1 /* 2 * si7020.c - Silicon Labs Si7013/20/21 Relative Humidity and Temp Sensors 3 * Copyright (c) 2013,2014 Uplogix, Inc. 4 * David Barksdale <dbarksdale@uplogix.com> 5 * 6 * This program is free software; you can redistribute it and/or modify it 7 * under the terms and conditions of the GNU General Public License, 8 * version 2, as published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 */ 15 16 /* 17 * The Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors 18 * are i2c devices which have an identical programming interface for 19 * measuring relative humidity and temperature. The Si7013 has an additional 20 * temperature input which this driver does not support. 21 * 22 * Data Sheets: 23 * Si7013: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7013.pdf 24 * Si7020: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7020.pdf 25 * Si7021: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7021.pdf 26 */ 27 28 #include <linux/delay.h> 29 #include <linux/i2c.h> 30 #include <linux/module.h> 31 #include <linux/slab.h> 32 #include <linux/sysfs.h> 33 34 #include <linux/iio/iio.h> 35 #include <linux/iio/sysfs.h> 36 37 /* Measure Relative Humidity, Hold Master Mode */ 38 #define SI7020CMD_RH_HOLD 0xE5 39 /* Measure Temperature, Hold Master Mode */ 40 #define SI7020CMD_TEMP_HOLD 0xE3 41 /* Software Reset */ 42 #define SI7020CMD_RESET 0xFE 43 44 static int si7020_read_raw(struct iio_dev *indio_dev, 45 struct iio_chan_spec const *chan, int *val, 46 int *val2, long mask) 47 { 48 struct i2c_client **client = iio_priv(indio_dev); 49 int ret; 50 51 switch (mask) { 52 case IIO_CHAN_INFO_RAW: 53 ret = i2c_smbus_read_word_swapped(*client, 54 chan->type == IIO_TEMP ? 55 SI7020CMD_TEMP_HOLD : 56 SI7020CMD_RH_HOLD); 57 if (ret < 0) 58 return ret; 59 *val = ret >> 2; 60 /* 61 * Humidity values can slightly exceed the 0-100%RH 62 * range and should be corrected by software 63 */ 64 if (chan->type == IIO_HUMIDITYRELATIVE) 65 *val = clamp_val(*val, 786, 13893); 66 return IIO_VAL_INT; 67 case IIO_CHAN_INFO_SCALE: 68 if (chan->type == IIO_TEMP) 69 *val = 175720; /* = 175.72 * 1000 */ 70 else 71 *val = 125 * 1000; 72 *val2 = 65536 >> 2; 73 return IIO_VAL_FRACTIONAL; 74 case IIO_CHAN_INFO_OFFSET: 75 /* 76 * Since iio_convert_raw_to_processed_unlocked assumes offset 77 * is an integer we have to round these values and lose 78 * accuracy. 79 * Relative humidity will be 0.0032959% too high and 80 * temperature will be 0.00277344 degrees too high. 81 * This is no big deal because it's within the accuracy of the 82 * sensor. 83 */ 84 if (chan->type == IIO_TEMP) 85 *val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */ 86 else 87 *val = -786; /* = -6 * (65536 >> 2) / 125 */ 88 return IIO_VAL_INT; 89 default: 90 break; 91 } 92 93 return -EINVAL; 94 } 95 96 static const struct iio_chan_spec si7020_channels[] = { 97 { 98 .type = IIO_HUMIDITYRELATIVE, 99 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 100 BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET), 101 }, 102 { 103 .type = IIO_TEMP, 104 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 105 BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET), 106 } 107 }; 108 109 static const struct iio_info si7020_info = { 110 .read_raw = si7020_read_raw, 111 .driver_module = THIS_MODULE, 112 }; 113 114 static int si7020_probe(struct i2c_client *client, 115 const struct i2c_device_id *id) 116 { 117 struct iio_dev *indio_dev; 118 struct i2c_client **data; 119 int ret; 120 121 if (!i2c_check_functionality(client->adapter, 122 I2C_FUNC_SMBUS_WRITE_BYTE | 123 I2C_FUNC_SMBUS_READ_WORD_DATA)) 124 return -EOPNOTSUPP; 125 126 /* Reset device, loads default settings. */ 127 ret = i2c_smbus_write_byte(client, SI7020CMD_RESET); 128 if (ret < 0) 129 return ret; 130 /* Wait the maximum power-up time after software reset. */ 131 msleep(15); 132 133 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); 134 if (!indio_dev) 135 return -ENOMEM; 136 137 data = iio_priv(indio_dev); 138 *data = client; 139 140 indio_dev->dev.parent = &client->dev; 141 indio_dev->name = dev_name(&client->dev); 142 indio_dev->modes = INDIO_DIRECT_MODE; 143 indio_dev->info = &si7020_info; 144 indio_dev->channels = si7020_channels; 145 indio_dev->num_channels = ARRAY_SIZE(si7020_channels); 146 147 return devm_iio_device_register(&client->dev, indio_dev); 148 } 149 150 static const struct i2c_device_id si7020_id[] = { 151 { "si7020", 0 }, 152 { "th06", 0 }, 153 { } 154 }; 155 MODULE_DEVICE_TABLE(i2c, si7020_id); 156 157 static const struct of_device_id si7020_dt_ids[] = { 158 { .compatible = "silabs,si7020" }, 159 { } 160 }; 161 MODULE_DEVICE_TABLE(of, si7020_dt_ids); 162 163 static struct i2c_driver si7020_driver = { 164 .driver = { 165 .name = "si7020", 166 .of_match_table = of_match_ptr(si7020_dt_ids), 167 }, 168 .probe = si7020_probe, 169 .id_table = si7020_id, 170 }; 171 172 module_i2c_driver(si7020_driver); 173 MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors"); 174 MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>"); 175 MODULE_LICENSE("GPL"); 176