https://bugzilla.kernel.org/show_bug.cgi?id=83461
--- Comment #37 from Alex Deucher alexdeucher@gmail.com --- (In reply to Joerg Esser from comment #35)
I had similar problems until I used 3.18.7. I couldn´t even boot beyond radeon load. The whole kernel crashed and my Monitor showed no usable signal. I had to blacklist and load it manually with option radeon.dpm=0, after turning on my Monitor . With kernel 3.18.6 I could use the radeon option radeon.aspm=0, but still had to turn on my Monitor before radeon module load.
Now with this kernel I only need radeon.aspm=0 and no blacklist option, either the Monitor is turned on before or after radeon module load. Also GPU speedup with Video output works fine.
Please file a different bug. This bug and the patch only affect old asics like the RS880. Something else must have fixed the issue for you.