Re: [PATCH v3] drm/bridge/sii902x: Fix EDID readback

From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
	Simon Horman <horms@verge.net.au>,
	Wolfram Sang <wsa@the-dreams.de>, Dave Airlie <airlied@linux.ie>,
	Boris BREZILLON <boris.brezillon@free-electrons.com>,
	Chris Paterson <Chris.Paterson2@renesas.com>,
	"open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
	Biju Das <biju.das@bp.renesas.com>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Mark Brown <broonie@kernel.org>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Peter Rosin <peda@axentia.se>,
	"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>
Subject: Re: [PATCH v3] drm/bridge/sii902x: Fix EDID readback
Date: Thu, 15 Nov 2018 17:54:44 +0100	[thread overview]
Message-ID: <20181115175444.3d0fce9c@bbrezillon> (raw)
In-Reply-To: <TY1PR01MB1770CD25E936A7DE3421E61DC0DC0@TY1PR01MB1770.jpnprd01.prod.outlook.com>

On Thu, 15 Nov 2018 11:39:30 +0000
Fabrizio Castro <fabrizio.castro@bp.renesas.com> wrote:

> Hello Boris,
> 
> > From: Boris Brezillon <boris.brezillon@bootlin.com>
> > Sent: 15 November 2018 10:16
> > Subject: Re: [PATCH v3] drm/bridge/sii902x: Fix EDID readback
> >
> > On Thu, 15 Nov 2018 11:13:52 +0100
> > Linus Walleij <linus.walleij@linaro.org> wrote:
> >  
> > > On Tue, Nov 6, 2018 at 12:52 PM Fabrizio Castro
> > > <fabrizio.castro@bp.renesas.com> wrote:
> > >  
> > > > While adding SiI9022A support to the iwg23s board, it came
> > > > up that when the HDMI transmitter is in pass through mode the
> > > > device is not compliant with the I2C specification anymore,
> > > > as it requires a far bigger tbuf, due to a delay the HDMI
> > > > transmitter is adding when relaying the STOP condition on the
> > > > monitor i2c side of things.
> > > >
> > > > When not providing an appropriate delay after the STOP condition
> > > > the i2c bus would get stuck. Also, any other traffic on the bus
> > > > while talking to the monitor may cause the transaction to fail
> > > > or even cause issues with the i2c bus as well.
> > > >
> > > > I2c-gates seemed to reach consent as a possible way to address
> > > > these issues, and as such this patch is implementing a solution
> > > > based on that. Since others are clearly relying on the current
> > > > implementation of the driver, this patch won't require any DT
> > > > changes.
> > > >
> > > > Since we don't want any interference during the DDC Bus
> > > > Request/Grant procedure and while talking to the monitor, we
> > > > have to use the adapter locking primitives rather than the
> > > > i2c-mux locking primitives.
> > > >
> > > > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> > > >
> > > > ---
> > > > v2->v3:
> > > > * Incorporated comments from Boris Brezillon and Peter Rosin  
> > >
> > > Acked-by: Linus Walleij <linus.walleij@linaro.org>
> > >
> > > Do you need help to apply this to drm-misc or do you
> > > have commit access?  
> >
> > I can do it if needed.  
> 
> Yes, please, your help is very much appreciated.

Queued to drm-misc-next.

Thanks,

Boris
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