https://bugzilla.kernel.org/show_bug.cgi?id=94061
--- Comment #6 from Klaus Maier abcdmail@freenet.de --- radeon.bapm=1 brings back the originally reported behaviour (based on 3.14).
I didn't enable rdev->cg_flags and rdev->pg_flags as it is already known to be broken because it needs a complete kernel recompile.
The relevant code already was in 3.12, which was released 2013-11-03.
When will there be a fix? It is working w/ Catalyst. Why not w/ radeon? Both drivers are made by AMD finally ... .