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/module.h>
  12 #include <linux/regulator/consumer.h>
  13 #include <linux/spi/spi.h>
  14
  15 #include <linux/iio/iio.h>
  16 #include <linux/iio/driver.h>
  17
  18 /*
  19  * LSB is the ADC single digital step
  20  * 1 LSB = (vref_mv / 2 ^ 16)
  21  *
  22  * LSB is used to calculate analog voltage value
  23  * from the number of ADC steps count
  24  *
  25  * Ain = (count * LSB)
  26  */
  27 #define MAX11100_LSB_DIV                (1 << 16)
  28
  29 struct max11100_state {
  30         struct regulator *vref_reg;
  31         struct spi_device *spi;
  32
  33         /*
  34          * DMA (thus cache coherency maintenance) requires the
  35          * transfer buffers to live in their own cache lines.
  36          */
  37         u8 buffer[3] ____cacheline_aligned;
  38 };
  39
  40 static struct iio_chan_spec max11100_channels[] = {
  41         { /* [0] */
  42                 .type = IIO_VOLTAGE,
  43                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  44                                       BIT(IIO_CHAN_INFO_SCALE),
  45         },
  46 };
  47
  48 static int max11100_read_single(struct iio_dev *indio_dev, int *val)
  49 {
  50         int ret;
  51         struct max11100_state *state = iio_priv(indio_dev);
  52
  53         ret = spi_read(state->spi, state->buffer, sizeof(state->buffer));
  54         if (ret) {
  55                 dev_err(&indio_dev->dev, "SPI transfer failed\n");
  56                 return ret;
  57         }
  58
  59         /* the first 8 bits sent out from ADC must be 0s */
  60         if (state->buffer[0]) {
  61                 dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n");
  62                 return -EINVAL;
  63         }
  64
  65         *val = (state->buffer[1] << 8) | state->buffer[2];
  66
  67         return 0;
  68 }
  69
  70 static int max11100_read_raw(struct iio_dev *indio_dev,
  71                              struct iio_chan_spec const *chan,
  72                              int *val, int *val2, long info)
  73 {
  74         int ret, vref_uv;
  75         struct max11100_state *state = iio_priv(indio_dev);
  76
  77         switch (info) {
  78         case IIO_CHAN_INFO_RAW:
  79                 ret = max11100_read_single(indio_dev, val);
  80                 if (ret)
  81                         return ret;
  82
  83                 return IIO_VAL_INT;
  84
  85         case IIO_CHAN_INFO_SCALE:
  86                 vref_uv = regulator_get_voltage(state->vref_reg);
  87                 if (vref_uv < 0)
  88                         /* dummy regulator "get_voltage" returns -EINVAL */
  89                         return -EINVAL;
  90
  91                 *val =  vref_uv / 1000;
  92                 *val2 = MAX11100_LSB_DIV;
  93                 return IIO_VAL_FRACTIONAL;
  94         }
  95
  96         return -EINVAL;
  97 }
  98
  99 static const struct iio_info max11100_info = {
 100         .read_raw = max11100_read_raw,
 101 };
 102
 103 static int max11100_probe(struct spi_device *spi)
 104 {
 105         int ret;
 106         struct iio_dev *indio_dev;
 107         struct max11100_state *state;
 108
 109         indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
 110         if (!indio_dev)
 111                 return -ENOMEM;
 112
 113         spi_set_drvdata(spi, indio_dev);
 114
 115         state = iio_priv(indio_dev);
 116         state->spi = spi;
 117
 118         indio_dev->dev.parent = &spi->dev;
 119         indio_dev->dev.of_node = spi->dev.of_node;
 120         indio_dev->name = "max11100";
 121         indio_dev->info = &max11100_info;
 122         indio_dev->modes = INDIO_DIRECT_MODE;
 123         indio_dev->channels = max11100_channels;
 124         indio_dev->num_channels = ARRAY_SIZE(max11100_channels);
 125
 126         state->vref_reg = devm_regulator_get(&spi->dev, "vref");
 127         if (IS_ERR(state->vref_reg))
 128                 return PTR_ERR(state->vref_reg);
 129
 130         ret = regulator_enable(state->vref_reg);
 131         if (ret)
 132                 return ret;
 133
 134         ret = iio_device_register(indio_dev);
 135         if (ret)
 136                 goto disable_regulator;
 137
 138         return 0;
 139
 140 disable_regulator:
 141         regulator_disable(state->vref_reg);
 142
 143         return ret;
 144 }
 145
 146 static int max11100_remove(struct spi_device *spi)
 147 {
 148         struct iio_dev *indio_dev = spi_get_drvdata(spi);
 149         struct max11100_state *state = iio_priv(indio_dev);
 150
 151         iio_device_unregister(indio_dev);
 152         regulator_disable(state->vref_reg);
 153
 154         return 0;
 155 }
 156
 157 static const struct of_device_id max11100_ids[] = {
 158         {.compatible = "maxim,max11100"},
 159         { },
 160 };
 161 MODULE_DEVICE_TABLE(of, max11100_ids);
 162
 163 static struct spi_driver max11100_driver = {
 164         .driver = {
 165                 .name   = "max11100",
 166                 .of_match_table = of_match_ptr(max11100_ids),
 167         },
 168         .probe          = max11100_probe,
 169         .remove         = max11100_remove,
 170 };
 171
 172 module_spi_driver(max11100_driver);
 173
 174 MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
 175 MODULE_DESCRIPTION("Maxim max11100 ADC Driver");
 176 MODULE_LICENSE("GPL v2");