From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= <ville.syrjala@linux.intel.com>
Subject: Re: [PATCH] drm/i915: Eliminate race from gen2/3 page
 flip interrupt handling
Date: Mon, 18 Feb 2013 14:27:24 +0200
Message-ID: <20130218122724.GN9135@intel.com>
References: <1361188671-11639-1-git-send-email-ville.syrjala@linux.intel.com>
	<20130218121609.GG16131@cantiga.alporthouse.com>
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To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
List-Id: intel-gfx@lists.freedesktop.org

On Mon, Feb 18, 2013 at 12:16:09PM +0000, Chris Wilson wrote:
> On Mon, Feb 18, 2013 at 01:57:51PM +0200, ville.syrjala@linux.intel.com w=
rote:
> > From: Ville Syrj=E4l=E4 <ville.syrjala@linux.intel.com>
> > =

> > If the interrupt handler were to process a previous vblank interrupt and
> > the following flip pending interrupt at the same time, the page flip
> > would be complete too soon.
> > =

> > To eliminate this race check the live pending flip status from the ISR
> > register before finishing the page flip.
> =

> Ok, that makes a lot of sense.
> =

> /* We detect FlipDone by looking for the change in PendingFlip from '1'
>  * to '0' on the following vblank, i.e. IIR has the Pendingflip
>  * asserted following the MI_DISPLAY_FLIP, but ISR is deasserted, hence
>  * the flip is completed (no longer pending). Since this doesn't raise an
>  * interrupt per-se, we watch for the change at vblank.
>  */

You want me to include that comment somewhere in the code?

> > Signed-off-by: Ville Syrj=E4l=E4 <ville.syrjala@linux.intel.com>
> Reviewed-by: Chris Wilson <chris@chris-wils
> =

> Time to give it a quick test and make sure it doesn't break a ton of
> assumptions... :)
> -Chris
> =

> -- =

> Chris Wilson, Intel Open Source Technology Centre

-- =

Ville Syrj=E4l=E4
Intel OTC