https://bugs.freedesktop.org/show_bug.cgi?id=48772
--- Comment #1 from Alex Deucher agd5f@yahoo.com 2012-04-16 08:13:28 UTC --- Sounds like display bandwidth/watermark issues. Does booting with radeon.disp_priority=2 on the kernel command line in grub help? Also does disabling tiling help?