https://bugs.freedesktop.org/show_bug.cgi?id=76286
--- Comment #14 from OmegaPhil+FreeDesktop.BugTracker@gmail.com --- I noticed v3.13.7-1 has come to Debian testing today with the following in the changelog:
- drm/radeon: fix runpm disabling on non-PX harder (may fix #741619, #742507)
I can confirm it doesnt help when I get rid of 'radeon.dpm=0' on boot.