Comment 85 for bug 814325

Created attachment 50311
Script to reproduce

Forwarding this for launchpad bug reporter Marc Deslauriers
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/814325

After f0575e92974d328e8816ed89704c985a7d7d90ac (drm/i915: DP_PIPE_ENABLED must check transcoder on CPT) was introduced in the kernel this person's Lenovo T510 machine started to come back from dpms fuzzy (see attached pictures) randomly, and another dpms cycle corrects it. This is still a problem on 3.1-rc2, and seems to be limited to this one machine with an optimus configuration (set to use only the integrated GPU) after testing on a wide variety of other machines including another T510 with an intel only config. He can reproduce the bug with the attached epilepsy.sh script which does rapid dpms off and on again easily.

System environment:
-- chipset: Intel Corporation Core Processor Integrated Graphics Controller [8086:0046]
-- system architecture: amd64
-- xf86-video-intel/xserver/mesa/libdrm version: both ubuntu 11.04 and current 11.10 were tested. 11.04: libdrm 2.4.23, xf86-video-intel 2.14, mesa 7.10.2, xserver 1.10.1, kernel 2.6.38-11.48
11.10: libdrm 2.4.26, xf86-video-intel 2.15.901, mesa 7.11, xserver 1.10.2.902, kernel 3.0.1
-- kernel version: 2.6.38-11 (which has the above commit backported), 3.1-rc2, various other kernels in between those two
-- Linux distribution: Ubuntu 11.04, Ubuntu 11.10
-- Machine or mobo model: Lenovo T510 (4313CTO)
-- Display connector: LVDS