iio: adc: Add basic support for MAX14001

The MAX14001/MAX14002 are configurable, isolated 10-bit ADCs for
multi-range binary inputs. Besides the ADC readings, the MAX14001/MAX14002
offers more features, like a binary comparator, a filtered reading that
can provide the average of the last 2, 4, or 8 ADC readings, and an inrush
comparator that triggers the inrush current. There is also a fault feature
that can diagnose seven possible fault conditions. And an option to select
an external or internal ADC voltage reference.

Add basic support for MAX14001/MAX14002 with the following features:
- Raw ADC reading.
- Filtered ADC average reading with the default configuration.

Signed-off-by: Marilene Andrade Garcia <[email protected]>

Author: MarileneGarcia

MAINTAINERS

@@ -13128,6 +13128,7 @@ L:	[email protected]
 S:	Maintained
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
+F:	drivers/iio/adc/max14001.c
 
 MAXIM MAX17040 FAMILY FUEL GAUGE DRIVERS
 R:	Iskren Chernev <[email protected]>

drivers/iio/adc/Kconfig

@@ -1126,6 +1126,16 @@ config MAX1363
 	  To compile this driver as a module, choose M here: the module will be
 	  called max1363.
 
+config MAX14001
+	tristate "Analog Devices MAX14001/MAX14002 ADCs driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices MAX14001/MAX14002
+	  Configurable, Isolated 10-bit ADCs for Multi-Range Binary Inputs.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max14001.
+
 config MAX77541_ADC
 	tristate "Analog Devices MAX77541 ADC driver"
 	depends on MFD_MAX77541

drivers/iio/adc/Makefile

@@ -156,6 +156,7 @@ obj-$(CONFIG_MAX11205) += max11205.o
 obj-$(CONFIG_MAX11410) += max11410.o
 obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
+obj-$(CONFIG_MAX14001) += max14001.o
 obj-$(CONFIG_MAX77541_ADC) += max77541-adc.o
 obj-$(CONFIG_MAX9611) += max9611.o
 obj-$(CONFIG_MCP320X) += mcp320x.o

drivers/iio/adc/max14001.c

@@ -0,0 +1,213 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MAX14001/MAX14002 SPI ADC driver
+ *
+ * Copyright (c) 2025 Marilene Andrade Garcia <[email protected]>
+ *
+ * Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf
+ */
+
+#include <asm/unaligned.h>
+#include <linux/bitfield.h>
+#include <linux/bitrev.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/iio/iio.h>
+#include <linux/regulator/consumer.h>
+
+/* MAX14001 registers definition */
+#define MAX14001_REG_ADC				0x00
+#define MAX14001_REG_FADC				0x01
+#define MAX14001_REG_FLAGS				0x02
+#define MAX14001_REG_FLTEN				0x03
+#define MAX14001_REG_THL				0x04
+#define MAX14001_REG_THU				0x05
+#define MAX14001_REG_INRR				0x06
+#define MAX14001_REG_INRT				0x07
+#define MAX14001_REG_INRP				0x08
+#define MAX14001_REG_CFG				0x09
+#define MAX14001_REG_ENBL				0x0A
+#define MAX14001_REG_ACT				0x0B
+#define MAX14001_REG_WEN				0x0C
+
+/* MAX14001 CONTROL values*/
+#define MAX14001_REG_WRITE				0x1
+#define MAX14001_REG_READ				0x0
+
+/* MAX14001 MASKS */
+#define MAX14001_MASK_ADDR				GENMASK(15, 11)
+#define MAX14001_MASK_WR				BIT(10)
+#define MAX14001_MASK_DATA				GENMASK(9, 0)
+
+enum max14001_chip_model {
+	max14001,
+	max14002,
+};
+
+struct max14001_chip_info {
+	const char *name;
+};
+
+struct max14001_state {
+	const struct max14001_chip_info *chip_info;
+	struct spi_device *spi;
+	int vref_mv;
+
+	__be16 rx_buffer __aligned(IIO_DMA_MINALIGN);
+	__be16 tx_buffer;
+};
+
+static struct max14001_chip_info max14001_chip_info_tbl[] = {
+	[max14001] = {
+		.name = "max14001",
+	},
+	[max14002] = {
+		.name = "max14002",
+	},
+};
+
+static int max14001_spi_read(struct max14001_state *st, u16 reg, int *val)
+{
+	struct spi_transfer xfer[] = {
+		{
+			.tx_buf = &st->tx_buffer,
+			.len = sizeof(st->tx_buffer),
+			.cs_change = 1,
+		},
+		{
+			.rx_buf = &st->rx_buffer,
+			.len = sizeof(st->rx_buffer),
+		},
+	};
+	int ret;
+
+	st->tx_buffer = FIELD_PREP(MAX14001_MASK_ADDR, reg) |
+			FIELD_PREP(MAX14001_MASK_WR, MAX14001_REG_READ);
+	st->tx_buffer = bitrev16(st->tx_buffer);
+
+	ret = spi_sync_transfer(st->spi, xfer, ARRAY_SIZE(xfer));
+	if (ret < 0)
+		return ret;
+
+	st->rx_buffer = bitrev16(be16_to_cpu(st->rx_buffer));
+	*val = FIELD_GET(MAX14001_MASK_DATA, st->rx_buffer);
+
+	return 0;
+}
+
+static int max14001_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max14001_state *st = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = max14001_spi_read(st, MAX14001_REG_ADC, val);
+		if (ret < 0)
+			return ret;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_AVERAGE_RAW:
+		ret = max14001_spi_read(st, MAX14001_REG_FADC, val);
+		if (ret < 0)
+			return ret;
+
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		*val = st->vref_mv;
+		*val2 = 10;
+
+		return IIO_VAL_FRACTIONAL_LOG2;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info max14001_info = {
+	.read_raw = max14001_read_raw,
+};
+
+static const struct iio_chan_spec max14001_channel[] = {
+	{
+		.type = IIO_VOLTAGE,
+		.indexed = 1,
+		.channel = 0,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_AVERAGE_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+	}
+};
+
+static int max14001_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct max14001_state *st;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->spi = spi;
+	st->chip_info = spi_get_device_match_data(spi);
+	if (!st->chip_info)
+		return dev_err_probe(dev, -ENODEV, "Failed to get match data\n");
+
+	indio_dev->name = st->chip_info->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &max14001_info;
+	indio_dev->channels = max14001_channel;
+	indio_dev->num_channels = ARRAY_SIZE(max14001_channel);
+
+	ret = devm_regulator_get_enable(dev, "vdd");
+	if (ret)
+		return dev_err_probe(dev, ret,
+			"Failed to enable specified Vdd supply\n");
+
+	ret = devm_regulator_get_enable(dev, "vddl");
+	if (ret)
+		return dev_err_probe(dev, ret,
+			"Failed to enable specified Vddl supply\n");
+
+	ret = devm_regulator_get_enable_read_voltage(dev, "vrefin");
+	if (ret < 0)
+		st->vref_mv = 1250000 / 1000;
+	else
+		st->vref_mv = ret / 1000;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct spi_device_id max14001_id_table[] = {
+	{ "max14001", (kernel_ulong_t)&max14001_chip_info_tbl[max14001] },
+	{ "max14002", (kernel_ulong_t)&max14001_chip_info_tbl[max14002] },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, max14001_id_table);
+
+static const struct of_device_id max14001_of_match[] = {
+	{ .compatible = "adi,max14001",
+	  .data = &max14001_chip_info_tbl[max14001], },
+	{ .compatible = "adi,max14002",
+	  .data = &max14001_chip_info_tbl[max14002], },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max14001_of_match);
+
+static struct spi_driver max14001_driver = {
+	.driver = {
+		.name = "max14001",
+		.of_match_table = max14001_of_match,
+	},
+	.probe = max14001_probe,
+	.id_table = max14001_id_table,
+};
+module_spi_driver(max14001_driver);
+
+MODULE_AUTHOR("Marilene Andrade Garcia <[email protected]>");
+MODULE_DESCRIPTION("Analog Devices MAX14001/MAX14002 ADCs driver");
+MODULE_LICENSE("GPL");