sht4x.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2
  3/*
  4 * Copyright (c) Linumiz 2021
  5 *
  6 * sht4x.c - Linux hwmon driver for SHT4x Temperature and Humidity sensor
  7 *
  8 * Author: Navin Sankar Velliangiri <navin@linumiz.com>
  9 */
 10
 11#include <linux/crc8.h>
 12#include <linux/delay.h>
 13#include <linux/hwmon.h>
 14#include <linux/hwmon-sysfs.h>
 15#include <linux/i2c.h>
 16#include <linux/jiffies.h>
 17#include <linux/module.h>
 18
 19/*
 20 * Poll intervals (in milliseconds)
 21 */
 22#define SHT4X_MIN_POLL_INTERVAL	2000
 23
 24/*
 25 * I2C command delays (in microseconds)
 26 */
 27#define SHT4X_MEAS_DELAY_HPM	8200	/* see t_MEAS,h in datasheet */
 28#define SHT4X_DELAY_EXTRA	10000
 29
 30/*
 31 * Command Bytes
 32 */
 33#define SHT4X_CMD_MEASURE_HPM	0b11111101
 34#define SHT4X_CMD_RESET		0b10010100
 35#define SHT4X_CMD_HEATER_20_1	0b00011110
 36#define SHT4X_CMD_HEATER_20_01	0b00010101
 37#define SHT4X_CMD_HEATER_110_1	0b00101111
 38#define SHT4X_CMD_HEATER_110_01	0b00100100
 39#define SHT4X_CMD_HEATER_200_1	0b00111001
 40#define SHT4X_CMD_HEATER_200_01 0b00110010
 41
 42#define SHT4X_CMD_LEN		1
 43#define SHT4X_CRC8_LEN		1
 44#define SHT4X_WORD_LEN		2
 45#define SHT4X_RESPONSE_LENGTH	6
 46#define SHT4X_CRC8_POLYNOMIAL	0x31
 47#define SHT4X_CRC8_INIT		0xff
 48#define SHT4X_MIN_TEMPERATURE	-45000
 49#define SHT4X_MAX_TEMPERATURE	125000
 50#define SHT4X_MIN_HUMIDITY	0
 51#define SHT4X_MAX_HUMIDITY	100000
 52
 53DECLARE_CRC8_TABLE(sht4x_crc8_table);
 54
 55/**
 56 * struct sht4x_data - All the data required to operate an SHT4X chip
 57 * @client: the i2c client associated with the SHT4X
 58 * @heating_complete: the time that the last heating finished
 59 * @data_pending: true if and only if there are measurements to retrieve after heating
 60 * @heater_power: the power at which the heater will be started
 61 * @heater_time: the time for which the heater will remain turned on
 62 * @valid: validity of fields below
 63 * @update_interval: the minimum poll interval
 64 * @last_updated: the previous time that the SHT4X was polled
 65 * @temperature: the latest temperature value received from the SHT4X
 66 * @humidity: the latest humidity value received from the SHT4X
 67 */
 68struct sht4x_data {
 69	struct i2c_client	*client;
 70	unsigned long		heating_complete;	/* in jiffies */
 71	bool			data_pending;
 72	u32			heater_power;	/* in milli-watts */
 73	u32			heater_time;	/* in milli-seconds */
 74	bool			valid;	/* validity of fields below */
 75	long			update_interval;	/* in milli-seconds */
 76	long			last_updated;	/* in jiffies */
 77	s32			temperature;
 78	s32			humidity;
 79};
 80
 81/**
 82 * sht4x_read_values() - read and parse the raw data from the SHT4X
 83 * @data: the struct sht4x_data to use for the lock
 84 * Return: 0 if successful, -ERRNO if not
 85 */
 86static int sht4x_read_values(struct sht4x_data *data)
 87{
 88	int ret;
 89	u16 t_ticks, rh_ticks;
 90	unsigned long next_update;
 91	struct i2c_client *client = data->client;
 92	u8 crc;
 93	u8 cmd[SHT4X_CMD_LEN] = {SHT4X_CMD_MEASURE_HPM};
 94	u8 raw_data[SHT4X_RESPONSE_LENGTH];
 95	unsigned long curr_jiffies;
 96
 97	curr_jiffies = jiffies;
 98	if (time_before(curr_jiffies, data->heating_complete))
 99		msleep(jiffies_to_msecs(data->heating_complete - curr_jiffies));
100
101	if (data->data_pending &&
102	    time_before(jiffies, data->heating_complete + data->update_interval)) {
103		data->data_pending = false;
104	} else {
105		next_update = data->last_updated +
106			msecs_to_jiffies(data->update_interval);
107
108		if (data->valid && time_before_eq(jiffies, next_update))
109			return 0;
110
111		ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
112		if (ret < 0)
113			return ret;
114
115		usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA);
116	}
117
118	ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
119	if (ret != SHT4X_RESPONSE_LENGTH) {
120		if (ret >= 0)
121			ret = -ENODATA;
122		return ret;
123	}
124
125	t_ticks = raw_data[0] << 8 | raw_data[1];
126	rh_ticks = raw_data[3] << 8 | raw_data[4];
127
128	crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
129	if (crc != raw_data[2]) {
130		dev_err(&client->dev, "data integrity check failed\n");
131		return -EIO;
132	}
133
134	crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
135	if (crc != raw_data[5]) {
136		dev_err(&client->dev, "data integrity check failed\n");
137		return -EIO;
138	}
139
140	data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
141	data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
142	data->last_updated = jiffies;
143	data->valid = true;
144	return 0;
145}
146
147static ssize_t sht4x_interval_write(struct sht4x_data *data, long val)
148{
149	data->update_interval = clamp_val(val, SHT4X_MIN_POLL_INTERVAL, INT_MAX);
150
151	return 0;
152}
153
154/* sht4x_interval_read() - read the minimum poll interval in milliseconds */
155static size_t sht4x_interval_read(struct sht4x_data *data, long *val)
156{
157	*val = data->update_interval;
158	return 0;
159}
160
161/* sht4x_temperature1_read() - read the temperature in millidegrees */
162static int sht4x_temperature1_read(struct sht4x_data *data, long *val)
163{
164	int ret;
165
166	ret = sht4x_read_values(data);
167	if (ret < 0)
168		return ret;
169
170	*val = data->temperature;
171
172	return 0;
173}
174
175/* sht4x_humidity1_read() - read a relative humidity in millipercent */
176static int sht4x_humidity1_read(struct sht4x_data *data, long *val)
177{
178	int ret;
179
180	ret = sht4x_read_values(data);
181	if (ret < 0)
182		return ret;
183
184	*val = data->humidity;
185
186	return 0;
187}
188
189static umode_t sht4x_hwmon_visible(const void *data,
190				   enum hwmon_sensor_types type,
191				   u32 attr, int channel)
192{
193	switch (type) {
194	case hwmon_temp:
195	case hwmon_humidity:
196		return 0444;
197	case hwmon_chip:
198		return 0644;
199	default:
200		return 0;
201	}
202}
203
204static int sht4x_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
205			    u32 attr, int channel, long *val)
206{
207	struct sht4x_data *data = dev_get_drvdata(dev);
208
209	switch (type) {
210	case hwmon_temp:
211		return sht4x_temperature1_read(data, val);
212	case hwmon_humidity:
213		return sht4x_humidity1_read(data, val);
214	case hwmon_chip:
215		return sht4x_interval_read(data, val);
216	default:
217		return -EOPNOTSUPP;
218	}
219}
220
221static int sht4x_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
222			     u32 attr, int channel, long val)
223{
224	struct sht4x_data *data = dev_get_drvdata(dev);
225
226	switch (type) {
227	case hwmon_chip:
228		return sht4x_interval_write(data, val);
229	default:
230		return -EOPNOTSUPP;
231	}
232}
233
234static ssize_t heater_enable_show(struct device *dev,
235				  struct device_attribute *attr,
236				  char *buf)
237{
238	struct sht4x_data *data = dev_get_drvdata(dev);
239
240	return sysfs_emit(buf, "%u\n", time_before(jiffies, data->heating_complete));
241}
242
243static ssize_t heater_enable_store(struct device *dev,
244				   struct device_attribute *attr,
245				   const char *buf,
246				   size_t count)
247{
248	struct sht4x_data *data = dev_get_drvdata(dev);
249	bool status;
250	ssize_t ret;
251	u8 cmd;
252	u32 heating_time_bound;
253
254	ret = kstrtobool(buf, &status);
255	if (ret)
256		return ret;
257	if (!status)
258		return -EINVAL;
259
260	if (data->heater_time == 100) {
261		if (data->heater_power == 20)
262			cmd = SHT4X_CMD_HEATER_20_01;
263		else if (data->heater_power == 110)
264			cmd = SHT4X_CMD_HEATER_110_01;
265		else /* data->heater_power == 200 */
266			cmd = SHT4X_CMD_HEATER_200_01;
267
268		heating_time_bound = 110;
269	} else { /* data->heater_time == 1000 */
270		if (data->heater_power == 20)
271			cmd = SHT4X_CMD_HEATER_20_1;
272		else if (data->heater_power == 110)
273			cmd = SHT4X_CMD_HEATER_110_1;
274		else /* data->heater_power == 200 */
275			cmd = SHT4X_CMD_HEATER_200_1;
276
277		heating_time_bound = 1100;
278	}
279
280	if (time_before(jiffies, data->heating_complete))
281		return -EBUSY;
282
283	ret = i2c_master_send(data->client, &cmd, SHT4X_CMD_LEN);
284	if (ret < 0)
285		return ret;
286
287	data->heating_complete = jiffies + msecs_to_jiffies(heating_time_bound);
288	data->data_pending = true;
289	return 0;
290}
291
292static ssize_t heater_power_show(struct device *dev,
293				 struct device_attribute *attr,
294				 char *buf)
295{
296	struct sht4x_data *data = dev_get_drvdata(dev);
297
298	return sysfs_emit(buf, "%u\n", data->heater_power);
299}
300
301static ssize_t heater_power_store(struct device *dev,
302				  struct device_attribute *attr,
303				  const char *buf,
304				  size_t count)
305{
306	struct sht4x_data *data = dev_get_drvdata(dev);
307	u32 power;
308	ssize_t ret;
309
310	ret = kstrtou32(buf, 10, &power);
311	if (ret)
312		return ret;
313
314	if (power != 20 && power != 110 && power != 200)
315		return -EINVAL;
316
317	data->heater_power = power;
318
319	return count;
320}
321
322static ssize_t heater_time_show(struct device *dev,
323				struct device_attribute *attr,
324				char *buf)
325{
326	struct sht4x_data *data = dev_get_drvdata(dev);
327
328	return sysfs_emit(buf, "%u\n", data->heater_time);
329}
330
331static ssize_t heater_time_store(struct device *dev,
332				 struct device_attribute *attr,
333				 const char *buf,
334				 size_t count)
335{
336	struct sht4x_data *data = dev_get_drvdata(dev);
337	u32 time;
338	ssize_t ret;
339
340	ret = kstrtou32(buf, 10, &time);
341	if (ret)
342		return ret;
343
344	if (time != 100 && time != 1000)
345		return -EINVAL;
346
347	data->heater_time = time;
348
349	return count;
350}
351
352static DEVICE_ATTR_RW(heater_enable);
353static DEVICE_ATTR_RW(heater_power);
354static DEVICE_ATTR_RW(heater_time);
355
356static struct attribute *sht4x_attrs[] = {
357	&dev_attr_heater_enable.attr,
358	&dev_attr_heater_power.attr,
359	&dev_attr_heater_time.attr,
360	NULL
361};
362
363ATTRIBUTE_GROUPS(sht4x);
364
365static const struct hwmon_channel_info * const sht4x_info[] = {
366	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
367	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
368	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
369	NULL,
370};
371
372static const struct hwmon_ops sht4x_hwmon_ops = {
373	.is_visible = sht4x_hwmon_visible,
374	.read = sht4x_hwmon_read,
375	.write = sht4x_hwmon_write,
376};
377
378static const struct hwmon_chip_info sht4x_chip_info = {
379	.ops = &sht4x_hwmon_ops,
380	.info = sht4x_info,
381};
382
383static int sht4x_probe(struct i2c_client *client)
384{
385	struct device *device = &client->dev;
386	struct device *hwmon_dev;
387	struct sht4x_data *data;
388	u8 cmd[] = {SHT4X_CMD_RESET};
389	int ret;
390
391	/*
392	 * we require full i2c support since the sht4x uses multi-byte read and
393	 * writes as well as multi-byte commands which are not supported by
394	 * the smbus protocol
395	 */
396	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
397		return -EOPNOTSUPP;
398
399	data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
400	if (!data)
401		return -ENOMEM;
402
403	data->update_interval = SHT4X_MIN_POLL_INTERVAL;
404	data->client = client;
405	data->heater_power = 200;
406	data->heater_time = 1000;
407	data->heating_complete = jiffies;
408
409	crc8_populate_msb(sht4x_crc8_table, SHT4X_CRC8_POLYNOMIAL);
410
411	ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
412	if (ret < 0)
413		return ret;
414	if (ret != SHT4X_CMD_LEN)
415		return -EIO;
416
417	hwmon_dev = devm_hwmon_device_register_with_info(device,
418							 client->name,
419							 data,
420							 &sht4x_chip_info,
421							 sht4x_groups);
422
423	return PTR_ERR_OR_ZERO(hwmon_dev);
424}
425
426static const struct i2c_device_id sht4x_id[] = {
427	{ "sht4x" },
428	{ },
429};
430MODULE_DEVICE_TABLE(i2c, sht4x_id);
431
432static const struct of_device_id sht4x_of_match[] = {
433	{ .compatible = "sensirion,sht4x" },
434	{ }
435};
436MODULE_DEVICE_TABLE(of, sht4x_of_match);
437
438static struct i2c_driver sht4x_driver = {
439	.driver = {
440		.name = "sht4x",
441		.of_match_table = sht4x_of_match,
442	},
443	.probe		= sht4x_probe,
444	.id_table	= sht4x_id,
445};
446
447module_i2c_driver(sht4x_driver);
448
449MODULE_AUTHOR("Navin Sankar Velliangiri <navin@linumiz.com>");
450MODULE_DESCRIPTION("Sensirion SHT4x humidity and temperature sensor driver");
451MODULE_LICENSE("GPL v2");