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#
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# Copyright (C) 2014, Simon Glass <sjg@chromium.org>
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# Copyright (C) 2014, Bin Meng <bmeng.cn@gmail.com>
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#
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# SPDX-License-Identifier: GPL-2.0+
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#
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U-Boot on x86
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=============
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This document describes the information about U-Boot running on x86 targets,
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including supported boards, build instructions, todo list, etc.
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Status
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------
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U-Boot supports running as a coreboot [1] payload on x86. So far only Link
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(Chromebook Pixel) and QEMU [2] x86 targets have been tested, but it should
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work with minimal adjustments on other x86 boards since coreboot deals with
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most of the low-level details.
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U-Boot also supports booting directly from x86 reset vector, without coreboot.
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In this case, known as bare mode, from the fact that it runs on the
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'bare metal', U-Boot acts like a BIOS replacement. Currently Link, QEMU x86
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targets and all Intel boards support running U-Boot 'bare metal'.
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As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit
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Linux kernel as part of a FIT image. It also supports a compressed zImage.
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U-Boot supports loading an x86 VxWorks kernel. Please check README.vxworks
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for more details.
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Build Instructions for U-Boot as coreboot payload
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-------------------------------------------------
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Building U-Boot as a coreboot payload is just like building U-Boot for targets
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on other architectures, like below:
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$ make coreboot-x86_defconfig
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$ make all
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Note this default configuration will build a U-Boot payload for the QEMU board.
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To build a coreboot payload against another board, you can change the build
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configuration during the 'make menuconfig' process.
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x86 architecture --->
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...
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(qemu-x86) Board configuration file
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(qemu-x86_i440fx) Board Device Tree Source (dts) file
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(0x01920000) Board specific Cache-As-RAM (CAR) address
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(0x4000) Board specific Cache-As-RAM (CAR) size
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Change the 'Board configuration file' and 'Board Device Tree Source (dts) file'
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to point to a new board. You can also change the Cache-As-RAM (CAR) related
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settings here if the default values do not fit your new board.
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Build Instructions for U-Boot as BIOS replacement (bare mode)
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-------------------------------------------------------------
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Building a ROM version of U-Boot (hereafter referred to as u-boot.rom) is a
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little bit tricky, as generally it requires several binary blobs which are not
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shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build is
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not turned on by default in the U-Boot source tree. Firstly, you need turn it
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on by enabling the ROM build:
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$ export BUILD_ROM=y
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This tells the Makefile to build u-boot.rom as a target.
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---
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Chromebook Link specific instructions for bare mode:
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First, you need the following binary blobs:
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* descriptor.bin - Intel flash descriptor
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* me.bin - Intel Management Engine
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* mrc.bin - Memory Reference Code, which sets up SDRAM
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* video ROM - sets up the display
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You can get these binary blobs by:
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$ git clone http://review.coreboot.org/p/blobs.git
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$ cd blobs
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Find the following files:
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* ./mainboard/google/link/descriptor.bin
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* ./mainboard/google/link/me.bin
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* ./northbridge/intel/sandybridge/systemagent-r6.bin
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The 3rd one should be renamed to mrc.bin.
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As for the video ROM, you can get it here [3] and rename it to vga.bin.
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Make sure all these binary blobs are put in the board directory.
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Now you can build U-Boot and obtain u-boot.rom:
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$ make chromebook_link_defconfig
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$ make all
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---
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Intel Crown Bay specific instructions for bare mode:
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U-Boot support of Intel Crown Bay board [4] relies on a binary blob called
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Firmware Support Package [5] to perform all the necessary initialization steps
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as documented in the BIOS Writer Guide, including initialization of the CPU,
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memory controller, chipset and certain bus interfaces.
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Download the Intel FSP for Atom E6xx series and Platform Controller Hub EG20T,
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install it on your host and locate the FSP binary blob. Note this platform
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also requires a Chipset Micro Code (CMC) state machine binary to be present in
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the SPI flash where u-boot.rom resides, and this CMC binary blob can be found
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in this FSP package too.
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* ./FSP/QUEENSBAY_FSP_GOLD_001_20-DECEMBER-2013.fd
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* ./Microcode/C0_22211.BIN
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Rename the first one to fsp.bin and second one to cmc.bin and put them in the
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board directory.
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Note the FSP release version 001 has a bug which could cause random endless
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loop during the FspInit call. This bug was published by Intel although Intel
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did not describe any details. We need manually apply the patch to the FSP
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binary using any hex editor (eg: bvi). Go to the offset 0x1fcd8 of the FSP
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binary, change the following five bytes values from orginally E8 42 FF FF FF
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to B8 00 80 0B 00.
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As for the video ROM, you need manually extract it from the Intel provided
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BIOS for Crown Bay here [6], using the AMI MMTool [7]. Check PCI option ROM
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ID 8086:4108, extract and save it as vga.bin in the board directory.
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Now you can build U-Boot and obtain u-boot.rom
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$ make crownbay_defconfig
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$ make all
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---
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Intel Minnowboard Max instructions for bare mode:
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This uses as FSP as with Crown Bay, except it is for the Atom E3800 series.
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Download this and get the .fd file (BAYTRAIL_FSP_GOLD_003_16-SEP-2014.fd at
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the time of writing). Put it in the board directory:
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board/intel/minnowmax/fsp.bin
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Obtain the VGA RAM (Vga.dat at the time of writing) and put it into the same
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directory: board/intel/minnowmax/vga.bin
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You still need two more binary blobs. The first comes from the original
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firmware image available from:
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http://firmware.intel.com/sites/default/files/2014-WW42.4-MinnowBoardMax.73-64-bit.bin_Release.zip
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Unzip it:
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$ unzip 2014-WW42.4-MinnowBoardMax.73-64-bit.bin_Release.zip
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Use ifdtool in the U-Boot tools directory to extract the images from that
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file, for example:
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$ ./tools/ifdtool -x MNW2MAX1.X64.0073.R02.1409160934.bin
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This will provide the descriptor file - copy this into the correct place:
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$ cp flashregion_0_flashdescriptor.bin board/intel/minnowmax/descriptor.bin
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Then do the same with the sample SPI image provided in the FSP (SPI.bin at
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the time of writing) to obtain the last image. Note that this will also
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produce a flash descriptor file, but it does not seem to work, probably
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because it is not designed for the Minnowmax. That is why you need to get
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the flash descriptor from the original firmware as above.
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$ ./tools/ifdtool -x BayleyBay/SPI.bin
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$ cp flashregion_2_intel_me.bin board/intel/minnowmax/me.bin
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Now you can build U-Boot and obtain u-boot.rom
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$ make minnowmax_defconfig
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$ make all
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Checksums are as follows (but note that newer versions will invalidate this):
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$ md5sum -b board/intel/minnowmax/*.bin
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ffda9a3b94df5b74323afb328d51e6b4 board/intel/minnowmax/descriptor.bin
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69f65b9a580246291d20d08cbef9d7c5 board/intel/minnowmax/fsp.bin
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894a97d371544ec21de9c3e8e1716c4b board/intel/minnowmax/me.bin
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a2588537da387da592a27219d56e9962 board/intel/minnowmax/vga.bin
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The ROM image is broken up into these parts:
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Offset Description Controlling config
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------------------------------------------------------------
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000000 descriptor.bin Hard-coded to 0 in ifdtool
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001000 me.bin Set by the descriptor
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500000 <spare>
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6f0000 MRC cache CONFIG_ENABLE_MRC_CACHE
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700000 u-boot-dtb.bin CONFIG_SYS_TEXT_BASE
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790000 vga.bin CONFIG_VGA_BIOS_ADDR
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7c0000 fsp.bin CONFIG_FSP_ADDR
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7f8000 <spare> (depends on size of fsp.bin)
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7fe000 Environment CONFIG_ENV_OFFSET
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7ff800 U-Boot 16-bit boot CONFIG_SYS_X86_START16
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Overall ROM image size is controlled by CONFIG_ROM_SIZE.
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---
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Intel Galileo instructions for bare mode:
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Only one binary blob is needed for Remote Management Unit (RMU) within Intel
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Quark SoC. Not like FSP, U-Boot does not call into the binary. The binary is
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needed by the Quark SoC itself.
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You can get the binary blob from Quark Board Support Package from Intel website:
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* ./QuarkSocPkg/QuarkNorthCluster/Binary/QuarkMicrocode/RMU.bin
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Rename the file and put it to the board directory by:
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$ cp RMU.bin board/intel/galileo/rmu.bin
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Now you can build U-Boot and obtain u-boot.rom
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$ make galileo_defconfig
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$ make all
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QEMU x86 target instructions:
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To build u-boot.rom for QEMU x86 targets, just simply run
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$ make qemu-x86_defconfig
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$ make all
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Note this default configuration will build a U-Boot for the QEMU x86 i440FX
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board. To build a U-Boot against QEMU x86 Q35 board, you can change the build
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configuration during the 'make menuconfig' process like below:
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Device Tree Control --->
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...
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(qemu-x86_q35) Default Device Tree for DT control
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Test with coreboot
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------------------
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For testing U-Boot as the coreboot payload, there are things that need be paid
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attention to. coreboot supports loading an ELF executable and a 32-bit plain
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binary, as well as other supported payloads. With the default configuration,
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U-Boot is set up to use a separate Device Tree Blob (dtb). As of today, the
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generated u-boot-dtb.bin needs to be packaged by the cbfstool utility (a tool
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provided by coreboot) manually as coreboot's 'make menuconfig' does not provide
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this capability yet. The command is as follows:
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# in the coreboot root directory
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$ ./build/util/cbfstool/cbfstool build/coreboot.rom add-flat-binary \
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-f u-boot-dtb.bin -n fallback/payload -c lzma -l 0x1110000 -e 0x1110000
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Make sure 0x1110000 matches CONFIG_SYS_TEXT_BASE, which is the symbol address
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of _x86boot_start (in arch/x86/cpu/start.S).
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If you want to use ELF as the coreboot payload, change U-Boot configuration to
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use CONFIG_OF_EMBED instead of CONFIG_OF_SEPARATE.
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To enable video you must enable these options in coreboot:
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- Set framebuffer graphics resolution (1280x1024 32k-color (1:5:5))
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- Keep VESA framebuffer
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At present it seems that for Minnowboard Max, coreboot does not pass through
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the video information correctly (it always says the resolution is 0x0). This
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works correctly for link though.
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Test with QEMU for bare mode
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----------------------------
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QEMU is a fancy emulator that can enable us to test U-Boot without access to
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a real x86 board. Please make sure your QEMU version is 2.3.0 or above test
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U-Boot. To launch QEMU with u-boot.rom, call QEMU as follows:
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$ qemu-system-i386 -nographic -bios path/to/u-boot.rom
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This will instantiate an emulated x86 board with i440FX and PIIX chipset. QEMU
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also supports emulating an x86 board with Q35 and ICH9 based chipset, which is
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also supported by U-Boot. To instantiate such a machine, call QEMU with:
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$ qemu-system-i386 -nographic -bios path/to/u-boot.rom -M q35
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Note by default QEMU instantiated boards only have 128 MiB system memory. But
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it is enough to have U-Boot boot and function correctly. You can increase the
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system memory by pass '-m' parameter to QEMU if you want more memory:
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$ qemu-system-i386 -nographic -bios path/to/u-boot.rom -m 1024
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This creates a board with 1 GiB system memory. Currently U-Boot for QEMU only
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supports 3 GiB maximum system memory and reserves the last 1 GiB address space
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for PCI device memory-mapped I/O and other stuff, so the maximum value of '-m'
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would be 3072.
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QEMU emulates a graphic card which U-Boot supports. Removing '-nographic' will
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show QEMU's VGA console window. Note this will disable QEMU's serial output.
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If you want to check both consoles, use '-serial stdio'.
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Multicore is also supported by QEMU via '-smp n' where n is the number of cores
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to instantiate. Currently the default U-Boot built for QEMU supports 2 cores.
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In order to support more cores, you need add additional cpu nodes in the device
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tree and change CONFIG_MAX_CPUS accordingly.
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CPU Microcode
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-------------
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Modern CPUs usually require a special bit stream called microcode [8] to be
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loaded on the processor after power up in order to function properly. U-Boot
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has already integrated these as hex dumps in the source tree.
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SMP Support
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-----------
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On a multicore system, U-Boot is executed on the bootstrap processor (BSP).
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Additional application processors (AP) can be brought up by U-Boot. In order to
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have an SMP kernel to discover all of the available processors, U-Boot needs to
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prepare configuration tables which contain the multi-CPUs information before
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loading the OS kernel. Currently U-Boot supports generating two types of tables
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for SMP, called Simple Firmware Interface (SFI) [9] and Multi-Processor (MP)
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[10] tables. The writing of these two tables are controlled by two Kconfig
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options GENERATE_SFI_TABLE and GENERATE_MP_TABLE.
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Driver Model
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------------
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x86 has been converted to use driver model for serial and GPIO.
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Device Tree
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-----------
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x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to
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be turned on. Not every device on the board is configured via device tree, but
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more and more devices will be added as time goes by. Check out the directory
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arch/x86/dts/ for these device tree source files.
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Useful Commands
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---------------
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In keeping with the U-Boot philosophy of providing functions to check and
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adjust internal settings, there are several x86-specific commands that may be
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useful:
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fsp - Display information about Intel Firmware Support Package (FSP).
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This is only available on platforms which use FSP, mostly Atom.
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iod - Display I/O memory
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iow - Write I/O memory
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mtrr - List and set the Memory Type Range Registers (MTRR). These are used to
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tell the CPU whether memory is cacheable and if so the cache write
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mode to use. U-Boot sets up some reasonable values but you can
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adjust then with this command.
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Booting Ubuntu
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--------------
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As an example of how to set up your boot flow with U-Boot, here are
|
|
|
|
instructions for starting Ubuntu from U-Boot. These instructions have been
|
|
|
|
tested on Minnowboard MAX with a SATA driver but are equally applicable on
|
|
|
|
other platforms and other media. There are really only four steps and its a
|
|
|
|
very simple script, but a more detailed explanation is provided here for
|
|
|
|
completeness.
|
|
|
|
|
|
|
|
Note: It is possible to set up U-Boot to boot automatically using syslinux.
|
|
|
|
It could also use the grub.cfg file (/efi/ubuntu/grub.cfg) to obtain the
|
|
|
|
GUID. If you figure these out, please post patches to this README.
|
|
|
|
|
|
|
|
Firstly, you will need Ubunutu installed on an available disk. It should be
|
|
|
|
possible to make U-Boot start a USB start-up disk but for now let's assume
|
|
|
|
that you used another boot loader to install Ubuntu.
|
|
|
|
|
|
|
|
Use the U-Boot command line to find the UUID of the partition you want to
|
|
|
|
boot. For example our disk is SCSI device 0:
|
|
|
|
|
|
|
|
=> part list scsi 0
|
|
|
|
|
|
|
|
Partition Map for SCSI device 0 -- Partition Type: EFI
|
|
|
|
|
|
|
|
Part Start LBA End LBA Name
|
|
|
|
Attributes
|
|
|
|
Type GUID
|
|
|
|
Partition GUID
|
|
|
|
1 0x00000800 0x001007ff ""
|
|
|
|
attrs: 0x0000000000000000
|
|
|
|
type: c12a7328-f81f-11d2-ba4b-00a0c93ec93b
|
|
|
|
guid: 9d02e8e4-4d59-408f-a9b0-fd497bc9291c
|
|
|
|
2 0x00100800 0x037d8fff ""
|
|
|
|
attrs: 0x0000000000000000
|
|
|
|
type: 0fc63daf-8483-4772-8e79-3d69d8477de4
|
|
|
|
guid: 965c59ee-1822-4326-90d2-b02446050059
|
|
|
|
3 0x037d9000 0x03ba27ff ""
|
|
|
|
attrs: 0x0000000000000000
|
|
|
|
type: 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f
|
|
|
|
guid: 2c4282bd-1e82-4bcf-a5ff-51dedbf39f17
|
|
|
|
=>
|
|
|
|
|
|
|
|
This shows that your SCSI disk has three partitions. The really long hex
|
|
|
|
strings are called Globally Unique Identifiers (GUIDs). You can look up the
|
|
|
|
'type' ones here [11]. On this disk the first partition is for EFI and is in
|
|
|
|
VFAT format (DOS/Windows):
|
|
|
|
|
|
|
|
=> fatls scsi 0:1
|
|
|
|
efi/
|
|
|
|
|
|
|
|
0 file(s), 1 dir(s)
|
|
|
|
|
|
|
|
|
|
|
|
Partition 2 is 'Linux filesystem data' so that will be our root disk. It is
|
|
|
|
in ext2 format:
|
|
|
|
|
|
|
|
=> ext2ls scsi 0:2
|
|
|
|
<DIR> 4096 .
|
|
|
|
<DIR> 4096 ..
|
|
|
|
<DIR> 16384 lost+found
|
|
|
|
<DIR> 4096 boot
|
|
|
|
<DIR> 12288 etc
|
|
|
|
<DIR> 4096 media
|
|
|
|
<DIR> 4096 bin
|
|
|
|
<DIR> 4096 dev
|
|
|
|
<DIR> 4096 home
|
|
|
|
<DIR> 4096 lib
|
|
|
|
<DIR> 4096 lib64
|
|
|
|
<DIR> 4096 mnt
|
|
|
|
<DIR> 4096 opt
|
|
|
|
<DIR> 4096 proc
|
|
|
|
<DIR> 4096 root
|
|
|
|
<DIR> 4096 run
|
|
|
|
<DIR> 12288 sbin
|
|
|
|
<DIR> 4096 srv
|
|
|
|
<DIR> 4096 sys
|
|
|
|
<DIR> 4096 tmp
|
|
|
|
<DIR> 4096 usr
|
|
|
|
<DIR> 4096 var
|
|
|
|
<SYM> 33 initrd.img
|
|
|
|
<SYM> 30 vmlinuz
|
|
|
|
<DIR> 4096 cdrom
|
|
|
|
<SYM> 33 initrd.img.old
|
|
|
|
=>
|
|
|
|
|
|
|
|
and if you look in the /boot directory you will see the kernel:
|
|
|
|
|
|
|
|
=> ext2ls scsi 0:2 /boot
|
|
|
|
<DIR> 4096 .
|
|
|
|
<DIR> 4096 ..
|
|
|
|
<DIR> 4096 efi
|
|
|
|
<DIR> 4096 grub
|
|
|
|
3381262 System.map-3.13.0-32-generic
|
|
|
|
1162712 abi-3.13.0-32-generic
|
|
|
|
165611 config-3.13.0-32-generic
|
|
|
|
176500 memtest86+.bin
|
|
|
|
178176 memtest86+.elf
|
|
|
|
178680 memtest86+_multiboot.bin
|
|
|
|
5798112 vmlinuz-3.13.0-32-generic
|
|
|
|
165762 config-3.13.0-58-generic
|
|
|
|
1165129 abi-3.13.0-58-generic
|
|
|
|
5823136 vmlinuz-3.13.0-58-generic
|
|
|
|
19215259 initrd.img-3.13.0-58-generic
|
|
|
|
3391763 System.map-3.13.0-58-generic
|
|
|
|
5825048 vmlinuz-3.13.0-58-generic.efi.signed
|
|
|
|
28304443 initrd.img-3.13.0-32-generic
|
|
|
|
=>
|
|
|
|
|
|
|
|
The 'vmlinuz' files contain a packaged Linux kernel. The format is a kind of
|
|
|
|
self-extracting compressed file mixed with some 'setup' configuration data.
|
|
|
|
Despite its size (uncompressed it is >10MB) this only includes a basic set of
|
|
|
|
device drivers, enough to boot on most hardware types.
|
|
|
|
|
|
|
|
The 'initrd' files contain a RAM disk. This is something that can be loaded
|
|
|
|
into RAM and will appear to Linux like a disk. Ubuntu uses this to hold lots
|
|
|
|
of drivers for whatever hardware you might have. It is loaded before the
|
|
|
|
real root disk is accessed.
|
|
|
|
|
|
|
|
The numbers after the end of each file are the version. Here it is Linux
|
|
|
|
version 3.13. You can find the source code for this in the Linux tree with
|
|
|
|
the tag v3.13. The '.0' allows for additional Linux releases to fix problems,
|
|
|
|
but normally this is not needed. The '-58' is used by Ubuntu. Each time they
|
|
|
|
release a new kernel they increment this number. New Ubuntu versions might
|
|
|
|
include kernel patches to fix reported bugs. Stable kernels can exist for
|
|
|
|
some years so this number can get quite high.
|
|
|
|
|
|
|
|
The '.efi.signed' kernel is signed for EFI's secure boot. U-Boot has its own
|
|
|
|
secure boot mechanism - see [12] [13] and cannot read .efi files at present.
|
|
|
|
|
|
|
|
To boot Ubuntu from U-Boot the steps are as follows:
|
|
|
|
|
|
|
|
1. Set up the boot arguments. Use the GUID for the partition you want to
|
|
|
|
boot:
|
|
|
|
|
|
|
|
=> setenv bootargs root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro
|
|
|
|
|
|
|
|
Here root= tells Linux the location of its root disk. The disk is specified
|
|
|
|
by its GUID, using '/dev/disk/by-partuuid/', a Linux path to a 'directory'
|
|
|
|
containing all the GUIDs Linux has found. When it starts up, there will be a
|
|
|
|
file in that directory with this name in it. It is also possible to use a
|
|
|
|
device name here, see later.
|
|
|
|
|
|
|
|
2. Load the kernel. Since it is an ext2/4 filesystem we can do:
|
|
|
|
|
|
|
|
=> ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic
|
|
|
|
|
|
|
|
The address 30000000 is arbitrary, but there seem to be problems with using
|
|
|
|
small addresses (sometimes Linux cannot find the ramdisk). This is 48MB into
|
|
|
|
the start of RAM (which is at 0 on x86).
|
|
|
|
|
|
|
|
3. Load the ramdisk (to 64MB):
|
|
|
|
|
|
|
|
=> ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic
|
|
|
|
|
|
|
|
4. Start up the kernel. We need to know the size of the ramdisk, but can use
|
|
|
|
a variable for that. U-Boot sets 'filesize' to the size of the last file it
|
|
|
|
loaded.
|
|
|
|
|
|
|
|
=> zboot 03000000 0 04000000 ${filesize}
|
|
|
|
|
|
|
|
Type 'help zboot' if you want to see what the arguments are. U-Boot on x86 is
|
|
|
|
quite verbose when it boots a kernel. You should see these messages from
|
|
|
|
U-Boot:
|
|
|
|
|
|
|
|
Valid Boot Flag
|
|
|
|
Setup Size = 0x00004400
|
|
|
|
Magic signature found
|
|
|
|
Using boot protocol version 2.0c
|
|
|
|
Linux kernel version 3.13.0-58-generic (buildd@allspice) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015
|
|
|
|
Building boot_params at 0x00090000
|
|
|
|
Loading bzImage at address 100000 (5805728 bytes)
|
|
|
|
Magic signature found
|
|
|
|
Initial RAM disk at linear address 0x04000000, size 19215259 bytes
|
|
|
|
Kernel command line: "console=ttyS0,115200 root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro"
|
|
|
|
|
|
|
|
Starting kernel ...
|
|
|
|
|
|
|
|
U-Boot prints out some bootstage timing. This is more useful if you put the
|
|
|
|
above commands into a script since then it will be faster.
|
|
|
|
|
|
|
|
Timer summary in microseconds:
|
|
|
|
Mark Elapsed Stage
|
|
|
|
0 0 reset
|
|
|
|
241,535 241,535 board_init_r
|
|
|
|
2,421,611 2,180,076 id=64
|
|
|
|
2,421,790 179 id=65
|
|
|
|
2,428,215 6,425 main_loop
|
|
|
|
48,860,584 46,432,369 start_kernel
|
|
|
|
|
|
|
|
Accumulated time:
|
|
|
|
240,329 ahci
|
|
|
|
1,422,704 vesa display
|
|
|
|
|
|
|
|
Now the kernel actually starts:
|
|
|
|
|
|
|
|
[ 0.000000] Initializing cgroup subsys cpuset
|
|
|
|
[ 0.000000] Initializing cgroup subsys cpu
|
|
|
|
[ 0.000000] Initializing cgroup subsys cpuacct
|
|
|
|
[ 0.000000] Linux version 3.13.0-58-generic (buildd@allspice) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) ) #97-Ubuntu SMP Wed Jul 8 02:56:15 UTC 2015 (Ubuntu 3.13.0-58.97-generic 3.13.11-ckt22)
|
|
|
|
[ 0.000000] Command line: console=ttyS0,115200 root=/dev/disk/by-partuuid/965c59ee-1822-4326-90d2-b02446050059 ro
|
|
|
|
|
|
|
|
It continues for a long time. Along the way you will see it pick up your
|
|
|
|
ramdisk:
|
|
|
|
|
|
|
|
[ 0.000000] RAMDISK: [mem 0x04000000-0x05253fff]
|
|
|
|
...
|
|
|
|
[ 0.788540] Trying to unpack rootfs image as initramfs...
|
|
|
|
[ 1.540111] Freeing initrd memory: 18768K (ffff880004000000 - ffff880005254000)
|
|
|
|
...
|
|
|
|
|
|
|
|
Later it actually starts using it:
|
|
|
|
|
|
|
|
Begin: Running /scripts/local-premount ... done.
|
|
|
|
|
|
|
|
You should also see your boot disk turn up:
|
|
|
|
|
|
|
|
[ 4.357243] scsi 1:0:0:0: Direct-Access ATA ADATA SP310 5.2 PQ: 0 ANSI: 5
|
|
|
|
[ 4.366860] sd 1:0:0:0: [sda] 62533296 512-byte logical blocks: (32.0 GB/29.8 GiB)
|
|
|
|
[ 4.375677] sd 1:0:0:0: Attached scsi generic sg0 type 0
|
|
|
|
[ 4.381859] sd 1:0:0:0: [sda] Write Protect is off
|
|
|
|
[ 4.387452] sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
|
|
|
|
[ 4.399535] sda: sda1 sda2 sda3
|
|
|
|
|
|
|
|
Linux has found the three partitions (sda1-3). Mercifully it doesn't print out
|
|
|
|
the GUIDs. In step 1 above we could have used:
|
|
|
|
|
|
|
|
setenv bootargs root=/dev/sda2 ro
|
|
|
|
|
|
|
|
instead of the GUID. However if you add another drive to your board the
|
|
|
|
numbering may change whereas the GUIDs will not. So if your boot partition
|
|
|
|
becomes sdb2, it will still boot. For embedded systems where you just want to
|
|
|
|
boot the first disk, you have that option.
|
|
|
|
|
|
|
|
The last thing you will see on the console is mention of plymouth (which
|
|
|
|
displays the Ubuntu start-up screen) and a lot of 'Starting' messages:
|
|
|
|
|
|
|
|
* Starting Mount filesystems on boot [ OK ]
|
|
|
|
|
|
|
|
After a pause you should see a login screen on your display and you are done.
|
|
|
|
|
|
|
|
If you want to put this in a script you can use something like this:
|
|
|
|
|
|
|
|
setenv bootargs root=UUID=b2aaf743-0418-4d90-94cc-3e6108d7d968 ro
|
|
|
|
setenv boot zboot 03000000 0 04000000 \${filesize}
|
|
|
|
setenv bootcmd "ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; run boot"
|
|
|
|
saveenv
|
|
|
|
|
|
|
|
The \ is to tell the shell not to evaluate ${filesize} as part of the setenv
|
|
|
|
command.
|
|
|
|
|
|
|
|
You will also need to add this to your board configuration file, e.g.
|
|
|
|
include/configs/minnowmax.h:
|
|
|
|
|
|
|
|
#define CONFIG_BOOTDELAY 2
|
|
|
|
|
|
|
|
Now when you reset your board it wait a few seconds (in case you want to
|
|
|
|
interrupt) and then should boot straight into Ubuntu.
|
|
|
|
|
|
|
|
You can also bake this behaviour into your build by hard-coding the
|
|
|
|
environment variables if you add this to minnowmax.h:
|
|
|
|
|
|
|
|
#undef CONFIG_BOOTARGS
|
|
|
|
#undef CONFIG_BOOTCOMMAND
|
|
|
|
|
|
|
|
#define CONFIG_BOOTARGS \
|
|
|
|
"root=/dev/sda2 ro"
|
|
|
|
#define CONFIG_BOOTCOMMAND \
|
|
|
|
"ext2load scsi 0:2 03000000 /boot/vmlinuz-3.13.0-58-generic; " \
|
|
|
|
"ext2load scsi 0:2 04000000 /boot/initrd.img-3.13.0-58-generic; " \
|
|
|
|
"run boot"
|
|
|
|
|
|
|
|
#undef CONFIG_EXTRA_ENV_SETTINGS
|
|
|
|
#define CONFIG_EXTRA_ENV_SETTINGS "boot=zboot 03000000 0 04000000 ${filesize}"
|
|
|
|
|
|
|
|
|
|
|
|
Development Flow
|
|
|
|
----------------
|
|
|
|
These notes are for those who want to port U-Boot to a new x86 platform.
|
|
|
|
|
|
|
|
Since x86 CPUs boot from SPI flash, a SPI flash emulator is a good investment.
|
|
|
|
The Dediprog em100 can be used on Linux. The em100 tool is available here:
|
|
|
|
|
|
|
|
http://review.coreboot.org/p/em100.git
|
|
|
|
|
|
|
|
On Minnowboard Max the following command line can be used:
|
|
|
|
|
|
|
|
sudo em100 -s -p LOW -d u-boot.rom -c W25Q64DW -r
|
|
|
|
|
|
|
|
A suitable clip for connecting over the SPI flash chip is here:
|
|
|
|
|
|
|
|
http://www.dediprog.com/pd/programmer-accessories/EM-TC-8
|
|
|
|
|
|
|
|
This allows you to override the SPI flash contents for development purposes.
|
|
|
|
Typically you can write to the em100 in around 1200ms, considerably faster
|
|
|
|
than programming the real flash device each time. The only important
|
|
|
|
limitation of the em100 is that it only supports SPI bus speeds up to 20MHz.
|
|
|
|
This means that images must be set to boot with that speed. This is an
|
|
|
|
Intel-specific feature - e.g. tools/ifttool has an option to set the SPI
|
|
|
|
speed in the SPI descriptor region.
|
|
|
|
|
|
|
|
If your chip/board uses an Intel Firmware Support Package (FSP) it is fairly
|
|
|
|
easy to fit it in. You can follow the Minnowboard Max implementation, for
|
|
|
|
example. Hopefully you will just need to create new files similar to those
|
|
|
|
in arch/x86/cpu/baytrail which provide Bay Trail support.
|
|
|
|
|
|
|
|
If you are not using an FSP you have more freedom and more responsibility.
|
|
|
|
The ivybridge support works this way, although it still uses a ROM for
|
|
|
|
graphics and still has binary blobs containing Intel code. You should aim to
|
|
|
|
support all important peripherals on your platform including video and storage.
|
|
|
|
Use the device tree for configuration where possible.
|
|
|
|
|
|
|
|
For the microcode you can create a suitable device tree file using the
|
|
|
|
microcode tool:
|
|
|
|
|
|
|
|
./tools/microcode-tool -d microcode.dat -m <model> create
|
|
|
|
|
|
|
|
or if you only have header files and not the full Intel microcode.dat database:
|
|
|
|
|
|
|
|
./tools/microcode-tool -H BAY_TRAIL_FSP_KIT/Microcode/M0130673322.h \
|
|
|
|
-H BAY_TRAIL_FSP_KIT/Microcode/M0130679901.h \
|
|
|
|
-m all create
|
|
|
|
|
|
|
|
These are written to arch/x86/dts/microcode/ by default.
|
|
|
|
|
|
|
|
Note that it is possible to just add the micrcode for your CPU if you know its
|
|
|
|
model. U-Boot prints this information when it starts
|
|
|
|
|
|
|
|
CPU: x86_64, vendor Intel, device 30673h
|
|
|
|
|
|
|
|
so here we can use the M0130673322 file.
|
|
|
|
|
|
|
|
If you platform can display POST codes on two little 7-segment displays on
|
|
|
|
the board, then you can use post_code() calls from C or assembler to monitor
|
|
|
|
boot progress. This can be good for debugging.
|
|
|
|
|
|
|
|
If not, you can try to get serial working as early as possible. The early
|
|
|
|
debug serial port may be useful here. See setup_early_uart() for an example.
|
|
|
|
|
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During the U-Boot porting, one of the important steps is to write correct PIRQ
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routing information in the board device tree. Without it, device drivers in the
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Linux kernel won't function correctly due to interrupt is not working. Please
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refer to U-Boot doc [14] for the device tree bindings of Intel interrupt router.
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Here we have more details on the intel,pirq-routing property below.
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intel,pirq-routing = <
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PCI_BDF(0, 2, 0) INTA PIRQA
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...
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>;
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As you see each entry has 3 cells. For the first one, we need describe all pci
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devices mounted on the board. For SoC devices, normally there is a chapter on
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the chipset datasheet which lists all the available PCI devices. For example on
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Bay Trail, this is chapter 4.3 (PCI configuration space). For the second one, we
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can get the interrupt pin either from datasheet or hardware via U-Boot shell.
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The reliable source is the hardware as sometimes chipset datasheet is not 100%
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up-to-date. Type 'pci header' plus the device's pci bus/device/function number
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from U-Boot shell below.
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=> pci header 0.1e.1
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vendor ID = 0x8086
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device ID = 0x0f08
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...
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interrupt line = 0x09
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interrupt pin = 0x04
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...
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It shows this PCI device is using INTD pin as it reports 4 in the interrupt pin
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register. Repeat this until you get interrupt pins for all the devices. The last
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cell is the PIRQ line which a particular interrupt pin is mapped to. On Intel
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chipset, the power-up default mapping is INTA/B/C/D maps to PIRQA/B/C/D. This
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can be changed by registers in LPC bridge. So far Intel FSP does not touch those
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registers so we can write down the PIRQ according to the default mapping rule.
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Once we get the PIRQ routing information in the device tree, the interrupt
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allocation and assignment will be done by U-Boot automatically. Now you can
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enable CONFIG_GENERATE_PIRQ_TABLE for testing Linux kernel using i8259 PIC and
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CONFIG_GENERATE_MP_TABLE for testing Linux kernel using local APIC and I/O APIC.
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This script might be useful. If you feed it the output of 'pci long' from
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U-Boot then it will generate a device tree fragment with the interrupt
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configuration for each device (note it needs gawk 4.0.0):
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$ cat console_output |awk '/PCI/ {device=$4} /interrupt line/ {line=$4} \
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/interrupt pin/ {pin = $4; if (pin != "0x00" && pin != "0xff") \
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{patsplit(device, bdf, "[0-9a-f]+"); \
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printf "PCI_BDF(%d, %d, %d) INT%c PIRQ%c\n", strtonum("0x" bdf[1]), \
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strtonum("0x" bdf[2]), bdf[3], strtonum(pin) + 64, 64 + strtonum(pin)}}'
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Example output:
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PCI_BDF(0, 2, 0) INTA PIRQA
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PCI_BDF(0, 3, 0) INTA PIRQA
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...
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Porting Hints
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-------------
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Quark-specific considerations:
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To port U-Boot to other boards based on the Intel Quark SoC, a few things need
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to be taken care of. The first important part is the Memory Reference Code (MRC)
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parameters. Quark MRC supports memory-down configuration only. All these MRC
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parameters are supplied via the board device tree. To get started, first copy
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the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then
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change these values by consulting board manuals or your hardware vendor.
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Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h.
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The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports,
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but by default they are held in reset after power on. In U-Boot, PCIe
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initialization is properly handled as per Quark's firmware writer guide.
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In your board support codes, you need provide two routines to aid PCIe
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initialization, which are board_assert_perst() and board_deassert_perst().
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The two routines need implement a board-specific mechanism to assert/deassert
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PCIe PERST# pin. Care must be taken that in those routines that any APIs that
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may trigger PCI enumeration process are strictly forbidden, as any access to
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PCIe root port's configuration registers will cause system hang while it is
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held in reset. For more details, check how they are implemented by the Intel
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Galileo board support codes in board/intel/galileo/galileo.c.
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TODO List
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---------
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- Audio
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- Chrome OS verified boot
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- SMI and ACPI support, to provide platform info and facilities to Linux
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References
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----------
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[1] http://www.coreboot.org
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[2] http://www.qemu.org
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[3] http://www.coreboot.org/~stepan/pci8086,0166.rom
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[4] http://www.intel.com/content/www/us/en/embedded/design-tools/evaluation-platforms/atom-e660-eg20t-development-kit.html
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[5] http://www.intel.com/fsp
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[6] http://www.intel.com/content/www/us/en/secure/intelligent-systems/privileged/e6xx-35-b1-cmc22211.html
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[7] http://www.ami.com/products/bios-uefi-tools-and-utilities/bios-uefi-utilities/
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[8] http://en.wikipedia.org/wiki/Microcode
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[9] http://simplefirmware.org
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[10] http://www.intel.com/design/archives/processors/pro/docs/242016.htm
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[11] https://en.wikipedia.org/wiki/GUID_Partition_Table
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[12] http://events.linuxfoundation.org/sites/events/files/slides/chromeos_and_diy_vboot_0.pdf
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[13] http://events.linuxfoundation.org/sites/events/files/slides/elce-2014.pdf
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[14] doc/device-tree-bindings/misc/intel,irq-router.txt
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