Comment # 84 on bug 106175 from Michel Dänzer

(In reply to Nicholas Kazlauskas from comment #81)
> As for the difference between dc=1 and dc=0, that might just be a difference
> in behavior on the DRM level for atomic vs non-atomic drivers. Or a
> difference in userspace if they make a distinction there.

xf86-video-amdgpu doesn't, FWIW.