1 /*
2 * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
3 * The LTC2473 is identical to the 2471, but reports a differential signal.
4 *
5 * Copyright (C) 2017 Topic Embedded Products
6 * Author: Mike Looijmans <mike.looijmans@topic.nl>
7 *
8 * License: GPLv2
9 */
10
11 #include <linux/err.h>
12 #include <linux/i2c.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/iio/iio.h>
16 #include <linux/iio/sysfs.h>
17
18 enum ltc2471_chips {
19 ltc2471,
20 ltc2473,
21 };
22
23 struct ltc2471_data {
24 struct i2c_client *client;
25 };
26
27 /* Reference voltage is 1.25V */
28 #define LTC2471_VREF 1250
29
30 /* Read two bytes from the I2C bus to obtain the ADC result */
ltc2471_get_value(struct i2c_client * client)31 static int ltc2471_get_value(struct i2c_client *client)
32 {
33 int ret;
34 __be16 buf;
35
36 ret = i2c_master_recv(client, (char *)&buf, sizeof(buf));
37 if (ret < 0)
38 return ret;
39 if (ret != sizeof(buf))
40 return -EIO;
41
42 /* MSB first */
43 return be16_to_cpu(buf);
44 }
45
ltc2471_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long info)46 static int ltc2471_read_raw(struct iio_dev *indio_dev,
47 struct iio_chan_spec const *chan,
48 int *val, int *val2, long info)
49 {
50 struct ltc2471_data *data = iio_priv(indio_dev);
51 int ret;
52
53 switch (info) {
54 case IIO_CHAN_INFO_RAW:
55 ret = ltc2471_get_value(data->client);
56 if (ret < 0)
57 return ret;
58 *val = ret;
59 return IIO_VAL_INT;
60
61 case IIO_CHAN_INFO_SCALE:
62 if (chan->differential)
63 /* Output ranges from -VREF to +VREF */
64 *val = 2 * LTC2471_VREF;
65 else
66 /* Output ranges from 0 to VREF */
67 *val = LTC2471_VREF;
68 *val2 = 16; /* 16 data bits */
69 return IIO_VAL_FRACTIONAL_LOG2;
70
71 case IIO_CHAN_INFO_OFFSET:
72 /* Only differential chip has this property */
73 *val = -LTC2471_VREF;
74 return IIO_VAL_INT;
75
76 default:
77 return -EINVAL;
78 }
79 }
80
81 static const struct iio_chan_spec ltc2471_channel[] = {
82 {
83 .type = IIO_VOLTAGE,
84 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
85 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
86 },
87 };
88
89 static const struct iio_chan_spec ltc2473_channel[] = {
90 {
91 .type = IIO_VOLTAGE,
92 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
93 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
94 BIT(IIO_CHAN_INFO_OFFSET),
95 .differential = 1,
96 },
97 };
98
99 static const struct iio_info ltc2471_info = {
100 .read_raw = ltc2471_read_raw,
101 };
102
ltc2471_i2c_probe(struct i2c_client * client,const struct i2c_device_id * id)103 static int ltc2471_i2c_probe(struct i2c_client *client,
104 const struct i2c_device_id *id)
105 {
106 struct iio_dev *indio_dev;
107 struct ltc2471_data *data;
108 int ret;
109
110 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
111 return -EOPNOTSUPP;
112
113 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
114 if (!indio_dev)
115 return -ENOMEM;
116
117 data = iio_priv(indio_dev);
118 data->client = client;
119
120 indio_dev->dev.parent = &client->dev;
121 indio_dev->name = id->name;
122 indio_dev->info = <c2471_info;
123 indio_dev->modes = INDIO_DIRECT_MODE;
124 if (id->driver_data == ltc2473)
125 indio_dev->channels = ltc2473_channel;
126 else
127 indio_dev->channels = ltc2471_channel;
128 indio_dev->num_channels = 1;
129
130 /* Trigger once to start conversion and check if chip is there */
131 ret = ltc2471_get_value(client);
132 if (ret < 0) {
133 dev_err(&client->dev, "Cannot read from device.\n");
134 return ret;
135 }
136
137 return devm_iio_device_register(&client->dev, indio_dev);
138 }
139
140 static const struct i2c_device_id ltc2471_i2c_id[] = {
141 { "ltc2471", ltc2471 },
142 { "ltc2473", ltc2473 },
143 {}
144 };
145 MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);
146
147 static struct i2c_driver ltc2471_i2c_driver = {
148 .driver = {
149 .name = "ltc2471",
150 },
151 .probe = ltc2471_i2c_probe,
152 .id_table = ltc2471_i2c_id,
153 };
154
155 module_i2c_driver(ltc2471_i2c_driver);
156
157 MODULE_DESCRIPTION("LTC2471/LTC2473 ADC driver");
158 MODULE_AUTHOR("Topic Embedded Products");
159 MODULE_LICENSE("GPL v2");
160