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 DHT20_CMD_INIT 0x71
41
42/*
43 * Flags in the answer byte/command
44 */
45#define AHT10_CAL_ENABLED BIT(3)
46#define AHT10_BUSY BIT(7)
47#define AHT10_MODE_NOR (BIT(5) | BIT(6))
48#define AHT10_MODE_CYC BIT(5)
49#define AHT10_MODE_CMD BIT(6)
50
51#define AHT10_MAX_POLL_INTERVAL_LEN 30
52
53enum aht10_variant { aht10, aht20, dht20};
54
55static const struct i2c_device_id aht10_id[] = {
56 { "aht10", aht10 },
57 { "aht20", aht20 },
58 { "dht20", dht20 },
59 { },
60};
61MODULE_DEVICE_TABLE(i2c, aht10_id);
62
63/**
64 * struct aht10_data - All the data required to operate an AHT10/AHT20 chip
65 * @client: the i2c client associated with the AHT10/AHT20
66 * @min_poll_interval: the minimum poll interval
67 * While the poll rate limit is not 100% necessary,
68 * the datasheet recommends that a measurement
69 * is not performed too often to prevent
70 * the chip from warming up due to the heat it generates.
71 * If it's unwanted, it can be ignored setting it to
72 * it to 0. Default value is 2000 ms
73 * @previous_poll_time: the previous time that the AHT10/AHT20
74 * was polled
75 * @temperature: the latest temperature value received from
76 * the AHT10/AHT20
77 * @humidity: the latest humidity value received from the
78 * AHT10/AHT20
79 * @crc8: crc8 support flag
80 * @meas_size: measurements data size
81 * @init_cmd: Initialization command
82 */
83
84struct aht10_data {
85 struct i2c_client *client;
86 ktime_t min_poll_interval;
87 ktime_t previous_poll_time;
88 int temperature;
89 int humidity;
90 bool crc8;
91 unsigned int meas_size;
92 u8 init_cmd;
93};
94
95/*
96 * aht10_init() - Initialize an AHT10/AHT20 chip
97 * @data: the data associated with this AHT10/AHT20 chip
98 * Return: 0 if successful, 1 if not
99 */
100static int aht10_init(struct aht10_data *data)
101{
102 const u8 cmd_init[] = {data->init_cmd, AHT10_CAL_ENABLED | AHT10_MODE_CYC,
103 0x00};
104 int res;
105 u8 status;
106 struct i2c_client *client = data->client;
107
108 res = i2c_master_send(client, buf: cmd_init, count: sizeof(cmd_init));
109 if (res < 0)
110 return res;
111
112 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY +
113 AHT10_DELAY_EXTRA);
114
115 res = i2c_master_recv(client, buf: &status, count: 1);
116 if (res != 1)
117 return -ENODATA;
118
119 if (status & AHT10_BUSY)
120 return -EBUSY;
121
122 return 0;
123}
124
125/*
126 * aht10_polltime_expired() - check if the minimum poll interval has
127 * expired
128 * @data: the data containing the time to compare
129 * Return: 1 if the minimum poll interval has expired, 0 if not
130 */
131static int aht10_polltime_expired(struct aht10_data *data)
132{
133 ktime_t current_time = ktime_get_boottime();
134 ktime_t difference = ktime_sub(current_time, data->previous_poll_time);
135
136 return ktime_after(cmp1: difference, cmp2: data->min_poll_interval);
137}
138
139DECLARE_CRC8_TABLE(crc8_table);
140
141/*
142 * crc8_check() - check crc of the sensor's measurements
143 * @raw_data: data frame received from sensor(including crc as the last byte)
144 * @count: size of the data frame
145 * Return: 0 if successful, 1 if not
146 */
147static int crc8_check(u8 *raw_data, int count)
148{
149 /*
150 * crc calculated on the whole frame(including crc byte) should yield
151 * zero in case of correctly received bytes
152 */
153 return crc8(table: crc8_table, pdata: raw_data, nbytes: count, CRC8_INIT_VALUE);
154}
155
156/*
157 * aht10_read_values() - read and parse the raw data from the AHT10/AHT20
158 * @data: the struct aht10_data to use for the lock
159 * Return: 0 if successful, 1 if not
160 */
161static int aht10_read_values(struct aht10_data *data)
162{
163 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00};
164 u32 temp, hum;
165 int res;
166 u8 raw_data[AHT20_MEAS_SIZE];
167 struct i2c_client *client = data->client;
168
169 if (!aht10_polltime_expired(data))
170 return 0;
171
172 res = i2c_master_send(client, buf: cmd_meas, count: sizeof(cmd_meas));
173 if (res < 0)
174 return res;
175
176 usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA);
177
178 res = i2c_master_recv(client, buf: raw_data, count: data->meas_size);
179 if (res != data->meas_size) {
180 if (res >= 0)
181 return -ENODATA;
182 return res;
183 }
184
185 if (data->crc8 && crc8_check(raw_data, count: data->meas_size))
186 return -EIO;
187
188 hum = ((u32)raw_data[1] << 12u) |
189 ((u32)raw_data[2] << 4u) |
190 ((raw_data[3] & 0xF0u) >> 4u);
191
192 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) |
193 ((u32)raw_data[4] << 8u) |
194 raw_data[5];
195
196 temp = ((temp * 625) >> 15u) * 10;
197 hum = ((hum * 625) >> 16u) * 10;
198
199 data->temperature = (int)temp - 50000;
200 data->humidity = hum;
201 data->previous_poll_time = ktime_get_boottime();
202
203 return 0;
204}
205
206/*
207 * aht10_interval_write() - store the given minimum poll interval.
208 * Return: 0 on success, -EINVAL if a value lower than the
209 * AHT10_MIN_POLL_INTERVAL is given
210 */
211static ssize_t aht10_interval_write(struct aht10_data *data,
212 long val)
213{
214 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX));
215 return 0;
216}
217
218/*
219 * aht10_interval_read() - read the minimum poll interval
220 * in milliseconds
221 */
222static ssize_t aht10_interval_read(struct aht10_data *data,
223 long *val)
224{
225 *val = ktime_to_ms(kt: data->min_poll_interval);
226 return 0;
227}
228
229/*
230 * aht10_temperature1_read() - read the temperature in millidegrees
231 */
232static int aht10_temperature1_read(struct aht10_data *data, long *val)
233{
234 int res;
235
236 res = aht10_read_values(data);
237 if (res < 0)
238 return res;
239
240 *val = data->temperature;
241 return 0;
242}
243
244/*
245 * aht10_humidity1_read() - read the relative humidity in millipercent
246 */
247static int aht10_humidity1_read(struct aht10_data *data, long *val)
248{
249 int res;
250
251 res = aht10_read_values(data);
252 if (res < 0)
253 return res;
254
255 *val = data->humidity;
256 return 0;
257}
258
259static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type,
260 u32 attr, int channel)
261{
262 switch (type) {
263 case hwmon_temp:
264 case hwmon_humidity:
265 return 0444;
266 case hwmon_chip:
267 return 0644;
268 default:
269 return 0;
270 }
271}
272
273static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
274 u32 attr, int channel, long *val)
275{
276 struct aht10_data *data = dev_get_drvdata(dev);
277
278 switch (type) {
279 case hwmon_temp:
280 return aht10_temperature1_read(data, val);
281 case hwmon_humidity:
282 return aht10_humidity1_read(data, val);
283 case hwmon_chip:
284 return aht10_interval_read(data, val);
285 default:
286 return -EOPNOTSUPP;
287 }
288}
289
290static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
291 u32 attr, int channel, long val)
292{
293 struct aht10_data *data = dev_get_drvdata(dev);
294
295 switch (type) {
296 case hwmon_chip:
297 return aht10_interval_write(data, val);
298 default:
299 return -EOPNOTSUPP;
300 }
301}
302
303static const struct hwmon_channel_info * const aht10_info[] = {
304 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
305 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
306 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
307 NULL,
308};
309
310static const struct hwmon_ops aht10_hwmon_ops = {
311 .is_visible = aht10_hwmon_visible,
312 .read = aht10_hwmon_read,
313 .write = aht10_hwmon_write,
314};
315
316static const struct hwmon_chip_info aht10_chip_info = {
317 .ops = &aht10_hwmon_ops,
318 .info = aht10_info,
319};
320
321static int aht10_probe(struct i2c_client *client)
322{
323 enum aht10_variant variant = (uintptr_t)i2c_get_match_data(client);
324 struct device *device = &client->dev;
325 struct device *hwmon_dev;
326 struct aht10_data *data;
327 int res;
328
329 if (!i2c_check_functionality(adap: client->adapter, I2C_FUNC_I2C))
330 return -ENOENT;
331
332 data = devm_kzalloc(dev: device, size: sizeof(*data), GFP_KERNEL);
333 if (!data)
334 return -ENOMEM;
335
336 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL);
337 data->client = client;
338
339 switch (variant) {
340 case aht20:
341 data->meas_size = AHT20_MEAS_SIZE;
342 data->crc8 = true;
343 crc8_populate_msb(table: crc8_table, AHT20_CRC8_POLY);
344 data->init_cmd = AHT10_CMD_INIT;
345 break;
346 case dht20:
347 data->meas_size = AHT20_MEAS_SIZE;
348 data->crc8 = true;
349 crc8_populate_msb(table: crc8_table, AHT20_CRC8_POLY);
350 data->init_cmd = DHT20_CMD_INIT;
351 break;
352 default:
353 data->meas_size = AHT10_MEAS_SIZE;
354 data->init_cmd = AHT10_CMD_INIT;
355 break;
356 }
357
358 res = aht10_init(data);
359 if (res < 0)
360 return res;
361
362 res = aht10_read_values(data);
363 if (res < 0)
364 return res;
365
366 hwmon_dev = devm_hwmon_device_register_with_info(dev: device,
367 name: client->name,
368 drvdata: data,
369 info: &aht10_chip_info,
370 NULL);
371
372 return PTR_ERR_OR_ZERO(ptr: hwmon_dev);
373}
374
375static struct i2c_driver aht10_driver = {
376 .driver = {
377 .name = "aht10",
378 },
379 .probe = aht10_probe,
380 .id_table = aht10_id,
381};
382
383module_i2c_driver(aht10_driver);
384
385MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
386MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
387MODULE_VERSION("1.0");
388MODULE_LICENSE("GPL v2");
389

source code of linux/drivers/hwmon/aht10.c