ltc2471.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
  4 * The LTC2473 is identical to the 2471, but reports a differential signal.
  5 *
  6 * Copyright (C) 2017 Topic Embedded Products
  7 * Author: Mike Looijmans <mike.looijmans@topic.nl>
  8 */
  9
 10#include <linux/err.h>
 11#include <linux/i2c.h>
 12#include <linux/kernel.h>
 13#include <linux/module.h>
 14#include <linux/iio/iio.h>
 15#include <linux/iio/sysfs.h>
 16
 17enum ltc2471_chips {
 18	ltc2471,
 19	ltc2473,
 20};
 21
 22struct ltc2471_data {
 23	struct i2c_client *client;
 24};
 25
 26/* Reference voltage is 1.25V */
 27#define LTC2471_VREF 1250
 28
 29/* Read two bytes from the I2C bus to obtain the ADC result */
 30static int ltc2471_get_value(struct i2c_client *client)
 31{
 32	int ret;
 33	__be16 buf;
 34
 35	ret = i2c_master_recv(client, (char *)&buf, sizeof(buf));
 36	if (ret < 0)
 37		return ret;
 38	if (ret != sizeof(buf))
 39		return -EIO;
 40
 41	/* MSB first */
 42	return be16_to_cpu(buf);
 43}
 44
 45static int ltc2471_read_raw(struct iio_dev *indio_dev,
 46			    struct iio_chan_spec const *chan,
 47			    int *val, int *val2, long info)
 48{
 49	struct ltc2471_data *data = iio_priv(indio_dev);
 50	int ret;
 51
 52	switch (info) {
 53	case IIO_CHAN_INFO_RAW:
 54		ret = ltc2471_get_value(data->client);
 55		if (ret < 0)
 56			return ret;
 57		*val = ret;
 58		return IIO_VAL_INT;
 59
 60	case IIO_CHAN_INFO_SCALE:
 61		if (chan->differential)
 62			/* Output ranges from -VREF to +VREF */
 63			*val = 2 * LTC2471_VREF;
 64		else
 65			/* Output ranges from 0 to VREF */
 66			*val = LTC2471_VREF;
 67		*val2 = 16;	/* 16 data bits */
 68		return IIO_VAL_FRACTIONAL_LOG2;
 69
 70	case IIO_CHAN_INFO_OFFSET:
 71		/* Only differential chip has this property */
 72		*val = -LTC2471_VREF;
 73		return IIO_VAL_INT;
 74
 75	default:
 76		return -EINVAL;
 77	}
 78}
 79
 80static const struct iio_chan_spec ltc2471_channel[] = {
 81	{
 82		.type = IIO_VOLTAGE,
 83		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 84		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
 85	},
 86};
 87
 88static const struct iio_chan_spec ltc2473_channel[] = {
 89	{
 90		.type = IIO_VOLTAGE,
 91		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 92		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
 93					    BIT(IIO_CHAN_INFO_OFFSET),
 94		.differential = 1,
 95	},
 96};
 97
 98static const struct iio_info ltc2471_info = {
 99	.read_raw = ltc2471_read_raw,
100};
101
102static int ltc2471_i2c_probe(struct i2c_client *client)
103{
104	const struct i2c_device_id *id = i2c_client_get_device_id(client);
105	struct iio_dev *indio_dev;
106	struct ltc2471_data *data;
107	int ret;
108
109	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
110		return -EOPNOTSUPP;
111
112	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
113	if (!indio_dev)
114		return -ENOMEM;
115
116	data = iio_priv(indio_dev);
117	data->client = client;
118
119	indio_dev->name = id->name;
120	indio_dev->info = &ltc2471_info;
121	indio_dev->modes = INDIO_DIRECT_MODE;
122	if (id->driver_data == ltc2473)
123		indio_dev->channels = ltc2473_channel;
124	else
125		indio_dev->channels = ltc2471_channel;
126	indio_dev->num_channels = 1;
127
128	/* Trigger once to start conversion and check if chip is there */
129	ret = ltc2471_get_value(client);
130	if (ret < 0) {
131		dev_err(&client->dev, "Cannot read from device.\n");
132		return ret;
133	}
134
135	return devm_iio_device_register(&client->dev, indio_dev);
136}
137
138static const struct i2c_device_id ltc2471_i2c_id[] = {
139	{ "ltc2471", ltc2471 },
140	{ "ltc2473", ltc2473 },
141	{ }
142};
143MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);
144
145static struct i2c_driver ltc2471_i2c_driver = {
146	.driver = {
147		.name = "ltc2471",
148	},
149	.probe = ltc2471_i2c_probe,
150	.id_table = ltc2471_i2c_id,
151};
152
153module_i2c_driver(ltc2471_i2c_driver);
154
155MODULE_DESCRIPTION("LTC2471/LTC2473 ADC driver");
156MODULE_AUTHOR("Topic Embedded Products");
157MODULE_LICENSE("GPL v2");