https://bugzilla.kernel.org/show_bug.cgi?id=108221
--- Comment #14 from Fred Santos frederic.santos@u-bordeaux.fr --- (In reply to Michel Dänzer from comment #10)
(In reply to Fred Santos from comment #9)
(Is there a way to 'force' the use of amdgpu?)
Yes, you can force it in Section "Device" in /etc/X11/xorg.conf . If there is no such file yet, creating it with only something like this should work:
Section "Device" Identifier "Device0" Driver "amdgpu" EndSection
I compiled and booted some old kernels, and here are my observations:
1. Even when booting with old kernels that should have worked fine (e.g., 4.2), the problem persists...
2. 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.
Maybe an Xorg autodetection problem that doesn't come from the kernel itself? (Is it possible?)