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 DHT20_CMD_INIT 0x71 41 42 /* 43 * Flags in the answer byte/command 44 */ 45 #define AHT10_CAL_ENABLED BIT(3) 46 #define AHT10_BUSY BIT(7) 47 #define AHT10_MODE_NOR (BIT(5) | BIT(6)) 48 #define AHT10_MODE_CYC BIT(5) 49 #define AHT10_MODE_CMD BIT(6) 50 51 #define AHT10_MAX_POLL_INTERVAL_LEN 30 52 53 enum aht10_variant { aht10, aht20, dht20}; 54 55 static const struct i2c_device_id aht10_id[] = { 56 { "aht10", aht10 }, 57 { "aht20", aht20 }, 58 { "dht20", dht20 }, 59 { }, 60 }; 61 MODULE_DEVICE_TABLE(i2c, aht10_id); 62 63 /** 64 * struct aht10_data - All the data required to operate an AHT10/AHT20 chip 65 * @client: the i2c client associated with the AHT10/AHT20 66 * @min_poll_interval: the minimum poll interval 67 * While the poll rate limit is not 100% necessary, 68 * the datasheet recommends that a measurement 69 * is not performed too often to prevent 70 * the chip from warming up due to the heat it generates. 71 * If it's unwanted, it can be ignored setting it to 72 * it to 0. Default value is 2000 ms 73 * @previous_poll_time: the previous time that the AHT10/AHT20 74 * was polled 75 * @temperature: the latest temperature value received from 76 * the AHT10/AHT20 77 * @humidity: the latest humidity value received from the 78 * AHT10/AHT20 79 * @crc8: crc8 support flag 80 * @meas_size: measurements data size 81 * @init_cmd: Initialization command 82 */ 83 84 struct aht10_data { 85 struct i2c_client *client; 86 ktime_t min_poll_interval; 87 ktime_t previous_poll_time; 88 int temperature; 89 int humidity; 90 bool crc8; 91 unsigned int meas_size; 92 u8 init_cmd; 93 }; 94 95 /* 96 * aht10_init() - Initialize an AHT10/AHT20 chip 97 * @data: the data associated with this AHT10/AHT20 chip 98 * Return: 0 if successful, 1 if not 99 */ 100 static int aht10_init(struct aht10_data *data) 101 { 102 const u8 cmd_init[] = {data->init_cmd, AHT10_CAL_ENABLED | AHT10_MODE_CYC, 103 0x00}; 104 int res; 105 u8 status; 106 struct i2c_client *client = data->client; 107 108 res = i2c_master_send(client, cmd_init, sizeof(cmd_init)); 109 if (res < 0) 110 return res; 111 112 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY + 113 AHT10_DELAY_EXTRA); 114 115 res = i2c_master_recv(client, &status, 1); 116 if (res != 1) 117 return -ENODATA; 118 119 if (status & AHT10_BUSY) 120 return -EBUSY; 121 122 return 0; 123 } 124 125 /* 126 * aht10_polltime_expired() - check if the minimum poll interval has 127 * expired 128 * @data: the data containing the time to compare 129 * Return: 1 if the minimum poll interval has expired, 0 if not 130 */ 131 static int aht10_polltime_expired(struct aht10_data *data) 132 { 133 ktime_t current_time = ktime_get_boottime(); 134 ktime_t difference = ktime_sub(current_time, data->previous_poll_time); 135 136 return ktime_after(difference, data->min_poll_interval); 137 } 138 139 DECLARE_CRC8_TABLE(crc8_table); 140 141 /* 142 * crc8_check() - check crc of the sensor's measurements 143 * @raw_data: data frame received from sensor(including crc as the last byte) 144 * @count: size of the data frame 145 * Return: 0 if successful, 1 if not 146 */ 147 static int crc8_check(u8 *raw_data, int count) 148 { 149 /* 150 * crc calculated on the whole frame(including crc byte) should yield 151 * zero in case of correctly received bytes 152 */ 153 return crc8(crc8_table, raw_data, count, CRC8_INIT_VALUE); 154 } 155 156 /* 157 * aht10_read_values() - read and parse the raw data from the AHT10/AHT20 158 * @data: the struct aht10_data to use for the lock 159 * Return: 0 if successful, 1 if not 160 */ 161 static int aht10_read_values(struct aht10_data *data) 162 { 163 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00}; 164 u32 temp, hum; 165 int res; 166 u8 raw_data[AHT20_MEAS_SIZE]; 167 struct i2c_client *client = data->client; 168 169 if (!aht10_polltime_expired(data)) 170 return 0; 171 172 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); 173 if (res < 0) 174 return res; 175 176 usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); 177 178 res = i2c_master_recv(client, raw_data, data->meas_size); 179 if (res != data->meas_size) { 180 if (res >= 0) 181 return -ENODATA; 182 return res; 183 } 184 185 if (data->crc8 && crc8_check(raw_data, data->meas_size)) 186 return -EIO; 187 188 hum = ((u32)raw_data[1] << 12u) | 189 ((u32)raw_data[2] << 4u) | 190 ((raw_data[3] & 0xF0u) >> 4u); 191 192 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | 193 ((u32)raw_data[4] << 8u) | 194 raw_data[5]; 195 196 temp = ((temp * 625) >> 15u) * 10; 197 hum = ((hum * 625) >> 16u) * 10; 198 199 data->temperature = (int)temp - 50000; 200 data->humidity = hum; 201 data->previous_poll_time = ktime_get_boottime(); 202 203 return 0; 204 } 205 206 /* 207 * aht10_interval_write() - store the given minimum poll interval. 208 * Return: 0 on success, -EINVAL if a value lower than the 209 * AHT10_MIN_POLL_INTERVAL is given 210 */ 211 static ssize_t aht10_interval_write(struct aht10_data *data, 212 long val) 213 { 214 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX)); 215 return 0; 216 } 217 218 /* 219 * aht10_interval_read() - read the minimum poll interval 220 * in milliseconds 221 */ 222 static ssize_t aht10_interval_read(struct aht10_data *data, 223 long *val) 224 { 225 *val = ktime_to_ms(data->min_poll_interval); 226 return 0; 227 } 228 229 /* 230 * aht10_temperature1_read() - read the temperature in millidegrees 231 */ 232 static int aht10_temperature1_read(struct aht10_data *data, long *val) 233 { 234 int res; 235 236 res = aht10_read_values(data); 237 if (res < 0) 238 return res; 239 240 *val = data->temperature; 241 return 0; 242 } 243 244 /* 245 * aht10_humidity1_read() - read the relative humidity in millipercent 246 */ 247 static int aht10_humidity1_read(struct aht10_data *data, long *val) 248 { 249 int res; 250 251 res = aht10_read_values(data); 252 if (res < 0) 253 return res; 254 255 *val = data->humidity; 256 return 0; 257 } 258 259 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type, 260 u32 attr, int channel) 261 { 262 switch (type) { 263 case hwmon_temp: 264 case hwmon_humidity: 265 return 0444; 266 case hwmon_chip: 267 return 0644; 268 default: 269 return 0; 270 } 271 } 272 273 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type, 274 u32 attr, int channel, long *val) 275 { 276 struct aht10_data *data = dev_get_drvdata(dev); 277 278 switch (type) { 279 case hwmon_temp: 280 return aht10_temperature1_read(data, val); 281 case hwmon_humidity: 282 return aht10_humidity1_read(data, val); 283 case hwmon_chip: 284 return aht10_interval_read(data, val); 285 default: 286 return -EOPNOTSUPP; 287 } 288 } 289 290 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type, 291 u32 attr, int channel, long val) 292 { 293 struct aht10_data *data = dev_get_drvdata(dev); 294 295 switch (type) { 296 case hwmon_chip: 297 return aht10_interval_write(data, val); 298 default: 299 return -EOPNOTSUPP; 300 } 301 } 302 303 static const struct hwmon_channel_info * const aht10_info[] = { 304 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), 305 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), 306 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), 307 NULL, 308 }; 309 310 static const struct hwmon_ops aht10_hwmon_ops = { 311 .is_visible = aht10_hwmon_visible, 312 .read = aht10_hwmon_read, 313 .write = aht10_hwmon_write, 314 }; 315 316 static const struct hwmon_chip_info aht10_chip_info = { 317 .ops = &aht10_hwmon_ops, 318 .info = aht10_info, 319 }; 320 321 static int aht10_probe(struct i2c_client *client) 322 { 323 enum aht10_variant variant = (uintptr_t)i2c_get_match_data(client); 324 struct device *device = &client->dev; 325 struct device *hwmon_dev; 326 struct aht10_data *data; 327 int res; 328 329 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 330 return -ENOENT; 331 332 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); 333 if (!data) 334 return -ENOMEM; 335 336 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); 337 data->client = client; 338 339 switch (variant) { 340 case aht20: 341 data->meas_size = AHT20_MEAS_SIZE; 342 data->crc8 = true; 343 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY); 344 data->init_cmd = AHT10_CMD_INIT; 345 break; 346 case dht20: 347 data->meas_size = AHT20_MEAS_SIZE; 348 data->crc8 = true; 349 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY); 350 data->init_cmd = DHT20_CMD_INIT; 351 break; 352 default: 353 data->meas_size = AHT10_MEAS_SIZE; 354 data->init_cmd = AHT10_CMD_INIT; 355 break; 356 } 357 358 res = aht10_init(data); 359 if (res < 0) 360 return res; 361 362 res = aht10_read_values(data); 363 if (res < 0) 364 return res; 365 366 hwmon_dev = devm_hwmon_device_register_with_info(device, 367 client->name, 368 data, 369 &aht10_chip_info, 370 NULL); 371 372 return PTR_ERR_OR_ZERO(hwmon_dev); 373 } 374 375 static struct i2c_driver aht10_driver = { 376 .driver = { 377 .name = "aht10", 378 }, 379 .probe = aht10_probe, 380 .id_table = aht10_id, 381 }; 382 383 module_i2c_driver(aht10_driver); 384 385 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>"); 386 MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver"); 387 MODULE_VERSION("1.0"); 388 MODULE_LICENSE("GPL v2"); 389