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

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Date:   Fri, 24 Feb 2023 11:59:26 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Chancel Liu <chancel.liu@....com>, Mark Brown <broonie@...nel.org>
Cc:     "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "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 11:56, Chancel Liu wrote:
>> On Wed, Feb 22, 2023 at 07:39:43PM +0800, 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 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/
>>
>> According to that the delay is a property of MCLK and the sample rate rather
>> than a per board constant, it shouldn't be in DT but rather the driver should
>> figure out the required delay on each startup.
> 
> I can't agree with you more. From the power up to audio out timing table in
> WTN0302, the delay depends on sample rate and MCLK. Driver should calculate it
> rather than read it from DT. However as I mentioned in my last email, values in
> the table seem not accurate for all systems. It's a kind of compromise to get
> the value from DT. Do other codecs have a similar situation?

DT is for hardware properties, not for software compromises.


Best regards,
Krzysztof