linux-kernel - Re: [PATCH v3 7/8] ASoC: cs42l42: Don't set idle_bias

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Message-ID: <f0c8d03d-8190-383b-0536-a4006b1296c7@linux.intel.com>
Date:   Mon, 30 Jan 2023 10:40:35 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Stefan Binding <sbinding@...nsource.cirrus.com>,
        Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com,
        Richard Fitzgerald <rf@...nsource.cirrus.com>
Subject: Re: [PATCH v3 7/8] ASoC: cs42l42: Don't set idle_bias_on



On 1/27/23 10:51, Stefan Binding wrote:
> From: Richard Fitzgerald <rf@...nsource.cirrus.com>
> 
> idle_bias_on was set because cs42l42 has a "VMID" type pseudo-midrail
> supply (named FILT+), and these typically take a long time to charge.
> But the driver never enabled pm_runtime so it would never have powered-
> down the cs42l42 anyway.
> 
> In fact, FILT+ can charge to operating voltage within 12.5 milliseconds
> of enabling HP or ADC. This time is already covered by the startup
> delay of the HP/ADC.
> 
> The datasheet warning about FILT+ taking up to 1 second to charge only
> applies in the special cases that either the PLL is started or
> DETECT_MODE set to non-zero while both HP and ADC are off. The driver
> never does either of these.
> 
> Removing idle_bias_on allows the Soundwire host controller to suspend
> if there isn't a snd_soc_jack handler registered.
> 
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> Signed-off-by: Stefan Binding <sbinding@...nsource.cirrus.com>

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>

> ---
>  sound/soc/codecs/cs42l42.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/sound/soc/codecs/cs42l42.c b/sound/soc/codecs/cs42l42.c
> index aa8d724432ab8..e3edaa1a2761e 100644
> --- a/sound/soc/codecs/cs42l42.c
> +++ b/sound/soc/codecs/cs42l42.c
> @@ -597,7 +597,6 @@ const struct snd_soc_component_driver cs42l42_soc_component = {
>  	.num_dapm_routes	= ARRAY_SIZE(cs42l42_audio_map),
>  	.controls		= cs42l42_snd_controls,
>  	.num_controls		= ARRAY_SIZE(cs42l42_snd_controls),
> -	.idle_bias_on		= 1,
>  	.endianness		= 1,
>  };
>  EXPORT_SYMBOL_NS_GPL(cs42l42_soc_component, SND_SOC_CS42L42_CORE);