1 // SPDX-License-Identifier: GPL-2.0-only 2 3 /* 4 * aht10.c - Linux hwmon driver for AHT10 Temperature and Humidity sensor 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 14 #define AHT10_MEAS_SIZE 6 15 16 /* 17 * Poll intervals (in milliseconds) 18 */ 19 #define AHT10_DEFAULT_MIN_POLL_INTERVAL 2000 20 #define AHT10_MIN_POLL_INTERVAL 2000 21 22 /* 23 * I2C command delays (in microseconds) 24 */ 25 #define AHT10_MEAS_DELAY 80000 26 #define AHT10_CMD_DELAY 350000 27 #define AHT10_DELAY_EXTRA 100000 28 29 /* 30 * Command bytes 31 */ 32 #define AHT10_CMD_INIT 0b11100001 33 #define AHT10_CMD_MEAS 0b10101100 34 #define AHT10_CMD_RST 0b10111010 35 36 /* 37 * Flags in the answer byte/command 38 */ 39 #define AHT10_CAL_ENABLED BIT(3) 40 #define AHT10_BUSY BIT(7) 41 #define AHT10_MODE_NOR (BIT(5) | BIT(6)) 42 #define AHT10_MODE_CYC BIT(5) 43 #define AHT10_MODE_CMD BIT(6) 44 45 #define AHT10_MAX_POLL_INTERVAL_LEN 30 46 47 /** 48 * struct aht10_data - All the data required to operate an AHT10 chip 49 * @client: the i2c client associated with the AHT10 50 * @lock: a mutex that is used to prevent parallel access to the 51 * i2c client 52 * @min_poll_interval: the minimum poll interval 53 * While the poll rate limit is not 100% necessary, 54 * the datasheet recommends that a measurement 55 * is not performed too often to prevent 56 * the chip from warming up due to the heat it generates. 57 * If it's unwanted, it can be ignored setting it to 58 * it to 0. Default value is 2000 ms 59 * @previous_poll_time: the previous time that the AHT10 60 * was polled 61 * @temperature: the latest temperature value received from 62 * the AHT10 63 * @humidity: the latest humidity value received from the 64 * AHT10 65 */ 66 67 struct aht10_data { 68 struct i2c_client *client; 69 /* 70 * Prevent simultaneous access to the i2c 71 * client and previous_poll_time 72 */ 73 struct mutex lock; 74 ktime_t min_poll_interval; 75 ktime_t previous_poll_time; 76 int temperature; 77 int humidity; 78 }; 79 80 /** 81 * aht10_init() - Initialize an AHT10 chip 82 * @data: the data associated with this AHT10 chip 83 * Return: 0 if successful, 1 if not 84 */ 85 static int aht10_init(struct aht10_data *data) 86 { 87 const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC, 88 0x00}; 89 int res; 90 u8 status; 91 struct i2c_client *client = data->client; 92 93 res = i2c_master_send(client, cmd_init, 3); 94 if (res < 0) 95 return res; 96 97 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY + 98 AHT10_DELAY_EXTRA); 99 100 res = i2c_master_recv(client, &status, 1); 101 if (res != 1) 102 return -ENODATA; 103 104 if (status & AHT10_BUSY) 105 return -EBUSY; 106 107 return 0; 108 } 109 110 /** 111 * aht10_polltime_expired() - check if the minimum poll interval has 112 * expired 113 * @data: the data containing the time to compare 114 * Return: 1 if the minimum poll interval has expired, 0 if not 115 */ 116 static int aht10_polltime_expired(struct aht10_data *data) 117 { 118 ktime_t current_time = ktime_get_boottime(); 119 ktime_t difference = ktime_sub(current_time, data->previous_poll_time); 120 121 return ktime_after(difference, data->min_poll_interval); 122 } 123 124 /** 125 * aht10_read_values() - read and parse the raw data from the AHT10 126 * @data: the struct aht10_data to use for the lock 127 * Return: 0 if successful, 1 if not 128 */ 129 static int aht10_read_values(struct aht10_data *data) 130 { 131 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00}; 132 u32 temp, hum; 133 int res; 134 u8 raw_data[AHT10_MEAS_SIZE]; 135 struct i2c_client *client = data->client; 136 137 mutex_lock(&data->lock); 138 if (!aht10_polltime_expired(data)) { 139 mutex_unlock(&data->lock); 140 return 0; 141 } 142 143 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); 144 if (res < 0) { 145 mutex_unlock(&data->lock); 146 return res; 147 } 148 149 usleep_range(AHT10_MEAS_DELAY, AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); 150 151 res = i2c_master_recv(client, raw_data, AHT10_MEAS_SIZE); 152 if (res != AHT10_MEAS_SIZE) { 153 mutex_unlock(&data->lock); 154 if (res >= 0) 155 return -ENODATA; 156 return res; 157 } 158 159 hum = ((u32)raw_data[1] << 12u) | 160 ((u32)raw_data[2] << 4u) | 161 ((raw_data[3] & 0xF0u) >> 4u); 162 163 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | 164 ((u32)raw_data[4] << 8u) | 165 raw_data[5]; 166 167 temp = ((temp * 625) >> 15u) * 10; 168 hum = ((hum * 625) >> 16u) * 10; 169 170 data->temperature = (int)temp - 50000; 171 data->humidity = hum; 172 data->previous_poll_time = ktime_get_boottime(); 173 174 mutex_unlock(&data->lock); 175 return 0; 176 } 177 178 /** 179 * aht10_interval_write() - store the given minimum poll interval. 180 * Return: 0 on success, -EINVAL if a value lower than the 181 * AHT10_MIN_POLL_INTERVAL is given 182 */ 183 static ssize_t aht10_interval_write(struct aht10_data *data, 184 long val) 185 { 186 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX)); 187 return 0; 188 } 189 190 /** 191 * aht10_interval_read() - read the minimum poll interval 192 * in milliseconds 193 */ 194 static ssize_t aht10_interval_read(struct aht10_data *data, 195 long *val) 196 { 197 *val = ktime_to_ms(data->min_poll_interval); 198 return 0; 199 } 200 201 /** 202 * aht10_temperature1_read() - read the temperature in millidegrees 203 */ 204 static int aht10_temperature1_read(struct aht10_data *data, long *val) 205 { 206 int res; 207 208 res = aht10_read_values(data); 209 if (res < 0) 210 return res; 211 212 *val = data->temperature; 213 return 0; 214 } 215 216 /** 217 * aht10_humidity1_read() - read the relative humidity in millipercent 218 */ 219 static int aht10_humidity1_read(struct aht10_data *data, long *val) 220 { 221 int res; 222 223 res = aht10_read_values(data); 224 if (res < 0) 225 return res; 226 227 *val = data->humidity; 228 return 0; 229 } 230 231 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type, 232 u32 attr, int channel) 233 { 234 switch (type) { 235 case hwmon_temp: 236 case hwmon_humidity: 237 return 0444; 238 case hwmon_chip: 239 return 0644; 240 default: 241 return 0; 242 } 243 } 244 245 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type, 246 u32 attr, int channel, long *val) 247 { 248 struct aht10_data *data = dev_get_drvdata(dev); 249 250 switch (type) { 251 case hwmon_temp: 252 return aht10_temperature1_read(data, val); 253 case hwmon_humidity: 254 return aht10_humidity1_read(data, val); 255 case hwmon_chip: 256 return aht10_interval_read(data, val); 257 default: 258 return -EOPNOTSUPP; 259 } 260 } 261 262 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type, 263 u32 attr, int channel, long val) 264 { 265 struct aht10_data *data = dev_get_drvdata(dev); 266 267 switch (type) { 268 case hwmon_chip: 269 return aht10_interval_write(data, val); 270 default: 271 return -EOPNOTSUPP; 272 } 273 } 274 275 static const struct hwmon_channel_info * const aht10_info[] = { 276 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), 277 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), 278 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), 279 NULL, 280 }; 281 282 static const struct hwmon_ops aht10_hwmon_ops = { 283 .is_visible = aht10_hwmon_visible, 284 .read = aht10_hwmon_read, 285 .write = aht10_hwmon_write, 286 }; 287 288 static const struct hwmon_chip_info aht10_chip_info = { 289 .ops = &aht10_hwmon_ops, 290 .info = aht10_info, 291 }; 292 293 static int aht10_probe(struct i2c_client *client) 294 { 295 struct device *device = &client->dev; 296 struct device *hwmon_dev; 297 struct aht10_data *data; 298 int res; 299 300 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 301 return -ENOENT; 302 303 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); 304 if (!data) 305 return -ENOMEM; 306 307 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); 308 data->client = client; 309 310 mutex_init(&data->lock); 311 312 res = aht10_init(data); 313 if (res < 0) 314 return res; 315 316 res = aht10_read_values(data); 317 if (res < 0) 318 return res; 319 320 hwmon_dev = devm_hwmon_device_register_with_info(device, 321 client->name, 322 data, 323 &aht10_chip_info, 324 NULL); 325 326 return PTR_ERR_OR_ZERO(hwmon_dev); 327 } 328 329 static const struct i2c_device_id aht10_id[] = { 330 { "aht10", 0 }, 331 { }, 332 }; 333 MODULE_DEVICE_TABLE(i2c, aht10_id); 334 335 static struct i2c_driver aht10_driver = { 336 .driver = { 337 .name = "aht10", 338 }, 339 .probe = aht10_probe, 340 .id_table = aht10_id, 341 }; 342 343 module_i2c_driver(aht10_driver); 344 345 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>"); 346 MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver"); 347 MODULE_VERSION("1.0"); 348 MODULE_LICENSE("GPL v2"); 349