[PATCH v3 1/4] dt-bindings: display: renesas,rzg2l-du: Document RZ/G2UL DU bindings

[Laurent Pinchart]

On Tue, Aug 20, 2024 at 06:42:48AM +0000, Biju Das wrote:
> Hi Rob and all,
> 
> > -----Original Message-----
> > From: Biju Das
> > Sent: Monday, August 19, 2024 1:37 PM
> > Subject: RE: [PATCH v3 1/4] dt-bindings: display: renesas,rzg2l-du: Document RZ/G2UL DU bindings
> > 
> > Hi Laurent and Rob,
> > 
> > Thanks for the feedback
> > 
> > > -----Original Message-----
> > > From: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > > Sent: Tuesday, August 13, 2024 8:39 PM
> > > Subject: Re: [PATCH v3 1/4] dt-bindings: display: renesas,rzg2l-du:
> > > Document RZ/G2UL DU bindings
> > >
> > > Hi Rob,
> > >
> > > On Tue, Aug 13, 2024 at 10:32:20AM -0600, Rob Herring wrote:
> > > > On Mon, Aug 05, 2024 at 04:52:35PM +0100, Biju Das wrote:
> > > > > Document DU found in RZ/G2UL SoC. The DU block is identical to
> > > > > RZ/G2L SoC, but has only DPI interface.
> > > > >
> > > > > While at it, add missing required property port at 1 for RZ/G2L and
> > > > > RZ/V2L SoCs. Currently there is no user for the DPI interface and
> > > > > hence there won't be any ABI breakage for adding port at 1 as
> > > > > required property for RZ/G2L and RZ/V2L SoCs.
> > > > >
> > > > > Signed-off-by: Biju Das <biju.das.jz at bp.renesas.com>
> > > > > ---
> > > > > v2->v3:
> > > > >  * Replaced ports->port property for RZ/G2UL as it supports only DPI.
> > > > >    and retained ports property for RZ/{G2L,V2L} as it supports both DSI
> > > > >    and DPI output interface.
> > > >
> > > > Why? Having port and ports is just a needless complication.
> > >
> > > I agree that making the ports node mandatory, even when the device has
> > > a single port, will simplify the bindings. In hindsight we should never have made ports optional,
> > but that can't be changed.
> > >
> > > > >  * Added missing blank line before example.
> > > > >  * Dropped tags from Conor and Geert as there are new changes.
> > > > > v1->v2:
> > > > >  * Updated commit description related to non ABI breakage.
> > > > >  * Added Ack from Conor.
> > > > > ---
> > > > >  .../bindings/display/renesas,rzg2l-du.yaml    | 35 +++++++++++++++++--
> > > > >  1 file changed, 32 insertions(+), 3 deletions(-)
> > > > >
> > > > > diff --git
> > > > > a/Documentation/devicetree/bindings/display/renesas,rzg2l-du.yaml
> > > > > b/Documentation/devicetree/bindings/display/renesas,rzg2l-du.yaml
> > > > > index 08e5b9478051..ca01bf26c4c0 100644
> > > > > ---
> > > > > a/Documentation/devicetree/bindings/display/renesas,rzg2l-du.yaml
> > > > > +++ b/Documentation/devicetree/bindings/display/renesas,rzg2l-du.y
> > > > > +++ am
> > > > > +++ l
> > > > > @@ -18,6 +18,7 @@ properties:
> > > > >    compatible:
> > > > >      oneOf:
> > > > >        - enum:
> > > > > +          - renesas,r9a07g043u-du # RZ/G2UL
> > > > >            - renesas,r9a07g044-du # RZ/G2{L,LC}
> > > > >        - items:
> > > > >            - enum:
> > > > > @@ -60,8 +61,9 @@ properties:
> > > > >          $ref: /schemas/graph.yaml#/properties/port
> > > > >          unevaluatedProperties: false
> > > > >
> > > > > -    required:
> > > > > -      - port at 0
> > > > > +  port:
> > > > > +    $ref: /schemas/graph.yaml#/properties/port
> > > > > +    description: Connection to the DU output video port.
> > > > >
> > > > >      unevaluatedProperties: false
> > > > >
> > > > > @@ -83,11 +85,38 @@ required:
> > > > >    - clock-names
> > > > >    - resets
> > > > >    - power-domains
> > > > > -  - ports
> > > > >    - renesas,vsps
> > > > >
> > > > >  additionalProperties: false
> > > > >
> > > > > +allOf:
> > > > > +  - if:
> > > > > +      properties:
> > > > > +        compatible:
> > > > > +          contains:
> > > > > +            const: renesas,r9a07g043u-du
> > > > > +    then:
> > > > > +      properties:
> > > > > +        port:
> > > > > +          description: DPI
> > > >
> > > > This is equivalent to 'port at 0'. IMO, this case should have a 'port at 1'
> > > > node so that DPI interface is *always* the same port.
> > >
> > > That's what Biju did in the previous version, and I recommended to
> > > number the ports based on hardware indices, not types. Mapping port
> > > numbers to the hardware documentation makes it more consistent for DT
> > > writers, makes the logic simpler to understand (in my opinion, based
> > > on my experience with the R-Car
> > > DU) on the driver side, but most importantly, type-based numbering
> > > wouldn't scale as SoCs could have multiple ports of the same type
> > > (we've seen that happening with R-Car).
> > 
> > OK, I will send bindings based on hardware indices.
> 
> I get a warning, if I use ports and port at 0 for single port. I don't
> see this warning if I use ports and port at 1
> 
> arch/arm64/boot/dts/renesas/r9a07g043u.dtsi:169.9-178.5: Warning (graph_child_address): /soc/display at 10890000/ports: graph node has single child node 'port at 0', #address-cells/#size-cells are not necessary
> 
> Can we fix the dt-schema to getting consistent results for single port
> usage involving ports?

I would like that too.

> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: renesas,r9a07g043u-du
> +    then:
> +      properties:
> +        ports:
> +          properties:
> +            port at 0:
> +              description: DPI
> +
> +          required:
> +            - port at 0

-- 
Regards,

Laurent Pinchart