[PATCH 1/2] iio: adc: Add MAX1241 driver

Alexandru Lazar
2020-03-18T20:24:24Z

Add driver for the Maxim MAX1241 12-bit, single-channel ADC. The driver
includes support for this device's low-power operation mode.

Signed-off-by: Alexandru Lazar <alazar@startmail.com>
---
drivers/iio/adc/Kconfig | 10 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/max1241.c | 206 ++++++++++++++++++++++++++++++++++++++
3 files changed, 217 insertions(+)
create mode 100644 drivers/iio/adc/max1241.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 5d8540b7b427..4254633147af 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -566,6 +566,16 @@ 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 max1118.
+
config MAX1363
tristate "Maxim max1363 ADC driver"
depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index a1f1fbec0f87..37d6f17559dc 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_LTC2497) += ltc2497.o
obj-$(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
index 000000000000..0278510ec346
--- /dev/null
+++ b/drivers/iio/adc/max1241.c
@@ -0,0 +1,206 @@
+// 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/regulator/consumer.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+
+#define MAX1241_VAL_MASK 0xFFF
+#define MAX1241_SHDN_DELAY_USEC 4
+
+enum max1241_id {
+ max1241,
+};
+
+struct max1241 {
+ struct spi_device *spi;
+ struct mutex lock;
+ struct regulator *reg;
+ struct gpio_desc *shdn;
+
+ __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),
+ .scan_index = 0,
+ .scan_type = {
+ .sign = 'u',
+ .realbits = 12,
+ .storagebits = 16,
+ },
+ },
+};
+
+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->shdn) {
+ gpiod_set_value(adc->shdn, 0);
+ udelay(MAX1241_SHDN_DELAY_USEC);
+ }
+
+ ret = max1241_read(adc);
+
+ if (adc->shdn)
+ gpiod_set_value(adc->shdn, 1);
+
+ 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->reg);
+
+ 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_reg_action(void *data)
+{
+ struct max1241 *adc = data;
+ int err;
+
+ err = regulator_disable(adc->reg);
+ if (err)
+ dev_err(&adc->spi->dev, "could not disable reference regulator.\n");
+}
+
+static int max1241_probe(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev;
+ struct max1241 *adc;
+ int ret = 0;
+
+ indio_dev = devm_iio_device_alloc(&spi->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->reg = devm_regulator_get(&spi->dev, "vref");
+ if (IS_ERR(adc->reg)) {
+ dev_err(&spi->dev, "failed to get vref regulator\n");
+ return PTR_ERR(adc->reg);
+ }
+
+ ret = regulator_enable(adc->reg);
+ if (ret)
+ return ret;
+
+ ret = devm_add_action_or_reset(&spi->dev, max1241_disable_reg_action,
+ adc);
+ if (ret) {
+ dev_err(&spi->dev, "could not set up regulator cleanup action!\n");
+ return ret;
+ }
+
+ adc->shdn = devm_gpiod_get_optional(&spi->dev, "shdn", GPIOD_OUT_HIGH);
+
+ if (IS_ERR(adc->shdn))
+ return PTR_ERR(adc->shdn);
+
+ if (!adc->shdn)
+ dev_dbg(&spi->dev, "no shdn pin passed, low-power mode disabled");
+ else
+ dev_dbg(&spi->dev, "shdn pin passed, low-power mode enabled");
+
+ indio_dev->name = spi_get_device_id(spi)->name;
+ indio_dev->dev.parent = &spi->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(&spi->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");
--
2.25.1