linux-kernel - Re: [PATCH 3/3] drm/omap: displays: encoder-tpd12s015: Support for hot plug detection

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Message-ID: <2146476.yg7iIlQTUW@avalon>
Date:   Tue, 23 May 2017 13:42:25 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Tomi Valkeinen <tomi.valkeinen@...com>
Cc:     Peter Ujfalusi <peter.ujfalusi@...com>, airlied@...ux.ie,
        jsarha@...com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] drm/omap: displays: encoder-tpd12s015: Support for hot plug detection

Hi Tomi,

On Tuesday 23 May 2017 13:25:34 Tomi Valkeinen wrote:
> On 23/05/17 12:48, Laurent Pinchart wrote:
> > As the connector code can handle GPIO HPD thanks to patch 2/3, why does it
> > have to be duplicated here ? I agree that encoders should support
> > reporting of hotplug events when the HPD signal is connected to an
> > encoder, but if it's connected to a GPIO, it seems to me that it should
> > be the sole responsibility of the connector code to handle it.
> 
> The HPD line goes from the connector to TPD12S015. From TPD12S015
> another line goes to the SoCs GPIO.

Isn't it the same signal, just with glitches filtered ? The TPD12S015 is an 
ESD clamp, level shifter and DC-DC converter, if it wasn't for the two control 
inputs CT_CP_HPD and LS_OE, we could probably do without a driver. I wouldn't 
add HPD support to this driver, as the chip really can't detect HPD.

-- 
Regards,

Laurent Pinchart