(In reply to John Frei from comment #44)
> I found out some interesting fact on my system:
> 
> If I start in textmode (runlevel 3) with no specific kernel parameter like
> 'radeon.dpm=0', set power_dm_force_perofrmance_level to 'high' and
> power_dpm_state to 'performance' and finally start the gdm service, the
> system works without crash. I was even able to play some games.
> 
> If I boot in textmode with radeon.dpm=0 and try to set power_profile to
> 'high', I get a crash immediately. I cannot even start gdm in this case.

Your experience sounds exactly like mine, setting a udev rule to do that upon
boot works fine as a workaround that persists accross reboots.