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 #include <linux/property.h>
  16
  17 #include <asm/unaligned.h>
  18
  19 #include "ltc2497.h"
  20
  21 enum ltc2497_chip_type {
  22         TYPE_LTC2497,
  23         TYPE_LTC2499,
  24 };
  25
  26 struct ltc2497_driverdata {
  27         /* this must be the first member */
  28         struct ltc2497core_driverdata common_ddata;
  29         struct i2c_client *client;
  30         u32 recv_size;
  31         /*
  32          * DMA (thus cache coherency maintenance) may require the
  33          * transfer buffers to live in their own cache lines.
  34          */
  35         union {
  36                 __be32 d32;
  37                 u8 d8[3];
  38         } data __aligned(IIO_DMA_MINALIGN);
  39 };
  40
  41 static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
  42                                       u8 address, int *val)
  43 {
  44         struct ltc2497_driverdata *st =
  45                 container_of(ddata, struct ltc2497_driverdata, common_ddata);
  46         int ret;
  47
  48         if (val) {
  49                 if (st->recv_size == 3)
  50                         ret = i2c_master_recv(st->client, (char *)&st->data.d8,
  51                                               st->recv_size);
  52                 else
  53                         ret = i2c_master_recv(st->client, (char *)&st->data.d32,
  54                                               st->recv_size);
  55                 if (ret < 0) {
  56                         dev_err(&st->client->dev, "i2c_master_recv failed\n");
  57                         return ret;
  58                 }
  59
  60                 /*
  61                  * The data format is 16/24 bit 2s complement, but with an upper sign bit on the
  62                  * resolution + 1 position, which is set for positive values only. Given this
  63                  * bit's value, subtracting BIT(resolution + 1) from the ADC's result is
  64                  * equivalent to a sign extension.
  65                  */
  66                 if (st->recv_size == 3) {
  67                         *val = (get_unaligned_be24(st->data.d8) >> 6)
  68                                 - BIT(ddata->chip_info->resolution + 1);
  69                 } else {
  70                         *val = (be32_to_cpu(st->data.d32) >> 6)
  71                                 - BIT(ddata->chip_info->resolution + 1);
  72                 }
  73
  74                 /*
  75                  * The part started a new conversion at the end of the above i2c
  76                  * transfer, so if the address didn't change since the last call
  77                  * everything is fine and we can return early.
  78                  * If not (which should only happen when some sort of bulk
  79                  * conversion is implemented) we have to program the new
  80                  * address. Note that this probably fails as the conversion that
  81                  * was triggered above is like not complete yet and the two
  82                  * operations have to be done in a single transfer.
  83                  */
  84                 if (ddata->addr_prev == address)
  85                         return 0;
  86         }
  87
  88         ret = i2c_smbus_write_byte(st->client,
  89                                    LTC2497_ENABLE | address);
  90         if (ret)
  91                 dev_err(&st->client->dev, "i2c transfer failed: %pe\n",
  92                         ERR_PTR(ret));
  93         return ret;
  94 }
  95
  96 static int ltc2497_probe(struct i2c_client *client)
  97 {
  98         const struct ltc2497_chip_info *chip_info;
  99         struct iio_dev *indio_dev;
 100         struct ltc2497_driverdata *st;
 101         struct device *dev = &client->dev;
 102         u32 resolution;
 103
 104         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
 105                                      I2C_FUNC_SMBUS_WRITE_BYTE))
 106                 return -EOPNOTSUPP;
 107
 108         indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
 109         if (!indio_dev)
 110                 return -ENOMEM;
 111
 112         st = iio_priv(indio_dev);
 113         i2c_set_clientdata(client, indio_dev);
 114         st->client = client;
 115         st->common_ddata.result_and_measure = ltc2497_result_and_measure;
 116
 117         chip_info = i2c_get_match_data(client);
 118         st->common_ddata.chip_info = chip_info;
 119
 120         resolution = chip_info->resolution;
 121         st->recv_size = BITS_TO_BYTES(resolution) + 1;
 122
 123         return ltc2497core_probe(dev, indio_dev);
 124 }
 125
 126 static void ltc2497_remove(struct i2c_client *client)
 127 {
 128         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 129
 130         ltc2497core_remove(indio_dev);
 131 }
 132
 133 static const struct ltc2497_chip_info ltc2497_info[] = {
 134         [TYPE_LTC2497] = {
 135                 .resolution = 16,
 136                 .name = NULL,
 137         },
 138         [TYPE_LTC2499] = {
 139                 .resolution = 24,
 140                 .name = "ltc2499",
 141         },
 142 };
 143
 144 static const struct i2c_device_id ltc2497_id[] = {
 145         { "ltc2497", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2497] },
 146         { "ltc2499", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2499] },
 147         { }
 148 };
 149 MODULE_DEVICE_TABLE(i2c, ltc2497_id);
 150
 151 static const struct of_device_id ltc2497_of_match[] = {
 152         { .compatible = "lltc,ltc2497", .data = &ltc2497_info[TYPE_LTC2497] },
 153         { .compatible = "lltc,ltc2499", .data = &ltc2497_info[TYPE_LTC2499] },
 154         {},
 155 };
 156 MODULE_DEVICE_TABLE(of, ltc2497_of_match);
 157
 158 static struct i2c_driver ltc2497_driver = {
 159         .driver = {
 160                 .name = "ltc2497",
 161                 .of_match_table = ltc2497_of_match,
 162         },
 163         .probe = ltc2497_probe,
 164         .remove = ltc2497_remove,
 165         .id_table = ltc2497_id,
 166 };
 167 module_i2c_driver(ltc2497_driver);
 168
 169 MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
 170 MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver");
 171 MODULE_LICENSE("GPL v2");