linux-kernel - Re: [PATCH] ASoC: AMD: Add delay before starting to capture

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Date:   Mon, 7 Jan 2019 06:00:35 +0000
From:   "Agrawal, Akshu" <Akshu.Agrawal@....com>
To:     Mark Brown <broonie@...nel.org>
CC:     "djkurtz@...omium.org" <djkurtz@...omium.org>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        "Mukunda, Vijendar" <Vijendar.Mukunda@....com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        "moderated list:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM..." 
        <alsa-devel@...a-project.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: AMD: Add delay before starting to capture



On 1/4/2019 5:57 PM, Mark Brown wrote:
> On Thu, Jan 03, 2019 at 10:18:13AM +0000, Agrawal, Akshu wrote:
>> On capture through dmic we observe a glitch at the start of record.
>> This is because we start capturing even before dmic is ready to send
>> out data. The glitch seen last for ~20msec.
>>
> 
>> +	/*
>> +	 * On some platforms, it takes ~20 msec for PDM DMICs and ADAU7002
>> +	 * to settle and start producing proper audio data.
>> +	 */
>> +	msleep(ADAU7002_DELAY_MS);
> 
> If the delay is required for external components to start up the delay
> should be going in the drivers for those components rather than in the
> driver for the CPU side, that way other systems using those components
> get the benefit and non-affected boards don't pay the cost.  There's
> already some support for this in the DMIC driver at least.
> 

Agreed, we can use the similar to wakeup_delay in dmic driver in our
codec driver. Will post the patch on same lines.

Thanks,
Akshu