Comment # 5 on bug 103317 from Torsten Kessler

Created attachment 134943 [details]
Second Xorg log with EnablePageFlip turned off

You're right. I was mixing things up. I meant loading the radeon module and
blacklisting the amdgpu module solves the issue.
I'm just downloading the kernel from the amd-staging-drm-next branch. I will
see tomorow if it helps. Thank you for your help so far!