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 #define AHT20_CMD_INIT 0b10111110
41
42 #define DHT20_CMD_INIT 0b01110001
43
44 /*
45 * Flags in the answer byte/command
46 */
47 #define AHT10_CAL_ENABLED BIT(3)
48 #define AHT10_BUSY BIT(7)
49 #define AHT10_MODE_NOR (BIT(5) | BIT(6))
50 #define AHT10_MODE_CYC BIT(5)
51 #define AHT10_MODE_CMD BIT(6)
52
53 #define AHT10_MAX_POLL_INTERVAL_LEN 30
54
55 enum aht10_variant { aht10, aht20, dht20};
56
57 static const struct i2c_device_id aht10_id[] = {
58 { "aht10", aht10 },
59 { "aht20", aht20 },
60 { "dht20", dht20 },
61 { },
62 };
63 MODULE_DEVICE_TABLE(i2c, aht10_id);
64
65 /**
66 * struct aht10_data - All the data required to operate an AHT10/AHT20 chip
67 * @client: the i2c client associated with the AHT10/AHT20
68 * @min_poll_interval: the minimum poll interval
69 * While the poll rate limit is not 100% necessary,
70 * the datasheet recommends that a measurement
71 * is not performed too often to prevent
72 * the chip from warming up due to the heat it generates.
73 * If it's unwanted, it can be ignored setting it to
74 * it to 0. Default value is 2000 ms
75 * @previous_poll_time: the previous time that the AHT10/AHT20
76 * was polled
77 * @temperature: the latest temperature value received from
78 * the AHT10/AHT20
79 * @humidity: the latest humidity value received from the
80 * AHT10/AHT20
81 * @crc8: crc8 support flag
82 * @meas_size: measurements data size
83 * @init_cmd: Initialization command
84 */
85
86 struct aht10_data {
87 struct i2c_client *client;
88 ktime_t min_poll_interval;
89 ktime_t previous_poll_time;
90 int temperature;
91 int humidity;
92 bool crc8;
93 unsigned int meas_size;
94 u8 init_cmd;
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[] = {data->init_cmd, 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, sizeof(cmd_init));
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 if (!aht10_polltime_expired(data))
172 return 0;
173
174 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas));
175 if (res < 0)
176 return res;
177
178 usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA);
179
180 res = i2c_master_recv(client, raw_data, data->meas_size);
181 if (res != data->meas_size) {
182 if (res >= 0)
183 return -ENODATA;
184 return res;
185 }
186
187 if (data->crc8 && crc8_check(raw_data, data->meas_size))
188 return -EIO;
189
190 hum = ((u32)raw_data[1] << 12u) |
191 ((u32)raw_data[2] << 4u) |
192 ((raw_data[3] & 0xF0u) >> 4u);
193
194 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) |
195 ((u32)raw_data[4] << 8u) |
196 raw_data[5];
197
198 temp = ((temp * 625) >> 15u) * 10;
199 hum = ((hum * 625) >> 16u) * 10;
200
201 data->temperature = (int)temp - 50000;
202 data->humidity = hum;
203 data->previous_poll_time = ktime_get_boottime();
204
205 return 0;
206 }
207
208 /*
209 * aht10_interval_write() - store the given minimum poll interval.
210 * Return: 0 on success, -EINVAL if a value lower than the
211 * AHT10_MIN_POLL_INTERVAL is given
212 */
aht10_interval_write(struct aht10_data * data,long val)213 static ssize_t aht10_interval_write(struct aht10_data *data,
214 long val)
215 {
216 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX));
217 return 0;
218 }
219
220 /*
221 * aht10_interval_read() - read the minimum poll interval
222 * in milliseconds
223 */
aht10_interval_read(struct aht10_data * data,long * val)224 static ssize_t aht10_interval_read(struct aht10_data *data,
225 long *val)
226 {
227 *val = ktime_to_ms(data->min_poll_interval);
228 return 0;
229 }
230
231 /*
232 * aht10_temperature1_read() - read the temperature in millidegrees
233 */
aht10_temperature1_read(struct aht10_data * data,long * val)234 static int aht10_temperature1_read(struct aht10_data *data, long *val)
235 {
236 int res;
237
238 res = aht10_read_values(data);
239 if (res < 0)
240 return res;
241
242 *val = data->temperature;
243 return 0;
244 }
245
246 /*
247 * aht10_humidity1_read() - read the relative humidity in millipercent
248 */
aht10_humidity1_read(struct aht10_data * data,long * val)249 static int aht10_humidity1_read(struct aht10_data *data, long *val)
250 {
251 int res;
252
253 res = aht10_read_values(data);
254 if (res < 0)
255 return res;
256
257 *val = data->humidity;
258 return 0;
259 }
260
aht10_hwmon_visible(const void * data,enum hwmon_sensor_types type,u32 attr,int channel)261 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type,
262 u32 attr, int channel)
263 {
264 switch (type) {
265 case hwmon_temp:
266 case hwmon_humidity:
267 return 0444;
268 case hwmon_chip:
269 return 0644;
270 default:
271 return 0;
272 }
273 }
274
aht10_hwmon_read(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long * val)275 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
276 u32 attr, int channel, long *val)
277 {
278 struct aht10_data *data = dev_get_drvdata(dev);
279
280 switch (type) {
281 case hwmon_temp:
282 return aht10_temperature1_read(data, val);
283 case hwmon_humidity:
284 return aht10_humidity1_read(data, val);
285 case hwmon_chip:
286 return aht10_interval_read(data, val);
287 default:
288 return -EOPNOTSUPP;
289 }
290 }
291
aht10_hwmon_write(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long val)292 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
293 u32 attr, int channel, long val)
294 {
295 struct aht10_data *data = dev_get_drvdata(dev);
296
297 switch (type) {
298 case hwmon_chip:
299 return aht10_interval_write(data, val);
300 default:
301 return -EOPNOTSUPP;
302 }
303 }
304
305 static const struct hwmon_channel_info * const aht10_info[] = {
306 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
307 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
308 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
309 NULL,
310 };
311
312 static const struct hwmon_ops aht10_hwmon_ops = {
313 .is_visible = aht10_hwmon_visible,
314 .read = aht10_hwmon_read,
315 .write = aht10_hwmon_write,
316 };
317
318 static const struct hwmon_chip_info aht10_chip_info = {
319 .ops = &aht10_hwmon_ops,
320 .info = aht10_info,
321 };
322
aht10_probe(struct i2c_client * client)323 static int aht10_probe(struct i2c_client *client)
324 {
325 enum aht10_variant variant = (uintptr_t)i2c_get_match_data(client);
326 struct device *device = &client->dev;
327 struct device *hwmon_dev;
328 struct aht10_data *data;
329 int res;
330
331 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
332 return -ENOENT;
333
334 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
335 if (!data)
336 return -ENOMEM;
337
338 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL);
339 data->client = client;
340
341 switch (variant) {
342 case aht20:
343 data->meas_size = AHT20_MEAS_SIZE;
344 data->crc8 = true;
345 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
346 data->init_cmd = AHT20_CMD_INIT;
347 break;
348 case dht20:
349 data->meas_size = AHT20_MEAS_SIZE;
350 data->crc8 = true;
351 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
352 data->init_cmd = DHT20_CMD_INIT;
353 break;
354 default:
355 data->meas_size = AHT10_MEAS_SIZE;
356 data->init_cmd = AHT10_CMD_INIT;
357 break;
358 }
359
360 res = aht10_init(data);
361 if (res < 0)
362 return res;
363
364 res = aht10_read_values(data);
365 if (res < 0)
366 return res;
367
368 hwmon_dev = devm_hwmon_device_register_with_info(device,
369 client->name,
370 data,
371 &aht10_chip_info,
372 NULL);
373
374 return PTR_ERR_OR_ZERO(hwmon_dev);
375 }
376
377 static struct i2c_driver aht10_driver = {
378 .driver = {
379 .name = "aht10",
380 },
381 .probe = aht10_probe,
382 .id_table = aht10_id,
383 };
384
385 module_i2c_driver(aht10_driver);
386
387 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
388 MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
389 MODULE_VERSION("1.0");
390 MODULE_LICENSE("GPL v2");
391