iio: adc: Add MAX1241 driver

Add driver for the Maxim MAX1241 12-bit, single-channel ADC.

Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Alexandru Lazar <alazar@startmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index a079651..c40b3c2 100644 (file)
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -630,6 +630,16 @@ config MAX1118
          To compile this driver as a module, choose M here: the module will be
          called max1118.
 
+config MAX1241
+       tristate "Maxim max1241 ADC driver"
+       depends on SPI_MASTER
+       help
+         Say yes here to build support for Maxim max1241 12-bit, single-channel
+         ADC.
+
+         To compile this driver as a module, choose M here: the module will be
+         called max1241.
+
 config MAX1363
        tristate "Maxim max1363 ADC driver"
        depends on I2C

diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 5972277..62169ab 100644 (file)
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -59,6 +59,7 @@ obj-$(CONFIG_LTC2497) += ltc2497.o ltc2497-core.o
 obj-$(CONFIG_MAX1027) += max1027.o
 obj-$(CONFIG_MAX11100) += max11100.o
 obj-$(CONFIG_MAX1118) += max1118.o
+obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MAX9611) += max9611.o
 obj-$(CONFIG_MCP320X) += mcp320x.o

diff --git a/drivers/iio/adc/max1241.c b/drivers/iio/adc/max1241.c
new file mode 100644 (file)
index 0000000..541939c
--- /dev/null
+++ b/drivers/iio/adc/max1241.c
@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MAX1241 low-power, 12-bit serial ADC
+ *
+ * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#define MAX1241_VAL_MASK GENMASK(11, 0)
+#define MAX1241_SHUTDOWN_DELAY_USEC 4
+
+enum max1241_id {
+       max1241,
+};
+
+struct max1241 {
+       struct spi_device *spi;
+       struct mutex lock;
+       struct regulator *vdd;
+       struct regulator *vref;
+       struct gpio_desc *shutdown;
+
+       __be16 data ____cacheline_aligned;
+};
+
+static const struct iio_chan_spec max1241_channels[] = {
+       {
+               .type = IIO_VOLTAGE,
+               .indexed = 1,
+               .channel = 0,
+               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+                               BIT(IIO_CHAN_INFO_SCALE),
+       },
+};
+
+static int max1241_read(struct max1241 *adc)
+{
+       struct spi_transfer xfers[] = {
+               /*
+                * Begin conversion by bringing /CS low for at least
+                * tconv us.
+                */
+               {
+                       .len = 0,
+                       .delay.value = 8,
+                       .delay.unit = SPI_DELAY_UNIT_USECS,
+               },
+               /*
+                * Then read two bytes of data in our RX buffer.
+                */
+               {
+                       .rx_buf = &adc->data,
+                       .len = 2,
+               },
+       };
+
+       return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
+}
+
+static int max1241_read_raw(struct iio_dev *indio_dev,
+                       struct iio_chan_spec const *chan,
+                       int *val, int *val2, long mask)
+{
+       int ret, vref_uV;
+       struct max1241 *adc = iio_priv(indio_dev);
+
+       switch (mask) {
+       case IIO_CHAN_INFO_RAW:
+               mutex_lock(&adc->lock);
+
+               if (adc->shutdown) {
+                       gpiod_set_value(adc->shutdown, 0);
+                       udelay(MAX1241_SHUTDOWN_DELAY_USEC);
+                       ret = max1241_read(adc);
+                       gpiod_set_value(adc->shutdown, 1);
+               } else
+                       ret = max1241_read(adc);
+
+               if (ret) {
+                       mutex_unlock(&adc->lock);
+                       return ret;
+               }
+
+               *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;
+
+               mutex_unlock(&adc->lock);
+               return IIO_VAL_INT;
+       case IIO_CHAN_INFO_SCALE:
+               vref_uV = regulator_get_voltage(adc->vref);
+
+               if (vref_uV < 0)
+                       return vref_uV;
+
+               *val = vref_uV / 1000;
+               *val2 = 12;
+
+               return IIO_VAL_FRACTIONAL_LOG2;
+       default:
+               return -EINVAL;
+       }
+}
+
+static const struct iio_info max1241_info = {
+       .read_raw = max1241_read_raw,
+};
+
+static void max1241_disable_vdd_action(void *data)
+{
+       struct max1241 *adc = data;
+       struct device *dev = &adc->spi->dev;
+       int err;
+
+       err = regulator_disable(adc->vdd);
+       if (err)
+               dev_err(dev, "could not disable vdd regulator.\n");
+}
+
+static void max1241_disable_vref_action(void *data)
+{
+       struct max1241 *adc = data;
+       struct device *dev = &adc->spi->dev;
+       int err;
+
+       err = regulator_disable(adc->vref);
+       if (err)
+               dev_err(dev, "could not disable vref regulator.\n");
+}
+
+static int max1241_probe(struct spi_device *spi)
+{
+       struct device *dev = &spi->dev;
+       struct iio_dev *indio_dev;
+       struct max1241 *adc;
+       int ret;
+
+       indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
+       if (!indio_dev)
+               return -ENOMEM;
+
+       adc = iio_priv(indio_dev);
+       adc->spi = spi;
+       mutex_init(&adc->lock);
+
+       spi_set_drvdata(spi, indio_dev);
+
+       adc->vdd = devm_regulator_get(dev, "vdd");
+       if (IS_ERR(adc->vdd)) {
+               dev_err(dev, "failed to get vdd regulator\n");
+               return PTR_ERR(adc->vdd);
+       }
+
+       ret = regulator_enable(adc->vdd);
+       if (ret)
+               return ret;
+
+       ret = devm_add_action_or_reset(dev, max1241_disable_vdd_action, adc);
+       if (ret) {
+               dev_err(dev, "could not set up vdd regulator cleanup action\n");
+               return ret;
+       }
+
+       adc->vref = devm_regulator_get(dev, "vref");
+       if (IS_ERR(adc->vref)) {
+               dev_err(dev, "failed to get vref regulator\n");
+               return PTR_ERR(adc->vref);
+       }
+
+       ret = regulator_enable(adc->vref);
+       if (ret)
+               return ret;
+
+       ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);
+       if (ret) {
+               dev_err(dev, "could not set up vref regulator cleanup action\n");
+               return ret;
+       }
+
+       adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",
+                                               GPIOD_OUT_HIGH);
+       if (IS_ERR(adc->shutdown))
+               return PTR_ERR(adc->shutdown);
+
+       if (adc->shutdown)
+               dev_dbg(dev, "shutdown pin passed, low-power mode enabled");
+       else
+               dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");
+
+       indio_dev->name = spi_get_device_id(spi)->name;
+       indio_dev->dev.parent = dev;
+       indio_dev->info = &max1241_info;
+       indio_dev->modes = INDIO_DIRECT_MODE;
+       indio_dev->channels = max1241_channels;
+       indio_dev->num_channels = ARRAY_SIZE(max1241_channels);
+
+       return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct spi_device_id max1241_id[] = {
+       { "max1241", max1241 },
+       {}
+};
+
+static const struct of_device_id max1241_dt_ids[] = {
+       { .compatible = "maxim,max1241" },
+       {}
+};
+MODULE_DEVICE_TABLE(of, max1241_dt_ids);
+
+static struct spi_driver max1241_spi_driver = {
+       .driver = {
+               .name = "max1241",
+               .of_match_table = max1241_dt_ids,
+       },
+       .probe = max1241_probe,
+       .id_table = max1241_id,
+};
+module_spi_driver(max1241_spi_driver);
+
+MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
+MODULE_DESCRIPTION("MAX1241 ADC driver");
+MODULE_LICENSE("GPL v2");