drivers/hwmon/aht10.c

   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         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                 break;
 356         default:
 357                 data->meas_size = AHT10_MEAS_SIZE;
 358                 break;
 359         }
 360
 361         mutex_init(&data->lock);
 362
 363         res = aht10_init(data);
 364         if (res < 0)
 365                 return res;
 366
 367         res = aht10_read_values(data);
 368         if (res < 0)
 369                 return res;
 370
 371         hwmon_dev = devm_hwmon_device_register_with_info(device,
 372                                                          client->name,
 373                                                          data,
 374                                                          &aht10_chip_info,
 375                                                          NULL);
 376
 377         return PTR_ERR_OR_ZERO(hwmon_dev);
 378 }
 379
 380 static struct i2c_driver aht10_driver = {
 381         .driver = {
 382                 .name = "aht10",
 383         },
 384         .probe      = aht10_probe,
 385         .id_table   = aht10_id,
 386 };
 387
 388 module_i2c_driver(aht10_driver);
 389
 390 MODULE_AUTHOR("Johannes Cornelis Draaijer <jcdra1@gmail.com>");
 391 MODULE_DESCRIPTION("AHT10/AHT20 Temperature and Humidity sensor driver");
 392 MODULE_VERSION("1.0");
 393 MODULE_LICENSE("GPL v2");