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 AHT20_CMD_INIT 0b10111110 41 42 #define DHT20_CMD_INIT 0b01110001 43 44 /* 45 * Flags in the answer byte/command 46 */ 47 #define AHT10_CAL_ENABLED BIT(3) 48 #define AHT10_BUSY BIT(7) 49 #define AHT10_MODE_NOR (BIT(5) | BIT(6)) 50 #define AHT10_MODE_CYC BIT(5) 51 #define AHT10_MODE_CMD BIT(6) 52 53 #define AHT10_MAX_POLL_INTERVAL_LEN 30 54 55 enum aht10_variant { aht10, aht20, dht20}; 56 57 static const struct i2c_device_id aht10_id[] = { 58 { "aht10", aht10 }, 59 { "aht20", aht20 }, 60 { "dht20", dht20 }, 61 { }, 62 }; 63 MODULE_DEVICE_TABLE(i2c, aht10_id); 64 65 static const struct of_device_id aht10_of_match[] = { 66 { .compatible = "aosong,aht10", .data = (void *)aht10 }, 67 { .compatible = "aosong,aht20", .data = (void *)aht20 }, 68 { .compatible = "aosong,dht20", .data = (void *)dht20 }, 69 {} 70 }; 71 72 MODULE_DEVICE_TABLE(of, aht10_of_match); 73 74 /** 75 * struct aht10_data - All the data required to operate an AHT10/AHT20 chip 76 * @client: the i2c client associated with the AHT10/AHT20 77 * @min_poll_interval: the minimum poll interval 78 * While the poll rate limit is not 100% necessary, 79 * the datasheet recommends that a measurement 80 * is not performed too often to prevent 81 * the chip from warming up due to the heat it generates. 82 * If it's unwanted, it can be ignored setting it to 83 * it to 0. Default value is 2000 ms 84 * @previous_poll_time: the previous time that the AHT10/AHT20 85 * was polled 86 * @temperature: the latest temperature value received from 87 * the AHT10/AHT20 88 * @humidity: the latest humidity value received from the 89 * AHT10/AHT20 90 * @crc8: crc8 support flag 91 * @meas_size: measurements data size 92 * @init_cmd: Initialization command 93 */ 94 95 struct aht10_data { 96 struct i2c_client *client; 97 ktime_t min_poll_interval; 98 ktime_t previous_poll_time; 99 int temperature; 100 int humidity; 101 bool crc8; 102 unsigned int meas_size; 103 u8 init_cmd; 104 }; 105 106 /* 107 * aht10_init() - Initialize an AHT10/AHT20 chip 108 * @data: the data associated with this AHT10/AHT20 chip 109 * Return: 0 if successful, 1 if not 110 */ 111 static int aht10_init(struct aht10_data *data) 112 { 113 const u8 cmd_init[] = {data->init_cmd, AHT10_CAL_ENABLED | AHT10_MODE_CYC, 114 0x00}; 115 int res; 116 u8 status; 117 struct i2c_client *client = data->client; 118 119 res = i2c_master_send(client, cmd_init, sizeof(cmd_init)); 120 if (res < 0) 121 return res; 122 123 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY + 124 AHT10_DELAY_EXTRA); 125 126 res = i2c_master_recv(client, &status, 1); 127 if (res != 1) 128 return -ENODATA; 129 130 if (status & AHT10_BUSY) 131 return -EBUSY; 132 133 return 0; 134 } 135 136 /* 137 * aht10_polltime_expired() - check if the minimum poll interval has 138 * expired 139 * @data: the data containing the time to compare 140 * Return: 1 if the minimum poll interval has expired, 0 if not 141 */ 142 static int aht10_polltime_expired(struct aht10_data *data) 143 { 144 ktime_t current_time = ktime_get_boottime(); 145 ktime_t difference = ktime_sub(current_time, data->previous_poll_time); 146 147 return ktime_after(difference, data->min_poll_interval); 148 } 149 150 DECLARE_CRC8_TABLE(crc8_table); 151 152 /* 153 * crc8_check() - check crc of the sensor's measurements 154 * @raw_data: data frame received from sensor(including crc as the last byte) 155 * @count: size of the data frame 156 * Return: 0 if successful, 1 if not 157 */ 158 static int crc8_check(u8 *raw_data, int count) 159 { 160 /* 161 * crc calculated on the whole frame(including crc byte) should yield 162 * zero in case of correctly received bytes 163 */ 164 return crc8(crc8_table, raw_data, count, CRC8_INIT_VALUE); 165 } 166 167 /* 168 * aht10_read_values() - read and parse the raw data from the AHT10/AHT20 169 * @data: the struct aht10_data to use for the lock 170 * Return: 0 if successful, 1 if not 171 */ 172 static int aht10_read_values(struct aht10_data *data) 173 { 174 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00}; 175 u32 temp, hum; 176 int res; 177 u8 raw_data[AHT20_MEAS_SIZE]; 178 struct i2c_client *client = data->client; 179 180 if (!aht10_polltime_expired(data)) 181 return 0; 182 183 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); 184 if (res < 0) 185 return res; 186 187 usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); 188 189 res = i2c_master_recv(client, raw_data, data->meas_size); 190 if (res != data->meas_size) { 191 if (res >= 0) 192 return -ENODATA; 193 return res; 194 } 195 196 if (data->crc8 && crc8_check(raw_data, data->meas_size)) 197 return -EIO; 198 199 hum = ((u32)raw_data[1] << 12u) | 200 ((u32)raw_data[2] << 4u) | 201 ((raw_data[3] & 0xF0u) >> 4u); 202 203 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | 204 ((u32)raw_data[4] << 8u) | 205 raw_data[5]; 206 207 temp = ((temp * 625) >> 15u) * 10; 208 hum = ((hum * 625) >> 16u) * 10; 209 210 data->temperature = (int)temp - 50000; 211 data->humidity = hum; 212 data->previous_poll_time = ktime_get_boottime(); 213 214 return 0; 215 } 216 217 /* 218 * aht10_interval_write() - store the given minimum poll interval. 219 * Return: 0 on success, -EINVAL if a value lower than the 220 * AHT10_MIN_POLL_INTERVAL is given 221 */ 222 static ssize_t aht10_interval_write(struct aht10_data *data, 223 long val) 224 { 225 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX)); 226 return 0; 227 } 228 229 /* 230 * aht10_interval_read() - read the minimum poll interval 231 * in milliseconds 232 */ 233 static ssize_t aht10_interval_read(struct aht10_data *data, 234 long *val) 235 { 236 *val = ktime_to_ms(data->min_poll_interval); 237 return 0; 238 } 239 240 /* 241 * aht10_temperature1_read() - read the temperature in millidegrees 242 */ 243 static int aht10_temperature1_read(struct aht10_data *data, long *val) 244 { 245 int res; 246 247 res = aht10_read_values(data); 248 if (res < 0) 249 return res; 250 251 *val = data->temperature; 252 return 0; 253 } 254 255 /* 256 * aht10_humidity1_read() - read the relative humidity in millipercent 257 */ 258 static int aht10_humidity1_read(struct aht10_data *data, long *val) 259 { 260 int res; 261 262 res = aht10_read_values(data); 263 if (res < 0) 264 return res; 265 266 *val = data->humidity; 267 return 0; 268 } 269 270 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type, 271 u32 attr, int channel) 272 { 273 switch (type) { 274 case hwmon_temp: 275 case hwmon_humidity: 276 return 0444; 277 case hwmon_chip: 278 return 0644; 279 default: 280 return 0; 281 } 282 } 283 284 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type, 285 u32 attr, int channel, long *val) 286 { 287 struct aht10_data *data = dev_get_drvdata(dev); 288 289 switch (type) { 290 case hwmon_temp: 291 return aht10_temperature1_read(data, val); 292 case hwmon_humidity: 293 return aht10_humidity1_read(data, val); 294 case hwmon_chip: 295 return aht10_interval_read(data, val); 296 default: 297 return -EOPNOTSUPP; 298 } 299 } 300 301 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type, 302 u32 attr, int channel, long val) 303 { 304 struct aht10_data *data = dev_get_drvdata(dev); 305 306 switch (type) { 307 case hwmon_chip: 308 return aht10_interval_write(data, val); 309 default: 310 return -EOPNOTSUPP; 311 } 312 } 313 314 static const struct hwmon_channel_info * const aht10_info[] = { 315 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), 316 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), 317 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), 318 NULL, 319 }; 320 321 static const struct hwmon_ops aht10_hwmon_ops = { 322 .is_visible = aht10_hwmon_visible, 323 .read = aht10_hwmon_read, 324 .write = aht10_hwmon_write, 325 }; 326 327 static const struct hwmon_chip_info aht10_chip_info = { 328 .ops = &aht10_hwmon_ops, 329 .info = aht10_info, 330 }; 331 332 static int aht10_probe(struct i2c_client *client) 333 { 334 enum aht10_variant variant = (uintptr_t)i2c_get_match_data(client); 335 struct device *device = &client->dev; 336 struct device *hwmon_dev; 337 struct aht10_data *data; 338 int res; 339 340 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 341 return -ENOENT; 342 343 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); 344 if (!data) 345 return -ENOMEM; 346 347 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); 348 data->client = client; 349 350 switch (variant) { 351 case aht20: 352 data->meas_size = AHT20_MEAS_SIZE; 353 data->crc8 = true; 354 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY); 355 data->init_cmd = AHT20_CMD_INIT; 356 break; 357 case dht20: 358 data->meas_size = AHT20_MEAS_SIZE; 359 data->crc8 = true; 360 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY); 361 data->init_cmd = DHT20_CMD_INIT; 362 break; 363 default: 364 data->meas_size = AHT10_MEAS_SIZE; 365 data->init_cmd = AHT10_CMD_INIT; 366 break; 367 } 368 369 res = aht10_init(data); 370 if (res < 0) 371 return res; 372 373 res = aht10_read_values(data); 374 if (res < 0) 375 return res; 376 377 hwmon_dev = devm_hwmon_device_register_with_info(device, 378 client->name, 379 data, 380 &aht10_chip_info, 381 NULL); 382 383 return PTR_ERR_OR_ZERO(hwmon_dev); 384 } 385 386 static struct i2c_driver aht10_driver = { 387 .driver = { 388 .name = "aht10", 389 .of_match_table = aht10_of_match, 390 }, 391 .probe = aht10_probe, 392 .id_table = aht10_id, 393 }; 394 395 module_i2c_driver(aht10_driver); 396 397 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>"); 398 MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver"); 399 MODULE_VERSION("1.0"); 400 MODULE_LICENSE("GPL v2"); 401