aht10.c

  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	{ "aht10", aht10 },
 59	{ "aht20", aht20 },
 60	{ "dht20", dht20 },
 61	{ },
 62};
 63MODULE_DEVICE_TABLE(i2c, aht10_id);
 64
 65/**
 66 *   struct aht10_data - All the data required to operate an AHT10/AHT20 chip
 67 *   @client: the i2c client associated with the AHT10/AHT20
 68 *   @min_poll_interval: the minimum poll interval
 69 *                   While the poll rate limit is not 100% necessary,
 70 *                   the datasheet recommends that a measurement
 71 *                   is not performed too often to prevent
 72 *                   the chip from warming up due to the heat it generates.
 73 *                   If it's unwanted, it can be ignored setting it to
 74 *                   it to 0. Default value is 2000 ms
 75 *   @previous_poll_time: the previous time that the AHT10/AHT20
 76 *                        was polled
 77 *   @temperature: the latest temperature value received from
 78 *                 the AHT10/AHT20
 79 *   @humidity: the latest humidity value received from the
 80 *              AHT10/AHT20
 81 *   @crc8: crc8 support flag
 82 *   @meas_size: measurements data size
 83 *   @init_cmd: Initialization command
 84 */
 85
 86struct aht10_data {
 87	struct i2c_client *client;
 88	ktime_t min_poll_interval;
 89	ktime_t previous_poll_time;
 90	int temperature;
 91	int humidity;
 92	bool crc8;
 93	unsigned int meas_size;
 94	u8 init_cmd;
 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 */
102static int aht10_init(struct aht10_data *data)
103{
104	const u8 cmd_init[] = {data->init_cmd, 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, sizeof(cmd_init));
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 */
133static 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
141DECLARE_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 */
149static 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 */
163static 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	if (!aht10_polltime_expired(data))
172		return 0;
173
174	res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas));
175	if (res < 0)
176		return res;
177
178	usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA);
179
180	res = i2c_master_recv(client, raw_data, data->meas_size);
181	if (res != data->meas_size) {
182		if (res >= 0)
183			return -ENODATA;
184		return res;
185	}
186
187	if (data->crc8 && crc8_check(raw_data, data->meas_size))
188		return -EIO;
189
190	hum =   ((u32)raw_data[1] << 12u) |
191		((u32)raw_data[2] << 4u) |
192		((raw_data[3] & 0xF0u) >> 4u);
193
194	temp =  ((u32)(raw_data[3] & 0x0Fu) << 16u) |
195		((u32)raw_data[4] << 8u) |
196		raw_data[5];
197
198	temp = ((temp * 625) >> 15u) * 10;
199	hum = ((hum * 625) >> 16u) * 10;
200
201	data->temperature = (int)temp - 50000;
202	data->humidity = hum;
203	data->previous_poll_time = ktime_get_boottime();
204
205	return 0;
206}
207
208/*
209 * aht10_interval_write() - store the given minimum poll interval.
210 * Return: 0 on success, -EINVAL if a value lower than the
211 *         AHT10_MIN_POLL_INTERVAL is given
212 */
213static ssize_t aht10_interval_write(struct aht10_data *data,
214				    long val)
215{
216	data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX));
217	return 0;
218}
219
220/*
221 * aht10_interval_read() - read the minimum poll interval
222 *                            in milliseconds
223 */
224static ssize_t aht10_interval_read(struct aht10_data *data,
225				   long *val)
226{
227	*val = ktime_to_ms(data->min_poll_interval);
228	return 0;
229}
230
231/*
232 * aht10_temperature1_read() - read the temperature in millidegrees
233 */
234static int aht10_temperature1_read(struct aht10_data *data, long *val)
235{
236	int res;
237
238	res = aht10_read_values(data);
239	if (res < 0)
240		return res;
241
242	*val = data->temperature;
243	return 0;
244}
245
246/*
247 * aht10_humidity1_read() - read the relative humidity in millipercent
248 */
249static int aht10_humidity1_read(struct aht10_data *data, long *val)
250{
251	int res;
252
253	res = aht10_read_values(data);
254	if (res < 0)
255		return res;
256
257	*val = data->humidity;
258	return 0;
259}
260
261static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type,
262				   u32 attr, int channel)
263{
264	switch (type) {
265	case hwmon_temp:
266	case hwmon_humidity:
267		return 0444;
268	case hwmon_chip:
269		return 0644;
270	default:
271		return 0;
272	}
273}
274
275static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
276			    u32 attr, int channel, long *val)
277{
278	struct aht10_data *data = dev_get_drvdata(dev);
279
280	switch (type) {
281	case hwmon_temp:
282		return aht10_temperature1_read(data, val);
283	case hwmon_humidity:
284		return aht10_humidity1_read(data, val);
285	case hwmon_chip:
286		return aht10_interval_read(data, val);
287	default:
288		return -EOPNOTSUPP;
289	}
290}
291
292static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
293			     u32 attr, int channel, long val)
294{
295	struct aht10_data *data = dev_get_drvdata(dev);
296
297	switch (type) {
298	case hwmon_chip:
299		return aht10_interval_write(data, val);
300	default:
301		return -EOPNOTSUPP;
302	}
303}
304
305static const struct hwmon_channel_info * const aht10_info[] = {
306	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
307	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
308	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
309	NULL,
310};
311
312static const struct hwmon_ops aht10_hwmon_ops = {
313	.is_visible = aht10_hwmon_visible,
314	.read = aht10_hwmon_read,
315	.write = aht10_hwmon_write,
316};
317
318static const struct hwmon_chip_info aht10_chip_info = {
319	.ops = &aht10_hwmon_ops,
320	.info = aht10_info,
321};
322
323static int aht10_probe(struct i2c_client *client)
324{
325	enum aht10_variant variant = (uintptr_t)i2c_get_match_data(client);
326	struct device *device = &client->dev;
327	struct device *hwmon_dev;
328	struct aht10_data *data;
329	int res;
330
331	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
332		return -ENOENT;
333
334	data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
335	if (!data)
336		return -ENOMEM;
337
338	data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL);
339	data->client = client;
340
341	switch (variant) {
342	case aht20:
343		data->meas_size = AHT20_MEAS_SIZE;
344		data->crc8 = true;
345		crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
346		data->init_cmd = AHT20_CMD_INIT;
347		break;
348	case dht20:
349		data->meas_size = AHT20_MEAS_SIZE;
350		data->crc8 = true;
351		crc8_populate_msb(crc8_table, AHT20_CRC8_POLY);
352		data->init_cmd = DHT20_CMD_INIT;
353		break;
354	default:
355		data->meas_size = AHT10_MEAS_SIZE;
356		data->init_cmd = AHT10_CMD_INIT;
357		break;
358	}
359
360	res = aht10_init(data);
361	if (res < 0)
362		return res;
363
364	res = aht10_read_values(data);
365	if (res < 0)
366		return res;
367
368	hwmon_dev = devm_hwmon_device_register_with_info(device,
369							 client->name,
370							 data,
371							 &aht10_chip_info,
372							 NULL);
373
374	return PTR_ERR_OR_ZERO(hwmon_dev);
375}
376
377static struct i2c_driver aht10_driver = {
378	.driver = {
379		.name = "aht10",
380	},
381	.probe      = aht10_probe,
382	.id_table   = aht10_id,
383};
384
385module_i2c_driver(aht10_driver);
386
387MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
388MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
389MODULE_VERSION("1.0");
390MODULE_LICENSE("GPL v2");