ltc2485.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * ltc2485.c - Driver for Linear Technology LTC2485 ADC
  4 *
  5 * Copyright (C) 2016 Alison Schofield <amsfield22@gmail.com>
  6 *
  7 * Datasheet: http://cds.linear.com/docs/en/datasheet/2485fd.pdf
  8 */
  9
 10#include <linux/delay.h>
 11#include <linux/i2c.h>
 12#include <linux/module.h>
 13
 14#include <linux/iio/iio.h>
 15#include <linux/iio/sysfs.h>
 16
 17/* Power-on configuration: rejects both 50/60Hz, operates at 1x speed */
 18#define LTC2485_CONFIG_DEFAULT		0
 19
 20struct ltc2485_data {
 21	struct i2c_client	*client;
 22	ktime_t			time_prev;	/* last conversion */
 23};
 24
 25static void ltc2485_wait_conv(struct ltc2485_data *data)
 26{
 27	const unsigned int conv_time = 147;	/* conversion time ms */
 28	unsigned int time_elapsed;
 29
 30	/* delay if conversion time not passed since last read or write */
 31	time_elapsed = ktime_ms_delta(ktime_get(), data->time_prev);
 32
 33	if (time_elapsed < conv_time)
 34		msleep(conv_time - time_elapsed);
 35}
 36
 37static int ltc2485_read(struct ltc2485_data *data, int *val)
 38{
 39	struct i2c_client *client = data->client;
 40	__be32 buf = 0;
 41	int ret;
 42
 43	ltc2485_wait_conv(data);
 44
 45	ret = i2c_master_recv(client, (char *)&buf, 4);
 46	if (ret < 0)  {
 47		dev_err(&client->dev, "i2c_master_recv failed\n");
 48		return ret;
 49	}
 50	data->time_prev = ktime_get();
 51	*val = sign_extend32(be32_to_cpu(buf) >> 6, 24);
 52
 53	return ret;
 54}
 55
 56static int ltc2485_read_raw(struct iio_dev *indio_dev,
 57			    struct iio_chan_spec const *chan,
 58			    int *val, int *val2, long mask)
 59{
 60	struct ltc2485_data *data = iio_priv(indio_dev);
 61	int ret;
 62
 63	if (mask == IIO_CHAN_INFO_RAW) {
 64		ret = ltc2485_read(data, val);
 65		if (ret < 0)
 66			return ret;
 67
 68		return IIO_VAL_INT;
 69
 70	} else if (mask == IIO_CHAN_INFO_SCALE) {
 71		*val = 5000;			/* on board vref millivolts */
 72		*val2 = 25;			/* 25 (24 + sign) data bits */
 73		return IIO_VAL_FRACTIONAL_LOG2;
 74
 75	} else {
 76		return -EINVAL;
 77	}
 78}
 79
 80static const struct iio_chan_spec ltc2485_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_info ltc2485_info = {
 89	.read_raw = ltc2485_read_raw,
 90};
 91
 92static int ltc2485_probe(struct i2c_client *client)
 93{
 94	const struct i2c_device_id *id = i2c_client_get_device_id(client);
 95	struct iio_dev *indio_dev;
 96	struct ltc2485_data *data;
 97	int ret;
 98
 99	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
100				     I2C_FUNC_SMBUS_WRITE_BYTE))
101		return -EOPNOTSUPP;
102
103	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
104	if (!indio_dev)
105		return -ENOMEM;
106
107	data = iio_priv(indio_dev);
108	i2c_set_clientdata(client, indio_dev);
109	data->client = client;
110
111	indio_dev->name = id->name;
112	indio_dev->info = &ltc2485_info;
113	indio_dev->modes = INDIO_DIRECT_MODE;
114	indio_dev->channels = ltc2485_channel;
115	indio_dev->num_channels = ARRAY_SIZE(ltc2485_channel);
116
117	ret = i2c_smbus_write_byte(data->client, LTC2485_CONFIG_DEFAULT);
118	if (ret < 0)
119		return ret;
120
121	data->time_prev = ktime_get();
122
123	return devm_iio_device_register(&client->dev, indio_dev);
124}
125
126static const struct i2c_device_id ltc2485_id[] = {
127	{ "ltc2485" },
128	{ }
129};
130MODULE_DEVICE_TABLE(i2c, ltc2485_id);
131
132static struct i2c_driver ltc2485_driver = {
133	.driver = {
134		.name = "ltc2485",
135	},
136	.probe = ltc2485_probe,
137	.id_table = ltc2485_id,
138};
139module_i2c_driver(ltc2485_driver);
140
141MODULE_AUTHOR("Alison Schofield <amsfield22@gmail.com>");
142MODULE_DESCRIPTION("Linear Technology LTC2485 ADC driver");
143MODULE_LICENSE("GPL v2");