| # |
| # Copyright (C) 2014, Simon Glass <sjg@chromium.org> |
| # Copyright (C) 2014, Bin Meng <bmeng.cn@gmail.com> |
| # |
| # SPDX-License-Identifier: GPL-2.0+ |
| # |
| |
| U-Boot on x86 |
| ============= |
| |
| This document describes the information about U-Boot running on x86 targets, |
| including supported boards, build instructions, todo list, etc. |
| |
| Status |
| ------ |
| U-Boot supports running as a coreboot [1] payload on x86. So far only Link |
| (Chromebook Pixel) has been tested, but it should work with minimal adjustments |
| on other x86 boards since coreboot deals with most of the low-level details. |
| |
| U-Boot also supports booting directly from x86 reset vector without coreboot, |
| aka raw support or bare support. Currently Link and Intel Crown Bay board |
| support running U-Boot 'bare metal'. |
| |
| As for loading OS, U-Boot supports directly booting a 32-bit or 64-bit Linux |
| kernel as part of a FIT image. It also supports a compressed zImage. |
| |
| Build Instructions |
| ------------------ |
| Building U-Boot as a coreboot payload is just like building U-Boot for targets |
| on other architectures, like below: |
| |
| $ make coreboot-x86_defconfig |
| $ make all |
| |
| Building ROM version of U-Boot (hereafter referred to as u-boot.rom) is a |
| little bit tricky, as generally it requires several binary blobs which are not |
| shipped in the U-Boot source tree. Due to this reason, the u-boot.rom build is |
| not turned on by default in the U-Boot source tree. Firstly, you need turn it |
| on by uncommenting the following line in the main U-Boot Makefile: |
| |
| # ALL-$(CONFIG_X86_RESET_VECTOR) += u-boot.rom |
| |
| Link-specific instructions: |
| |
| First, you need the following binary blobs: |
| |
| * descriptor.bin - Intel flash descriptor |
| * me.bin - Intel Management Engine |
| * mrc.bin - Memory Reference Code, which sets up SDRAM |
| * video ROM - sets up the display |
| |
| You can get these binary blobs by: |
| |
| $ git clone http://review.coreboot.org/p/blobs.git |
| $ cd blobs |
| |
| Find the following files: |
| |
| * ./mainboard/google/link/descriptor.bin |
| * ./mainboard/google/link/me.bin |
| * ./northbridge/intel/sandybridge/systemagent-ivybridge.bin |
| |
| The 3rd one should be renamed to mrc.bin. |
| As for the video ROM, you can get it here [2]. |
| Make sure all these binary blobs are put in the board directory. |
| |
| Now you can build U-Boot and obtain u-boot.rom: |
| |
| $ make chromebook_link_defconfig |
| $ make all |
| |
| Intel Crown Bay specific instructions: |
| |
| U-Boot support of Intel Crown Bay board [3] relies on a binary blob called |
| Firmware Support Package [4] to perform all the necessary initialization steps |
| as documented in the BIOS Writer Guide, including initialization of the CPU, |
| memory controller, chipset and certain bus interfaces. |
| |
| Download the Intel FSP for Atom E6xx series and Platform Controller Hub EG20T, |
| install it on your host and locate the FSP binary blob. Note this platform |
| also requires a Chipset Micro Code (CMC) state machine binary to be present in |
| the SPI flash where u-boot.rom resides, and this CMC binary blob can be found |
| in this FSP package too. |
| |
| * ./FSP/QUEENSBAY_FSP_GOLD_001_20-DECEMBER-2013.fd |
| * ./Microcode/C0_22211.BIN |
| |
| Rename the first one to fsp.bin and second one to cmc.bin and put them in the |
| board directory. |
| |
| Now you can build U-Boot and obtaim u-boot.rom |
| |
| $ make crownbay_defconfig |
| $ make all |
| |
| CPU Microcode |
| ------------- |
| Modern CPU usually requires a special bit stream called microcode [5] to be |
| loaded on the processor after power up in order to function properly. U-Boot |
| has already integrated these as hex dumps in the source tree. |
| |
| Driver Model |
| ------------ |
| x86 has been converted to use driver model for serial and GPIO. |
| |
| Device Tree |
| ----------- |
| x86 uses device tree to configure the board thus requires CONFIG_OF_CONTROL to |
| be turned on. Not every device on the board is configured via devie tree, but |
| more and more devices will be added as time goes by. Check out the directory |
| arch/x86/dts/ for these device tree source files. |
| |
| TODO List |
| --------- |
| - MTRR support (for performance) |
| - Audio |
| - Chrome OS verified boot |
| - SMI and ACPI support, to provide platform info and facilities to Linux |
| |
| References |
| ---------- |
| [1] http://www.coreboot.org |
| [2] http://www.coreboot.org/~stepan/pci8086,0166.rom |
| [3] http://www.intel.com/content/www/us/en/embedded/design-tools/evaluation-platforms/atom-e660-eg20t-development-kit.html |
| [4] http://www.intel.com/fsp |
| [5] http://en.wikipedia.org/wiki/Microcode |