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
17 enum ltc2471_chips {
18 ltc2471,
19 ltc2473,
20 };
21
22 struct 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 */
ltc2471_get_value(struct i2c_client * client)30 static 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
ltc2471_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long info)45 static 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
80 static 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
88 static 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
98 static const struct iio_info ltc2471_info = {
99 .read_raw = ltc2471_read_raw,
100 };
101
ltc2471_i2c_probe(struct i2c_client * client)102 static 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 = <c2471_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
138 static const struct i2c_device_id ltc2471_i2c_id[] = {
139 { "ltc2471", ltc2471 },
140 { "ltc2473", ltc2473 },
141 {}
142 };
143 MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);
144
145 static struct i2c_driver ltc2471_i2c_driver = {
146 .driver = {
147 .name = "ltc2471",
148 },
149 .probe_new = ltc2471_i2c_probe,
150 .id_table = ltc2471_i2c_id,
151 };
152
153 module_i2c_driver(ltc2471_i2c_driver);
154
155 MODULE_DESCRIPTION("LTC2471/LTC2473 ADC driver");
156 MODULE_AUTHOR("Topic Embedded Products");
157 MODULE_LICENSE("GPL v2");
158