linux-kernel - Re: [PATCH 2/4] ASoC: dt-bindings: wlf,wm8524: Add a property to specify power up sequency time

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Message-ID: <506f92cd-7cf5-4fd5-a930-9af086732f84@linaro.org>
Date:   Wed, 22 Feb 2023 13:42:16 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Chancel Liu <chancel.liu@....com>, lgirdwood@...il.com,
        broonie@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, perex@...ex.cz, tiwai@...e.com,
        ckeepax@...nsource.cirrus.com, patches@...nsource.cirrus.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/4] ASoC: dt-bindings: wlf,wm8524: Add a property to
 specify power up sequency time

On 22/02/2023 12:39, Chancel Liu wrote:
> This property specifies power up to audio out time. It's necessary
> beacause this device has to wait some time before ready to output audio

typo... run spellcheck, also on the subject

> after MCLK, BCLK and MUTE=1 are enabled. For more details about the
> timing constraints, please refer to WTN0302 on
> https://www.cirrus.com/products/wm8524/
> 
> Signed-off-by: Chancel Liu <chancel.liu@....com>
> ---
>  .../devicetree/bindings/sound/wlf,wm8524.yaml          | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/sound/wlf,wm8524.yaml b/Documentation/devicetree/bindings/sound/wlf,wm8524.yaml
> index 09c54cc7de95..54b4da5470e4 100644
> --- a/Documentation/devicetree/bindings/sound/wlf,wm8524.yaml
> +++ b/Documentation/devicetree/bindings/sound/wlf,wm8524.yaml
> @@ -21,6 +21,15 @@ properties:
>      description:
>        a GPIO spec for the MUTE pin.
>  
> +  wlf,power-up-delay-ms:
> +    maximum: 1500

maximum is 1003. Where do you see 1500?

minimum: 82

> +    default: 100
> +    description:
> +      Power up sequency delay time in millisecond. It specifies power up to

typo: sequence?

> +      audio out time. For more details about the timing constraints of this
> +      device, please refer to WTN0302 on
> +      https://www.cirrus.com/products/wm8524/.

According to WTN0302 this might or might not include regulator
ramp-up-delay. You should clearly indicate which part of it this delay
is to not mix up with ramp up. IOW, mention exactly from where the value
comes (e.g. Δt POWER UP TO AUDIO OUT TIMING table, depending on sampling
clock rate). Otherwise you introduce quite loose property which will be
including regulator ramp up in some cases...

Best regards,
Krzysztof