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

[Krzysztof Kozlowski]

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?


Best regards,
Krzysztof