https://bugs.freedesktop.org/show_bug.cgi?id=93998
--- Comment #7 from SMF smf.linux@ntlworld.com --- (In reply to SMF from comment #6)
(In reply to Alex Deucher from comment #5)
Looks like you forced dpm on. Had you been using that previously?
Yes I have been using this setting for some time, I cannot remember how long (some years ?) or why I set it in the first place.
The other machine I have tested uses a Turks PRO [Radeon HD 6570/7570/8550] with the same boot settings and fails in the same way.