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 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 | */ |
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, buf: cmd_init, count: 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, buf: &status, count: 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 | */ |
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(cmp1: difference, cmp2: 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 | */ |
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(table: crc8_table, pdata: raw_data, nbytes: 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 | */ |
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(lock: &data->lock); |
174 | return 0; |
175 | } |
176 | |
177 | res = i2c_master_send(client, buf: cmd_meas, count: sizeof(cmd_meas)); |
178 | if (res < 0) { |
179 | mutex_unlock(lock: &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, buf: raw_data, count: data->meas_size); |
186 | if (res != data->meas_size) { |
187 | mutex_unlock(lock: &data->lock); |
188 | if (res >= 0) |
189 | return -ENODATA; |
190 | return res; |
191 | } |
192 | |
193 | if (data->crc8 && crc8_check(raw_data, count: data->meas_size)) { |
194 | mutex_unlock(lock: &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(lock: &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 | */ |
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 | */ |
233 | static ssize_t aht10_interval_read(struct aht10_data *data, |
234 | long *val) |
235 | { |
236 | *val = ktime_to_ms(kt: data->min_poll_interval); |
237 | return 0; |
238 | } |
239 | |
240 | /** |
241 | * aht10_temperature1_read() - read the temperature in millidegrees |
242 | */ |
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 | */ |
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 | |
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 | |
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 | |
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 | |
332 | static int aht10_probe(struct i2c_client *client) |
333 | { |
334 | const struct i2c_device_id *id = i2c_match_id(id: aht10_id, client); |
335 | enum aht10_variant variant = id->driver_data; |
336 | struct device *device = &client->dev; |
337 | struct device *hwmon_dev; |
338 | struct aht10_data *data; |
339 | int res; |
340 | |
341 | if (!i2c_check_functionality(adap: client->adapter, I2C_FUNC_I2C)) |
342 | return -ENOENT; |
343 | |
344 | data = devm_kzalloc(dev: device, size: sizeof(*data), GFP_KERNEL); |
345 | if (!data) |
346 | return -ENOMEM; |
347 | |
348 | data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); |
349 | data->client = client; |
350 | |
351 | switch (variant) { |
352 | case aht20: |
353 | data->meas_size = AHT20_MEAS_SIZE; |
354 | data->crc8 = true; |
355 | crc8_populate_msb(table: crc8_table, AHT20_CRC8_POLY); |
356 | break; |
357 | default: |
358 | data->meas_size = AHT10_MEAS_SIZE; |
359 | break; |
360 | } |
361 | |
362 | mutex_init(&data->lock); |
363 | |
364 | res = aht10_init(data); |
365 | if (res < 0) |
366 | return res; |
367 | |
368 | res = aht10_read_values(data); |
369 | if (res < 0) |
370 | return res; |
371 | |
372 | hwmon_dev = devm_hwmon_device_register_with_info(dev: device, |
373 | name: client->name, |
374 | drvdata: data, |
375 | info: &aht10_chip_info, |
376 | NULL); |
377 | |
378 | return PTR_ERR_OR_ZERO(ptr: hwmon_dev); |
379 | } |
380 | |
381 | static struct i2c_driver aht10_driver = { |
382 | .driver = { |
383 | .name = "aht10" , |
384 | }, |
385 | .probe = aht10_probe, |
386 | .id_table = aht10_id, |
387 | }; |
388 | |
389 | module_i2c_driver(aht10_driver); |
390 | |
391 | MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>" ); |
392 | MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver" ); |
393 | MODULE_VERSION("1.0" ); |
394 | MODULE_LICENSE("GPL v2" ); |
395 | |