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 *vdd;
  26         struct regulator *vref;
  27         struct gpio_desc *shutdown;
  28
  29         __be16 data ____cacheline_aligned;
  30 };
  31
  32 static const struct iio_chan_spec max1241_channels[] = {
  33         {
  34                 .type = IIO_VOLTAGE,
  35                 .indexed = 1,
  36                 .channel = 0,
  37                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  38                                 BIT(IIO_CHAN_INFO_SCALE),
  39         },
  40 };
  41
  42 static int max1241_read(struct max1241 *adc)
  43 {
  44         struct spi_transfer xfers[] = {
  45                 /*
  46                  * Begin conversion by bringing /CS low for at least
  47                  * tconv us.
  48                  */
  49                 {
  50                         .len = 0,
  51                         .delay.value = 8,
  52                         .delay.unit = SPI_DELAY_UNIT_USECS,
  53                 },
  54                 /*
  55                  * Then read two bytes of data in our RX buffer.
  56                  */
  57                 {
  58                         .rx_buf = &adc->data,
  59                         .len = 2,
  60                 },
  61         };
  62
  63         return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
  64 }
  65
  66 static int max1241_read_raw(struct iio_dev *indio_dev,
  67                         struct iio_chan_spec const *chan,
  68                         int *val, int *val2, long mask)
  69 {
  70         int ret, vref_uV;
  71         struct max1241 *adc = iio_priv(indio_dev);
  72
  73         switch (mask) {
  74         case IIO_CHAN_INFO_RAW:
  75                 mutex_lock(&adc->lock);
  76
  77                 if (adc->shutdown) {
  78                         gpiod_set_value(adc->shutdown, 0);
  79                         udelay(MAX1241_SHUTDOWN_DELAY_USEC);
  80                         ret = max1241_read(adc);
  81                         gpiod_set_value(adc->shutdown, 1);
  82                 } else
  83                         ret = max1241_read(adc);
  84
  85                 if (ret) {
  86                         mutex_unlock(&adc->lock);
  87                         return ret;
  88                 }
  89
  90                 *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
  91
  92                 mutex_unlock(&adc->lock);
  93                 return IIO_VAL_INT;
  94         case IIO_CHAN_INFO_SCALE:
  95                 vref_uV = regulator_get_voltage(adc->vref);
  96
  97                 if (vref_uV < 0)
  98                         return vref_uV;
  99
 100                 *val = vref_uV / 1000;
 101                 *val2 = 12;
 102
 103                 return IIO_VAL_FRACTIONAL_LOG2;
 104         default:
 105                 return -EINVAL;
 106         }
 107 }
 108
 109 static const struct iio_info max1241_info = {
 110         .read_raw = max1241_read_raw,
 111 };
 112
 113 static void max1241_disable_vdd_action(void *data)
 114 {
 115         struct max1241 *adc = data;
 116         struct device *dev = &adc->spi->dev;
 117         int err;
 118
 119         err = regulator_disable(adc->vdd);
 120         if (err)
 121                 dev_err(dev, "could not disable vdd regulator.\n");
 122 }
 123
 124 static void max1241_disable_vref_action(void *data)
 125 {
 126         struct max1241 *adc = data;
 127         struct device *dev = &adc->spi->dev;
 128         int err;
 129
 130         err = regulator_disable(adc->vref);
 131         if (err)
 132                 dev_err(dev, "could not disable vref regulator.\n");
 133 }
 134
 135 static int max1241_probe(struct spi_device *spi)
 136 {
 137         struct device *dev = &spi->dev;
 138         struct iio_dev *indio_dev;
 139         struct max1241 *adc;
 140         int ret;
 141
 142         indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
 143         if (!indio_dev)
 144                 return -ENOMEM;
 145
 146         adc = iio_priv(indio_dev);
 147         adc->spi = spi;
 148         mutex_init(&adc->lock);
 149
 150         spi_set_drvdata(spi, indio_dev);
 151
 152         adc->vdd = devm_regulator_get(dev, "vdd");
 153         if (IS_ERR(adc->vdd)) {
 154                 dev_err(dev, "failed to get vdd regulator\n");
 155                 return PTR_ERR(adc->vdd);
 156         }
 157
 158         ret = regulator_enable(adc->vdd);
 159         if (ret)
 160                 return ret;
 161
 162         ret = devm_add_action_or_reset(dev, max1241_disable_vdd_action, adc);
 163         if (ret) {
 164                 dev_err(dev, "could not set up vdd regulator cleanup action\n");
 165                 return ret;
 166         }
 167
 168         adc->vref = devm_regulator_get(dev, "vref");
 169         if (IS_ERR(adc->vref)) {
 170                 dev_err(dev, "failed to get vref regulator\n");
 171                 return PTR_ERR(adc->vref);
 172         }
 173
 174         ret = regulator_enable(adc->vref);
 175         if (ret)
 176                 return ret;
 177
 178         ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);
 179         if (ret) {
 180                 dev_err(dev, "could not set up vref regulator cleanup action\n");
 181                 return ret;
 182         }
 183
 184         adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",
 185                                                 GPIOD_OUT_HIGH);
 186         if (IS_ERR(adc->shutdown))
 187                 return PTR_ERR(adc->shutdown);
 188
 189         if (adc->shutdown)
 190                 dev_dbg(dev, "shutdown pin passed, low-power mode enabled");
 191         else
 192                 dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");
 193
 194         indio_dev->name = spi_get_device_id(spi)->name;
 195         indio_dev->info = &max1241_info;
 196         indio_dev->modes = INDIO_DIRECT_MODE;
 197         indio_dev->channels = max1241_channels;
 198         indio_dev->num_channels = ARRAY_SIZE(max1241_channels);
 199
 200         return devm_iio_device_register(dev, indio_dev);
 201 }
 202
 203 static const struct spi_device_id max1241_id[] = {
 204         { "max1241", max1241 },
 205         {}
 206 };
 207
 208 static const struct of_device_id max1241_dt_ids[] = {
 209         { .compatible = "maxim,max1241" },
 210         {}
 211 };
 212 MODULE_DEVICE_TABLE(of, max1241_dt_ids);
 213
 214 static struct spi_driver max1241_spi_driver = {
 215         .driver = {
 216                 .name = "max1241",
 217                 .of_match_table = max1241_dt_ids,
 218         },
 219         .probe = max1241_probe,
 220         .id_table = max1241_id,
 221 };
 222 module_spi_driver(max1241_spi_driver);
 223
 224 MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
 225 MODULE_DESCRIPTION("MAX1241 ADC driver");
 226 MODULE_LICENSE("GPL v2");