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  
51  enum aht10_variant { aht10, aht20 };
52  
53  static const struct i2c_device_id aht10_id[] = {
54  	{ "aht10", aht10 },
55  	{ "aht20", aht20 },
56  	{ },
57  };
58  MODULE_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  
82  struct 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   */
aht10_init(struct aht10_data * data)102  static 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   */
aht10_polltime_expired(struct aht10_data * data)133  static 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  
141  DECLARE_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   */
crc8_check(u8 * raw_data,int count)149  static 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   */
aht10_read_values(struct aht10_data * data)163  static 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   */
aht10_interval_write(struct aht10_data * data,long val)222  static 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   */
aht10_interval_read(struct aht10_data * data,long * val)233  static 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   */
aht10_temperature1_read(struct aht10_data * data,long * val)243  static 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   */
aht10_humidity1_read(struct aht10_data * data,long * val)258  static 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  
aht10_hwmon_visible(const void * data,enum hwmon_sensor_types type,u32 attr,int channel)270  static 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  
aht10_hwmon_read(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long * val)284  static 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  
aht10_hwmon_write(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long val)301  static 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  
314  static 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  
321  static 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  
327  static const struct hwmon_chip_info aht10_chip_info = {
328  	.ops = &aht10_hwmon_ops,
329  	.info = aht10_info,
330  };
331  
aht10_probe(struct i2c_client * client)332  static 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  
381  static struct i2c_driver aht10_driver = {
382  	.driver = {
383  		.name = "aht10",
384  	},
385  	.probe      = aht10_probe,
386  	.id_table   = aht10_id,
387  };
388  
389  module_i2c_driver(aht10_driver);
390  
391  MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
392  MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
393  MODULE_VERSION("1.0");
394  MODULE_LICENSE("GPL v2");
395