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
44static 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_data(*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		if (chan->type == IIO_HUMIDITYRELATIVE)
61			*val &= GENMASK(11, 0);
62		return IIO_VAL_INT;
63	case IIO_CHAN_INFO_SCALE:
64		if (chan->type == IIO_TEMP)
65			*val = 175720; /* = 175.72 * 1000 */
66		else
67			*val = 125 * 1000;
68		*val2 = 65536 >> 2;
69		return IIO_VAL_FRACTIONAL;
70	case IIO_CHAN_INFO_OFFSET:
71		/*
72		 * Since iio_convert_raw_to_processed_unlocked assumes offset
73		 * is an integer we have to round these values and lose
74		 * accuracy.
75		 * Relative humidity will be 0.0032959% too high and
76		 * temperature will be 0.00277344 degrees too high.
77		 * This is no big deal because it's within the accuracy of the
78		 * sensor.
79		 */
80		if (chan->type == IIO_TEMP)
81			*val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */
82		else
83			*val = -786; /* = -6 * (65536 >> 2) / 125 */
84		return IIO_VAL_INT;
85	default:
86		break;
87	}
88
89	return -EINVAL;
90}
91
92static const struct iio_chan_spec si7020_channels[] = {
93	{
94		.type = IIO_HUMIDITYRELATIVE,
95		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
96			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
97	},
98	{
99		.type = IIO_TEMP,
100		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
101			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
102	}
103};
104
105static const struct iio_info si7020_info = {
106	.read_raw = si7020_read_raw,
107	.driver_module = THIS_MODULE,
108};
109
110static int si7020_probe(struct i2c_client *client,
111			const struct i2c_device_id *id)
112{
113	struct iio_dev *indio_dev;
114	struct i2c_client **data;
115	int ret;
116
117	if (!i2c_check_functionality(client->adapter,
118				     I2C_FUNC_SMBUS_WRITE_BYTE |
119				     I2C_FUNC_SMBUS_READ_WORD_DATA))
120		return -ENODEV;
121
122	/* Reset device, loads default settings. */
123	ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
124	if (ret < 0)
125		return ret;
126	/* Wait the maximum power-up time after software reset. */
127	msleep(15);
128
129	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
130	if (!indio_dev)
131		return -ENOMEM;
132
133	data = iio_priv(indio_dev);
134	*data = client;
135
136	indio_dev->dev.parent = &client->dev;
137	indio_dev->name = dev_name(&client->dev);
138	indio_dev->modes = INDIO_DIRECT_MODE;
139	indio_dev->info = &si7020_info;
140	indio_dev->channels = si7020_channels;
141	indio_dev->num_channels = ARRAY_SIZE(si7020_channels);
142
143	return devm_iio_device_register(&client->dev, indio_dev);
144}
145
146static const struct i2c_device_id si7020_id[] = {
147	{ "si7020", 0 },
148	{ }
149};
150MODULE_DEVICE_TABLE(i2c, si7020_id);
151
152static struct i2c_driver si7020_driver = {
153	.driver.name	= "si7020",
154	.probe		= si7020_probe,
155	.id_table	= si7020_id,
156};
157
158module_i2c_driver(si7020_driver);
159MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
160MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
161MODULE_LICENSE("GPL");
162