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

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Date:   Thu, 16 Feb 2023 11:04:33 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>, lgirdwood@...il.com,
        broonie@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, lars@...afoo.de, perex@...ex.cz,
        tiwai@...e.com, nicolas.ferre@...rochip.com,
        alexandre.belloni@...tlin.com
Cc:     alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/3] ASoC: dt-bindings: sama7g5-pdmc: add
 microchip,startup-delay-us binding

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@...rochip.com>
> ---
>  .../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?

Best regards,
Krzysztof