LXR linux/drivers/iio/adc/max11100.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * iio/adc/max11100.c
   4 * Maxim max11100 ADC Driver with IIO interface
   5 *
   6 * Copyright (C) 2016-17 Renesas Electronics Corporation
   7 * Copyright (C) 2016-17 Jacopo Mondi
   8 */
   9#include <linux/delay.h>
  10#include <linux/kernel.h>
  11#include <linux/mod_devicetable.h>
  12#include <linux/module.h>
  13#include <linux/regulator/consumer.h>
  14#include <linux/spi/spi.h>
  15#include <asm/unaligned.h>
  16
  17#include <linux/iio/iio.h>
  18#include <linux/iio/driver.h>
  19
  20/*
  21 * LSB is the ADC single digital step
  22 * 1 LSB = (vref_mv / 2 ^ 16)
  23 *
  24 * LSB is used to calculate analog voltage value
  25 * from the number of ADC steps count
  26 *
  27 * Ain = (count * LSB)
  28 */
  29#define MAX11100_LSB_DIV                (1 << 16)
  30
  31struct max11100_state {
  32        struct regulator *vref_reg;
  33        struct spi_device *spi;
  34
  35        /*
  36         * DMA (thus cache coherency maintenance) requires the
  37         * transfer buffers to live in their own cache lines.
  38         */
  39        u8 buffer[3] ____cacheline_aligned;
  40};
  41
  42static const struct iio_chan_spec max11100_channels[] = {
  43        { /* [0] */
  44                .type = IIO_VOLTAGE,
  45                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  46                                      BIT(IIO_CHAN_INFO_SCALE),
  47        },
  48};
  49
  50static int max11100_read_single(struct iio_dev *indio_dev, int *val)
  51{
  52        int ret;
  53        struct max11100_state *state = iio_priv(indio_dev);
  54
  55        ret = spi_read(state->spi, state->buffer, sizeof(state->buffer));
  56        if (ret) {
  57                dev_err(&indio_dev->dev, "SPI transfer failed\n");
  58                return ret;
  59        }
  60
  61        /* the first 8 bits sent out from ADC must be 0s */
  62        if (state->buffer[0]) {
  63                dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n");
  64                return -EINVAL;
  65        }
  66
  67        *val = get_unaligned_be16(&state->buffer[1]);
  68
  69        return 0;
  70}
  71
  72static int max11100_read_raw(struct iio_dev *indio_dev,
  73                             struct iio_chan_spec const *chan,
  74                             int *val, int *val2, long info)
  75{
  76        int ret, vref_uv;
  77        struct max11100_state *state = iio_priv(indio_dev);
  78
  79        switch (info) {
  80        case IIO_CHAN_INFO_RAW:
  81                ret = max11100_read_single(indio_dev, val);
  82                if (ret)
  83                        return ret;
  84
  85                return IIO_VAL_INT;
  86
  87        case IIO_CHAN_INFO_SCALE:
  88                vref_uv = regulator_get_voltage(state->vref_reg);
  89                if (vref_uv < 0)
  90                        /* dummy regulator "get_voltage" returns -EINVAL */
  91                        return -EINVAL;
  92
  93                *val =  vref_uv / 1000;
  94                *val2 = MAX11100_LSB_DIV;
  95                return IIO_VAL_FRACTIONAL;
  96        }
  97
  98        return -EINVAL;
  99}
 100
 101static const struct iio_info max11100_info = {
 102        .read_raw = max11100_read_raw,
 103};
 104
 105static void max11100_regulator_disable(void *reg)
 106{
 107        regulator_disable(reg);
 108}
 109
 110static int max11100_probe(struct spi_device *spi)
 111{
 112        int ret;
 113        struct iio_dev *indio_dev;
 114        struct max11100_state *state;
 115
 116        indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
 117        if (!indio_dev)
 118                return -ENOMEM;
 119
 120        state = iio_priv(indio_dev);
 121        state->spi = spi;
 122
 123        indio_dev->name = "max11100";
 124        indio_dev->info = &max11100_info;
 125        indio_dev->modes = INDIO_DIRECT_MODE;
 126        indio_dev->channels = max11100_channels;
 127        indio_dev->num_channels = ARRAY_SIZE(max11100_channels);
 128
 129        state->vref_reg = devm_regulator_get(&spi->dev, "vref");
 130        if (IS_ERR(state->vref_reg))
 131                return PTR_ERR(state->vref_reg);
 132
 133        ret = regulator_enable(state->vref_reg);
 134        if (ret)
 135                return ret;
 136
 137        ret = devm_add_action_or_reset(&spi->dev, max11100_regulator_disable,
 138                                       state->vref_reg);
 139        if (ret)
 140                return ret;
 141
 142        return devm_iio_device_register(&spi->dev, indio_dev);
 143}
 144
 145static const struct of_device_id max11100_ids[] = {
 146        {.compatible = "maxim,max11100"},
 147        { },
 148};
 149MODULE_DEVICE_TABLE(of, max11100_ids);
 150
 151static struct spi_driver max11100_driver = {
 152        .driver = {
 153                .name   = "max11100",
 154                .of_match_table = max11100_ids,
 155        },
 156        .probe          = max11100_probe,
 157};
 158
 159module_spi_driver(max11100_driver);
 160
 161MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
 162MODULE_DESCRIPTION("Maxim max11100 ADC Driver");
 163MODULE_LICENSE("GPL v2");
 164