linux/drivers/input/misc/pwm-beeper.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (C) 2010, Lars-Peter Clausen <lars@metafoo.de>
 *  PWM beeper driver
 */

#include <linux/input.h>
#include <linux/regulator/consumer.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/workqueue.h>

struct pwm_beeper {
	struct input_dev *input;
	struct pwm_device *pwm;
	struct regulator *amplifier;
	struct work_struct work;
	unsigned long period;
	unsigned int bell_frequency;
	bool suspended;
	bool amplifier_on;
};

#define HZ_TO_NANOSECONDS(x) (1000000000UL/(x))

static int pwm_beeper_on(struct pwm_beeper *beeper, unsigned long period)
{
	struct pwm_state state;
	int error;

	pwm_get_state(beeper->pwm, &state);

	state.enabled = true;
	state.period = period;
	pwm_set_relative_duty_cycle(&state, 50, 100);

	error = pwm_apply_might_sleep(beeper->pwm, &state);
	if (error)
		return error;

	if (!beeper->amplifier_on) {
		error = regulator_enable(beeper->amplifier);
		if (error) {
			pwm_disable(beeper->pwm);
			return error;
		}

		beeper->amplifier_on = true;
	}

	return 0;
}

static void pwm_beeper_off(struct pwm_beeper *beeper)
{
	if (beeper->amplifier_on) {
		regulator_disable(beeper->amplifier);
		beeper->amplifier_on = false;
	}

	pwm_disable(beeper->pwm);
}

static void pwm_beeper_work(struct work_struct *work)
{
	struct pwm_beeper *beeper = container_of(work, struct pwm_beeper, work);
	unsigned long period = READ_ONCE(beeper->period);

	if (period)
		pwm_beeper_on(beeper, period);
	else
		pwm_beeper_off(beeper);
}

static int pwm_beeper_event(struct input_dev *input,
			    unsigned int type, unsigned int code, int value)
{
	struct pwm_beeper *beeper = input_get_drvdata(input);

	if (type != EV_SND || value < 0)
		return -EINVAL;

	switch (code) {
	case SND_BELL:
		value = value ? beeper->bell_frequency : 0;
		break;
	case SND_TONE:
		break;
	default:
		return -EINVAL;
	}

	if (value == 0)
		beeper->period = 0;
	else
		beeper->period = HZ_TO_NANOSECONDS(value);

	if (!beeper->suspended)
		schedule_work(&beeper->work);

	return 0;
}

static void pwm_beeper_stop(struct pwm_beeper *beeper)
{
	cancel_work_sync(&beeper->work);
	pwm_beeper_off(beeper);
}

static void pwm_beeper_close(struct input_dev *input)
{
	struct pwm_beeper *beeper = input_get_drvdata(input);

	pwm_beeper_stop(beeper);
}

static int pwm_beeper_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct pwm_beeper *beeper;
	struct pwm_state state;
	u32 bell_frequency;
	int error;

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

	beeper->pwm = devm_pwm_get(dev, NULL);
	if (IS_ERR(beeper->pwm))
		return dev_err_probe(dev, PTR_ERR(beeper->pwm), "Failed to request PWM device\n");

	/* Sync up PWM state and ensure it is off. */
	pwm_init_state(beeper->pwm, &state);
	state.enabled = false;
	error = pwm_apply_might_sleep(beeper->pwm, &state);
	if (error) {
		dev_err(dev, "failed to apply initial PWM state: %d\n",
			error);
		return error;
	}

	beeper->amplifier = devm_regulator_get(dev, "amp");
	if (IS_ERR(beeper->amplifier))
		return dev_err_probe(dev, PTR_ERR(beeper->amplifier),
				     "Failed to get 'amp' regulator\n");

	INIT_WORK(&beeper->work, pwm_beeper_work);

	error = device_property_read_u32(dev, "beeper-hz", &bell_frequency);
	if (error) {
		bell_frequency = 1000;
		dev_dbg(dev,
			"failed to parse 'beeper-hz' property, using default: %uHz\n",
			bell_frequency);
	}

	beeper->bell_frequency = bell_frequency;

	beeper->input = devm_input_allocate_device(dev);
	if (!beeper->input) {
		dev_err(dev, "Failed to allocate input device\n");
		return -ENOMEM;
	}

	beeper->input->name = "pwm-beeper";
	beeper->input->phys = "pwm/input0";
	beeper->input->id.bustype = BUS_HOST;
	beeper->input->id.vendor = 0x001f;
	beeper->input->id.product = 0x0001;
	beeper->input->id.version = 0x0100;

	input_set_capability(beeper->input, EV_SND, SND_TONE);
	input_set_capability(beeper->input, EV_SND, SND_BELL);

	beeper->input->event = pwm_beeper_event;
	beeper->input->close = pwm_beeper_close;

	input_set_drvdata(beeper->input, beeper);

	error = input_register_device(beeper->input);
	if (error) {
		dev_err(dev, "Failed to register input device: %d\n", error);
		return error;
	}

	platform_set_drvdata(pdev, beeper);

	return 0;
}

static int pwm_beeper_suspend(struct device *dev)
{
	struct pwm_beeper *beeper = dev_get_drvdata(dev);

	/*
	 * Spinlock is taken here is not to protect write to
	 * beeper->suspended, but to ensure that pwm_beeper_event
	 * does not re-submit work once flag is set.
	 */
	scoped_guard(spinlock_irq, &beeper->input->event_lock) {
		beeper->suspended = true;
	}

	pwm_beeper_stop(beeper);

	return 0;
}

static int pwm_beeper_resume(struct device *dev)
{
	struct pwm_beeper *beeper = dev_get_drvdata(dev);

	scoped_guard(spinlock_irq, &beeper->input->event_lock) {
		beeper->suspended = false;
	}

	/* Let worker figure out if we should resume beeping */
	schedule_work(&beeper->work);

	return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(pwm_beeper_pm_ops,
				pwm_beeper_suspend, pwm_beeper_resume);

#ifdef CONFIG_OF
static const struct of_device_id pwm_beeper_match[] = {
	{ .compatible = "pwm-beeper", },
	{ },
};
MODULE_DEVICE_TABLE(of, pwm_beeper_match);
#endif

static struct platform_driver pwm_beeper_driver = {
	.probe	= pwm_beeper_probe,
	.driver = {
		.name	= "pwm-beeper",
		.pm	= pm_sleep_ptr(&pwm_beeper_pm_ops),
		.of_match_table = of_match_ptr(pwm_beeper_match),
	},
};
module_platform_driver(pwm_beeper_driver);

MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
MODULE_DESCRIPTION("PWM beeper driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pwm-beeper");