linux-kernel - Re: [PATCH v2 1/2] dt-bindings: drm/bridge: anx7625: add DPI flag and swing setting

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Message-ID: <CAL_JsqJ1B6JzpdgtP=ZNtWasjW5R0rYyUGV3RTDxT1LPa1rz5w@mail.gmail.com>
Date:   Fri, 22 Jan 2021 10:16:02 -0600
From:   Rob Herring <robh@...nel.org>
To:     Xin Ji <xji@...logixsemi.com>
Cc:     David Airlie <airlied@...ux.ie>,
        Nicolas Boichat <drinkcat@...gle.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Maxime Ripard <mripard@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Ricardo Cañuelo <ricardo.canuelo@...labora.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree@...r.kernel.org, Sheng Pan <span@...logixsemi.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: drm/bridge: anx7625: add DPI flag and
 swing setting

On Tue, Jan 12, 2021 at 2:57 AM Xin Ji <xji@...logixsemi.com> wrote:
>
> Hi Rob Herring, thanks for the comments.
>
> On Mon, Jan 11, 2021 at 04:14:35PM -0600, Rob Herring wrote:
> > On Thu, Dec 31, 2020 at 10:21:12AM +0800, Xin Ji wrote:
> > > Add DPI flag for distinguish MIPI input signal type, DSI or DPI. Add
> > > swing setting for adjusting DP tx PHY swing
> > >
> > > Signed-off-by: Xin Ji <xji@...logixsemi.com>
> > > ---
> > >  .../bindings/display/bridge/analogix,anx7625.yaml  | 25 ++++++++++++++++++++--
> > >  1 file changed, 23 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml b/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> > > index 60585a4..4eb0ea3 100644
> > > --- a/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> > > +++ b/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> > > @@ -34,6 +34,16 @@ properties:
> > >      description: used for reset chip control, RESET_N pin B7.
> > >      maxItems: 1
> > >
> > > +  analogix,swing-setting:
> > > +    type: uint8-array
> >
> > Humm, this should have be rejected by the meta-schema.
> We needs define an array to adjust DP tx PHY swing, the developer hopes these
> settings are changeable, so I moved the register data to DT. Can you
> give me some suggestion if it is rejected by the meta-schema?
> >
> > > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> >
> > This is how types are defined other than boolean or nodes (object).
> >
> > > +    description: an array of swing register setting for DP tx PHY
> > > +
> > > +  analogix,mipi-dpi-in:
> > > +    type: int
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    description: indicate the MIPI rx signal type is DPI or DSI
> >
> > Why does this need to be in DT, you should be able to determine this
> > based on what you are connected to.
> As the anx7625 can receive MIPI DSI and DPI data (depends on hardware
> implement, we have a project which have two anx7625, one is DSI input,
> the other is DPI input), we needs to let driver know what kind of MIPI
> rx signal input. And there is no other way to tell driver the MIPI rx
> signal type, we needs define this flag.

That's only true if what's driving the output is a single h/w block
that can drive either. But typically you have 2 blocks: an LCD
controller driving parallel signals and a DSI controller in front of
it doing parallel to DSI conversion. The anx7625 would be connected to
the LCD controller or DSI controller via the graph binding depending
on the h/w connection.

However, if you do need this, then let's extend video-interfaces.yaml
'bus-type' to include DSI (it already has parallel).

Rob