https://bugs.freedesktop.org/show_bug.cgi?id=60879
--- Comment #54 from Michel Dänzer michel@daenzer.net --- (In reply to comment #53)
What is the PCI ID of your GPU?
From attachment 74859:
[drm] initializing kernel modesetting (TAHITI 0x1002:0x679E 0x174B:0xE246).
So the PCI ID is 0x679E, a harvested Tahiti I think.