[coreboot] PciExpressGraphics on Intel Sandybridge

[Patrick Rudolph]

Hello,
I'm currently working on enabling PEG and run into some trouble.
With pending patches [1] applied, I was able to activate the Nvidia GPU.
The system hangs at Seabios/Grub2 with 2 GPUs enabled at the same time.
As I'm using the EHCI Debug Port I don't have any Seabios console
output.
Is there EHCI Debug Port support available ?
My first guess is some VGA IO ranges are overlapping.
Any ideas whats wrong ?

Do I need to provide two VBIOS blobs ? At the moment it is only possible
to provide one (using make menuconfig).
The ACPI code "parses" the IGD VBIOS, do I need to add similar code for
PEG ?

It looks like to best idea is to disable one GPU depending on a user
setting.
I would like to see a new define: PREFER_PEG_OVER_IGD
If set and PEG and IGD are found, IGD is disabled.
If unset and PEG and IGD are found, PEG is disabled.

Some UEFI allows to run both GPUs.
Running multiple GPUs at the same time seems to be possible, but
requires additional testing.

Regards,
Patrick

[1] http://review.coreboot.org/#/c/11058/
    http://review.coreboot.org/#/c/11059/