Commit 617b867f authored by Bin Meng's avatar Bin Meng Committed by Simon Glass
Browse files

x86: Update README.x86 for coreboot support



Update README.x86 to include new build instructions for U-Boot as
the coreboot payload and testing considerations with coreboot.
Signed-off-by: default avatarBin Meng <bmeng.cn@gmail.com>
Acked-by: default avatarSimon Glass <sjg@chromium.org>
parent cdcc17d7
......@@ -32,6 +32,21 @@ on other architectures, like below:
$ make coreboot-x86_defconfig
$ make all
Note this default configuration will build a U-Boot payload for the Link board.
To build a coreboot payload against another board, you can change the build
configuration during the 'make menuconfig' process.
x86 architecture --->
...
(chromebook_link) Board configuration file
(chromebook_link) Board Device Tree Source (dts) file
(0x19200000) Board specific Cache-As-RAM (CAR) address
(0x4000) Board specific Cache-As-RAM (CAR) size
Change the 'Board configuration file' and 'Board Device Tree Source (dts) file'
to point to a new board. You can also change the Cache-As-RAM (CAR) related
settings here if the default values do not fit your new board.
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
......@@ -88,11 +103,31 @@ in this FSP package too.
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
Now you can build U-Boot and obtain u-boot.rom
$ make crownbay_defconfig
$ make all
Test with coreboot
------------------
For testing U-Boot as the coreboot payload, there are things that need be paid
attention to. coreboot supports loading an ELF executable and a 32-bit plain
binary, as well as other supported payloads. With the default configuration,
U-Boot is set up to use a separate Device Tree Blob (dtb). As of today, the
generated u-boot-dtb.bin needs to be packaged by the cbfstool utility (a tool
provided by coreboot) manually as coreboot's 'make menuconfig' does not provide
this capability yet. The command is as follows:
# in the coreboot root directory
$ ./build/util/cbfstool/cbfstool build/coreboot.rom add-flat-binary \
-f u-boot-dtb.bin -n fallback/payload -c lzma -l 0x1110000 -e 0x1110015
Make sure 0x1110000 matches CONFIG_SYS_TEXT_BASE and 0x1110015 matches the
symbol address of _start (in arch/x86/cpu/start.S).
If you want to use ELF as the coreboot payload, change U-Boot configuration to
use CONFIG_OF_EMBED.
CPU Microcode
-------------
Modern CPU usually requires a special bit stream called microcode [5] to be
......@@ -106,7 +141,7 @@ 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
be turned on. Not every device on the board is configured via device 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.
......
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