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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");