linux-kernel - Re: [PATCH] ASoC: nau8825: fix issue that pop noise when start capture

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Message-ID: <5A3376E7.2080602@nuvoton.com>
Date:   Fri, 15 Dec 2017 15:16:55 +0800
From:   John Hsu <KCHSU0@...oton.com>
To:     <abhijeet.kumar@...el.com>
CC:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        "Bhumika Goyal" <bhumirks@...il.com>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
        <anatol.pomozov@...il.com>, <mhkuo@...oton.com>,
        <wuchengli@...gle.com>, <cychiang@...gle.com>,
        <mac.chiang@...el.com>, <YHCHuang@...oton.com>,
        <CTLIN0@...oton.com>, <WTLI@...oton.com>
Subject: Re: [PATCH] ASoC: nau8825: fix issue that pop noise when start capture

On 12/12/2017 3:10 AM, abhijeet.kumar@...el.com wrote:
> From: Abhijeet Kumar <abhijeet.kumar@...el.com>
>
> 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.
>
> Signed-off-by: Abhijeet Kumar <abhijeet.kumar@...el.com>
> ---
>  sound/soc/codecs/nau8825.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/sound/soc/codecs/nau8825.c b/sound/soc/codecs/nau8825.c
> index 714ce17da717..e853a6dfd33b 100644
> --- a/sound/soc/codecs/nau8825.c
> +++ b/sound/soc/codecs/nau8825.c
> @@ -905,6 +905,7 @@ static int nau8825_adc_event(struct snd_soc_dapm_widget *w,
>
>       switch (event) {
>       case SND_SOC_DAPM_POST_PMU:
> +             msleep(125);
>               regmap_update_bits(nau8825->regmap, NAU8825_REG_ENA_CTRL,
>                       NAU8825_ENABLE_ADC, NAU8825_ENABLE_ADC);
>               break;

The solution is fine for me. It's verified in my device and indeed
helps to reduce the capture pop noise. I think the little delay
is acceptable.

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