drivers/hwmon/aht10.c

   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                        const struct i2c_device_id *aht10_id)
 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");