https://bugs.freedesktop.org/show_bug.cgi?id=66963
--- Comment #168 from Kajzer kap3tan@gmail.com --- I don't think it's the kernel (3.12 or 3.13) , when I managed to make it work I tried to boot under kernel 3.11 and it worked.
Anyhow, today it doesn't work anymore, no matter what I do. I didn't touch a thing, it was working fine for 2-3 days and now it's not.
boots fine with radeon.dpm=0