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 * @client: the i2c client associated with the AHT10 83 * @data: the data associated with this AHT10 chip 84 * Return: 0 if succesfull, 1 if not 85 */ 86 static int aht10_init(struct aht10_data *data) 87 { 88 const u8 cmd_init[] = {AHT10_CMD_INIT, AHT10_CAL_ENABLED | AHT10_MODE_CYC, 89 0x00}; 90 int res; 91 u8 status; 92 struct i2c_client *client = data->client; 93 94 res = i2c_master_send(client, cmd_init, 3); 95 if (res < 0) 96 return res; 97 98 usleep_range(AHT10_CMD_DELAY, AHT10_CMD_DELAY + 99 AHT10_DELAY_EXTRA); 100 101 res = i2c_master_recv(client, &status, 1); 102 if (res != 1) 103 return -ENODATA; 104 105 if (status & AHT10_BUSY) 106 return -EBUSY; 107 108 return 0; 109 } 110 111 /** 112 * aht10_polltime_expired() - check if the minimum poll interval has 113 * expired 114 * @data: the data containing the time to compare 115 * Return: 1 if the minimum poll interval has expired, 0 if not 116 */ 117 static int aht10_polltime_expired(struct aht10_data *data) 118 { 119 ktime_t current_time = ktime_get_boottime(); 120 ktime_t difference = ktime_sub(current_time, data->previous_poll_time); 121 122 return ktime_after(difference, data->min_poll_interval); 123 } 124 125 /** 126 * aht10_read_values() - read and parse the raw data from the AHT10 127 * @aht10_data: the struct aht10_data to use for the lock 128 * Return: 0 if succesfull, 1 if not 129 */ 130 static int aht10_read_values(struct aht10_data *data) 131 { 132 const u8 cmd_meas[] = {AHT10_CMD_MEAS, 0x33, 0x00}; 133 u32 temp, hum; 134 int res; 135 u8 raw_data[AHT10_MEAS_SIZE]; 136 struct i2c_client *client = data->client; 137 138 mutex_lock(&data->lock); 139 if (aht10_polltime_expired(data)) { 140 res = i2c_master_send(client, cmd_meas, sizeof(cmd_meas)); 141 if (res < 0) { 142 mutex_unlock(&data->lock); 143 return res; 144 } 145 146 usleep_range(AHT10_MEAS_DELAY, 147 AHT10_MEAS_DELAY + AHT10_DELAY_EXTRA); 148 149 res = i2c_master_recv(client, raw_data, AHT10_MEAS_SIZE); 150 if (res != AHT10_MEAS_SIZE) { 151 mutex_unlock(&data->lock); 152 if (res >= 0) 153 return -ENODATA; 154 else 155 return res; 156 } 157 158 hum = ((u32)raw_data[1] << 12u) | 159 ((u32)raw_data[2] << 4u) | 160 ((raw_data[3] & 0xF0u) >> 4u); 161 162 temp = ((u32)(raw_data[3] & 0x0Fu) << 16u) | 163 ((u32)raw_data[4] << 8u) | 164 raw_data[5]; 165 166 temp = ((temp * 625) >> 15u) * 10; 167 hum = ((hum * 625) >> 16u) * 10; 168 169 data->temperature = (int)temp - 50000; 170 data->humidity = hum; 171 data->previous_poll_time = ktime_get_boottime(); 172 } 173 mutex_unlock(&data->lock); 174 return 0; 175 } 176 177 /** 178 * aht10_interval_write() - store the given minimum poll interval. 179 * Return: 0 on success, -EINVAL if a value lower than the 180 * AHT10_MIN_POLL_INTERVAL is given 181 */ 182 static ssize_t aht10_interval_write(struct aht10_data *data, 183 long val) 184 { 185 data->min_poll_interval = ms_to_ktime(clamp_val(val, 2000, LONG_MAX)); 186 return 0; 187 } 188 189 /** 190 * aht10_interval_read() - read the minimum poll interval 191 * in milliseconds 192 */ 193 static ssize_t aht10_interval_read(struct aht10_data *data, 194 long *val) 195 { 196 *val = ktime_to_ms(data->min_poll_interval); 197 return 0; 198 } 199 200 /** 201 * aht10_temperature1_read() - read the temperature in millidegrees 202 */ 203 static int aht10_temperature1_read(struct aht10_data *data, long *val) 204 { 205 int res; 206 207 res = aht10_read_values(data); 208 if (res < 0) 209 return res; 210 211 *val = data->temperature; 212 return 0; 213 } 214 215 /** 216 * aht10_humidity1_read() - read the relative humidity in millipercent 217 */ 218 static int aht10_humidity1_read(struct aht10_data *data, long *val) 219 { 220 int res; 221 222 res = aht10_read_values(data); 223 if (res < 0) 224 return res; 225 226 *val = data->humidity; 227 return 0; 228 } 229 230 static umode_t aht10_hwmon_visible(const void *data, enum hwmon_sensor_types type, 231 u32 attr, int channel) 232 { 233 switch (type) { 234 case hwmon_temp: 235 case hwmon_humidity: 236 return 0444; 237 case hwmon_chip: 238 return 0644; 239 default: 240 return 0; 241 } 242 } 243 244 static int aht10_hwmon_read(struct device *dev, enum hwmon_sensor_types type, 245 u32 attr, int channel, long *val) 246 { 247 struct aht10_data *data = dev_get_drvdata(dev); 248 249 switch (type) { 250 case hwmon_temp: 251 return aht10_temperature1_read(data, val); 252 case hwmon_humidity: 253 return aht10_humidity1_read(data, val); 254 case hwmon_chip: 255 return aht10_interval_read(data, val); 256 default: 257 return -EOPNOTSUPP; 258 } 259 } 260 261 static int aht10_hwmon_write(struct device *dev, enum hwmon_sensor_types type, 262 u32 attr, int channel, long val) 263 { 264 struct aht10_data *data = dev_get_drvdata(dev); 265 266 switch (type) { 267 case hwmon_chip: 268 return aht10_interval_write(data, val); 269 default: 270 return -EOPNOTSUPP; 271 } 272 } 273 274 static const struct hwmon_channel_info *aht10_info[] = { 275 HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), 276 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT), 277 HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT), 278 NULL, 279 }; 280 281 static const struct hwmon_ops aht10_hwmon_ops = { 282 .is_visible = aht10_hwmon_visible, 283 .read = aht10_hwmon_read, 284 .write = aht10_hwmon_write, 285 }; 286 287 static const struct hwmon_chip_info aht10_chip_info = { 288 .ops = &aht10_hwmon_ops, 289 .info = aht10_info, 290 }; 291 292 static int aht10_probe(struct i2c_client *client) 293 { 294 struct device *device = &client->dev; 295 struct device *hwmon_dev; 296 struct aht10_data *data; 297 int res; 298 299 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 300 return -ENOENT; 301 302 data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL); 303 if (!data) 304 return -ENOMEM; 305 306 data->min_poll_interval = ms_to_ktime(AHT10_DEFAULT_MIN_POLL_INTERVAL); 307 data->client = client; 308 309 mutex_init(&data->lock); 310 311 res = aht10_init(data); 312 if (res < 0) 313 return res; 314 315 res = aht10_read_values(data); 316 if (res < 0) 317 return res; 318 319 hwmon_dev = devm_hwmon_device_register_with_info(device, 320 client->name, 321 data, 322 &aht10_chip_info, 323 NULL); 324 325 return PTR_ERR_OR_ZERO(hwmon_dev); 326 } 327 328 static const struct i2c_device_id aht10_id[] = { 329 { "aht10", 0 }, 330 { }, 331 }; 332 MODULE_DEVICE_TABLE(i2c, aht10_id); 333 334 static struct i2c_driver aht10_driver = { 335 .driver = { 336 .name = "aht10", 337 }, 338 .probe_new = aht10_probe, 339 .id_table = aht10_id, 340 }; 341 342 module_i2c_driver(aht10_driver); 343 344 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>"); 345 MODULE_DESCRIPTION("AHT10 Temperature and Humidity sensor driver"); 346 MODULE_VERSION("1.0"); 347 MODULE_LICENSE("GPL v2"); 348