drivers/iio/potentiometer/max5481.c

   1 /*
   2  * Maxim Integrated MAX5481-MAX5484 digital potentiometer driver
   3  * Copyright 2016 Rockwell Collins
   4  *
   5  * Datasheet:
   6  * http://datasheets.maximintegrated.com/en/ds/MAX5481-MAX5484.pdf
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the gnu general public license version 2 as
  10  * published by the free software foundation.
  11  *
  12  */
  13
  14 #include <linux/acpi.h>
  15 #include <linux/iio/iio.h>
  16 #include <linux/iio/sysfs.h>
  17 #include <linux/module.h>
  18 #include <linux/of.h>
  19 #include <linux/of_device.h>
  20 #include <linux/spi/spi.h>
  21
  22 /* write wiper reg */
  23 #define MAX5481_WRITE_WIPER (0 << 4)
  24 /* copy wiper reg to NV reg */
  25 #define MAX5481_COPY_AB_TO_NV (2 << 4)
  26 /* copy NV reg to wiper reg */
  27 #define MAX5481_COPY_NV_TO_AB (3 << 4)
  28
  29 #define MAX5481_MAX_POS    1023
  30
  31 enum max5481_variant {
  32         max5481,
  33         max5482,
  34         max5483,
  35         max5484,
  36 };
  37
  38 struct max5481_cfg {
  39         int kohms;
  40 };
  41
  42 static const struct max5481_cfg max5481_cfg[] = {
  43         [max5481] = { .kohms =  10, },
  44         [max5482] = { .kohms =  50, },
  45         [max5483] = { .kohms =  10, },
  46         [max5484] = { .kohms =  50, },
  47 };
  48
  49 struct max5481_data {
  50         struct spi_device *spi;
  51         const struct max5481_cfg *cfg;
  52         u8 msg[3] ____cacheline_aligned;
  53 };
  54
  55 #define MAX5481_CHANNEL {                                       \
  56         .type = IIO_RESISTANCE,                                 \
  57         .indexed = 1,                                           \
  58         .output = 1,                                            \
  59         .channel = 0,                                           \
  60         .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
  61         .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \
  62 }
  63
  64 static const struct iio_chan_spec max5481_channels[] = {
  65         MAX5481_CHANNEL,
  66 };
  67
  68 static int max5481_write_cmd(struct max5481_data *data, u8 cmd, u16 val)
  69 {
  70         struct spi_device *spi = data->spi;
  71
  72         data->msg[0] = cmd;
  73
  74         switch (cmd) {
  75         case MAX5481_WRITE_WIPER:
  76                 data->msg[1] = val >> 2;
  77                 data->msg[2] = (val & 0x3) << 6;
  78                 return spi_write(spi, data->msg, 3);
  79
  80         case MAX5481_COPY_AB_TO_NV:
  81         case MAX5481_COPY_NV_TO_AB:
  82                 return spi_write(spi, data->msg, 1);
  83
  84         default:
  85                 return -EIO;
  86         }
  87 }
  88
  89 static int max5481_read_raw(struct iio_dev *indio_dev,
  90                 struct iio_chan_spec const *chan,
  91                 int *val, int *val2, long mask)
  92 {
  93         struct max5481_data *data = iio_priv(indio_dev);
  94
  95         if (mask != IIO_CHAN_INFO_SCALE)
  96                 return -EINVAL;
  97
  98         *val = 1000 * data->cfg->kohms;
  99         *val2 = MAX5481_MAX_POS;
 100
 101         return IIO_VAL_FRACTIONAL;
 102 }
 103
 104 static int max5481_write_raw(struct iio_dev *indio_dev,
 105                 struct iio_chan_spec const *chan,
 106                 int val, int val2, long mask)
 107 {
 108         struct max5481_data *data = iio_priv(indio_dev);
 109
 110         if (mask != IIO_CHAN_INFO_RAW)
 111                 return -EINVAL;
 112
 113         if (val < 0 || val > MAX5481_MAX_POS)
 114                 return -EINVAL;
 115
 116         return max5481_write_cmd(data, MAX5481_WRITE_WIPER, val);
 117 }
 118
 119 static const struct iio_info max5481_info = {
 120         .read_raw = max5481_read_raw,
 121         .write_raw = max5481_write_raw,
 122 };
 123
 124 #if defined(CONFIG_OF)
 125 static const struct of_device_id max5481_match[] = {
 126         { .compatible = "maxim,max5481", .data = &max5481_cfg[max5481] },
 127         { .compatible = "maxim,max5482", .data = &max5481_cfg[max5482] },
 128         { .compatible = "maxim,max5483", .data = &max5481_cfg[max5483] },
 129         { .compatible = "maxim,max5484", .data = &max5481_cfg[max5484] },
 130         { }
 131 };
 132 MODULE_DEVICE_TABLE(of, max5481_match);
 133 #endif
 134
 135 static int max5481_probe(struct spi_device *spi)
 136 {
 137         struct iio_dev *indio_dev;
 138         struct max5481_data *data;
 139         const struct spi_device_id *id = spi_get_device_id(spi);
 140         const struct of_device_id *match;
 141         int ret;
 142
 143         indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
 144         if (!indio_dev)
 145                 return -ENOMEM;
 146
 147         dev_set_drvdata(&spi->dev, indio_dev);
 148         data = iio_priv(indio_dev);
 149
 150         data->spi = spi;
 151
 152         match = of_match_device(of_match_ptr(max5481_match), &spi->dev);
 153         if (match)
 154                 data->cfg = of_device_get_match_data(&spi->dev);
 155         else
 156                 data->cfg = &max5481_cfg[id->driver_data];
 157
 158         indio_dev->name = id->name;
 159         indio_dev->dev.parent = &spi->dev;
 160         indio_dev->modes = INDIO_DIRECT_MODE;
 161
 162         /* variant specific configuration */
 163         indio_dev->info = &max5481_info;
 164         indio_dev->channels = max5481_channels;
 165         indio_dev->num_channels = ARRAY_SIZE(max5481_channels);
 166
 167         /* restore wiper from NV */
 168         ret = max5481_write_cmd(data, MAX5481_COPY_NV_TO_AB, 0);
 169         if (ret < 0)
 170                 return ret;
 171
 172         return iio_device_register(indio_dev);
 173 }
 174
 175 static int max5481_remove(struct spi_device *spi)
 176 {
 177         struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
 178         struct max5481_data *data = iio_priv(indio_dev);
 179
 180         iio_device_unregister(indio_dev);
 181
 182         /* save wiper reg to NV reg */
 183         return max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0);
 184 }
 185
 186 static const struct spi_device_id max5481_id_table[] = {
 187         { "max5481", max5481 },
 188         { "max5482", max5482 },
 189         { "max5483", max5483 },
 190         { "max5484", max5484 },
 191         { }
 192 };
 193 MODULE_DEVICE_TABLE(spi, max5481_id_table);
 194
 195 #if defined(CONFIG_ACPI)
 196 static const struct acpi_device_id max5481_acpi_match[] = {
 197         { "max5481", max5481 },
 198         { "max5482", max5482 },
 199         { "max5483", max5483 },
 200         { "max5484", max5484 },
 201         { }
 202 };
 203 MODULE_DEVICE_TABLE(acpi, max5481_acpi_match);
 204 #endif
 205
 206 static struct spi_driver max5481_driver = {
 207         .driver = {
 208                 .name  = "max5481",
 209                 .of_match_table = of_match_ptr(max5481_match),
 210                 .acpi_match_table = ACPI_PTR(max5481_acpi_match),
 211         },
 212         .probe = max5481_probe,
 213         .remove = max5481_remove,
 214         .id_table = max5481_id_table,
 215 };
 216
 217 module_spi_driver(max5481_driver);
 218
 219 MODULE_AUTHOR("Maury Anderson <maury.anderson@rockwellcollins.com>");
 220 MODULE_DESCRIPTION("max5481 SPI driver");
 221 MODULE_LICENSE("GPL v2");