linux-kernel - Re: [PATCH] drm/i915: fix vblank wait test condition

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Message-ID: <20100825081336.GA30504@sucs.org>
Date:	Wed, 25 Aug 2010 09:13:36 +0100
From:	Sitsofe Wheeler <sitsofe@...oo.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org
Subject: Re: [PATCH] drm/i915: fix vblank wait test condition

On Tue, Aug 24, 2010 at 11:31:16AM -0700, Jesse Barnes wrote:
> When converting this to the new wait_for macro I inverted the wait
> condition, which causes all sorts of problems.  So correct it to fix
> several failures caused by the bad wait (flickering, bad output
> detection, tearing, etc.).

Further testing has shown this fixed one set of cases where strange
behaviour happened on my EeePC but there are other triggers. I've found
the following:

With this patch booting without a battery in the machine will lead to a
stable system without lots of errors appearing in dmesg (just one
"Insufficient FIFO" at boot). Doing "watch --differences=cumulative
xrandr" always shows the same outputs. VT switching occasionally causes
the occasional "*ERROR* vblank wait timed out" message. However doing a
suspend/resume brings back all the problems, dmesg starts filling up
with FIFO errors and xrandr starts reporting different outputs every
time it is called.  Additionally, booting with a battery inside the
machine at boot will always lead to the quirky behaviour too.

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