1# 2# Copyright (C) 2014, Simon Glass <sjg@chromium.org> 3# Copyright (C) 2014, Bin Meng <bmeng.cn@gmail.com> 4# 5# SPDX-License-Identifier: GPL-2.0+ 6# 7 8U-Boot on x86 9============= 10 11This document describes the information about U-Boot running on x86 targets, 12including supported boards, build instructions, todo list, etc. 13 14Status 15------ 16U-Boot supports running as a coreboot [1] payload on x86. So far only Link 17(Chromebook Pixel) and QEMU [2] x86 targets have been tested, but it should 18work with minimal adjustments on other x86 boards since coreboot deals with 19most of the low-level details. 20 21U-Boot also supports booting directly from x86 reset vector without coreboot, 22aka raw support or bare support. Currently Link, QEMU x86 targets and all 23Intel boards support running U-Boot 'bare metal'. 24 25As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit 26Linux kernel as part of a FIT image. It also supports a compressed zImage. 27 28Build Instructions 29------------------ 30Building U-Boot as a coreboot payload is just like building U-Boot for targets 31on other architectures, like below: 32 33$ make coreboot-x86_defconfig 34$ make all 35 36Note this default configuration will build a U-Boot payload for the QEMU board. 37To build a coreboot payload against another board, you can change the build 38configuration during the 'make menuconfig' process. 39 40x86 architecture ---> 41 ... 42 (qemu-x86) Board configuration file 43 (qemu-x86_i440fx) Board Device Tree Source (dts) file 44 (0x01920000) Board specific Cache-As-RAM (CAR) address 45 (0x4000) Board specific Cache-As-RAM (CAR) size 46 47Change the 'Board configuration file' and 'Board Device Tree Source (dts) file' 48to point to a new board. You can also change the Cache-As-RAM (CAR) related 49settings here if the default values do not fit your new board. 50 51Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a 52little bit tricky, as generally it requires several binary blobs which are not 53shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build is 54not turned on by default in the U-Boot source tree. Firstly, you need turn it 55on by enabling the ROM build: 56 57$ export BUILD_ROM=y 58 59This tells the Makefile to build u-boot.rom as a target. 60 61Link-specific instructions: 62 63First, you need the following binary blobs: 64 65* descriptor.bin - Intel flash descriptor 66* me.bin - Intel Management Engine 67* mrc.bin - Memory Reference Code, which sets up SDRAM 68* video ROM - sets up the display 69 70You can get these binary blobs by: 71 72$ git clone http://review.coreboot.org/p/blobs.git 73$ cd blobs 74 75Find the following files: 76 77* ./mainboard/google/link/descriptor.bin 78* ./mainboard/google/link/me.bin 79* ./northbridge/intel/sandybridge/systemagent-r6.bin 80 81The 3rd one should be renamed to mrc.bin. 82As for the video ROM, you can get it here [3] and rename it to vga.bin. 83Make sure all these binary blobs are put in the board directory. 84 85Now you can build U-Boot and obtain u-boot.rom: 86 87$ make chromebook_link_defconfig 88$ make all 89 90Intel Crown Bay specific instructions: 91 92U-Boot support of Intel Crown Bay board [4] relies on a binary blob called 93Firmware Support Package [5] to perform all the necessary initialization steps 94as documented in the BIOS Writer Guide, including initialization of the CPU, 95memory controller, chipset and certain bus interfaces. 96 97Download the Intel FSP for Atom E6xx series and Platform Controller Hub EG20T, 98install it on your host and locate the FSP binary blob. Note this platform 99also requires a Chipset Micro Code (CMC) state machine binary to be present in 100the SPI flash where u-boot.rom resides, and this CMC binary blob can be found 101in this FSP package too. 102 103* ./FSP/QUEENSBAY_FSP_GOLD_001_20-DECEMBER-2013.fd 104* ./Microcode/C0_22211.BIN 105 106Rename the first one to fsp.bin and second one to cmc.bin and put them in the 107board directory. 108 109Note the FSP release version 001 has a bug which could cause random endless 110loop during the FspInit call. This bug was published by Intel although Intel 111did not describe any details. We need manually apply the patch to the FSP 112binary using any hex editor (eg: bvi). Go to the offset 0x1fcd8 of the FSP 113binary, change the following five bytes values from orginally E8 42 FF FF FF 114to B8 00 80 0B 00. 115 116As for the video ROM, you need manually extract it from the Intel provided 117BIOS for Crown Bay here [6], using the AMI MMTool [7]. Check PCI option ROM 118ID 8086:4108, extract and save it as vga.bin in the board directory. 119 120Now you can build U-Boot and obtain u-boot.rom 121 122$ make crownbay_defconfig 123$ make all 124 125Intel Minnowboard Max instructions: 126 127This uses as FSP as with Crown Bay, except it is for the Atom E3800 series. 128Download this and get the .fd file (BAYTRAIL_FSP_GOLD_003_16-SEP-2014.fd at 129the time of writing). Put it in the board directory: 130board/intel/minnowmax/fsp.bin 131 132Obtain the VGA RAM (Vga.dat at the time of writing) and put it into the same 133directory: board/intel/minnowmax/vga.bin 134 135You still need two more binary blobs. The first comes from the original 136firmware image available from: 137 138http://firmware.intel.com/sites/default/files/2014-WW42.4-MinnowBoardMax.73-64-bit.bin_Release.zip 139 140Unzip it: 141 142 $ unzip 2014-WW42.4-MinnowBoardMax.73-64-bit.bin_Release.zip 143 144Use ifdtool in the U-Boot tools directory to extract the images from that 145file, for example: 146 147 $ ./tools/ifdtool -x MNW2MAX1.X64.0073.R02.1409160934.bin 148 149This will provide the descriptor file - copy this into the correct place: 150 151 $ cp flashregion_0_flashdescriptor.bin board/intel/minnowmax/descriptor.bin 152 153Then do the same with the sample SPI image provided in the FSP (SPI.bin at 154the time of writing) to obtain the last image. Note that this will also 155produce a flash descriptor file, but it does not seem to work, probably 156because it is not designed for the Minnowmax. That is why you need to get 157the flash descriptor from the original firmware as above. 158 159 $ ./tools/ifdtool -x BayleyBay/SPI.bin 160 $ cp flashregion_2_intel_me.bin board/intel/minnowmax/me.bin 161 162Now you can build U-Boot and obtain u-boot.rom 163 164$ make minnowmax_defconfig 165$ make all 166 167Checksums are as follows (but note that newer versions will invalidate this): 168 169$ md5sum -b board/intel/minnowmax/*.bin 170ffda9a3b94df5b74323afb328d51e6b4 board/intel/minnowmax/descriptor.bin 17169f65b9a580246291d20d08cbef9d7c5 board/intel/minnowmax/fsp.bin 172894a97d371544ec21de9c3e8e1716c4b board/intel/minnowmax/me.bin 173a2588537da387da592a27219d56e9962 board/intel/minnowmax/vga.bin 174 175The ROM image is broken up into these parts: 176 177Offset Description Controlling config 178------------------------------------------------------------ 179000000 descriptor.bin Hard-coded to 0 in ifdtool 180001000 me.bin Set by the descriptor 181500000 <spare> 182700000 u-boot-dtb.bin CONFIG_SYS_TEXT_BASE 183790000 vga.bin CONFIG_X86_OPTION_ROM_ADDR 1847c0000 fsp.bin CONFIG_FSP_ADDR 1857f8000 <spare> (depends on size of fsp.bin) 1867fe000 Environment CONFIG_ENV_OFFSET 1877ff800 U-Boot 16-bit boot CONFIG_SYS_X86_START16 188 189Overall ROM image size is controlled by CONFIG_ROM_SIZE. 190 191 192Intel Galileo instructions: 193 194Only one binary blob is needed for Remote Management Unit (RMU) within Intel 195Quark SoC. Not like FSP, U-Boot does not call into the binary. The binary is 196needed by the Quark SoC itself. 197 198You can get the binary blob from Quark Board Support Package from Intel website: 199 200* ./QuarkSocPkg/QuarkNorthCluster/Binary/QuarkMicrocode/RMU.bin 201 202Rename the file and put it to the board directory by: 203 204 $ cp RMU.bin board/intel/galileo/rmu.bin 205 206Now you can build U-Boot and obtain u-boot.rom 207 208$ make galileo_defconfig 209$ make all 210 211QEMU x86 target instructions: 212 213To build u-boot.rom for QEMU x86 targets, just simply run 214 215$ make qemu-x86_defconfig 216$ make all 217 218Note this default configuration will build a U-Boot for the QEMU x86 i440FX 219board. To build a U-Boot against QEMU x86 Q35 board, you can change the build 220configuration during the 'make menuconfig' process like below: 221 222Device Tree Control ---> 223 ... 224 (qemu-x86_q35) Default Device Tree for DT control 225 226Test with coreboot 227------------------ 228For testing U-Boot as the coreboot payload, there are things that need be paid 229attention to. coreboot supports loading an ELF executable and a 32-bit plain 230binary, as well as other supported payloads. With the default configuration, 231U-Boot is set up to use a separate Device Tree Blob (dtb). As of today, the 232generated u-boot-dtb.bin needs to be packaged by the cbfstool utility (a tool 233provided by coreboot) manually as coreboot's 'make menuconfig' does not provide 234this capability yet. The command is as follows: 235 236# in the coreboot root directory 237$ ./build/util/cbfstool/cbfstool build/coreboot.rom add-flat-binary \ 238 -f u-boot-dtb.bin -n fallback/payload -c lzma -l 0x1110000 -e 0x1110015 239 240Make sure 0x1110000 matches CONFIG_SYS_TEXT_BASE and 0x1110015 matches the 241symbol address of _start (in arch/x86/cpu/start.S). 242 243If you want to use ELF as the coreboot payload, change U-Boot configuration to 244use CONFIG_OF_EMBED instead of CONFIG_OF_SEPARATE. 245 246To enable video you must enable these options in coreboot: 247 248 - Set framebuffer graphics resolution (1280x1024 32k-color (1:5:5)) 249 - Keep VESA framebuffer 250 251At present it seems that for Minnowboard Max, coreboot does not pass through 252the video information correctly (it always says the resolution is 0x0). This 253works correctly for link though. 254 255Test with QEMU 256-------------- 257QEMU is a fancy emulator that can enable us to test U-Boot without access to 258a real x86 board. Please make sure your QEMU version is 2.3.0 or above test 259U-Boot. To launch QEMU with u-boot.rom, call QEMU as follows: 260 261$ qemu-system-i386 -nographic -bios path/to/u-boot.rom 262 263This will instantiate an emulated x86 board with i440FX and PIIX chipset. QEMU 264also supports emulating an x86 board with Q35 and ICH9 based chipset, which is 265also supported by U-Boot. To instantiate such a machine, call QEMU with: 266 267$ qemu-system-i386 -nographic -bios path/to/u-boot.rom -M q35 268 269Note by default QEMU instantiated boards only have 128 MiB system memory. But 270it is enough to have U-Boot boot and function correctly. You can increase the 271system memory by pass '-m' parameter to QEMU if you want more memory: 272 273$ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024 274 275This creates a board with 1 GiB system memory. Currently U-Boot for QEMU only 276supports 3 GiB maximum system memory and reserves the last 1 GiB address space 277for PCI device memory-mapped I/O and other stuff, so the maximum value of '-m' 278would be 3072. 279 280QEMU emulates a graphic card which U-Boot supports. Removing '-nographic' will 281show QEMU's VGA console window. Note this will disable QEMU's serial output. 282If you want to check both consoles, use '-serial stdio'. 283 284Multicore is also supported by QEMU via '-smp n' where n is the number of cores 285to instantiate. Currently the default U-Boot built for QEMU supports 2 cores. 286In order to support more cores, you need add additional cpu nodes in the device 287tree and change CONFIG_MAX_CPUS accordingly. 288 289CPU Microcode 290------------- 291Modern CPUs usually require a special bit stream called microcode [8] to be 292loaded on the processor after power up in order to function properly. U-Boot 293has already integrated these as hex dumps in the source tree. 294 295SMP Support 296----------- 297On a multicore system, U-Boot is executed on the bootstrap processor (BSP). 298Additional application processors (AP) can be brought up by U-Boot. In order to 299have an SMP kernel to discover all of the available processors, U-Boot needs to 300prepare configuration tables which contain the multi-CPUs information before 301loading the OS kernel. Currently U-Boot supports generating two types of tables 302for SMP, called Simple Firmware Interface (SFI) [9] and Multi-Processor (MP) 303[10] tables. The writing of these two tables are controlled by two Kconfig 304options GENERATE_SFI_TABLE and GENERATE_MP_TABLE. 305 306Driver Model 307------------ 308x86 has been converted to use driver model for serial and GPIO. 309 310Device Tree 311----------- 312x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to 313be turned on. Not every device on the board is configured via device tree, but 314more and more devices will be added as time goes by. Check out the directory 315arch/x86/dts/ for these device tree source files. 316 317Useful Commands 318--------------- 319In keeping with the U-Boot philosophy of providing functions to check and 320adjust internal settings, there are several x86-specific commands that may be 321useful: 322 323hob - Display information about Firmware Support Package (FSP) Hand-off 324 Block. This is only available on platforms which use FSP, mostly 325 Atom. 326iod - Display I/O memory 327iow - Write I/O memory 328mtrr - List and set the Memory Type Range Registers (MTRR). These are used to 329 tell the CPU whether memory is cacheable and if so the cache write 330 mode to use. U-Boot sets up some reasonable values but you can 331 adjust then with this command. 332 333Booting Ubuntu 334-------------- 335As an example of how to set up your boot flow with U-Boot, here are 336instructions for starting Ubuntu from U-Boot. These instructions have been 337tested on Minnowboard MAX with a SATA driver but are equally applicable on 338other platforms and other media. There are really only four steps and its a 339very simple script, but a more detailed explanation is provided here for 340completeness. 341 342Note: It is possible to set up U-Boot to boot automatically using syslinux. 343It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the 344GUID. If you figure these out, please post patches to this README. 345 346Firstly, you will need Ubunutu installed on an available disk. It should be 347possible to make U-Boot start a USB start-up disk but for now let's assume 348that you used another boot loader to install Ubuntu. 349 350Use the U-Boot command line to find the UUID of the partition you want to 351boot. For example our disk is SCSI device 0: 352 353=> part list scsi 0 354 355Partition Map for SCSI device 0 -- Partition Type: EFI 356 357 Part Start LBA End LBA Name 358 Attributes 359 Type GUID 360 Partition GUID 361 1 0x00000800 0x001007ff "" 362 attrs: 0x0000000000000000 363 type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b 364 guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c 365 2 0x00100800 0x037d8fff "" 366 attrs: 0x0000000000000000 367 type: 0fc63daf-8483-4772-8e79-3d69d8477de4 368 guid: 965c59ee-1822-4326-90d2-b02446050059 369 3 0x037d9000 0x03ba27ff "" 370 attrs: 0x0000000000000000 371 type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f 372 guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17 373 => 374 375This shows that your SCSI disk has three partitions. The really long hex 376strings are called Globally Unique Identifiers (GUIDs). You can look up the 377'type' ones here [11]. On this disk the first partition is for EFI and is in 378VFAT format (DOS/Windows): 379 380 => fatls scsi 0:1 381 efi/ 382 383 0 file(s), 1 dir(s) 384 385 386Partition 2 is 'Linux filesystem data' so that will be our root disk. It is 387in ext2 format: 388 389 => ext2ls scsi 0:2 390 <DIR> 4096 . 391 <DIR> 4096 .. 392 <DIR> 16384 lost+found 393 <DIR> 4096 boot 394 <DIR> 12288 etc 395 <DIR> 4096 media 396 <DIR> 4096 bin 397 <DIR> 4096 dev 398 <DIR> 4096 home 399 <DIR> 4096 lib 400 <DIR> 4096 lib64 401 <DIR> 4096 mnt 402 <DIR> 4096 opt 403 <DIR> 4096 proc 404 <DIR> 4096 root 405 <DIR> 4096 run 406 <DIR> 12288 sbin 407 <DIR> 4096 srv 408 <DIR> 4096 sys 409 <DIR> 4096 tmp 410 <DIR> 4096 usr 411 <DIR> 4096 var 412 <SYM> 33 initrd.img 413 <SYM> 30 vmlinuz 414 <DIR> 4096 cdrom 415 <SYM> 33 initrd.img.old 416 => 417 418and if you look in the /boot directory you will see the kernel: 419 420 => ext2ls scsi 0:2 /boot 421 <DIR> 4096 . 422 <DIR> 4096 .. 423 <DIR> 4096 efi 424 <DIR> 4096 grub 425 3381262 System.map-3.13.0-32-generic 426 1162712 abi-3.13.0-32-generic 427 165611 config-3.13.0-32-generic 428 176500 memtest86+.bin 429 178176 memtest86+.elf 430 178680 memtest86+_multiboot.bin 431 5798112 vmlinuz-3.13.0-32-generic 432 165762 config-3.13.0-58-generic 433 1165129 abi-3.13.0-58-generic 434 5823136 vmlinuz-3.13.0-58-generic 435 19215259 initrd.img-3.13.0-58-generic 436 3391763 System.map-3.13.0-58-generic 437 5825048 vmlinuz-3.13.0-58-generic.efi.signed 438 28304443 initrd.img-3.13.0-32-generic 439 => 440 441The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of 442self-extracting compressed file mixed with some 'setup' configuration data. 443Despite its size (uncompressed it is >10MB) this only includes a basic set of 444device drivers, enough to boot on most hardware types. 445 446The 'initrd' files contain a RAM disk. This is something that can be loaded 447into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots 448of drivers for whatever hardware you might have. It is loaded before the 449real root disk is accessed. 450 451The numbers after the end of each file are the version. Here it is Linux 452version 3.13. You can find the source code for this in the Linux tree with 453the tag v3.13. The '.0' allows for additional Linux releases to fix problems, 454but normally this is not needed. The '-58' is used by Ubuntu. Each time they 455release a new kernel they increment this number. New Ubuntu versions might 456include kernel patches to fix reported bugs. Stable kernels can exist for 457some years so this number can get quite high. 458 459The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own 460secure boot mechanism - see [12] [13] and cannot read .efi files at present. 461 462To boot Ubuntu from U-Boot the steps are as follows: 463 4641. Set up the boot arguments. Use the GUID for the partition you want to 465boot: 466 467 => setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro 468 469Here root= tells Linux the location of its root disk. The disk is specified 470by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory' 471containing all the GUIDs Linux has found. When it starts up, there will be a 472file in that directory with this name in it. It is also possible to use a 473device name here, see later. 474 4752. Load the kernel. Since it is an ext2/4 filesystem we can do: 476 477 => ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic 478 479The address 30000000 is arbitrary, but there seem to be problems with using 480small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into 481the start of RAM (which is at 0 on x86). 482 4833. Load the ramdisk (to 64MB): 484 485 => ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic 486 4874. Start up the kernel. We need to know the size of the ramdisk, but can use 488a variable for that. U-Boot sets 'filesize' to the size of the last file it 489loaded. 490 491 => zboot 03000000 0 04000000 ${filesize} 492 493Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is 494quite verbose when it boots a kernel. You should see these messages from 495U-Boot: 496 497 Valid Boot Flag 498 Setup Size = 0x00004400 499 Magic signature found 500 Using boot protocol version 2.0c 501 Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015 502 Building boot_params at 0x00090000 503 Loading bzImage at address 100000 (5805728 bytes) 504 Magic signature found 505 Initial RAM disk at linear address 0x04000000, size 19215259 bytes 506 Kernel command line: "console=ttyS0,115200 root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro" 507 508 Starting kernel ... 509 510U-Boot prints out some bootstage timing. This is more useful if you put the 511above commands into a script since then it will be faster. 512 513 Timer summary in microseconds: 514 Mark Elapsed Stage 515 0 0 reset 516 241,535 241,535 board_init_r 517 2,421,611 2,180,076 id=64 518 2,421,790 179 id=65 519 2,428,215 6,425 main_loop 520 48,860,584 46,432,369 start_kernel 521 522 Accumulated time: 523 240,329 ahci 524 1,422,704 vesa display 525 526Now the kernel actually starts: 527 528 [ 0.000000] Initializing cgroup subsys cpuset 529 [ 0.000000] Initializing cgroup subsys cpu 530 [ 0.000000] Initializing cgroup subsys cpuacct 531 [ 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) 532 [ 0.000000] Command line: console=ttyS0,115200 root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro 533 534It continues for a long time. Along the way you will see it pick up your 535ramdisk: 536 537 [ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff] 538... 539 [ 0.788540] Trying to unpack rootfs image as initramfs... 540 [ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000) 541... 542 543Later it actually starts using it: 544 545 Begin: Running /scripts/local-premount ... done. 546 547You should also see your boot disk turn up: 548 549 [ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5 550 [ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB) 551 [ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0 552 [ 4.381859] sd 1:0:0:0: [sda] Write Protect is off 553 [ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA 554 [ 4.399535] sda: sda1 sda2 sda3 555 556Linux has found the three partitions (sda1-3). Mercifully it doesn't print out 557the GUIDs. In step 1 above we could have used: 558 559 setenv bootargs root=/dev/sda2 ro 560 561instead of the GUID. However if you add another drive to your board the 562numbering may change whereas the GUIDs will not. So if your boot partition 563becomes sdb2, it will still boot. For embedded systems where you just want to 564boot the first disk, you have that option. 565 566The last thing you will see on the console is mention of plymouth (which 567displays the Ubuntu start-up screen) and a lot of 'Starting' messages: 568 569 * Starting Mount filesystems on boot [ OK ] 570 571After a pause you should see a login screen on your display and you are done. 572 573If you want to put this in a script you can use something like this: 574 575 setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro 576 setenv boot zboot 03000000 0 04000000 \${filesize} 577 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" 578 saveenv 579 580The \ is to tell the shell not to evaluate ${filesize} as part of the setenv 581command. 582 583You will also need to add this to your board configuration file, e.g. 584include/configs/minnowmax.h: 585 586 #define CONFIG_BOOTDELAY 2 587 588Now when you reset your board it wait a few seconds (in case you want to 589interrupt) and then should boot straight into Ubuntu. 590 591You can also bake this behaviour into your build by hard-coding the 592environment variables if you add this to minnowmax.h: 593 594#undef CONFIG_BOOTARGS 595#undef CONFIG_BOOTCOMMAND 596 597#define CONFIG_BOOTARGS \ 598 "root=/dev/sda2 ro" 599#define CONFIG_BOOTCOMMAND \ 600 "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \ 601 "ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \ 602 "run boot" 603 604#undef CONFIG_EXTRA_ENV_SETTINGS 605#define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}" 606 607 608Development Flow 609---------------- 610These notes are for those who want to port U-Boot to a new x86 platform. 611 612Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment. 613The Dediprog em100 can be used on Linux. The em100 tool is available here: 614 615 http://review.coreboot.org/p/em100.git 616 617On Minnowboard Max the following command line can be used: 618 619 sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r 620 621A suitable clip for connecting over the SPI flash chip is here: 622 623 http://www.dediprog.com/pd/programmer-accessories/EM-TC-8 624 625This allows you to override the SPI flash contents for development purposes. 626Typically you can write to the em100 in around 1200ms, considerably faster 627than programming the real flash device each time. The only important 628limitation of the em100 is that it only supports SPI bus speeds up to 20MHz. 629This means that images must be set to boot with that speed. This is an 630Intel-specific feature - e.g. tools/ifttool has an option to set the SPI 631speed in the SPI descriptor region. 632 633If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly 634easy to fit it in. You can follow the Minnowboard Max implementation, for 635example. Hopefully you will just need to create new files similar to those 636in arch/x86/cpu/baytrail which provide Bay Trail support. 637 638If you are not using an FSP you have more freedom and more responsibility. 639The ivybridge support works this way, although it still uses a ROM for 640graphics and still has binary blobs containing Intel code. You should aim to 641support all important peripherals on your platform including video and storage. 642Use the device tree for configuration where possible. 643 644For the microcode you can create a suitable device tree file using the 645microcode tool: 646 647 ./tools/microcode-tool -d microcode.dat create <model> 648 649or if you only have header files and not the full Intel microcode.dat database: 650 651 ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \ 652 -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h \ 653 create all 654 655These are written to arch/x86/dts/microcode/ by default. 656 657Note that it is possible to just add the micrcode for your CPU if you know its 658model. U-Boot prints this information when it starts 659 660 CPU: x86_64, vendor Intel, device 30673h 661 662so here we can use the M0130673322 file. 663 664If you platform can display POST codes on two little 7-segment displays on 665the board, then you can use post_code() calls from C or assembler to monitor 666boot progress. This can be good for debugging. 667 668If not, you can try to get serial working as early as possible. The early 669debug serial port may be useful here. See setup_early_uart() for an example. 670 671During the U-Boot porting, one of the important steps is to write correct PIRQ 672routing information in the board device tree. Without it, device drivers in the 673Linux kernel won't function correctly due to interrupt is not working. Please 674refer to U-Boot doc [14] for the device tree bindings of Intel interrupt router. 675Here we have more details on the intel,pirq-routing property below. 676 677 intel,pirq-routing = < 678 PCI_BDF(0, 2, 0) INTA PIRQA 679 ... 680 >; 681 682As you see each entry has 3 cells. For the first one, we need describe all pci 683devices mounted on the board. For SoC devices, normally there is a chapter on 684the chipset datasheet which lists all the available PCI devices. For example on 685Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we 686can get the interrupt pin either from datasheet or hardware via U-Boot shell. 687The reliable source is the hardware as sometimes chipset datasheet is not 100% 688up-to-date. Type 'pci header' plus the device's pci bus/device/function number 689from U-Boot shell below. 690 691 => pci header 0.1e.1 692 vendor ID = 0x8086 693 device ID = 0x0f08 694 ... 695 interrupt line = 0x09 696 interrupt pin = 0x04 697 ... 698 699It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin 700register. Repeat this until you get interrupt pins for all the devices. The last 701cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel 702chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This 703can be changed by registers in LPC bridge. So far Intel FSP does not touch those 704registers so we can write down the PIRQ according to the default mapping rule. 705 706Once we get the PIRQ routing information in the device tree, the interrupt 707allocation and assignment will be done by U-Boot automatically. Now you can 708enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and 709CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC. 710 711TODO List 712--------- 713- Audio 714- Chrome OS verified boot 715- SMI and ACPI support, to provide platform info and facilities to Linux 716 717References 718---------- 719[1] http://www.coreboot.org 720[2] http://www.qemu.org 721[3] http://www.coreboot.org/~stepan/pci8086,0166.rom 722[4] http://www.intel.com/content/www/us/en/embedded/design-tools/evaluation-platforms/atom-e660-eg20t-development-kit.html 723[5] http://www.intel.com/fsp 724[6] http://www.intel.com/content/www/us/en/secure/intelligent-systems/privileged/e6xx-35-b1-cmc22211.html 725[7] http://www.ami.com/products/bios-uefi-tools-and-utilities/bios-uefi-utilities/ 726[8] http://en.wikipedia.org/wiki/Microcode 727[9] http://simplefirmware.org 728[10] http://www.intel.com/design/archives/processors/pro/docs/242016.htm 729[11] https://en.wikipedia.org/wiki/GUID_Partition_Table 730[12] http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf 731[13] http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf 732[14] doc/device-tree-bindings/misc/intel,irq-router.txt 733