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.. SPDX-License-Identifier: GPL-2.0+
.. sectionauthor:: Simon Glass <sjg@chromium.org>
Chromebook Samus
================
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
* refcode.elf - Additional Reference code
* vga.bin - video ROM, which sets up the display
If you have a samus you can obtain them from your flash, for example, in
developer mode on the Chromebook (use Ctrl-Alt-F2 to obtain a terminal and
log in as 'root')::
cd /tmp
flashrom -w samus.bin
scp samus.bin username@ip_address:/path/to/somewhere
If not see the coreboot tree where you can use::
bash crosfirmware.sh samus
to get the image. There is also an 'extract_blobs.sh' scripts that you can use
on the 'coreboot-Google_Samus.*' file to short-circuit some of the below.
Then 'ifdtool -x samus.bin' on your development machine will produce::
flashregion_0_flashdescriptor.bin
flashregion_1_bios.bin
flashregion_2_intel_me.bin
Rename flashregion_0_flashdescriptor.bin to descriptor.bin
Rename flashregion_2_intel_me.bin to me.bin
You can ignore flashregion_1_bios.bin - it is not used.
To get the rest, use 'cbfstool samus.bin print'::
samus.bin: 8192 kB, bootblocksize 2864, romsize 8388608, offset 0x700000
alignment: 64 bytes, architecture: x86
============================ ======== =========== ======
Name Offset Type Size
============================ ======== =========== ======
cmos_layout.bin 0x700000 cmos_layout 1164
pci8086,0406.rom 0x7004c0 optionrom 65536
spd.bin 0x710500 (unknown) 4096
cpu_microcode_blob.bin 0x711540 microcode 70720
fallback/romstage 0x722a00 stage 54210
fallback/ramstage 0x72fe00 stage 96382
config 0x7476c0 raw 6075
fallback/vboot 0x748ec0 stage 15980
fallback/refcode 0x74cd80 stage 75578
fallback/payload 0x75f500 payload 62878
u-boot.dtb 0x76eb00 (unknown) 5318
(empty) 0x770000 null 196504
mrc.bin 0x79ffc0 (unknown) 222876
(empty) 0x7d66c0 null 167320
============================ ======== =========== ======
You can extract what you need::
cbfstool samus.bin extract -n pci8086,0406.rom -f vga.bin
cbfstool samus.bin extract -n fallback/refcode -f refcode.rmod
cbfstool samus.bin extract -n mrc.bin -f mrc.bin
cbfstool samus.bin extract -n fallback/refcode -f refcode.bin -U
Note that the -U flag is only supported by the latest cbfstool. It unpacks
and decompresses the stage to produce a coreboot rmodule. This is a simple
representation of an ELF file. You need the patch "Support decoding a stage
with compression".
Put all 5 files into board/google/chromebook_samus.
Now you can build U-Boot and obtain u-boot.rom::
$ make chromebook_samus_defconfig
$ make all
If you are using em100, then this command will flash write -Boot::
em100 -s -d filename.rom -c W25Q64CV -r
Flash map for samus / broadwell:
:fffff800: SYS_X86_START16
:ffff0000: RESET_SEG_START
:fffd8000: TPL_TEXT_BASE
:fffa0000: X86_MRC_ADDR
:fff90000: VGA_BIOS_ADDR
:ffed0000: SYS_TEXT_BASE
:ffea0000: X86_REFCODE_ADDR
:ffe70000: SPL_TEXT_BASE
:ffbf8000: CONFIG_ENV_OFFSET (environemnt offset)
:ffbe0000: rw-mrc-cache (Memory-reference-code cache)
:ffa00000: <spare>
:ff801000: intel-me (address set by descriptor.bin)
:ff800000: intel-descriptor
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