linux-kernel - Re: [REGRESSION, BISECTED, i915]: Periodic stalls with 2.6.36-rc2

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Date:	Tue, 24 Aug 2010 10:55:35 +0100
From:	Sitsofe Wheeler <sitsofe@...oo.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org
Subject: Re: [REGRESSION, BISECTED, i915]: Periodic stalls with 2.6.36-rc2

On Tue, Aug 24, 2010 at 10:00:47AM +0100, Chris Wilson wrote:
> 
> I was hoping that git would be more intelligent than that. Is there a
> way to simply bisect down one side of a merge?

Seemingly not...

> The slow boot is probably fixed by 4936a3b90d79dd8775c6ac23c2cf2dcebe29abde.
> A trivial patch you can apply on each step is:

Thanks that patch got it booting at normal speeds. Bisecting has now
narrowed the flickering/corruption with a newer X userspace down to
this:

commit 9d0498a2bf7455159b317f19531a3e5db2ecc9c4
Author: Jesse Barnes <jbarnes@...tuousgeek.org>
Date:   Wed Aug 18 13:20:54 2010 -0700

    drm/i915: wait for actual vblank, not just 20ms
    
    Waiting for a hard coded 20ms isn't always enough to make sure a vblank
    period has actually occurred, so add code to make sure we really have
    passed through a vblank period (or that the pipe is off when disabling).
    
    This prevents problems with mode setting and link training, and seems to
    fix a bug like https://bugs.freedesktop.org/show_bug.cgi?id=29278, but
    on an HP 8440p instead.  Hopefully also fixes
    https://bugs.freedesktop.org/show_bug.cgi?id=29141.
    
    Signed-off-by: Jesse Barnes <jbarnes@...tuousgeek.org>
    Signed-off-by: Eric Anholt <eric@...olt.net>

Reverting the above against HEAD seems to have fixed the misdetection of
displays and hangcheck warnings don't appear (although plenty of FIFO
warnings still). I notice that this commit also seemed to be the cause
of problems for Ivan and Pekka in http://lkml.org/lkml/2010/8/23/452 ...

-- 
Sitsofe | http://sucs.org/~sits/
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