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From:   Chen-Yu Tsai <wenst@chromium.org>
Date:   Thu, 30 Mar 2023 12:11:18 +0800
Message-ID: <CAGXv+5HFP-1SFFBsUneyVT-42b3_6BPtQ-CkULmUT6v0pUoLbA@mail.gmail.com>
Subject: Re: [PATCH v3 0/5] Add generic-display-mux driver and bindings
To:     Jagan Teki <jagan@amarulasolutions.com>
Cc:     Pin-yen Lin <treapking@chromium.org>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Nicolas Boichat <drinkcat@chromium.org>,
        Robert Foss <rfoss@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Jonas Karlman <jonas@kwiboo.se>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        devicetree@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        linux-mediatek@lists.infradead.org,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        chrome-platform@lists.linux.dev,
        Guenter Roeck <groeck@chromium.org>,
        linux-arm-kernel@lists.infradead.org
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On Thu, Mar 30, 2023 at 2:10=E2=80=AFAM Jagan Teki <jagan@amarulasolutions.=
com> wrote:
>
> On Sat, Feb 18, 2023 at 4:47=E2=80=AFPM Pin-yen Lin <treapking@chromium.o=
rg> wrote:
> >
> > This series is developed for and tested on MT8173 board, and the layout=
 is:
> >
> >                                   /-- anx7688
> > -- MT8173 HDMI bridge -- GPIO mux
> >                                   \-- native HDMI
>
> What is the part number of this GPIO mux? Does mux gpio interrupt
> based and able to switch output HDMI and DP. If so, how this gpio
> interrupt is different than the HPD in native HDMI? I mean does HPD
> have any detection bottlenecks with mux gpio interrupt?

It's a full blown HDMI 1:2 demultiplexer, so DDC and HPD signals are muxed
as well. The anx7688 handles all the Type-C stuff, and our EC talks to it.
If HDMI output from the SoC needs to be muxed over for DP alt-mode, the EC
will signal the SoC.

> I do have GPIO Mux that input DSI and two outputs DMD/HDMI Input and
> HDMI Out. 2x1 with 1x2 mux.
>
> I'm thinking having a generic mux to select the specific out number of
> outputs with associated interface outputs can be a viable solution to
> address all use cases here.

AFAIK DRM doesn't allow dynamically changing the constitution of a display
pipeline, so it doesn't really work out for us.

If you're just muxing between different outputs with passive/dumb bridges,
it may still work for you.

ChenYu