[coreboot] No external PCIe GPU possible/working on Gigabyte g41m-es2l

[Arthur Heymans]

Arthur Heymans <arthur at aheymans.xyz> writes:

> <i1w5d7gf38keg at tutanota.com> writes:
>
>> Hardware: Gigabyte g41m-es2l, latest coreboot git, latest seabios git, two nvidia gpu cards tested
>>
>> I tried to use some external GPU on a g41m-es2l to get some digial
>> screen output. It does not seem to work. When having build coreboot
>> with native vga-init for
>> the internal intel gpu, i never get a output from the nvidia
>> card. When i connect the analog VGA cable to the internal intel gpu
>> and boot up i can see many
>> nouveau (memory-space?) errors. Both GPUs (nvidia and intel) are then
>> enabled at once. Kernel 4.10 cant boot.
>
> Indeed the internal GPU should be disabled if an external GPU is
> detected. Afaik there is only one northbridge that currently does this
> for desktop boards which can have a wide variety of things in that slot
> and this is i945. (It disables integrated GPU in romstage)  Maybe this
> code can be reused?
>

Seems I was wrong. Adding a correct disable operation to the internal
graphic device should do it. The allocator will detect 2 graphic devices
and if internal one has a disable op, it will be disabled.

This might fix it:
https://review.coreboot.org/#/c/18504/

-- 
Arthur Heymans