https://bugzilla.kernel.org/show_bug.cgi?id=108221
--- Comment #15 from Michel Dänzer michel@daenzer.net --- (In reply to Fred Santos from comment #14)
- We found (Comment #10) that amdgpu was not found/activated during boot:
when 'forcing' its use by creating this /etc/X11/xorg.conf file, everything is OK, with all kernels I have tested (4.4, 4.3, 4.2). To put it in a nutshell, no matter the kernel we use, we have the same behavior: it works if and only if we add this /etc/X11/xorg.conf file.
If /etc/X11/xorg.conf.d/10-amdgpu.conf / /usr/share/X11/xorg.conf.d/10-amdgpu.conf isn't enough, then it sounds like maybe the amdgpu kernel driver isn't loaded yet the first time Xorg starts up during boot.
Also, it sounds like there's a bug in the Xorg modesetting driver causing the artifacts you described.
Probably no kernel bug here though.