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 * https://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/mod_devicetable.h>
41 #include <linux/module.h>
42 #include <linux/platform_device.h>
43 #include <linux/property.h>
44 #include <linux/sched.h>
45 #include <linux/interrupt.h>
46 #include <linux/delay.h>
47 #include <linux/pm_runtime.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 gpio_desc *gpiod_power;
60 struct mutex lock;
61 int irqnr;
62 ktime_t ts_rising;
63 ktime_t ts_falling;
64 struct completion rising;
65 struct completion falling;
66 const struct srf04_cfg *cfg;
67 int startup_time_ms;
68 };
69
70 static const struct srf04_cfg srf04_cfg = {
71 .trigger_pulse_us = 10,
72 };
73
74 static const struct srf04_cfg mb_lv_cfg = {
75 .trigger_pulse_us = 20,
76 };
77
srf04_handle_irq(int irq,void * dev_id)78 static irqreturn_t srf04_handle_irq(int irq, void *dev_id)
79 {
80 struct iio_dev *indio_dev = dev_id;
81 struct srf04_data *data = iio_priv(indio_dev);
82 ktime_t now = ktime_get();
83
84 if (gpiod_get_value(data->gpiod_echo)) {
85 data->ts_rising = now;
86 complete(&data->rising);
87 } else {
88 data->ts_falling = now;
89 complete(&data->falling);
90 }
91
92 return IRQ_HANDLED;
93 }
94
srf04_read(struct srf04_data * data)95 static int srf04_read(struct srf04_data *data)
96 {
97 int ret;
98 ktime_t ktime_dt;
99 u64 dt_ns;
100 u32 time_ns, distance_mm;
101
102 if (data->gpiod_power) {
103 ret = pm_runtime_resume_and_get(data->dev);
104 if (ret < 0)
105 return ret;
106 }
107 /*
108 * just one read-echo-cycle can take place at a time
109 * ==> lock against concurrent reading calls
110 */
111 mutex_lock(&data->lock);
112
113 reinit_completion(&data->rising);
114 reinit_completion(&data->falling);
115
116 gpiod_set_value(data->gpiod_trig, 1);
117 udelay(data->cfg->trigger_pulse_us);
118 gpiod_set_value(data->gpiod_trig, 0);
119
120 if (data->gpiod_power) {
121 pm_runtime_mark_last_busy(data->dev);
122 pm_runtime_put_autosuspend(data->dev);
123 }
124
125 /* it should not take more than 20 ms until echo is rising */
126 ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
127 if (ret < 0) {
128 mutex_unlock(&data->lock);
129 return ret;
130 } else if (ret == 0) {
131 mutex_unlock(&data->lock);
132 return -ETIMEDOUT;
133 }
134
135 /* it cannot take more than 50 ms until echo is falling */
136 ret = wait_for_completion_killable_timeout(&data->falling, HZ/20);
137 if (ret < 0) {
138 mutex_unlock(&data->lock);
139 return ret;
140 } else if (ret == 0) {
141 mutex_unlock(&data->lock);
142 return -ETIMEDOUT;
143 }
144
145 ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
146
147 mutex_unlock(&data->lock);
148
149 dt_ns = ktime_to_ns(ktime_dt);
150 /*
151 * measuring more than 6,45 meters is beyond the capabilities of
152 * the supported sensors
153 * ==> filter out invalid results for not measuring echos of
154 * another us sensor
155 *
156 * formula:
157 * distance 6,45 * 2 m
158 * time = ---------- = ------------ = 40438871 ns
159 * speed 319 m/s
160 *
161 * using a minimum speed at -20 °C of 319 m/s
162 */
163 if (dt_ns > 40438871)
164 return -EIO;
165
166 time_ns = dt_ns;
167
168 /*
169 * the speed as function of the temperature is approximately:
170 *
171 * speed = 331,5 + 0,6 * Temp
172 * with Temp in °C
173 * and speed in m/s
174 *
175 * use 343,5 m/s as ultrasonic speed at 20 °C here in absence of the
176 * temperature
177 *
178 * therefore:
179 * time 343,5 time * 106
180 * distance = ------ * ------- = ------------
181 * 10^6 2 617176
182 * with time in ns
183 * and distance in mm (one way)
184 *
185 * because we limit to 6,45 meters the multiplication with 106 just
186 * fits into 32 bit
187 */
188 distance_mm = time_ns * 106 / 617176;
189
190 return distance_mm;
191 }
192
srf04_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * channel,int * val,int * val2,long info)193 static int srf04_read_raw(struct iio_dev *indio_dev,
194 struct iio_chan_spec const *channel, int *val,
195 int *val2, long info)
196 {
197 struct srf04_data *data = iio_priv(indio_dev);
198 int ret;
199
200 if (channel->type != IIO_DISTANCE)
201 return -EINVAL;
202
203 switch (info) {
204 case IIO_CHAN_INFO_RAW:
205 ret = srf04_read(data);
206 if (ret < 0)
207 return ret;
208 *val = ret;
209 return IIO_VAL_INT;
210 case IIO_CHAN_INFO_SCALE:
211 /*
212 * theoretical maximum resolution is 3 mm
213 * 1 LSB is 1 mm
214 */
215 *val = 0;
216 *val2 = 1000;
217 return IIO_VAL_INT_PLUS_MICRO;
218 default:
219 return -EINVAL;
220 }
221 }
222
223 static const struct iio_info srf04_iio_info = {
224 .read_raw = srf04_read_raw,
225 };
226
227 static const struct iio_chan_spec srf04_chan_spec[] = {
228 {
229 .type = IIO_DISTANCE,
230 .info_mask_separate =
231 BIT(IIO_CHAN_INFO_RAW) |
232 BIT(IIO_CHAN_INFO_SCALE),
233 },
234 };
235
236 static const struct of_device_id of_srf04_match[] = {
237 { .compatible = "devantech,srf04", .data = &srf04_cfg },
238 { .compatible = "maxbotix,mb1000", .data = &mb_lv_cfg },
239 { .compatible = "maxbotix,mb1010", .data = &mb_lv_cfg },
240 { .compatible = "maxbotix,mb1020", .data = &mb_lv_cfg },
241 { .compatible = "maxbotix,mb1030", .data = &mb_lv_cfg },
242 { .compatible = "maxbotix,mb1040", .data = &mb_lv_cfg },
243 {},
244 };
245
246 MODULE_DEVICE_TABLE(of, of_srf04_match);
247
srf04_probe(struct platform_device * pdev)248 static int srf04_probe(struct platform_device *pdev)
249 {
250 struct device *dev = &pdev->dev;
251 struct srf04_data *data;
252 struct iio_dev *indio_dev;
253 int ret;
254
255 indio_dev = devm_iio_device_alloc(dev, sizeof(struct srf04_data));
256 if (!indio_dev) {
257 dev_err(dev, "failed to allocate IIO device\n");
258 return -ENOMEM;
259 }
260
261 data = iio_priv(indio_dev);
262 data->dev = dev;
263 data->cfg = device_get_match_data(dev);
264
265 mutex_init(&data->lock);
266 init_completion(&data->rising);
267 init_completion(&data->falling);
268
269 data->gpiod_trig = devm_gpiod_get(dev, "trig", GPIOD_OUT_LOW);
270 if (IS_ERR(data->gpiod_trig)) {
271 dev_err(dev, "failed to get trig-gpios: err=%ld\n",
272 PTR_ERR(data->gpiod_trig));
273 return PTR_ERR(data->gpiod_trig);
274 }
275
276 data->gpiod_echo = devm_gpiod_get(dev, "echo", GPIOD_IN);
277 if (IS_ERR(data->gpiod_echo)) {
278 dev_err(dev, "failed to get echo-gpios: err=%ld\n",
279 PTR_ERR(data->gpiod_echo));
280 return PTR_ERR(data->gpiod_echo);
281 }
282
283 data->gpiod_power = devm_gpiod_get_optional(dev, "power",
284 GPIOD_OUT_LOW);
285 if (IS_ERR(data->gpiod_power)) {
286 dev_err(dev, "failed to get power-gpios: err=%ld\n",
287 PTR_ERR(data->gpiod_power));
288 return PTR_ERR(data->gpiod_power);
289 }
290 if (data->gpiod_power) {
291 data->startup_time_ms = 100;
292 device_property_read_u32(dev, "startup-time-ms", &data->startup_time_ms);
293 dev_dbg(dev, "using power gpio: startup-time-ms=%d\n",
294 data->startup_time_ms);
295 }
296
297 if (gpiod_cansleep(data->gpiod_echo)) {
298 dev_err(data->dev, "cansleep-GPIOs not supported\n");
299 return -ENODEV;
300 }
301
302 data->irqnr = gpiod_to_irq(data->gpiod_echo);
303 if (data->irqnr < 0) {
304 dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
305 return data->irqnr;
306 }
307
308 ret = devm_request_irq(dev, data->irqnr, srf04_handle_irq,
309 IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
310 pdev->name, indio_dev);
311 if (ret < 0) {
312 dev_err(data->dev, "request_irq: %d\n", ret);
313 return ret;
314 }
315
316 platform_set_drvdata(pdev, indio_dev);
317
318 indio_dev->name = "srf04";
319 indio_dev->info = &srf04_iio_info;
320 indio_dev->modes = INDIO_DIRECT_MODE;
321 indio_dev->channels = srf04_chan_spec;
322 indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);
323
324 ret = iio_device_register(indio_dev);
325 if (ret < 0) {
326 dev_err(data->dev, "iio_device_register: %d\n", ret);
327 return ret;
328 }
329
330 if (data->gpiod_power) {
331 pm_runtime_set_autosuspend_delay(data->dev, 1000);
332 pm_runtime_use_autosuspend(data->dev);
333
334 ret = pm_runtime_set_active(data->dev);
335 if (ret) {
336 dev_err(data->dev, "pm_runtime_set_active: %d\n", ret);
337 iio_device_unregister(indio_dev);
338 }
339
340 pm_runtime_enable(data->dev);
341 pm_runtime_idle(data->dev);
342 }
343
344 return ret;
345 }
346
srf04_remove(struct platform_device * pdev)347 static int srf04_remove(struct platform_device *pdev)
348 {
349 struct iio_dev *indio_dev = platform_get_drvdata(pdev);
350 struct srf04_data *data = iio_priv(indio_dev);
351
352 iio_device_unregister(indio_dev);
353
354 if (data->gpiod_power) {
355 pm_runtime_disable(data->dev);
356 pm_runtime_set_suspended(data->dev);
357 }
358
359 return 0;
360 }
361
srf04_pm_runtime_suspend(struct device * dev)362 static int srf04_pm_runtime_suspend(struct device *dev)
363 {
364 struct platform_device *pdev = container_of(dev,
365 struct platform_device, dev);
366 struct iio_dev *indio_dev = platform_get_drvdata(pdev);
367 struct srf04_data *data = iio_priv(indio_dev);
368
369 gpiod_set_value(data->gpiod_power, 0);
370
371 return 0;
372 }
373
srf04_pm_runtime_resume(struct device * dev)374 static int srf04_pm_runtime_resume(struct device *dev)
375 {
376 struct platform_device *pdev = container_of(dev,
377 struct platform_device, dev);
378 struct iio_dev *indio_dev = platform_get_drvdata(pdev);
379 struct srf04_data *data = iio_priv(indio_dev);
380
381 gpiod_set_value(data->gpiod_power, 1);
382 msleep(data->startup_time_ms);
383
384 return 0;
385 }
386
387 static const struct dev_pm_ops srf04_pm_ops = {
388 RUNTIME_PM_OPS(srf04_pm_runtime_suspend,
389 srf04_pm_runtime_resume, NULL)
390 };
391
392 static struct platform_driver srf04_driver = {
393 .probe = srf04_probe,
394 .remove = srf04_remove,
395 .driver = {
396 .name = "srf04-gpio",
397 .of_match_table = of_srf04_match,
398 .pm = pm_ptr(&srf04_pm_ops),
399 },
400 };
401
402 module_platform_driver(srf04_driver);
403
404 MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
405 MODULE_DESCRIPTION("SRF04 ultrasonic sensor for distance measuring using GPIOs");
406 MODULE_LICENSE("GPL");
407 MODULE_ALIAS("platform:srf04");
408