[Intel-gfx] Fw: 2.6.32 regression (bisected): Video tearing/glitching with T400 laptops

[Jesse Barnes]

Begin forwarded message:

Date: Wed, 14 Oct 2009 14:22:52 -0700
From: Jesse Barnes <jbarnes at virtuousgeek.org>
Cc: Theodore Tso <tytso at mit.edu>, "Carlos R. Mafra"
<crmafra2 at gmail.com>, Eric Anholt <eric at anholt.net>,
linux-kernel at vger.kernel.org, Keith Packard <keithp at keithp.com>, Chris
Wilson <chris at chris-wilson.co.uk> Subject: Re: 2.6.32 regression
(bisected): Video tearing/glitching with T400 laptops


On Tue, 13 Oct 2009 12:14:26 -0700
Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> According to the chipset team that form of display corruption is
> likely related to RAM self-refresh... Sounds like the display plane
> isn't getting its memory requests serviced fast enough when in
> self-refresh mode, which might mean we have to program the
> self-refresh watermarks more aggressively on GM45.

Ok, like any good bug there was more than one thing wrong:
  - we weren't setting up a fence for the object before enabling FBC.
    Chris caught this and posted a patch to
    intel-gfx at lists.freedesktop.org titled "drm/i915: Install a fence
    register for fbc on g4x" (attached for convenience)
  - turns out we *do* need to set watermarks on G4x, despite some hw
    documentation indicating otherwise, patch for that attached

Hopefully with these two you'll have a solid display and some power
saving!

-- 
Jesse Barnes, Intel Open Source Technology Center
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