[PATCH Oneiric SRU] LP:#1041315 -- drm/i915: apply timing generator bug workaround on CPT and PPT

[Timo Aaltonen]

SRU justification:

Impact:

Commit "628280f36e4fdbd drm/i915: Sanitize BIOS debugging bits from
PIPECONF" got in the oneiric kernel via upstream, since it fixed a
similar issue as here with an earlier version of the intel VBIOS. With a
newer VBIOS however, the issue is back. Simply reverting the commit
would likely mean breaking other setups.

this is a critical bug for some of our OEM's

Fix:

upstream patch 3bcf603f6d5d18b from 3.1 works around a bug in the
CPT/PPT PCH chips, and it was bisected as the commit that fixes the bug
in 3.1 and up.

Testcase:

boot a kernel that doesn't have 3bcf603f6d5d18b but has 628280f36e4fdbd
on hw that has a "new enough" VBIOS.

BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1041315

--

I'll send this to stable@ as well.