https://bugs.freedesktop.org/show_bug.cgi?id=102507
--- Comment #6 from dwagner jb5sgc1n.nya@20mm.eu --- The recent patches to amdgpu made those annoying kernel warning messages go away for me, too. Along with them went some initialization and self-test messages, such as e.g.
[drm] GPU post is not needed [drm] amdgpu: irq initialized. amdgpu: [powerplay] amdgpu: powerplay sw initialized
... which probably (hopefully) were not really relevant, either.