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 <linux/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
  31 struct max11100_state {
  32         struct regulator *vref_reg;
  33         struct spi_device *spi;
  34
  35         /*
  36          * DMA (thus cache coherency maintenance) may require the
  37          * transfer buffers to live in their own cache lines.
  38          */
  39         u8 buffer[3] __aligned(IIO_DMA_MINALIGN);
  40 };
  41
  42 static 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
  50 static 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
  72 static 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
 101 static const struct iio_info max11100_info = {
 102         .read_raw = max11100_read_raw,
 103 };
 104
 105 static void max11100_regulator_disable(void *reg)
 106 {
 107         regulator_disable(reg);
 108 }
 109
 110 static 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
 145 static const struct of_device_id max11100_ids[] = {
 146         { .compatible = "maxim,max11100" },
 147         { }
 148 };
 149 MODULE_DEVICE_TABLE(of, max11100_ids);
 150
 151 static struct spi_driver max11100_driver = {
 152         .driver = {
 153                 .name   = "max11100",
 154                 .of_match_table = max11100_ids,
 155         },
 156         .probe          = max11100_probe,
 157 };
 158
 159 module_spi_driver(max11100_driver);
 160
 161 MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
 162 MODULE_DESCRIPTION("Maxim max11100 ADC Driver");
 163 MODULE_LICENSE("GPL v2");