Re: [PATCH v9 02/10] dt-bindings: display: Document Renesas RZ/G3E display subsystem

[Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>]

Hi Krzysztof,
Thanks for your review.

On Wed, Nov 04, 2026 at 11:19:47AM +0100, Krzysztof Kozlowski wrote:
> On Fri, Oct 23, 2026 at 06:47:35PM +0200, Tommaso Merciai wrote:
> > The Renesas RZ/G3E (R9A09G047) SoC has two LCD Controllers, LCDC0 and
> > LCDC1, each containing a Display Unit (DU). The two DUs are separate
> > instances of the same IP, with their own registers, interrupt, clocks,
> > reset and VSP, and are therefore described by two device tree nodes.
> > 
> > The DSI encoder and channel 1 of the LVDS encoder can be fed by either
> > DU, the source being selected at runtime. Driving those outputs from
> > either DU requires handling both DUs as a single display subsystem.
> > 
> > Document the renesas,r9a09g047-display-subsystem node that groups the
> > two Display Unit instances.
> > 
> > Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
> > ---
> > v8->v9:
> >  - New patch.
> > 
> >  .../renesas,r9a09g047-display-subsystem.yaml  | 44 +++++++++++++++++++
> >  MAINTAINERS                                   |  1 +
> >  2 files changed, 45 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/display/renesas,r9a09g047-display-subsystem.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/display/renesas,r9a09g047-display-subsystem.yaml b/Documentation/devicetree/bindings/display/renesas,r9a09g047-display-subsystem.yaml
> > new file mode 100644
> > index 000000000000..e23cc53a1fea
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/renesas,r9a09g047-display-subsystem.yaml
> > @@ -0,0 +1,44 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/display/renesas,r9a09g047-display-subsystem.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Renesas RZ/G3E Display Subsystem
> > +
> > +maintainers:
> > +  - Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
> > +
> > +description:
> > +  The Renesas RZ/G3E display subsystem is a virtual device needed to list the
> 
> We do not take bindings for virtual devices, because you do not need
> them. Instantiate your driver from existing bindings, instead of
> creating fake device just for Linux drivers.

Thanks for sharing.

I will drop this patch into the next version, also I will
instantiate the driver from existing bindings like you suggested.

Kind regards,
Tommaso

> 
> > +  Display Unit instances that comprise the graphics subsystem.
> > +
> > +properties:
> > +  compatible:
> > +    const: renesas,r9a09g047-display-subsystem
> > +
> > +  ports:
> > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> 
> Properties have only one type and ports is already defined as object for
> graph.
> 
> Why isn't this a graph?
> 
> Best regards,
> Krzysztof
>