Re: [PATCH v3 2/4] dt-bindings: media: add Maxim MAX96714F GMSL2 Deserializer

[Sakari Ailus]

Hi Julien,

On Thu, Jan 11, 2024 at 02:03:47PM +0100, Julien Massot wrote:
> Add DT bindings for Maxim MAX96714F GMSL2 Deserializer.
> 
> Signed-off-by: Julien Massot <julien.massot@xxxxxxxxxxxxx>
> 
> ---
> Change since v2:
>  - remove reg description
>  - rename enable gpio to powerdown
>  - use generic node name: i2c, serializer, deserializer
> ---
>  .../bindings/media/i2c/maxim,max96714f.yaml   | 171 ++++++++++++++++++
>  1 file changed, 171 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml
> new file mode 100644
> index 000000000000..2423d166c954
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml
> @@ -0,0 +1,171 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# Copyright (C) 2024 Collabora Ltd.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/media/i2c/maxim,max96714f.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Maxim MAX96714 GMSL2 to CSI-2 Deserializer
> +
> +maintainers:
> +  - Julien Massot <julien.massot@xxxxxxxxxxxxx>
> +
> +description: |
> +  The MAX96714F deserializer converts GMSL2 serial inputs into MIPI
> +  CSI-2 D-PHY or C-PHY formatted output. The device allows the GMSL2 link to
> +  simultaneously transmit bidirectional control-channel data while forward
> +  video transmissions are in progress. The MAX96714F 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 MAX96714F 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 in the
> +  forward direction and 187.5Mbps in the reverse direction.
> +
> +properties:
> +  compatible:
> +    const: maxim,max96714f
> +
> +  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
> +
> +              link-frequencies:
> +                maxItems: 1
> +
> +              bus-type:
> +                enum:
> +                  - 4 # MEDIA_BUS_TYPE_CSI2_DPHY

MEDIA_BUS_TYPE_CSI2_CPHY (1) is missing. Even if the driver doesn't support
it, it would be best to list it here.

> +
> +            required:
> +              - data-lanes
> +              - bus-type
> +
> +    required:
> +      - port@1

Why port@1 but not port@0?

> +
> +  i2c-gate:
> +    $ref: /schemas/i2c/i2c-controller.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";
> +            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 {
> +                        bus-type = <MEDIA_BUS_TYPE_CSI2_DPHY>;
> +                        clock-lanes = <0>;

clock-lanes isn't listed in bindings. You can drop it from here.

> +                        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";
> +                    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 {
> +                                data-lanes = <1 2>;
> +                                lane-polarities = <1 0 1>;

Shouldn't lane-polarities be mentioned in bindings, too?

> +                                remote-endpoint = <&sensor_out>;
> +                            };
> +                        };
> +
> +                        port@1 {
> +                            reg = <1>;
> +                            max96917f_gmsl_out: endpoint {
> +                                remote-endpoint = <&max96714_gmsl_in>;
> +                            };
> +                        };
> +                    };
> +                };
> +            };
> +        };
> +    };
> +...

-- 
Regards,

Sakari Ailus