linux/drivers/iio/potentiometer/max5481.c
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   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
  31enum max5481_variant {
  32        max5481,
  33        max5482,
  34        max5483,
  35        max5484,
  36};
  37
  38struct max5481_cfg {
  39        int kohms;
  40};
  41
  42static const struct max5481_cfg max5481_cfg[] = {
  43        [max5481] = { .kohms =  10, },
  44        [max5482] = { .kohms =  50, },
  45        [max5483] = { .kohms =  10, },
  46        [max5484] = { .kohms =  50, },
  47};
  48
  49struct 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
  64static const struct iio_chan_spec max5481_channels[] = {
  65        MAX5481_CHANNEL,
  66};
  67
  68static 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
  89static 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
 104static 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
 119static const struct iio_info max5481_info = {
 120        .read_raw = max5481_read_raw,
 121        .write_raw = max5481_write_raw,
 122        .driver_module = THIS_MODULE,
 123};
 124
 125#if defined(CONFIG_OF)
 126static const struct of_device_id max5481_match[] = {
 127        { .compatible = "maxim,max5481", .data = &max5481_cfg[max5481] },
 128        { .compatible = "maxim,max5482", .data = &max5481_cfg[max5482] },
 129        { .compatible = "maxim,max5483", .data = &max5481_cfg[max5483] },
 130        { .compatible = "maxim,max5484", .data = &max5481_cfg[max5484] },
 131        { }
 132};
 133MODULE_DEVICE_TABLE(of, max5481_match);
 134#endif
 135
 136static int max5481_probe(struct spi_device *spi)
 137{
 138        struct iio_dev *indio_dev;
 139        struct max5481_data *data;
 140        const struct spi_device_id *id = spi_get_device_id(spi);
 141        const struct of_device_id *match;
 142        int ret;
 143
 144        indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
 145        if (!indio_dev)
 146                return -ENOMEM;
 147
 148        dev_set_drvdata(&spi->dev, indio_dev);
 149        data = iio_priv(indio_dev);
 150
 151        data->spi = spi;
 152
 153        match = of_match_device(of_match_ptr(max5481_match), &spi->dev);
 154        if (match)
 155                data->cfg = of_device_get_match_data(&spi->dev);
 156        else
 157                data->cfg = &max5481_cfg[id->driver_data];
 158
 159        indio_dev->name = id->name;
 160        indio_dev->dev.parent = &spi->dev;
 161        indio_dev->modes = INDIO_DIRECT_MODE;
 162
 163        /* variant specific configuration */
 164        indio_dev->info = &max5481_info;
 165        indio_dev->channels = max5481_channels;
 166        indio_dev->num_channels = ARRAY_SIZE(max5481_channels);
 167
 168        /* restore wiper from NV */
 169        ret = max5481_write_cmd(data, MAX5481_COPY_NV_TO_AB, 0);
 170        if (ret < 0)
 171                return ret;
 172
 173        return iio_device_register(indio_dev);
 174}
 175
 176static int max5481_remove(struct spi_device *spi)
 177{
 178        struct iio_dev *indio_dev = dev_get_drvdata(&spi->dev);
 179        struct max5481_data *data = iio_priv(indio_dev);
 180
 181        iio_device_unregister(indio_dev);
 182
 183        /* save wiper reg to NV reg */
 184        return max5481_write_cmd(data, MAX5481_COPY_AB_TO_NV, 0);
 185}
 186
 187static const struct spi_device_id max5481_id_table[] = {
 188        { "max5481", max5481 },
 189        { "max5482", max5482 },
 190        { "max5483", max5483 },
 191        { "max5484", max5484 },
 192        { }
 193};
 194MODULE_DEVICE_TABLE(spi, max5481_id_table);
 195
 196#if defined(CONFIG_ACPI)
 197static const struct acpi_device_id max5481_acpi_match[] = {
 198        { "max5481", max5481 },
 199        { "max5482", max5482 },
 200        { "max5483", max5483 },
 201        { "max5484", max5484 },
 202        { }
 203};
 204MODULE_DEVICE_TABLE(acpi, max5481_acpi_match);
 205#endif
 206
 207static struct spi_driver max5481_driver = {
 208        .driver = {
 209                .name  = "max5481",
 210                .owner = THIS_MODULE,
 211                .of_match_table = of_match_ptr(max5481_match),
 212                .acpi_match_table = ACPI_PTR(max5481_acpi_match),
 213        },
 214        .probe = max5481_probe,
 215        .remove = max5481_remove,
 216        .id_table = max5481_id_table,
 217};
 218
 219module_spi_driver(max5481_driver);
 220
 221MODULE_AUTHOR("Maury Anderson <maury.anderson@rockwellcollins.com>");
 222MODULE_DESCRIPTION("max5481 SPI driver");
 223MODULE_LICENSE("GPL v2");
 224