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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#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
55enum aht10_variant { aht10, aht20, dht20};
56
57static const struct i2c_device_id aht10_id[] = {
58 { .name = "aht10", .driver_data = aht10 },
59 { .name = "aht20", .driver_data = aht20 },
60 { .name = "dht20", .driver_data = dht20 },
61 { }
62};
63MODULE_DEVICE_TABLE(i2c, aht10_id);
64
65static const struct of_device_id aht10_of_match[] = {
66 { .compatible = "aosong,aht10", .data = (void *)aht10 },
67 { .compatible = "aosong,aht20", .data = (void *)aht20 },
68 { .compatible = "aosong,dht20", .data = (void *)dht20 },
69 {}
70};
71
72MODULE_DEVICE_TABLE(of, aht10_of_match);
73
74/**
75 * struct aht10_data - All the data required to operate an AHT10/AHT20 chip
76 * @client: the i2c client associated with the AHT10/AHT20
77 * @min_poll_interval: the minimum poll interval
78 * While the poll rate limit is not 100% necessary,
79 * the datasheet recommends that a measurement
80 * is not performed too often to prevent
81 * the chip from warming up due to the heat it generates.
82 * If it's unwanted, it can be ignored setting it to
83 * it to 0. Default value is 2000 ms
84 * @previous_poll_time: the previous time that the AHT10/AHT20
85 * was polled
86 * @temperature: the latest temperature value received from
87 * the AHT10/AHT20
88 * @humidity: the latest humidity value received from the
89 * AHT10/AHT20
90 * @crc8: crc8 support flag
91 * @meas_size: measurements data size
92 * @init_cmd: Initialization command
93 */
94
95struct aht10_data {
96 struct i2c_client *client;
97 ktime_t min_poll_interval;
98 ktime_t previous_poll_time;
99 int temperature;
100 int humidity;
101 bool crc8;
102 unsigned int meas_size;
103 u8 init_cmd;
104};
105
106/*
107 * aht10_init() - Initialize an AHT10/AHT20 chip
108 * @data: the data associated with this AHT10/AHT20 chip
109 * Return: 0 if successful, 1 if not
110 */
111static int aht10_init(struct aht10_data *data)
112{
113 const u8 cmd_init[] = {data->init_cmd, AHT10_CAL_ENABLED | AHT10_MODE_CYC,
114 0x00};
115 int res;
116 u8 status;
117 struct i2c_client *client = data->client;
118
119 res = i2c_master_send(client, cmd_init, sizeof(cmd_init));
120 if (res < 0)
121 return res;
122
123 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY +
124 AHT10_DELAY_EXTRA);
125
126 res = i2c_master_recv(client, &status, 1);
127 if (res != 1)
128 return -ENODATA;
129
130 if (status & AHT10_BUSY)
131 return -EBUSY;
132
133 return 0;
134}
135
136/*
137 * aht10_polltime_expired() - check if the minimum poll interval has
138 * expired
139 * @data: the data containing the time to compare
140 * Return: 1 if the minimum poll interval has expired, 0 if not
141 */
142static int aht10_polltime_expired(struct aht10_data *data)
143{
144 ktime_t current_time = ktime_get_boottime();
145 ktime_t difference = ktime_sub(current_time, data->previous_poll_time);
146
147 return ktime_after(difference, data->min_poll_interval);
148}
149
150DECLARE_CRC8_TABLE(crc8_table);
151
152/*
153 * crc8_check() - check crc of the sensor's measurements
154 * @raw_data: data frame received from sensor(including crc as the last byte)
155 * @count: size of the data frame
156 * Return: 0 if successful, 1 if not
157 */
158static int crc8_check(u8 *raw_data, int count)
159{
160 /*
161 * crc calculated on the whole frame(including crc byte) should yield
162 * zero in case of correctly received bytes
163 */
164 return crc8(crc8_table, raw_data, count, CRC8_INIT_VALUE);
165}
166
167/*
168 * aht10_read_values() - read and parse the raw data from the AHT10/AHT20
169 * @data: the struct aht10_data to use for the lock
170 * Return: 0 if successful, 1 if not
171 */
172static int aht10_read_values(struct aht10_data *data)
173{
174 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00};
175 u32 temp, hum;
176 int res;
177 u8 raw_data[AHT20_MEAS_SIZE];
178 struct i2c_client *client = data->client;
179
180 if (!aht10_polltime_expired(data))
181 return 0;
182
183 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas));
184 if (res < 0)
185 return res;
186
187 usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA);
188
189 res = i2c_master_recv(client, raw_data, data->meas_size);
190 if (res != data->meas_size) {
191 if (res >= 0)
192 return -ENODATA;
193 return res;
194 }
195
196 if (data->crc8 && crc8_check(raw_data, data->meas_size))
197 return -EIO;
198
199 hum = ((u32)raw_data[1] << 12u) |
200 ((u32)raw_data[2] << 4u) |
201 ((raw_data[3] & 0xF0u) >> 4u);
202
203 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) |
204 ((u32)raw_data[4] << 8u) |
205 raw_data[5];
206
207 temp = ((temp * 625) >> 15u) * 10;
208 hum = ((hum * 625) >> 16u) * 10;
209
210 data->temperature = (int)temp - 50000;
211 data->humidity = hum;
212 data->previous_poll_time = ktime_get_boottime();
213
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 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 data->init_cmd = AHT20_CMD_INIT;
356 break;
357 case dht20:
358 data->meas_size = AHT20_MEAS_SIZE;
359 data->crc8 = true;
360 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
361 data->init_cmd = DHT20_CMD_INIT;
362 break;
363 default:
364 data->meas_size = AHT10_MEAS_SIZE;
365 data->init_cmd = AHT10_CMD_INIT;
366 break;
367 }
368
369 res = aht10_init(data);
370 if (res < 0)
371 return res;
372
373 res = aht10_read_values(data);
374 if (res < 0)
375 return res;
376
377 hwmon_dev = devm_hwmon_device_register_with_info(device,
378 client->name,
379 data,
380 &aht10_chip_info,
381 NULL);
382
383 return PTR_ERR_OR_ZERO(hwmon_dev);
384}
385
386static struct i2c_driver aht10_driver = {
387 .driver = {
388 .name = "aht10",
389 .of_match_table = aht10_of_match,
390 },
391 .probe = aht10_probe,
392 .id_table = aht10_id,
393};
394
395module_i2c_driver(aht10_driver);
396
397MODULE_AUTHOR("Johannes Cornelis Draaijer <[email protected]>");
398MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
399MODULE_VERSION("1.0");
400MODULE_LICENSE("GPL v2");