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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
51enum aht10_variant { aht10, aht20 };
52
53static const struct i2c_device_id aht10_id[] = {
54 { "aht10", aht10 },
55 { "aht20", aht20 },
56 { },
57};
58MODULE_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
82struct 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 */
102static 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 */
133static 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
141DECLARE_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 */
149static 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 */
163static 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 */
222static 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 */
233static 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 */
243static 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 */
258static 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
270static 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
284static 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
301static 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
314static 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
321static 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
327static const struct hwmon_chip_info aht10_chip_info = {
328 .ops = &aht10_hwmon_ops,
329 .info = aht10_info,
330};
331
332static int aht10_probe(struct i2c_client *client)
333{
334 const struct i2c_device_id *id = i2c_match_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(client->adapter, I2C_FUNC_I2C))
342 return -ENOENT;
343
344 data = devm_kzalloc(device, 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(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(device,
373 client->name,
374 data,
375 &aht10_chip_info,
376 NULL);
377
378 return PTR_ERR_OR_ZERO(hwmon_dev);
379}
380
381static struct i2c_driver aht10_driver = {
382 .driver = {
383 .name = "aht10",
384 },
385 .probe = aht10_probe,
386 .id_table = aht10_id,
387};
388
389module_i2c_driver(aht10_driver);
390
391MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
392MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
393MODULE_VERSION("1.0");
394MODULE_LICENSE("GPL v2");