Update README.x86 to include new build instructions for U-Boot as the coreboot payload and testing considerations with coreboot.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
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Changes in v2: - New patch to update REAME.x86 for coreboot support
doc/README.x86 | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+)
diff --git a/doc/README.x86 b/doc/README.x86 index 5fab044..da0c712 100644 --- a/doc/README.x86 +++ b/doc/README.x86 @@ -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 aginst 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 @@ -93,6 +108,26 @@ Now you can build U-Boot and obtaim 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.in 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