https://bugs.freedesktop.org/show_bug.cgi?id=58661
--- Comment #3 from Thomas Rohloff v10lator@myway.de --- I'm not sure if it's mesa or kernel. Yes, it was working before last update (updated mesa + kernel).
I might be able to bisect later but atm my time is limited and as I don't even know what to bisect (kernel or mesa) it may take some time.