linux-kernel - Re: [PATCH v5 2/8] dt-bindings: media: max9286: Document 'maxim,initial-reverse-channel-mV'

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Date:   Mon, 30 Nov 2020 15:00:48 -0700
From:   Rob Herring <robh@...nel.org>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>
Cc:     kieran.bingham+renesas@...asonboard.com,
        laurent.pinchart+renesas@...asonboard.com,
        niklas.soderlund+renesas@...natech.se, geert@...ux-m68k.org,
        devicetree@...r.kernel.org, linux-media@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hyun Kwon <hyunk@...inx.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        sergei.shtylyov@...il.com
Subject: Re: [PATCH v5 2/8] dt-bindings: media: max9286: Document
 'maxim,initial-reverse-channel-mV'

On Mon, Nov 16, 2020 at 02:52:59PM +0100, Jacopo Mondi wrote:
> Document the 'initial-reverse-channel-mV' vendor property in the
> bindings document of the max9286 driver.
> 
> The newly introduced property allows to specifying the initial
> configuration of the GMSL reverse control channel to accommodate
> remote serializers pre-programmed with the high threshold power
> supply noise immunity enabled.
> 
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> ---
>  .../bindings/media/i2c/maxim,max9286.yaml     | 23 +++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
> index 9ea827092fdd..f61234d204fa 100644
> --- a/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
> +++ b/Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
> @@ -51,6 +51,26 @@ properties:
>    '#gpio-cells':
>      const: 2
> 
> +  maxim,initial-reverse-channel-mV:

Use standard unit suffix.

> +    $ref: '/schemas/types.yaml#/definitions/uint32'
> +    minimum: 30
> +    maximum: 200
> +    default: 170
> +    description: |
> +      Initial amplitude of the reverse control channel, in millivolts.
> +
> +      The initial amplitude shall be adjusted to a value compatible with the
> +      configuration of the connected remote serializer.
> +
> +      Some camera modules (for example RDACM20) include an on-board MCU that
> +      pre-programs the embedded serializer with power supply noise immunity
> +      (high-threshold) enabled. A typical value of the deserializer's reverse
> +      channel amplitude to communicate with pre-programmed serializers is 170mV.
> +
> +      A typical value for the reverse channel amplitude to communicate with
> +      a remote serializer whose high-threshold noise immunity is not enabled
> +      is 100mV.
> +
>    ports:
>      type: object
>      description: |
> @@ -221,6 +241,7 @@ required:
>    - ports
>    - i2c-mux
>    - gpio-controller
> +  - maxim,initial-reverse-channel-mV
> 
>  additionalProperties: false
> 
> @@ -243,6 +264,8 @@ examples:
>          gpio-controller;
>          #gpio-cells = <2>;
> 
> +        maxim,initial-reverse-channel-mV = <170>;
> +
>          ports {
>            #address-cells = <1>;
>            #size-cells = <0>;
> --
> 2.29.1
>