drivers/iio/humidity/si7020.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * si7020.c - Silicon Labs Si7013/20/21 Relative Humidity and Temp Sensors
   4  * Copyright (c) 2013,2014  Uplogix, Inc.
   5  * David Barksdale <dbarksdale@uplogix.com>
   6  */
   7
   8 /*
   9  * The Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors
  10  * are i2c devices which have an identical programming interface for
  11  * measuring relative humidity and temperature. The Si7013 has an additional
  12  * temperature input which this driver does not support.
  13  *
  14  * Data Sheets:
  15  *   Si7013: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7013.pdf
  16  *   Si7020: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7020.pdf
  17  *   Si7021: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7021.pdf
  18  */
  19
  20 #include <linux/delay.h>
  21 #include <linux/i2c.h>
  22 #include <linux/module.h>
  23 #include <linux/mod_devicetable.h>
  24 #include <linux/slab.h>
  25 #include <linux/sysfs.h>
  26
  27 #include <linux/iio/iio.h>
  28 #include <linux/iio/sysfs.h>
  29
  30 /* Measure Relative Humidity, Hold Master Mode */
  31 #define SI7020CMD_RH_HOLD       0xE5
  32 /* Measure Temperature, Hold Master Mode */
  33 #define SI7020CMD_TEMP_HOLD     0xE3
  34 /* Software Reset */
  35 #define SI7020CMD_RESET         0xFE
  36
  37 static int si7020_read_raw(struct iio_dev *indio_dev,
  38                            struct iio_chan_spec const *chan, int *val,
  39                            int *val2, long mask)
  40 {
  41         struct i2c_client **client = iio_priv(indio_dev);
  42         int ret;
  43
  44         switch (mask) {
  45         case IIO_CHAN_INFO_RAW:
  46                 ret = i2c_smbus_read_word_swapped(*client,
  47                                                   chan->type == IIO_TEMP ?
  48                                                   SI7020CMD_TEMP_HOLD :
  49                                                   SI7020CMD_RH_HOLD);
  50                 if (ret < 0)
  51                         return ret;
  52                 *val = ret >> 2;
  53                 /*
  54                  * Humidity values can slightly exceed the 0-100%RH
  55                  * range and should be corrected by software
  56                  */
  57                 if (chan->type == IIO_HUMIDITYRELATIVE)
  58                         *val = clamp_val(*val, 786, 13893);
  59                 return IIO_VAL_INT;
  60         case IIO_CHAN_INFO_SCALE:
  61                 if (chan->type == IIO_TEMP)
  62                         *val = 175720; /* = 175.72 * 1000 */
  63                 else
  64                         *val = 125 * 1000;
  65                 *val2 = 65536 >> 2;
  66                 return IIO_VAL_FRACTIONAL;
  67         case IIO_CHAN_INFO_OFFSET:
  68                 /*
  69                  * Since iio_convert_raw_to_processed_unlocked assumes offset
  70                  * is an integer we have to round these values and lose
  71                  * accuracy.
  72                  * Relative humidity will be 0.0032959% too high and
  73                  * temperature will be 0.00277344 degrees too high.
  74                  * This is no big deal because it's within the accuracy of the
  75                  * sensor.
  76                  */
  77                 if (chan->type == IIO_TEMP)
  78                         *val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */
  79                 else
  80                         *val = -786; /* = -6 * (65536 >> 2) / 125 */
  81                 return IIO_VAL_INT;
  82         default:
  83                 break;
  84         }
  85
  86         return -EINVAL;
  87 }
  88
  89 static const struct iio_chan_spec si7020_channels[] = {
  90         {
  91                 .type = IIO_HUMIDITYRELATIVE,
  92                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  93                         BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
  94         },
  95         {
  96                 .type = IIO_TEMP,
  97                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  98                         BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
  99         }
 100 };
 101
 102 static const struct iio_info si7020_info = {
 103         .read_raw = si7020_read_raw,
 104 };
 105
 106 static int si7020_probe(struct i2c_client *client,
 107                         const struct i2c_device_id *id)
 108 {
 109         struct iio_dev *indio_dev;
 110         struct i2c_client **data;
 111         int ret;
 112
 113         if (!i2c_check_functionality(client->adapter,
 114                                      I2C_FUNC_SMBUS_WRITE_BYTE |
 115                                      I2C_FUNC_SMBUS_READ_WORD_DATA))
 116                 return -EOPNOTSUPP;
 117
 118         /* Reset device, loads default settings. */
 119         ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
 120         if (ret < 0)
 121                 return ret;
 122         /* Wait the maximum power-up time after software reset. */
 123         msleep(15);
 124
 125         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 126         if (!indio_dev)
 127                 return -ENOMEM;
 128
 129         data = iio_priv(indio_dev);
 130         *data = client;
 131
 132         indio_dev->name = dev_name(&client->dev);
 133         indio_dev->modes = INDIO_DIRECT_MODE;
 134         indio_dev->info = &si7020_info;
 135         indio_dev->channels = si7020_channels;
 136         indio_dev->num_channels = ARRAY_SIZE(si7020_channels);
 137
 138         return devm_iio_device_register(&client->dev, indio_dev);
 139 }
 140
 141 static const struct i2c_device_id si7020_id[] = {
 142         { "si7020", 0 },
 143         { "th06", 0 },
 144         { }
 145 };
 146 MODULE_DEVICE_TABLE(i2c, si7020_id);
 147
 148 static const struct of_device_id si7020_dt_ids[] = {
 149         { .compatible = "silabs,si7020" },
 150         { }
 151 };
 152 MODULE_DEVICE_TABLE(of, si7020_dt_ids);
 153
 154 static struct i2c_driver si7020_driver = {
 155         .driver = {
 156                 .name = "si7020",
 157                 .of_match_table = si7020_dt_ids,
 158         },
 159         .probe          = si7020_probe,
 160         .id_table       = si7020_id,
 161 };
 162
 163 module_i2c_driver(si7020_driver);
 164 MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
 165 MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
 166 MODULE_LICENSE("GPL");