x86.rst 31 KB

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  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>
  4. x86
  5. ===
  6. This document describes the information about U-Boot running on x86 targets,
  7. including supported boards, build instructions, todo list, etc.
  8. Status
  9. ------
  10. U-Boot supports running as a `coreboot`_ payload on x86. So far only Link
  11. (Chromebook Pixel) and `QEMU`_ x86 targets have been tested, but it should
  12. work with minimal adjustments on other x86 boards since coreboot deals with
  13. most of the low-level details.
  14. U-Boot is a main bootloader on Intel Edison board.
  15. U-Boot also supports booting directly from x86 reset vector, without coreboot.
  16. In this case, known as bare mode, from the fact that it runs on the
  17. 'bare metal', U-Boot acts like a BIOS replacement. The following platforms
  18. are supported:
  19. - Bayley Bay CRB
  20. - Cherry Hill CRB
  21. - Congatec QEVAL 2.0 & conga-QA3/E3845
  22. - Cougar Canyon 2 CRB
  23. - Crown Bay CRB
  24. - Galileo
  25. - Link (Chromebook Pixel)
  26. - Minnowboard MAX
  27. - Samus (Chromebook Pixel 2015)
  28. - QEMU x86 (32-bit & 64-bit)
  29. As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit
  30. Linux kernel as part of a FIT image. It also supports a compressed zImage.
  31. U-Boot supports loading an x86 VxWorks kernel. Please check README.vxworks
  32. for more details.
  33. Build Instructions for U-Boot as BIOS replacement (bare mode)
  34. -------------------------------------------------------------
  35. Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a
  36. little bit tricky, as generally it requires several binary blobs which are not
  37. shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build may
  38. print some warnings if required binary blobs (e.g.: FSP) are not present.
  39. CPU Microcode
  40. -------------
  41. Modern CPUs usually require a special bit stream called `microcode`_ to be
  42. loaded on the processor after power up in order to function properly. U-Boot
  43. has already integrated these as hex dumps in the source tree.
  44. SMP Support
  45. -----------
  46. On a multicore system, U-Boot is executed on the bootstrap processor (BSP).
  47. Additional application processors (AP) can be brought up by U-Boot. In order to
  48. have an SMP kernel to discover all of the available processors, U-Boot needs to
  49. prepare configuration tables which contain the multi-CPUs information before
  50. loading the OS kernel. Currently U-Boot supports generating two types of tables
  51. for SMP, called Simple Firmware Interface (`SFI`_) and Multi-Processor (`MP`_)
  52. tables. The writing of these two tables are controlled by two Kconfig
  53. options GENERATE_SFI_TABLE and GENERATE_MP_TABLE.
  54. Driver Model
  55. ------------
  56. x86 has been converted to use driver model for serial, GPIO, SPI, SPI flash,
  57. keyboard, real-time clock, USB. Video is in progress.
  58. Device Tree
  59. -----------
  60. x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to
  61. be turned on. Not every device on the board is configured via device tree, but
  62. more and more devices will be added as time goes by. Check out the directory
  63. arch/x86/dts/ for these device tree source files.
  64. Useful Commands
  65. ---------------
  66. In keeping with the U-Boot philosophy of providing functions to check and
  67. adjust internal settings, there are several x86-specific commands that may be
  68. useful:
  69. fsp
  70. Display information about Intel Firmware Support Package (FSP).
  71. This is only available on platforms which use FSP, mostly Atom.
  72. iod
  73. Display I/O memory
  74. iow
  75. Write I/O memory
  76. mtrr
  77. List and set the Memory Type Range Registers (MTRR). These are used to
  78. tell the CPU whether memory is cacheable and if so the cache write
  79. mode to use. U-Boot sets up some reasonable values but you can
  80. adjust then with this command.
  81. Booting Ubuntu
  82. --------------
  83. As an example of how to set up your boot flow with U-Boot, here are
  84. instructions for starting Ubuntu from U-Boot. These instructions have been
  85. tested on Minnowboard MAX with a SATA drive but are equally applicable on
  86. other platforms and other media. There are really only four steps and it's a
  87. very simple script, but a more detailed explanation is provided here for
  88. completeness.
  89. Note: It is possible to set up U-Boot to boot automatically using syslinux.
  90. It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the
  91. GUID. If you figure these out, please post patches to this README.
  92. Firstly, you will need Ubuntu installed on an available disk. It should be
  93. possible to make U-Boot start a USB start-up disk but for now let's assume
  94. that you used another boot loader to install Ubuntu.
  95. Use the U-Boot command line to find the UUID of the partition you want to
  96. boot. For example our disk is SCSI device 0::
  97. => part list scsi 0
  98. Partition Map for SCSI device 0 -- Partition Type: EFI
  99. Part Start LBA End LBA Name
  100. Attributes
  101. Type GUID
  102. Partition GUID
  103. 1 0x00000800 0x001007ff ""
  104. attrs: 0x0000000000000000
  105. type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b
  106. guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c
  107. 2 0x00100800 0x037d8fff ""
  108. attrs: 0x0000000000000000
  109. type: 0fc63daf-8483-4772-8e79-3d69d8477de4
  110. guid: 965c59ee-1822-4326-90d2-b02446050059
  111. 3 0x037d9000 0x03ba27ff ""
  112. attrs: 0x0000000000000000
  113. type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f
  114. guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17
  115. =>
  116. This shows that your SCSI disk has three partitions. The really long hex
  117. strings are called Globally Unique Identifiers (GUIDs). You can look up the
  118. 'type' ones `here`_. On this disk the first partition is for EFI and is in
  119. VFAT format (DOS/Windows)::
  120. => fatls scsi 0:1
  121. efi/
  122. 0 file(s), 1 dir(s)
  123. Partition 2 is 'Linux filesystem data' so that will be our root disk. It is
  124. in ext2 format::
  125. => ext2ls scsi 0:2
  126. <DIR> 4096 .
  127. <DIR> 4096 ..
  128. <DIR> 16384 lost+found
  129. <DIR> 4096 boot
  130. <DIR> 12288 etc
  131. <DIR> 4096 media
  132. <DIR> 4096 bin
  133. <DIR> 4096 dev
  134. <DIR> 4096 home
  135. <DIR> 4096 lib
  136. <DIR> 4096 lib64
  137. <DIR> 4096 mnt
  138. <DIR> 4096 opt
  139. <DIR> 4096 proc
  140. <DIR> 4096 root
  141. <DIR> 4096 run
  142. <DIR> 12288 sbin
  143. <DIR> 4096 srv
  144. <DIR> 4096 sys
  145. <DIR> 4096 tmp
  146. <DIR> 4096 usr
  147. <DIR> 4096 var
  148. <SYM> 33 initrd.img
  149. <SYM> 30 vmlinuz
  150. <DIR> 4096 cdrom
  151. <SYM> 33 initrd.img.old
  152. =>
  153. and if you look in the /boot directory you will see the kernel::
  154. => ext2ls scsi 0:2 /boot
  155. <DIR> 4096 .
  156. <DIR> 4096 ..
  157. <DIR> 4096 efi
  158. <DIR> 4096 grub
  159. 3381262 System.map-3.13.0-32-generic
  160. 1162712 abi-3.13.0-32-generic
  161. 165611 config-3.13.0-32-generic
  162. 176500 memtest86+.bin
  163. 178176 memtest86+.elf
  164. 178680 memtest86+_multiboot.bin
  165. 5798112 vmlinuz-3.13.0-32-generic
  166. 165762 config-3.13.0-58-generic
  167. 1165129 abi-3.13.0-58-generic
  168. 5823136 vmlinuz-3.13.0-58-generic
  169. 19215259 initrd.img-3.13.0-58-generic
  170. 3391763 System.map-3.13.0-58-generic
  171. 5825048 vmlinuz-3.13.0-58-generic.efi.signed
  172. 28304443 initrd.img-3.13.0-32-generic
  173. =>
  174. The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of
  175. self-extracting compressed file mixed with some 'setup' configuration data.
  176. Despite its size (uncompressed it is >10MB) this only includes a basic set of
  177. device drivers, enough to boot on most hardware types.
  178. The 'initrd' files contain a RAM disk. This is something that can be loaded
  179. into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots
  180. of drivers for whatever hardware you might have. It is loaded before the
  181. real root disk is accessed.
  182. The numbers after the end of each file are the version. Here it is Linux
  183. version 3.13. You can find the source code for this in the Linux tree with
  184. the tag v3.13. The '.0' allows for additional Linux releases to fix problems,
  185. but normally this is not needed. The '-58' is used by Ubuntu. Each time they
  186. release a new kernel they increment this number. New Ubuntu versions might
  187. include kernel patches to fix reported bugs. Stable kernels can exist for
  188. some years so this number can get quite high.
  189. The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own
  190. secure boot mechanism - see `this`_ & `that`_. It cannot read .efi files
  191. at present.
  192. To boot Ubuntu from U-Boot the steps are as follows:
  193. 1. Set up the boot arguments. Use the GUID for the partition you want to boot::
  194. => setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro
  195. Here root= tells Linux the location of its root disk. The disk is specified
  196. by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory'
  197. containing all the GUIDs Linux has found. When it starts up, there will be a
  198. file in that directory with this name in it. It is also possible to use a
  199. device name here, see later.
  200. 2. Load the kernel. Since it is an ext2/4 filesystem we can do::
  201. => ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic
  202. The address 30000000 is arbitrary, but there seem to be problems with using
  203. small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into
  204. the start of RAM (which is at 0 on x86).
  205. 3. Load the ramdisk (to 64MB)::
  206. => ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic
  207. 4. Start up the kernel. We need to know the size of the ramdisk, but can use
  208. a variable for that. U-Boot sets 'filesize' to the size of the last file it
  209. loaded::
  210. => zboot 03000000 0 04000000 ${filesize}
  211. Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is
  212. quite verbose when it boots a kernel. You should see these messages from
  213. U-Boot::
  214. Valid Boot Flag
  215. Setup Size = 0x00004400
  216. Magic signature found
  217. Using boot protocol version 2.0c
  218. Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015
  219. Building boot_params at 0x00090000
  220. Loading bzImage at address 100000 (5805728 bytes)
  221. Magic signature found
  222. Initial RAM disk at linear address 0x04000000, size 19215259 bytes
  223. Kernel command line: "root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro"
  224. Starting kernel ...
  225. U-Boot prints out some bootstage timing. This is more useful if you put the
  226. above commands into a script since then it will be faster::
  227. Timer summary in microseconds:
  228. Mark Elapsed Stage
  229. 0 0 reset
  230. 241,535 241,535 board_init_r
  231. 2,421,611 2,180,076 id=64
  232. 2,421,790 179 id=65
  233. 2,428,215 6,425 main_loop
  234. 48,860,584 46,432,369 start_kernel
  235. Accumulated time:
  236. 240,329 ahci
  237. 1,422,704 vesa display
  238. Now the kernel actually starts (if you want to examine kernel boot up message on
  239. the serial console, append "console=ttyS0,115200" to the kernel command line)::
  240. [ 0.000000] Initializing cgroup subsys cpuset
  241. [ 0.000000] Initializing cgroup subsys cpu
  242. [ 0.000000] Initializing cgroup subsys cpuacct
  243. [ 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)
  244. [ 0.000000] Command line: root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro console=ttyS0,115200
  245. It continues for a long time. Along the way you will see it pick up your
  246. ramdisk::
  247. [ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff]
  248. ...
  249. [ 0.788540] Trying to unpack rootfs image as initramfs...
  250. [ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000)
  251. ...
  252. Later it actually starts using it::
  253. Begin: Running /scripts/local-premount ... done.
  254. You should also see your boot disk turn up::
  255. [ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5
  256. [ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB)
  257. [ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0
  258. [ 4.381859] sd 1:0:0:0: [sda] Write Protect is off
  259. [ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
  260. [ 4.399535] sda: sda1 sda2 sda3
  261. Linux has found the three partitions (sda1-3). Mercifully it doesn't print out
  262. the GUIDs. In step 1 above we could have used::
  263. setenv bootargs root=/dev/sda2 ro
  264. instead of the GUID. However if you add another drive to your board the
  265. numbering may change whereas the GUIDs will not. So if your boot partition
  266. becomes sdb2, it will still boot. For embedded systems where you just want to
  267. boot the first disk, you have that option.
  268. The last thing you will see on the console is mention of plymouth (which
  269. displays the Ubuntu start-up screen) and a lot of 'Starting' messages::
  270. * Starting Mount filesystems on boot [ OK ]
  271. After a pause you should see a login screen on your display and you are done.
  272. If you want to put this in a script you can use something like this::
  273. setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro
  274. setenv boot zboot 03000000 0 04000000 \${filesize}
  275. 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"
  276. saveenv
  277. The \ is to tell the shell not to evaluate ${filesize} as part of the setenv
  278. command.
  279. You can also bake this behaviour into your build by hard-coding the
  280. environment variables if you add this to minnowmax.h:
  281. .. code-block:: c
  282. #undef CONFIG_BOOTCOMMAND
  283. #define CONFIG_BOOTCOMMAND \
  284. "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \
  285. "ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \
  286. "run boot"
  287. #undef CONFIG_EXTRA_ENV_SETTINGS
  288. #define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}"
  289. and change CONFIG_BOOTARGS value in configs/minnowmax_defconfig to::
  290. CONFIG_BOOTARGS="root=/dev/sda2 ro"
  291. Test with SeaBIOS
  292. -----------------
  293. `SeaBIOS`_ is an open source implementation of a 16-bit x86 BIOS. It can run
  294. in an emulator or natively on x86 hardware with the use of U-Boot. With its
  295. help, we can boot some OSes that require 16-bit BIOS services like Windows/DOS.
  296. As U-Boot, we have to manually create a table where SeaBIOS gets various system
  297. information (eg: E820) from. The table unfortunately has to follow the coreboot
  298. table format as SeaBIOS currently supports booting as a coreboot payload.
  299. To support loading SeaBIOS, U-Boot should be built with CONFIG_SEABIOS on.
  300. Booting SeaBIOS is done via U-Boot's bootelf command, like below::
  301. => tftp bios.bin.elf;bootelf
  302. Using e1000#0 device
  303. TFTP from server 10.10.0.100; our IP address is 10.10.0.108
  304. ...
  305. Bytes transferred = 122124 (1dd0c hex)
  306. ## Starting application at 0x000ff06e ...
  307. SeaBIOS (version rel-1.9.0)
  308. ...
  309. bios.bin.elf is the SeaBIOS image built from SeaBIOS source tree.
  310. Make sure it is built as follows::
  311. $ make menuconfig
  312. Inside the "General Features" menu, select "Build for coreboot" as the
  313. "Build Target". Inside the "Debugging" menu, turn on "Serial port debugging"
  314. so that we can see something as soon as SeaBIOS boots. Leave other options
  315. as in their default state. Then::
  316. $ make
  317. ...
  318. Total size: 121888 Fixed: 66496 Free: 9184 (used 93.0% of 128KiB rom)
  319. Creating out/bios.bin.elf
  320. Currently this is tested on QEMU x86 target with U-Boot chain-loading SeaBIOS
  321. to install/boot a Windows XP OS (below for example command to install Windows).
  322. .. code-block:: none
  323. # Create a 10G disk.img as the virtual hard disk
  324. $ qemu-img create -f qcow2 disk.img 10G
  325. # Install a Windows XP OS from an ISO image 'winxp.iso'
  326. $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -cdrom winxp.iso -smp 2 -m 512
  327. # Boot a Windows XP OS installed on the virutal hard disk
  328. $ qemu-system-i386 -serial stdio -bios u-boot.rom -hda disk.img -smp 2 -m 512
  329. This is also tested on Intel Crown Bay board with a PCIe graphics card, booting
  330. SeaBIOS then chain-loading a GRUB on a USB drive, then Linux kernel finally.
  331. If you are using Intel Integrated Graphics Device (IGD) as the primary display
  332. device on your board, SeaBIOS needs to be patched manually to get its VGA ROM
  333. loaded and run by SeaBIOS. SeaBIOS locates VGA ROM via the PCI expansion ROM
  334. register, but IGD device does not have its VGA ROM mapped by this register.
  335. Its VGA ROM is packaged as part of u-boot.rom at a configurable flash address
  336. which is unknown to SeaBIOS. An example patch is needed for SeaBIOS below:
  337. .. code-block:: none
  338. diff --git a/src/optionroms.c b/src/optionroms.c
  339. index 65f7fe0..c7b6f5e 100644
  340. --- a/src/optionroms.c
  341. +++ b/src/optionroms.c
  342. @@ -324,6 +324,8 @@ init_pcirom(struct pci_device *pci, int isvga, u64 *sources)
  343. rom = deploy_romfile(file);
  344. else if (RunPCIroms > 1 || (RunPCIroms == 1 && isvga))
  345. rom = map_pcirom(pci);
  346. + if (pci->bdf == pci_to_bdf(0, 2, 0))
  347. + rom = (struct rom_header *)0xfff90000;
  348. if (! rom)
  349. // No ROM present.
  350. return;
  351. Note: the patch above expects IGD device is at PCI b.d.f 0.2.0 and its VGA ROM
  352. is at 0xfff90000 which corresponds to CONFIG_VGA_BIOS_ADDR on Minnowboard MAX.
  353. Change these two accordingly if this is not the case on your board.
  354. Development Flow
  355. ----------------
  356. These notes are for those who want to port U-Boot to a new x86 platform.
  357. Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment.
  358. The Dediprog em100 can be used on Linux.
  359. The em100 tool is available here: http://review.coreboot.org/p/em100.git
  360. On Minnowboard Max the following command line can be used::
  361. sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r
  362. A suitable clip for connecting over the SPI flash chip is here:
  363. http://www.dediprog.com/pd/programmer-accessories/EM-TC-8.
  364. This allows you to override the SPI flash contents for development purposes.
  365. Typically you can write to the em100 in around 1200ms, considerably faster
  366. than programming the real flash device each time. The only important
  367. limitation of the em100 is that it only supports SPI bus speeds up to 20MHz.
  368. This means that images must be set to boot with that speed. This is an
  369. Intel-specific feature - e.g. tools/ifttool has an option to set the SPI
  370. speed in the SPI descriptor region.
  371. If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly
  372. easy to fit it in. You can follow the Minnowboard Max implementation, for
  373. example. Hopefully you will just need to create new files similar to those
  374. in arch/x86/cpu/baytrail which provide Bay Trail support.
  375. If you are not using an FSP you have more freedom and more responsibility.
  376. The ivybridge support works this way, although it still uses a ROM for
  377. graphics and still has binary blobs containing Intel code. You should aim to
  378. support all important peripherals on your platform including video and storage.
  379. Use the device tree for configuration where possible.
  380. For the microcode you can create a suitable device tree file using the
  381. microcode tool::
  382. ./tools/microcode-tool -d microcode.dat -m <model> create
  383. or if you only have header files and not the full Intel microcode.dat database::
  384. ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \
  385. -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h -m all create
  386. These are written to arch/x86/dts/microcode/ by default.
  387. Note that it is possible to just add the micrcode for your CPU if you know its
  388. model. U-Boot prints this information when it starts::
  389. CPU: x86_64, vendor Intel, device 30673h
  390. so here we can use the M0130673322 file.
  391. If you platform can display POST codes on two little 7-segment displays on
  392. the board, then you can use post_code() calls from C or assembler to monitor
  393. boot progress. This can be good for debugging.
  394. If not, you can try to get serial working as early as possible. The early
  395. debug serial port may be useful here. See setup_internal_uart() for an example.
  396. During the U-Boot porting, one of the important steps is to write correct PIRQ
  397. routing information in the board device tree. Without it, device drivers in the
  398. Linux kernel won't function correctly due to interrupt is not working. Please
  399. refer to U-Boot `doc <doc/device-tree-bindings/misc/intel,irq-router.txt>`_ for
  400. the device tree bindings of Intel interrupt router. Here we have more details
  401. on the intel,pirq-routing property below.
  402. .. code-block:: none
  403. intel,pirq-routing = <
  404. PCI_BDF(0, 2, 0) INTA PIRQA
  405. ...
  406. >;
  407. As you see each entry has 3 cells. For the first one, we need describe all pci
  408. devices mounted on the board. For SoC devices, normally there is a chapter on
  409. the chipset datasheet which lists all the available PCI devices. For example on
  410. Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we
  411. can get the interrupt pin either from datasheet or hardware via U-Boot shell.
  412. The reliable source is the hardware as sometimes chipset datasheet is not 100%
  413. up-to-date. Type 'pci header' plus the device's pci bus/device/function number
  414. from U-Boot shell below::
  415. => pci header 0.1e.1
  416. vendor ID = 0x8086
  417. device ID = 0x0f08
  418. ...
  419. interrupt line = 0x09
  420. interrupt pin = 0x04
  421. ...
  422. It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin
  423. register. Repeat this until you get interrupt pins for all the devices. The last
  424. cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel
  425. chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This
  426. can be changed by registers in LPC bridge. So far Intel FSP does not touch those
  427. registers so we can write down the PIRQ according to the default mapping rule.
  428. Once we get the PIRQ routing information in the device tree, the interrupt
  429. allocation and assignment will be done by U-Boot automatically. Now you can
  430. enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and
  431. CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC.
  432. This script might be useful. If you feed it the output of 'pci long' from
  433. U-Boot then it will generate a device tree fragment with the interrupt
  434. configuration for each device (note it needs gawk 4.0.0)::
  435. $ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \
  436. /interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \
  437. {patsplit(device, bdf, "[0-9a-f]+"); \
  438. printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \
  439. strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}'
  440. Example output::
  441. PCI_BDF(0, 2, 0) INTA PIRQA
  442. PCI_BDF(0, 3, 0) INTA PIRQA
  443. ...
  444. Porting Hints
  445. -------------
  446. Quark-specific considerations
  447. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  448. To port U-Boot to other boards based on the Intel Quark SoC, a few things need
  449. to be taken care of. The first important part is the Memory Reference Code (MRC)
  450. parameters. Quark MRC supports memory-down configuration only. All these MRC
  451. parameters are supplied via the board device tree. To get started, first copy
  452. the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then
  453. change these values by consulting board manuals or your hardware vendor.
  454. Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h.
  455. The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports,
  456. but by default they are held in reset after power on. In U-Boot, PCIe
  457. initialization is properly handled as per Quark's firmware writer guide.
  458. In your board support codes, you need provide two routines to aid PCIe
  459. initialization, which are board_assert_perst() and board_deassert_perst().
  460. The two routines need implement a board-specific mechanism to assert/deassert
  461. PCIe PERST# pin. Care must be taken that in those routines that any APIs that
  462. may trigger PCI enumeration process are strictly forbidden, as any access to
  463. PCIe root port's configuration registers will cause system hang while it is
  464. held in reset. For more details, check how they are implemented by the Intel
  465. Galileo board support codes in board/intel/galileo/galileo.c.
  466. coreboot
  467. ^^^^^^^^
  468. See scripts/coreboot.sed which can assist with porting coreboot code into
  469. U-Boot drivers. It will not resolve all build errors, but will perform common
  470. transformations. Remember to add attribution to coreboot for new files added
  471. to U-Boot. This should go at the top of each file and list the coreboot
  472. filename where the code originated.
  473. Debugging ACPI issues with Windows
  474. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  475. Windows might cache system information and only detect ACPI changes if you
  476. modify the ACPI table versions. So tweak them liberally when debugging ACPI
  477. issues with Windows.
  478. ACPI Support Status
  479. -------------------
  480. Advanced Configuration and Power Interface (`ACPI`_) aims to establish
  481. industry-standard interfaces enabling OS-directed configuration, power
  482. management, and thermal management of mobile, desktop, and server platforms.
  483. Linux can boot without ACPI with "acpi=off" command line parameter, but
  484. with ACPI the kernel gains the capabilities to handle power management.
  485. For Windows, ACPI is a must-have firmware feature since Windows Vista.
  486. CONFIG_GENERATE_ACPI_TABLE is the config option to turn on ACPI support in
  487. U-Boot. This requires Intel ACPI compiler to be installed on your host to
  488. compile ACPI DSDT table written in ASL format to AML format. You can get
  489. the compiler via "apt-get install iasl" if you are on Ubuntu or download
  490. the source from https://www.acpica.org/downloads to compile one by yourself.
  491. Current ACPI support in U-Boot is basically complete. More optional features
  492. can be added in the future. The status as of today is:
  493. * Support generating RSDT, XSDT, FACS, FADT, MADT, MCFG tables.
  494. * Support one static DSDT table only, compiled by Intel ACPI compiler.
  495. * Support S0/S3/S4/S5, reboot and shutdown from OS.
  496. * Support booting a pre-installed Ubuntu distribution via 'zboot' command.
  497. * Support installing and booting Ubuntu 14.04 (or above) from U-Boot with
  498. the help of SeaBIOS using legacy interface (non-UEFI mode).
  499. * Support installing and booting Windows 8.1/10 from U-Boot with the help
  500. of SeaBIOS using legacy interface (non-UEFI mode).
  501. * Support ACPI interrupts with SCI only.
  502. Features that are optional:
  503. * Dynamic AML bytecodes insertion at run-time. We may need this to support
  504. SSDT table generation and DSDT fix up.
  505. * SMI support. Since U-Boot is a modern bootloader, we don't want to bring
  506. those legacy stuff into U-Boot. ACPI spec allows a system that does not
  507. support SMI (a legacy-free system).
  508. ACPI was initially enabled on BayTrail based boards. Testing was done by booting
  509. a pre-installed Ubuntu 14.04 from a SATA drive. Installing Ubuntu 14.04 and
  510. Windows 8.1/10 to a SATA drive and booting from there is also tested. Most
  511. devices seem to work correctly and the board can respond a reboot/shutdown
  512. command from the OS.
  513. For other platform boards, ACPI support status can be checked by examining their
  514. board defconfig files to see if CONFIG_GENERATE_ACPI_TABLE is set to y.
  515. The S3 sleeping state is a low wake latency sleeping state defined by ACPI
  516. spec where all system context is lost except system memory. To test S3 resume
  517. with a Linux kernel, simply run "echo mem > /sys/power/state" and kernel will
  518. put the board to S3 state where the power is off. So when the power button is
  519. pressed again, U-Boot runs as it does in cold boot and detects the sleeping
  520. state via ACPI register to see if it is S3, if yes it means we are waking up.
  521. U-Boot is responsible for restoring the machine state as it is before sleep.
  522. When everything is done, U-Boot finds out the wakeup vector provided by OSes
  523. and jump there. To determine whether ACPI S3 resume is supported, check to
  524. see if CONFIG_HAVE_ACPI_RESUME is set for that specific board.
  525. Note for testing S3 resume with Windows, correct graphics driver must be
  526. installed for your platform, otherwise you won't find "Sleep" option in
  527. the "Power" submenu from the Windows start menu.
  528. EFI Support
  529. -----------
  530. U-Boot supports booting as a 32-bit or 64-bit EFI payload, e.g. with UEFI.
  531. This is enabled with CONFIG_EFI_STUB to boot from both 32-bit and 64-bit
  532. UEFI BIOS. U-Boot can also run as an EFI application, with CONFIG_EFI_APP.
  533. The CONFIG_EFI_LOADER option, where U-Boot provides an EFI environment to
  534. the kernel (i.e. replaces UEFI completely but provides the same EFI run-time
  535. services) is supported too. For example, we can even use 'bootefi' command
  536. to load a 'u-boot-payload.efi', see below test logs on QEMU.
  537. .. code-block:: none
  538. => load ide 0 3000000 u-boot-payload.efi
  539. 489787 bytes read in 138 ms (3.4 MiB/s)
  540. => bootefi 3000000
  541. Scanning disk ide.blk#0...
  542. Found 2 disks
  543. WARNING: booting without device tree
  544. ## Starting EFI application at 03000000 ...
  545. U-Boot EFI Payload
  546. U-Boot 2018.07-rc2 (Jun 23 2018 - 17:12:58 +0800)
  547. CPU: x86_64, vendor AMD, device 663h
  548. DRAM: 2 GiB
  549. MMC:
  550. Video: 1024x768x32
  551. Model: EFI x86 Payload
  552. Net: e1000: 52:54:00:12:34:56
  553. Warning: e1000#0 using MAC address from ROM
  554. eth0: e1000#0
  555. No controllers found
  556. Hit any key to stop autoboot: 0
  557. See :doc:`../develop/uefi/u-boot_on_efi` and :doc:`../develop/uefi/uefi` for
  558. details of EFI support in U-Boot.
  559. Chain-loading
  560. -------------
  561. U-Boot can be chain-loaded from another bootloader, such as coreboot or
  562. Slim Bootloader. Typically this is done by building for targets 'coreboot' or
  563. 'slimbootloader'.
  564. For example, at present we have a 'coreboot' target but this runs very
  565. different code from the bare-metal targets, such as coral. There is very little
  566. in common between them.
  567. It is useful to be able to boot the same U-Boot on a device, with or without a
  568. first-stage bootloader. For example, with chromebook_coral, it is helpful for
  569. testing to be able to boot the same U-Boot (complete with FSP) on bare metal
  570. and from coreboot. It allows checking of things like CPU speed, comparing
  571. registers, ACPI tables and the like.
  572. To do this you can use ll_boot_init() in appropriate places to skip init that
  573. has already been done by the previous stage. This works by setting a
  574. GD_FLG_NO_LL_INIT flag when U-Boot detects that it is running from another
  575. bootloader.
  576. With this feature, you can build a bare-metal target and boot it from
  577. coreboot, for example.
  578. Note that this is a development feature only. It is not intended for use in
  579. production environments. Also it is not currently part of the automated tests
  580. so may break in the future.
  581. SMBIOS tables
  582. -------------
  583. To generate SMBIOS tables in U-Boot, for use by the OS, enable the
  584. CONFIG_GENERATE_SMBIOS_TABLE option. The easiest way to provide the values to
  585. use is via the device tree. For details see
  586. device-tree-bindings/sysinfo/smbios.txt
  587. TODO List
  588. ---------
  589. - Audio
  590. - Chrome OS verified boot
  591. .. _coreboot: http://www.coreboot.org
  592. .. _QEMU: http://www.qemu.org
  593. .. _microcode: http://en.wikipedia.org/wiki/Microcode
  594. .. _SFI: http://simplefirmware.org
  595. .. _MP: http://www.intel.com/design/archives/processors/pro/docs/242016.htm
  596. .. _here: https://en.wikipedia.org/wiki/GUID_Partition_Table
  597. .. _this: http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf
  598. .. _that: http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf
  599. .. _SeaBIOS: http://www.seabios.org/SeaBIOS
  600. .. _ACPI: http://www.acpi.info