Hi Greg,
Please consider
9a0f938bde74 drm/i915: Use the correct size of the GTT for placing the per-process entries, 2012-08-24
for application to the 3.4.y tree.
Without this patch, Geoff Crompton's iMac hits a BUG during bootup. The problem is reproducible on
* Debian's 3.2.y-based kernel with drm backported from 3.4.37 * a Debian kernel close to 3.4.4 * a Debian kernel close to 3.5.5 * vanilla 3.4.4
He is not able to reproduce the problem on
* Debian's older 3.2.y-based kernels without the 3.4.y drm backport * a Debian kernel close to 3.6.4; various newer kernels * vanilla 3.4.4 + this patch
The patch was applied upstream during the 3.6-rc4 cycle, so newer kernels don't need it.
http://bugs.debian.org/703468 has details, including a screenshot of the boot failure ("unable to handling kernel paging request at ffffc9000b7ff000" in i915_gem_init_ppgtt).
Thoughts welcome, as always.
Regards, Jonathan