The original issue in this report, "Failed to map FB", seems to be the one reported upstream in http://bugs.freedesktop.org/show_bug.cgi?id=21233 and is now fixed in http://cgit.freedesktop.org/xorg/driver/xf86-video-radeonhd/commit/?id=881334543d2711f159c8fcaf4a30b8b0db3186d7