Root/target/linux/generic/files/drivers/pwm/gpio-pwm.c

1/*
2 * drivers/pwm/gpio.c
3 *
4 * Models a single-channel PWM device using a timer and a GPIO pin.
5 *
6 * Copyright (C) 2010 Bill Gatliff <bgat@billgatliff.com>
7 *
8 * This program is free software; you may redistribute and/or modify
9 * it under the terms of the GNU General Public License Version 2, as
10 * published by the Free Software Foundation.
11 *
12 * This program is distributed in the hope that it will be useful, but
13 * WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
20 * USA
21 */
22
23#include <linux/module.h>
24#include <linux/init.h>
25#include <linux/hrtimer.h>
26#include <linux/err.h>
27#include <linux/platform_device.h>
28#include <linux/workqueue.h>
29#include <linux/gpio.h>
30#include <linux/slab.h>
31#include <linux/pwm/pwm.h>
32
33struct gpio_pwm {
34    struct pwm_device pwm;
35    struct hrtimer timer;
36    struct work_struct work;
37    pwm_callback_t callback;
38    int gpio;
39    unsigned long polarity : 1;
40    unsigned long active : 1;
41};
42
43static inline struct gpio_pwm *to_gpio_pwm(const struct pwm_channel *p)
44{
45    return container_of(p->pwm, struct gpio_pwm, pwm);
46}
47
48static void
49gpio_pwm_work (struct work_struct *work)
50{
51    struct gpio_pwm *gp = container_of(work, struct gpio_pwm, work);
52
53    if (gp->active)
54        gpio_direction_output(gp->gpio, gp->polarity ? 1 : 0);
55    else
56        gpio_direction_output(gp->gpio, gp->polarity ? 0 : 1);
57}
58
59static enum hrtimer_restart
60gpio_pwm_timeout(struct hrtimer *t)
61{
62    struct gpio_pwm *gp = container_of(t, struct gpio_pwm, timer);
63    ktime_t tnew;
64
65    if (unlikely(gp->pwm.channels[0].duty_ticks == 0))
66        gp->active = 0;
67    else if (unlikely(gp->pwm.channels[0].duty_ticks
68              == gp->pwm.channels[0].period_ticks))
69        gp->active = 1;
70    else
71        gp->active ^= 1;
72
73    if (gpio_cansleep(gp->gpio))
74        schedule_work(&gp->work);
75    else
76        gpio_pwm_work(&gp->work);
77
78    if (!gp->active && gp->pwm.channels[0].callback)
79        gp->pwm.channels[0].callback(&gp->pwm.channels[0]);
80
81    if (unlikely(!gp->active &&
82             (gp->pwm.channels[0].flags & BIT(FLAG_STOP)))) {
83        clear_bit(FLAG_STOP, &gp->pwm.channels[0].flags);
84        complete_all(&gp->pwm.channels[0].complete);
85        return HRTIMER_NORESTART;
86    }
87
88    if (gp->active)
89        tnew = ktime_set(0, gp->pwm.channels[0].duty_ticks);
90    else
91        tnew = ktime_set(0, gp->pwm.channels[0].period_ticks
92                 - gp->pwm.channels[0].duty_ticks);
93    hrtimer_start(&gp->timer, tnew, HRTIMER_MODE_REL);
94
95    return HRTIMER_NORESTART;
96}
97
98static void gpio_pwm_start(struct pwm_channel *p)
99{
100    struct gpio_pwm *gp = to_gpio_pwm(p);
101
102    gp->active = 0;
103    gpio_pwm_timeout(&gp->timer);
104}
105
106static int
107gpio_pwm_config_nosleep(struct pwm_channel *p,
108            struct pwm_channel_config *c)
109{
110    struct gpio_pwm *gp = to_gpio_pwm(p);
111    int ret = 0;
112    unsigned long flags;
113
114    spin_lock_irqsave(&p->lock, flags);
115
116    switch (c->config_mask) {
117
118    case PWM_CONFIG_DUTY_TICKS:
119        p->duty_ticks = c->duty_ticks;
120        break;
121
122    case PWM_CONFIG_START:
123        if (!hrtimer_active(&gp->timer)) {
124            gpio_pwm_start(p);
125        }
126        break;
127    default:
128        ret = -EINVAL;
129        break;
130    }
131
132    spin_unlock_irqrestore(&p->lock, flags);
133    return ret;
134}
135
136static int
137gpio_pwm_stop_sync(struct pwm_channel *p)
138{
139    struct gpio_pwm *gp = to_gpio_pwm(p);
140    int ret;
141    int was_on = hrtimer_active(&gp->timer);
142
143    if (was_on) {
144        do {
145            init_completion(&p->complete);
146            set_bit(FLAG_STOP, &p->flags);
147            ret = wait_for_completion_interruptible(&p->complete);
148            if (ret)
149                return ret;
150        } while (p->flags & BIT(FLAG_STOP));
151    }
152
153    return was_on;
154}
155
156static int
157gpio_pwm_config(struct pwm_channel *p,
158        struct pwm_channel_config *c)
159{
160    struct gpio_pwm *gp = to_gpio_pwm(p);
161    int was_on = 0;
162
163    if (p->pwm->config_nosleep) {
164        if (!p->pwm->config_nosleep(p, c))
165            return 0;
166    }
167
168    might_sleep();
169
170    was_on = gpio_pwm_stop_sync(p);
171    if (was_on < 0)
172        return was_on;
173
174    if (c->config_mask & PWM_CONFIG_PERIOD_TICKS)
175        p->period_ticks = c->period_ticks;
176
177    if (c->config_mask & PWM_CONFIG_DUTY_TICKS)
178        p->duty_ticks = c->duty_ticks;
179
180    if (c->config_mask & PWM_CONFIG_POLARITY) {
181        gp->polarity = c->polarity ? 1 : 0;
182        p->active_high = gp->polarity;
183    }
184
185    if ((c->config_mask & PWM_CONFIG_START)
186        || (was_on && !(c->config_mask & PWM_CONFIG_STOP)))
187        gpio_pwm_start(p);
188
189    return 0;
190}
191
192static int
193gpio_pwm_set_callback(struct pwm_channel *p,
194              pwm_callback_t callback)
195{
196    struct gpio_pwm *gp = to_gpio_pwm(p);
197    gp->callback = callback;
198    return 0;
199}
200
201static int
202gpio_pwm_request(struct pwm_channel *p)
203{
204    p->tick_hz = 1000000000UL;
205    return 0;
206}
207
208static int __devinit
209gpio_pwm_probe(struct platform_device *pdev)
210{
211    struct gpio_pwm *gp;
212    struct gpio_pwm_platform_data *gpd = pdev->dev.platform_data;
213    int ret = 0;
214
215    /* TODO: create configfs entries, so users can assign GPIOs to
216     * PWMs at runtime instead of creating a platform_device
217     * specification and rebuilding their kernel */
218
219    if (!gpd || gpio_request(gpd->gpio, dev_name(&pdev->dev)))
220        return -EINVAL;
221
222    gp = kzalloc(sizeof(*gp), GFP_KERNEL);
223    if (!gp) {
224        ret = -ENOMEM;
225        goto err_alloc;
226    }
227
228    platform_set_drvdata(pdev, gp);
229
230    gp->pwm.dev = &pdev->dev;
231    gp->pwm.bus_id = dev_name(&pdev->dev);
232    gp->pwm.nchan = 1;
233    gp->gpio = gpd->gpio;
234
235    INIT_WORK(&gp->work, gpio_pwm_work);
236
237    hrtimer_init(&gp->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
238    gp->timer.function = gpio_pwm_timeout;
239
240    gp->pwm.owner = THIS_MODULE;
241    gp->pwm.config_nosleep = gpio_pwm_config_nosleep;
242    gp->pwm.config = gpio_pwm_config;
243    gp->pwm.request = gpio_pwm_request;
244    gp->pwm.set_callback = gpio_pwm_set_callback;
245
246    ret = pwm_register(&gp->pwm);
247    if (ret)
248        goto err_pwm_register;
249
250    return 0;
251
252err_pwm_register:
253    platform_set_drvdata(pdev, 0);
254    kfree(gp);
255err_alloc:
256    return ret;
257}
258
259static int __devexit
260gpio_pwm_remove(struct platform_device *pdev)
261{
262    struct gpio_pwm *gp = platform_get_drvdata(pdev);
263    int ret;
264
265    ret = pwm_unregister(&gp->pwm);
266    hrtimer_cancel(&gp->timer);
267    cancel_work_sync(&gp->work);
268    platform_set_drvdata(pdev, 0);
269    kfree(gp);
270
271    return 0;
272}
273
274static struct platform_driver gpio_pwm_driver = {
275    .driver = {
276        .name = "gpio_pwm",
277        .owner = THIS_MODULE,
278    },
279    .probe = gpio_pwm_probe,
280    .remove = __devexit_p(gpio_pwm_remove),
281};
282
283static int __init gpio_pwm_init(void)
284{
285    return platform_driver_register(&gpio_pwm_driver);
286}
287module_init(gpio_pwm_init);
288
289static void __exit gpio_pwm_exit(void)
290{
291    platform_driver_unregister(&gpio_pwm_driver);
292}
293module_exit(gpio_pwm_exit);
294
295MODULE_AUTHOR("Bill Gatliff <bgat@billgatliff.com>");
296MODULE_DESCRIPTION("PWM output using GPIO and a high-resolution timer");
297MODULE_LICENSE("GPL");
298MODULE_ALIAS("platform:gpio_pwm");
299

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