drivers/iio/adc/max1241.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * MAX1241 low-power, 12-bit serial ADC
   4  *
   5  * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
   6  */
   7
   8 #include <linux/delay.h>
   9 #include <linux/gpio/consumer.h>
  10 #include <linux/iio/iio.h>
  11 #include <linux/module.h>
  12 #include <linux/regulator/consumer.h>
  13 #include <linux/spi/spi.h>
  14
  15 #define MAX1241_VAL_MASK GENMASK(11, 0)
  16 #define MAX1241_SHUTDOWN_DELAY_USEC 4
  17
  18 enum max1241_id {
  19         max1241,
  20 };
  21
  22 struct max1241 {
  23         struct spi_device *spi;
  24         struct mutex lock;
  25         struct regulator *vref;
  26         struct gpio_desc *shutdown;
  27
  28         __be16 data __aligned(IIO_DMA_MINALIGN);
  29 };
  30
  31 static const struct iio_chan_spec max1241_channels[] = {
  32         {
  33                 .type = IIO_VOLTAGE,
  34                 .indexed = 1,
  35                 .channel = 0,
  36                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  37                                 BIT(IIO_CHAN_INFO_SCALE),
  38         },
  39 };
  40
  41 static int max1241_read(struct max1241 *adc)
  42 {
  43         struct spi_transfer xfers[] = {
  44                 /*
  45                  * Begin conversion by bringing /CS low for at least
  46                  * tconv us.
  47                  */
  48                 {
  49                         .len = 0,
  50                         .delay.value = 8,
  51                         .delay.unit = SPI_DELAY_UNIT_USECS,
  52                 },
  53                 /*
  54                  * Then read two bytes of data in our RX buffer.
  55                  */
  56                 {
  57                         .rx_buf = &adc->data,
  58                         .len = 2,
  59                 },
  60         };
  61
  62         return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
  63 }
  64
  65 static int max1241_read_raw(struct iio_dev *indio_dev,
  66                         struct iio_chan_spec const *chan,
  67                         int *val, int *val2, long mask)
  68 {
  69         int ret, vref_uV;
  70         struct max1241 *adc = iio_priv(indio_dev);
  71
  72         switch (mask) {
  73         case IIO_CHAN_INFO_RAW:
  74                 mutex_lock(&adc->lock);
  75
  76                 if (adc->shutdown) {
  77                         gpiod_set_value(adc->shutdown, 0);
  78                         udelay(MAX1241_SHUTDOWN_DELAY_USEC);
  79                         ret = max1241_read(adc);
  80                         gpiod_set_value(adc->shutdown, 1);
  81                 } else
  82                         ret = max1241_read(adc);
  83
  84                 if (ret) {
  85                         mutex_unlock(&adc->lock);
  86                         return ret;
  87                 }
  88
  89                 *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
  90
  91                 mutex_unlock(&adc->lock);
  92                 return IIO_VAL_INT;
  93         case IIO_CHAN_INFO_SCALE:
  94                 vref_uV = regulator_get_voltage(adc->vref);
  95
  96                 if (vref_uV < 0)
  97                         return vref_uV;
  98
  99                 *val = vref_uV / 1000;
 100                 *val2 = 12;
 101
 102                 return IIO_VAL_FRACTIONAL_LOG2;
 103         default:
 104                 return -EINVAL;
 105         }
 106 }
 107
 108 static const struct iio_info max1241_info = {
 109         .read_raw = max1241_read_raw,
 110 };
 111
 112 static void max1241_disable_vref_action(void *data)
 113 {
 114         struct max1241 *adc = data;
 115         struct device *dev = &adc->spi->dev;
 116         int err;
 117
 118         err = regulator_disable(adc->vref);
 119         if (err)
 120                 dev_err(dev, "could not disable vref regulator.\n");
 121 }
 122
 123 static int max1241_probe(struct spi_device *spi)
 124 {
 125         struct device *dev = &spi->dev;
 126         struct iio_dev *indio_dev;
 127         struct max1241 *adc;
 128         int ret;
 129
 130         indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
 131         if (!indio_dev)
 132                 return -ENOMEM;
 133
 134         adc = iio_priv(indio_dev);
 135         adc->spi = spi;
 136         mutex_init(&adc->lock);
 137
 138         ret = devm_regulator_get_enable(dev, "vdd");
 139         if (ret)
 140                 return dev_err_probe(dev, ret,
 141                                      "failed to get/enable vdd regulator\n");
 142
 143         adc->vref = devm_regulator_get(dev, "vref");
 144         if (IS_ERR(adc->vref))
 145                 return dev_err_probe(dev, PTR_ERR(adc->vref),
 146                                      "failed to get vref regulator\n");
 147
 148         ret = regulator_enable(adc->vref);
 149         if (ret)
 150                 return ret;
 151
 152         ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);
 153         if (ret) {
 154                 dev_err(dev, "could not set up vref regulator cleanup action\n");
 155                 return ret;
 156         }
 157
 158         adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",
 159                                                 GPIOD_OUT_HIGH);
 160         if (IS_ERR(adc->shutdown))
 161                 return dev_err_probe(dev, PTR_ERR(adc->shutdown),
 162                                      "cannot get shutdown gpio\n");
 163
 164         if (adc->shutdown)
 165                 dev_dbg(dev, "shutdown pin passed, low-power mode enabled");
 166         else
 167                 dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");
 168
 169         indio_dev->name = spi_get_device_id(spi)->name;
 170         indio_dev->info = &max1241_info;
 171         indio_dev->modes = INDIO_DIRECT_MODE;
 172         indio_dev->channels = max1241_channels;
 173         indio_dev->num_channels = ARRAY_SIZE(max1241_channels);
 174
 175         return devm_iio_device_register(dev, indio_dev);
 176 }
 177
 178 static const struct spi_device_id max1241_id[] = {
 179         { "max1241", max1241 },
 180         {}
 181 };
 182
 183 static const struct of_device_id max1241_dt_ids[] = {
 184         { .compatible = "maxim,max1241" },
 185         {}
 186 };
 187 MODULE_DEVICE_TABLE(of, max1241_dt_ids);
 188
 189 static struct spi_driver max1241_spi_driver = {
 190         .driver = {
 191                 .name = "max1241",
 192                 .of_match_table = max1241_dt_ids,
 193         },
 194         .probe = max1241_probe,
 195         .id_table = max1241_id,
 196 };
 197 module_spi_driver(max1241_spi_driver);
 198
 199 MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
 200 MODULE_DESCRIPTION("MAX1241 ADC driver");
 201 MODULE_LICENSE("GPL v2");