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 | |
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(desc: 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 | |
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(x: &data->rising); |
107 | reinit_completion(x: &data->falling); |
108 | |
109 | gpiod_set_value(desc: data->gpiod_ping, value: 1); |
110 | udelay(data->cfg->trigger_pulse_us); |
111 | gpiod_set_value(desc: data->gpiod_ping, value: 0); |
112 | |
113 | ret = gpiod_direction_input(desc: data->gpiod_ping); |
114 | if (ret < 0) { |
115 | mutex_unlock(lock: &data->lock); |
116 | return ret; |
117 | } |
118 | |
119 | data->irqnr = gpiod_to_irq(desc: data->gpiod_ping); |
120 | if (data->irqnr < 0) { |
121 | dev_err(data->dev, "gpiod_to_irq: %d\n" , data->irqnr); |
122 | mutex_unlock(lock: &data->lock); |
123 | return data->irqnr; |
124 | } |
125 | |
126 | ret = request_irq(irq: data->irqnr, handler: ping_handle_irq, |
127 | IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, |
128 | name: pdev->name, dev: indio_dev); |
129 | if (ret < 0) { |
130 | dev_err(data->dev, "request_irq: %d\n" , ret); |
131 | mutex_unlock(lock: &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(x: &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(x: &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(desc: data->gpiod_ping, value: GPIOD_OUT_LOW); |
158 | if (ret < 0) { |
159 | mutex_unlock(lock: &data->lock); |
160 | return ret; |
161 | } |
162 | |
163 | mutex_unlock(lock: &data->lock); |
164 | |
165 | dt_ns = ktime_to_ns(kt: 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(lock: &data->lock); |
220 | |
221 | if (gpiod_direction_output(desc: data->gpiod_ping, value: GPIOD_OUT_LOW)) |
222 | dev_dbg(data->dev, "error in gpiod_direction_output\n" ); |
223 | return ret; |
224 | } |
225 | |
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 | |
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(parent: dev, sizeof_priv: 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(x: &data->rising); |
294 | init_completion(x: &data->falling); |
295 | |
296 | data->gpiod_ping = devm_gpiod_get(dev, con_id: "ping" , flags: GPIOD_OUT_LOW); |
297 | if (IS_ERR(ptr: 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(ptr: data->gpiod_ping); |
301 | } |
302 | |
303 | if (gpiod_cansleep(desc: data->gpiod_ping)) { |
304 | dev_err(data->dev, "cansleep-GPIOs not supported\n" ); |
305 | return -ENODEV; |
306 | } |
307 | |
308 | platform_set_drvdata(pdev, data: 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 | |