From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?ISO-8859-1?Q?=22David_M=FCller_=28ELSOFT_AG=29=22?=
	<d.mueller@elsoft.ch>
Subject: Re: [DVO][PATCH] drm/i915: Fall back to bit banging
 mode for DVO transmitter detection
Date: Fri, 19 Apr 2013 12:54:00 +0200
Message-ID: <51712248.8010504@elsoft.ch>
References: <5171034E.1020204@elsoft.ch>
	<20130419091414.GS6169@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>
In-Reply-To: <20130419091414.GS6169@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, dri-devel@lists.freedesktop.org
List-Id: dri-devel@lists.freedesktop.org

Daniel Vetter wrote:
> On Fri, Apr 19, 2013 at 10:41:50AM +0200, "David M=FCller (ELSOFT AG)" wr=
ote:
>> +		/* GMBUS NAK handling seems to be unstable, hence let the
>> +		 * transmitter detection run in bit banging mode for now.
>> +		 */
>> +		intel_gmbus_force_bit(i2c, true);
>> +
>> +		dvoinit =3D dvo->dev_ops->init(&intel_dvo->dev, i2c);
>> +
>> +		intel_gmbus_force_bit(i2c, false);
> =

> Shouldn't we keep the dvo i2c line in bit-banging mode always, i.e.
> restore gmbus mode only when dvo init failed?
> =

> I suspect that for fickle hw not just init will fail ...

As far as i can tell, the critical part is the NAK handling.

Dave