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

[Johan Hovold <johan@kernel.org>]

On Thu, Mar 27, 2025 at 10:06:32AM +0000, Srinivas Kandagatla wrote:
> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.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@linaro.org>
> Tested-by: Christopher Obbard <christopher.obbard@linaro.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);

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)

You need to suppress that error in mux_get() to allow for optional muxes
to be looked up like this.

> +	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