Re: [PATCH v5 2/4] dt-bindings: media: add Maxim MAX96714 GMSL2 Deserializer

[Conor Dooley]

On Wed, Mar 13, 2024 at 10:49:20AM +0100, Julien Massot wrote:
> Add DT bindings for Maxim MAX96714 GMSL2 Deserializer.
> 
> Signed-off-by: Julien Massot <julien.massot@xxxxxxxxxxxxx>
> ---
> Change since v4:
>  - Add compatible for MAX96714 and use it as a fallback for MAX96714F
>  - Remove extra '|' for decriptions
>  - Reference 'i2c-gate' instead of 'i2c-controller'
> 
> Change since v3:
>  - Renamed file to maxim,max96714.yaml dropped the 'f' suffix
>  - Removed mention to C-PHY since it's not supported by MAX96714 deserializers
>  - Removed bus-type requirement on CSI endpoint since the device only support D-PHY
>  - Removed the clock-lanes property in the dt example
> 
> Change since v2:
>  - remove reg description
>  - rename enable gpio to powerdown
>  - use generic node name: i2c, serializer, deserializer
> ---
>  .../bindings/media/i2c/maxim,max96714.yaml    | 176 ++++++++++++++++++
>  1 file changed, 176 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/i2c/maxim,max96714.yaml
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max96714.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max96714.yaml
> new file mode 100644
> index 000000000000..59b116092834
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/i2c/maxim,max96714.yaml
> @@ -0,0 +1,176 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# Copyright (C) 2024 Collabora Ltd.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/media/i2c/maxim,max96714.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Maxim MAX96714 GMSL2 to CSI-2 Deserializer
> +
> +maintainers:
> +  - Julien Massot <julien.massot@xxxxxxxxxxxxx>
> +
> +description:
> +  The MAX96714 deserializer converts GMSL2 serial inputs into MIPI
> +  CSI-2 D-PHY formatted output. The device allows the GMSL2 link to
> +  simultaneously transmit bidirectional control-channel data while forward
> +  video transmissions are in progress. The MAX96714 can connect to one
> +  remotely located serializer using industry-standard coax or STP
> +  interconnects. The device cans operate in pixel or tunnel mode. In pixel mode
> +  the MAX96714 can select individual video stream, while the tunnel mode forward all
> +  the MIPI data received by the serializer.
> +
> +  The GMSL2 serial link operates at a fixed rate of 3Gbps or 6Gbps in the
> +  forward direction and 187.5Mbps in the reverse direction.
> +  MAX96714F only supports a fixed rate of 3Gbps in the forward direction.
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - enum:
> +          - maxim,max96714

There's only once device here, make it const rather than enum.

> +      - items:
> +          - enum:
> +              - maxim,max96714f
> +          - const: maxim,max96714 # fallback for 'f' variant

Drop the comment btw, it doesn't make sense given you have an enum that
will allow for more devices and it being a fallback is obvious. That
said, given what you told me on the last version
| Yes there are a few differences visible to the software, for example the 
| GMSL
| link rate since MAX96714 support 6 and 3 Gbps, while MAX96714F only 
| supports 3Gbps.
| the registers map is the same, but a few values are not possible with 
| the 'f' version.
I don't think your ordering here is correct. The 96714 should fall back
to the 96714f, not the opposite that you have here, as the f is the
version which supports fewer features.

I think this should be:

oneOf:
  - const: maxim,max96714f
  - items:
      - enum:
          - maxim,max96714
      - const: maxim,max96714f

Cheers,
Conor.

> +
> +  reg:
> +    maxItems: 1
> +
> +  powerdown-gpios:
> +    maxItems: 1
> +    description:
> +      Specifier for the GPIO connected to the PWDNB pin.
> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/properties/port
> +        unevaluatedProperties: false
> +        description: GMSL Input
> +        properties:
> +          endpoint:
> +            $ref: /schemas/media/video-interfaces.yaml#
> +            unevaluatedProperties: false
> +            description:
> +              Endpoint for GMSL2-Link port.
> +
> +      port@1:
> +        $ref: /schemas/graph.yaml#/$defs/port-base
> +        unevaluatedProperties: false
> +        description: CSI-2 Output port
> +
> +        properties:
> +          endpoint:
> +            $ref: /schemas/media/video-interfaces.yaml#
> +            unevaluatedProperties: false
> +
> +            properties:
> +              data-lanes:
> +                minItems: 1
> +                maxItems: 4
> +
> +              lane-polarities:
> +                minItems: 1
> +                maxItems: 5
> +
> +              link-frequencies:
> +                maxItems: 1
> +
> +            required:
> +              - data-lanes
> +
> +    required:
> +      - port@1
> +
> +  i2c-gate:
> +    $ref: /schemas/i2c/i2c-gate.yaml
> +    unevaluatedProperties: false
> +    description:
> +      The MAX96714 will pass through and forward the I2C requests from the
> +      incoming I2C bus over the GMSL2 link. Therefore it supports an i2c-gate
> +      subnode to configure a serializer.
> +
> +  port0-poc-supply:
> +    description: Regulator providing Power over Coax for the GMSL port
> +
> +required:
> +  - compatible
> +  - reg
> +  - ports
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/media/video-interfaces.h>
> +
> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        deserializer@28 {
> +            compatible = "maxim,max96714f", "maxim,max96714";
> +            reg = <0x28>;
> +            powerdown-gpios = <&main_gpio0 37 GPIO_ACTIVE_LOW>;
> +
> +            ports {
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +                port@0 {
> +                    reg = <0>;
> +                    max96714_gmsl_in: endpoint {
> +                        remote-endpoint = <&max96917f_gmsl_out>;
> +                    };
> +                };
> +
> +                port@1 {
> +                    reg = <1>;
> +                    max96714_csi_out: endpoint {
> +                        data-lanes = <1 2 3 4>;
> +                        link-frequencies = /bits/ 64 <400000000>;
> +                        remote-endpoint = <&csi_in>;
> +                    };
> +                };
> +            };
> +
> +            i2c-gate {
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +
> +                serializer@40 {
> +                    compatible = "maxim,max96717f", "maxim,max96717";
> +                    reg = <0x40>;
> +                    gpio-controller;
> +                    #gpio-cells = <2>;
> +                    #clock-cells = <0>;
> +
> +                    ports {
> +                        #address-cells = <1>;
> +                        #size-cells = <0>;
> +
> +                        port@0 {
> +                            reg = <0>;
> +                            max96717f_csi_in: endpoint {
> +                                bus-type = <MEDIA_BUS_TYPE_CSI2_DPHY>;
> +                                data-lanes = <1 2>;
> +                                lane-polarities = <1 0 1>;
> +                                remote-endpoint = <&sensor_out>;
> +                            };
> +                        };
> +
> +                        port@1 {
> +                            reg = <1>;
> +                            max96917f_gmsl_out: endpoint {
> +                                remote-endpoint = <&max96714_gmsl_in>;
> +                            };
> +                        };
> +                    };
> +                };
> +            };
> +        };
> +    };
> +...
> -- 
> 2.44.0
>

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