https://bugs.freedesktop.org/show_bug.cgi?id=79806
--- Comment #7 from Chernovsky Oleg adonai@xaker.ru ---
One more! If you (or anyone else) don't have the same card, but have some similar issue, you should check if the problem is the same or not (i.e. that the card does not turn up performance, when needed). Give some 3D load (e.g. glmark2), and check /sys/kernel/debug/dri/64/radeon_pm_info.
I'll try it in my spare time and post results here.