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

[Claudiu.Beznea]

On 16.02.2023 12:04, Krzysztof Kozlowski wrote:
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> 
> 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.
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.

> 
> Best regards,
> Krzysztof
>