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 * @data: the data associated with this AHT10 chip
83 * Return: 0 if succesfull, 1 if not
84 */
aht10_init(struct aht10_data * data)85 static int aht10_init(struct aht10_data *data)
86 {
87 const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC,
88 0x00};
89 int res;
90 u8 status;
91 struct i2c_client *client = data->client;
92
93 res = i2c_master_send(client, cmd_init, 3);
94 if (res < 0)
95 return res;
96
97 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY +
98 AHT10_DELAY_EXTRA);
99
100 res = i2c_master_recv(client, &status, 1);
101 if (res != 1)
102 return -ENODATA;
103
104 if (status & AHT10_BUSY)
105 return -EBUSY;
106
107 return 0;
108 }
109
110 /**
111 * aht10_polltime_expired() - check if the minimum poll interval has
112 * expired
113 * @data: the data containing the time to compare
114 * Return: 1 if the minimum poll interval has expired, 0 if not
115 */
aht10_polltime_expired(struct aht10_data * data)116 static int aht10_polltime_expired(struct aht10_data *data)
117 {
118 ktime_t current_time = ktime_get_boottime();
119 ktime_t difference = ktime_sub(current_time, data->previous_poll_time);
120
121 return ktime_after(difference, data->min_poll_interval);
122 }
123
124 /**
125 * aht10_read_values() - read and parse the raw data from the AHT10
126 * @data: the struct aht10_data to use for the lock
127 * Return: 0 if succesfull, 1 if not
128 */
aht10_read_values(struct aht10_data * data)129 static int aht10_read_values(struct aht10_data *data)
130 {
131 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00};
132 u32 temp, hum;
133 int res;
134 u8 raw_data[AHT10_MEAS_SIZE];
135 struct i2c_client *client = data->client;
136
137 mutex_lock(&data->lock);
138 if (aht10_polltime_expired(data)) {
139 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas));
140 if (res < 0) {
141 mutex_unlock(&data->lock);
142 return res;
143 }
144
145 usleep_range(AHT10_MEAS_DELAY,
146 AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA);
147
148 res = i2c_master_recv(client, raw_data, AHT10_MEAS_SIZE);
149 if (res != AHT10_MEAS_SIZE) {
150 mutex_unlock(&data->lock);
151 if (res >= 0)
152 return -ENODATA;
153 else
154 return res;
155 }
156
157 hum = ((u32)raw_data[1] << 12u) |
158 ((u32)raw_data[2] << 4u) |
159 ((raw_data[3] & 0xF0u) >> 4u);
160
161 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) |
162 ((u32)raw_data[4] << 8u) |
163 raw_data[5];
164
165 temp = ((temp * 625) >> 15u) * 10;
166 hum = ((hum * 625) >> 16u) * 10;
167
168 data->temperature = (int)temp - 50000;
169 data->humidity = hum;
170 data->previous_poll_time = ktime_get_boottime();
171 }
172 mutex_unlock(&data->lock);
173 return 0;
174 }
175
176 /**
177 * aht10_interval_write() - store the given minimum poll interval.
178 * Return: 0 on success, -EINVAL if a value lower than the
179 * AHT10_MIN_POLL_INTERVAL is given
180 */
aht10_interval_write(struct aht10_data * data,long val)181 static ssize_t aht10_interval_write(struct aht10_data *data,
182 long val)
183 {
184 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX));
185 return 0;
186 }
187
188 /**
189 * aht10_interval_read() - read the minimum poll interval
190 * in milliseconds
191 */
aht10_interval_read(struct aht10_data * data,long * val)192 static ssize_t aht10_interval_read(struct aht10_data *data,
193 long *val)
194 {
195 *val = ktime_to_ms(data->min_poll_interval);
196 return 0;
197 }
198
199 /**
200 * aht10_temperature1_read() - read the temperature in millidegrees
201 */
aht10_temperature1_read(struct aht10_data * data,long * val)202 static int aht10_temperature1_read(struct aht10_data *data, long *val)
203 {
204 int res;
205
206 res = aht10_read_values(data);
207 if (res < 0)
208 return res;
209
210 *val = data->temperature;
211 return 0;
212 }
213
214 /**
215 * aht10_humidity1_read() - read the relative humidity in millipercent
216 */
aht10_humidity1_read(struct aht10_data * data,long * val)217 static int aht10_humidity1_read(struct aht10_data *data, long *val)
218 {
219 int res;
220
221 res = aht10_read_values(data);
222 if (res < 0)
223 return res;
224
225 *val = data->humidity;
226 return 0;
227 }
228
aht10_hwmon_visible(const void * data,enum hwmon_sensor_types type,u32 attr,int channel)229 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type,
230 u32 attr, int channel)
231 {
232 switch (type) {
233 case hwmon_temp:
234 case hwmon_humidity:
235 return 0444;
236 case hwmon_chip:
237 return 0644;
238 default:
239 return 0;
240 }
241 }
242
aht10_hwmon_read(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long * val)243 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
244 u32 attr, int channel, long *val)
245 {
246 struct aht10_data *data = dev_get_drvdata(dev);
247
248 switch (type) {
249 case hwmon_temp:
250 return aht10_temperature1_read(data, val);
251 case hwmon_humidity:
252 return aht10_humidity1_read(data, val);
253 case hwmon_chip:
254 return aht10_interval_read(data, val);
255 default:
256 return -EOPNOTSUPP;
257 }
258 }
259
aht10_hwmon_write(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long val)260 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
261 u32 attr, int channel, long val)
262 {
263 struct aht10_data *data = dev_get_drvdata(dev);
264
265 switch (type) {
266 case hwmon_chip:
267 return aht10_interval_write(data, val);
268 default:
269 return -EOPNOTSUPP;
270 }
271 }
272
273 static const struct hwmon_channel_info *aht10_info[] = {
274 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
275 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
276 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
277 NULL,
278 };
279
280 static const struct hwmon_ops aht10_hwmon_ops = {
281 .is_visible = aht10_hwmon_visible,
282 .read = aht10_hwmon_read,
283 .write = aht10_hwmon_write,
284 };
285
286 static const struct hwmon_chip_info aht10_chip_info = {
287 .ops = &aht10_hwmon_ops,
288 .info = aht10_info,
289 };
290
aht10_probe(struct i2c_client * client)291 static int aht10_probe(struct i2c_client *client)
292 {
293 struct device *device = &client->dev;
294 struct device *hwmon_dev;
295 struct aht10_data *data;
296 int res;
297
298 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
299 return -ENOENT;
300
301 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
302 if (!data)
303 return -ENOMEM;
304
305 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL);
306 data->client = client;
307
308 mutex_init(&data->lock);
309
310 res = aht10_init(data);
311 if (res < 0)
312 return res;
313
314 res = aht10_read_values(data);
315 if (res < 0)
316 return res;
317
318 hwmon_dev = devm_hwmon_device_register_with_info(device,
319 client->name,
320 data,
321 &aht10_chip_info,
322 NULL);
323
324 return PTR_ERR_OR_ZERO(hwmon_dev);
325 }
326
327 static const struct i2c_device_id aht10_id[] = {
328 { "aht10", 0 },
329 { },
330 };
331 MODULE_DEVICE_TABLE(i2c, aht10_id);
332
333 static struct i2c_driver aht10_driver = {
334 .driver = {
335 .name = "aht10",
336 },
337 .probe_new = aht10_probe,
338 .id_table = aht10_id,
339 };
340
341 module_i2c_driver(aht10_driver);
342
343 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
344 MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver");
345 MODULE_VERSION("1.0");
346 MODULE_LICENSE("GPL v2");
347