target/linux/generic/files/drivers/pwm/gpio.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
  33 struct 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
  43 static 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
  48 static void
  49 gpio_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
  59 static enum hrtimer_restart
  60 gpio_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
  98 static 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
 106 static int
 107 gpio_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
 136 static int
 137 gpio_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
 156 static int
 157 gpio_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
 192 static int
 193 gpio_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
 201 static int
 202 gpio_pwm_request(struct pwm_channel *p)
 203 {
 204         p->tick_hz = 1000000000UL;
 205         return 0;
 206 }
 207
 208 static int __devinit
 209 gpio_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
 252 err_pwm_register:
 253         platform_set_drvdata(pdev, 0);
 254         kfree(gp);
 255 err_alloc:
 256         return ret;
 257 }
 258
 259 static int __devexit
 260 gpio_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
 274 static 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
 283 static int __init gpio_pwm_init(void)
 284 {
 285         return platform_driver_register(&gpio_pwm_driver);
 286 }
 287 module_init(gpio_pwm_init);
 288
 289 static void __exit gpio_pwm_exit(void)
 290 {
 291         platform_driver_unregister(&gpio_pwm_driver);
 292 }
 293 module_exit(gpio_pwm_exit);
 294
 295 MODULE_AUTHOR("Bill Gatliff <bgat@billgatliff.com>");
 296 MODULE_DESCRIPTION("PWM output using GPIO and a high-resolution timer");
 297 MODULE_LICENSE("GPL");
 298 MODULE_ALIAS("platform:gpio_pwm");