https://bugzilla.kernel.org/show_bug.cgi?id=65761
--- Comment #11 from Christoph Haag haagch.christoph@googlemail.com --- Created attachment 119551 --> https://bugzilla.kernel.org/attachment.cgi?id=119551&action=edit dmesg with acpiphp.disable=1
A quick search also showed this: https://bugzilla.kernel.org/show_bug.cgi?id=67461
Good news: With acpiphp.disable=1 there are no errors with booting and using X. In a tty the gpu is in DynOff state.
Not so good news: When starting X it switches to DynPwr and after several minutes I don't think it ever powered down again. But when killing X it goes back to DynOff.
Still bad news: rmmod radeon.