Patrick Rudolph has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/41190 )
Change subject: device/: Add basic dualgraphics support ......................................................................
Patch Set 3:
(3 comments)
Thanks for working on this. Please state what you try to achieve. I made an attempt a while ago here: CB:12897 It's not that easy to fix.
In general you want only one GPU to decode I/O, which is likely required for graphics init on legacy devices. Besides that all GPUs could decode memory as long as they only the primary decodes the A-seg. Running graphics init on every GPU is possible by switching the "primary" between those runs, but that's not supported by coreboot (yet).
https://review.coreboot.org/c/coreboot/+/41190/3/src/device/device.c File src/device/device.c:
https://review.coreboot.org/c/coreboot/+/41190/3/src/device/device.c@769 PS3, Line 769: PCI_COMMAND_IO only the primary gpu should decode IO
https://review.coreboot.org/c/coreboot/+/41190/3/src/device/device.c@782 PS3, Line 782: (vga != vga_onboard) && vga_onboard && tab
https://review.coreboot.org/c/coreboot/+/41190/3/src/device/device.c@791 PS3, Line 791: if (!CONFIG(ENABLE_ALL_GPUS)) { That's just wrong.