linux-kernel - Re: [PATCH v2] media: dt-bindings: ov8856: decouple lanes and link frequency from driver

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Date:   Fri, 8 Dec 2023 18:07:09 +0000
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Maxime Ripard <mripard@...nel.org>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] media: dt-bindings: ov8856: decouple lanes and link
 frequency from driver

Hi Krzysztof,

Thanks for the update.

On Thu, Dec 07, 2023 at 03:23:56PM +0100, Krzysztof Kozlowski wrote:
> The data lanes and link frequency were set to match exiting Linux driver
> limitations, however bindings should be independent of chosen Linux
> driver support.
> 
> Decouple these properties from the driver to match what is actually
> supported by the hardware.
> 
> This also fixes DTS example:
> 
>   ov8856.example.dtb: camera@10: port:endpoint:link-frequencies:0: [360000000] is too short
> 
> Fixes: 066a94e28a23 ("media: dt-bindings: media: Use graph and video-interfaces schemas")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> 
> ---
> 
> Changes in v2:
> 1. Rework approach: decouple bindings from driver instead of fixing
>    DTS example (Sakari)
> ---
>  .../devicetree/bindings/media/i2c/ov8856.yaml | 21 +++++++++++--------
>  1 file changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/ov8856.yaml b/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> index 57f5e48fd8e0..71102a71cf81 100644
> --- a/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> +++ b/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> @@ -67,19 +67,22 @@ properties:
>  
>          properties:
>            data-lanes:
> -            description: |-
> -              The driver only supports four-lane operation.
> -            items:
> -              - const: 1
> -              - const: 2
> -              - const: 3
> -              - const: 4
> +            oneOf:
> +              - items:
> +                  - const: 1
> +              - items:
> +                  - const: 1
> +                  - const: 2
> +              - items:
> +                  - const: 1
> +                  - const: 2
> +                  - const: 3
> +                  - const: 4
>  
>            link-frequencies:
>              description: Frequencies listed are driver, not h/w limitations.

This should be dropped, too.

> -            maxItems: 2
>              items:
> -              enum: [ 360000000, 180000000 ]
> +              enum: [ 1440000000, 720000000, 360000000, 180000000 ]

These frequencies are listed in the datasheet but they're just an
example---the sensor hardware isn't limited to these, the resulting
frequency on the CSI-2 bus is simply up to the external clock frequency and
PLL configuration. I'd remove the values here altogether.

>  
>          required:
>            - link-frequencies

-- 
Regards,

Sakari Ailus