Re: [PATCH 2/3] ASoC: dt-bindings: sama7g5-pdmc: add microchip,startup-delay-us binding

[Krzysztof Kozlowski]

On 16/02/2023 11:41, Claudiu.Beznea@xxxxxxxxxxxxx wrote:
> On 16.02.2023 12:18, Krzysztof Kozlowski wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> On 16/02/2023 11:15, Claudiu.Beznea@xxxxxxxxxxxxx wrote:
>>> On 16.02.2023 12:04, Krzysztof Kozlowski wrote:
>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>
>>>> On 14/02/2023 17:14, Claudiu Beznea wrote:
>>>>> Add microchip,startup-delay-us binding to let PDMC users to specify
>>>>> startup delay.
>>>>>
>>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
>>>>> ---
>>>>>  .../devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml   | 6 ++++++
>>>>>  1 file changed, 6 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml b/Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml
>>>>> index c4cf1e5ab84b..9b40268537cb 100644
>>>>> --- a/Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml
>>>>> +++ b/Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml
>>>>> @@ -67,6 +67,12 @@ properties:
>>>>>      maxItems: 4
>>>>>      uniqueItems: true
>>>>>
>>>>> +  microchip,startup-delay-us:
>>>>> +    description: |
>>>>> +      Specifies the delay in microseconds that needs to be applied after
>>>>> +      enabling the PDMC microphones to avoid unwanted noise due to microphones
>>>>> +      not being ready.
>>>>
>>>> Is this some hardware delay? Or OS? If OS, why Linux specific delay is
>>>> put into DT?
>>>
>>> It's the delay used in software workaround that IP needs to filter noises.
>>
>> Then this sounds like OS? Linux related properties usually do not belong
>> to DT.
>>
>>> The IP is not fully featured to do this kind of filtering on its own thus
>>> this software workaround. This delay may depend on used microphones thus
>>> for different kind of setups (PDMC + different microphones) I introduced
>>> this in DT.
>>
>> I understand your driver needs delay and I am not questioning this. I am
>> questioning why this is suitable for DT?
> 
> Because that delay may depend on the microphones that are used with PDMC.
> Different boards may come with different microphones, thus the default
> delay may not fit to fully filter the noise. Due to this I chose to add it
> in DT.

Ah, ok, that's good explanation. Thank you.


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>

Best regards,
Krzysztof