linux-kernel - Re: [PATCH RESEND 3/4] dt-bindings: drm/bridge: analogix-anx78xx: support bypass GPIO

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Date:   Wed, 11 Dec 2019 14:34:02 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Archit Taneja <architt@...eaurora.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Matthias Brugger <mbrugger@...e.com>,
        Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH RESEND 3/4] dt-bindings: drm/bridge: analogix-anx78xx:
 support bypass GPIO

On Mon, Dec 9, 2019 at 11:32 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
Hi Laurent,
> You may have used a proportional font when writing this, the | doesn't
> align with anything using a fixed font. Do I assume correctly that the
> hardware multiplexer is actually a demultiplexer with one input and two
> outputs ?
>                                      +-----------+
> +---------+         +------+    /--> | HDMI      |
> | MT8173  |  HDMI   |   -->| --/     | Connector |
> |  HDMI   | ------> |--/   |         +-----------+
> | Encoder |         |    ->| --\     +-----------+      +-----------+
> +---------+         +------+    \--> | ANX7688   | ---> | USB-C     |
>                                      | Bridge    |      | Connector |
>                                      +-----------+      +-----------+
>
Sorry for not noticing the font issue, this graph is correct.

> > There's a hardware mux that takes mt8173 hdmi as input and has 2
> > output port: native hdmi and anx7688 bridge.
> > If gpio is active, we would like it to go to HDMI.
> >
> > Previous approach is to make hardware mux a generic gpio mux bridge,
> > but this is probably a very rare use case that is only for
> > mt8173.(https://lore.kernel.org/lkml/57723AD2.8020806@codeaurora.org/)
> > We merge the mux and anx7688 to a single bridge and leave this as an
> > optional feature in this time.
>
> I think that's a better approach, at least at the DT level. The HDMI
> demultiplexer should be represented as a DT node with 3 ports (one input
> and two outputs) with a control GPIO.
>
I've resend the original gpio mux driver. So for anx7688 there's 1
input and 1 output.

Thanks