mirror of
https://github.com/AsahiLinux/u-boot
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Correctly reference uefi/uefi.rst and uefi/u-boot_on_efi.rst. Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de> Reviewed-by: Bin Meng <bmeng.cn@gmail.com> Tested-by: Bin Meng <bmeng.cn@gmail.com>
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ReStructuredText
729 lines
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ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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.. Copyright (C) 2014, Simon Glass <sjg@chromium.org>
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.. Copyright (C) 2014, Bin Meng <bmeng.cn@gmail.com>
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x86
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===
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This document describes the information about U-Boot running on x86 targets,
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including supported boards, build instructions, todo list, etc.
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Status
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------
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U-Boot supports running as a `coreboot`_ payload on x86. So far only Link
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(Chromebook Pixel) and `QEMU`_ x86 targets have been tested, but it should
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work with minimal adjustments on other x86 boards since coreboot deals with
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most of the low-level details.
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U-Boot is a main bootloader on Intel Edison board.
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U-Boot also supports booting directly from x86 reset vector, without coreboot.
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In this case, known as bare mode, from the fact that it runs on the
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'bare metal', U-Boot acts like a BIOS replacement. The following platforms
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are supported:
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- Bayley Bay CRB
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- Cherry Hill CRB
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- Congatec QEVAL 2.0 & conga-QA3/E3845
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- Cougar Canyon 2 CRB
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- Crown Bay CRB
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- Galileo
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- Link (Chromebook Pixel)
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- Minnowboard MAX
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- Samus (Chromebook Pixel 2015)
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- QEMU x86 (32-bit & 64-bit)
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As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit
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Linux kernel as part of a FIT image. It also supports a compressed zImage.
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U-Boot supports loading an x86 VxWorks kernel. Please check README.vxworks
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for more details.
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Build Instructions for U-Boot as BIOS replacement (bare mode)
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-------------------------------------------------------------
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Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a
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little bit tricky, as generally it requires several binary blobs which are not
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shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build is
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not turned on by default in the U-Boot source tree. Firstly, you need turn it
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on by enabling the ROM build either via an environment variable::
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$ export BUILD_ROM=y
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or via configuration::
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CONFIG_BUILD_ROM=y
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Both tell the Makefile to build u-boot.rom as a target.
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CPU Microcode
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-------------
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Modern CPUs usually require a special bit stream called `microcode`_ to be
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loaded on the processor after power up in order to function properly. U-Boot
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has already integrated these as hex dumps in the source tree.
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SMP Support
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-----------
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On a multicore system, U-Boot is executed on the bootstrap processor (BSP).
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Additional application processors (AP) can be brought up by U-Boot. In order to
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have an SMP kernel to discover all of the available processors, U-Boot needs to
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prepare configuration tables which contain the multi-CPUs information before
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loading the OS kernel. Currently U-Boot supports generating two types of tables
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for SMP, called Simple Firmware Interface (`SFI`_) and Multi-Processor (`MP`_)
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tables. The writing of these two tables are controlled by two Kconfig
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options GENERATE_SFI_TABLE and GENERATE_MP_TABLE.
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Driver Model
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------------
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x86 has been converted to use driver model for serial, GPIO, SPI, SPI flash,
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keyboard, real-time clock, USB. Video is in progress.
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Device Tree
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-----------
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x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to
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be turned on. Not every device on the board is configured via device tree, but
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more and more devices will be added as time goes by. Check out the directory
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arch/x86/dts/ for these device tree source files.
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Useful Commands
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---------------
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In keeping with the U-Boot philosophy of providing functions to check and
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adjust internal settings, there are several x86-specific commands that may be
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useful:
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fsp
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Display information about Intel Firmware Support Package (FSP).
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This is only available on platforms which use FSP, mostly Atom.
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iod
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Display I/O memory
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iow
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Write I/O memory
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mtrr
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List and set the Memory Type Range Registers (MTRR). These are used to
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tell the CPU whether memory is cacheable and if so the cache write
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mode to use. U-Boot sets up some reasonable values but you can
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adjust then with this command.
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Booting Ubuntu
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--------------
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As an example of how to set up your boot flow with U-Boot, here are
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instructions for starting Ubuntu from U-Boot. These instructions have been
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tested on Minnowboard MAX with a SATA drive but are equally applicable on
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other platforms and other media. There are really only four steps and it's a
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very simple script, but a more detailed explanation is provided here for
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completeness.
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Note: It is possible to set up U-Boot to boot automatically using syslinux.
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It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the
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GUID. If you figure these out, please post patches to this README.
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Firstly, you will need Ubuntu installed on an available disk. It should be
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possible to make U-Boot start a USB start-up disk but for now let's assume
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that you used another boot loader to install Ubuntu.
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Use the U-Boot command line to find the UUID of the partition you want to
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boot. For example our disk is SCSI device 0::
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=> part list scsi 0
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Partition Map for SCSI device 0 -- Partition Type: EFI
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Part Start LBA End LBA Name
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Attributes
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Type GUID
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Partition GUID
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1 0x00000800 0x001007ff ""
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attrs: 0x0000000000000000
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type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b
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guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c
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2 0x00100800 0x037d8fff ""
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attrs: 0x0000000000000000
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type: 0fc63daf-8483-4772-8e79-3d69d8477de4
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guid: 965c59ee-1822-4326-90d2-b02446050059
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3 0x037d9000 0x03ba27ff ""
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attrs: 0x0000000000000000
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type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f
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guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17
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=>
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This shows that your SCSI disk has three partitions. The really long hex
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strings are called Globally Unique Identifiers (GUIDs). You can look up the
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'type' ones `here`_. On this disk the first partition is for EFI and is in
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VFAT format (DOS/Windows)::
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=> fatls scsi 0:1
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efi/
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0 file(s), 1 dir(s)
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Partition 2 is 'Linux filesystem data' so that will be our root disk. It is
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in ext2 format::
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=> ext2ls scsi 0:2
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<DIR> 4096 .
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<DIR> 4096 ..
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<DIR> 16384 lost+found
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<DIR> 4096 boot
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<DIR> 12288 etc
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<DIR> 4096 media
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<DIR> 4096 bin
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<DIR> 4096 dev
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<DIR> 4096 home
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<DIR> 4096 lib
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<DIR> 4096 lib64
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<DIR> 4096 mnt
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<DIR> 4096 opt
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<DIR> 4096 proc
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<DIR> 4096 root
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<DIR> 4096 run
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<DIR> 12288 sbin
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<DIR> 4096 srv
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<DIR> 4096 sys
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<DIR> 4096 tmp
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<DIR> 4096 usr
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<DIR> 4096 var
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<SYM> 33 initrd.img
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<SYM> 30 vmlinuz
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<DIR> 4096 cdrom
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<SYM> 33 initrd.img.old
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=>
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and if you look in the /boot directory you will see the kernel::
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=> ext2ls scsi 0:2 /boot
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<DIR> 4096 .
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<DIR> 4096 ..
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<DIR> 4096 efi
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<DIR> 4096 grub
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3381262 System.map-3.13.0-32-generic
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1162712 abi-3.13.0-32-generic
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165611 config-3.13.0-32-generic
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176500 memtest86+.bin
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178176 memtest86+.elf
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178680 memtest86+_multiboot.bin
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5798112 vmlinuz-3.13.0-32-generic
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165762 config-3.13.0-58-generic
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1165129 abi-3.13.0-58-generic
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5823136 vmlinuz-3.13.0-58-generic
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19215259 initrd.img-3.13.0-58-generic
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3391763 System.map-3.13.0-58-generic
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5825048 vmlinuz-3.13.0-58-generic.efi.signed
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28304443 initrd.img-3.13.0-32-generic
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=>
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The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of
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self-extracting compressed file mixed with some 'setup' configuration data.
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Despite its size (uncompressed it is >10MB) this only includes a basic set of
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device drivers, enough to boot on most hardware types.
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The 'initrd' files contain a RAM disk. This is something that can be loaded
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into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots
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of drivers for whatever hardware you might have. It is loaded before the
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real root disk is accessed.
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The numbers after the end of each file are the version. Here it is Linux
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version 3.13. You can find the source code for this in the Linux tree with
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the tag v3.13. The '.0' allows for additional Linux releases to fix problems,
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but normally this is not needed. The '-58' is used by Ubuntu. Each time they
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release a new kernel they increment this number. New Ubuntu versions might
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include kernel patches to fix reported bugs. Stable kernels can exist for
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some years so this number can get quite high.
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The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own
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secure boot mechanism - see `this`_ & `that`_. It cannot read .efi files
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at present.
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To boot Ubuntu from U-Boot the steps are as follows:
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1. Set up the boot arguments. Use the GUID for the partition you want to boot::
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=> setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro
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Here root= tells Linux the location of its root disk. The disk is specified
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by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory'
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containing all the GUIDs Linux has found. When it starts up, there will be a
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file in that directory with this name in it. It is also possible to use a
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device name here, see later.
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2. Load the kernel. Since it is an ext2/4 filesystem we can do::
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=> ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic
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The address 30000000 is arbitrary, but there seem to be problems with using
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small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into
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the start of RAM (which is at 0 on x86).
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3. Load the ramdisk (to 64MB)::
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=> ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic
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4. Start up the kernel. We need to know the size of the ramdisk, but can use
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a variable for that. U-Boot sets 'filesize' to the size of the last file it
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loaded::
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=> zboot 03000000 0 04000000 ${filesize}
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Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is
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quite verbose when it boots a kernel. You should see these messages from
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U-Boot::
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Valid Boot Flag
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Setup Size = 0x00004400
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Magic signature found
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Using boot protocol version 2.0c
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Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015
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Building boot_params at 0x00090000
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Loading bzImage at address 100000 (5805728 bytes)
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Magic signature found
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Initial RAM disk at linear address 0x04000000, size 19215259 bytes
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Kernel command line: "root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro"
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Starting kernel ...
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U-Boot prints out some bootstage timing. This is more useful if you put the
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above commands into a script since then it will be faster::
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Timer summary in microseconds:
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Mark Elapsed Stage
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0 0 reset
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241,535 241,535 board_init_r
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2,421,611 2,180,076 id=64
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2,421,790 179 id=65
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2,428,215 6,425 main_loop
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48,860,584 46,432,369 start_kernel
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Accumulated time:
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240,329 ahci
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1,422,704 vesa display
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Now the kernel actually starts (if you want to examine kernel boot up message on
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the serial console, append "console=ttyS0,115200" to the kernel command line)::
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[ 0.000000] Initializing cgroup subsys cpuset
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[ 0.000000] Initializing cgroup subsys cpu
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[ 0.000000] Initializing cgroup subsys cpuacct
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[ 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)
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[ 0.000000] Command line: root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro console=ttyS0,115200
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It continues for a long time. Along the way you will see it pick up your
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ramdisk::
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[ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff]
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...
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[ 0.788540] Trying to unpack rootfs image as initramfs...
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[ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000)
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...
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Later it actually starts using it::
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Begin: Running /scripts/local-premount ... done.
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You should also see your boot disk turn up::
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[ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5
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[ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB)
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[ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0
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[ 4.381859] sd 1:0:0:0: [sda] Write Protect is off
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[ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
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[ 4.399535] sda: sda1 sda2 sda3
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Linux has found the three partitions (sda1-3). Mercifully it doesn't print out
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the GUIDs. In step 1 above we could have used::
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setenv bootargs root=/dev/sda2 ro
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instead of the GUID. However if you add another drive to your board the
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numbering may change whereas the GUIDs will not. So if your boot partition
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becomes sdb2, it will still boot. For embedded systems where you just want to
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boot the first disk, you have that option.
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The last thing you will see on the console is mention of plymouth (which
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displays the Ubuntu start-up screen) and a lot of 'Starting' messages::
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* Starting Mount filesystems on boot [ OK ]
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After a pause you should see a login screen on your display and you are done.
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If you want to put this in a script you can use something like this::
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setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro
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setenv boot zboot 03000000 0 04000000 \${filesize}
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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"
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saveenv
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The \ is to tell the shell not to evaluate ${filesize} as part of the setenv
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command.
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You can also bake this behaviour into your build by hard-coding the
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environment variables if you add this to minnowmax.h:
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.. code-block:: c
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#undef CONFIG_BOOTCOMMAND
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#define CONFIG_BOOTCOMMAND \
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"ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \
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"ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \
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"run boot"
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#undef CONFIG_EXTRA_ENV_SETTINGS
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#define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}"
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and change CONFIG_BOOTARGS value in configs/minnowmax_defconfig to::
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CONFIG_BOOTARGS="root=/dev/sda2 ro"
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Test with SeaBIOS
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-----------------
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`SeaBIOS`_ is an open source implementation of a 16-bit x86 BIOS. It can run
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in an emulator or natively on x86 hardware with the use of U-Boot. With its
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help, we can boot some OSes that require 16-bit BIOS services like Windows/DOS.
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As U-Boot, we have to manually create a table where SeaBIOS gets various system
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information (eg: E820) from. The table unfortunately has to follow the coreboot
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table format as SeaBIOS currently supports booting as a coreboot payload.
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To support loading SeaBIOS, U-Boot should be built with CONFIG_SEABIOS on.
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Booting SeaBIOS is done via U-Boot's bootelf command, like below::
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=> tftp bios.bin.elf;bootelf
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Using e1000#0 device
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TFTP from server 10.10.0.100; our IP address is 10.10.0.108
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...
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Bytes transferred = 122124 (1dd0c hex)
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## Starting application at 0x000ff06e ...
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SeaBIOS (version rel-1.9.0)
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...
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bios.bin.elf is the SeaBIOS image built from SeaBIOS source tree.
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Make sure it is built as follows::
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$ make menuconfig
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Inside the "General Features" menu, select "Build for coreboot" as the
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"Build Target". Inside the "Debugging" menu, turn on "Serial port debugging"
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so that we can see something as soon as SeaBIOS boots. Leave other options
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as in their default state. Then::
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$ make
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...
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Total size: 121888 Fixed: 66496 Free: 9184 (used 93.0% of 128KiB rom)
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Creating out/bios.bin.elf
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Currently this is tested on QEMU x86 target with U-Boot chain-loading SeaBIOS
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to install/boot a Windows XP OS (below for example command to install Windows).
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.. code-block:: none
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# Create a 10G disk.img as the virtual hard disk
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$ qemu-img create -f qcow2 disk.img 10G
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# Install a Windows XP OS from an ISO image 'winxp.iso'
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$ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -cdrom winxp.iso -smp 2 -m 512
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# Boot a Windows XP OS installed on the virutal hard disk
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$ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -smp 2 -m 512
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This is also tested on Intel Crown Bay board with a PCIe graphics card, booting
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SeaBIOS then chain-loading a GRUB on a USB drive, then Linux kernel finally.
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If you are using Intel Integrated Graphics Device (IGD) as the primary display
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device on your board, SeaBIOS needs to be patched manually to get its VGA ROM
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loaded and run by SeaBIOS. SeaBIOS locates VGA ROM via the PCI expansion ROM
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register, but IGD device does not have its VGA ROM mapped by this register.
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Its VGA ROM is packaged as part of u-boot.rom at a configurable flash address
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which is unknown to SeaBIOS. An example patch is needed for SeaBIOS below:
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.. code-block:: none
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diff --git a/src/optionroms.c b/src/optionroms.c
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index 65f7fe0..c7b6f5e 100644
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--- a/src/optionroms.c
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+++ b/src/optionroms.c
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@@ -324,6 +324,8 @@ init_pcirom(struct pci_device *pci, int isvga, u64 *sources)
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rom = deploy_romfile(file);
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else if (RunPCIroms > 1 || (RunPCIroms == 1 && isvga))
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rom = map_pcirom(pci);
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+ if (pci->bdf == pci_to_bdf(0, 2, 0))
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+ rom = (struct rom_header *)0xfff90000;
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if (! rom)
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// No ROM present.
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return;
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Note: the patch above expects IGD device is at PCI b.d.f 0.2.0 and its VGA ROM
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is at 0xfff90000 which corresponds to CONFIG_VGA_BIOS_ADDR on Minnowboard MAX.
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Change these two accordingly if this is not the case on your board.
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Development Flow
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----------------
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These notes are for those who want to port U-Boot to a new x86 platform.
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Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment.
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The Dediprog em100 can be used on Linux.
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The em100 tool is available here: http://review.coreboot.org/p/em100.git
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On Minnowboard Max the following command line can be used::
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sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r
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A suitable clip for connecting over the SPI flash chip is here:
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http://www.dediprog.com/pd/programmer-accessories/EM-TC-8.
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This allows you to override the SPI flash contents for development purposes.
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Typically you can write to the em100 in around 1200ms, considerably faster
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than programming the real flash device each time. The only important
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limitation of the em100 is that it only supports SPI bus speeds up to 20MHz.
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This means that images must be set to boot with that speed. This is an
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Intel-specific feature - e.g. tools/ifttool has an option to set the SPI
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speed in the SPI descriptor region.
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If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly
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easy to fit it in. You can follow the Minnowboard Max implementation, for
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example. Hopefully you will just need to create new files similar to those
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in arch/x86/cpu/baytrail which provide Bay Trail support.
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If you are not using an FSP you have more freedom and more responsibility.
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The ivybridge support works this way, although it still uses a ROM for
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graphics and still has binary blobs containing Intel code. You should aim to
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support all important peripherals on your platform including video and storage.
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Use the device tree for configuration where possible.
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For the microcode you can create a suitable device tree file using the
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microcode tool::
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./tools/microcode-tool -d microcode.dat -m <model> create
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or if you only have header files and not the full Intel microcode.dat database::
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./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \
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-H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h -m all create
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These are written to arch/x86/dts/microcode/ by default.
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Note that it is possible to just add the micrcode for your CPU if you know its
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model. U-Boot prints this information when it starts::
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CPU: x86_64, vendor Intel, device 30673h
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so here we can use the M0130673322 file.
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If you platform can display POST codes on two little 7-segment displays on
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the board, then you can use post_code() calls from C or assembler to monitor
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boot progress. This can be good for debugging.
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If not, you can try to get serial working as early as possible. The early
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debug serial port may be useful here. See setup_internal_uart() for an example.
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During the U-Boot porting, one of the important steps is to write correct PIRQ
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routing information in the board device tree. Without it, device drivers in the
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Linux kernel won't function correctly due to interrupt is not working. Please
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refer to U-Boot `doc <doc/device-tree-bindings/misc/intel,irq-router.txt>`_ for
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the device tree bindings of Intel interrupt router. Here we have more details
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on the intel,pirq-routing property below.
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.. code-block:: none
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intel,pirq-routing = <
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PCI_BDF(0, 2, 0) INTA PIRQA
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...
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>;
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As you see each entry has 3 cells. For the first one, we need describe all pci
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devices mounted on the board. For SoC devices, normally there is a chapter on
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the chipset datasheet which lists all the available PCI devices. For example on
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Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we
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can get the interrupt pin either from datasheet or hardware via U-Boot shell.
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The reliable source is the hardware as sometimes chipset datasheet is not 100%
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up-to-date. Type 'pci header' plus the device's pci bus/device/function number
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from U-Boot shell below::
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=> pci header 0.1e.1
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vendor ID = 0x8086
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device ID = 0x0f08
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...
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interrupt line = 0x09
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interrupt pin = 0x04
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...
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It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin
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register. Repeat this until you get interrupt pins for all the devices. The last
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cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel
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chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This
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can be changed by registers in LPC bridge. So far Intel FSP does not touch those
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registers so we can write down the PIRQ according to the default mapping rule.
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Once we get the PIRQ routing information in the device tree, the interrupt
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allocation and assignment will be done by U-Boot automatically. Now you can
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enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and
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CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC.
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This script might be useful. If you feed it the output of 'pci long' from
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U-Boot then it will generate a device tree fragment with the interrupt
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configuration for each device (note it needs gawk 4.0.0)::
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$ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \
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/interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \
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{patsplit(device, bdf, "[0-9a-f]+"); \
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printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \
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strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}'
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Example output::
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PCI_BDF(0, 2, 0) INTA PIRQA
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PCI_BDF(0, 3, 0) INTA PIRQA
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...
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Porting Hints
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-------------
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Quark-specific considerations
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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To port U-Boot to other boards based on the Intel Quark SoC, a few things need
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to be taken care of. The first important part is the Memory Reference Code (MRC)
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parameters. Quark MRC supports memory-down configuration only. All these MRC
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parameters are supplied via the board device tree. To get started, first copy
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the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then
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change these values by consulting board manuals or your hardware vendor.
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Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h.
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The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports,
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but by default they are held in reset after power on. In U-Boot, PCIe
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initialization is properly handled as per Quark's firmware writer guide.
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In your board support codes, you need provide two routines to aid PCIe
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initialization, which are board_assert_perst() and board_deassert_perst().
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The two routines need implement a board-specific mechanism to assert/deassert
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PCIe PERST# pin. Care must be taken that in those routines that any APIs that
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may trigger PCI enumeration process are strictly forbidden, as any access to
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PCIe root port's configuration registers will cause system hang while it is
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held in reset. For more details, check how they are implemented by the Intel
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Galileo board support codes in board/intel/galileo/galileo.c.
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coreboot
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^^^^^^^^
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See scripts/coreboot.sed which can assist with porting coreboot code into
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U-Boot drivers. It will not resolve all build errors, but will perform common
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transformations. Remember to add attribution to coreboot for new files added
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to U-Boot. This should go at the top of each file and list the coreboot
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filename where the code originated.
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Debugging ACPI issues with Windows
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Windows might cache system information and only detect ACPI changes if you
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modify the ACPI table versions. So tweak them liberally when debugging ACPI
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issues with Windows.
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ACPI Support Status
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-------------------
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Advanced Configuration and Power Interface (`ACPI`_) aims to establish
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industry-standard interfaces enabling OS-directed configuration, power
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management, and thermal management of mobile, desktop, and server platforms.
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Linux can boot without ACPI with "acpi=off" command line parameter, but
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with ACPI the kernel gains the capabilities to handle power management.
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For Windows, ACPI is a must-have firmware feature since Windows Vista.
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CONFIG_GENERATE_ACPI_TABLE is the config option to turn on ACPI support in
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U-Boot. This requires Intel ACPI compiler to be installed on your host to
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compile ACPI DSDT table written in ASL format to AML format. You can get
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the compiler via "apt-get install iasl" if you are on Ubuntu or download
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the source from https://www.acpica.org/downloads to compile one by yourself.
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Current ACPI support in U-Boot is basically complete. More optional features
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can be added in the future. The status as of today is:
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* Support generating RSDT, XSDT, FACS, FADT, MADT, MCFG tables.
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* Support one static DSDT table only, compiled by Intel ACPI compiler.
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* Support S0/S3/S4/S5, reboot and shutdown from OS.
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* Support booting a pre-installed Ubuntu distribution via 'zboot' command.
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* Support installing and booting Ubuntu 14.04 (or above) from U-Boot with
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the help of SeaBIOS using legacy interface (non-UEFI mode).
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* Support installing and booting Windows 8.1/10 from U-Boot with the help
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of SeaBIOS using legacy interface (non-UEFI mode).
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* Support ACPI interrupts with SCI only.
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Features that are optional:
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* Dynamic AML bytecodes insertion at run-time. We may need this to support
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SSDT table generation and DSDT fix up.
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* SMI support. Since U-Boot is a modern bootloader, we don't want to bring
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those legacy stuff into U-Boot. ACPI spec allows a system that does not
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support SMI (a legacy-free system).
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ACPI was initially enabled on BayTrail based boards. Testing was done by booting
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a pre-installed Ubuntu 14.04 from a SATA drive. Installing Ubuntu 14.04 and
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Windows 8.1/10 to a SATA drive and booting from there is also tested. Most
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devices seem to work correctly and the board can respond a reboot/shutdown
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command from the OS.
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For other platform boards, ACPI support status can be checked by examining their
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board defconfig files to see if CONFIG_GENERATE_ACPI_TABLE is set to y.
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The S3 sleeping state is a low wake latency sleeping state defined by ACPI
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spec where all system context is lost except system memory. To test S3 resume
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with a Linux kernel, simply run "echo mem > /sys/power/state" and kernel will
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put the board to S3 state where the power is off. So when the power button is
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pressed again, U-Boot runs as it does in cold boot and detects the sleeping
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state via ACPI register to see if it is S3, if yes it means we are waking up.
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U-Boot is responsible for restoring the machine state as it is before sleep.
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When everything is done, U-Boot finds out the wakeup vector provided by OSes
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and jump there. To determine whether ACPI S3 resume is supported, check to
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see if CONFIG_HAVE_ACPI_RESUME is set for that specific board.
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Note for testing S3 resume with Windows, correct graphics driver must be
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installed for your platform, otherwise you won't find "Sleep" option in
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the "Power" submenu from the Windows start menu.
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EFI Support
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-----------
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U-Boot supports booting as a 32-bit or 64-bit EFI payload, e.g. with UEFI.
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This is enabled with CONFIG_EFI_STUB to boot from both 32-bit and 64-bit
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UEFI BIOS. U-Boot can also run as an EFI application, with CONFIG_EFI_APP.
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The CONFIG_EFI_LOADER option, where U-Boot provides an EFI environment to
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the kernel (i.e. replaces UEFI completely but provides the same EFI run-time
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services) is supported too. For example, we can even use 'bootefi' command
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to load a 'u-boot-payload.efi', see below test logs on QEMU.
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.. code-block:: none
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=> load ide 0 3000000 u-boot-payload.efi
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489787 bytes read in 138 ms (3.4 MiB/s)
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=> bootefi 3000000
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Scanning disk ide.blk#0...
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Found 2 disks
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WARNING: booting without device tree
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## Starting EFI application at 03000000 ...
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U-Boot EFI Payload
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U-Boot 2018.07-rc2 (Jun 23 2018 - 17:12:58 +0800)
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CPU: x86_64, vendor AMD, device 663h
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DRAM: 2 GiB
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MMC:
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Video: 1024x768x32
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Model: EFI x86 Payload
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Net: e1000: 52:54:00:12:34:56
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Warning: e1000#0 using MAC address from ROM
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eth0: e1000#0
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No controllers found
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Hit any key to stop autoboot: 0
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See :doc:`../uefi/u-boot_on_efi` and :doc:`../uefi/uefi` for details of
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EFI support in U-Boot.
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TODO List
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---------
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- Audio
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- Chrome OS verified boot
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.. _coreboot: http://www.coreboot.org
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.. _QEMU: http://www.qemu.org
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.. _microcode: http://en.wikipedia.org/wiki/Microcode
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.. _SFI: http://simplefirmware.org
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.. _MP: http://www.intel.com/design/archives/processors/pro/docs/242016.htm
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.. _here: https://en.wikipedia.org/wiki/GUID_Partition_Table
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.. _this: http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf
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.. _that: http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf
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.. _SeaBIOS: http://www.seabios.org/SeaBIOS
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.. _ACPI: http://www.acpi.info
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