linux-kernel - Re: [PATCH AUTOSEL for 4.14 029/110] ASoC: nau8825: fix issue that pop noise when start capture

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Date:   Tue, 6 Feb 2018 01:41:29 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     Mark Brown <broonie@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Abhijeet Kumar <abhijeet.kumar@...el.com>
Subject: Re: [PATCH AUTOSEL for 4.14 029/110] ASoC: nau8825: fix issue that
 pop noise when start capture

On Mon, Feb 05, 2018 at 11:41:54AM +0000, Mark Brown wrote:
>On Sat, Feb 03, 2018 at 06:00:42PM +0000, Sasha Levin wrote:
>> From: Abhijeet Kumar <abhijeet.kumar@...el.com>
>>
>> [ Upstream commit d070f7c703ef26e3db613f24206823f916272fc6 ]
>>
>> In skylake platform, we hear a loud pop noise(0 dB) at start of
>> audio capture power up sequence. This patch removes the pop noise
>> from the recording by adding a delay before enabling ADC.
>
>>  	switch (event) {
>>  	case SND_SOC_DAPM_POST_PMU:
>> +		msleep(125);
>>  		regmap_update_bits(nau8825->regmap, NAU8825_REG_ENA_CTRL,
>
>This is another one of these where I'm not convinced that backporting to
>stable isn't going to introduce regressions - it will fix problems on
>some systems but if someone really cares about a startup pop and has
>arranged to do something like discard the start of the audio where the
>pop occurs then this may cut off even more and cause them to miss
>things.

It might cause regressions for users who worked around the issue, but it
may also fix the issue for users who didn't. I think that in general
we'd rather have mainline and stable trees have the same bugs and
breakage - we don't want surprises when users jump around between
kernels.

-- 

Thanks,
Sasha