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 #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         u32 sub_lsb;
  32         /*
  33          * DMA (thus cache coherency maintenance) may require the
  34          * transfer buffers to live in their own cache lines.
  35          */
  36         union {
  37                 __be32 d32;
  38                 u8 d8[3];
  39         } data __aligned(IIO_DMA_MINALIGN);
  40 };
  41
  42 static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
  43                                       u8 address, int *val)
  44 {
  45         struct ltc2497_driverdata *st =
  46                 container_of(ddata, struct ltc2497_driverdata, common_ddata);
  47         int ret;
  48
  49         if (val) {
  50                 if (st->recv_size == 3)
  51                         ret = i2c_master_recv(st->client, (char *)&st->data.d8,
  52                                               st->recv_size);
  53                 else
  54                         ret = i2c_master_recv(st->client, (char *)&st->data.d32,
  55                                               st->recv_size);
  56                 if (ret < 0) {
  57                         dev_err(&st->client->dev, "i2c_master_recv failed\n");
  58                         return ret;
  59                 }
  60
  61                 /*
  62                  * The data format is 16/24 bit 2s complement, but with an upper sign bit on the
  63                  * resolution + 1 position, which is set for positive values only. Given this
  64                  * bit's value, subtracting BIT(resolution + 1) from the ADC's result is
  65                  * equivalent to a sign extension.
  66                  */
  67                 if (st->recv_size == 3) {
  68                         *val = (get_unaligned_be24(st->data.d8) >> st->sub_lsb)
  69                                 - BIT(ddata->chip_info->resolution + 1);
  70                 } else {
  71                         *val = (be32_to_cpu(st->data.d32) >> st->sub_lsb)
  72                                 - BIT(ddata->chip_info->resolution + 1);
  73                 }
  74
  75                 /*
  76                  * The part started a new conversion at the end of the above i2c
  77                  * transfer, so if the address didn't change since the last call
  78                  * everything is fine and we can return early.
  79                  * If not (which should only happen when some sort of bulk
  80                  * conversion is implemented) we have to program the new
  81                  * address. Note that this probably fails as the conversion that
  82                  * was triggered above is like not complete yet and the two
  83                  * operations have to be done in a single transfer.
  84                  */
  85                 if (ddata->addr_prev == address)
  86                         return 0;
  87         }
  88
  89         ret = i2c_smbus_write_byte(st->client,
  90                                    LTC2497_ENABLE | address);
  91         if (ret)
  92                 dev_err(&st->client->dev, "i2c transfer failed: %pe\n",
  93                         ERR_PTR(ret));
  94         return ret;
  95 }
  96
  97 static int ltc2497_probe(struct i2c_client *client,
  98                          const struct i2c_device_id *id)
  99 {
 100         const struct ltc2497_chip_info *chip_info;
 101         struct iio_dev *indio_dev;
 102         struct ltc2497_driverdata *st;
 103         struct device *dev = &client->dev;
 104         u32 resolution;
 105
 106         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
 107                                      I2C_FUNC_SMBUS_WRITE_BYTE))
 108                 return -EOPNOTSUPP;
 109
 110         indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
 111         if (!indio_dev)
 112                 return -ENOMEM;
 113
 114         st = iio_priv(indio_dev);
 115         i2c_set_clientdata(client, indio_dev);
 116         st->client = client;
 117         st->common_ddata.result_and_measure = ltc2497_result_and_measure;
 118
 119         chip_info = device_get_match_data(dev);
 120         if (!chip_info)
 121                 chip_info = (const struct ltc2497_chip_info *)id->driver_data;
 122         st->common_ddata.chip_info = chip_info;
 123
 124         resolution = chip_info->resolution;
 125         st->sub_lsb = 31 - (resolution + 1);
 126         st->recv_size = BITS_TO_BYTES(resolution) + 1;
 127
 128         return ltc2497core_probe(dev, indio_dev);
 129 }
 130
 131 static void ltc2497_remove(struct i2c_client *client)
 132 {
 133         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 134
 135         ltc2497core_remove(indio_dev);
 136 }
 137
 138 static const struct ltc2497_chip_info ltc2497_info[] = {
 139         [TYPE_LTC2497] = {
 140                 .resolution = 16,
 141                 .name = NULL,
 142         },
 143         [TYPE_LTC2499] = {
 144                 .resolution = 24,
 145                 .name = "ltc2499",
 146         },
 147 };
 148
 149 static const struct i2c_device_id ltc2497_id[] = {
 150         { "ltc2497", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2497] },
 151         { "ltc2499", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2499] },
 152         { }
 153 };
 154 MODULE_DEVICE_TABLE(i2c, ltc2497_id);
 155
 156 static const struct of_device_id ltc2497_of_match[] = {
 157         { .compatible = "lltc,ltc2497", .data = &ltc2497_info[TYPE_LTC2497] },
 158         { .compatible = "lltc,ltc2499", .data = &ltc2497_info[TYPE_LTC2499] },
 159         {},
 160 };
 161 MODULE_DEVICE_TABLE(of, ltc2497_of_match);
 162
 163 static struct i2c_driver ltc2497_driver = {
 164         .driver = {
 165                 .name = "ltc2497",
 166                 .of_match_table = ltc2497_of_match,
 167         },
 168         .probe = ltc2497_probe,
 169         .remove = ltc2497_remove,
 170         .id_table = ltc2497_id,
 171 };
 172 module_i2c_driver(ltc2497_driver);
 173
 174 MODULE_AUTHOR("Michael Hennerich <[email protected]>");
 175 MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver");
 176 MODULE_LICENSE("GPL v2");