linux-kernel - Re: 2.6.32 regression (bisected): Video tearing/glitching with T400 laptops

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Date:	Wed, 14 Oct 2009 14:22:52 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	unlisted-recipients:; (no To-header on input)
Cc:	Theodore Tso <tytso@....edu>,
	"Carlos R. Mafra" <crmafra2@...il.com>,
	Eric Anholt <eric@...olt.net>, linux-kernel@...r.kernel.org,
	Keith Packard <keithp@...thp.com>,
	Chris Wilson <chris@...is-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@...tuousgeek.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@...ts.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

View attachment "i915-g4x-watermarks-hack.patch" of type "text/x-patch" (1645 bytes)

View attachment "i915-install-fence.patch" of type "text/x-patch" (3016 bytes)