linux-kernel - Re: [PATCH v3 1/2] dt-bindings: display: bridge: Add bindings for Chipone ICN6211

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Message-ID: <CAMty3ZDAz28BWUJRLW0LwmJ5v6dOPZmxRzfzseoQMiMkTVBW6Q@mail.gmail.com>
Date:   Thu, 4 Mar 2021 14:40:15 +0530
From:   Jagan Teki <jagan@...rulasolutions.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-amarula <linux-amarula@...rulasolutions.com>
Subject: Re: [PATCH v3 1/2] dt-bindings: display: bridge: Add bindings for
 Chipone ICN6211

Hi Laurent,

On Thu, Mar 4, 2021 at 4:29 AM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Jagan,
>
> On Wed, Mar 03, 2021 at 08:08:35PM +0530, Jagan Teki wrote:
> > On Wed, Feb 24, 2021 at 6:44 PM Laurent Pinchart wrote:
> > > On Wed, Feb 24, 2021 at 06:07:43PM +0530, Jagan Teki wrote:
> > > > On Mon, Feb 15, 2021 at 5:48 PM Laurent Pinchart wrote:
> > > > > On Sun, Feb 14, 2021 at 11:22:10PM +0530, Jagan Teki wrote:
> > > > > > ICN6211 is MIPI-DSI to RGB Convertor bridge from Chipone.
> > > > > >
> > > > > > It has a flexible configuration of MIPI DSI signal input and
> > > > > > produce RGB565, RGB666, RGB888 output format.
> > > > > >
> > > > > > Add dt-bingings for it.
> > > > > >
> > > > > > Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>
> > > > > > ---
> > > > > > Changes for v3:
> > > > > > - updated to new dt-bindings style
> > > > > >
> > > > > >  .../display/bridge/chipone,icn6211.yaml       | 90 +++++++++++++++++++
> > > > > >  1 file changed, 90 insertions(+)
> > > > > >  create mode 100644 Documentation/devicetree/bindings/display/bridge/chipone,icn6211.yaml
> > > > > >
> > > > > > diff --git a/Documentation/devicetree/bindings/display/bridge/chipone,icn6211.yaml b/Documentation/devicetree/bindings/display/bridge/chipone,icn6211.yaml
> > > > > > new file mode 100644
> > > > > > index 000000000000..13764f13fe46
> > > > > > --- /dev/null
> > > > > > +++ b/Documentation/devicetree/bindings/display/bridge/chipone,icn6211.yaml
> > > > > > @@ -0,0 +1,90 @@
> > > > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > > > +%YAML 1.2
> > > > > > +---
> > > > > > +$id: http://devicetree.org/schemas/display/bridge/chipone,icn6211.yaml#
> > > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > > +
> > > > > > +title: Chipone ICN6211 MIPI-DSI to RGB Converter bridge
> > > > > > +
> > > > > > +maintainers:
> > > > > > +  - Jagan Teki <jagan@...rulasolutions.com>
> > > > > > +
> > > > > > +description: |
> > > > > > +  ICN6211 is MIPI-DSI to RGB Convertor bridge from chipone.
> > > > > > +
> > > > > > +  It has a flexible configuration of MIPI DSI signal input and
> > > > > > +  produce RGB565, RGB666, RGB888 output format.
> > > > >
> > > > > How does one select between the output formats ? Should the output
> > > > > connection option be described in the device tree ?
> > > >
> > > > I think that is a good option to select output formats via dts. what
> > > > if it makes it a generic property like data-lanes? since it is common
> > > > across many other bridges.
> > >
> > > Describing the output connection in the device tree sounds like a good
> > > idea indeed. The bus-width property could be used for this, maybe along
> > > the lines of
> > > https://lore.kernel.org/dri-devel/20201013020619.GG3942@pendragon.ideasonboard.com/.
> >
> > I have seen an issue by passing bus-width where the same bus-with 24
> > can use by RGB888 and RGB666 according to
> > mipi_dsi_pixel_format_to_bpp. Having a default RGB888 format now and
> > update it when it supports properly, can be a good Idea I thought of.
> > Let me know if you have any comments?
>
> I'm fine with hardcoding a default for now. If a given bus wiring (which
> is described in DT by bus-width) can transport different formats, that's
> something that should be configured dynamically, either by querying what
> format a sink (such as a panel) requires, or if both the source and the
> sink can support different formats, possibly by involving userspace in
> the selection.

Not sure how we can get userspace involvement in DRM here, but if
source and sink can have different formats then having precedence to
the source would be a good option as it handles low-level
configuration for formats.

Look like it is worth trying-feature. Maybe we can come up with some
RFC and have a discussion.

Jagan.