xref: /linux/drivers/hwmon/aht10.c (revision a1ff5a7d78a036d6c2178ee5acd6ba4946243800)
1 // SPDX-License-Identifier: GPL-2.0-only
2 
3 /*
4  * aht10.c - Linux hwmon driver for AHT10/AHT20 Temperature and Humidity sensors
5  * Copyright (C) 2020 Johannes Cornelis Draaijer
6  */
7 
8 #include <linux/delay.h>
9 #include <linux/hwmon.h>
10 #include <linux/i2c.h>
11 #include <linux/ktime.h>
12 #include <linux/module.h>
13 #include <linux/crc8.h>
14 
15 #define AHT10_MEAS_SIZE		6
16 
17 #define AHT20_MEAS_SIZE		7
18 #define AHT20_CRC8_POLY		0x31
19 
20 /*
21  * Poll intervals (in milliseconds)
22  */
23 #define AHT10_DEFAULT_MIN_POLL_INTERVAL	2000
24 #define AHT10_MIN_POLL_INTERVAL		2000
25 
26 /*
27  * I2C command delays (in microseconds)
28  */
29 #define AHT10_MEAS_DELAY	80000
30 #define AHT10_CMD_DELAY		350000
31 #define AHT10_DELAY_EXTRA	100000
32 
33 /*
34  * Command bytes
35  */
36 #define AHT10_CMD_INIT	0b11100001
37 #define AHT10_CMD_MEAS	0b10101100
38 #define AHT10_CMD_RST	0b10111010
39 
40 /*
41  * Flags in the answer byte/command
42  */
43 #define AHT10_CAL_ENABLED	BIT(3)
44 #define AHT10_BUSY		BIT(7)
45 #define AHT10_MODE_NOR		(BIT(5) | BIT(6))
46 #define AHT10_MODE_CYC		BIT(5)
47 #define AHT10_MODE_CMD		BIT(6)
48 
49 #define AHT10_MAX_POLL_INTERVAL_LEN	30
50 
51 enum aht10_variant { aht10, aht20 };
52 
53 static const struct i2c_device_id aht10_id[] = {
54 	{ "aht10", aht10 },
55 	{ "aht20", aht20 },
56 	{ },
57 };
58 MODULE_DEVICE_TABLE(i2c, aht10_id);
59 
60 /**
61  *   struct aht10_data - All the data required to operate an AHT10/AHT20 chip
62  *   @client: the i2c client associated with the AHT10/AHT20
63  *   @lock: a mutex that is used to prevent parallel access to the
64  *          i2c client
65  *   @min_poll_interval: the minimum poll interval
66  *                   While the poll rate limit is not 100% necessary,
67  *                   the datasheet recommends that a measurement
68  *                   is not performed too often to prevent
69  *                   the chip from warming up due to the heat it generates.
70  *                   If it's unwanted, it can be ignored setting it to
71  *                   it to 0. Default value is 2000 ms
72  *   @previous_poll_time: the previous time that the AHT10/AHT20
73  *                        was polled
74  *   @temperature: the latest temperature value received from
75  *                 the AHT10/AHT20
76  *   @humidity: the latest humidity value received from the
77  *              AHT10/AHT20
78  *   @crc8: crc8 support flag
79  *   @meas_size: measurements data size
80  */
81 
82 struct aht10_data {
83 	struct i2c_client *client;
84 	/*
85 	 * Prevent simultaneous access to the i2c
86 	 * client and previous_poll_time
87 	 */
88 	struct mutex lock;
89 	ktime_t min_poll_interval;
90 	ktime_t previous_poll_time;
91 	int temperature;
92 	int humidity;
93 	bool crc8;
94 	unsigned int meas_size;
95 };
96 
97 /**
98  * aht10_init() - Initialize an AHT10/AHT20 chip
99  * @data: the data associated with this AHT10/AHT20 chip
100  * Return: 0 if successful, 1 if not
101  */
aht10_init(struct aht10_data * data)102 static int aht10_init(struct aht10_data *data)
103 {
104 	const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC,
105 			       0x00};
106 	int res;
107 	u8 status;
108 	struct i2c_client *client = data->client;
109 
110 	res = i2c_master_send(client, cmd_init, 3);
111 	if (res < 0)
112 		return res;
113 
114 	usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY +
115 		     AHT10_DELAY_EXTRA);
116 
117 	res = i2c_master_recv(client, &status, 1);
118 	if (res != 1)
119 		return -ENODATA;
120 
121 	if (status & AHT10_BUSY)
122 		return -EBUSY;
123 
124 	return 0;
125 }
126 
127 /**
128  * aht10_polltime_expired() - check if the minimum poll interval has
129  *                                  expired
130  * @data: the data containing the time to compare
131  * Return: 1 if the minimum poll interval has expired, 0 if not
132  */
aht10_polltime_expired(struct aht10_data * data)133 static int aht10_polltime_expired(struct aht10_data *data)
134 {
135 	ktime_t current_time = ktime_get_boottime();
136 	ktime_t difference = ktime_sub(current_time, data->previous_poll_time);
137 
138 	return ktime_after(difference, data->min_poll_interval);
139 }
140 
141 DECLARE_CRC8_TABLE(crc8_table);
142 
143 /**
144  * crc8_check() - check crc of the sensor's measurements
145  * @raw_data: data frame received from sensor(including crc as the last byte)
146  * @count: size of the data frame
147  * Return: 0 if successful, 1 if not
148  */
crc8_check(u8 * raw_data,int count)149 static int crc8_check(u8 *raw_data, int count)
150 {
151 	/*
152 	 * crc calculated on the whole frame(including crc byte) should yield
153 	 * zero in case of correctly received bytes
154 	 */
155 	return crc8(crc8_table, raw_data, count, CRC8_INIT_VALUE);
156 }
157 
158 /**
159  * aht10_read_values() - read and parse the raw data from the AHT10/AHT20
160  * @data: the struct aht10_data to use for the lock
161  * Return: 0 if successful, 1 if not
162  */
aht10_read_values(struct aht10_data * data)163 static int aht10_read_values(struct aht10_data *data)
164 {
165 	const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00};
166 	u32 temp, hum;
167 	int res;
168 	u8 raw_data[AHT20_MEAS_SIZE];
169 	struct i2c_client *client = data->client;
170 
171 	mutex_lock(&data->lock);
172 	if (!aht10_polltime_expired(data)) {
173 		mutex_unlock(&data->lock);
174 		return 0;
175 	}
176 
177 	res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas));
178 	if (res < 0) {
179 		mutex_unlock(&data->lock);
180 		return res;
181 	}
182 
183 	usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA);
184 
185 	res = i2c_master_recv(client, raw_data, data->meas_size);
186 	if (res != data->meas_size) {
187 		mutex_unlock(&data->lock);
188 		if (res >= 0)
189 			return -ENODATA;
190 		return res;
191 	}
192 
193 	if (data->crc8 && crc8_check(raw_data, data->meas_size)) {
194 		mutex_unlock(&data->lock);
195 		return -EIO;
196 	}
197 
198 	hum =   ((u32)raw_data[1] << 12u) |
199 		((u32)raw_data[2] << 4u) |
200 		((raw_data[3] & 0xF0u) >> 4u);
201 
202 	temp =  ((u32)(raw_data[3] & 0x0Fu) << 16u) |
203 		((u32)raw_data[4] << 8u) |
204 		raw_data[5];
205 
206 	temp = ((temp * 625) >> 15u) * 10;
207 	hum = ((hum * 625) >> 16u) * 10;
208 
209 	data->temperature = (int)temp - 50000;
210 	data->humidity = hum;
211 	data->previous_poll_time = ktime_get_boottime();
212 
213 	mutex_unlock(&data->lock);
214 	return 0;
215 }
216 
217 /**
218  * aht10_interval_write() - store the given minimum poll interval.
219  * Return: 0 on success, -EINVAL if a value lower than the
220  *         AHT10_MIN_POLL_INTERVAL is given
221  */
aht10_interval_write(struct aht10_data * data,long val)222 static ssize_t aht10_interval_write(struct aht10_data *data,
223 				    long val)
224 {
225 	data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX));
226 	return 0;
227 }
228 
229 /**
230  * aht10_interval_read() - read the minimum poll interval
231  *                            in milliseconds
232  */
aht10_interval_read(struct aht10_data * data,long * val)233 static ssize_t aht10_interval_read(struct aht10_data *data,
234 				   long *val)
235 {
236 	*val = ktime_to_ms(data->min_poll_interval);
237 	return 0;
238 }
239 
240 /**
241  * aht10_temperature1_read() - read the temperature in millidegrees
242  */
aht10_temperature1_read(struct aht10_data * data,long * val)243 static int aht10_temperature1_read(struct aht10_data *data, long *val)
244 {
245 	int res;
246 
247 	res = aht10_read_values(data);
248 	if (res < 0)
249 		return res;
250 
251 	*val = data->temperature;
252 	return 0;
253 }
254 
255 /**
256  * aht10_humidity1_read() - read the relative humidity in millipercent
257  */
aht10_humidity1_read(struct aht10_data * data,long * val)258 static int aht10_humidity1_read(struct aht10_data *data, long *val)
259 {
260 	int res;
261 
262 	res = aht10_read_values(data);
263 	if (res < 0)
264 		return res;
265 
266 	*val = data->humidity;
267 	return 0;
268 }
269 
aht10_hwmon_visible(const void * data,enum hwmon_sensor_types type,u32 attr,int channel)270 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type,
271 				   u32 attr, int channel)
272 {
273 	switch (type) {
274 	case hwmon_temp:
275 	case hwmon_humidity:
276 		return 0444;
277 	case hwmon_chip:
278 		return 0644;
279 	default:
280 		return 0;
281 	}
282 }
283 
aht10_hwmon_read(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long * val)284 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
285 			    u32 attr, int channel, long *val)
286 {
287 	struct aht10_data *data = dev_get_drvdata(dev);
288 
289 	switch (type) {
290 	case hwmon_temp:
291 		return aht10_temperature1_read(data, val);
292 	case hwmon_humidity:
293 		return aht10_humidity1_read(data, val);
294 	case hwmon_chip:
295 		return aht10_interval_read(data, val);
296 	default:
297 		return -EOPNOTSUPP;
298 	}
299 }
300 
aht10_hwmon_write(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long val)301 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
302 			     u32 attr, int channel, long val)
303 {
304 	struct aht10_data *data = dev_get_drvdata(dev);
305 
306 	switch (type) {
307 	case hwmon_chip:
308 		return aht10_interval_write(data, val);
309 	default:
310 		return -EOPNOTSUPP;
311 	}
312 }
313 
314 static const struct hwmon_channel_info * const aht10_info[] = {
315 	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
316 	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
317 	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
318 	NULL,
319 };
320 
321 static const struct hwmon_ops aht10_hwmon_ops = {
322 	.is_visible = aht10_hwmon_visible,
323 	.read = aht10_hwmon_read,
324 	.write = aht10_hwmon_write,
325 };
326 
327 static const struct hwmon_chip_info aht10_chip_info = {
328 	.ops = &aht10_hwmon_ops,
329 	.info = aht10_info,
330 };
331 
aht10_probe(struct i2c_client * client)332 static int aht10_probe(struct i2c_client *client)
333 {
334 	enum aht10_variant variant = (uintptr_t)i2c_get_match_data(client);
335 	struct device *device = &client->dev;
336 	struct device *hwmon_dev;
337 	struct aht10_data *data;
338 	int res;
339 
340 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
341 		return -ENOENT;
342 
343 	data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
344 	if (!data)
345 		return -ENOMEM;
346 
347 	data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL);
348 	data->client = client;
349 
350 	switch (variant) {
351 	case aht20:
352 		data->meas_size = AHT20_MEAS_SIZE;
353 		data->crc8 = true;
354 		crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
355 		break;
356 	default:
357 		data->meas_size = AHT10_MEAS_SIZE;
358 		break;
359 	}
360 
361 	mutex_init(&data->lock);
362 
363 	res = aht10_init(data);
364 	if (res < 0)
365 		return res;
366 
367 	res = aht10_read_values(data);
368 	if (res < 0)
369 		return res;
370 
371 	hwmon_dev = devm_hwmon_device_register_with_info(device,
372 							 client->name,
373 							 data,
374 							 &aht10_chip_info,
375 							 NULL);
376 
377 	return PTR_ERR_OR_ZERO(hwmon_dev);
378 }
379 
380 static struct i2c_driver aht10_driver = {
381 	.driver = {
382 		.name = "aht10",
383 	},
384 	.probe      = aht10_probe,
385 	.id_table   = aht10_id,
386 };
387 
388 module_i2c_driver(aht10_driver);
389 
390 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
391 MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
392 MODULE_VERSION("1.0");
393 MODULE_LICENSE("GPL v2");
394