https://bugs.freedesktop.org/show_bug.cgi?id=83792
--- Comment #7 from Tim Nelson wayland@wayland.id.au --- Anyway, it looks like I was wrong about the kernel modesetting; I think this is a side-effect of the more modern radeon driver not supporting nomodeset. So it's just a bug in the radeon driver, pure and simple. So now I suspect I have to do a kernel bisect. If you have any other advice, though, let me know.