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(msecs: jiffies_to_msecs(j: 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(m: data->update_interval);
107
108 if (data->valid && time_before_eq(jiffies, next_update))
109 return 0;
110
111 ret = i2c_master_send(client, buf: 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, buf: 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(table: sht4x_crc8_table, pdata: &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(table: sht4x_crc8_table, pdata: &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, fmt: "%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(s: buf, res: &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(client: data->client, buf: &cmd, SHT4X_CMD_LEN);
284 if (ret < 0)
285 return ret;
286
287 data->heating_complete = jiffies + msecs_to_jiffies(m: 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, fmt: "%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(s: buf, base: 10, res: &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, fmt: "%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(s: buf, base: 10, res: &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(adap: client->adapter, I2C_FUNC_I2C))
397 return -EOPNOTSUPP;
398
399 data = devm_kzalloc(dev: device, size: 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(table: sht4x_crc8_table, SHT4X_CRC8_POLYNOMIAL);
410
411 ret = i2c_master_send(client, buf: 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(dev: device,
418 name: client->name,
419 drvdata: data,
420 info: &sht4x_chip_info,
421 extra_groups: sht4x_groups);
422
423 return PTR_ERR_OR_ZERO(ptr: 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");
452

source code of linux/drivers/hwmon/sht4x.c