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1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | ||
3 | /* | |
4 | * aht10.c - Linux hwmon driver for AHT10 Temperature and Humidity sensor | |
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 | ||
14 | #define AHT10_MEAS_SIZE 6 | |
15 | ||
16 | /* | |
17 | * Poll intervals (in milliseconds) | |
18 | */ | |
19 | #define AHT10_DEFAULT_MIN_POLL_INTERVAL 2000 | |
20 | #define AHT10_MIN_POLL_INTERVAL 2000 | |
21 | ||
22 | /* | |
23 | * I2C command delays (in microseconds) | |
24 | */ | |
25 | #define AHT10_MEAS_DELAY 80000 | |
26 | #define AHT10_CMD_DELAY 350000 | |
27 | #define AHT10_DELAY_EXTRA 100000 | |
28 | ||
29 | /* | |
30 | * Command bytes | |
31 | */ | |
32 | #define AHT10_CMD_INIT 0b11100001 | |
33 | #define AHT10_CMD_MEAS 0b10101100 | |
34 | #define AHT10_CMD_RST 0b10111010 | |
35 | ||
36 | /* | |
37 | * Flags in the answer byte/command | |
38 | */ | |
39 | #define AHT10_CAL_ENABLED BIT(3) | |
40 | #define AHT10_BUSY BIT(7) | |
41 | #define AHT10_MODE_NOR (BIT(5) | BIT(6)) | |
42 | #define AHT10_MODE_CYC BIT(5) | |
43 | #define AHT10_MODE_CMD BIT(6) | |
44 | ||
45 | #define AHT10_MAX_POLL_INTERVAL_LEN 30 | |
46 | ||
47 | /** | |
48 | * struct aht10_data - All the data required to operate an AHT10 chip | |
49 | * @client: the i2c client associated with the AHT10 | |
50 | * @lock: a mutex that is used to prevent parallel access to the | |
51 | * i2c client | |
52 | * @min_poll_interval: the minimum poll interval | |
53 | * While the poll rate limit is not 100% necessary, | |
54 | * the datasheet recommends that a measurement | |
55 | * is not performed too often to prevent | |
56 | * the chip from warming up due to the heat it generates. | |
57 | * If it's unwanted, it can be ignored setting it to | |
58 | * it to 0. Default value is 2000 ms | |
59 | * @previous_poll_time: the previous time that the AHT10 | |
60 | * was polled | |
61 | * @temperature: the latest temperature value received from | |
62 | * the AHT10 | |
63 | * @humidity: the latest humidity value received from the | |
64 | * AHT10 | |
65 | */ | |
66 | ||
67 | struct aht10_data { | |
68 | struct i2c_client *client; | |
69 | /* | |
70 | * Prevent simultaneous access to the i2c | |
71 | * client and previous_poll_time | |
72 | */ | |
73 | struct mutex lock; | |
74 | ktime_t min_poll_interval; | |
75 | ktime_t previous_poll_time; | |
76 | int temperature; | |
77 | int humidity; | |
78 | }; | |
79 | ||
80 | /** | |
81 | * aht10_init() - Initialize an AHT10 chip | |
82 | * @client: the i2c client associated with the AHT10 | |
83 | * @data: the data associated with this AHT10 chip | |
84 | * Return: 0 if succesfull, 1 if not | |
85 | */ | |
86 | static int aht10_init(struct aht10_data *data) | |
87 | { | |
88 | const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC, | |
89 | 0x00}; | |
90 | int res; | |
91 | u8 status; | |
92 | struct i2c_client *client = data->client; | |
93 | ||
94 | res = i2c_master_send(client, cmd_init, 3); | |
95 | if (res < 0) | |
96 | return res; | |
97 | ||
98 | usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY + | |
99 | AHT10_DELAY_EXTRA); | |
100 | ||
101 | res = i2c_master_recv(client, &status, 1); | |
102 | if (res != 1) | |
103 | return -ENODATA; | |
104 | ||
105 | if (status & AHT10_BUSY) | |
106 | return -EBUSY; | |
107 | ||
108 | return 0; | |
109 | } | |
110 | ||
111 | /** | |
112 | * aht10_polltime_expired() - check if the minimum poll interval has | |
113 | * expired | |
114 | * @data: the data containing the time to compare | |
115 | * Return: 1 if the minimum poll interval has expired, 0 if not | |
116 | */ | |
117 | static int aht10_polltime_expired(struct aht10_data *data) | |
118 | { | |
119 | ktime_t current_time = ktime_get_boottime(); | |
120 | ktime_t difference = ktime_sub(current_time, data->previous_poll_time); | |
121 | ||
122 | return ktime_after(difference, data->min_poll_interval); | |
123 | } | |
124 | ||
125 | /** | |
126 | * aht10_read_values() - read and parse the raw data from the AHT10 | |
127 | * @aht10_data: the struct aht10_data to use for the lock | |
128 | * Return: 0 if succesfull, 1 if not | |
129 | */ | |
130 | static int aht10_read_values(struct aht10_data *data) | |
131 | { | |
132 | const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00}; | |
133 | u32 temp, hum; | |
134 | int res; | |
135 | u8 raw_data[AHT10_MEAS_SIZE]; | |
136 | struct i2c_client *client = data->client; | |
137 | ||
138 | mutex_lock(&data->lock); | |
139 | if (aht10_polltime_expired(data)) { | |
140 | res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); | |
cbfc6c61 DC |
141 | if (res < 0) { |
142 | mutex_unlock(&data->lock); | |
8c78f0de | 143 | return res; |
cbfc6c61 | 144 | } |
8c78f0de JCD |
145 | |
146 | usleep_range(AHT10_MEAS_DELAY, | |
147 | AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); | |
148 | ||
149 | res = i2c_master_recv(client, raw_data, AHT10_MEAS_SIZE); | |
150 | if (res != AHT10_MEAS_SIZE) { | |
151 | mutex_unlock(&data->lock); | |
152 | if (res >= 0) | |
153 | return -ENODATA; | |
154 | else | |
155 | return res; | |
156 | } | |
157 | ||
158 | hum = ((u32)raw_data[1] << 12u) | | |
159 | ((u32)raw_data[2] << 4u) | | |
160 | ((raw_data[3] & 0xF0u) >> 4u); | |
161 | ||
162 | temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | | |
163 | ((u32)raw_data[4] << 8u) | | |
164 | raw_data[5]; | |
165 | ||
166 | temp = ((temp * 625) >> 15u) * 10; | |
167 | hum = ((hum * 625) >> 16u) * 10; | |
168 | ||
169 | data->temperature = (int)temp - 50000; | |
170 | data->humidity = hum; | |
171 | data->previous_poll_time = ktime_get_boottime(); | |
172 | } | |
173 | mutex_unlock(&data->lock); | |
174 | return 0; | |
175 | } | |
176 | ||
177 | /** | |
178 | * aht10_interval_write() - store the given minimum poll interval. | |
179 | * Return: 0 on success, -EINVAL if a value lower than the | |
180 | * AHT10_MIN_POLL_INTERVAL is given | |
181 | */ | |
182 | static ssize_t aht10_interval_write(struct aht10_data *data, | |
183 | long val) | |
184 | { | |
185 | data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX)); | |
186 | return 0; | |
187 | } | |
188 | ||
189 | /** | |
190 | * aht10_interval_read() - read the minimum poll interval | |
191 | * in milliseconds | |
192 | */ | |
193 | static ssize_t aht10_interval_read(struct aht10_data *data, | |
194 | long *val) | |
195 | { | |
196 | *val = ktime_to_ms(data->min_poll_interval); | |
197 | return 0; | |
198 | } | |
199 | ||
200 | /** | |
201 | * aht10_temperature1_read() - read the temperature in millidegrees | |
202 | */ | |
203 | static int aht10_temperature1_read(struct aht10_data *data, long *val) | |
204 | { | |
205 | int res; | |
206 | ||
207 | res = aht10_read_values(data); | |
208 | if (res < 0) | |
209 | return res; | |
210 | ||
211 | *val = data->temperature; | |
212 | return 0; | |
213 | } | |
214 | ||
215 | /** | |
216 | * aht10_humidity1_read() - read the relative humidity in millipercent | |
217 | */ | |
218 | static int aht10_humidity1_read(struct aht10_data *data, long *val) | |
219 | { | |
220 | int res; | |
221 | ||
222 | res = aht10_read_values(data); | |
223 | if (res < 0) | |
224 | return res; | |
225 | ||
226 | *val = data->humidity; | |
227 | return 0; | |
228 | } | |
229 | ||
230 | static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type, | |
231 | u32 attr, int channel) | |
232 | { | |
233 | switch (type) { | |
234 | case hwmon_temp: | |
235 | case hwmon_humidity: | |
236 | return 0444; | |
237 | case hwmon_chip: | |
238 | return 0644; | |
239 | default: | |
240 | return 0; | |
241 | } | |
242 | } | |
243 | ||
244 | static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type, | |
245 | u32 attr, int channel, long *val) | |
246 | { | |
247 | struct aht10_data *data = dev_get_drvdata(dev); | |
248 | ||
249 | switch (type) { | |
250 | case hwmon_temp: | |
251 | return aht10_temperature1_read(data, val); | |
252 | case hwmon_humidity: | |
253 | return aht10_humidity1_read(data, val); | |
254 | case hwmon_chip: | |
255 | return aht10_interval_read(data, val); | |
256 | default: | |
257 | return -EOPNOTSUPP; | |
258 | } | |
259 | } | |
260 | ||
261 | static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type, | |
262 | u32 attr, int channel, long val) | |
263 | { | |
264 | struct aht10_data *data = dev_get_drvdata(dev); | |
265 | ||
266 | switch (type) { | |
267 | case hwmon_chip: | |
268 | return aht10_interval_write(data, val); | |
269 | default: | |
270 | return -EOPNOTSUPP; | |
271 | } | |
272 | } | |
273 | ||
274 | static const struct hwmon_channel_info *aht10_info[] = { | |
275 | HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), | |
276 | HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), | |
277 | HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), | |
278 | NULL, | |
279 | }; | |
280 | ||
281 | static const struct hwmon_ops aht10_hwmon_ops = { | |
282 | .is_visible = aht10_hwmon_visible, | |
283 | .read = aht10_hwmon_read, | |
284 | .write = aht10_hwmon_write, | |
285 | }; | |
286 | ||
287 | static const struct hwmon_chip_info aht10_chip_info = { | |
288 | .ops = &aht10_hwmon_ops, | |
289 | .info = aht10_info, | |
290 | }; | |
291 | ||
292 | static int aht10_probe(struct i2c_client *client, | |
293 | const struct i2c_device_id *aht10_id) | |
294 | { | |
295 | struct device *device = &client->dev; | |
296 | struct device *hwmon_dev; | |
297 | struct aht10_data *data; | |
298 | int res; | |
299 | ||
300 | if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) | |
301 | return -ENOENT; | |
302 | ||
303 | data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); | |
304 | if (!data) | |
305 | return -ENOMEM; | |
306 | ||
307 | data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); | |
308 | data->client = client; | |
309 | ||
310 | mutex_init(&data->lock); | |
311 | ||
312 | res = aht10_init(data); | |
313 | if (res < 0) | |
314 | return res; | |
315 | ||
316 | res = aht10_read_values(data); | |
317 | if (res < 0) | |
318 | return res; | |
319 | ||
320 | hwmon_dev = devm_hwmon_device_register_with_info(device, | |
321 | client->name, | |
322 | data, | |
323 | &aht10_chip_info, | |
324 | NULL); | |
325 | ||
326 | return PTR_ERR_OR_ZERO(hwmon_dev); | |
327 | } | |
328 | ||
329 | static const struct i2c_device_id aht10_id[] = { | |
330 | { "aht10", 0 }, | |
331 | { }, | |
332 | }; | |
333 | MODULE_DEVICE_TABLE(i2c, aht10_id); | |
334 | ||
335 | static struct i2c_driver aht10_driver = { | |
336 | .driver = { | |
337 | .name = "aht10", | |
338 | }, | |
339 | .probe = aht10_probe, | |
340 | .id_table = aht10_id, | |
341 | }; | |
342 | ||
343 | module_i2c_driver(aht10_driver); | |
344 | ||
345 | MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>"); | |
346 | MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver"); | |
347 | MODULE_VERSION("1.0"); | |
348 | MODULE_LICENSE("GPL v2"); |