drivers/iio/proximity/srf04.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * SRF04: ultrasonic sensor for distance measuring by using GPIOs
   4  *
   5  * Copyright (c) 2017 Andreas Klinger <ak@it-klinger.de>
   6  *
   7  * For details about the device see:
   8  * http://www.robot-electronics.co.uk/htm/srf04tech.htm
   9  *
  10  * the measurement cycle as timing diagram looks like:
  11  *
  12  *          +---+
  13  * GPIO     |   |
  14  * trig:  --+   +------------------------------------------------------
  15  *          ^   ^
  16  *          |<->|
  17  *         udelay(trigger_pulse_us)
  18  *
  19  * ultra           +-+ +-+ +-+
  20  * sonic           | | | | | |
  21  * burst: ---------+ +-+ +-+ +-----------------------------------------
  22  *                           .
  23  * ultra                     .              +-+ +-+ +-+
  24  * sonic                     .              | | | | | |
  25  * echo:  ----------------------------------+ +-+ +-+ +----------------
  26  *                           .                        .
  27  *                           +------------------------+
  28  * GPIO                      |                        |
  29  * echo:  -------------------+                        +---------------
  30  *                           ^                        ^
  31  *                           interrupt                interrupt
  32  *                           (ts_rising)              (ts_falling)
  33  *                           |<---------------------->|
  34  *                              pulse time measured
  35  *                              --> one round trip of ultra sonic waves
  36  */
  37 #include <linux/err.h>
  38 #include <linux/gpio/consumer.h>
  39 #include <linux/kernel.h>
  40 #include <linux/module.h>
  41 #include <linux/of.h>
  42 #include <linux/of_device.h>
  43 #include <linux/platform_device.h>
  44 #include <linux/property.h>
  45 #include <linux/sched.h>
  46 #include <linux/interrupt.h>
  47 #include <linux/delay.h>
  48 #include <linux/iio/iio.h>
  49 #include <linux/iio/sysfs.h>
  50
  51 struct srf04_cfg {
  52         unsigned long trigger_pulse_us;
  53 };
  54
  55 struct srf04_data {
  56         struct device           *dev;
  57         struct gpio_desc        *gpiod_trig;
  58         struct gpio_desc        *gpiod_echo;
  59         struct mutex            lock;
  60         int                     irqnr;
  61         ktime_t                 ts_rising;
  62         ktime_t                 ts_falling;
  63         struct completion       rising;
  64         struct completion       falling;
  65         const struct srf04_cfg  *cfg;
  66 };
  67
  68 static const struct srf04_cfg srf04_cfg = {
  69         .trigger_pulse_us = 10,
  70 };
  71
  72 static const struct srf04_cfg mb_lv_cfg = {
  73         .trigger_pulse_us = 20,
  74 };
  75
  76 static irqreturn_t srf04_handle_irq(int irq, void *dev_id)
  77 {
  78         struct iio_dev *indio_dev = dev_id;
  79         struct srf04_data *data = iio_priv(indio_dev);
  80         ktime_t now = ktime_get();
  81
  82         if (gpiod_get_value(data->gpiod_echo)) {
  83                 data->ts_rising = now;
  84                 complete(&data->rising);
  85         } else {
  86                 data->ts_falling = now;
  87                 complete(&data->falling);
  88         }
  89
  90         return IRQ_HANDLED;
  91 }
  92
  93 static int srf04_read(struct srf04_data *data)
  94 {
  95         int ret;
  96         ktime_t ktime_dt;
  97         u64 dt_ns;
  98         u32 time_ns, distance_mm;
  99
 100         /*
 101          * just one read-echo-cycle can take place at a time
 102          * ==> lock against concurrent reading calls
 103          */
 104         mutex_lock(&data->lock);
 105
 106         reinit_completion(&data->rising);
 107         reinit_completion(&data->falling);
 108
 109         gpiod_set_value(data->gpiod_trig, 1);
 110         udelay(data->cfg->trigger_pulse_us);
 111         gpiod_set_value(data->gpiod_trig, 0);
 112
 113         /* it cannot take more than 20 ms */
 114         ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
 115         if (ret < 0) {
 116                 mutex_unlock(&data->lock);
 117                 return ret;
 118         } else if (ret == 0) {
 119                 mutex_unlock(&data->lock);
 120                 return -ETIMEDOUT;
 121         }
 122
 123         ret = wait_for_completion_killable_timeout(&data->falling, HZ/50);
 124         if (ret < 0) {
 125                 mutex_unlock(&data->lock);
 126                 return ret;
 127         } else if (ret == 0) {
 128                 mutex_unlock(&data->lock);
 129                 return -ETIMEDOUT;
 130         }
 131
 132         ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
 133
 134         mutex_unlock(&data->lock);
 135
 136         dt_ns = ktime_to_ns(ktime_dt);
 137         /*
 138          * measuring more than 3 meters is beyond the capabilities of
 139          * the sensor
 140          * ==> filter out invalid results for not measuring echos of
 141          *     another us sensor
 142          *
 143          * formula:
 144          *         distance       3 m
 145          * time = ---------- = --------- = 9404389 ns
 146          *          speed       319 m/s
 147          *
 148          * using a minimum speed at -20 °C of 319 m/s
 149          */
 150         if (dt_ns > 9404389)
 151                 return -EIO;
 152
 153         time_ns = dt_ns;
 154
 155         /*
 156          * the speed as function of the temperature is approximately:
 157          *
 158          * speed = 331,5 + 0,6 * Temp
 159          *   with Temp in °C
 160          *   and speed in m/s
 161          *
 162          * use 343 m/s as ultrasonic speed at 20 °C here in absence of the
 163          * temperature
 164          *
 165          * therefore:
 166          *             time     343
 167          * distance = ------ * -----
 168          *             10^6       2
 169          *   with time in ns
 170          *   and distance in mm (one way)
 171          *
 172          * because we limit to 3 meters the multiplication with 343 just
 173          * fits into 32 bit
 174          */
 175         distance_mm = time_ns * 343 / 2000000;
 176
 177         return distance_mm;
 178 }
 179
 180 static int srf04_read_raw(struct iio_dev *indio_dev,
 181                             struct iio_chan_spec const *channel, int *val,
 182                             int *val2, long info)
 183 {
 184         struct srf04_data *data = iio_priv(indio_dev);
 185         int ret;
 186
 187         if (channel->type != IIO_DISTANCE)
 188                 return -EINVAL;
 189
 190         switch (info) {
 191         case IIO_CHAN_INFO_RAW:
 192                 ret = srf04_read(data);
 193                 if (ret < 0)
 194                         return ret;
 195                 *val = ret;
 196                 return IIO_VAL_INT;
 197         case IIO_CHAN_INFO_SCALE:
 198                 /*
 199                  * theoretical maximum resolution is 3 mm
 200                  * 1 LSB is 1 mm
 201                  */
 202                 *val = 0;
 203                 *val2 = 1000;
 204                 return IIO_VAL_INT_PLUS_MICRO;
 205         default:
 206                 return -EINVAL;
 207         }
 208 }
 209
 210 static const struct iio_info srf04_iio_info = {
 211         .read_raw               = srf04_read_raw,
 212 };
 213
 214 static const struct iio_chan_spec srf04_chan_spec[] = {
 215         {
 216                 .type = IIO_DISTANCE,
 217                 .info_mask_separate =
 218                                 BIT(IIO_CHAN_INFO_RAW) |
 219                                 BIT(IIO_CHAN_INFO_SCALE),
 220         },
 221 };
 222
 223 static const struct of_device_id of_srf04_match[] = {
 224         { .compatible = "devantech,srf04", .data = &srf04_cfg},
 225         { .compatible = "maxbotix,mb1000", .data = &mb_lv_cfg},
 226         { .compatible = "maxbotix,mb1010", .data = &mb_lv_cfg},
 227         { .compatible = "maxbotix,mb1020", .data = &mb_lv_cfg},
 228         { .compatible = "maxbotix,mb1030", .data = &mb_lv_cfg},
 229         { .compatible = "maxbotix,mb1040", .data = &mb_lv_cfg},
 230         {},
 231 };
 232
 233 MODULE_DEVICE_TABLE(of, of_srf04_match);
 234
 235 static int srf04_probe(struct platform_device *pdev)
 236 {
 237         struct device *dev = &pdev->dev;
 238         struct srf04_data *data;
 239         struct iio_dev *indio_dev;
 240         int ret;
 241
 242         indio_dev = devm_iio_device_alloc(dev, sizeof(struct srf04_data));
 243         if (!indio_dev) {
 244                 dev_err(dev, "failed to allocate IIO device\n");
 245                 return -ENOMEM;
 246         }
 247
 248         data = iio_priv(indio_dev);
 249         data->dev = dev;
 250         data->cfg = of_match_device(of_srf04_match, dev)->data;
 251
 252         mutex_init(&data->lock);
 253         init_completion(&data->rising);
 254         init_completion(&data->falling);
 255
 256         data->gpiod_trig = devm_gpiod_get(dev, "trig", GPIOD_OUT_LOW);
 257         if (IS_ERR(data->gpiod_trig)) {
 258                 dev_err(dev, "failed to get trig-gpios: err=%ld\n",
 259                                         PTR_ERR(data->gpiod_trig));
 260                 return PTR_ERR(data->gpiod_trig);
 261         }
 262
 263         data->gpiod_echo = devm_gpiod_get(dev, "echo", GPIOD_IN);
 264         if (IS_ERR(data->gpiod_echo)) {
 265                 dev_err(dev, "failed to get echo-gpios: err=%ld\n",
 266                                         PTR_ERR(data->gpiod_echo));
 267                 return PTR_ERR(data->gpiod_echo);
 268         }
 269
 270         if (gpiod_cansleep(data->gpiod_echo)) {
 271                 dev_err(data->dev, "cansleep-GPIOs not supported\n");
 272                 return -ENODEV;
 273         }
 274
 275         data->irqnr = gpiod_to_irq(data->gpiod_echo);
 276         if (data->irqnr < 0) {
 277                 dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
 278                 return data->irqnr;
 279         }
 280
 281         ret = devm_request_irq(dev, data->irqnr, srf04_handle_irq,
 282                         IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
 283                         pdev->name, indio_dev);
 284         if (ret < 0) {
 285                 dev_err(data->dev, "request_irq: %d\n", ret);
 286                 return ret;
 287         }
 288
 289         platform_set_drvdata(pdev, indio_dev);
 290
 291         indio_dev->name = "srf04";
 292         indio_dev->dev.parent = &pdev->dev;
 293         indio_dev->info = &srf04_iio_info;
 294         indio_dev->modes = INDIO_DIRECT_MODE;
 295         indio_dev->channels = srf04_chan_spec;
 296         indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);
 297
 298         return devm_iio_device_register(dev, indio_dev);
 299 }
 300
 301 static struct platform_driver srf04_driver = {
 302         .probe          = srf04_probe,
 303         .driver         = {
 304                 .name           = "srf04-gpio",
 305                 .of_match_table = of_srf04_match,
 306         },
 307 };
 308
 309 module_platform_driver(srf04_driver);
 310
 311 MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
 312 MODULE_DESCRIPTION("SRF04 ultrasonic sensor for distance measuring using GPIOs");
 313 MODULE_LICENSE("GPL");
 314 MODULE_ALIAS("platform:srf04");