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
ping_handle_irq(int irq,void * dev_id)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
ping_read(struct iio_dev * indio_dev)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
ping_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * channel,int * val,int * val2,long info)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
ping_probe(struct platform_device * pdev)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");
334