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(later: ktime_get(), earlier: data->time_prev);
32
33 if (time_elapsed < conv_time)
34 msleep(msecs: 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, buf: (char *)&buf, count: 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, index: 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(adap: client->adapter, I2C_FUNC_I2C |
100 I2C_FUNC_SMBUS_WRITE_BYTE))
101 return -EOPNOTSUPP;
102
103 indio_dev = devm_iio_device_alloc(parent: &client->dev, sizeof_priv: sizeof(*data));
104 if (!indio_dev)
105 return -ENOMEM;
106
107 data = iio_priv(indio_dev);
108 i2c_set_clientdata(client, data: 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(client: 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

source code of linux/drivers/iio/adc/ltc2485.c