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

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Message-ID: <ce8a7040-2667-4046-8542-f698bd8a9af1@linaro.org>
Date:   Fri, 8 Dec 2023 20:37:10 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
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

On 08/12/2023 19:07, Sakari Ailus wrote:
> 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.

Ack, I forgot.

> 
>> -            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.

Hm, are you sure? Isn't it quite difficult to program device to any
frequency? But if that's not the case here, I can drop it.


Best regards,
Krzysztof