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: <c4ee1a7b-a500-5fa5-6a97-93b1eba2c852@linaro.org>
Date:   Fri, 24 Feb 2023 12:00:55 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Chancel Liu <chancel.liu@....com>,
        "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: [PATCH 2/4] ASoC: dt-bindings: wlf,wm8524: Add a property to
 specify power up sequency time

On 24/02/2023 11:54, Chancel Liu wrote:
>> 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 you miss proper regulator ramp-up?

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

That's not really good argument. DT should describe hardware and if this
property does not match hardware, it means you mix this with something
else. Something not for DT.


Best regards,
Krzysztof