the branch includes three commits, fixing (at least) these bugs
https://bugs.launchpad.net/ubuntu/precise/+source/linux/+bug/982415 :
14667a4bde4361b drm/i915: Finish any pending operations on the framebuffer before disabling
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/999910
7ea29b13e5e3e1e drm/i915: Do the fallback non-IRQ wait in ring throttle, too.
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1015120 :
5d031e5b633d910 drm/i915: Remove use of the autoreported ringbuffer HEAD position