drivers/iio/proximity/srf04.c

   1 /*
   2  * SRF04: ultrasonic sensor for distance measuring by using GPIOs
   3  *
   4  * Copyright (c) 2017 Andreas Klinger <ak@it-klinger.de>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * For details about the device see:
  17  * http://www.robot-electronics.co.uk/htm/srf04tech.htm
  18  *
  19  * the measurement cycle as timing diagram looks like:
  20  *
  21  *          +---+
  22  * GPIO     |   |
  23  * trig:  --+   +------------------------------------------------------
  24  *          ^   ^
  25  *          |<->|
  26  *         udelay(10)
  27  *
  28  * ultra           +-+ +-+ +-+
  29  * sonic           | | | | | |
  30  * burst: ---------+ +-+ +-+ +-----------------------------------------
  31  *                           .
  32  * ultra                     .              +-+ +-+ +-+
  33  * sonic                     .              | | | | | |
  34  * echo:  ----------------------------------+ +-+ +-+ +----------------
  35  *                           .                        .
  36  *                           +------------------------+
  37  * GPIO                      |                        |
  38  * echo:  -------------------+                        +---------------
  39  *                           ^                        ^
  40  *                           interrupt                interrupt
  41  *                           (ts_rising)              (ts_falling)
  42  *                           |<---------------------->|
  43  *                              pulse time measured
  44  *                              --> one round trip of ultra sonic waves
  45  */
  46 #include <linux/err.h>
  47 #include <linux/gpio/consumer.h>
  48 #include <linux/kernel.h>
  49 #include <linux/module.h>
  50 #include <linux/of.h>
  51 #include <linux/platform_device.h>
  52 #include <linux/property.h>
  53 #include <linux/sched.h>
  54 #include <linux/interrupt.h>
  55 #include <linux/delay.h>
  56 #include <linux/iio/iio.h>
  57 #include <linux/iio/sysfs.h>
  58
  59 struct srf04_data {
  60         struct device           *dev;
  61         struct gpio_desc        *gpiod_trig;
  62         struct gpio_desc        *gpiod_echo;
  63         struct mutex            lock;
  64         int                     irqnr;
  65         ktime_t                 ts_rising;
  66         ktime_t                 ts_falling;
  67         struct completion       rising;
  68         struct completion       falling;
  69 };
  70
  71 static irqreturn_t srf04_handle_irq(int irq, void *dev_id)
  72 {
  73         struct iio_dev *indio_dev = dev_id;
  74         struct srf04_data *data = iio_priv(indio_dev);
  75         ktime_t now = ktime_get();
  76
  77         if (gpiod_get_value(data->gpiod_echo)) {
  78                 data->ts_rising = now;
  79                 complete(&data->rising);
  80         } else {
  81                 data->ts_falling = now;
  82                 complete(&data->falling);
  83         }
  84
  85         return IRQ_HANDLED;
  86 }
  87
  88 static int srf04_read(struct srf04_data *data)
  89 {
  90         int ret;
  91         ktime_t ktime_dt;
  92         u64 dt_ns;
  93         u32 time_ns, distance_mm;
  94
  95         /*
  96          * just one read-echo-cycle can take place at a time
  97          * ==> lock against concurrent reading calls
  98          */
  99         mutex_lock(&data->lock);
 100
 101         reinit_completion(&data->rising);
 102         reinit_completion(&data->falling);
 103
 104         gpiod_set_value(data->gpiod_trig, 1);
 105         udelay(10);
 106         gpiod_set_value(data->gpiod_trig, 0);
 107
 108         /* it cannot take more than 20 ms */
 109         ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
 110         if (ret < 0) {
 111                 mutex_unlock(&data->lock);
 112                 return ret;
 113         } else if (ret == 0) {
 114                 mutex_unlock(&data->lock);
 115                 return -ETIMEDOUT;
 116         }
 117
 118         ret = wait_for_completion_killable_timeout(&data->falling, HZ/50);
 119         if (ret < 0) {
 120                 mutex_unlock(&data->lock);
 121                 return ret;
 122         } else if (ret == 0) {
 123                 mutex_unlock(&data->lock);
 124                 return -ETIMEDOUT;
 125         }
 126
 127         ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
 128
 129         mutex_unlock(&data->lock);
 130
 131         dt_ns = ktime_to_ns(ktime_dt);
 132         /*
 133          * measuring more than 3 meters is beyond the capabilities of
 134          * the sensor
 135          * ==> filter out invalid results for not measuring echos of
 136          *     another us sensor
 137          *
 138          * formula:
 139          *         distance       3 m
 140          * time = ---------- = --------- = 9404389 ns
 141          *          speed       319 m/s
 142          *
 143          * using a minimum speed at -20 °C of 319 m/s
 144          */
 145         if (dt_ns > 9404389)
 146                 return -EIO;
 147
 148         time_ns = dt_ns;
 149
 150         /*
 151          * the speed as function of the temperature is approximately:
 152          *
 153          * speed = 331,5 + 0,6 * Temp
 154          *   with Temp in °C
 155          *   and speed in m/s
 156          *
 157          * use 343 m/s as ultrasonic speed at 20 °C here in absence of the
 158          * temperature
 159          *
 160          * therefore:
 161          *             time     343
 162          * distance = ------ * -----
 163          *             10^6       2
 164          *   with time in ns
 165          *   and distance in mm (one way)
 166          *
 167          * because we limit to 3 meters the multiplication with 343 just
 168          * fits into 32 bit
 169          */
 170         distance_mm = time_ns * 343 / 2000000;
 171
 172         return distance_mm;
 173 }
 174
 175 static int srf04_read_raw(struct iio_dev *indio_dev,
 176                             struct iio_chan_spec const *channel, int *val,
 177                             int *val2, long info)
 178 {
 179         struct srf04_data *data = iio_priv(indio_dev);
 180         int ret;
 181
 182         if (channel->type != IIO_DISTANCE)
 183                 return -EINVAL;
 184
 185         switch (info) {
 186         case IIO_CHAN_INFO_RAW:
 187                 ret = srf04_read(data);
 188                 if (ret < 0)
 189                         return ret;
 190                 *val = ret;
 191                 return IIO_VAL_INT;
 192         case IIO_CHAN_INFO_SCALE:
 193                 /*
 194                  * theoretical maximum resolution is 3 mm
 195                  * 1 LSB is 1 mm
 196                  */
 197                 *val = 0;
 198                 *val2 = 1000;
 199                 return IIO_VAL_INT_PLUS_MICRO;
 200         default:
 201                 return -EINVAL;
 202         }
 203 }
 204
 205 static const struct iio_info srf04_iio_info = {
 206         .driver_module          = THIS_MODULE,
 207         .read_raw               = srf04_read_raw,
 208 };
 209
 210 static const struct iio_chan_spec srf04_chan_spec[] = {
 211         {
 212                 .type = IIO_DISTANCE,
 213                 .info_mask_separate =
 214                                 BIT(IIO_CHAN_INFO_RAW) |
 215                                 BIT(IIO_CHAN_INFO_SCALE),
 216         },
 217 };
 218
 219 static int srf04_probe(struct platform_device *pdev)
 220 {
 221         struct device *dev = &pdev->dev;
 222         struct srf04_data *data;
 223         struct iio_dev *indio_dev;
 224         int ret;
 225
 226         indio_dev = devm_iio_device_alloc(dev, sizeof(struct srf04_data));
 227         if (!indio_dev) {
 228                 dev_err(dev, "failed to allocate IIO device\n");
 229                 return -ENOMEM;
 230         }
 231
 232         data = iio_priv(indio_dev);
 233         data->dev = dev;
 234
 235         mutex_init(&data->lock);
 236         init_completion(&data->rising);
 237         init_completion(&data->falling);
 238
 239         data->gpiod_trig = devm_gpiod_get(dev, "trig", GPIOD_OUT_LOW);
 240         if (IS_ERR(data->gpiod_trig)) {
 241                 dev_err(dev, "failed to get trig-gpios: err=%ld\n",
 242                                         PTR_ERR(data->gpiod_trig));
 243                 return PTR_ERR(data->gpiod_trig);
 244         }
 245
 246         data->gpiod_echo = devm_gpiod_get(dev, "echo", GPIOD_IN);
 247         if (IS_ERR(data->gpiod_echo)) {
 248                 dev_err(dev, "failed to get echo-gpios: err=%ld\n",
 249                                         PTR_ERR(data->gpiod_echo));
 250                 return PTR_ERR(data->gpiod_echo);
 251         }
 252
 253         if (gpiod_cansleep(data->gpiod_echo)) {
 254                 dev_err(data->dev, "cansleep-GPIOs not supported\n");
 255                 return -ENODEV;
 256         }
 257
 258         data->irqnr = gpiod_to_irq(data->gpiod_echo);
 259         if (data->irqnr < 0) {
 260                 dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
 261                 return data->irqnr;
 262         }
 263
 264         ret = devm_request_irq(dev, data->irqnr, srf04_handle_irq,
 265                         IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
 266                         pdev->name, indio_dev);
 267         if (ret < 0) {
 268                 dev_err(data->dev, "request_irq: %d\n", ret);
 269                 return ret;
 270         }
 271
 272         platform_set_drvdata(pdev, indio_dev);
 273
 274         indio_dev->name = "srf04";
 275         indio_dev->dev.parent = &pdev->dev;
 276         indio_dev->info = &srf04_iio_info;
 277         indio_dev->modes = INDIO_DIRECT_MODE;
 278         indio_dev->channels = srf04_chan_spec;
 279         indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);
 280
 281         return devm_iio_device_register(dev, indio_dev);
 282 }
 283
 284 static const struct of_device_id of_srf04_match[] = {
 285         { .compatible = "devantech,srf04", },
 286         {},
 287 };
 288
 289 MODULE_DEVICE_TABLE(of, of_srf04_match);
 290
 291 static struct platform_driver srf04_driver = {
 292         .probe          = srf04_probe,
 293         .driver         = {
 294                 .name           = "srf04-gpio",
 295                 .of_match_table = of_srf04_match,
 296         },
 297 };
 298
 299 module_platform_driver(srf04_driver);
 300
 301 MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
 302 MODULE_DESCRIPTION("SRF04 ultrasonic sensor for distance measuring using GPIOs");
 303 MODULE_LICENSE("GPL");
 304 MODULE_ALIAS("platform:srf04");