https://bugzilla.kernel.org/show_bug.cgi?id=119631
--- Comment #18 from Michel Dänzer michel@daenzer.net --- (In reply to John Brooks from comment #17)
Looks like it may actually have been a kernel regression. https://bugs.freedesktop.org/show_bug.cgi?id=97260#c12
We can't be sure about that until the problem is fully understood / fixed. So far it still seems more likely that the kernel change triggered an existing issue somewhere else.