Comment # 17 on bug 1222156 from Togan Muftuoglu

(In reply to Stefan Dirsch from comment #16)
> I'm still not sure whether it's a regression in Mesa (radeonsi DRI driver)
> or an issue in radeon kernel driver. I mean the issue doesn't occur for
> users being able to switch to amdgpu kernel driver and I'm pretty sure
> radeonsi DRI driver is still being used with that configuration.

You are correct with the assumption as I see in lsmod

drm_display_helper    245760  2 amdgpu,radeon

and I can see in Xorg log

] (II) AMDGPU(0): [DRI2] Setup complete
[    15.655] (II) AMDGPU(0): [DRI2]   DRI driver: radeonsi
[    15.655] (II) AMDGPU(0): [DRI2]   VDPAU driver: radeonsi

So am I really using amdgpu or radeon weird