https://bugzilla.kernel.org/show_bug.cgi?id=75211
--- Comment #4 from Darren Salt bugspam@moreofthesa.me.uk --- It appears that you do actually need mismatched builds of xserver git and xf86-video-ati git, the latter built against (ideally) 1.15.99.902, to trigger this kernel bug... I wonder why it's gone apparently unnoticed until now. ☺