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/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
42 struct 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
50 struct 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
62 static const struct ping_cfg pa_ping_cfg = {
63 .trigger_pulse_us = 5,
64 .laserping_error = 0,
65 .timeout_ns = 18500000, /* 3 meters */
66 };
67
68 static 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
ping_handle_irq(int irq,void * dev_id)74 static 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
ping_read(struct iio_dev * indio_dev)91 static 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 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_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 to
176 * figure out error by using dynamic debugging
177 */
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 * Temp
197 * with Temp in °C
198 * and speed in m/s
199 *
200 * use 343,5 m/s as ultrasonic speed at 20 °C here in absence of the
201 * temperature
202 *
203 * therefore:
204 * time 343,5 time * 232
205 * distance = ------ * ------- = ------------
206 * 10^6 2 1350800
207 * with time in ns
208 * and distance in mm (one way)
209 *
210 * because we limit to 3 meters the multiplication with 232 just
211 * fits into 32 bit
212 */
213 distance_mm = time_ns * 232 / 1350800;
214
215 return distance_mm;
216
217 err_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
ping_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * channel,int * val,int * val2,long info)226 static 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 mm
245 * 1 LSB is 1 mm
246 */
247 *val = 0;
248 *val2 = 1000;
249 return IIO_VAL_INT_PLUS_MICRO;
250 default:
251 return -EINVAL;
252 }
253 }
254
255 static const struct iio_info ping_iio_info = {
256 .read_raw = ping_read_raw,
257 };
258
259 static 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
268 static 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
274 MODULE_DEVICE_TABLE(of, of_ping_match);
275
ping_probe(struct platform_device * pdev)276 static 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
319 static 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
327 module_platform_driver(ping_driver);
328
329 MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
330 MODULE_DESCRIPTION("PING sensors for distance measuring using one GPIOs");
331 MODULE_LICENSE("GPL");
332 MODULE_ALIAS("platform:ping");
333