linux-kernel - Re: [PATCH v6 5/6] ASoC: codecs: wcd938x: add mux control support for hp audio mux

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Message-ID: <8613cf45-d202-4577-868c-8caf771c7bc4@linaro.org>
Date: Thu, 3 Apr 2025 13:19:57 +0100
From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: peda@...ntia.se, broonie@...nel.org, andersson@...nel.org,
 krzk+dt@...nel.org, 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, dmitry.baryshkov@....qualcomm.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 v6 5/6] ASoC: codecs: wcd938x: add mux control support for
 hp audio mux



On 02/04/2025 10:12, Johan Hovold wrote:
> On Thu, Mar 27, 2025 at 10:06:32AM +0000, Srinivas Kandagatla 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>
> 
>> @@ -3261,11 +3276,26 @@ static int wcd938x_populate_dt_data(struct wcd938x_priv *wcd938x, struct device
>>   		return dev_err_probe(dev, wcd938x->reset_gpio,
>>   				     "Failed to get reset gpio\n");
>>   
>> -	wcd938x->us_euro_gpio = devm_gpiod_get_optional(dev, "us-euro",
>> -						GPIOD_OUT_LOW);
>> -	if (IS_ERR(wcd938x->us_euro_gpio))
>> -		return dev_err_probe(dev, PTR_ERR(wcd938x->us_euro_gpio),
>> -				     "us-euro swap Control GPIO not found\n");
>> +	wcd938x->us_euro_mux = devm_mux_control_get(dev, NULL);
> 
Thanks Johan,
> Running with this patch on the CRD I noticed that this now prints an
> error as there is no optional mux (or gpio) defined:
> 
> 	wcd938x_codec audio-codec: /audio-codec: failed to get mux-control (0)

This is not from codec driver, mux control is throwing up this.

> 
> You need to suppress that error in mux_get() to allow for optional muxes
> to be looked up like this.
I have a plan for this,

I proposed some changes to mux api for exclusive apis at 
https://lkml.org/lkml/2025/3/26/955

This should also allow us to easily add an optional api, which I plan to 
do once i get some feedback on this patch.

--srini

> 
>> +	if (IS_ERR(wcd938x->us_euro_mux)) {
>> +		if (PTR_ERR(wcd938x->us_euro_mux) == -EPROBE_DEFER)
>> +			return -EPROBE_DEFER;
>> +
>> +		/* mux is optional and now fallback to using gpio */
>> +		wcd938x->us_euro_mux = NULL;
>> +		wcd938x->us_euro_gpio = devm_gpiod_get_optional(dev, "us-euro", GPIOD_OUT_LOW);
>> +		if (IS_ERR(wcd938x->us_euro_gpio))
>> +			return dev_err_probe(dev, PTR_ERR(wcd938x->us_euro_gpio),
>> +					     "us-euro swap Control GPIO not found\n");
>> +	} else {
>> +		ret = mux_control_try_select(wcd938x->us_euro_mux, wcd938x->mux_state);
>> +		if (ret) {
>> +			dev_err(dev, "Error (%d) Unable to select us/euro mux state\n", ret);
>> +			wcd938x->mux_setup_done = false;
>> +			return ret;
>> +		}
>> +		wcd938x->mux_setup_done = true;
>> +	}
> 
> Johan