aboutsummaryrefslogtreecommitdiffstats
path: root/target/linux/generic/files/drivers/pwm/gpio-pwm.c
blob: dff5d1d6275183556370214681f670b3282a9162 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
/*
 * 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");