Re: [PATCH v4 2/7] dt-bindings: display: bridge: Document Renesas R-Car V4H DSC bindings

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

Hi Geert,

On 15/06/2026 12:24, Geert Uytterhoeven wrote:
> Hi Tomi,
> 
> On Mon, 15 Jun 2026 at 08:28, Tomi Valkeinen
> <tomi.valkeinen+renesas@ideasonboard.com> wrote:
>> From: Marek Vasut <marek.vasut+renesas@mailbox.org>
>>
>> The Renesas DSC Display Stream Compression is a bridge embedded in the
>> Renesas R-Car V4H SoC. The bridge performs VESA DSC encoding of up to
>> 8k or 400 Mpixel/s .
>>
>> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
>> [tomi.valkeinen: fix the example]
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
>> Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
>> Acked-by: Conor Dooley <conor.dooley@microchip.com>
> 
> Thanks for the update!
> 
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/display/bridge/renesas,dsc.yaml
>> @@ -0,0 +1,99 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/display/bridge/renesas,dsc.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Renesas R-Car DSC Display Stream Compression
>> +
>> +maintainers:
>> +  - Marek Vasut <marek.vasut+renesas@mailbox.org>
>> +
>> +description: |
>> +  This binding describes the VESA DSC Display Stream Compression encoder
>> +  embedded in the Renesas R-Car V4H SoC. The encoder supports all DSC1.1
>> +  encoding mechanisms, configurable bits-per-pixel, resolution up to 8k.
>> +
>> +properties:
>> +  compatible:
>> +    items:
>> +      - enum:
>> +          - renesas,r8a779g0-dsc
>> +      - const: renesas,rcar-dsc
> 
> Please do not introduce new "renesas,rcar" fallback compatible values,
> unless you are adding new support for a hardware block that is present
> in SoCs belonging to multiple (nowadays I would say at least three)
> R-Car generations.  The DSC is only found in R-Car Gen4 SoCs, so
> "renesas,rcar-gen4-dsc" sounds more appropriate.

Ok.

> However, so far R-Car V4H is the only R-Car Gen4 SoC that has a DSC.

Right. Even "renesas,rcar-gen4-dsc" feels a bit too wide.

None of the other rcar du related bindings define fallback compatibles. 
So maybe we can just keep "renesas,r8a779g0-dsc" and name the file 
"renesas,r8a779g0-dsc.yaml" (which was the review comment I'm trying to 
resolve with this change).

> Even the very similar R-Car V4M does not seem to have it.
> R-Car X5H has DSC-functionality integrated in its DisplayPort TX
> controller, so that seems to be a different implementation?
I'm not that familiar with DSC functionality, but my understanding is 
that it's not DSI or DP specific, it just outputs packed parallel video. 
I couldn't find details about X5H's DSC, it could even be the same block 
(or not).

  Tomi