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 /* 41 * Flags in the answer byte/command 42 */ 43 #define AHT10_CAL_ENABLED BIT(3) 44 #define AHT10_BUSY BIT(7) 45 #define AHT10_MODE_NOR (BIT(5) | BIT(6)) 46 #define AHT10_MODE_CYC BIT(5) 47 #define AHT10_MODE_CMD BIT(6) 48 49 #define AHT10_MAX_POLL_INTERVAL_LEN 30 50 51 enum aht10_variant { aht10, aht20 }; 52 53 static const struct i2c_device_id aht10_id[] = { 54 { "aht10", aht10 }, 55 { "aht20", aht20 }, 56 { }, 57 }; 58 MODULE_DEVICE_TABLE(i2c, aht10_id); 59 60 /** 61 * struct aht10_data - All the data required to operate an AHT10/AHT20 chip 62 * @client: the i2c client associated with the AHT10/AHT20 63 * @lock: a mutex that is used to prevent parallel access to the 64 * i2c client 65 * @min_poll_interval: the minimum poll interval 66 * While the poll rate limit is not 100% necessary, 67 * the datasheet recommends that a measurement 68 * is not performed too often to prevent 69 * the chip from warming up due to the heat it generates. 70 * If it's unwanted, it can be ignored setting it to 71 * it to 0. Default value is 2000 ms 72 * @previous_poll_time: the previous time that the AHT10/AHT20 73 * was polled 74 * @temperature: the latest temperature value received from 75 * the AHT10/AHT20 76 * @humidity: the latest humidity value received from the 77 * AHT10/AHT20 78 * @crc8: crc8 support flag 79 * @meas_size: measurements data size 80 */ 81 82 struct aht10_data { 83 struct i2c_client *client; 84 /* 85 * Prevent simultaneous access to the i2c 86 * client and previous_poll_time 87 */ 88 struct mutex lock; 89 ktime_t min_poll_interval; 90 ktime_t previous_poll_time; 91 int temperature; 92 int humidity; 93 bool crc8; 94 unsigned int meas_size; 95 }; 96 97 /** 98 * aht10_init() - Initialize an AHT10/AHT20 chip 99 * @data: the data associated with this AHT10/AHT20 chip 100 * Return: 0 if successful, 1 if not 101 */ 102 static int aht10_init(struct aht10_data *data) 103 { 104 const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC, 105 0x00}; 106 int res; 107 u8 status; 108 struct i2c_client *client = data->client; 109 110 res = i2c_master_send(client, cmd_init, 3); 111 if (res < 0) 112 return res; 113 114 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY + 115 AHT10_DELAY_EXTRA); 116 117 res = i2c_master_recv(client, &status, 1); 118 if (res != 1) 119 return -ENODATA; 120 121 if (status & AHT10_BUSY) 122 return -EBUSY; 123 124 return 0; 125 } 126 127 /** 128 * aht10_polltime_expired() - check if the minimum poll interval has 129 * expired 130 * @data: the data containing the time to compare 131 * Return: 1 if the minimum poll interval has expired, 0 if not 132 */ 133 static int aht10_polltime_expired(struct aht10_data *data) 134 { 135 ktime_t current_time = ktime_get_boottime(); 136 ktime_t difference = ktime_sub(current_time, data->previous_poll_time); 137 138 return ktime_after(difference, data->min_poll_interval); 139 } 140 141 DECLARE_CRC8_TABLE(crc8_table); 142 143 /** 144 * crc8_check() - check crc of the sensor's measurements 145 * @raw_data: data frame received from sensor(including crc as the last byte) 146 * @count: size of the data frame 147 * Return: 0 if successful, 1 if not 148 */ 149 static int crc8_check(u8 *raw_data, int count) 150 { 151 /* 152 * crc calculated on the whole frame(including crc byte) should yield 153 * zero in case of correctly received bytes 154 */ 155 return crc8(crc8_table, raw_data, count, CRC8_INIT_VALUE); 156 } 157 158 /** 159 * aht10_read_values() - read and parse the raw data from the AHT10/AHT20 160 * @data: the struct aht10_data to use for the lock 161 * Return: 0 if successful, 1 if not 162 */ 163 static int aht10_read_values(struct aht10_data *data) 164 { 165 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00}; 166 u32 temp, hum; 167 int res; 168 u8 raw_data[AHT20_MEAS_SIZE]; 169 struct i2c_client *client = data->client; 170 171 mutex_lock(&data->lock); 172 if (!aht10_polltime_expired(data)) { 173 mutex_unlock(&data->lock); 174 return 0; 175 } 176 177 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); 178 if (res < 0) { 179 mutex_unlock(&data->lock); 180 return res; 181 } 182 183 usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); 184 185 res = i2c_master_recv(client, raw_data, data->meas_size); 186 if (res != data->meas_size) { 187 mutex_unlock(&data->lock); 188 if (res >= 0) 189 return -ENODATA; 190 return res; 191 } 192 193 if (data->crc8 && crc8_check(raw_data, data->meas_size)) { 194 mutex_unlock(&data->lock); 195 return -EIO; 196 } 197 198 hum = ((u32)raw_data[1] << 12u) | 199 ((u32)raw_data[2] << 4u) | 200 ((raw_data[3] & 0xF0u) >> 4u); 201 202 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | 203 ((u32)raw_data[4] << 8u) | 204 raw_data[5]; 205 206 temp = ((temp * 625) >> 15u) * 10; 207 hum = ((hum * 625) >> 16u) * 10; 208 209 data->temperature = (int)temp - 50000; 210 data->humidity = hum; 211 data->previous_poll_time = ktime_get_boottime(); 212 213 mutex_unlock(&data->lock); 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 const struct i2c_device_id *id = i2c_match_id(aht10_id, client); 335 enum aht10_variant variant = id->driver_data; 336 struct device *device = &client->dev; 337 struct device *hwmon_dev; 338 struct aht10_data *data; 339 int res; 340 341 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 342 return -ENOENT; 343 344 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); 345 if (!data) 346 return -ENOMEM; 347 348 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); 349 data->client = client; 350 351 switch (variant) { 352 case aht20: 353 data->meas_size = AHT20_MEAS_SIZE; 354 data->crc8 = true; 355 crc8_populate_msb(crc8_table, AHT20_CRC8_POLY); 356 break; 357 default: 358 data->meas_size = AHT10_MEAS_SIZE; 359 break; 360 } 361 362 mutex_init(&data->lock); 363 364 res = aht10_init(data); 365 if (res < 0) 366 return res; 367 368 res = aht10_read_values(data); 369 if (res < 0) 370 return res; 371 372 hwmon_dev = devm_hwmon_device_register_with_info(device, 373 client->name, 374 data, 375 &aht10_chip_info, 376 NULL); 377 378 return PTR_ERR_OR_ZERO(hwmon_dev); 379 } 380 381 static struct i2c_driver aht10_driver = { 382 .driver = { 383 .name = "aht10", 384 }, 385 .probe = aht10_probe, 386 .id_table = aht10_id, 387 }; 388 389 module_i2c_driver(aht10_driver); 390 391 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>"); 392 MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver"); 393 MODULE_VERSION("1.0"); 394 MODULE_LICENSE("GPL v2"); 395