299 lines
6.6 KiB
C
299 lines
6.6 KiB
C
/*
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* drivers/pwm/gpio.c
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*
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* Models a single-channel PWM device using a timer and a GPIO pin.
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*
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* Copyright (C) 2010 Bill Gatliff <bgat@billgatliff.com>
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*
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* This program is free software; you may redistribute and/or modify
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* it under the terms of the GNU General Public License Version 2, as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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* USA
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/hrtimer.h>
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#include <linux/err.h>
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#include <linux/platform_device.h>
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#include <linux/workqueue.h>
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#include <linux/gpio.h>
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#include <linux/slab.h>
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#include <linux/pwm/pwm.h>
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struct gpio_pwm {
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struct pwm_device pwm;
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struct hrtimer timer;
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struct work_struct work;
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pwm_callback_t callback;
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int gpio;
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unsigned long polarity : 1;
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unsigned long active : 1;
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};
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static inline struct gpio_pwm *to_gpio_pwm(const struct pwm_channel *p)
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{
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return container_of(p->pwm, struct gpio_pwm, pwm);
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}
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static void
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gpio_pwm_work (struct work_struct *work)
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{
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struct gpio_pwm *gp = container_of(work, struct gpio_pwm, work);
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if (gp->active)
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gpio_direction_output(gp->gpio, gp->polarity ? 1 : 0);
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else
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gpio_direction_output(gp->gpio, gp->polarity ? 0 : 1);
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}
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static enum hrtimer_restart
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gpio_pwm_timeout(struct hrtimer *t)
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{
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struct gpio_pwm *gp = container_of(t, struct gpio_pwm, timer);
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ktime_t tnew;
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if (unlikely(gp->pwm.channels[0].duty_ticks == 0))
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gp->active = 0;
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else if (unlikely(gp->pwm.channels[0].duty_ticks
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== gp->pwm.channels[0].period_ticks))
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gp->active = 1;
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else
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gp->active ^= 1;
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if (gpio_cansleep(gp->gpio))
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schedule_work(&gp->work);
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else
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gpio_pwm_work(&gp->work);
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if (!gp->active && gp->pwm.channels[0].callback)
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gp->pwm.channels[0].callback(&gp->pwm.channels[0]);
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if (unlikely(!gp->active &&
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(gp->pwm.channels[0].flags & BIT(FLAG_STOP)))) {
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clear_bit(FLAG_STOP, &gp->pwm.channels[0].flags);
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complete_all(&gp->pwm.channels[0].complete);
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return HRTIMER_NORESTART;
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}
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if (gp->active)
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tnew = ktime_set(0, gp->pwm.channels[0].duty_ticks);
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else
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tnew = ktime_set(0, gp->pwm.channels[0].period_ticks
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- gp->pwm.channels[0].duty_ticks);
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hrtimer_start(&gp->timer, tnew, HRTIMER_MODE_REL);
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return HRTIMER_NORESTART;
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}
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static void gpio_pwm_start(struct pwm_channel *p)
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{
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struct gpio_pwm *gp = to_gpio_pwm(p);
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gp->active = 0;
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gpio_pwm_timeout(&gp->timer);
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}
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static int
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gpio_pwm_config_nosleep(struct pwm_channel *p,
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struct pwm_channel_config *c)
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{
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struct gpio_pwm *gp = to_gpio_pwm(p);
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int ret = 0;
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unsigned long flags;
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spin_lock_irqsave(&p->lock, flags);
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switch (c->config_mask) {
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case PWM_CONFIG_DUTY_TICKS:
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p->duty_ticks = c->duty_ticks;
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break;
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case PWM_CONFIG_START:
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if (!hrtimer_active(&gp->timer)) {
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gpio_pwm_start(p);
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}
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break;
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default:
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ret = -EINVAL;
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break;
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}
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spin_unlock_irqrestore(&p->lock, flags);
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return ret;
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}
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static int
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gpio_pwm_stop_sync(struct pwm_channel *p)
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{
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struct gpio_pwm *gp = to_gpio_pwm(p);
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int ret;
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int was_on = hrtimer_active(&gp->timer);
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if (was_on) {
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do {
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init_completion(&p->complete);
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set_bit(FLAG_STOP, &p->flags);
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ret = wait_for_completion_interruptible(&p->complete);
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if (ret)
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return ret;
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} while (p->flags & BIT(FLAG_STOP));
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}
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return was_on;
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}
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static int
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gpio_pwm_config(struct pwm_channel *p,
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struct pwm_channel_config *c)
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{
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struct gpio_pwm *gp = to_gpio_pwm(p);
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int was_on = 0;
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if (p->pwm->config_nosleep) {
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if (!p->pwm->config_nosleep(p, c))
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return 0;
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}
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might_sleep();
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was_on = gpio_pwm_stop_sync(p);
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if (was_on < 0)
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return was_on;
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if (c->config_mask & PWM_CONFIG_PERIOD_TICKS)
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p->period_ticks = c->period_ticks;
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if (c->config_mask & PWM_CONFIG_DUTY_TICKS)
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p->duty_ticks = c->duty_ticks;
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if (c->config_mask & PWM_CONFIG_POLARITY) {
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gp->polarity = c->polarity ? 1 : 0;
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p->active_high = gp->polarity;
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}
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if ((c->config_mask & PWM_CONFIG_START)
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|| (was_on && !(c->config_mask & PWM_CONFIG_STOP)))
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gpio_pwm_start(p);
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return 0;
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}
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static int
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gpio_pwm_set_callback(struct pwm_channel *p,
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pwm_callback_t callback)
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{
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struct gpio_pwm *gp = to_gpio_pwm(p);
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gp->callback = callback;
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return 0;
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}
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static int
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gpio_pwm_request(struct pwm_channel *p)
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{
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p->tick_hz = 1000000000UL;
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return 0;
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}
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static int __devinit
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gpio_pwm_probe(struct platform_device *pdev)
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{
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struct gpio_pwm *gp;
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struct gpio_pwm_platform_data *gpd = pdev->dev.platform_data;
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int ret = 0;
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/* TODO: create configfs entries, so users can assign GPIOs to
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* PWMs at runtime instead of creating a platform_device
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* specification and rebuilding their kernel */
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if (!gpd || gpio_request(gpd->gpio, dev_name(&pdev->dev)))
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return -EINVAL;
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gp = kzalloc(sizeof(*gp), GFP_KERNEL);
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if (!gp) {
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ret = -ENOMEM;
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goto err_alloc;
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}
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platform_set_drvdata(pdev, gp);
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gp->pwm.dev = &pdev->dev;
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gp->pwm.bus_id = dev_name(&pdev->dev);
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gp->pwm.nchan = 1;
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gp->gpio = gpd->gpio;
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INIT_WORK(&gp->work, gpio_pwm_work);
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hrtimer_init(&gp->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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gp->timer.function = gpio_pwm_timeout;
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gp->pwm.owner = THIS_MODULE;
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gp->pwm.config_nosleep = gpio_pwm_config_nosleep;
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gp->pwm.config = gpio_pwm_config;
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gp->pwm.request = gpio_pwm_request;
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gp->pwm.set_callback = gpio_pwm_set_callback;
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ret = pwm_register(&gp->pwm);
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if (ret)
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goto err_pwm_register;
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return 0;
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err_pwm_register:
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platform_set_drvdata(pdev, 0);
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kfree(gp);
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err_alloc:
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return ret;
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}
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static int __devexit
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gpio_pwm_remove(struct platform_device *pdev)
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{
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struct gpio_pwm *gp = platform_get_drvdata(pdev);
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int ret;
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ret = pwm_unregister(&gp->pwm);
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hrtimer_cancel(&gp->timer);
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cancel_work_sync(&gp->work);
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platform_set_drvdata(pdev, 0);
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kfree(gp);
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return 0;
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}
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static struct platform_driver gpio_pwm_driver = {
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.driver = {
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.name = "gpio_pwm",
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.owner = THIS_MODULE,
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},
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.probe = gpio_pwm_probe,
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.remove = __devexit_p(gpio_pwm_remove),
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};
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static int __init gpio_pwm_init(void)
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{
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return platform_driver_register(&gpio_pwm_driver);
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}
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module_init(gpio_pwm_init);
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static void __exit gpio_pwm_exit(void)
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{
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platform_driver_unregister(&gpio_pwm_driver);
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}
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module_exit(gpio_pwm_exit);
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MODULE_AUTHOR("Bill Gatliff <bgat@billgatliff.com>");
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MODULE_DESCRIPTION("PWM output using GPIO and a high-resolution timer");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("platform:gpio_pwm");
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