https://bugs.freedesktop.org/show_bug.cgi?id=91880
--- Comment #75 from Ioannis Panagiotopoulos yiannispana@hotmail.com --- (In reply to Alex Deucher from comment #73)
(In reply to Julian from comment #72)
(In reply to Alex Deucher from comment #71)
Can you also test with the code and firmware from comment 32?
To clarify, do you mean only with the code from http://cgit.freedesktop.org/~agd5f/linux/commit/?h=new_smc or the whole kernel under agd5f?
Either use the kernel from that branch or cherry-pick the top 4 commits to whatever kernel you want to use and then install the new firmware files.
Also tried this since I have the same problem, compiled the new_smc branch, installed the kernel and the firmware, however the problem persists if I boot it without radeon.dpm=0.