 3391763 System.map-3.13.0-58-generic
200 5825048 vmlinuz-3.13.0-58-generic.efi.signed
201 28304443 initrd.img-3.13.0-32-generic
204 The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of
205 self-extracting compressed file mixed with some 'setup' configuration data.
206 Despite its size (uncompressed it is >10MB) this only includes a basic set of
207 device drivers, enough to boot on most hardware types.
209 The 'initrd' files contain a RAM disk. This is something that can be loaded
210 into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots
211 of drivers for whatever hardware you might have. It is loaded before the
212 real root disk is accessed.
214 The numbers after the end of each file are the version. Here it is Linux
215 version 3.13. You can find the source code for this in the Linux tree with
216 the tag v3.13. The '.0' allows for additional Linux releases to fix problems,
217 but normally this is not needed. The '-58' is used by Ubuntu. Each time they
218 release a new kernel they increment this number. New Ubuntu versions might
219 include kernel patches to fix reported bugs. Stable kernels can exist for
220 some years so this number can get quite high.
222 The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own
223 secure boot mechanism - see `this`_ & `that`_. It cannot read .efi files
226 To boot Ubuntu from U-Boot the steps are as follows:
228 1. Set up the boot arguments. Use the GUID for the partition you want to boot::
230 => setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro
232 Here root= tells Linux the location of its root disk. The disk is specified
233 by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory'
234 containing all the GUIDs Linux has found. When it starts up, there will be a
235 file in that directory with this name in it. It is also possible to use a
236 device name here, see later.
238 2. Load the kernel. Since it is an ext2/4 filesystem we can do::
240 => ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic
242 The address 30000000 is arbitrary, but there seem to be problems with using
243 small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into
244 the start of RAM (which is at 0 on x86).
246 3. Load the ramdisk (to 64MB)::
248 => ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic
250 4. Start up the kernel. We need to know the size of the ramdisk, but can use
251 a variable for that. U-Boot sets 'filesize' to the size of the last file it
254 => zboot 03000000 0 04000000 ${filesize}
256 Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is
257 quite verbose when it boots a kernel. You should see these messages from
261 Setup Size = 0x00004400
262 Magic signature found
263 Using boot protocol version 2.0c
264 Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015
265 Building boot_params at 0x00090000
266 Loading bzImage at address 100000 (5805728 bytes)
267 Magic signature found
268 Initial RAM disk at linear address 0x04000000, size 19215259 bytes
269 Kernel command line: "root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro"
273 U-Boot prints out some bootstage timing. This is more useful if you put the
274 above commands into a script since then it will be faster::
276 Timer summary in microseconds:
279 241,535 241,535 board_init_r
280 2,421,611 2,180,076 id=64
282 2,428,215 6,425 main_loop
283 48,860,584 46,432,369 start_kernel
287 1,422,704 vesa display
289 Now the kernel actually starts (if you want to examine kernel boot up message on
290 the serial console, append "console=ttyS0,115200" to the kernel command line)::
292 [ 0.000000] Initializing cgroup subsys cpuset
293 [ 0.000000] Initializing cgroup subsys cpu
294 [ 0.000000] Initializing cgroup subsys cpuacct
295 [ 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)
296 [ 0.000000] Command line: root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro console=ttyS0,115200
298 It continues for a long time. Along the way you will see it pick up your
301 [ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff]
303 [ 0.788540] Trying to unpack rootfs image as initramfs...
304 [ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000)
307 Later it actually starts using it::
309 Begin: Running /scripts/local-premount ... done.
311 You should also see your boot disk turn up::
313 [ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5
314 [ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB)
315 [ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0
316 [ 4.381859] sd 1:0:0:0: [sda] Write Protect is off
317 [ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
318 [ 4.399535] sda: sda1 sda2 sda3
320 Linux has found the three partitions (sda1-3). Mercifully it doesn't print out
321 the GUIDs. In step 1 above we could have used::
323 setenv bootargs root=/dev/sda2 ro
325 instead of the GUID. However if you add another drive to your board the
326 numbering may change whereas the GUIDs will not. So if your boot partition
327 becomes sdb2, it will still boot. For embedded systems where you just want to
328 boot the first disk, you have that option.
330 The last thing you will see on the console is mention of plymouth (which
331 displays the Ubuntu start-up screen) and a lot of 'Starting' messages::
333 * Starting Mount filesystems on boot [ OK ]
335 After a pause you should see a login screen on your display and you are done.
337 If you want to put this in a script you can use something like this::
339 setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro
340 setenv boot zboot 03000000 0 04000000 \${filesize}
341 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"
344 The \ is to tell the shell not to evaluate ${filesize} as part of the setenv
347 You can also bake this behaviour into your build by hard-coding the
348 environment variables if you add this to minnowmax.h:
352 #undef CONFIG_BOOTCOMMAND
353 #define CONFIG_BOOTCOMMAND \
354 "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \
355 "ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \
358 #undef CONFIG_EXTRA_ENV_SETTINGS
359 #define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}"
361 and change CONFIG_BOOTARGS value in configs/minnowmax_defconfig to::
363 CONFIG_BOOTARGS="root=/dev/sda2 ro"
367 `SeaBIOS`_ is an open source implementation of a 16-bit x86 BIOS. It can run
368 in an emulator or natively on x86 hardware with the use of U-Boot. With its
369 help, we can boot some OSes that require 16-bit BIOS services like Windows/DOS.
371 As U-Boot, we have to manually create a table where SeaBIOS gets various system
372 information (eg: E820) from. The table unfortunately has to follow the coreboot
373 table format as SeaBIOS currently supports booting as a coreboot payload.
375 To support loading SeaBIOS, U-Boot should be built with CONFIG_SEABIOS on.
376 Booting SeaBIOS is done via U-Boot's bootelf command, like below::
378 => tftp bios.bin.elf;bootelf
380 TFTP from server 10.10.0.100; our IP address is 10.10.0.108
382 Bytes transferred = 128748 (1f6ec hex)
383 ## Starting application at 0x000fd269 ...
384 SeaBIOS (version rel-1.14.0-0-g155821a)
387 bios.bin.elf is the SeaBIOS image built from SeaBIOS source tree. At the time
388 being, SeaBIOS release 1.14.0 has been tested. To build the SeaBIOS image::
390 $ echo -e 'CONFIG_COREBOOT=y\nCONFIG_COREBOOT_FLASH=n\nCONFIG_DEBUG_SERIAL=y\nCONFIG_DEBUG_COREBOOT=n' > .config
394 Total size: 128512 Fixed: 69216 Free: 2560 (used 98.0% of 128KiB rom)
395 Creating out/bios.bin.elf
397 Currently this is tested on QEMU x86 target with U-Boot chain-loading SeaBIOS
398 to install/boot a Windows XP OS (below for example command to install Windows).
402 # Create a 10G disk.img as the virtual hard disk
403 $ qemu-img create -f qcow2 disk.img 10G
405 # Install a Windows XP OS from an ISO image 'winxp.iso'
406 $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -cdrom winxp.iso -smp 2 -m 512
408 # Boot a Windows XP OS installed on the virutal hard disk
409 $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -smp 2 -m 512
411 This is also tested on Intel Crown Bay board with a PCIe graphics card, booting
412 SeaBIOS then chain-loading a GRUB on a USB drive, then Linux kernel finally.
414 If you are using Intel Integrated Graphics Device (IGD) as the primary display
415 device on your board, SeaBIOS needs to be patched manually to get its VGA ROM
416 loaded and run by SeaBIOS. SeaBIOS locates VGA ROM via the PCI expansion ROM
417 register, but IGD device does not have its VGA ROM mapped by this register.
418 Its VGA ROM is packaged as part of u-boot.rom at a configurable flash address
419 which is unknown to SeaBIOS. An example patch is needed for SeaBIOS below:
423 diff --git a/src/optionroms.c b/src/optionroms.c
424 index 65f7fe0..c7b6f5e 100644
425 --- a/src/optionroms.c
426 +++ b/src/optionroms.c
427 @@ -324,6 +324,8 @@ init_pcirom(struct pci_device *pci, int isvga, u64 *sources)
428 rom = deploy_romfile(file);
429 else if (RunPCIroms > 1 || (RunPCIroms == 1 && isvga))
430 rom = map_pcirom(pci);
431 + if (pci->bdf == pci_to_bdf(0, 2, 0))
432 + rom = (struct rom_header *)0xfff90000;
437 Note: the patch above expects IGD device is at PCI b.d.f 0.2.0 and its VGA ROM
438 is at 0xfff90000 which corresponds to CONFIG_VGA_BIOS_ADDR on Minnowboard MAX.
439 Change these two accordingly if this is not the case on your board.
443 These notes are for those who want to port U-Boot to a new x86 platform.
445 Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment.
446 The Dediprog em100 can be used on Linux.
448 The em100 tool is available here: http://review.coreboot.org/p/em100.git
450 On Minnowboard Max the following command line can be used::
452 sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r
454 A suitable clip for connecting over the SPI flash chip is here:
455 http://www.dediprog.com/pd/programmer-accessories/EM-TC-8.
457 This allows you to override the SPI flash contents for development purposes.
458 Typically you can write to the em100 in around 1200ms, considerably faster
459 than programming the real flash device each time. The only important
460 limitation of the em100 is that it only supports SPI bus speeds up to 20MHz.
461 This means that images must be set to boot with that speed. This is an
462 Intel-specific feature - e.g. tools/ifttool has an option to set the SPI
463 speed in the SPI descriptor region.
465 If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly
466 easy to fit it in. You can follow the Minnowboard Max implementation, for
467 example. Hopefully you will just need to create new files similar to those
468 in arch/x86/cpu/baytrail which provide Bay Trail support.
470 If you are not using an FSP you have more freedom and more responsibility.
471 The ivybridge support works this way, although it still uses a ROM for
472 graphics and still has binary blobs containing Intel code. You should aim to
473 support all important peripherals on your platform including video and storage.
474 Use the device tree for configuration where possible.
476 For the microcode you can create a suitable device tree file using the
479 ./tools/microcode-tool -d microcode.dat -m <model> create
481 or if you only have header files and not the full Intel microcode.dat database::
483 ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \
484 -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h -m all create
486 These are written to arch/x86/dts/microcode/ by default.
488 Note that it is possible to just add the micrcode for your CPU if you know its
489 model. U-Boot prints this information when it starts::
491 CPU: x86_64, vendor Intel, device 30673h
493 so here we can use the M0130673322 file.
495 If you platform can display POST codes on two little 7-segment displays on
496 the board, then you can use post_code() calls from C or assembler to monitor
497 boot progress. This can be good for debugging.
499 If not, you can try to get serial working as early as possible. The early
500 debug serial port may be useful here. See setup_internal_uart() for an example.
502 During the U-Boot porting, one of the important steps is to write correct PIRQ
503 routing information in the board device tree. Without it, device drivers in the
504 Linux kernel won't function correctly due to interrupt is not working. Please
505 refer to U-Boot `doc <doc/device-tree-bindings/misc/intel,irq-router.txt>`_ for
506 the device tree bindings of Intel interrupt router. Here we have more details
507 on the intel,pirq-routing property below.
511 intel,pirq-routing = <
512 PCI_BDF(0, 2, 0) INTA PIRQA
516 As you see each entry has 3 cells. For the first one, we need describe all pci
517 devices mounted on the board. For SoC devices, normally there is a chapter on
518 the chipset datasheet which lists all the available PCI devices. For example on
519 Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we
520 can get the interrupt pin either from datasheet or hardware via U-Boot shell.
521 The reliable source is the hardware as sometimes chipset datasheet is not 100%
522 up-to-date. Type 'pci header' plus the device's pci bus/device/function number
523 from U-Boot shell below::
529 interrupt line = 0x09
533 It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin
534 register. Repeat this until you get interrupt pins for all the devices. The last
535 cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel
536 chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This
537 can be changed by registers in LPC bridge. So far Intel FSP does not touch those
538 registers so we can write down the PIRQ according to the default mapping rule.
540 Once we get the PIRQ routing information in the device tree, the interrupt
541 allocation and assignment will be done by U-Boot automatically. Now you can
542 enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and
543 CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC.
545 This script might be useful. If you feed it the output of 'pci long' from
546 U-Boot then it will generate a device tree fragment with the interrupt
547 configuration for each device (note it needs gawk 4.0.0)::
549 $ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \
550 /interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \
551 {patsplit(device, bdf, "[0-9a-f]+"); \
552 printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \
553 strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}'
557 PCI_BDF(0, 2, 0) INTA PIRQA
558 PCI_BDF(0, 3, 0) INTA PIRQA
564 Quark-specific considerations
565 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
567 To port U-Boot to other boards based on the Intel Quark SoC, a few things need
568 to be taken care of. The first important part is the Memory Reference Code (MRC)
569 parameters. Quark MRC supports memory-down configuration only. All these MRC
570 parameters are supplied via the board device tree. To get started, first copy
571 the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then
572 change these values by consulting board manuals or your hardware vendor.
573 Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h.
574 The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports,
575 but by default they are held in reset after power on. In U-Boot, PCIe
576 initialization is properly handled as per Quark's firmware writer guide.
577 In your board support codes, you need provide two routines to aid PCIe
578 initialization, which are board_assert_perst() and board_deassert_perst().
579 The two routines need implement a board-specific mechanism to assert/deassert
580 PCIe PERST# pin. Care must be taken that in those routines that any APIs that
581 may trigger PCI enumeration process are strictly forbidden, as any access to
582 PCIe root port's configuration registers will cause system hang while it is
583 held in reset. For more details, check how they are implemented by the Intel
584 Galileo board support codes in board/intel/galileo/galileo.c.
589 See scripts/coreboot.sed which can assist with porting coreboot code into
590 U-Boot drivers. It will not resolve all build errors, but will perform common
591 transformations. Remember to add attribution to coreboot for new files added
592 to U-Boot. This should go at the top of each file and list the coreboot
593 filename where the code originated.
595 Debugging ACPI issues with Windows
596 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
598 Windows might cache system information and only detect ACPI changes if you
599 modify the ACPI table versions. So tweak them liberally when debugging ACPI
604 Advanced Configuration and Power Interface (`ACPI`_) aims to establish
605 industry-standard interfaces enabling OS-directed configuration, power
606 management, and thermal management of mobile, desktop, and server platforms.
608 Linux can boot without ACPI with "acpi=off" command line parameter, but
609 with ACPI the kernel gains the capabilities to handle power management.
610 For Windows, ACPI is a must-have firmware feature since Windows Vista.
611 CONFIG_GENERATE_ACPI_TABLE is the config option to turn on ACPI support in
612 U-Boot. This requires Intel ACPI compiler to be installed on your host to
613 compile ACPI DSDT table written in ASL format to AML format. You can get
614 the compiler via "apt-get install iasl" if you are on Ubuntu or download
615 the source from https://www.acpica.org/downloads to compile one by yourself.
617 Current ACPI support in U-Boot is basically complete. More optional features
618 can be added in the future. The status as of today is:
620 * Support generating RSDT, XSDT, FACS, FADT, MADT, MCFG tables.
621 * Support one static DSDT table only, compiled by Intel ACPI compiler.
622 * Support S0/S3/S4/S5, reboot and shutdown from OS.
623 * Support booting a pre-installed Ubuntu distribution via 'zboot' command.
624 * Support installing and booting Ubuntu 14.04 (or above) from U-Boot with
625 the help of SeaBIOS using legacy interface (non-UEFI mode).
626 * Support installing and booting Windows 8.1/10 from U-Boot with the help
627 of SeaBIOS using legacy interface (non-UEFI mode).
628 * Support ACPI interrupts with SCI only.
630 Features that are optional:
632 * Dynamic AML bytecodes insertion at run-time. We may need this to support
633 SSDT table generation and DSDT fix up.
634 * SMI support. Since U-Boot is a modern bootloader, we don't want to bring
635 those legacy stuff into U-Boot. ACPI spec allows a system that does not
636 support SMI (a legacy-free system).
638 ACPI was initially enabled on BayTrail based boards. Testing was done by booting
639 a pre-installed Ubuntu 14.04 from a SATA drive. Installing Ubuntu 14.04 and
640 Windows 8.1/10 to a SATA drive and booting from there is also tested. Most
641 devices seem to work correctly and the board can respond a reboot/shutdown
644 For other platform boards, ACPI support status can be checked by examining their
645 board defconfig files to see if CONFIG_GENERATE_ACPI_TABLE is set to y.
647 The S3 sleeping state is a low wake latency sleeping state defined by ACPI
648 spec where all system context is lost except system memory. To test S3 resume
649 with a Linux kernel, simply run "echo mem > /sys/power/state" and kernel will
650 put the board to S3 state where the power is off. So when the power button is
651 pressed again, U-Boot runs as it does in cold boot and detects the sleeping
652 state via ACPI register to see if it is S3, if yes it means we are waking up.
653 U-Boot is responsible for restoring the machine state as it is before sleep.
654 When everything is done, U-Boot finds out the wakeup vector provided by OSes
655 and jump there. To determine whether ACPI S3 resume is supported, check to
656 see if CONFIG_HAVE_ACPI_RESUME is set for that specific board.
658 Note for testing S3 resume with Windows, correct graphics driver must be
659 installed for your platform, otherwise you won't find "Sleep" option in
660 the "Power" submenu from the Windows start menu.
664 U-Boot supports booting as a 32-bit or 64-bit EFI payload, e.g. with UEFI.
665 This is enabled with CONFIG_EFI_STUB to boot from both 32-bit and 64-bit
666 UEFI BIOS. U-Boot can also run as an EFI application, with CONFIG_EFI_APP.
667 The CONFIG_EFI_LOADER option, where U-Boot provides an EFI environment to
668 the kernel (i.e. replaces UEFI completely but provides the same EFI run-time
669 services) is supported too. For example, we can even use 'bootefi' command
670 to load a 'u-boot-payload.efi', see below test logs on QEMU.
674 => load ide 0 3000000 u-boot-payload.efi
675 489787 bytes read in 138 ms (3.4 MiB/s)
677 Scanning disk ide.blk#0...
679 WARNING: booting without device tree
680 ## Starting EFI application at 03000000 ...
684 U-Boot 2018.07-rc2 (Jun 23 2018 - 17:12:58 +0800)
686 CPU: x86_64, vendor AMD, device 663h
690 Model: EFI x86 Payload
691 Net: e1000: 52:54:00:12:34:56
693 Warning: e1000#0 using MAC address from ROM
696 Hit any key to stop autoboot: 0
698 See :doc:`../develop/uefi/u-boot_on_efi` and :doc:`../develop/uefi/uefi` for
699 details of EFI support in U-Boot.
703 U-Boot can be chain-loaded from another bootloader, such as coreboot or
704 Slim Bootloader. Typically this is done by building for targets 'coreboot' or
707 For example, at present we have a 'coreboot' target but this runs very
708 different code from the bare-metal targets, such as coral. There is very little
709 in common between them.
711 It is useful to be able to boot the same U-Boot on a device, with or without a
712 first-stage bootloader. For example, with chromebook_coral, it is helpful for
713 testing to be able to boot the same U-Boot (complete with FSP) on bare metal
714 and from coreboot. It allows checking of things like CPU speed, comparing
715 registers, ACPI tables and the like.
717 To do this you can use ll_boot_init() in appropriate places to skip init that
718 has already been done by the previous stage. This works by setting a
719 GD_FLG_NO_LL_INIT flag when U-Boot detects that it is running from another
722 With this feature, you can build a bare-metal target and boot it from
723 coreboot, for example.
725 Note that this is a development feature only. It is not intended for use in
726 production environments. Also it is not currently part of the automated tests
727 so may break in the future.
732 To generate SMBIOS tables in U-Boot, for use by the OS, enable the
733 CONFIG_GENERATE_SMBIOS_TABLE option. The easiest way to provide the values to
734 use is via the device tree. For details see
735 device-tree-bindings/sysinfo/smbios.txt
740 - Chrome OS verified boot
742 .. _coreboot: http://www.coreboot.org
743 .. _QEMU: http://www.qemu.org
744 .. _microcode: http://en.wikipedia.org/wiki/Microcode
745 .. _SFI: http://simplefirmware.org
746 .. _MP: http://www.intel.com/design/archives/processors/pro/docs/242016.htm
747 .. _here: https://en.wikipedia.org/wiki/GUID_Partition_Table
748 .. _this: http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf
749 .. _that: http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf
750 .. _SeaBIOS: http://www.seabios.org/SeaBIOS
751 .. _ACPI: http://www.acpi.info