https://bugs.freedesktop.org/show_bug.cgi?id=106363
--- Comment #4 from Gregor Münch gr.muench@gmail.com --- (In reply to Alex Deucher from comment #3)
dpm is enabled by default on SI parts so setting dpm=1 doesn't change anything.
This depends if you use amdgpu instead of radeon on SI. In that case amdgpu.dpm seems to be disabled. I tried to enable DPMS and read through a bunch of tutorials configuring Xorg but nothing did work. Then I stumbled about a newsentry on phoronix mentioned this patch: https://lists.freedesktop.org/archives/amd-gfx/2018-May/022771.html There you change the behavior for CIK parts to use PP by default. The logic of this patch changes amdgpu.dpm=-1 (auto) to switch from whatever to Powerplay.
I started my Kernel with amdgpu.dpm=1 and everything suddenly worked like magic.
Since I dont what Powerplay actually does in the Linux world and a quick google search came up with nothing and modinfo amdgpu just reveils dpm:DPM support (1 = enable, 0 = disable, -1 = auto) (int) but nothing about Powerplay I was really under the impression that DPM also enables Powerplay. Im sorry for the confusion.