Re: [PATCH v3 2/3] media: dt-bindings: alvium: add document YAML binding

[Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>]

Hi Tommaso,

Thank you for the patch.

On Tue, Jun 06, 2023 at 05:54:03PM +0200, Tommaso Merciai wrote:
> Add documentation of device tree in YAML schema for the ALVIUM
> Camera from Allied Vision Inc.
> 
> References:
>  - https://www.alliedvision.com/en/products/embedded-vision-solutions
> 
> Signed-off-by: Tommaso Merciai <tomm.merciai@xxxxxxxxx>
> ---
> Changes since v1:
>  - Fixed build error as suggested by RHerring bot
> 
> Changes since v2:
>  - Fixed License as suggested by KKozlowski/CDooley
>  - Removed rotation property as suggested by CDooley/LPinchart
>  - Fixed example node name as suggested by CDooley
>  - Fixed title as suggested by LPinchart
>  - Fixed compatible name as suggested by LPinchart
>  - Removed clock as suggested by LPinchart
>  - Removed gpios not as suggested by LPinchart
>  - Renamed property name streamon-delay into alliedvision,lp2hs-delay-us
>  - Fixed vendor prefix, unit append as suggested by KKozlowski
>  - Fixed data-lanes
>  - Fixed blank space + example indentation (from 6 -> 4 space) as suggested by KKozlowski
>  - Dropped status into example  as suggested by KKozlowski
>  - Added vcc-ext-in supply as suggested by LPinchart
>  - Dropped pinctrl into example as suggested by LPinchart
> 
>  .../media/i2c/alliedvision,alvium-csi2.yaml   | 93 +++++++++++++++++++
>  1 file changed, 93 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/i2c/alliedvision,alvium-csi2.yaml
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/alliedvision,alvium-csi2.yaml b/Documentation/devicetree/bindings/media/i2c/alliedvision,alvium-csi2.yaml
> new file mode 100644
> index 000000000000..191534e2f7bd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/i2c/alliedvision,alvium-csi2.yaml
> @@ -0,0 +1,93 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/media/i2c/alliedvision,alvium.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Allied Vision Alvium Camera
> +
> +maintainers:
> +  - Tommaso Merciai <tomm.merciai@xxxxxxxxx>
> +  - Martin Hecht <martin.hecht@xxxxxxxx>
> +
> +allOf:
> +  - $ref: /schemas/media/video-interface-devices.yaml#
> +
> +properties:
> +  compatible:
> +    const: alliedvision,alvium-csi2
> +
> +  reg:
> +    maxItems: 1
> +
> +  vcc-ext-in-supply:
> +    description:
> +      Definition of the regulator used as interface power supply.

      The regulator that supplies power to the VCC_EXT_IN pins.

> +
> +  alliedvision,lp2hs-delay-us:
> +    maxItems: 1
> +    description:
> +      Low power to high speed delay time in microseconds.

You can drop "in microseconds", that's implied by the suffix.

> +      The purpose of this property is force a DPhy reset for the period
> +      described by the microseconds on the property, before it starts
> +      streaming. To be clear, with that value bigger than 0 the Alvium
> +      forces a dphy-reset on all lanes for that period. That means all
> +      lanes go up into low power state. This may help a csi2 rx ip to
> +      reset if that IP can't deal with a continous clock.

I'd like to propose what I think is a clearer version:

    description: |
      Low power to high speed delay time.

      If the value is larger than 0, the camera forces a reset of all
      D-PHY lanes for the duration specified by this property. All lanes
      will transition to the low-power state and back to the high-speed
      state after the delay. Otherwise the lanes will transition to and
      remain in the high-speed state immediately after power on.

      This is meant to help CSI-2 receivers synchronizing their D-PHY
      RX.

Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>

> +
> +  port:
> +    description: Digital Output Port
> +    $ref: /schemas/graph.yaml#/$defs/port-base
> +    additionalProperties: false
> +
> +    properties:
> +      endpoint:
> +        $ref: /schemas/media/video-interfaces.yaml#
> +        unevaluatedProperties: false
> +
> +        properties:
> +          link-frequencies: true
> +
> +          data-lanes:
> +            minItems: 1
> +            items:
> +              - const: 1
> +              - const: 2
> +              - const: 3
> +              - const: 4
> +
> +        required:
> +          - data-lanes
> +          - link-frequencies
> +
> +required:
> +  - compatible
> +  - reg
> +  - vcc-ext-in-supply
> +  - port
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        alvium: camera@3c {
> +            compatible = "alliedvision,alvium-csi2";
> +            reg = <0x3c>;
> +            vcc-ext-in-supply = <&reg_vcc_ext_in>;
> +            alliedvision,lp2hs-delay-us = <20>;
> +
> +            port {
> +                alvium_out: endpoint {
> +                    remote-endpoint = <&mipi_csi_0_in>;
> +                    data-lanes = <1 2 3 4>;
> +                    link-frequencies = /bits/ 64 <681250000>;
> +                };
> +            };
> +        };
> +    };
> +
> +...

-- 
Regards,

Laurent Pinchart