The patches by Nicholas are now merged in drm-next-5.4 branch (tested with
recent commit that bases the branch on 5.3-rc3), but the mouse input issue in
certain games is still unaffected.

I was also able to reproduce it with a different system (also with RX 580)
which features a 60Hz FreeSync display, it definitely makes FreeSync impossible
to use in the aforementioned titles.