aboutsummaryrefslogtreecommitdiff
path: root/drivers/iio/adc/ltc2471.c
blob: b88102b751cfc5c7a95497c34971326607d29527 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
/*
 * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
 * The LTC2473 is identical to the 2471, but reports a differential signal.
 *
 * Copyright (C) 2017 Topic Embedded Products
 * Author: Mike Looijmans <mike.looijmans@topic.nl>
 *
 * License: GPLv2
 */

#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

enum ltc2471_chips {
	ltc2471,
	ltc2473,
};

struct ltc2471_data {
	struct i2c_client *client;
};

/* Reference voltage is 1.25V */
#define LTC2471_VREF 1250

/* Read two bytes from the I2C bus to obtain the ADC result */
static int ltc2471_get_value(struct i2c_client *client)
{
	int ret;
	__be16 buf;

	ret = i2c_master_recv(client, (char *)&buf, sizeof(buf));
	if (ret < 0)
		return ret;
	if (ret != sizeof(buf))
		return -EIO;

	/* MSB first */
	return be16_to_cpu(buf);
}

static int ltc2471_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan,
			    int *val, int *val2, long info)
{
	struct ltc2471_data *data = iio_priv(indio_dev);
	int ret;

	switch (info) {
	case IIO_CHAN_INFO_RAW:
		ret = ltc2471_get_value(data->client);
		if (ret < 0)
			return ret;
		*val = ret;
		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:
		if (chan->differential)
			/* Output ranges from -VREF to +VREF */
			*val = 2 * LTC2471_VREF;
		else
			/* Output ranges from 0 to VREF */
			*val = LTC2471_VREF;
		*val2 = 16;	/* 16 data bits */
		return IIO_VAL_FRACTIONAL_LOG2;

	case IIO_CHAN_INFO_OFFSET:
		/* Only differential chip has this property */
		*val = -LTC2471_VREF;
		return IIO_VAL_INT;

	default:
		return -EINVAL;
	}
}

static const struct iio_chan_spec ltc2471_channel[] = {
	{
		.type = IIO_VOLTAGE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
	},
};

static const struct iio_chan_spec ltc2473_channel[] = {
	{
		.type = IIO_VOLTAGE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
					    BIT(IIO_CHAN_INFO_OFFSET),
		.differential = 1,
	},
};

static const struct iio_info ltc2471_info = {
	.read_raw = ltc2471_read_raw,
};

static int ltc2471_i2c_probe(struct i2c_client *client,
			     const struct i2c_device_id *id)
{
	struct iio_dev *indio_dev;
	struct ltc2471_data *data;
	int ret;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
		return -EOPNOTSUPP;

	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
	if (!indio_dev)
		return -ENOMEM;

	data = iio_priv(indio_dev);
	data->client = client;

	indio_dev->dev.parent = &client->dev;
	indio_dev->name = id->name;
	indio_dev->info = &ltc2471_info;
	indio_dev->modes = INDIO_DIRECT_MODE;
	if (id->driver_data == ltc2473)
		indio_dev->channels = ltc2473_channel;
	else
		indio_dev->channels = ltc2471_channel;
	indio_dev->num_channels = 1;

	/* Trigger once to start conversion and check if chip is there */
	ret = ltc2471_get_value(client);
	if (ret < 0) {
		dev_err(&client->dev, "Cannot read from device.\n");
		return ret;
	}

	return devm_iio_device_register(&client->dev, indio_dev);
}

static const struct i2c_device_id ltc2471_i2c_id[] = {
	{ "ltc2471", ltc2471 },
	{ "ltc2473", ltc2473 },
	{}
};
MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);

static struct i2c_driver ltc2471_i2c_driver = {
	.driver = {
		.name = "ltc2471",
	},
	.probe    = ltc2471_i2c_probe,
	.id_table = ltc2471_i2c_id,
};

module_i2c_driver(ltc2471_i2c_driver);

MODULE_DESCRIPTION("LTC2471/LTC2473 ADC driver");
MODULE_AUTHOR("Topic Embedded Products");
MODULE_LICENSE("GPL v2");