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 */ 26 #define SHT4X_MEAS_DELAY_HPM 8200 /* see t_MEAS,h in datasheet */ 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 52 * @valid: validity of fields below 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 70 * @data: the struct sht4x_data to use for the lock 71 * Return: 0 if successful, -ERRNO if not 72 */ sht4x_read_values(struct sht4x_data * data)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; 79 u8 crc; 80 u8 cmd[SHT4X_CMD_LEN] = {SHT4X_CMD_MEASURE_HPM}; 81 u8 raw_data[SHT4X_RESPONSE_LENGTH]; 82 83 mutex_lock(&data->lock); 84 next_update = data->last_updated + 85 msecs_to_jiffies(data->update_interval); 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 94 usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA); 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; 101 } 102 103 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; 125 126 unlock: 127 mutex_unlock(&data->lock); 128 return ret; 129 } 130 sht4x_interval_write(struct sht4x_data * data,long val)131 static ssize_t sht4x_interval_write(struct sht4x_data *data, long val) 132 { 133 data->update_interval = clamp_val(val, SHT4X_MIN_POLL_INTERVAL, INT_MAX); 134 135 return 0; 136 } 137 138 /* sht4x_interval_read() - read the minimum poll interval in milliseconds */ sht4x_interval_read(struct sht4x_data * data,long * val)139 static size_t sht4x_interval_read(struct sht4x_data *data, long *val) 140 { 141 *val = data->update_interval; 142 return 0; 143 } 144 145 /* sht4x_temperature1_read() - read the temperature in millidegrees */ sht4x_temperature1_read(struct sht4x_data * data,long * val)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 } 158 159 /* sht4x_humidity1_read() - read a relative humidity in millipercent */ sht4x_humidity1_read(struct sht4x_data * data,long * val)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 sht4x_hwmon_visible(const void * data,enum hwmon_sensor_types type,u32 attr,int channel)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 sht4x_hwmon_read(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long * val)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 sht4x_hwmon_write(struct device * dev,enum hwmon_sensor_types type,u32 attr,int channel,long val)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 } 217 218 static const struct hwmon_channel_info * const sht4x_info[] = { 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 sht4x_probe(struct i2c_client * client)236 static int sht4x_probe(struct i2c_client *client) 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[] = { 279 { "sht4x" }, 280 { }, 281 }; 282 MODULE_DEVICE_TABLE(i2c, sht4x_id); 283 284 static const struct of_device_id sht4x_of_match[] = { 285 { .compatible = "sensirion,sht4x" }, 286 { } 287 }; 288 MODULE_DEVICE_TABLE(of, sht4x_of_match); 289 290 static struct i2c_driver sht4x_driver = { 291 .driver = { 292 .name = "sht4x", 293 .of_match_table = sht4x_of_match, 294 }, 295 .probe = sht4x_probe, 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"); 304