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505c2549 NSV |
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/i2c.h> | |
15 | #include <linux/jiffies.h> | |
16 | #include <linux/module.h> | |
17 | ||
18 | /* | |
19 | * Poll intervals (in milliseconds) | |
20 | */ | |
21 | #define SHT4X_MIN_POLL_INTERVAL 2000 | |
22 | ||
23 | /* | |
24 | * I2C command delays (in microseconds) | |
25 | */ | |
0e4190d7 | 26 | #define SHT4X_MEAS_DELAY_HPM 8200 /* see t_MEAS,h in datasheet */ |
505c2549 NSV |
27 | #define SHT4X_DELAY_EXTRA 10000 |
28 | ||
29 | /* | |
30 | * Command Bytes | |
31 | */ | |
32 | #define SHT4X_CMD_MEASURE_HPM 0b11111101 | |
33 | #define SHT4X_CMD_RESET 0b10010100 | |
34 | ||
35 | #define SHT4X_CMD_LEN 1 | |
36 | #define SHT4X_CRC8_LEN 1 | |
37 | #define SHT4X_WORD_LEN 2 | |
38 | #define SHT4X_RESPONSE_LENGTH 6 | |
39 | #define SHT4X_CRC8_POLYNOMIAL 0x31 | |
40 | #define SHT4X_CRC8_INIT 0xff | |
41 | #define SHT4X_MIN_TEMPERATURE -45000 | |
42 | #define SHT4X_MAX_TEMPERATURE 125000 | |
43 | #define SHT4X_MIN_HUMIDITY 0 | |
44 | #define SHT4X_MAX_HUMIDITY 100000 | |
45 | ||
46 | DECLARE_CRC8_TABLE(sht4x_crc8_table); | |
47 | ||
48 | /** | |
49 | * struct sht4x_data - All the data required to operate an SHT4X chip | |
50 | * @client: the i2c client associated with the SHT4X | |
51 | * @lock: a mutex that is used to prevent parallel access to the i2c client | |
10bd80e0 | 52 | * @valid: validity of fields below |
505c2549 NSV |
53 | * @update_interval: the minimum poll interval |
54 | * @last_updated: the previous time that the SHT4X was polled | |
55 | * @temperature: the latest temperature value received from the SHT4X | |
56 | * @humidity: the latest humidity value received from the SHT4X | |
57 | */ | |
58 | struct sht4x_data { | |
59 | struct i2c_client *client; | |
60 | struct mutex lock; /* atomic read data updates */ | |
61 | bool valid; /* validity of fields below */ | |
62 | long update_interval; /* in milli-seconds */ | |
63 | long last_updated; /* in jiffies */ | |
64 | s32 temperature; | |
65 | s32 humidity; | |
66 | }; | |
67 | ||
68 | /** | |
69 | * sht4x_read_values() - read and parse the raw data from the SHT4X | |
10bd80e0 | 70 | * @data: the struct sht4x_data to use for the lock |
07c6621a | 71 | * Return: 0 if successful, -ERRNO if not |
505c2549 NSV |
72 | */ |
73 | static int sht4x_read_values(struct sht4x_data *data) | |
74 | { | |
75 | int ret = 0; | |
76 | u16 t_ticks, rh_ticks; | |
77 | unsigned long next_update; | |
78 | struct i2c_client *client = data->client; | |
07c6621a JP |
79 | u8 crc; |
80 | u8 cmd[SHT4X_CMD_LEN] = {SHT4X_CMD_MEASURE_HPM}; | |
81 | u8 raw_data[SHT4X_RESPONSE_LENGTH]; | |
505c2549 NSV |
82 | |
83 | mutex_lock(&data->lock); | |
84 | next_update = data->last_updated + | |
85 | msecs_to_jiffies(data->update_interval); | |
07c6621a JP |
86 | |
87 | if (data->valid && time_before_eq(jiffies, next_update)) | |
88 | goto unlock; | |
89 | ||
90 | ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN); | |
91 | if (ret < 0) | |
92 | goto unlock; | |
93 | ||
0e4190d7 | 94 | usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA); |
07c6621a JP |
95 | |
96 | ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH); | |
97 | if (ret != SHT4X_RESPONSE_LENGTH) { | |
98 | if (ret >= 0) | |
99 | ret = -ENODATA; | |
100 | goto unlock; | |
505c2549 NSV |
101 | } |
102 | ||
07c6621a JP |
103 | t_ticks = raw_data[0] << 8 | raw_data[1]; |
104 | rh_ticks = raw_data[3] << 8 | raw_data[4]; | |
105 | ||
106 | crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE); | |
107 | if (crc != raw_data[2]) { | |
108 | dev_err(&client->dev, "data integrity check failed\n"); | |
109 | ret = -EIO; | |
110 | goto unlock; | |
111 | } | |
112 | ||
113 | crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE); | |
114 | if (crc != raw_data[5]) { | |
115 | dev_err(&client->dev, "data integrity check failed\n"); | |
116 | ret = -EIO; | |
117 | goto unlock; | |
118 | } | |
119 | ||
120 | data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000; | |
121 | data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000; | |
122 | data->last_updated = jiffies; | |
123 | data->valid = true; | |
124 | ret = 0; | |
125 | ||
505c2549 NSV |
126 | unlock: |
127 | mutex_unlock(&data->lock); | |
128 | return ret; | |
129 | } | |
130 | ||
131 | static ssize_t sht4x_interval_write(struct sht4x_data *data, long val) | |
132 | { | |
f9c0cf8f | 133 | data->update_interval = clamp_val(val, SHT4X_MIN_POLL_INTERVAL, INT_MAX); |
505c2549 NSV |
134 | |
135 | return 0; | |
136 | } | |
137 | ||
07c6621a | 138 | /* sht4x_interval_read() - read the minimum poll interval in milliseconds */ |
505c2549 NSV |
139 | static size_t sht4x_interval_read(struct sht4x_data *data, long *val) |
140 | { | |
141 | *val = data->update_interval; | |
142 | return 0; | |
143 | } | |
144 | ||
07c6621a | 145 | /* sht4x_temperature1_read() - read the temperature in millidegrees */ |
505c2549 NSV |
146 | static int sht4x_temperature1_read(struct sht4x_data *data, long *val) |
147 | { | |
148 | int ret; | |
149 | ||
150 | ret = sht4x_read_values(data); | |
151 | if (ret < 0) | |
152 | return ret; | |
153 | ||
154 | *val = data->temperature; | |
155 | ||
156 | return 0; | |
157 | } | |
158 | ||
07c6621a | 159 | /* sht4x_humidity1_read() - read a relative humidity in millipercent */ |
505c2549 NSV |
160 | static int sht4x_humidity1_read(struct sht4x_data *data, long *val) |
161 | { | |
162 | int ret; | |
163 | ||
164 | ret = sht4x_read_values(data); | |
165 | if (ret < 0) | |
166 | return ret; | |
167 | ||
168 | *val = data->humidity; | |
169 | ||
170 | return 0; | |
171 | } | |
172 | ||
173 | static umode_t sht4x_hwmon_visible(const void *data, | |
174 | enum hwmon_sensor_types type, | |
175 | u32 attr, int channel) | |
176 | { | |
177 | switch (type) { | |
178 | case hwmon_temp: | |
179 | case hwmon_humidity: | |
180 | return 0444; | |
181 | case hwmon_chip: | |
182 | return 0644; | |
183 | default: | |
184 | return 0; | |
185 | } | |
186 | } | |
187 | ||
188 | static int sht4x_hwmon_read(struct device *dev, enum hwmon_sensor_types type, | |
189 | u32 attr, int channel, long *val) | |
190 | { | |
191 | struct sht4x_data *data = dev_get_drvdata(dev); | |
192 | ||
193 | switch (type) { | |
194 | case hwmon_temp: | |
195 | return sht4x_temperature1_read(data, val); | |
196 | case hwmon_humidity: | |
197 | return sht4x_humidity1_read(data, val); | |
198 | case hwmon_chip: | |
199 | return sht4x_interval_read(data, val); | |
200 | default: | |
201 | return -EOPNOTSUPP; | |
202 | } | |
203 | } | |
204 | ||
205 | static int sht4x_hwmon_write(struct device *dev, enum hwmon_sensor_types type, | |
206 | u32 attr, int channel, long val) | |
207 | { | |
208 | struct sht4x_data *data = dev_get_drvdata(dev); | |
209 | ||
210 | switch (type) { | |
211 | case hwmon_chip: | |
212 | return sht4x_interval_write(data, val); | |
213 | default: | |
214 | return -EOPNOTSUPP; | |
215 | } | |
216 | } | |
217 | ||
11c1dff5 | 218 | static const struct hwmon_channel_info * const sht4x_info[] = { |
505c2549 NSV |
219 | HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), |
220 | HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), | |
221 | HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), | |
222 | NULL, | |
223 | }; | |
224 | ||
225 | static const struct hwmon_ops sht4x_hwmon_ops = { | |
226 | .is_visible = sht4x_hwmon_visible, | |
227 | .read = sht4x_hwmon_read, | |
228 | .write = sht4x_hwmon_write, | |
229 | }; | |
230 | ||
231 | static const struct hwmon_chip_info sht4x_chip_info = { | |
232 | .ops = &sht4x_hwmon_ops, | |
233 | .info = sht4x_info, | |
234 | }; | |
235 | ||
deeab9ea | 236 | static int sht4x_probe(struct i2c_client *client) |
505c2549 NSV |
237 | { |
238 | struct device *device = &client->dev; | |
239 | struct device *hwmon_dev; | |
240 | struct sht4x_data *data; | |
241 | u8 cmd[] = {SHT4X_CMD_RESET}; | |
242 | int ret; | |
243 | ||
244 | /* | |
245 | * we require full i2c support since the sht4x uses multi-byte read and | |
246 | * writes as well as multi-byte commands which are not supported by | |
247 | * the smbus protocol | |
248 | */ | |
249 | if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) | |
250 | return -EOPNOTSUPP; | |
251 | ||
252 | data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); | |
253 | if (!data) | |
254 | return -ENOMEM; | |
255 | ||
256 | data->update_interval = SHT4X_MIN_POLL_INTERVAL; | |
257 | data->client = client; | |
258 | ||
259 | mutex_init(&data->lock); | |
260 | ||
261 | crc8_populate_msb(sht4x_crc8_table, SHT4X_CRC8_POLYNOMIAL); | |
262 | ||
263 | ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN); | |
264 | if (ret < 0) | |
265 | return ret; | |
266 | if (ret != SHT4X_CMD_LEN) | |
267 | return -EIO; | |
268 | ||
269 | hwmon_dev = devm_hwmon_device_register_with_info(device, | |
270 | client->name, | |
271 | data, | |
272 | &sht4x_chip_info, | |
273 | NULL); | |
274 | ||
275 | return PTR_ERR_OR_ZERO(hwmon_dev); | |
276 | } | |
277 | ||
278 | static const struct i2c_device_id sht4x_id[] = { | |
d8a66f36 | 279 | { "sht4x" }, |
505c2549 NSV |
280 | { }, |
281 | }; | |
282 | MODULE_DEVICE_TABLE(i2c, sht4x_id); | |
283 | ||
62cfc057 DMT |
284 | static const struct of_device_id sht4x_of_match[] = { |
285 | { .compatible = "sensirion,sht4x" }, | |
286 | { } | |
287 | }; | |
288 | MODULE_DEVICE_TABLE(of, sht4x_of_match); | |
289 | ||
505c2549 NSV |
290 | static struct i2c_driver sht4x_driver = { |
291 | .driver = { | |
292 | .name = "sht4x", | |
62cfc057 | 293 | .of_match_table = sht4x_of_match, |
505c2549 | 294 | }, |
1975d167 | 295 | .probe = sht4x_probe, |
505c2549 NSV |
296 | .id_table = sht4x_id, |
297 | }; | |
298 | ||
299 | module_i2c_driver(sht4x_driver); | |
300 | ||
301 | MODULE_AUTHOR("Navin Sankar Velliangiri <navin@linumiz.com>"); | |
302 | MODULE_DESCRIPTION("Sensirion SHT4x humidity and temperature sensor driver"); | |
303 | MODULE_LICENSE("GPL v2"); |