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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * PING: ultrasonic sensor for distance measuring by using only one GPIOs4 *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.pdf9 * http://parallax.com/sites/default/files/downloads/28015-PING-Documentation-v1.6.pdf10 *11 * the measurement cycle as timing diagram looks like:12 *13 * GPIO ___ ________________________14 * ping: __/ \____________/ \________________15 * ^ ^ ^ ^16 * |<->| interrupt interrupt17 * udelay(5) (ts_rising) (ts_falling)18 * |<---------------------->|19 * . pulse time measured .20 * . --> one round trip of ultra sonic waves21 * 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/mod_devicetable.h>33#include <linux/module.h>34#include <linux/platform_device.h>35#include <linux/property.h>36#include <linux/sched.h>37#include <linux/interrupt.h>38#include <linux/delay.h>39#include <linux/iio/iio.h>40#include <linux/iio/sysfs.h>41 42struct ping_cfg {43 unsigned long trigger_pulse_us; /* length of trigger pulse */44 int laserping_error; /* support error code in */45 /* pulse width of laser */46 /* ping sensors */47 s64 timeout_ns; /* timeout in ns */48};49 50struct ping_data {51 struct device *dev;52 struct gpio_desc *gpiod_ping;53 struct mutex lock;54 int irqnr;55 ktime_t ts_rising;56 ktime_t ts_falling;57 struct completion rising;58 struct completion falling;59 const struct ping_cfg *cfg;60};61 62static const struct ping_cfg pa_ping_cfg = {63 .trigger_pulse_us = 5,64 .laserping_error = 0,65 .timeout_ns = 18500000, /* 3 meters */66};67 68static const struct ping_cfg pa_laser_ping_cfg = {69 .trigger_pulse_us = 5,70 .laserping_error = 1,71 .timeout_ns = 15500000, /* 2 meters plus error codes */72};73 74static irqreturn_t ping_handle_irq(int irq, void *dev_id)75{76 struct iio_dev *indio_dev = dev_id;77 struct ping_data *data = iio_priv(indio_dev);78 ktime_t now = ktime_get();79 80 if (gpiod_get_value(data->gpiod_ping)) {81 data->ts_rising = now;82 complete(&data->rising);83 } else {84 data->ts_falling = now;85 complete(&data->falling);86 }87 88 return IRQ_HANDLED;89}90 91static int ping_read(struct iio_dev *indio_dev)92{93 struct ping_data *data = iio_priv(indio_dev);94 int ret;95 ktime_t ktime_dt;96 s64 dt_ns;97 u32 time_ns, distance_mm;98 struct platform_device *pdev = to_platform_device(data->dev);99 100 /*101 * just one read-echo-cycle can take place at a time102 * ==> lock against concurrent reading calls103 */104 mutex_lock(&data->lock);105 106 reinit_completion(&data->rising);107 reinit_completion(&data->falling);108 109 gpiod_set_value(data->gpiod_ping, 1);110 udelay(data->cfg->trigger_pulse_us);111 gpiod_set_value(data->gpiod_ping, 0);112 113 ret = gpiod_direction_input(data->gpiod_ping);114 if (ret < 0) {115 mutex_unlock(&data->lock);116 return ret;117 }118 119 data->irqnr = gpiod_to_irq(data->gpiod_ping);120 if (data->irqnr < 0) {121 dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);122 mutex_unlock(&data->lock);123 return data->irqnr;124 }125 126 ret = request_irq(data->irqnr, ping_handle_irq,127 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,128 pdev->name, indio_dev);129 if (ret < 0) {130 dev_err(data->dev, "request_irq: %d\n", ret);131 mutex_unlock(&data->lock);132 return ret;133 }134 135 /* it should not take more than 20 ms until echo is rising */136 ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);137 if (ret < 0)138 goto err_reset_direction;139 else if (ret == 0) {140 ret = -ETIMEDOUT;141 goto err_reset_direction;142 }143 144 /* it cannot take more than 50 ms until echo is falling */145 ret = wait_for_completion_killable_timeout(&data->falling, HZ/20);146 if (ret < 0)147 goto err_reset_direction;148 else if (ret == 0) {149 ret = -ETIMEDOUT;150 goto err_reset_direction;151 }152 153 ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);154 155 free_irq(data->irqnr, indio_dev);156 157 ret = gpiod_direction_output(data->gpiod_ping, GPIOD_OUT_LOW);158 if (ret < 0) {159 mutex_unlock(&data->lock);160 return ret;161 }162 163 mutex_unlock(&data->lock);164 165 dt_ns = ktime_to_ns(ktime_dt);166 if (dt_ns > data->cfg->timeout_ns) {167 dev_dbg(data->dev, "distance out of range: dt=%lldns\n",168 dt_ns);169 return -EIO;170 }171 172 time_ns = dt_ns;173 174 /*175 * read error code of laser ping sensor and give users chance to176 * figure out error by using dynamic debugging177 */178 if (data->cfg->laserping_error) {179 if ((time_ns > 12500000) && (time_ns <= 13500000)) {180 dev_dbg(data->dev, "target too close or to far\n");181 return -EIO;182 }183 if ((time_ns > 13500000) && (time_ns <= 14500000)) {184 dev_dbg(data->dev, "internal sensor error\n");185 return -EIO;186 }187 if ((time_ns > 14500000) && (time_ns <= 15500000)) {188 dev_dbg(data->dev, "internal sensor timeout\n");189 return -EIO;190 }191 }192 193 /*194 * the speed as function of the temperature is approximately:195 *196 * speed = 331,5 + 0,6 * Temp197 * with Temp in °C198 * and speed in m/s199 *200 * use 343,5 m/s as ultrasonic speed at 20 °C here in absence of the201 * temperature202 *203 * therefore:204 * time 343,5 time * 232205 * distance = ------ * ------- = ------------206 * 10^6 2 1350800207 * with time in ns208 * and distance in mm (one way)209 *210 * because we limit to 3 meters the multiplication with 232 just211 * fits into 32 bit212 */213 distance_mm = time_ns * 232 / 1350800;214 215 return distance_mm;216 217err_reset_direction:218 free_irq(data->irqnr, indio_dev);219 mutex_unlock(&data->lock);220 221 if (gpiod_direction_output(data->gpiod_ping, GPIOD_OUT_LOW))222 dev_dbg(data->dev, "error in gpiod_direction_output\n");223 return ret;224}225 226static int ping_read_raw(struct iio_dev *indio_dev,227 struct iio_chan_spec const *channel, int *val,228 int *val2, long info)229{230 int ret;231 232 if (channel->type != IIO_DISTANCE)233 return -EINVAL;234 235 switch (info) {236 case IIO_CHAN_INFO_RAW:237 ret = ping_read(indio_dev);238 if (ret < 0)239 return ret;240 *val = ret;241 return IIO_VAL_INT;242 case IIO_CHAN_INFO_SCALE:243 /*244 * maximum resolution in datasheet is 1 mm245 * 1 LSB is 1 mm246 */247 *val = 0;248 *val2 = 1000;249 return IIO_VAL_INT_PLUS_MICRO;250 default:251 return -EINVAL;252 }253}254 255static const struct iio_info ping_iio_info = {256 .read_raw = ping_read_raw,257};258 259static const struct iio_chan_spec ping_chan_spec[] = {260 {261 .type = IIO_DISTANCE,262 .info_mask_separate =263 BIT(IIO_CHAN_INFO_RAW) |264 BIT(IIO_CHAN_INFO_SCALE),265 },266};267 268static const struct of_device_id of_ping_match[] = {269 { .compatible = "parallax,ping", .data = &pa_ping_cfg },270 { .compatible = "parallax,laserping", .data = &pa_laser_ping_cfg },271 {},272};273 274MODULE_DEVICE_TABLE(of, of_ping_match);275 276static int ping_probe(struct platform_device *pdev)277{278 struct device *dev = &pdev->dev;279 struct ping_data *data;280 struct iio_dev *indio_dev;281 282 indio_dev = devm_iio_device_alloc(dev, sizeof(struct ping_data));283 if (!indio_dev) {284 dev_err(dev, "failed to allocate IIO device\n");285 return -ENOMEM;286 }287 288 data = iio_priv(indio_dev);289 data->dev = dev;290 data->cfg = device_get_match_data(dev);291 292 mutex_init(&data->lock);293 init_completion(&data->rising);294 init_completion(&data->falling);295 296 data->gpiod_ping = devm_gpiod_get(dev, "ping", GPIOD_OUT_LOW);297 if (IS_ERR(data->gpiod_ping)) {298 dev_err(dev, "failed to get ping-gpios: err=%ld\n",299 PTR_ERR(data->gpiod_ping));300 return PTR_ERR(data->gpiod_ping);301 }302 303 if (gpiod_cansleep(data->gpiod_ping)) {304 dev_err(data->dev, "cansleep-GPIOs not supported\n");305 return -ENODEV;306 }307 308 platform_set_drvdata(pdev, indio_dev);309 310 indio_dev->name = "ping";311 indio_dev->info = &ping_iio_info;312 indio_dev->modes = INDIO_DIRECT_MODE;313 indio_dev->channels = ping_chan_spec;314 indio_dev->num_channels = ARRAY_SIZE(ping_chan_spec);315 316 return devm_iio_device_register(dev, indio_dev);317}318 319static struct platform_driver ping_driver = {320 .probe = ping_probe,321 .driver = {322 .name = "ping-gpio",323 .of_match_table = of_ping_match,324 },325};326 327module_platform_driver(ping_driver);328 329MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");330MODULE_DESCRIPTION("PING sensors for distance measuring using one GPIOs");331MODULE_LICENSE("GPL");332MODULE_ALIAS("platform:ping");333