linux-kernel - Re: [PATCH v2 8/9] media: dt-bindings: Add Intel Displayport RX IP

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Date: Mon, 26 Feb 2024 10:12:56 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Paweł Anikiel <panikiel@...gle.com>, airlied@...il.com,
 akpm@...ux-foundation.org, conor+dt@...nel.org, daniel@...ll.ch,
 dinguyen@...nel.org, hverkuil-cisco@...all.nl,
 krzysztof.kozlowski+dt@...aro.org, maarten.lankhorst@...ux.intel.com,
 mchehab@...nel.org, mripard@...nel.org, robh+dt@...nel.org,
 tzimmermann@...e.de
Cc: devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 chromeos-krk-upstreaming@...gle.com, ribalda@...omium.org
Subject: Re: [PATCH v2 8/9] media: dt-bindings: Add Intel Displayport RX IP

On 21/02/2024 17:02, Paweł Anikiel wrote:
> The Intel Displayport RX IP is a part of the DisplayPort Intel FPGA IP
> Core. It implements a DisplayPort 1.4 receiver capable of HBR3 video
> capture and Multi-Stream Transport. The user guide can be found here:
> 
> https://www.intel.com/programmable/technical-pdfs/683273.pdf
> 
> Signed-off-by: Paweł Anikiel <panikiel@...gle.com>
> ---
>  .../devicetree/bindings/media/intel,dprx.yaml | 160 ++++++++++++++++++
>  1 file changed, 160 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/intel,dprx.yaml
> 
> diff --git a/Documentation/devicetree/bindings/media/intel,dprx.yaml b/Documentation/devicetree/bindings/media/intel,dprx.yaml
> new file mode 100644
> index 000000000000..31025f2d5dcd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/intel,dprx.yaml
> @@ -0,0 +1,160 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/media/intel,dprx.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Intel DisplayPort RX IP
> +
> +maintainers:
> +  - Paweł Anikiel <panikiel@...gle.com>
> +
> +description: |
> +  The Intel Displayport RX IP is a part of the DisplayPort Intel FPGA IP
> +  Core. It implements a DisplayPort 1.4 receiver capable of HBR3 video
> +  capture and Multi-Stream Transport.
> +
> +  The IP features a large number of configuration parameters, found at:
> +  https://www.intel.com/content/www/us/en/docs/programmable/683273/23-3-20-0-1/sink-parameters.html
> +
> +  The following parameters have to be enabled:
> +    - Support DisplayPort sink
> +    - Enable GPU control
> +  The following parameters' values have to be set in the devicetree:
> +    - RX maximum link rate
> +    - Maximum lane count
> +    - Support MST
> +    - Max stream count (only if Support MST is enabled)
> +
> +properties:
> +  compatible:
> +    const: intel,dprx-20.0.1
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  intel,max-link-rate:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: Max link rate configuration parameter

Please do not duplicate property name in description. It's useless.
Instead explain what is this responsible for.

Why max-link-rate would differ for the same dprx-20.0.1? And why
standard properties cannot be used?

Same for all questions below.

> +
> +  intel,max-lane-count:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: Max lane count configuration parameter
> +
> +  intel,multi-stream-support:
> +    type: boolean
> +    description: Multi-Stream Transport support configuration parameter
> +
> +  intel,max-stream-count:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: Max stream count configuration parameter
> +
> +  port:
> +    $ref: /schemas/graph.yaml#/properties/port
> +    description: SST main link

I don't understand why you have both port and ports. Shouldn't this be
under ports?

> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: MST virtual channel 0 or SST main link
> +
> +      port@1:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: MST virtual channel 1
> +
> +      port@2:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: MST virtual channel 2
> +
> +      port@3:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        description: MST virtual channel 3
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +
> +allOf:
> +  - if:
> +      required:
> +        - intel,multi-stream-support
> +    then:
> +      required:
> +        - intel,max-stream-count
> +        - ports
> +    else:
> +      required:
> +        - port


Best regards,
Krzysztof