drivers/pwm/gpio-pwm.c - kernel/windcharger - Git at Google

 /*
  * drivers/pwm/gpio.c
  *
  * Models a single-channel PWM device using a timer and a GPIO pin.
  *
  * Copyright (C) 2010 Bill Gatliff <bgat@billgatliff.com>
  *
  * This program is free software; you may redistribute 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.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  * USA
  */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/hrtimer.h>
 #include <linux/err.h>
 #include <linux/platform_device.h>
 #include <linux/workqueue.h>
 #include <linux/gpio.h>
 #include <linux/slab.h>
 #include <linux/pwm/pwm.h>

 struct gpio_pwm {
 	struct pwm_device pwm;
 	struct hrtimer timer;
 	struct work_struct work;
 	pwm_callback_t callback;
 	int gpio;
 	unsigned long polarity : 1;
 	unsigned long active : 1;
 };

 static inline struct gpio_pwm *to_gpio_pwm(const struct pwm_channel *p)
 {
 	return container_of(p->pwm, struct gpio_pwm, pwm);
 }

 static void
 gpio_pwm_work (struct work_struct *work)
 {
 	struct gpio_pwm *gp = container_of(work, struct gpio_pwm, work);

 	if (gp->active)
 		gpio_direction_output(gp->gpio, gp->polarity ? 1 : 0);
 	else
 		gpio_direction_output(gp->gpio, gp->polarity ? 0 : 1);
 }

 static enum hrtimer_restart
 gpio_pwm_timeout(struct hrtimer *t)
 {
 	struct gpio_pwm *gp = container_of(t, struct gpio_pwm, timer);
 	ktime_t tnew;

 	if (unlikely(gp->pwm.channels[0].duty_ticks == 0))
 		gp->active = 0;
 	else if (unlikely(gp->pwm.channels[0].duty_ticks
 			  == gp->pwm.channels[0].period_ticks))
 		gp->active = 1;
 	else
 		gp->active ^= 1;

 	if (gpio_cansleep(gp->gpio))
 		schedule_work(&gp->work);
 	else
 		gpio_pwm_work(&gp->work);

 	if (!gp->active && gp->pwm.channels[0].callback)
 		gp->pwm.channels[0].callback(&gp->pwm.channels[0]);

 	if (unlikely(!gp->active &&
 		     (gp->pwm.channels[0].flags & BIT(FLAG_STOP)))) {
 		clear_bit(FLAG_STOP, &gp->pwm.channels[0].flags);
 		complete_all(&gp->pwm.channels[0].complete);
 		return HRTIMER_NORESTART;
 	}

 	if (gp->active)
 		tnew = ktime_set(0, gp->pwm.channels[0].duty_ticks);
 	else
 		tnew = ktime_set(0, gp->pwm.channels[0].period_ticks
 				 - gp->pwm.channels[0].duty_ticks);
 	hrtimer_start(&gp->timer, tnew, HRTIMER_MODE_REL);

 	return HRTIMER_NORESTART;
 }

 static void gpio_pwm_start(struct pwm_channel *p)
 {
 	struct gpio_pwm *gp = to_gpio_pwm(p);

 	gp->active = 0;
 	gpio_pwm_timeout(&gp->timer);
 }

 static int
 gpio_pwm_config_nosleep(struct pwm_channel *p,
 			struct pwm_channel_config *c)
 {
 	struct gpio_pwm *gp = to_gpio_pwm(p);
 	int ret = 0;
 	unsigned long flags;

 	spin_lock_irqsave(&p->lock, flags);

 	switch (c->config_mask) {

 	case PWM_CONFIG_DUTY_TICKS:
 		p->duty_ticks = c->duty_ticks;
 		break;

 	case PWM_CONFIG_START:
 		if (!hrtimer_active(&gp->timer)) {
 			gpio_pwm_start(p);
 		}
 		break;
 	default:
 		ret = -EINVAL;
 		break;
 	}

 	spin_unlock_irqrestore(&p->lock, flags);
 	return ret;
 }

 static int
 gpio_pwm_stop_sync(struct pwm_channel *p)
 {
 	struct gpio_pwm *gp = to_gpio_pwm(p);
 	int ret;
 	int was_on = hrtimer_active(&gp->timer);

 	if (was_on) {
 		do {
 			init_completion(&p->complete);
 			set_bit(FLAG_STOP, &p->flags);
 			ret = wait_for_completion_interruptible(&p->complete);
 			if (ret)
 				return ret;
 		} while (p->flags & BIT(FLAG_STOP));
 	}

 	return was_on;
 }

 static int
 gpio_pwm_config(struct pwm_channel *p,
 		struct pwm_channel_config *c)
 {
 	struct gpio_pwm *gp = to_gpio_pwm(p);
 	int was_on = 0;

 	if (p->pwm->config_nosleep) {
 		if (!p->pwm->config_nosleep(p, c))
 			return 0;
 	}

 	might_sleep();

 	was_on = gpio_pwm_stop_sync(p);
 	if (was_on < 0)
 		return was_on;

 	if (c->config_mask & PWM_CONFIG_PERIOD_TICKS)
 		p->period_ticks = c->period_ticks;

 	if (c->config_mask & PWM_CONFIG_DUTY_TICKS)
 		p->duty_ticks = c->duty_ticks;

 	if (c->config_mask & PWM_CONFIG_POLARITY) {
 		gp->polarity = c->polarity ? 1 : 0;
 		p->active_high = gp->polarity;
 	}

 	if ((c->config_mask & PWM_CONFIG_START)
 	    || (was_on && !(c->config_mask & PWM_CONFIG_STOP)))
 		gpio_pwm_start(p);

 	return 0;
 }

 static int
 gpio_pwm_set_callback(struct pwm_channel *p,
 		      pwm_callback_t callback)
 {
 	struct gpio_pwm *gp = to_gpio_pwm(p);
 	gp->callback = callback;
 	return 0;
 }

 static int
 gpio_pwm_request(struct pwm_channel *p)
 {
 	p->tick_hz = 1000000000UL;
 	return 0;
 }

 static int __devinit
 gpio_pwm_probe(struct platform_device *pdev)
 {
 	struct gpio_pwm *gp;
 	struct gpio_pwm_platform_data *gpd = pdev->dev.platform_data;
 	int ret = 0;

 	/* TODO: create configfs entries, so users can assign GPIOs to
 	 * PWMs at runtime instead of creating a platform_device
 	 * specification and rebuilding their kernel */

 	if (!gpd || gpio_request(gpd->gpio, dev_name(&pdev->dev)))
 		return -EINVAL;

 	gp = kzalloc(sizeof(*gp), GFP_KERNEL);
 	if (!gp) {
 		ret = -ENOMEM;
 		goto err_alloc;
 	}

 	platform_set_drvdata(pdev, gp);

 	gp->pwm.dev = &pdev->dev;
 	gp->pwm.bus_id = dev_name(&pdev->dev);
 	gp->pwm.nchan = 1;
 	gp->gpio = gpd->gpio;

 	INIT_WORK(&gp->work, gpio_pwm_work);

 	hrtimer_init(&gp->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	gp->timer.function = gpio_pwm_timeout;

 	gp->pwm.owner = THIS_MODULE;
 	gp->pwm.config_nosleep = gpio_pwm_config_nosleep;
 	gp->pwm.config = gpio_pwm_config;
 	gp->pwm.request = gpio_pwm_request;
 	gp->pwm.set_callback = gpio_pwm_set_callback;

 	ret = pwm_register(&gp->pwm);
 	if (ret)
 		goto err_pwm_register;

 	return 0;

 err_pwm_register:
 	platform_set_drvdata(pdev, 0);
 	kfree(gp);
 err_alloc:
 	return ret;
 }

 static int __devexit
 gpio_pwm_remove(struct platform_device *pdev)
 {
 	struct gpio_pwm *gp = platform_get_drvdata(pdev);
 	int ret;

 	ret = pwm_unregister(&gp->pwm);
 	hrtimer_cancel(&gp->timer);
 	cancel_work_sync(&gp->work);
 	platform_set_drvdata(pdev, 0);
 	kfree(gp);

 	return 0;
 }

 static struct platform_driver gpio_pwm_driver = {
 	.driver = {
 		.name = "gpio_pwm",
 		.owner = THIS_MODULE,
 	},
 	.probe = gpio_pwm_probe,
 	.remove = __devexit_p(gpio_pwm_remove),
 };

 static int __init gpio_pwm_init(void)
 {
 	return platform_driver_register(&gpio_pwm_driver);
 }
 module_init(gpio_pwm_init);

 static void __exit gpio_pwm_exit(void)
 {
 	platform_driver_unregister(&gpio_pwm_driver);
 }
 module_exit(gpio_pwm_exit);

 MODULE_AUTHOR("Bill Gatliff <bgat@billgatliff.com>");
 MODULE_DESCRIPTION("PWM output using GPIO and a high-resolution timer");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:gpio_pwm");
	/*
	* drivers/pwm/gpio.c
	*
	* Models a single-channel PWM device using a timer and a GPIO pin.
	*
	* Copyright (C) 2010 Bill Gatliff <bgat@billgatliff.com>
	*
	* This program is free software; you may redistribute 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.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
	* USA
	*/

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/hrtimer.h>
	#include <linux/err.h>
	#include <linux/platform_device.h>
	#include <linux/workqueue.h>
	#include <linux/gpio.h>
	#include <linux/slab.h>
	#include <linux/pwm/pwm.h>

	struct gpio_pwm {
	struct pwm_device pwm;
	struct hrtimer timer;
	struct work_struct work;
	pwm_callback_t callback;
	int gpio;
	unsigned long polarity : 1;
	unsigned long active : 1;
	};

	static inline struct gpio_pwm to_gpio_pwm(const struct pwm_channel p)
	{
	return container_of(p->pwm, struct gpio_pwm, pwm);
	}

	static void
	gpio_pwm_work (struct work_struct *work)
	{
	struct gpio_pwm *gp = container_of(work, struct gpio_pwm, work);

	if (gp->active)
	gpio_direction_output(gp->gpio, gp->polarity ? 1 : 0);
	else
	gpio_direction_output(gp->gpio, gp->polarity ? 0 : 1);
	}

	static enum hrtimer_restart
	gpio_pwm_timeout(struct hrtimer *t)
	{
	struct gpio_pwm *gp = container_of(t, struct gpio_pwm, timer);
	ktime_t tnew;

	if (unlikely(gp->pwm.channels[0].duty_ticks == 0))
	gp->active = 0;
	else if (unlikely(gp->pwm.channels[0].duty_ticks
	== gp->pwm.channels[0].period_ticks))
	gp->active = 1;
	else
	gp->active ^= 1;

	if (gpio_cansleep(gp->gpio))
	schedule_work(&gp->work);
	else
	gpio_pwm_work(&gp->work);

	if (!gp->active && gp->pwm.channels[0].callback)
	gp->pwm.channels[0].callback(&gp->pwm.channels[0]);

	if (unlikely(!gp->active &&
	(gp->pwm.channels[0].flags & BIT(FLAG_STOP)))) {
	clear_bit(FLAG_STOP, &gp->pwm.channels[0].flags);
	complete_all(&gp->pwm.channels[0].complete);
	return HRTIMER_NORESTART;
	}

	if (gp->active)
	tnew = ktime_set(0, gp->pwm.channels[0].duty_ticks);
	else
	tnew = ktime_set(0, gp->pwm.channels[0].period_ticks
	- gp->pwm.channels[0].duty_ticks);
	hrtimer_start(&gp->timer, tnew, HRTIMER_MODE_REL);

	return HRTIMER_NORESTART;
	}

	static void gpio_pwm_start(struct pwm_channel *p)
	{
	struct gpio_pwm *gp = to_gpio_pwm(p);

	gp->active = 0;
	gpio_pwm_timeout(&gp->timer);
	}

	static int
	gpio_pwm_config_nosleep(struct pwm_channel *p,
	struct pwm_channel_config *c)
	{
	struct gpio_pwm *gp = to_gpio_pwm(p);
	int ret = 0;
	unsigned long flags;

	spin_lock_irqsave(&p->lock, flags);

	switch (c->config_mask) {

	case PWM_CONFIG_DUTY_TICKS:
	p->duty_ticks = c->duty_ticks;
	break;

	case PWM_CONFIG_START:
	if (!hrtimer_active(&gp->timer)) {
	gpio_pwm_start(p);
	}
	break;
	default:
	ret = -EINVAL;
	break;
	}

	spin_unlock_irqrestore(&p->lock, flags);
	return ret;
	}

	static int
	gpio_pwm_stop_sync(struct pwm_channel *p)
	{
	struct gpio_pwm *gp = to_gpio_pwm(p);
	int ret;
	int was_on = hrtimer_active(&gp->timer);

	if (was_on) {
	do {
	init_completion(&p->complete);
	set_bit(FLAG_STOP, &p->flags);
	ret = wait_for_completion_interruptible(&p->complete);
	if (ret)
	return ret;
	} while (p->flags & BIT(FLAG_STOP));
	}

	return was_on;
	}

	static int
	gpio_pwm_config(struct pwm_channel *p,
	struct pwm_channel_config *c)
	{
	struct gpio_pwm *gp = to_gpio_pwm(p);
	int was_on = 0;

	if (p->pwm->config_nosleep) {
	if (!p->pwm->config_nosleep(p, c))
	return 0;
	}

	might_sleep();

	was_on = gpio_pwm_stop_sync(p);
	if (was_on < 0)
	return was_on;

	if (c->config_mask & PWM_CONFIG_PERIOD_TICKS)
	p->period_ticks = c->period_ticks;

	if (c->config_mask & PWM_CONFIG_DUTY_TICKS)
	p->duty_ticks = c->duty_ticks;

	if (c->config_mask & PWM_CONFIG_POLARITY) {
	gp->polarity = c->polarity ? 1 : 0;
	p->active_high = gp->polarity;
	}

	if ((c->config_mask & PWM_CONFIG_START)
	\|\| (was_on && !(c->config_mask & PWM_CONFIG_STOP)))
	gpio_pwm_start(p);

	return 0;
	}

	static int
	gpio_pwm_set_callback(struct pwm_channel *p,
	pwm_callback_t callback)
	{
	struct gpio_pwm *gp = to_gpio_pwm(p);
	gp->callback = callback;
	return 0;
	}

	static int
	gpio_pwm_request(struct pwm_channel *p)
	{
	p->tick_hz = 1000000000UL;
	return 0;
	}

	static int __devinit
	gpio_pwm_probe(struct platform_device *pdev)
	{
	struct gpio_pwm *gp;
	struct gpio_pwm_platform_data *gpd = pdev->dev.platform_data;
	int ret = 0;

	/* TODO: create configfs entries, so users can assign GPIOs to
	* PWMs at runtime instead of creating a platform_device
	* specification and rebuilding their kernel */

	if (!gpd \|\| gpio_request(gpd->gpio, dev_name(&pdev->dev)))
	return -EINVAL;

	gp = kzalloc(sizeof(*gp), GFP_KERNEL);
	if (!gp) {
	ret = -ENOMEM;
	goto err_alloc;
	}

	platform_set_drvdata(pdev, gp);

	gp->pwm.dev = &pdev->dev;
	gp->pwm.bus_id = dev_name(&pdev->dev);
	gp->pwm.nchan = 1;
	gp->gpio = gpd->gpio;

	INIT_WORK(&gp->work, gpio_pwm_work);

	hrtimer_init(&gp->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	gp->timer.function = gpio_pwm_timeout;

	gp->pwm.owner = THIS_MODULE;
	gp->pwm.config_nosleep = gpio_pwm_config_nosleep;
	gp->pwm.config = gpio_pwm_config;
	gp->pwm.request = gpio_pwm_request;
	gp->pwm.set_callback = gpio_pwm_set_callback;

	ret = pwm_register(&gp->pwm);
	if (ret)
	goto err_pwm_register;

	return 0;

	err_pwm_register:
	platform_set_drvdata(pdev, 0);
	kfree(gp);
	err_alloc:
	return ret;
	}

	static int __devexit
	gpio_pwm_remove(struct platform_device *pdev)
	{
	struct gpio_pwm *gp = platform_get_drvdata(pdev);
	int ret;

	ret = pwm_unregister(&gp->pwm);
	hrtimer_cancel(&gp->timer);
	cancel_work_sync(&gp->work);
	platform_set_drvdata(pdev, 0);
	kfree(gp);

	return 0;
	}

	static struct platform_driver gpio_pwm_driver = {
	.driver = {
	.name = "gpio_pwm",
	.owner = THIS_MODULE,
	},
	.probe = gpio_pwm_probe,
	.remove = __devexit_p(gpio_pwm_remove),
	};

	static int __init gpio_pwm_init(void)
	{
	return platform_driver_register(&gpio_pwm_driver);
	}
	module_init(gpio_pwm_init);

	static void __exit gpio_pwm_exit(void)
	{
	platform_driver_unregister(&gpio_pwm_driver);
	}
	module_exit(gpio_pwm_exit);

	MODULE_AUTHOR("Bill Gatliff <bgat@billgatliff.com>");
	MODULE_DESCRIPTION("PWM output using GPIO and a high-resolution timer");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("platform:gpio_pwm");