Simple amp with GPIO mute/shutdown.

simple-amp.c

/*
 * ALSA SoC simple amplifier driver
 *
 * Copyright 2018 <nicveronese@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/gpio/consumer.h>
#include <linux/regulator/consumer.h>

#include <sound/soc.h>
#include <sound/soc-dapm.h>

/* This struct is used to save the context */
struct simple_amp_data {
	struct device *dev;
	struct regmap *regmap;
	struct gpio_desc *power_gpio;
};

static void simple_amp_power_gpio(struct simple_amp_data *data, int enable)
{
    /* Shutdown GPIO */
    if (data->power_gpio)
        gpiod_set_value_cansleep(data->power_gpio, enable);
}

static int simple_amp_power_event(struct snd_soc_dapm_widget *widget,
				 struct snd_kcontrol *kctrl, int event)
{
	struct snd_soc_component *c = snd_soc_dapm_to_component(widget->dapm);
	struct simple_amp_data *data = snd_soc_component_get_drvdata(c);

	simple_amp_power_gpio(data, SND_SOC_DAPM_EVENT_ON(event));

	return 0;
}

static const struct snd_soc_dapm_widget simple_amp_dapm_widgets[] = {
	SND_SOC_DAPM_INPUT("LEFT IN"),
	SND_SOC_DAPM_INPUT("RIGHT IN"),

	SND_SOC_DAPM_OUTPUT("SPK LEFT"),
	SND_SOC_DAPM_OUTPUT("SPK RIGHT"),

	SND_SOC_DAPM_REGULATOR_SUPPLY("VCC", 20, 0),
	SND_SOC_DAPM_PGA_E("MUTE", SND_SOC_NOPM, 0, 0, NULL, 0, simple_amp_power_event, 0),	
};

static const struct snd_soc_dapm_route simple_amp_dapm_routes[] = {
	{ "SPK LEFT", NULL, "LEFT IN" },
	{ "SPK RIGHT", NULL, "RIGHT IN" },

	{ "SPK LEFT", NULL, "VCC" },
	{ "SPK RIGHT", NULL, "VCC" },

	{ "SPK LEFT", NULL, "MUTE" },
	{ "SPK RIGHT", NULL, "MUTE" },
};

static const struct snd_soc_component_driver simple_amp_component_driver = {
	.name = "simple-amp",
	.dapm_widgets = simple_amp_dapm_widgets,
	.num_dapm_widgets = ARRAY_SIZE(simple_amp_dapm_widgets),
	.dapm_routes = simple_amp_dapm_routes,
	.num_dapm_routes = ARRAY_SIZE(simple_amp_dapm_routes),
};

static int asoc_simple_amp_probe(struct platform_device *pdev)
{
	struct simple_amp_data *data;
	struct device *dev = &pdev->dev;
	int ret;

	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	data->dev = &pdev->dev;

	if(of_property_read_bool(pdev->dev.of_node,"shutdown-gpio")) {
		data->power_gpio = devm_gpiod_get_optional(&pdev->dev, "shutdown", GPIOD_OUT_LOW);

		if (IS_ERR(data->power_gpio)) {
			ret = PTR_ERR(data->power_gpio);
			dev_err(&pdev->dev,	"Failed to get shutdown gpio: %d\n", ret);
			return ret;
		}
	}

	return devm_snd_soc_register_component(dev,
			&simple_amp_component_driver, NULL, 0);
}

static const struct of_device_id asoc_simple_of_match[] = {
	{ .compatible = "simple-audio-amp", },
	{},
};
MODULE_DEVICE_TABLE(of, asoc_simple_of_match);

static struct platform_driver asoc_simple_amp = {
	.driver = {
		.name = "asoc-simple-amp",
		.of_match_table = of_match_ptr(asoc_simple_of_match),
	},
	.probe = asoc_simple_amp_probe,
};

module_platform_driver(asoc_simple_amp);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("ASoC Simple Amp");
MODULE_AUTHOR("Nicolò Veronese <nicveronese@gmail.com>");