linux-kernel - Re: [PATCH v3 5/6] ASoC: codecs: wcd938x: add mux control support for hp audio mux

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Message-ID: <7fc622e8-6f9d-4a14-bf5f-3122e6f81808@oss.qualcomm.com>
Date: Mon, 24 Mar 2025 13:20:44 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: srinivas.kandagatla@...aro.org, peda@...ntia.se, broonie@...nel.org,
        andersson@...nel.org, krzk+dt@...nel.org
Cc: ivprusov@...utedevices.com, luca.ceresoli@...tlin.com,
        zhoubinbin@...ngson.cn, paulha@...nsource.cirrus.com,
        lgirdwood@...il.com, robh@...nel.org, conor+dt@...nel.org,
        konradybcio@...nel.org, perex@...ex.cz, tiwai@...e.com,
        linux-sound@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        johan+linaro@...nel.org,
        Christopher Obbard <christopher.obbard@...aro.org>
Subject: Re: [PATCH v3 5/6] ASoC: codecs: wcd938x: add mux control support for
 hp audio mux

On 24/03/2025 13:06, srinivas.kandagatla@...aro.org wrote:
> From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> 
> On some platforms to minimise pop and click during switching between
> CTIA and OMTP headset an additional HiFi mux is used. Most common
> case is that this switch is switched on by default, but on some
> platforms this needs a regulator enable.
> 
> move to using mux control to enable both regulator and handle gpios,
> deprecate the usage of gpio.
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> Tested-by: Christopher Obbard <christopher.obbard@...aro.org>
> ---
>   sound/soc/codecs/Kconfig   |  1 +
>   sound/soc/codecs/wcd938x.c | 38 ++++++++++++++++++++++++++++++--------
>   2 files changed, 31 insertions(+), 8 deletions(-)
> 
> diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
> index ee35f3aa5521..a2829d76e108 100644
> --- a/sound/soc/codecs/Kconfig
> +++ b/sound/soc/codecs/Kconfig
> @@ -2226,6 +2226,7 @@ config SND_SOC_WCD938X
>   	tristate
>   	depends on SOUNDWIRE || !SOUNDWIRE
>   	select SND_SOC_WCD_CLASSH
> +	select MULTIPLEXER
>   
>   config SND_SOC_WCD938X_SDW
>   	tristate "WCD9380/WCD9385 Codec - SDW"
> diff --git a/sound/soc/codecs/wcd938x.c b/sound/soc/codecs/wcd938x.c
> index dfaa3de31164..948b5f6cc45a 100644
> --- a/sound/soc/codecs/wcd938x.c
> +++ b/sound/soc/codecs/wcd938x.c
> @@ -19,6 +19,7 @@
>   #include <linux/regmap.h>
>   #include <sound/soc.h>
>   #include <sound/soc-dapm.h>
> +#include <linux/mux/consumer.h>
>   #include <linux/regulator/consumer.h>
>   
>   #include "wcd-clsh-v2.h"
> @@ -178,6 +179,8 @@ struct wcd938x_priv {
>   	int variant;
>   	int reset_gpio;
>   	struct gpio_desc *us_euro_gpio;
> +	struct mux_control *us_euro_mux;
> +	u32 mux_state;
>   	u32 micb1_mv;
>   	u32 micb2_mv;
>   	u32 micb3_mv;
> @@ -3243,9 +3246,16 @@ static bool wcd938x_swap_gnd_mic(struct snd_soc_component *component)
>   
>   	wcd938x = snd_soc_component_get_drvdata(component);
>   
> -	value = gpiod_get_value(wcd938x->us_euro_gpio);
> +	if (!wcd938x->us_euro_mux) {
> +		value = gpiod_get_value(wcd938x->us_euro_gpio);
>   
> -	gpiod_set_value(wcd938x->us_euro_gpio, !value);
> +		gpiod_set_value(wcd938x->us_euro_gpio, !value);

Is it possible to use mux_state for both GPIO and MUX paths?

> +	} else {
> +		mux_control_deselect(wcd938x->us_euro_mux);
> +		wcd938x->mux_state = !wcd938x->mux_state;
> +		if (mux_control_select(wcd938x->us_euro_mux, wcd938x->mux_state))
> +			dev_err(component->dev, "Unable to select us/euro mux state\n");

This can lead to mux being deselected next time even if the 
mux_control_select returned an error. I think mux_control API needs a 
way to toggle the state without deselecting it first. Anyway, an error 
from mux_control_select() must prevent you from calling 
mux_control_deselect() next time.

> +	}
>   
>   	return true;
>   }


-- 
With best wishes
Dmitry