https://bugs.freedesktop.org/show_bug.cgi?id=26891
--- Comment #48 from Alex Deucher agd5f@yahoo.com --- (In reply to comment #46)
Radeon now works for me on a MBP 8,2 booted from efistub in Linux 3.8.x. Can anyone else confirm this? You just need to make sure you add the PCI IDs to the xorg for both cards. Should Xorg detect them automatically? Is this another bug?
What do you mean by "make sure you add the PCI IDs to the xorg for both cards"? The driver should autodetect the cards fine. However for systems with multiple VGA cards, you may have to manually specify which ones you want to start X on.