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

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Message-ID: <VI1PR04MB42221B1708BA02B1FA2149D9E3A89@VI1PR04MB4222.eurprd04.prod.outlook.com>
Date:   Fri, 24 Feb 2023 10:54:35 +0000
From:   Chancel Liu <chancel.liu@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "perex@...ex.cz" <perex@...ex.cz>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "ckeepax@...nsource.cirrus.com" <ckeepax@...nsource.cirrus.com>,
        "patches@...nsource.cirrus.com" <patches@...nsource.cirrus.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: 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
> >
> >
> > 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
> 

Yes, you are absolutely right. From the power up to audio out timing table in
WTN0302, the minimum number is 82 and the maximum is 1003.

Consider the following possibilities:
1. These timings may depend on the system design
2. These timings may be simulated results
3. These timings may be the minimum values

I set a larger value trying to extend the time. The larger value of course
introduces unwanted time delay but it benefits on avoiding beginning audio
lost.

I also did some tests on a board. If I want to work on 48KHZ sample rate and
512FS, the recommended value is 143. But the test result showed 143ms is not
enough. I increased the value to 500ms and could hear the beginning sound.

Maybe it's a better choice to let DT set the suitable value? Is there a similar
situation before?

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

Sorry. I must avoid these spelling mistakes.

> > +      audio out time. For more details about the timing constraints of this
> > +      device, please refer to WTN0302 on
> > +
> 
> 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

Yes. This property is designed for power up to audio out timing. I need to
clearly point this out.

Thank you very much for your suggestions!

Regards, 
Chancel Liu