https://bugs.freedesktop.org/show_bug.cgi?id=64867
--- Comment #9 from Harald Judt h.judt@gmx.at ---
adding R600_DEBUG=nodma to my environment makes the problem go away... Not pretty, but a workaround. Same question though : how could I help debugging this?
I confirm this helps; Not against the GPU fault when playing the video, but against the crashes/hangs when an opengl xscreensaver etc. activates. Thanks for mentioning the workaround.
I've also applied https://bugs.freedesktop.org/attachment.cgi?id=72794, but it doesn't help.