drivers/iio/adc/ltc2497.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * ltc2497.c - Driver for Analog Devices/Linear Technology LTC2497 ADC
   4  *
   5  * Copyright (C) 2017 Analog Devices Inc.
   6  *
   7  * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf
   8  */
   9
  10 #include <linux/i2c.h>
  11 #include <linux/iio/iio.h>
  12 #include <linux/iio/driver.h>
  13 #include <linux/module.h>
  14 #include <linux/mod_devicetable.h>
  15
  16 #include "ltc2497.h"
  17
  18 struct ltc2497_driverdata {
  19         /* this must be the first member */
  20         struct ltc2497core_driverdata common_ddata;
  21         struct i2c_client *client;
  22         /*
  23          * DMA (thus cache coherency maintenance) requires the
  24          * transfer buffers to live in their own cache lines.
  25          */
  26         __be32 buf ____cacheline_aligned;
  27 };
  28
  29 static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
  30                                       u8 address, int *val)
  31 {
  32         struct ltc2497_driverdata *st =
  33                 container_of(ddata, struct ltc2497_driverdata, common_ddata);
  34         int ret;
  35
  36         if (val) {
  37                 ret = i2c_master_recv(st->client, (char *)&st->buf, 3);
  38                 if (ret < 0) {
  39                         dev_err(&st->client->dev, "i2c_master_recv failed\n");
  40                         return ret;
  41                 }
  42
  43                 *val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);
  44
  45                 /*
  46                  * The part started a new conversion at the end of the above i2c
  47                  * transfer, so if the address didn't change since the last call
  48                  * everything is fine and we can return early.
  49                  * If not (which should only happen when some sort of bulk
  50                  * conversion is implemented) we have to program the new
  51                  * address. Note that this probably fails as the conversion that
  52                  * was triggered above is like not complete yet and the two
  53                  * operations have to be done in a single transfer.
  54                  */
  55                 if (ddata->addr_prev == address)
  56                         return 0;
  57         }
  58
  59         ret = i2c_smbus_write_byte(st->client,
  60                                    LTC2497_ENABLE | address);
  61         if (ret)
  62                 dev_err(&st->client->dev, "i2c transfer failed: %pe\n",
  63                         ERR_PTR(ret));
  64         return ret;
  65 }
  66
  67 static int ltc2497_probe(struct i2c_client *client,
  68                          const struct i2c_device_id *id)
  69 {
  70         struct iio_dev *indio_dev;
  71         struct ltc2497_driverdata *st;
  72         struct device *dev = &client->dev;
  73
  74         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
  75                                      I2C_FUNC_SMBUS_WRITE_BYTE))
  76                 return -EOPNOTSUPP;
  77
  78         indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
  79         if (!indio_dev)
  80                 return -ENOMEM;
  81
  82         st = iio_priv(indio_dev);
  83         i2c_set_clientdata(client, indio_dev);
  84         st->client = client;
  85         st->common_ddata.result_and_measure = ltc2497_result_and_measure;
  86
  87         return ltc2497core_probe(dev, indio_dev);
  88 }
  89
  90 static int ltc2497_remove(struct i2c_client *client)
  91 {
  92         struct iio_dev *indio_dev = i2c_get_clientdata(client);
  93
  94         ltc2497core_remove(indio_dev);
  95
  96         return 0;
  97 }
  98
  99 static const struct i2c_device_id ltc2497_id[] = {
 100         { "ltc2497", 0 },
 101         { }
 102 };
 103 MODULE_DEVICE_TABLE(i2c, ltc2497_id);
 104
 105 static const struct of_device_id ltc2497_of_match[] = {
 106         { .compatible = "lltc,ltc2497", },
 107         {},
 108 };
 109 MODULE_DEVICE_TABLE(of, ltc2497_of_match);
 110
 111 static struct i2c_driver ltc2497_driver = {
 112         .driver = {
 113                 .name = "ltc2497",
 114                 .of_match_table = ltc2497_of_match,
 115         },
 116         .probe = ltc2497_probe,
 117         .remove = ltc2497_remove,
 118         .id_table = ltc2497_id,
 119 };
 120 module_i2c_driver(ltc2497_driver);
 121
 122 MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
 123 MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver");
 124 MODULE_LICENSE("GPL v2");