drivers/iio/adc/ltc2471.c

   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 */
  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
  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
 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 = &ltc2471_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");