https://bugs.freedesktop.org/show_bug.cgi?id=63935
--- Comment #14 from Alex Deucher agd5f@yahoo.com --- Try booting into runlevel 3 with radeon kms (radeon.modeset=0 on the kernel command line in grub, etc.), then manually load radeon with kms enabled (modprobe -r radeon; modprobe radeon modeset=1).