drivers/iio/proximity/ping.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * PING: ultrasonic sensor for distance measuring by using only one GPIOs
   4  *
   5  * Copyright (c) 2019 Andreas Klinger <ak@it-klinger.de>
   6  *
   7  * For details about the devices see:
   8  * http://parallax.com/sites/default/files/downloads/28041-LaserPING-2m-Rangefinder-Guide.pdf
   9  * http://parallax.com/sites/default/files/downloads/28015-PING-Documentation-v1.6.pdf
  10  *
  11  * the measurement cycle as timing diagram looks like:
  12  *
  13  * GPIO      ___              ________________________
  14  * ping:  __/   \____________/                        \________________
  15  *          ^   ^            ^                        ^
  16  *          |<->|            interrupt                interrupt
  17  *         udelay(5)         (ts_rising)              (ts_falling)
  18  *                           |<---------------------->|
  19  *                           .  pulse time measured   .
  20  *                           .  --> one round trip of ultra sonic waves
  21  * ultra                     .                        .
  22  * sonic            _   _   _.                        .
  23  * burst: _________/ \_/ \_/ \_________________________________________
  24  *                                                    .
  25  * ultra                                              .
  26  * sonic                                     _   _   _.
  27  * echo:  __________________________________/ \_/ \_/ \________________
  28  */
  29 #include <linux/err.h>
  30 #include <linux/gpio/consumer.h>
  31 #include <linux/kernel.h>
  32 #include <linux/module.h>
  33 #include <linux/of.h>
  34 #include <linux/of_device.h>
  35 #include <linux/platform_device.h>
  36 #include <linux/property.h>
  37 #include <linux/sched.h>
  38 #include <linux/interrupt.h>
  39 #include <linux/delay.h>
  40 #include <linux/iio/iio.h>
  41 #include <linux/iio/sysfs.h>
  42
  43 struct ping_cfg {
  44         unsigned long   trigger_pulse_us;       /* length of trigger pulse */
  45         int             laserping_error;        /* support error code in */
  46                                                 /*   pulse width of laser */
  47                                                 /*   ping sensors */
  48         s64             timeout_ns;             /* timeout in ns */
  49 };
  50
  51 struct ping_data {
  52         struct device           *dev;
  53         struct gpio_desc        *gpiod_ping;
  54         struct mutex            lock;
  55         int                     irqnr;
  56         ktime_t                 ts_rising;
  57         ktime_t                 ts_falling;
  58         struct completion       rising;
  59         struct completion       falling;
  60         const struct ping_cfg   *cfg;
  61 };
  62
  63 static const struct ping_cfg pa_ping_cfg = {
  64         .trigger_pulse_us       = 5,
  65         .laserping_error        = 0,
  66         .timeout_ns             = 18500000,     /* 3 meters */
  67 };
  68
  69 static const struct ping_cfg pa_laser_ping_cfg = {
  70         .trigger_pulse_us       = 5,
  71         .laserping_error        = 1,
  72         .timeout_ns             = 15500000,     /* 2 meters plus error codes */
  73 };
  74
  75 static irqreturn_t ping_handle_irq(int irq, void *dev_id)
  76 {
  77         struct iio_dev *indio_dev = dev_id;
  78         struct ping_data *data = iio_priv(indio_dev);
  79         ktime_t now = ktime_get();
  80
  81         if (gpiod_get_value(data->gpiod_ping)) {
  82                 data->ts_rising = now;
  83                 complete(&data->rising);
  84         } else {
  85                 data->ts_falling = now;
  86                 complete(&data->falling);
  87         }
  88
  89         return IRQ_HANDLED;
  90 }
  91
  92 static int ping_read(struct iio_dev *indio_dev)
  93 {
  94         struct ping_data *data = iio_priv(indio_dev);
  95         int ret;
  96         ktime_t ktime_dt;
  97         s64 dt_ns;
  98         u32 time_ns, distance_mm;
  99         struct platform_device *pdev = to_platform_device(data->dev);
 100
 101         /*
 102          * just one read-echo-cycle can take place at a time
 103          * ==> lock against concurrent reading calls
 104          */
 105         mutex_lock(&data->lock);
 106
 107         reinit_completion(&data->rising);
 108         reinit_completion(&data->falling);
 109
 110         gpiod_set_value(data->gpiod_ping, 1);
 111         udelay(data->cfg->trigger_pulse_us);
 112         gpiod_set_value(data->gpiod_ping, 0);
 113
 114         ret = gpiod_direction_input(data->gpiod_ping);
 115         if (ret < 0) {
 116                 mutex_unlock(&data->lock);
 117                 return ret;
 118         }
 119
 120         data->irqnr = gpiod_to_irq(data->gpiod_ping);
 121         if (data->irqnr < 0) {
 122                 dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
 123                 mutex_unlock(&data->lock);
 124                 return data->irqnr;
 125         }
 126
 127         ret = request_irq(data->irqnr, ping_handle_irq,
 128                                 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
 129                                                         pdev->name, indio_dev);
 130         if (ret < 0) {
 131                 dev_err(data->dev, "request_irq: %d\n", ret);
 132                 mutex_unlock(&data->lock);
 133                 return ret;
 134         }
 135
 136         /* it should not take more than 20 ms until echo is rising */
 137         ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
 138         if (ret < 0)
 139                 goto err_reset_direction;
 140         else if (ret == 0) {
 141                 ret = -ETIMEDOUT;
 142                 goto err_reset_direction;
 143         }
 144
 145         /* it cannot take more than 50 ms until echo is falling */
 146         ret = wait_for_completion_killable_timeout(&data->falling, HZ/20);
 147         if (ret < 0)
 148                 goto err_reset_direction;
 149         else if (ret == 0) {
 150                 ret = -ETIMEDOUT;
 151                 goto err_reset_direction;
 152         }
 153
 154         ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
 155
 156         free_irq(data->irqnr, indio_dev);
 157
 158         ret = gpiod_direction_output(data->gpiod_ping, GPIOD_OUT_LOW);
 159         if (ret < 0) {
 160                 mutex_unlock(&data->lock);
 161                 return ret;
 162         }
 163
 164         mutex_unlock(&data->lock);
 165
 166         dt_ns = ktime_to_ns(ktime_dt);
 167         if (dt_ns > data->cfg->timeout_ns) {
 168                 dev_dbg(data->dev, "distance out of range: dt=%lldns\n",
 169                                                                 dt_ns);
 170                 return -EIO;
 171         }
 172
 173         time_ns = dt_ns;
 174
 175         /*
 176          * read error code of laser ping sensor and give users chance to
 177          * figure out error by using dynamic debuggging
 178          */
 179         if (data->cfg->laserping_error) {
 180                 if ((time_ns > 12500000) && (time_ns <= 13500000)) {
 181                         dev_dbg(data->dev, "target too close or to far\n");
 182                         return -EIO;
 183                 }
 184                 if ((time_ns > 13500000) && (time_ns <= 14500000)) {
 185                         dev_dbg(data->dev, "internal sensor error\n");
 186                         return -EIO;
 187                 }
 188                 if ((time_ns > 14500000) && (time_ns <= 15500000)) {
 189                         dev_dbg(data->dev, "internal sensor timeout\n");
 190                         return -EIO;
 191                 }
 192         }
 193
 194         /*
 195          * the speed as function of the temperature is approximately:
 196          *
 197          * speed = 331,5 + 0,6 * Temp
 198          *   with Temp in °C
 199          *   and speed in m/s
 200          *
 201          * use 343,5 m/s as ultrasonic speed at 20 °C here in absence of the
 202          * temperature
 203          *
 204          * therefore:
 205          *             time     343,5     time * 232
 206          * distance = ------ * ------- = ------------
 207          *             10^6         2        1350800
 208          *   with time in ns
 209          *   and distance in mm (one way)
 210          *
 211          * because we limit to 3 meters the multiplication with 232 just
 212          * fits into 32 bit
 213          */
 214         distance_mm = time_ns * 232 / 1350800;
 215
 216         return distance_mm;
 217
 218 err_reset_direction:
 219         free_irq(data->irqnr, indio_dev);
 220         mutex_unlock(&data->lock);
 221
 222         if (gpiod_direction_output(data->gpiod_ping, GPIOD_OUT_LOW))
 223                 dev_dbg(data->dev, "error in gpiod_direction_output\n");
 224         return ret;
 225 }
 226
 227 static int ping_read_raw(struct iio_dev *indio_dev,
 228                             struct iio_chan_spec const *channel, int *val,
 229                             int *val2, long info)
 230 {
 231         int ret;
 232
 233         if (channel->type != IIO_DISTANCE)
 234                 return -EINVAL;
 235
 236         switch (info) {
 237         case IIO_CHAN_INFO_RAW:
 238                 ret = ping_read(indio_dev);
 239                 if (ret < 0)
 240                         return ret;
 241                 *val = ret;
 242                 return IIO_VAL_INT;
 243         case IIO_CHAN_INFO_SCALE:
 244                 /*
 245                  * maximum resolution in datasheet is 1 mm
 246                  * 1 LSB is 1 mm
 247                  */
 248                 *val = 0;
 249                 *val2 = 1000;
 250                 return IIO_VAL_INT_PLUS_MICRO;
 251         default:
 252                 return -EINVAL;
 253         }
 254 }
 255
 256 static const struct iio_info ping_iio_info = {
 257         .read_raw               = ping_read_raw,
 258 };
 259
 260 static const struct iio_chan_spec ping_chan_spec[] = {
 261         {
 262                 .type = IIO_DISTANCE,
 263                 .info_mask_separate =
 264                                 BIT(IIO_CHAN_INFO_RAW) |
 265                                 BIT(IIO_CHAN_INFO_SCALE),
 266         },
 267 };
 268
 269 static const struct of_device_id of_ping_match[] = {
 270         { .compatible = "parallax,ping", .data = &pa_ping_cfg },
 271         { .compatible = "parallax,laserping", .data = &pa_laser_ping_cfg },
 272         {},
 273 };
 274
 275 MODULE_DEVICE_TABLE(of, of_ping_match);
 276
 277 static int ping_probe(struct platform_device *pdev)
 278 {
 279         struct device *dev = &pdev->dev;
 280         struct ping_data *data;
 281         struct iio_dev *indio_dev;
 282
 283         indio_dev = devm_iio_device_alloc(dev, sizeof(struct ping_data));
 284         if (!indio_dev) {
 285                 dev_err(dev, "failed to allocate IIO device\n");
 286                 return -ENOMEM;
 287         }
 288
 289         data = iio_priv(indio_dev);
 290         data->dev = dev;
 291         data->cfg = of_device_get_match_data(dev);
 292
 293         mutex_init(&data->lock);
 294         init_completion(&data->rising);
 295         init_completion(&data->falling);
 296
 297         data->gpiod_ping = devm_gpiod_get(dev, "ping", GPIOD_OUT_LOW);
 298         if (IS_ERR(data->gpiod_ping)) {
 299                 dev_err(dev, "failed to get ping-gpios: err=%ld\n",
 300                                                 PTR_ERR(data->gpiod_ping));
 301                 return PTR_ERR(data->gpiod_ping);
 302         }
 303
 304         if (gpiod_cansleep(data->gpiod_ping)) {
 305                 dev_err(data->dev, "cansleep-GPIOs not supported\n");
 306                 return -ENODEV;
 307         }
 308
 309         platform_set_drvdata(pdev, indio_dev);
 310
 311         indio_dev->name = "ping";
 312         indio_dev->info = &ping_iio_info;
 313         indio_dev->modes = INDIO_DIRECT_MODE;
 314         indio_dev->channels = ping_chan_spec;
 315         indio_dev->num_channels = ARRAY_SIZE(ping_chan_spec);
 316
 317         return devm_iio_device_register(dev, indio_dev);
 318 }
 319
 320 static struct platform_driver ping_driver = {
 321         .probe          = ping_probe,
 322         .driver         = {
 323                 .name           = "ping-gpio",
 324                 .of_match_table = of_ping_match,
 325         },
 326 };
 327
 328 module_platform_driver(ping_driver);
 329
 330 MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
 331 MODULE_DESCRIPTION("PING sensors for distance measuring using one GPIOs");
 332 MODULE_LICENSE("GPL");
 333 MODULE_ALIAS("platform:ping");