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
37static 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
89static 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
102static const struct iio_info si7020_info = {
103	.read_raw = si7020_read_raw,
104};
105
106static int si7020_probe(struct i2c_client *client)
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->name = dev_name(&client->dev);
132	indio_dev->modes = INDIO_DIRECT_MODE;
133	indio_dev->info = &si7020_info;
134	indio_dev->channels = si7020_channels;
135	indio_dev->num_channels = ARRAY_SIZE(si7020_channels);
136
137	return devm_iio_device_register(&client->dev, indio_dev);
138}
139
140static const struct i2c_device_id si7020_id[] = {
141	{ "si7020", 0 },
142	{ "th06", 0 },
143	{ }
144};
145MODULE_DEVICE_TABLE(i2c, si7020_id);
146
147static const struct of_device_id si7020_dt_ids[] = {
148	{ .compatible = "silabs,si7020" },
149	{ }
150};
151MODULE_DEVICE_TABLE(of, si7020_dt_ids);
152
153static struct i2c_driver si7020_driver = {
154	.driver = {
155		.name = "si7020",
156		.of_match_table = si7020_dt_ids,
157	},
158	.probe		= si7020_probe,
159	.id_table	= si7020_id,
160};
161
162module_i2c_driver(si7020_driver);
163MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
164MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
165MODULE_LICENSE("GPL");
166