Comment 53 for bug 1157678

So what I thought might have been happening was that we reused an incorrectly sized cached framebuffer. Not so sure after reading i915_gem_framebuffer. However, I've implemented a defense against using the wrong framebuffer size:

commit 9dae6f9f1f169c228929185a8bd94e82afe92574
Author: Chris Wilson <email address hidden>
Date: Fri Apr 12 11:01:08 2013 +0100

    sna: Flush the scanout cache after resizing the display

    And ensure that any new scanout allocations make the requested size.

It will be worth updating xf86-video-intel.git and seeing if that makes any difference (will be in ppa:xorg-edgers in a few hours).