[coreboot] Upstream coreboot on Broadwell/samus

[Huimin Zhang]

Hey all,

I was under the impression that coreboot support for the Broadwell
Chromebooks such as the new Chromebook Pixel was upstreamed but I am having
trouble getting it to work. On startup the lightbar and keyboard backlight
activate, but not the screen backlight. After about forty seconds, give or
take a second or two, it shuts off. I initially guessed that this was an ME
issue since I read that there is a killswitch if ME is missing but
apparently that killswitch acts more in the half hour range, and after my
second attempt I am sure it is not an ME issue. Regarding the lack of
screen backlight, I am inclined to think that it is not a VGA BIOS issue
but some error occurring before graphics are ever initialized.

I followed the instructions here:
https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/upstream-coreboot-on-intel-haswell-chromebook

I assume the process is not so different for Broadwell. Of course I
remembered to ad-lib the board name and quadruple check that the binaries I
extracted from the recovery image were not corrupted. On my first attempt a
few months ago I followed the instructions more or less exactly, but on
this second attempt I kept the VGA BIOS as 0406 instead of 0a06 and used
the new make options for including the descriptor and ME during the build
instead of adding it in after the build. I think at this point any chance
of an unintentional error can be ruled out. Perhaps I am missing some small
detail regarding the build settings specific to Broadwell?

Best,
Min
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