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. 22In this case, known as bare mode, from the fact that it runs on the 23'bare metal', U-Boot acts like a BIOS replacement. Currently Link, QEMU x86 24targets and all Intel boards support running U-Boot 'bare metal'. 25 26As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit 27Linux kernel as part of a FIT image. It also supports a compressed zImage. 28 29Build Instructions for U-Boot as coreboot payload 30------------------------------------------------- 31Building U-Boot as a coreboot payload is just like building U-Boot for targets 32on other architectures, like below: 33 34$ make coreboot-x86_defconfig 35$ make all 36 37Note this default configuration will build a U-Boot payload for the QEMU board. 38To build a coreboot payload against another board, you can change the build 39configuration during the 'make menuconfig' process. 40 41x86 architecture ---> 42 ... 43 (qemu-x86) Board configuration file 44 (qemu-x86_i440fx) Board Device Tree Source (dts) file 45 (0x01920000) Board specific Cache-As-RAM (CAR) address 46 (0x4000) Board specific Cache-As-RAM (CAR) size 47 48Change the 'Board configuration file' and 'Board Device Tree Source (dts) file' 49to point to a new board. You can also change the Cache-As-RAM (CAR) related 50settings here if the default values do not fit your new board. 51 52Build Instructions for U-Boot as BIOS replacement (bare mode) 53------------------------------------------------------------- 54Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a 55little bit tricky, as generally it requires several binary blobs which are not 56shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build is 57not turned on by default in the U-Boot source tree. Firstly, you need turn it 58on by enabling the ROM build: 59 60$ export BUILD_ROM=y 61 62This tells the Makefile to build u-boot.rom as a target. 63 64--- 65 66Chromebook Link specific instructions for bare mode: 67 68First, you need the following binary blobs: 69 70* descriptor.bin - Intel flash descriptor 71* me.bin - Intel Management Engine 72* mrc.bin - Memory Reference Code, which sets up SDRAM 73* video ROM - sets up the display 74 75You can get these binary blobs by: 76 77$ git clone http://review.coreboot.org/p/blobs.git 78$ cd blobs 79 80Find the following files: 81 82* ./mainboard/google/link/descriptor.bin 83* ./mainboard/google/link/me.bin 84* ./northbridge/intel/sandybridge/systemagent-r6.bin 85 86The 3rd one should be renamed to mrc.bin. 87As for the video ROM, you can get it here [3] and rename it to vga.bin. 88Make sure all these binary blobs are put in the board directory. 89 90Now you can build U-Boot and obtain u-boot.rom: 91 92$ make chromebook_link_defconfig 93$ make all 94 95--- 96 97Intel Crown Bay specific instructions for bare mode: 98 99U-Boot support of Intel Crown Bay board [4] relies on a binary blob called 100Firmware Support Package [5] to perform all the necessary initialization steps 101as documented in the BIOS Writer Guide, including initialization of the CPU, 102memory controller, chipset and certain bus interfaces. 103 104Download the Intel FSP for Atom E6xx series and Platform Controller Hub EG20T, 105install it on your host and locate the FSP binary blob. Note this platform 106also requires a Chipset Micro Code (CMC) state machine binary to be present in 107the SPI flash where u-boot.rom resides, and this CMC binary blob can be found 108in this FSP package too. 109 110* ./FSP/QUEENSBAY_FSP_GOLD_001_20-DECEMBER-2013.fd 111* ./Microcode/C0_22211.BIN 112 113Rename the first one to fsp.bin and second one to cmc.bin and put them in the 114board directory. 115 116Note the FSP release version 001 has a bug which could cause random endless 117loop during the FspInit call. This bug was published by Intel although Intel 118did not describe any details. We need manually apply the patch to the FSP 119binary using any hex editor (eg: bvi). Go to the offset 0x1fcd8 of the FSP 120binary, change the following five bytes values from orginally E8 42 FF FF FF 121to B8 00 80 0B 00. 122 123As for the video ROM, you need manually extract it from the Intel provided 124BIOS for Crown Bay here [6], using the AMI MMTool [7]. Check PCI option ROM 125ID 8086:4108, extract and save it as vga.bin in the board directory. 126 127Now you can build U-Boot and obtain u-boot.rom 128 129$ make crownbay_defconfig 130$ make all 131 132--- 133 134Intel Minnowboard Max instructions for bare mode: 135 136This uses as FSP as with Crown Bay, except it is for the Atom E3800 series. 137Download this and get the .fd file (BAYTRAIL_FSP_GOLD_003_16-SEP-2014.fd at 138the time of writing). Put it in the board directory: 139board/intel/minnowmax/fsp.bin 140 141Obtain the VGA RAM (Vga.dat at the time of writing) and put it into the same 142directory: board/intel/minnowmax/vga.bin 143 144You still need two more binary blobs. The first comes from the original 145firmware image available from: 146 147http://firmware.intel.com/sites/default/files/2014-WW42.4-MinnowBoardMax.73-64-bit.bin_Release.zip 148 149Unzip it: 150 151 $ unzip 2014-WW42.4-MinnowBoardMax.73-64-bit.bin_Release.zip 152 153Use ifdtool in the U-Boot tools directory to extract the images from that 154file, for example: 155 156 $ ./tools/ifdtool -x MNW2MAX1.X64.0073.R02.1409160934.bin 157 158This will provide the descriptor file - copy this into the correct place: 159 160 $ cp flashregion_0_flashdescriptor.bin board/intel/minnowmax/descriptor.bin 161 162Then do the same with the sample SPI image provided in the FSP (SPI.bin at 163the time of writing) to obtain the last image. Note that this will also 164produce a flash descriptor file, but it does not seem to work, probably 165because it is not designed for the Minnowmax. That is why you need to get 166the flash descriptor from the original firmware as above. 167 168 $ ./tools/ifdtool -x BayleyBay/SPI.bin 169 $ cp flashregion_2_intel_me.bin board/intel/minnowmax/me.bin 170 171Now you can build U-Boot and obtain u-boot.rom 172 173$ make minnowmax_defconfig 174$ make all 175 176Checksums are as follows (but note that newer versions will invalidate this): 177 178$ md5sum -b board/intel/minnowmax/*.bin 179ffda9a3b94df5b74323afb328d51e6b4 board/intel/minnowmax/descriptor.bin 18069f65b9a580246291d20d08cbef9d7c5 board/intel/minnowmax/fsp.bin 181894a97d371544ec21de9c3e8e1716c4b board/intel/minnowmax/me.bin 182a2588537da387da592a27219d56e9962 board/intel/minnowmax/vga.bin 183 184The ROM image is broken up into these parts: 185 186Offset Description Controlling config 187------------------------------------------------------------ 188000000 descriptor.bin Hard-coded to 0 in ifdtool 189001000 me.bin Set by the descriptor 190500000 <spare> 191700000 u-boot-dtb.bin CONFIG_SYS_TEXT_BASE 192790000 vga.bin CONFIG_VGA_BIOS_ADDR 1937c0000 fsp.bin CONFIG_FSP_ADDR 1947f8000 <spare> (depends on size of fsp.bin) 1957fe000 Environment CONFIG_ENV_OFFSET 1967ff800 U-Boot 16-bit boot CONFIG_SYS_X86_START16 197 198Overall ROM image size is controlled by CONFIG_ROM_SIZE. 199 200--- 201 202Intel Galileo instructions for bare mode: 203 204Only one binary blob is needed for Remote Management Unit (RMU) within Intel 205Quark SoC. Not like FSP, U-Boot does not call into the binary. The binary is 206needed by the Quark SoC itself. 207 208You can get the binary blob from Quark Board Support Package from Intel website: 209 210* ./QuarkSocPkg/QuarkNorthCluster/Binary/QuarkMicrocode/RMU.bin 211 212Rename the file and put it to the board directory by: 213 214 $ cp RMU.bin board/intel/galileo/rmu.bin 215 216Now you can build U-Boot and obtain u-boot.rom 217 218$ make galileo_defconfig 219$ make all 220 221QEMU x86 target instructions: 222 223To build u-boot.rom for QEMU x86 targets, just simply run 224 225$ make qemu-x86_defconfig 226$ make all 227 228Note this default configuration will build a U-Boot for the QEMU x86 i440FX 229board. To build a U-Boot against QEMU x86 Q35 board, you can change the build 230configuration during the 'make menuconfig' process like below: 231 232Device Tree Control ---> 233 ... 234 (qemu-x86_q35) Default Device Tree for DT control 235 236Test with coreboot 237------------------ 238For testing U-Boot as the coreboot payload, there are things that need be paid 239attention to. coreboot supports loading an ELF executable and a 32-bit plain 240binary, as well as other supported payloads. With the default configuration, 241U-Boot is set up to use a separate Device Tree Blob (dtb). As of today, the 242generated u-boot-dtb.bin needs to be packaged by the cbfstool utility (a tool 243provided by coreboot) manually as coreboot's 'make menuconfig' does not provide 244this capability yet. The command is as follows: 245 246# in the coreboot root directory 247$ ./build/util/cbfstool/cbfstool build/coreboot.rom add-flat-binary \ 248 -f u-boot-dtb.bin -n fallback/payload -c lzma -l 0x1110000 -e 0x1110000 249 250Make sure 0x1110000 matches CONFIG_SYS_TEXT_BASE, which is the symbol address 251of _x86boot_start (in arch/x86/cpu/start.S). 252 253If you want to use ELF as the coreboot payload, change U-Boot configuration to 254use CONFIG_OF_EMBED instead of CONFIG_OF_SEPARATE. 255 256To enable video you must enable these options in coreboot: 257 258 - Set framebuffer graphics resolution (1280x1024 32k-color (1:5:5)) 259 - Keep VESA framebuffer 260 261At present it seems that for Minnowboard Max, coreboot does not pass through 262the video information correctly (it always says the resolution is 0x0). This 263works correctly for link though. 264 265Test with QEMU for bare mode 266---------------------------- 267QEMU is a fancy emulator that can enable us to test U-Boot without access to 268a real x86 board. Please make sure your QEMU version is 2.3.0 or above test 269U-Boot. To launch QEMU with u-boot.rom, call QEMU as follows: 270 271$ qemu-system-i386 -nographic -bios path/to/u-boot.rom 272 273This will instantiate an emulated x86 board with i440FX and PIIX chipset. QEMU 274also supports emulating an x86 board with Q35 and ICH9 based chipset, which is 275also supported by U-Boot. To instantiate such a machine, call QEMU with: 276 277$ qemu-system-i386 -nographic -bios path/to/u-boot.rom -M q35 278 279Note by default QEMU instantiated boards only have 128 MiB system memory. But 280it is enough to have U-Boot boot and function correctly. You can increase the 281system memory by pass '-m' parameter to QEMU if you want more memory: 282 283$ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024 284 285This creates a board with 1 GiB system memory. Currently U-Boot for QEMU only 286supports 3 GiB maximum system memory and reserves the last 1 GiB address space 287for PCI device memory-mapped I/O and other stuff, so the maximum value of '-m' 288would be 3072. 289 290QEMU emulates a graphic card which U-Boot supports. Removing '-nographic' will 291show QEMU's VGA console window. Note this will disable QEMU's serial output. 292If you want to check both consoles, use '-serial stdio'. 293 294Multicore is also supported by QEMU via '-smp n' where n is the number of cores 295to instantiate. Currently the default U-Boot built for QEMU supports 2 cores. 296In order to support more cores, you need add additional cpu nodes in the device 297tree and change CONFIG_MAX_CPUS accordingly. 298 299CPU Microcode 300------------- 301Modern CPUs usually require a special bit stream called microcode [8] to be 302loaded on the processor after power up in order to function properly. U-Boot 303has already integrated these as hex dumps in the source tree. 304 305SMP Support 306----------- 307On a multicore system, U-Boot is executed on the bootstrap processor (BSP). 308Additional application processors (AP) can be brought up by U-Boot. In order to 309have an SMP kernel to discover all of the available processors, U-Boot needs to 310prepare configuration tables which contain the multi-CPUs information before 311loading the OS kernel. Currently U-Boot supports generating two types of tables 312for SMP, called Simple Firmware Interface (SFI) [9] and Multi-Processor (MP) 313[10] tables. The writing of these two tables are controlled by two Kconfig 314options GENERATE_SFI_TABLE and GENERATE_MP_TABLE. 315 316Driver Model 317------------ 318x86 has been converted to use driver model for serial and GPIO. 319 320Device Tree 321----------- 322x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to 323be turned on. Not every device on the board is configured via device tree, but 324more and more devices will be added as time goes by. Check out the directory 325arch/x86/dts/ for these device tree source files. 326 327Useful Commands 328--------------- 329In keeping with the U-Boot philosophy of providing functions to check and 330adjust internal settings, there are several x86-specific commands that may be 331useful: 332 333hob - Display information about Firmware Support Package (FSP) Hand-off 334 Block. This is only available on platforms which use FSP, mostly 335 Atom. 336iod - Display I/O memory 337iow - Write I/O memory 338mtrr - List and set the Memory Type Range Registers (MTRR). These are used to 339 tell the CPU whether memory is cacheable and if so the cache write 340 mode to use. U-Boot sets up some reasonable values but you can 341 adjust then with this command. 342 343Booting Ubuntu 344-------------- 345As an example of how to set up your boot flow with U-Boot, here are 346instructions for starting Ubuntu from U-Boot. These instructions have been 347tested on Minnowboard MAX with a SATA driver but are equally applicable on 348other platforms and other media. There are really only four steps and its a 349very simple script, but a more detailed explanation is provided here for 350completeness. 351 352Note: It is possible to set up U-Boot to boot automatically using syslinux. 353It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the 354GUID. If you figure these out, please post patches to this README. 355 356Firstly, you will need Ubunutu installed on an available disk. It should be 357possible to make U-Boot start a USB start-up disk but for now let's assume 358that you used another boot loader to install Ubuntu. 359 360Use the U-Boot command line to find the UUID of the partition you want to 361boot. For example our disk is SCSI device 0: 362 363=> part list scsi 0 364 365Partition Map for SCSI device 0 -- Partition Type: EFI 366 367 Part Start LBA End LBA Name 368 Attributes 369 Type GUID 370 Partition GUID 371 1 0x00000800 0x001007ff "" 372 attrs: 0x0000000000000000 373 type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b 374 guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c 375 2 0x00100800 0x037d8fff "" 376 attrs: 0x0000000000000000 377 type: 0fc63daf-8483-4772-8e79-3d69d8477de4 378 guid: 965c59ee-1822-4326-90d2-b02446050059 379 3 0x037d9000 0x03ba27ff "" 380 attrs: 0x0000000000000000 381 type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f 382 guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17 383 => 384 385This shows that your SCSI disk has three partitions. The really long hex 386strings are called Globally Unique Identifiers (GUIDs). You can look up the 387'type' ones here [11]. On this disk the first partition is for EFI and is in 388VFAT format (DOS/Windows): 389 390 => fatls scsi 0:1 391 efi/ 392 393 0 file(s), 1 dir(s) 394 395 396Partition 2 is 'Linux filesystem data' so that will be our root disk. It is 397in ext2 format: 398 399 => ext2ls scsi 0:2 400 <DIR> 4096 . 401 <DIR> 4096 .. 402 <DIR> 16384 lost+found 403 <DIR> 4096 boot 404 <DIR> 12288 etc 405 <DIR> 4096 media 406 <DIR> 4096 bin 407 <DIR> 4096 dev 408 <DIR> 4096 home 409 <DIR> 4096 lib 410 <DIR> 4096 lib64 411 <DIR> 4096 mnt 412 <DIR> 4096 opt 413 <DIR> 4096 proc 414 <DIR> 4096 root 415 <DIR> 4096 run 416 <DIR> 12288 sbin 417 <DIR> 4096 srv 418 <DIR> 4096 sys 419 <DIR> 4096 tmp 420 <DIR> 4096 usr 421 <DIR> 4096 var 422 <SYM> 33 initrd.img 423 <SYM> 30 vmlinuz 424 <DIR> 4096 cdrom 425 <SYM> 33 initrd.img.old 426 => 427 428and if you look in the /boot directory you will see the kernel: 429 430 => ext2ls scsi 0:2 /boot 431 <DIR> 4096 . 432 <DIR> 4096 .. 433 <DIR> 4096 efi 434 <DIR> 4096 grub 435 3381262 System.map-3.13.0-32-generic 436 1162712 abi-3.13.0-32-generic 437 165611 config-3.13.0-32-generic 438 176500 memtest86+.bin 439 178176 memtest86+.elf 440 178680 memtest86+_multiboot.bin 441 5798112 vmlinuz-3.13.0-32-generic 442 165762 config-3.13.0-58-generic 443 1165129 abi-3.13.0-58-generic 444 5823136 vmlinuz-3.13.0-58-generic 445 19215259 initrd.img-3.13.0-58-generic 446 3391763 System.map-3.13.0-58-generic 447 5825048 vmlinuz-3.13.0-58-generic.efi.signed 448 28304443 initrd.img-3.13.0-32-generic 449 => 450 451The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of 452self-extracting compressed file mixed with some 'setup' configuration data. 453Despite its size (uncompressed it is >10MB) this only includes a basic set of 454device drivers, enough to boot on most hardware types. 455 456The 'initrd' files contain a RAM disk. This is something that can be loaded 457into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots 458of drivers for whatever hardware you might have. It is loaded before the 459real root disk is accessed. 460 461The numbers after the end of each file are the version. Here it is Linux 462version 3.13. You can find the source code for this in the Linux tree with 463the tag v3.13. The '.0' allows for additional Linux releases to fix problems, 464but normally this is not needed. The '-58' is used by Ubuntu. Each time they 465release a new kernel they increment this number. New Ubuntu versions might 466include kernel patches to fix reported bugs. Stable kernels can exist for 467some years so this number can get quite high. 468 469The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own 470secure boot mechanism - see [12] [13] and cannot read .efi files at present. 471 472To boot Ubuntu from U-Boot the steps are as follows: 473 4741. Set up the boot arguments. Use the GUID for the partition you want to 475boot: 476 477 => setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro 478 479Here root= tells Linux the location of its root disk. The disk is specified 480by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory' 481containing all the GUIDs Linux has found. When it starts up, there will be a 482file in that directory with this name in it. It is also possible to use a 483device name here, see later. 484 4852. Load the kernel. Since it is an ext2/4 filesystem we can do: 486 487 => ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic 488 489The address 30000000 is arbitrary, but there seem to be problems with using 490small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into 491the start of RAM (which is at 0 on x86). 492 4933. Load the ramdisk (to 64MB): 494 495 => ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic 496 4974. Start up the kernel. We need to know the size of the ramdisk, but can use 498a variable for that. U-Boot sets 'filesize' to the size of the last file it 499loaded. 500 501 => zboot 03000000 0 04000000 ${filesize} 502 503Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is 504quite verbose when it boots a kernel. You should see these messages from 505U-Boot: 506 507 Valid Boot Flag 508 Setup Size = 0x00004400 509 Magic signature found 510 Using boot protocol version 2.0c 511 Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015 512 Building boot_params at 0x00090000 513 Loading bzImage at address 100000 (5805728 bytes) 514 Magic signature found 515 Initial RAM disk at linear address 0x04000000, size 19215259 bytes 516 Kernel command line: "console=ttyS0,115200 root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro" 517 518 Starting kernel ... 519 520U-Boot prints out some bootstage timing. This is more useful if you put the 521above commands into a script since then it will be faster. 522 523 Timer summary in microseconds: 524 Mark Elapsed Stage 525 0 0 reset 526 241,535 241,535 board_init_r 527 2,421,611 2,180,076 id=64 528 2,421,790 179 id=65 529 2,428,215 6,425 main_loop 530 48,860,584 46,432,369 start_kernel 531 532 Accumulated time: 533 240,329 ahci 534 1,422,704 vesa display 535 536Now the kernel actually starts: 537 538 [ 0.000000] Initializing cgroup subsys cpuset 539 [ 0.000000] Initializing cgroup subsys cpu 540 [ 0.000000] Initializing cgroup subsys cpuacct 541 [ 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) 542 [ 0.000000] Command line: console=ttyS0,115200 root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro 543 544It continues for a long time. Along the way you will see it pick up your 545ramdisk: 546 547 [ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff] 548... 549 [ 0.788540] Trying to unpack rootfs image as initramfs... 550 [ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000) 551... 552 553Later it actually starts using it: 554 555 Begin: Running /scripts/local-premount ... done. 556 557You should also see your boot disk turn up: 558 559 [ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5 560 [ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB) 561 [ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0 562 [ 4.381859] sd 1:0:0:0: [sda] Write Protect is off 563 [ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA 564 [ 4.399535] sda: sda1 sda2 sda3 565 566Linux has found the three partitions (sda1-3). Mercifully it doesn't print out 567the GUIDs. In step 1 above we could have used: 568 569 setenv bootargs root=/dev/sda2 ro 570 571instead of the GUID. However if you add another drive to your board the 572numbering may change whereas the GUIDs will not. So if your boot partition 573becomes sdb2, it will still boot. For embedded systems where you just want to 574boot the first disk, you have that option. 575 576The last thing you will see on the console is mention of plymouth (which 577displays the Ubuntu start-up screen) and a lot of 'Starting' messages: 578 579 * Starting Mount filesystems on boot [ OK ] 580 581After a pause you should see a login screen on your display and you are done. 582 583If you want to put this in a script you can use something like this: 584 585 setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro 586 setenv boot zboot 03000000 0 04000000 \${filesize} 587 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" 588 saveenv 589 590The \ is to tell the shell not to evaluate ${filesize} as part of the setenv 591command. 592 593You will also need to add this to your board configuration file, e.g. 594include/configs/minnowmax.h: 595 596 #define CONFIG_BOOTDELAY 2 597 598Now when you reset your board it wait a few seconds (in case you want to 599interrupt) and then should boot straight into Ubuntu. 600 601You can also bake this behaviour into your build by hard-coding the 602environment variables if you add this to minnowmax.h: 603 604#undef CONFIG_BOOTARGS 605#undef CONFIG_BOOTCOMMAND 606 607#define CONFIG_BOOTARGS \ 608 "root=/dev/sda2 ro" 609#define CONFIG_BOOTCOMMAND \ 610 "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \ 611 "ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \ 612 "run boot" 613 614#undef CONFIG_EXTRA_ENV_SETTINGS 615#define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}" 616 617 618Development Flow 619---------------- 620These notes are for those who want to port U-Boot to a new x86 platform. 621 622Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment. 623The Dediprog em100 can be used on Linux. The em100 tool is available here: 624 625 http://review.coreboot.org/p/em100.git 626 627On Minnowboard Max the following command line can be used: 628 629 sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r 630 631A suitable clip for connecting over the SPI flash chip is here: 632 633 http://www.dediprog.com/pd/programmer-accessories/EM-TC-8 634 635This allows you to override the SPI flash contents for development purposes. 636Typically you can write to the em100 in around 1200ms, considerably faster 637than programming the real flash device each time. The only important 638limitation of the em100 is that it only supports SPI bus speeds up to 20MHz. 639This means that images must be set to boot with that speed. This is an 640Intel-specific feature - e.g. tools/ifttool has an option to set the SPI 641speed in the SPI descriptor region. 642 643If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly 644easy to fit it in. You can follow the Minnowboard Max implementation, for 645example. Hopefully you will just need to create new files similar to those 646in arch/x86/cpu/baytrail which provide Bay Trail support. 647 648If you are not using an FSP you have more freedom and more responsibility. 649The ivybridge support works this way, although it still uses a ROM for 650graphics and still has binary blobs containing Intel code. You should aim to 651support all important peripherals on your platform including video and storage. 652Use the device tree for configuration where possible. 653 654For the microcode you can create a suitable device tree file using the 655microcode tool: 656 657 ./tools/microcode-tool -d microcode.dat -m <model> create 658 659or if you only have header files and not the full Intel microcode.dat database: 660 661 ./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \ 662 -H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h \ 663 -m all create 664 665These are written to arch/x86/dts/microcode/ by default. 666 667Note that it is possible to just add the micrcode for your CPU if you know its 668model. U-Boot prints this information when it starts 669 670 CPU: x86_64, vendor Intel, device 30673h 671 672so here we can use the M0130673322 file. 673 674If you platform can display POST codes on two little 7-segment displays on 675the board, then you can use post_code() calls from C or assembler to monitor 676boot progress. This can be good for debugging. 677 678If not, you can try to get serial working as early as possible. The early 679debug serial port may be useful here. See setup_early_uart() for an example. 680 681During the U-Boot porting, one of the important steps is to write correct PIRQ 682routing information in the board device tree. Without it, device drivers in the 683Linux kernel won't function correctly due to interrupt is not working. Please 684refer to U-Boot doc [14] for the device tree bindings of Intel interrupt router. 685Here we have more details on the intel,pirq-routing property below. 686 687 intel,pirq-routing = < 688 PCI_BDF(0, 2, 0) INTA PIRQA 689 ... 690 >; 691 692As you see each entry has 3 cells. For the first one, we need describe all pci 693devices mounted on the board. For SoC devices, normally there is a chapter on 694the chipset datasheet which lists all the available PCI devices. For example on 695Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we 696can get the interrupt pin either from datasheet or hardware via U-Boot shell. 697The reliable source is the hardware as sometimes chipset datasheet is not 100% 698up-to-date. Type 'pci header' plus the device's pci bus/device/function number 699from U-Boot shell below. 700 701 => pci header 0.1e.1 702 vendor ID = 0x8086 703 device ID = 0x0f08 704 ... 705 interrupt line = 0x09 706 interrupt pin = 0x04 707 ... 708 709It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin 710register. Repeat this until you get interrupt pins for all the devices. The last 711cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel 712chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This 713can be changed by registers in LPC bridge. So far Intel FSP does not touch those 714registers so we can write down the PIRQ according to the default mapping rule. 715 716Once we get the PIRQ routing information in the device tree, the interrupt 717allocation and assignment will be done by U-Boot automatically. Now you can 718enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and 719CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC. 720 721This script might be useful. If you feed it the output of 'pci long' from 722U-Boot then it will generate a device tree fragment with the interrupt 723configuration for each device (note it needs gawk 4.0.0): 724 725 $ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \ 726 /interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \ 727 {patsplit(device, bdf, "[0-9a-f]+"); \ 728 printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \ 729 strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}' 730 731Example output: 732 PCI_BDF(0, 2, 0) INTA PIRQA 733 PCI_BDF(0, 3, 0) INTA PIRQA 734... 735 736TODO List 737--------- 738- Audio 739- Chrome OS verified boot 740- SMI and ACPI support, to provide platform info and facilities to Linux 741 742References 743---------- 744[1] http://www.coreboot.org 745[2] http://www.qemu.org 746[3] http://www.coreboot.org/~stepan/pci8086,0166.rom 747[4] http://www.intel.com/content/www/us/en/embedded/design-tools/evaluation-platforms/atom-e660-eg20t-development-kit.html 748[5] http://www.intel.com/fsp 749[6] http://www.intel.com/content/www/us/en/secure/intelligent-systems/privileged/e6xx-35-b1-cmc22211.html 750[7] http://www.ami.com/products/bios-uefi-tools-and-utilities/bios-uefi-utilities/ 751[8] http://en.wikipedia.org/wiki/Microcode 752[9] http://simplefirmware.org 753[10] http://www.intel.com/design/archives/processors/pro/docs/242016.htm 754[11] https://en.wikipedia.org/wiki/GUID_Partition_Table 755[12] http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf 756[13] http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf 757[14] doc/device-tree-bindings/misc/intel,irq-router.txt 758