x86: Add a README.x86 for U-Boot on x86 support

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
(Use 'Link' as the name for the Chromebook Pixel consistently)

Change-Id: I158c88653978ff212334f6d4ffeaf49fa81baefe

doc/README.x86

@@ -0,0 +1,126 @@
+#
+# 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