LXR linux/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/slab.h>
  24#include <linux/sysfs.h>
  25
  26#include <linux/iio/iio.h>
  27#include <linux/iio/sysfs.h>
  28
  29/* Measure Relative Humidity, Hold Master Mode */
  30#define SI7020CMD_RH_HOLD       0xE5
  31/* Measure Temperature, Hold Master Mode */
  32#define SI7020CMD_TEMP_HOLD     0xE3
  33/* Software Reset */
  34#define SI7020CMD_RESET         0xFE
  35
  36static int si7020_read_raw(struct iio_dev *indio_dev,
  37                           struct iio_chan_spec const *chan, int *val,
  38                           int *val2, long mask)
  39{
  40        struct i2c_client **client = iio_priv(indio_dev);
  41        int ret;
  42
  43        switch (mask) {
  44        case IIO_CHAN_INFO_RAW:
  45                ret = i2c_smbus_read_word_swapped(*client,
  46                                                  chan->type == IIO_TEMP ?
  47                                                  SI7020CMD_TEMP_HOLD :
  48                                                  SI7020CMD_RH_HOLD);
  49                if (ret < 0)
  50                        return ret;
  51                *val = ret >> 2;
  52                /*
  53                 * Humidity values can slightly exceed the 0-100%RH
  54                 * range and should be corrected by software
  55                 */
  56                if (chan->type == IIO_HUMIDITYRELATIVE)
  57                        *val = clamp_val(*val, 786, 13893);
  58                return IIO_VAL_INT;
  59        case IIO_CHAN_INFO_SCALE:
  60                if (chan->type == IIO_TEMP)
  61                        *val = 175720; /* = 175.72 * 1000 */
  62                else
  63                        *val = 125 * 1000;
  64                *val2 = 65536 >> 2;
  65                return IIO_VAL_FRACTIONAL;
  66        case IIO_CHAN_INFO_OFFSET:
  67                /*
  68                 * Since iio_convert_raw_to_processed_unlocked assumes offset
  69                 * is an integer we have to round these values and lose
  70                 * accuracy.
  71                 * Relative humidity will be 0.0032959% too high and
  72                 * temperature will be 0.00277344 degrees too high.
  73                 * This is no big deal because it's within the accuracy of the
  74                 * sensor.
  75                 */
  76                if (chan->type == IIO_TEMP)
  77                        *val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */
  78                else
  79                        *val = -786; /* = -6 * (65536 >> 2) / 125 */
  80                return IIO_VAL_INT;
  81        default:
  82                break;
  83        }
  84
  85        return -EINVAL;
  86}
  87
  88static const struct iio_chan_spec si7020_channels[] = {
  89        {
  90                .type = IIO_HUMIDITYRELATIVE,
  91                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  92                        BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
  93        },
  94        {
  95                .type = IIO_TEMP,
  96                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  97                        BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
  98        }
  99};
 100
 101static const struct iio_info si7020_info = {
 102        .read_raw = si7020_read_raw,
 103};
 104
 105static int si7020_probe(struct i2c_client *client,
 106                        const struct i2c_device_id *id)
 107{
 108        struct iio_dev *indio_dev;
 109        struct i2c_client **data;
 110        int ret;
 111
 112        if (!i2c_check_functionality(client->adapter,
 113                                     I2C_FUNC_SMBUS_WRITE_BYTE |
 114                                     I2C_FUNC_SMBUS_READ_WORD_DATA))
 115                return -EOPNOTSUPP;
 116
 117        /* Reset device, loads default settings. */
 118        ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
 119        if (ret < 0)
 120                return ret;
 121        /* Wait the maximum power-up time after software reset. */
 122        msleep(15);
 123
 124        indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 125        if (!indio_dev)
 126                return -ENOMEM;
 127
 128        data = iio_priv(indio_dev);
 129        *data = client;
 130
 131        indio_dev->dev.parent = &client->dev;
 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
 141static const struct i2c_device_id si7020_id[] = {
 142        { "si7020", 0 },
 143        { "th06", 0 },
 144        { }
 145};
 146MODULE_DEVICE_TABLE(i2c, si7020_id);
 147
 148static const struct of_device_id si7020_dt_ids[] = {
 149        { .compatible = "silabs,si7020" },
 150        { }
 151};
 152MODULE_DEVICE_TABLE(of, si7020_dt_ids);
 153
 154static struct i2c_driver si7020_driver = {
 155        .driver = {
 156                .name = "si7020",
 157                .of_match_table = of_match_ptr(si7020_dt_ids),
 158        },
 159        .probe          = si7020_probe,
 160        .id_table       = si7020_id,
 161};
 162
 163module_i2c_driver(si7020_driver);
 164MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
 165MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
 166MODULE_LICENSE("GPL");
 167