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", 0 },
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");
144