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 succesfull, 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 succesfull, 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 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); 140 if (res < 0) { 141 mutex_unlock(&data->lock); 142 return res; 143 } 144 145 usleep_range(AHT10_MEAS_DELAY, 146 AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); 147 148 res = i2c_master_recv(client, raw_data, AHT10_MEAS_SIZE); 149 if (res != AHT10_MEAS_SIZE) { 150 mutex_unlock(&data->lock); 151 if (res >= 0) 152 return -ENODATA; 153 else 154 return res; 155 } 156 157 hum = ((u32)raw_data[1] << 12u) | 158 ((u32)raw_data[2] << 4u) | 159 ((raw_data[3] & 0xF0u) >> 4u); 160 161 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | 162 ((u32)raw_data[4] << 8u) | 163 raw_data[5]; 164 165 temp = ((temp * 625) >> 15u) * 10; 166 hum = ((hum * 625) >> 16u) * 10; 167 168 data->temperature = (int)temp - 50000; 169 data->humidity = hum; 170 data->previous_poll_time = ktime_get_boottime(); 171 } 172 mutex_unlock(&data->lock); 173 return 0; 174 } 175 176 /** 177 * aht10_interval_write() - store the given minimum poll interval. 178 * Return: 0 on success, -EINVAL if a value lower than the 179 * AHT10_MIN_POLL_INTERVAL is given 180 */ 181 static ssize_t aht10_interval_write(struct aht10_data *data, 182 long val) 183 { 184 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX)); 185 return 0; 186 } 187 188 /** 189 * aht10_interval_read() - read the minimum poll interval 190 * in milliseconds 191 */ 192 static ssize_t aht10_interval_read(struct aht10_data *data, 193 long *val) 194 { 195 *val = ktime_to_ms(data->min_poll_interval); 196 return 0; 197 } 198 199 /** 200 * aht10_temperature1_read() - read the temperature in millidegrees 201 */ 202 static int aht10_temperature1_read(struct aht10_data *data, long *val) 203 { 204 int res; 205 206 res = aht10_read_values(data); 207 if (res < 0) 208 return res; 209 210 *val = data->temperature; 211 return 0; 212 } 213 214 /** 215 * aht10_humidity1_read() - read the relative humidity in millipercent 216 */ 217 static int aht10_humidity1_read(struct aht10_data *data, long *val) 218 { 219 int res; 220 221 res = aht10_read_values(data); 222 if (res < 0) 223 return res; 224 225 *val = data->humidity; 226 return 0; 227 } 228 229 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type, 230 u32 attr, int channel) 231 { 232 switch (type) { 233 case hwmon_temp: 234 case hwmon_humidity: 235 return 0444; 236 case hwmon_chip: 237 return 0644; 238 default: 239 return 0; 240 } 241 } 242 243 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type, 244 u32 attr, int channel, long *val) 245 { 246 struct aht10_data *data = dev_get_drvdata(dev); 247 248 switch (type) { 249 case hwmon_temp: 250 return aht10_temperature1_read(data, val); 251 case hwmon_humidity: 252 return aht10_humidity1_read(data, val); 253 case hwmon_chip: 254 return aht10_interval_read(data, val); 255 default: 256 return -EOPNOTSUPP; 257 } 258 } 259 260 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type, 261 u32 attr, int channel, long val) 262 { 263 struct aht10_data *data = dev_get_drvdata(dev); 264 265 switch (type) { 266 case hwmon_chip: 267 return aht10_interval_write(data, val); 268 default: 269 return -EOPNOTSUPP; 270 } 271 } 272 273 static const struct hwmon_channel_info *aht10_info[] = { 274 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), 275 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), 276 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), 277 NULL, 278 }; 279 280 static const struct hwmon_ops aht10_hwmon_ops = { 281 .is_visible = aht10_hwmon_visible, 282 .read = aht10_hwmon_read, 283 .write = aht10_hwmon_write, 284 }; 285 286 static const struct hwmon_chip_info aht10_chip_info = { 287 .ops = &aht10_hwmon_ops, 288 .info = aht10_info, 289 }; 290 291 static int aht10_probe(struct i2c_client *client) 292 { 293 struct device *device = &client->dev; 294 struct device *hwmon_dev; 295 struct aht10_data *data; 296 int res; 297 298 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 299 return -ENOENT; 300 301 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); 302 if (!data) 303 return -ENOMEM; 304 305 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); 306 data->client = client; 307 308 mutex_init(&data->lock); 309 310 res = aht10_init(data); 311 if (res < 0) 312 return res; 313 314 res = aht10_read_values(data); 315 if (res < 0) 316 return res; 317 318 hwmon_dev = devm_hwmon_device_register_with_info(device, 319 client->name, 320 data, 321 &aht10_chip_info, 322 NULL); 323 324 return PTR_ERR_OR_ZERO(hwmon_dev); 325 } 326 327 static const struct i2c_device_id aht10_id[] = { 328 { "aht10", 0 }, 329 { }, 330 }; 331 MODULE_DEVICE_TABLE(i2c, aht10_id); 332 333 static struct i2c_driver aht10_driver = { 334 .driver = { 335 .name = "aht10", 336 }, 337 .probe_new = aht10_probe, 338 .id_table = aht10_id, 339 }; 340 341 module_i2c_driver(aht10_driver); 342 343 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>"); 344 MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver"); 345 MODULE_VERSION("1.0"); 346 MODULE_LICENSE("GPL v2"); 347