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

[Arthur Heymans]

<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?

>
> I tried removing the native vga-init. The only change is then that the
> Intel GPU works only when the kernel have load. Nvidia card deliver
> still same errors.
Whether the hardware is initialised or not makes no difference to the
fact that is enabled/disabled. Linux is sometimes unhappy if no form of
initialisation (option rom or native) has been performed.

>
> With OEM-bios the intel card gets disabled and a PCIe GPU works fine.
OEM bios does the right thing :)

-- 
Arthur Heymans