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diff --git a/doc/arch/x86.rst b/doc/arch/x86.rst new file mode 100644 index 0000000000..2eb524cc8f --- /dev/null +++ b/doc/arch/x86.rst @@ -0,0 +1,728 @@ +.. SPDX-License-Identifier: GPL-2.0+ +.. Copyright (C) 2014, Simon Glass <sjg@chromium.org> +.. Copyright (C) 2014, Bin Meng <bmeng.cn@gmail.com> + +x86 +=== + +This document describes the information about U-Boot running on x86 targets, +including supported boards, build instructions, todo list, etc. + +Status +------ +U-Boot supports running as a `coreboot`_ payload on x86. So far only Link +(Chromebook Pixel) and `QEMU`_ x86 targets have been tested, but it should +work with minimal adjustments on other x86 boards since coreboot deals with +most of the low-level details. + +U-Boot is a main bootloader on Intel Edison board. + +U-Boot also supports booting directly from x86 reset vector, without coreboot. +In this case, known as bare mode, from the fact that it runs on the +'bare metal', U-Boot acts like a BIOS replacement. The following platforms +are supported: + + - Bayley Bay CRB + - Cherry Hill CRB + - Congatec QEVAL 2.0 & conga-QA3/E3845 + - Cougar Canyon 2 CRB + - Crown Bay CRB + - Galileo + - Link (Chromebook Pixel) + - Minnowboard MAX + - Samus (Chromebook Pixel 2015) + - QEMU x86 (32-bit & 64-bit) + +As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit +Linux kernel as part of a FIT image. It also supports a compressed zImage. +U-Boot supports loading an x86 VxWorks kernel. Please check README.vxworks +for more details. + +Build Instructions for U-Boot as BIOS replacement (bare mode) +------------------------------------------------------------- +Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a +little bit tricky, as generally it requires several binary blobs which are not +shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build is +not turned on by default in the U-Boot source tree. Firstly, you need turn it +on by enabling the ROM build either via an environment variable:: + + $ export BUILD_ROM=y + +or via configuration:: + + CONFIG_BUILD_ROM=y + +Both tell the Makefile to build u-boot.rom as a target. + +CPU Microcode +------------- +Modern CPUs usually require a special bit stream called `microcode`_ to be +loaded on the processor after power up in order to function properly. U-Boot +has already integrated these as hex dumps in the source tree. + +SMP Support +----------- +On a multicore system, U-Boot is executed on the bootstrap processor (BSP). +Additional application processors (AP) can be brought up by U-Boot. In order to +have an SMP kernel to discover all of the available processors, U-Boot needs to +prepare configuration tables which contain the multi-CPUs information before +loading the OS kernel. Currently U-Boot supports generating two types of tables +for SMP, called Simple Firmware Interface (`SFI`_) and Multi-Processor (`MP`_) +tables. The writing of these two tables are controlled by two Kconfig +options GENERATE_SFI_TABLE and GENERATE_MP_TABLE. + +Driver Model +------------ +x86 has been converted to use driver model for serial, GPIO, SPI, SPI flash, +keyboard, real-time clock, USB. Video is in progress. + +Device Tree +----------- +x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to +be turned on. Not every device on the board is configured via device tree, but +more and more devices will be added as time goes by. Check out the directory +arch/x86/dts/ for these device tree source files. + +Useful Commands +--------------- +In keeping with the U-Boot philosophy of providing functions to check and +adjust internal settings, there are several x86-specific commands that may be +useful: + +fsp + Display information about Intel Firmware Support Package (FSP). + This is only available on platforms which use FSP, mostly Atom. +iod + Display I/O memory +iow + Write I/O memory +mtrr + List and set the Memory Type Range Registers (MTRR). These are used to + tell the CPU whether memory is cacheable and if so the cache write + mode to use. U-Boot sets up some reasonable values but you can + adjust then with this command. + +Booting Ubuntu +-------------- +As an example of how to set up your boot flow with U-Boot, here are +instructions for starting Ubuntu from U-Boot. These instructions have been +tested on Minnowboard MAX with a SATA drive but are equally applicable on +other platforms and other media. There are really only four steps and it's a +very simple script, but a more detailed explanation is provided here for +completeness. + +Note: It is possible to set up U-Boot to boot automatically using syslinux. +It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the +GUID. If you figure these out, please post patches to this README. + +Firstly, you will need Ubuntu installed on an available disk. It should be +possible to make U-Boot start a USB start-up disk but for now let's assume +that you used another boot loader to install Ubuntu. + +Use the U-Boot command line to find the UUID of the partition you want to +boot. For example our disk is SCSI device 0:: + + => part list scsi 0 + + Partition Map for SCSI device 0 -- Partition Type: EFI + + Part Start LBA End LBA Name + Attributes + Type GUID + Partition GUID + 1 0x00000800 0x001007ff "" + attrs: 0x0000000000000000 + type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b + guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c + 2 0x00100800 0x037d8fff "" + attrs: 0x0000000000000000 + type: 0fc63daf-8483-4772-8e79-3d69d8477de4 + guid: 965c59ee-1822-4326-90d2-b02446050059 + 3 0x037d9000 0x03ba27ff "" + attrs: 0x0000000000000000 + type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f + guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17 + => + +This shows that your SCSI disk has three partitions. The really long hex +strings are called Globally Unique Identifiers (GUIDs). You can look up the +'type' ones `here`_. On this disk the first partition is for EFI and is in +VFAT format (DOS/Windows):: + + => fatls scsi 0:1 + efi/ + + 0 file(s), 1 dir(s) + + +Partition 2 is 'Linux filesystem data' so that will be our root disk. It is +in ext2 format:: + + => ext2ls scsi 0:2 + <DIR> 4096 . + <DIR> 4096 .. + <DIR> 16384 lost+found + <DIR> 4096 boot + <DIR> 12288 etc + <DIR> 4096 media + <DIR> 4096 bin + <DIR> 4096 dev + <DIR> 4096 home + <DIR> 4096 lib + <DIR> 4096 lib64 + <DIR> 4096 mnt + <DIR> 4096 opt + <DIR> 4096 proc + <DIR> 4096 root + <DIR> 4096 run + <DIR> 12288 sbin + <DIR> 4096 srv + <DIR> 4096 sys + <DIR> 4096 tmp + <DIR> 4096 usr + <DIR> 4096 var + <SYM> 33 initrd.img + <SYM> 30 vmlinuz + <DIR> 4096 cdrom + <SYM> 33 initrd.img.old + => + +and if you look in the /boot directory you will see the kernel:: + + => ext2ls scsi 0:2 /boot + <DIR> 4096 . + <DIR> 4096 .. + <DIR> 4096 efi + <DIR> 4096 grub + 3381262 System.map-3.13.0-32-generic + 1162712 abi-3.13.0-32-generic + 165611 config-3.13.0-32-generic + 176500 memtest86+.bin + 178176 memtest86+.elf + 178680 memtest86+_multiboot.bin + 5798112 vmlinuz-3.13.0-32-generic + 165762 config-3.13.0-58-generic + 1165129 abi-3.13.0-58-generic + 5823136 vmlinuz-3.13.0-58-generic + 19215259 initrd.img-3.13.0-58-generic + 3391763 System.map-3.13.0-58-generic + 5825048 vmlinuz-3.13.0-58-generic.efi.signed + 28304443 initrd.img-3.13.0-32-generic + => + +The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of +self-extracting compressed file mixed with some 'setup' configuration data. +Despite its size (uncompressed it is >10MB) this only includes a basic set of +device drivers, enough to boot on most hardware types. + +The 'initrd' files contain a RAM disk. This is something that can be loaded +into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots +of drivers for whatever hardware you might have. It is loaded before the +real root disk is accessed. + +The numbers after the end of each file are the version. Here it is Linux +version 3.13. You can find the source code for this in the Linux tree with +the tag v3.13. The '.0' allows for additional Linux releases to fix problems, +but normally this is not needed. The '-58' is used by Ubuntu. Each time they +release a new kernel they increment this number. New Ubuntu versions might +include kernel patches to fix reported bugs. Stable kernels can exist for +some years so this number can get quite high. + +The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own +secure boot mechanism - see `this`_ & `that`_. It cannot read .efi files +at present. + +To boot Ubuntu from U-Boot the steps are as follows: + +1. Set up the boot arguments. Use the GUID for the partition you want to boot:: + + => setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro + +Here root= tells Linux the location of its root disk. The disk is specified +by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory' +containing all the GUIDs Linux has found. When it starts up, there will be a +file in that directory with this name in it. It is also possible to use a +device name here, see later. + +2. Load the kernel. Since it is an ext2/4 filesystem we can do:: + + => ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic + +The address 30000000 is arbitrary, but there seem to be problems with using +small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into +the start of RAM (which is at 0 on x86). + +3. Load the ramdisk (to 64MB):: + + => ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic + +4. Start up the kernel. We need to know the size of the ramdisk, but can use + a variable for that. U-Boot sets 'filesize' to the size of the last file it + loaded:: + + => zboot 03000000 0 04000000 ${filesize} + +Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is +quite verbose when it boots a kernel. You should see these messages from +U-Boot:: + + Valid Boot Flag + Setup Size = 0x00004400 + Magic signature found + Using boot protocol version 2.0c + Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015 + Building boot_params at 0x00090000 + Loading bzImage at address 100000 (5805728 bytes) + Magic signature found + Initial RAM disk at linear address 0x04000000, size 19215259 bytes + Kernel command line: "root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro" + + Starting kernel ... + +U-Boot prints out some bootstage timing. This is more useful if you put the +above commands into a script since then it will be faster:: + + Timer summary in microseconds: + Mark Elapsed Stage + 0 0 reset + 241,535 241,535 board_init_r + 2,421,611 2,180,076 id=64 + 2,421,790 179 id=65 + 2,428,215 6,425 main_loop + 48,860,584 46,432,369 start_kernel + + Accumulated time: + 240,329 ahci + 1,422,704 vesa display + +Now the kernel actually starts (if you want to examine kernel boot up message on +the serial console, append "console=ttyS0,115200" to the kernel command line):: + + [ 0.000000] Initializing cgroup subsys cpuset + [ 0.000000] Initializing cgroup subsys cpu + [ 0.000000] Initializing cgroup subsys cpuacct + [ 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) + [ 0.000000] Command line: root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro console=ttyS0,115200 + +It continues for a long time. Along the way you will see it pick up your +ramdisk:: + + [ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff] + ... + [ 0.788540] Trying to unpack rootfs image as initramfs... + [ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000) + ... + +Later it actually starts using it:: + + Begin: Running /scripts/local-premount ... done. + +You should also see your boot disk turn up:: + + [ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5 + [ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB) + [ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0 + [ 4.381859] sd 1:0:0:0: [sda] Write Protect is off + [ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA + [ 4.399535] sda: sda1 sda2 sda3 + +Linux has found the three partitions (sda1-3). Mercifully it doesn't print out +the GUIDs. In step 1 above we could have used:: + + setenv bootargs root=/dev/sda2 ro + +instead of the GUID. However if you add another drive to your board the +numbering may change whereas the GUIDs will not. So if your boot partition +becomes sdb2, it will still boot. For embedded systems where you just want to +boot the first disk, you have that option. + +The last thing you will see on the console is mention of plymouth (which +displays the Ubuntu start-up screen) and a lot of 'Starting' messages:: + + * Starting Mount filesystems on boot [ OK ] + +After a pause you should see a login screen on your display and you are done. + +If you want to put this in a script you can use something like this:: + + setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro + setenv boot zboot 03000000 0 04000000 \${filesize} + 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" + saveenv + +The \ is to tell the shell not to evaluate ${filesize} as part of the setenv +command. + +You can also bake this behaviour into your build by hard-coding the +environment variables if you add this to minnowmax.h: + +.. code-block:: c + + #undef CONFIG_BOOTCOMMAND + #define CONFIG_BOOTCOMMAND \ + "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" + + #undef CONFIG_EXTRA_ENV_SETTINGS + #define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}" + +and change CONFIG_BOOTARGS value in configs/minnowmax_defconfig to:: + + CONFIG_BOOTARGS="root=/dev/sda2 ro" + +Test with SeaBIOS +----------------- +`SeaBIOS`_ is an open source implementation of a 16-bit x86 BIOS. It can run +in an emulator or natively on x86 hardware with the use of U-Boot. With its +help, we can boot some OSes that require 16-bit BIOS services like Windows/DOS. + +As U-Boot, we have to manually create a table where SeaBIOS gets various system +information (eg: E820) from. The table unfortunately has to follow the coreboot +table format as SeaBIOS currently supports booting as a coreboot payload. + +To support loading SeaBIOS, U-Boot should be built with CONFIG_SEABIOS on. +Booting SeaBIOS is done via U-Boot's bootelf command, like below:: + + => tftp bios.bin.elf;bootelf + Using e1000#0 device + TFTP from server 10.10.0.100; our IP address is 10.10.0.108 + ... + Bytes transferred = 122124 (1dd0c hex) + ## Starting application at 0x000ff06e ... + SeaBIOS (version rel-1.9.0) + ... + +bios.bin.elf is the SeaBIOS image built from SeaBIOS source tree. +Make sure it is built as follows:: + + $ make menuconfig + +Inside the "General Features" menu, select "Build for coreboot" as the +"Build Target". Inside the "Debugging" menu, turn on "Serial port debugging" +so that we can see something as soon as SeaBIOS boots. Leave other options +as in their default state. Then:: + + $ make + ... + Total size: 121888 Fixed: 66496 Free: 9184 (used 93.0% of 128KiB rom) + Creating out/bios.bin.elf + +Currently this is tested on QEMU x86 target with U-Boot chain-loading SeaBIOS +to install/boot a Windows XP OS (below for example command to install Windows). + +.. code-block:: none + + # Create a 10G disk.img as the virtual hard disk + $ qemu-img create -f qcow2 disk.img 10G + + # Install a Windows XP OS from an ISO image 'winxp.iso' + $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -cdrom winxp.iso -smp 2 -m 512 + + # Boot a Windows XP OS installed on the virutal hard disk + $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -smp 2 -m 512 + +This is also tested on Intel Crown Bay board with a PCIe graphics card, booting +SeaBIOS then chain-loading a GRUB on a USB drive, then Linux kernel finally. + +If you are using Intel Integrated Graphics Device (IGD) as the primary display +device on your board, SeaBIOS needs to be patched manually to get its VGA ROM +loaded and run by SeaBIOS. SeaBIOS locates VGA ROM via the PCI expansion ROM +register, but IGD device does not have its VGA ROM mapped by this register. +Its VGA ROM is packaged as part of u-boot.rom at a configurable flash address +which is unknown to SeaBIOS. An example patch is needed for SeaBIOS below: + +.. code-block:: none + + diff --git a/src/optionroms.c b/src/optionroms.c + index 65f7fe0..c7b6f5e 100644 + --- a/src/optionroms.c + +++ b/src/optionroms.c + @@ -324,6 +324,8 @@ init_pcirom(struct pci_device *pci, int isvga, u64 *sources) + rom = deploy_romfile(file); + else if (RunPCIroms > 1 || (RunPCIroms == 1 && isvga)) + rom = map_pcirom(pci); + + if (pci->bdf == pci_to_bdf(0, 2, 0)) + + rom = (struct rom_header *)0xfff90000; + if (! rom) + // No ROM present. + return; + +Note: the patch above expects IGD device is at PCI b.d.f 0.2.0 and its VGA ROM +is at 0xfff90000 which corresponds to CONFIG_VGA_BIOS_ADDR on Minnowboard MAX. +Change these two accordingly if this is not the case on your board. + +Development Flow +---------------- +These notes are for those who want to port U-Boot to a new x86 platform. + +Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment. +The Dediprog em100 can be used on Linux. + +The em100 tool is available here: http://review.coreboot.org/p/em100.git + +On Minnowboard Max the following command line can be used:: + + sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r + +A suitable clip for connecting over the SPI flash chip is here: +http://www.dediprog.com/pd/programmer-accessories/EM-TC-8. + +This allows you to override the SPI flash contents for development purposes. +Typically you can write to the em100 in around 1200ms, considerably faster +than programming the real flash device each time. The only important +limitation of the em100 is that it only supports SPI bus speeds up to 20MHz. +This means that images must be set to boot with that speed. This is an +Intel-specific feature - e.g. tools/ifttool has an option to set the SPI +speed in the SPI descriptor region. + +If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly +easy to fit it in. You can follow the Minnowboard Max implementation, for +example. Hopefully you will just need to create new files similar to those +in arch/x86/cpu/baytrail which provide Bay Trail support. + +If you are not using an FSP you have more freedom and more responsibility. +The ivybridge support works this way, although it still uses a ROM for +graphics and still has binary blobs containing Intel code. You should aim to +support all important peripherals on your platform including video and storage. +Use the device tree for configuration where possible. + +For the microcode you can create a suitable device tree file using the +microcode tool:: + + ./tools/microcode-tool -d microcode.dat -m <model> create + +or if you only have header files and not the full Intel microcode.dat database:: + + ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \ + -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h -m all create + +These are written to arch/x86/dts/microcode/ by default. + +Note that it is possible to just add the micrcode for your CPU if you know its +model. U-Boot prints this information when it starts:: + + CPU: x86_64, vendor Intel, device 30673h + +so here we can use the M0130673322 file. + +If you platform can display POST codes on two little 7-segment displays on +the board, then you can use post_code() calls from C or assembler to monitor +boot progress. This can be good for debugging. + +If not, you can try to get serial working as early as possible. The early +debug serial port may be useful here. See setup_internal_uart() for an example. + +During the U-Boot porting, one of the important steps is to write correct PIRQ +routing information in the board device tree. Without it, device drivers in the +Linux kernel won't function correctly due to interrupt is not working. Please +refer to U-Boot `doc <doc/device-tree-bindings/misc/intel,irq-router.txt>`_ for +the device tree bindings of Intel interrupt router. Here we have more details +on the intel,pirq-routing property below. + +.. code-block:: none + + intel,pirq-routing = < + PCI_BDF(0, 2, 0) INTA PIRQA + ... + >; + +As you see each entry has 3 cells. For the first one, we need describe all pci +devices mounted on the board. For SoC devices, normally there is a chapter on +the chipset datasheet which lists all the available PCI devices. For example on +Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we +can get the interrupt pin either from datasheet or hardware via U-Boot shell. +The reliable source is the hardware as sometimes chipset datasheet is not 100% +up-to-date. Type 'pci header' plus the device's pci bus/device/function number +from U-Boot shell below:: + + => pci header 0.1e.1 + vendor ID = 0x8086 + device ID = 0x0f08 + ... + interrupt line = 0x09 + interrupt pin = 0x04 + ... + +It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin +register. Repeat this until you get interrupt pins for all the devices. The last +cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel +chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This +can be changed by registers in LPC bridge. So far Intel FSP does not touch those +registers so we can write down the PIRQ according to the default mapping rule. + +Once we get the PIRQ routing information in the device tree, the interrupt +allocation and assignment will be done by U-Boot automatically. Now you can +enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and +CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC. + +This script might be useful. If you feed it the output of 'pci long' from +U-Boot then it will generate a device tree fragment with the interrupt +configuration for each device (note it needs gawk 4.0.0):: + + $ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \ + /interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \ + {patsplit(device, bdf, "[0-9a-f]+"); \ + printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \ + strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}' + +Example output:: + + PCI_BDF(0, 2, 0) INTA PIRQA + PCI_BDF(0, 3, 0) INTA PIRQA + ... + +Porting Hints +------------- + +Quark-specific considerations +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +To port U-Boot to other boards based on the Intel Quark SoC, a few things need +to be taken care of. The first important part is the Memory Reference Code (MRC) +parameters. Quark MRC supports memory-down configuration only. All these MRC +parameters are supplied via the board device tree. To get started, first copy +the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then +change these values by consulting board manuals or your hardware vendor. +Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h. +The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports, +but by default they are held in reset after power on. In U-Boot, PCIe +initialization is properly handled as per Quark's firmware writer guide. +In your board support codes, you need provide two routines to aid PCIe +initialization, which are board_assert_perst() and board_deassert_perst(). +The two routines need implement a board-specific mechanism to assert/deassert +PCIe PERST# pin. Care must be taken that in those routines that any APIs that +may trigger PCI enumeration process are strictly forbidden, as any access to +PCIe root port's configuration registers will cause system hang while it is +held in reset. For more details, check how they are implemented by the Intel +Galileo board support codes in board/intel/galileo/galileo.c. + +coreboot +^^^^^^^^ + +See scripts/coreboot.sed which can assist with porting coreboot code into +U-Boot drivers. It will not resolve all build errors, but will perform common +transformations. Remember to add attribution to coreboot for new files added +to U-Boot. This should go at the top of each file and list the coreboot +filename where the code originated. + +Debugging ACPI issues with Windows +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Windows might cache system information and only detect ACPI changes if you +modify the ACPI table versions. So tweak them liberally when debugging ACPI +issues with Windows. + +ACPI Support Status +------------------- +Advanced Configuration and Power Interface (`ACPI`_) aims to establish +industry-standard interfaces enabling OS-directed configuration, power +management, and thermal management of mobile, desktop, and server platforms. + +Linux can boot without ACPI with "acpi=off" command line parameter, but +with ACPI the kernel gains the capabilities to handle power management. +For Windows, ACPI is a must-have firmware feature since Windows Vista. +CONFIG_GENERATE_ACPI_TABLE is the config option to turn on ACPI support in +U-Boot. This requires Intel ACPI compiler to be installed on your host to +compile ACPI DSDT table written in ASL format to AML format. You can get +the compiler via "apt-get install iasl" if you are on Ubuntu or download +the source from https://www.acpica.org/downloads to compile one by yourself. + +Current ACPI support in U-Boot is basically complete. More optional features +can be added in the future. The status as of today is: + + * Support generating RSDT, XSDT, FACS, FADT, MADT, MCFG tables. + * Support one static DSDT table only, compiled by Intel ACPI compiler. + * Support S0/S3/S4/S5, reboot and shutdown from OS. + * Support booting a pre-installed Ubuntu distribution via 'zboot' command. + * Support installing and booting Ubuntu 14.04 (or above) from U-Boot with + the help of SeaBIOS using legacy interface (non-UEFI mode). + * Support installing and booting Windows 8.1/10 from U-Boot with the help + of SeaBIOS using legacy interface (non-UEFI mode). + * Support ACPI interrupts with SCI only. + +Features that are optional: + + * Dynamic AML bytecodes insertion at run-time. We may need this to support + SSDT table generation and DSDT fix up. + * SMI support. Since U-Boot is a modern bootloader, we don't want to bring + those legacy stuff into U-Boot. ACPI spec allows a system that does not + support SMI (a legacy-free system). + +ACPI was initially enabled on BayTrail based boards. Testing was done by booting +a pre-installed Ubuntu 14.04 from a SATA drive. Installing Ubuntu 14.04 and +Windows 8.1/10 to a SATA drive and booting from there is also tested. Most +devices seem to work correctly and the board can respond a reboot/shutdown +command from the OS. + +For other platform boards, ACPI support status can be checked by examining their +board defconfig files to see if CONFIG_GENERATE_ACPI_TABLE is set to y. + +The S3 sleeping state is a low wake latency sleeping state defined by ACPI +spec where all system context is lost except system memory. To test S3 resume +with a Linux kernel, simply run "echo mem > /sys/power/state" and kernel will +put the board to S3 state where the power is off. So when the power button is +pressed again, U-Boot runs as it does in cold boot and detects the sleeping +state via ACPI register to see if it is S3, if yes it means we are waking up. +U-Boot is responsible for restoring the machine state as it is before sleep. +When everything is done, U-Boot finds out the wakeup vector provided by OSes +and jump there. To determine whether ACPI S3 resume is supported, check to +see if CONFIG_HAVE_ACPI_RESUME is set for that specific board. + +Note for testing S3 resume with Windows, correct graphics driver must be +installed for your platform, otherwise you won't find "Sleep" option in +the "Power" submenu from the Windows start menu. + +EFI Support +----------- +U-Boot supports booting as a 32-bit or 64-bit EFI payload, e.g. with UEFI. +This is enabled with CONFIG_EFI_STUB to boot from both 32-bit and 64-bit +UEFI BIOS. U-Boot can also run as an EFI application, with CONFIG_EFI_APP. +The CONFIG_EFI_LOADER option, where U-Boot provides an EFI environment to +the kernel (i.e. replaces UEFI completely but provides the same EFI run-time +services) is supported too. For example, we can even use 'bootefi' command +to load a 'u-boot-payload.efi', see below test logs on QEMU. + +.. code-block:: none + + => load ide 0 3000000 u-boot-payload.efi + 489787 bytes read in 138 ms (3.4 MiB/s) + => bootefi 3000000 + Scanning disk ide.blk#0... + Found 2 disks + WARNING: booting without device tree + ## Starting EFI application at 03000000 ... + U-Boot EFI Payload + + + U-Boot 2018.07-rc2 (Jun 23 2018 - 17:12:58 +0800) + + CPU: x86_64, vendor AMD, device 663h + DRAM: 2 GiB + MMC: + Video: 1024x768x32 + Model: EFI x86 Payload + Net: e1000: 52:54:00:12:34:56 + + Warning: e1000#0 using MAC address from ROM + eth0: e1000#0 + No controllers found + Hit any key to stop autoboot: 0 + +See README.u-boot_on_efi and README.uefi for details of EFI support in U-Boot. + +TODO List +--------- +- Audio +- Chrome OS verified boot + +.. _coreboot: http://www.coreboot.org +.. _QEMU: http://www.qemu.org +.. _microcode: http://en.wikipedia.org/wiki/Microcode +.. _SFI: http://simplefirmware.org +.. _MP: http://www.intel.com/design/archives/processors/pro/docs/242016.htm +.. _here: https://en.wikipedia.org/wiki/GUID_Partition_Table +.. _this: http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf +.. _that: http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf +.. _SeaBIOS: http://www.seabios.org/SeaBIOS +.. _ACPI: http://www.acpi.info |