[PATCH v3 2/2] iio: adc: add MAX40080 current-sense amplifier driver

[Stefan Popa <stefan.popa@analog.com>]

The MAX40080 is a bidirectional current-sense amplifier with an
integrated 12-bit ADC and an I2C/SMBus interface. It measures the
voltage across an external shunt resistor and the input bus voltage,
storing the results in an internal FIFO.

No existing IIO driver covers this device or a register-compatible part.
The closest relatives target different silicon with incompatible register
maps and feature sets: max9611 is a unidirectional high-side sensor with a
die-temperature channel and MUX-selected gain and no FIFO/PEC, while
max34408 is an 8-bit multi-channel current monitor. The MAX40080 has a
device-specific register map with bidirectional 13-bit current, a 64-entry
FIFO, PEC, a single-measurement mode triggered by an SMBus Quick Command,
and two selectable input ranges, so it warrants its own driver.

Add a direct-mode IIO driver exposing the current and voltage channels
with raw and scale attributes, a configurable oversampling (digital
averaging) ratio, and PEC-protected register access. The two selectable
current-sense ranges are exposed through scale/scale_available; the
current scale is derived from the shunt-resistor-micro-ohms device-tree
property.

Link: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX40080.pdf

Co-developed-by: Ciprian Hegbeli <ciprian.hegbeli@analog.com>
Signed-off-by: Ciprian Hegbeli <ciprian.hegbeli@analog.com>
Signed-off-by: Stefan Popa <stefan.popa@analog.com>
---
 MAINTAINERS                |   9 +
 drivers/iio/adc/Kconfig    |  11 +
 drivers/iio/adc/Makefile   |   1 +
 drivers/iio/adc/max40080.c | 630 +++++++++++++++++++++++++++++++++++++
 4 files changed, 651 insertions(+)
 create mode 100644 drivers/iio/adc/max40080.c

diff --git a/MAINTAINERS b/MAINTAINERS
index e087673237636..f50c1e00e12bb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15513,6 +15513,15 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 F:	drivers/iio/temperature/max30208.c
 
+MAXIM MAX40080 CURRENT SENSE AMPLIFIER DRIVER
+M:	Ciprian Hegbeli <ciprian.hegbeli@analog.com>
+M:	Stefan Popa <stefan.popa@analog.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/adc/maxim,max40080.yaml
+F:	drivers/iio/adc/max40080.c
+
 MAXIM MAX7360 KEYPAD LED MFD DRIVER
 M:	Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
 S:	Maintained
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 58da8255525e4..b651c57bbc3f5 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1041,6 +1041,17 @@ config MAX34408
 	  To compile this driver as a module, choose M here: the module will be
 	  called max34408.
 
+config MAX40080
+	tristate "Analog Devices MAX40080 Current Sense Amplifier"
+	depends on I2C
+	help
+	  Say yes here to build support for the Analog Devices MAX40080
+	  bidirectional current-sense amplifier with a 12-bit ADC and an I2C
+	  interface.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max40080.
+
 config MAX77541_ADC
 	tristate "Analog Devices MAX77541 ADC driver"
 	depends on MFD_MAX77541
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 7cc8f9a12f763..e1953353c68a4 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -91,6 +91,7 @@ obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MAX14001) += max14001.o
 obj-$(CONFIG_MAX34408) += max34408.o
+obj-$(CONFIG_MAX40080) += max40080.o
 obj-$(CONFIG_MAX77541_ADC) += max77541-adc.o
 obj-$(CONFIG_MAX9611) += max9611.o
 obj-$(CONFIG_MCP320X) += mcp320x.o
diff --git a/drivers/iio/adc/max40080.c b/drivers/iio/adc/max40080.c
new file mode 100644
index 0000000000000..a0c1144cfda7c
--- /dev/null
+++ b/drivers/iio/adc/max40080.c
@@ -0,0 +1,630 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * MAX40080 Digital Current-Sense Amplifier driver
+ *
+ * Copyright 2026 Analog Devices, Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/cleanup.h>
+#include <linux/i2c.h>
+#include <linux/iopoll.h>
+#include <linux/math64.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/pm.h>
+#include <linux/property.h>
+#include <linux/time.h>
+#include <linux/types.h>
+#include <linux/unaligned.h>
+#include <linux/units.h>
+
+#include <linux/iio/iio.h>
+
+#define MAX40080_REG_CFG		0x00
+#define MAX40080_CFG_MODE_MSK		GENMASK(2, 0)
+#define MAX40080_CFG_PEC_EN_MSK		BIT(5)
+#define MAX40080_CFG_RANGE_MSK		BIT(6)
+#define MAX40080_CFG_FILTER_MSK		GENMASK(14, 12)
+
+#define MAX40080_REG_FIFO_CFG		0x0A
+#define MAX40080_FIFO_CFG_STORE_IV_MSK	GENMASK(1, 0)
+
+#define MAX40080_REG_IV			0x10
+/* Current is a 13-bit two's-complement value (magnitude + sign bit). */
+#define MAX40080_IV_I_MSK		GENMASK(12, 0)
+#define MAX40080_IV_I_SIGN_BIT		12
+#define MAX40080_IV_V_MAG_MSK		GENMASK(27, 16)
+#define MAX40080_IV_VALID_MSK		BIT(31)
+
+/* CFG.mode field values */
+#define MAX40080_CFG_MODE_STDBY		0x00
+#define MAX40080_CFG_MODE_SINGLE	0x02	/* one conversion per Quick Command */
+
+/* CFG.range field values */
+#define MAX40080_CFG_RANGE_50mV		0
+#define MAX40080_CFG_RANGE_10mV		1
+
+/* FIFO_CFG.store_iv field values */
+#define MAX40080_FIFO_CFG_STORE_I_V	0x02
+
+#define MAX40080_ADC_RES		4096
+#define MAX40080_INTER_VREF_mV		1250
+#define MAX40080_V_BUFF_GAIN		30
+#define MAX40080_CSA_50mV_GAIN		25
+#define MAX40080_CSA_10mV_GAIN		125
+
+/*
+ * The RANGE field (CFG bit 6) selects one of two current-sense full-scale
+ * ranges: +/-50 mV (gain 25 V/V) or +/-10 mV (gain 125 V/V).
+ */
+static const int max40080_csa_gain[] = {
+	[MAX40080_CFG_RANGE_50mV] = MAX40080_CSA_50mV_GAIN,
+	[MAX40080_CFG_RANGE_10mV] = MAX40080_CSA_10mV_GAIN,
+};
+
+struct max40080_state {
+	struct i2c_client *client;
+	/* Serializes read-modify-write access to the CFG register. */
+	struct mutex lock;
+	u32 shunt_resistor_uohm;
+	/*
+	 * Cached configuration, also used to restore the device on resume after
+	 * a suspend that may have cut its power: the selected RANGE index and
+	 * the oversampling ratio.
+	 */
+	unsigned int range;
+	int oversampling_ratio;
+	/*
+	 * Precomputed current scale (mA per code) for each RANGE setting, as
+	 * {integer, nano} pairs for IIO_VAL_INT_PLUS_NANO. The range is
+	 * selected by writing the corresponding scale.
+	 */
+	int current_scale[ARRAY_SIZE(max40080_csa_gain)][2];
+};
+
+static const int max40080_oversampling_avail[] = { 1, 8, 16, 32, 64, 128 };
+
+static int max40080_update_bits(struct max40080_state *st, u8 reg,
+				u16 mask, u16 val)
+{
+	int tmp;
+
+	guard(mutex)(&st->lock);
+
+	tmp = i2c_smbus_read_word_data(st->client, reg);
+	if (tmp < 0)
+		return tmp;
+
+	tmp = (tmp & ~mask) | (val & mask);
+
+	return i2c_smbus_write_word_data(st->client, reg, tmp);
+}
+
+/*
+ * In single-measurement mode the device sits idle until it receives an SMBus
+ * Quick Command, then performs exactly one current and one voltage conversion
+ * and returns to idle. Triggering on demand this way (rather than running the
+ * FIFO continuously in active mode) means each read returns a fresh, coherent
+ * current/voltage pair instead of the oldest queued FIFO entry.
+ */
+static int max40080_trigger_measurement(struct max40080_state *st)
+{
+	struct i2c_client *client = st->client;
+
+	return i2c_smbus_xfer(client->adapter, client->addr,
+			      client->flags, I2C_SMBUS_WRITE, 0,
+			      I2C_SMBUS_QUICK, NULL);
+}
+
+/*
+ * A single measurement holds the matched current/voltage pair in one 32-bit
+ * word (MAX40080_REG_IV). Reading all four bytes in one transaction returns
+ * both from the same conversion; reading the separate current (0x0C) and
+ * voltage (0x0E) registers would decorrelate the two channels.
+ *
+ * Unlike the word accesses used elsewhere, this is a plain I2C block read: the
+ * SMBus layer does not append or verify a PEC byte for it even when PEC is
+ * otherwise enabled for the device, so this transfer is not PEC protected.
+ */
+static int max40080_read_iv_once(struct max40080_state *st, u32 *iv)
+{
+	u8 buf[4];
+	int ret;
+
+	ret = i2c_smbus_read_i2c_block_data(st->client, MAX40080_REG_IV,
+					    sizeof(buf), buf);
+	if (ret < 0)
+		return ret;
+	if (ret != sizeof(buf))
+		return -EIO;
+
+	*iv = get_unaligned_le32(buf);
+
+	return 0;
+}
+
+static int max40080_read_iv(struct max40080_state *st, u32 *iv)
+{
+	int ret, io_ret;
+
+	guard(mutex)(&st->lock);
+
+	ret = max40080_trigger_measurement(st);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Wait for the conversion to complete by polling the FIFO valid bit
+	 * (or bail out on an I2C error). Polling the device's own status makes
+	 * this independent of the actual conversion time, which varies with the
+	 * oversampling ratio and the bus speed. The timeout is only a safety
+	 * ceiling: the worst case is the maximum 128x averaging on both the
+	 * current and voltage channels at the slowest 15 ksps base rate plus the
+	 * inter-channel switching time, i.e. roughly 20 ms; 50 ms leaves ample
+	 * margin.
+	 */
+	ret = read_poll_timeout(max40080_read_iv_once, io_ret,
+				io_ret || (*iv & MAX40080_IV_VALID_MSK),
+				1 * USEC_PER_MSEC, 50 * USEC_PER_MSEC,
+				false, st, iv);
+	if (ret)
+		return ret;
+
+	return io_ret;
+}
+
+static int max40080_get_current(struct max40080_state *st, int *val)
+{
+	u32 iv;
+	int ret;
+
+	ret = max40080_read_iv(st, &iv);
+	if (ret)
+		return ret;
+
+	*val = sign_extend32(FIELD_GET(MAX40080_IV_I_MSK, iv),
+			     MAX40080_IV_I_SIGN_BIT);
+
+	return 0;
+}
+
+static int max40080_get_voltage(struct max40080_state *st, int *val)
+{
+	u32 iv;
+	int ret;
+
+	ret = max40080_read_iv(st, &iv);
+	if (ret)
+		return ret;
+
+	*val = FIELD_GET(MAX40080_IV_V_MAG_MSK, iv);
+
+	return 0;
+}
+
+static int max40080_set_range(struct max40080_state *st, unsigned int range)
+{
+	int ret;
+
+	ret = max40080_update_bits(st, MAX40080_REG_CFG, MAX40080_CFG_RANGE_MSK,
+				   FIELD_PREP(MAX40080_CFG_RANGE_MSK, range));
+	if (ret)
+		return ret;
+
+	st->range = range;
+
+	return 0;
+}
+
+/*
+ * Precompute the current scale (mA per code) for each RANGE setting as
+ * {integer, nano} pairs. The shunt drop for a full-scale code is
+ *   Vref[mV] / (ADC_RES * gain)
+ * and current = Vshunt / Rshunt, so with Rshunt in micro-ohms the scale in
+ * mA/code is
+ *   Vref[mV] * NANO * MICRO / (ADC_RES * gain * Rshunt[uohm])
+ * expressed as an integer part plus a nano fractional part.
+ */
+static void max40080_calc_current_scale(struct max40080_state *st)
+{
+	unsigned int i;
+	u32 rem;
+	u64 tmp;
+
+	for (i = 0; i < ARRAY_SIZE(max40080_csa_gain); i++) {
+		tmp = (u64)MAX40080_INTER_VREF_mV * NANO * MICRO;
+		tmp = div64_u64(tmp, (u64)MAX40080_ADC_RES * max40080_csa_gain[i] *
+				st->shunt_resistor_uohm);
+		st->current_scale[i][0] = div_u64_rem(tmp, NANO, &rem);
+		st->current_scale[i][1] = rem;
+	}
+}
+
+/*
+ * The FILTER field selects digital averaging of N consecutive conversions
+ * (no averaging, 8, 16, 32, 64 or 128), which maps directly to the IIO
+ * oversampling ratio. Averaging reduces the effective output data rate by the
+ * same factor; the conversion rate itself is set by the separate ADC_RATE
+ * field.
+ */
+static int max40080_get_oversampling_ratio(struct max40080_state *st, int *val)
+{
+	u8 filter;
+	int tmp;
+
+	tmp = i2c_smbus_read_word_data(st->client, MAX40080_REG_CFG);
+	if (tmp < 0)
+		return tmp;
+
+	filter = FIELD_GET(MAX40080_CFG_FILTER_MSK, tmp);
+	if (filter >= ARRAY_SIZE(max40080_oversampling_avail))
+		return -EIO;
+
+	*val = max40080_oversampling_avail[filter];
+
+	return 0;
+}
+
+/*
+ * max40080_oversampling_avail[] is ordered so that its index is the FILTER
+ * field value (index 0 = no averaging, index 1 = 8x, ...). Return that index
+ * for an exact match, or -EINVAL for a value that is not on the list.
+ */
+static int max40080_oversampling_to_filter(int val)
+{
+	for (int i = 0; i < ARRAY_SIZE(max40080_oversampling_avail); i++) {
+		if (max40080_oversampling_avail[i] == val)
+			return i;
+	}
+
+	return -EINVAL;
+}
+
+static int max40080_set_oversampling_ratio(struct max40080_state *st, int val)
+{
+	int filter;
+	int ret;
+
+	filter = max40080_oversampling_to_filter(val);
+	if (filter < 0)
+		return filter;
+
+	ret = max40080_update_bits(st, MAX40080_REG_CFG, MAX40080_CFG_FILTER_MSK,
+				   FIELD_PREP(MAX40080_CFG_FILTER_MSK, filter));
+	if (ret)
+		return ret;
+
+	st->oversampling_ratio = val;
+
+	return 0;
+}
+
+static int max40080_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max40080_state *st = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		switch (chan->type) {
+		case IIO_CURRENT:
+			ret = max40080_get_current(st, val);
+			if (ret)
+				return ret;
+			break;
+		case IIO_VOLTAGE:
+			ret = max40080_get_voltage(st, val);
+			if (ret)
+				return ret;
+			break;
+		default:
+			return -EINVAL;
+		}
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		/*
+		 * The selectable current-sense range is exposed through
+		 * scale: each RANGE setting has its own precomputed
+		 * mA-per-code value. Userspace picks the range by writing
+		 * the matching scale.
+		 */
+		switch (chan->type) {
+		case IIO_CURRENT:
+			*val = st->current_scale[st->range][0];
+			*val2 = st->current_scale[st->range][1];
+			return IIO_VAL_INT_PLUS_NANO;
+		case IIO_VOLTAGE:
+			/* voltage[mV] = raw * Vref[mV] * buffer_gain / ADC_RES */
+			*val = MAX40080_INTER_VREF_mV * MAX40080_V_BUFF_GAIN;
+			*val2 = MAX40080_ADC_RES;
+			return IIO_VAL_FRACTIONAL;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		ret = max40080_get_oversampling_ratio(st, val);
+		if (ret)
+			return ret;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int max40080_write_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int val, int val2, long mask)
+{
+	struct max40080_state *st = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		/* Only the current channel has a selectable range/scale. */
+		if (chan->type != IIO_CURRENT)
+			return -EINVAL;
+
+		for (unsigned int i = 0; i < ARRAY_SIZE(max40080_csa_gain); i++) {
+			if (val == st->current_scale[i][0] &&
+			    val2 == st->current_scale[i][1])
+				return max40080_set_range(st, i);
+		}
+
+		return -EINVAL;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		return max40080_set_oversampling_ratio(st, val);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int max40080_write_raw_get_fmt(struct iio_dev *indio_dev,
+				      struct iio_chan_spec const *chan,
+				      long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		return IIO_VAL_INT_PLUS_NANO;
+	default:
+		return IIO_VAL_INT;
+	}
+}
+
+static int max40080_read_avail(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan,
+			       const int **vals, int *type, int *length,
+			       long info)
+{
+	struct max40080_state *st = iio_priv(indio_dev);
+
+	switch (info) {
+	case IIO_CHAN_INFO_SCALE:
+		if (chan->type != IIO_CURRENT)
+			return -EINVAL;
+
+		*vals = (const int *)st->current_scale;
+		*length = ARRAY_SIZE(max40080_csa_gain) * 2;
+		*type = IIO_VAL_INT_PLUS_NANO;
+
+		return IIO_AVAIL_LIST;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		*vals = max40080_oversampling_avail;
+		*length = ARRAY_SIZE(max40080_oversampling_avail);
+		*type = IIO_VAL_INT;
+
+		return IIO_AVAIL_LIST;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int max40080_reg_access(struct iio_dev *indio_dev,
+			       unsigned int reg,
+			       unsigned int write_val,
+			       unsigned int *read_val)
+{
+	struct max40080_state *st = iio_priv(indio_dev);
+	int val;
+
+	if (!read_val)
+		return i2c_smbus_write_word_data(st->client, reg, write_val);
+
+	val = i2c_smbus_read_word_data(st->client, reg);
+	if (val < 0)
+		return val;
+
+	*read_val = val;
+
+	return 0;
+}
+
+static const struct iio_info max40080_info = {
+	.read_raw = max40080_read_raw,
+	.write_raw = max40080_write_raw,
+	.write_raw_get_fmt = max40080_write_raw_get_fmt,
+	.read_avail = max40080_read_avail,
+	.debugfs_reg_access = &max40080_reg_access,
+};
+
+static const struct iio_chan_spec max40080_channels[] = {
+	{
+		.type = IIO_CURRENT,
+		.indexed = 1,
+		.channel = 0,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+		.info_mask_separate_available = BIT(IIO_CHAN_INFO_SCALE),
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+		.info_mask_shared_by_all_available =
+			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+	},
+	{
+		.type = IIO_VOLTAGE,
+		.indexed = 1,
+		.channel = 0,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+		.info_mask_shared_by_all_available =
+			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+	},
+};
+
+/*
+ * Configure (or, after a suspend that cut power, restore) the device from the
+ * cached state. The device powers up in standby with PEC enabled (CFG POR =
+ * 0x0060), so PEC is kept enabled throughout.
+ */
+static int max40080_init(struct max40080_state *st)
+{
+	u16 fifo_cfg, cfg;
+	int filter;
+	int ret;
+
+	filter = max40080_oversampling_to_filter(st->oversampling_ratio);
+	if (filter < 0)
+		return filter;
+
+	/*
+	 * Put the device in standby before (re)configuring the FIFO: the FIFO
+	 * configuration register can only be written while the device is not
+	 * converting.
+	 */
+	cfg = FIELD_PREP(MAX40080_CFG_MODE_MSK, MAX40080_CFG_MODE_STDBY) |
+	      FIELD_PREP(MAX40080_CFG_PEC_EN_MSK, 1);
+	ret = i2c_smbus_write_word_data(st->client, MAX40080_REG_CFG, cfg);
+	if (ret)
+		return ret;
+
+	/* Store a matched current+voltage pair per conversion. */
+	fifo_cfg = FIELD_PREP(MAX40080_FIFO_CFG_STORE_IV_MSK, MAX40080_FIFO_CFG_STORE_I_V);
+	ret = i2c_smbus_write_word_data(st->client, MAX40080_REG_FIFO_CFG, fifo_cfg);
+	if (ret)
+		return ret;
+
+	/*
+	 * Use single-measurement mode: the device stays idle and converts once
+	 * per SMBus Quick Command (see max40080_trigger_measurement()), so each
+	 * read returns a fresh sample rather than a queued FIFO entry.
+	 */
+	cfg = FIELD_PREP(MAX40080_CFG_MODE_MSK, MAX40080_CFG_MODE_SINGLE) |
+	      FIELD_PREP(MAX40080_CFG_PEC_EN_MSK, 1) |
+	      FIELD_PREP(MAX40080_CFG_RANGE_MSK, st->range) |
+	      FIELD_PREP(MAX40080_CFG_FILTER_MSK, filter);
+
+	return i2c_smbus_write_word_data(st->client, MAX40080_REG_CFG, cfg);
+}
+
+static int max40080_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct max40080_state *st;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	/*
+	 * The device powers up with PEC enabled (CFG POR = 0x0060) and rejects
+	 * unprotected transactions, so PEC support is mandatory, along with word
+	 * access, the I2C block read used for the current/voltage pair, and the
+	 * Quick Command used to trigger a conversion.
+	 */
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_WORD_DATA |
+				     I2C_FUNC_SMBUS_I2C_BLOCK |
+				     I2C_FUNC_SMBUS_QUICK |
+				     I2C_FUNC_SMBUS_PEC))
+		return -EOPNOTSUPP;
+
+	client->flags |= I2C_CLIENT_PEC;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, indio_dev);
+
+	st = iio_priv(indio_dev);
+	st->client = client;
+
+	ret = devm_mutex_init(dev, &st->lock);
+	if (ret)
+		return ret;
+
+	if (device_property_present(dev, "shunt-resistor-micro-ohms")) {
+		ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms",
+					       &st->shunt_resistor_uohm);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "can't read shunt-resistor-micro-ohms\n");
+		if (!st->shunt_resistor_uohm)
+			return dev_err_probe(dev, -EINVAL,
+					     "shunt-resistor-micro-ohms must be non-zero\n");
+	} else {
+		st->shunt_resistor_uohm = 1 * MICRO;
+	}
+
+	max40080_calc_current_scale(st);
+
+	/* Defaults: 50 mV range (index 0), no averaging. */
+	st->range = 0;
+	st->oversampling_ratio = 1;
+
+	indio_dev->name = "max40080";
+	indio_dev->info = &max40080_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = max40080_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max40080_channels);
+
+	ret = max40080_init(st);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static int max40080_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct max40080_state *st = iio_priv(indio_dev);
+
+	/*
+	 * A suspend may have cut power to the device, resetting it to its
+	 * power-on defaults. Reprogram it from the cached configuration.
+	 */
+	guard(mutex)(&st->lock);
+
+	return max40080_init(st);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(max40080_pm_ops, NULL, max40080_resume);
+
+static const struct i2c_device_id max40080_i2c_ids[] = {
+	{ .name = "max40080" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max40080_i2c_ids);
+
+static const struct of_device_id max40080_of_match[] = {
+	{ .compatible = "maxim,max40080" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max40080_of_match);
+
+static struct i2c_driver max40080_driver = {
+	.driver = {
+		.name = "max40080",
+		.of_match_table = max40080_of_match,
+		.pm = pm_sleep_ptr(&max40080_pm_ops),
+	},
+	.probe = max40080_probe,
+	.id_table = max40080_i2c_ids,
+};
+module_i2c_driver(max40080_driver);
+
+MODULE_AUTHOR("Ciprian Hegbeli <ciprian.hegbeli@analog.com>");
+MODULE_AUTHOR("Stefan Popa <stefan.popa@analog.com>");
+MODULE_DESCRIPTION("Analog Devices MAX40080 current-sense amplifier driver");
+MODULE_LICENSE("GPL");
-- 
2.53.0