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 v2 1/4] drm/i915: Don't allow ring tail to
 reach the same cacheline as head
Date: Thu, 29 Nov 2012 13:25:12 +0200
Message-ID: <20121129112512.GD21547@intel.com>
References: <1354041298-18898-1-git-send-email-ville.syrjala@linux.intel.com>
	<1354041298-18898-2-git-send-email-ville.syrjala@linux.intel.com>
	<20121128204546.GA3202@phenom.ffwll.local>
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Return-path: <intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org>
Received: from mga03.intel.com (mga03.intel.com [143.182.124.21])
	by gabe.freedesktop.org (Postfix) with ESMTP id 92EBAE6533
	for <intel-gfx@lists.freedesktop.org>;
	Thu, 29 Nov 2012 03:25:19 -0800 (PST)
Content-Disposition: inline
In-Reply-To: <20121128204546.GA3202@phenom.ffwll.local>
List-Unsubscribe: <http://lists.freedesktop.org/mailman/options/intel-gfx>,
	<mailto:intel-gfx-request@lists.freedesktop.org?subject=unsubscribe>
List-Archive: <http://lists.freedesktop.org/archives/intel-gfx>
List-Post: <mailto:intel-gfx@lists.freedesktop.org>
List-Help: <mailto:intel-gfx-request@lists.freedesktop.org?subject=help>
List-Subscribe: <http://lists.freedesktop.org/mailman/listinfo/intel-gfx>,
	<mailto:intel-gfx-request@lists.freedesktop.org?subject=subscribe>
Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org
Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org
To: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org
List-Id: intel-gfx@lists.freedesktop.org

On Wed, Nov 28, 2012 at 09:45:46PM +0100, Daniel Vetter wrote:
> On Tue, Nov 27, 2012 at 08:34:55PM +0200, ville.syrjala@linux.intel.com w=
rote:
> > From: Ville Syrj=E4l=E4 <ville.syrjala@linux.intel.com>
> > =

> > From BSpec:
> > "If the Ring Buffer Head Pointer and the Tail Pointer are on the same
> > cacheline, the Head Pointer must not be greater than the Tail
> > Pointer."
> > =

> > The easiest way to enforce this is to reduce the reported ring space.
> > =

> > References:
> > Gen2 BSpec "1. Programming Environment" / "1.4.4.6 Ring Buffer Use"
> > Gen3 BSpec "vol1c Memory Interface Functions" / "2.3.4.5 Ring Buffer Us=
e"
> > Gen4+ BSpec "vol1c Memory Interface and Command Stream" / "5.3.4.5 Ring=
 Buffer Use"
> > =

> > v2: Include the exact BSpec references in the description
> > =

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

> Another small bikeshed for this one: Less magic numbers with
> =

> #define RING_FREE_SPACE 64

Can do. And since the number will only appear in one place, I think
I'll stick the BSpec references into a comment above it.

-- =

Ville Syrj=E4l=E4
Intel OTC