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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
67struct 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 */
86static 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 */
117static 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 */
130static 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));
141 if (res < 0) {
142 mutex_unlock(&data->lock);
143 return res;
144 }
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 */
182static 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 */
193static 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 */
203static 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 */
218static 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
230static 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
244static 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
261static 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
274static 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
281static 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
287static const struct hwmon_chip_info aht10_chip_info = {
288 .ops = &aht10_hwmon_ops,
289 .info = aht10_info,
290};
291
292static int aht10_probe(struct i2c_client *client)
293{
294 struct device *device = &client->dev;
295 struct device *hwmon_dev;
296 struct aht10_data *data;
297 int res;
298
299 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
300 return -ENOENT;
301
302 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
303 if (!data)
304 return -ENOMEM;
305
306 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL);
307 data->client = client;
308
309 mutex_init(&data->lock);
310
311 res = aht10_init(data);
312 if (res < 0)
313 return res;
314
315 res = aht10_read_values(data);
316 if (res < 0)
317 return res;
318
319 hwmon_dev = devm_hwmon_device_register_with_info(device,
320 client->name,
321 data,
322 &aht10_chip_info,
323 NULL);
324
325 return PTR_ERR_OR_ZERO(hwmon_dev);
326}
327
328static const struct i2c_device_id aht10_id[] = {
329 { "aht10", 0 },
330 { },
331};
332MODULE_DEVICE_TABLE(i2c, aht10_id);
333
334static struct i2c_driver aht10_driver = {
335 .driver = {
336 .name = "aht10",
337 },
338 .probe_new = aht10_probe,
339 .id_table = aht10_id,
340};
341
342module_i2c_driver(aht10_driver);
343
344MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
345MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver");
346MODULE_VERSION("1.0");
347MODULE_LICENSE("GPL v2");