linux-kernel - Re: [PATCH RESEND 3/4] dt-bindings: drm/bridge: Add GPIO display mux binding

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Message-ID: <CAJMQK-jGw8kJFNjoHjeZUL+3NCiOS2hgGERnAnMwNsL_cm_J=Q@mail.gmail.com>
Date:   Fri, 20 Dec 2019 11:57:35 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Rob Herring <robh@...nel.org>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        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: Add GPIO display mux binding

On Fri, Dec 20, 2019 at 4:48 AM Rob Herring <robh@...nel.org> wrote:
>
> On Mon, Dec 16, 2019 at 03:16:23PM +0800, Hsin-Yi Wang wrote:
> > On Sat, Dec 14, 2019 at 5:29 AM Rob Herring <robh+dt@...nel.org> wrote:
> > >
> > > On Wed, Dec 11, 2019 at 12:19 AM Hsin-Yi Wang <hsinyi@...omium.org> wrote:
> > > >
> > > > From: Nicolas Boichat <drinkcat@...omium.org>
> > > >
> > > > Add bindings for Generic GPIO mux driver.
> > > >
> > > > Signed-off-by: Nicolas Boichat <drinkcat@...omium.org>
> > > > Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> > > > ---
> > > > Change from RFC to v1:
> > > > - txt to yaml
> > > > ---
> > > >  .../bindings/display/bridge/gpio-mux.yaml     | 89 +++++++++++++++++++
> > > >  1 file changed, 89 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/display/bridge/gpio-mux.yaml
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/bridge/gpio-mux.yaml b/Documentation/devicetree/bindings/display/bridge/gpio-mux.yaml
> > > > new file mode 100644
> > > > index 000000000000..cef098749066
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/display/bridge/gpio-mux.yaml
> > > > @@ -0,0 +1,89 @@
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/display/bridge/gpio-mux.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Generic display mux (1 input, 2 outputs)
> > >
> > > What makes it generic? Doesn't the mux chip have power supply,
> > > possibly a reset line or not, etc.? What about a mux where the GPIO
> > > controls the mux?
> > >
> > > Generally, we avoid 'generic' bindings because h/w is rarely generic.
> > > You can have a generic driver which works on multiple devices.
> > >
> > Then how about making it mt8173-oak-gpio-mux? Since this is currently
> > only used in this board.
>
> Isn't there an underlying part# you can use? Or if you can point me to
> multiple chips implementing the same thing, then maybe a generic binding
> is fine.
There are some similar chips, for example:
https://www.paradetech.com/zh-hant/%E7%94%A2%E5%93%81%E4%BB%8B%E7%B4%B9/ps8223-3-0gbps-hdmi-12-demultiplexer/
and http://www.ti.com/lit/ds/symlink/ts3dv642.pdf
If they are used in a similar way
(https://lore.kernel.org/lkml/CANMq1KDDEzPWhByEtn-EjNcg+ofVT2MW-hOXANGooYFOYJ35VA@mail.gmail.com/),
they would need such driver. But currently we only know that mt8173
oak board have this use case.
>
> Rob