[PATCH v4 2/2] iio: adc: add support for Nuvoton NCT7201

[Eason Yang <j2anfernee@gmail.com>]

Add Nuvoton NCT7201/NCT7202 system voltage monitor 12-bit ADC driver

NCT7201/NCT7202 supports up to 12 analog voltage monitor inputs and up to
4 SMBus addresses by ADDR pin. Meanwhile, ALERT# hardware event pins for
independent alarm signals, and the all threshold values could be set for
system protection without any timing delay. It also supports reset input
RSTIN# to recover system from a fault condition.

Currently, only single-edge mode conversion and threshold events support.

Signed-off-by: Eason Yang <j2anfernee@gmail.com>
---
 MAINTAINERS               |   1 +
 drivers/iio/adc/Kconfig   |  11 +
 drivers/iio/adc/Makefile  |   1 +
 drivers/iio/adc/nct7201.c | 487 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 500 insertions(+)
 create mode 100644 drivers/iio/adc/nct7201.c

diff --git a/MAINTAINERS b/MAINTAINERS
index fdc4aa5c7eff..389cbbdae1a7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2838,6 +2838,7 @@ F:	arch/arm/mach-npcm/
 F:	arch/arm64/boot/dts/nuvoton/
 F:	drivers/*/*/*npcm*
 F:	drivers/*/*npcm*
+F:	drivers/iio/adc/nct7201.c
 F:	drivers/rtc/rtc-nct3018y.c
 F:	include/dt-bindings/clock/nuvoton,npcm7xx-clock.h
 F:	include/dt-bindings/clock/nuvoton,npcm845-clk.h
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 849c90203071..d97eccb1c685 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1048,6 +1048,17 @@ config NAU7802
 	  To compile this driver as a module, choose M here: the
 	  module will be called nau7802.
 
+config NCT7201
+        tristate "Nuvoton NCT7201 and NCT7202 Power Monitor"
+        depends on I2C
+        select REGMAP_I2C
+        help
+          Say yes here to build support for Nuvoton NCT7201 and NCT7202
+          Voltage Monitor.
+
+          This driver can also be built as a module. If so, the module
+          will be called nct7201.
+
 config NPCM_ADC
 	tristate "Nuvoton NPCM ADC driver"
 	depends on ARCH_NPCM || COMPILE_TEST
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index ee19afba62b7..0108472e141c 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -94,6 +94,7 @@ obj-$(CONFIG_MESON_SARADC) += meson_saradc.o
 obj-$(CONFIG_MP2629_ADC) += mp2629_adc.o
 obj-$(CONFIG_MXS_LRADC_ADC) += mxs-lradc-adc.o
 obj-$(CONFIG_NAU7802) += nau7802.o
+obj-$(CONFIG_NCT7201) += nct7201.o
 obj-$(CONFIG_NPCM_ADC) += npcm_adc.o
 obj-$(CONFIG_PAC1921) += pac1921.o
 obj-$(CONFIG_PAC1934) += pac1934.o
diff --git a/drivers/iio/adc/nct7201.c b/drivers/iio/adc/nct7201.c
new file mode 100644
index 000000000000..c5d1540bcc00
--- /dev/null
+++ b/drivers/iio/adc/nct7201.c
@@ -0,0 +1,487 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for Nuvoton nct7201 and nct7202 power monitor chips.
+ *
+ * Copyright (c) 2024-2025 Nuvoton Technology corporation.
+ */
+
+#include <linux/array_size.h>
+#include <linux/bits.h>
+#include <linux/cleanup.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+#include <linux/unaligned.h>
+
+#include <linux/iio/events.h>
+#include <linux/iio/iio.h>
+
+#define NCT7201_VIN_MAX				12
+#define NCT7201_IN_SCALING				4995
+#define NCT7201_IN_SCALING_FACTOR			10000
+
+#define NCT7201_REG_INTERRUPT_STATUS_1			0x0C
+#define NCT7201_REG_INTERRUPT_STATUS_2			0x0D
+#define NCT7201_REG_VOLT_LOW_BYTE			0x0F
+#define NCT7201_REG_CONFIGURATION			0x10
+#define  NCT7201_BIT_CONFIGURATION_START		BIT(0)
+#define  NCT7201_BIT_CONFIGURATION_ALERT_MSK		BIT(1)
+#define  NCT7201_BIT_CONFIGURATION_CONV_RATE		BIT(2)
+#define  NCT7201_BIT_CONFIGURATION_RESET		BIT(7)
+
+#define NCT7201_REG_ADVANCED_CONFIGURATION		0x11
+#define  NCT7201_BIT_ADVANCED_CONF_MOD_ALERT		BIT(0)
+#define  NCT7201_BIT_ADVANCED_CONF_MOD_STS		BIT(1)
+#define  NCT7201_BIT_ADVANCED_CONF_FAULT_QUEUE		BIT(2)
+#define  NCT7201_BIT_ADVANCED_CONF_EN_DEEP_SHUTDOWN	BIT(4)
+#define  NCT7201_BIT_ADVANCED_CONF_EN_SMB_TIMEOUT	BIT(5)
+#define  NCT7201_BIT_ADVANCED_CONF_MOD_RSTIN		BIT(7)
+
+#define NCT7201_REG_CHANNEL_INPUT_MODE			0x12
+#define NCT7201_REG_CHANNEL_ENABLE_1			0x13
+#define  NCT7201_REG_CHANNEL_ENABLE_1_MASK		GENMASK(7, 0)
+#define NCT7201_REG_CHANNEL_ENABLE_2			0x14
+#define  NCT7201_REG_CHANNEL_ENABLE_2_MASK		GENMASK(3, 0)
+#define NCT7201_REG_INTERRUPT_MASK_1			0x15
+#define NCT7201_REG_INTERRUPT_MASK_2			0x16
+#define NCT7201_REG_BUSY_STATUS				0x1E
+#define  NCT7201_BIT_BUSY				BIT(0)
+#define  NCT7201_BIT_PWR_UP				BIT(1)
+#define NCT7201_REG_ONE_SHOT				0x1F
+#define NCT7201_REG_SMUS_ADDRESS			0xFC
+#define NCT7201_REG_VIN_MASK				GENMASK(15, 3)
+
+#define NCT7201_REG_VIN(i)				(i)
+#define NCT7201_REG_VIN_HIGH_LIMIT(i)			(0x20 + (i) * 2)
+#define NCT7201_REG_VIN_LOW_LIMIT(i)			(0x21 + (i) * 2)
+
+static const struct regmap_range nct7201_read_reg_range[] = {
+	regmap_reg_range(NCT7201_REG_INTERRUPT_STATUS_1, NCT7201_REG_BUSY_STATUS),
+	regmap_reg_range(NCT7201_REG_SMUS_ADDRESS, NCT7201_REG_SMUS_ADDRESS),
+};
+
+static const struct regmap_access_table nct7201_readable_regs_tbl = {
+	.yes_ranges = nct7201_read_reg_range,
+	.n_yes_ranges = ARRAY_SIZE(nct7201_read_reg_range),
+};
+
+static const struct regmap_range nct7201_write_reg_range[] = {
+	regmap_reg_range(NCT7201_REG_CONFIGURATION, NCT7201_REG_INTERRUPT_MASK_2),
+	regmap_reg_range(NCT7201_REG_ONE_SHOT, NCT7201_REG_ONE_SHOT),
+};
+
+static const struct regmap_access_table nct7201_writeable_regs_tbl = {
+	.yes_ranges = nct7201_write_reg_range,
+	.n_yes_ranges = ARRAY_SIZE(nct7201_write_reg_range),
+};
+
+static const struct regmap_range nct7201_read_vin_reg_range[] = {
+	regmap_reg_range(NCT7201_REG_VIN(0), NCT7201_REG_VIN(NCT7201_VIN_MAX - 1)),
+	regmap_reg_range(NCT7201_REG_VIN_HIGH_LIMIT(0),
+			 NCT7201_REG_VIN_LOW_LIMIT(NCT7201_VIN_MAX - 1)),
+};
+
+static const struct regmap_access_table nct7201_readable_vin_regs_tbl = {
+	.yes_ranges = nct7201_read_vin_reg_range,
+	.n_yes_ranges = ARRAY_SIZE(nct7201_read_vin_reg_range),
+};
+
+static const struct regmap_range nct7201_write_vin_reg_range[] = {
+	regmap_reg_range(NCT7201_REG_VIN_HIGH_LIMIT(0),
+			 NCT7201_REG_VIN_LOW_LIMIT(NCT7201_VIN_MAX - 1)),
+};
+
+static const struct regmap_access_table nct7201_writeable_vin_regs_tbl = {
+	.yes_ranges = nct7201_write_vin_reg_range,
+	.n_yes_ranges = ARRAY_SIZE(nct7201_write_vin_reg_range),
+};
+
+static const struct regmap_config nct7201_regmap8_config = {
+	.name = "vin-data-read-byte",
+	.reg_bits = 8,
+	.val_bits = 8,
+	.use_single_write = true,
+	.max_register = 0xff,
+	.rd_table = &nct7201_readable_regs_tbl,
+	.wr_table = &nct7201_writeable_regs_tbl,
+};
+
+static const struct regmap_config nct7201_regmap16_config = {
+	.name = "vin-data-read-word",
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 0xff,
+	.rd_table = &nct7201_readable_vin_regs_tbl,
+	.wr_table = &nct7201_writeable_vin_regs_tbl,
+};
+
+struct nct7201_chip_info {
+	struct i2c_client *client;
+	struct mutex access_lock;
+	struct regmap *regmap;
+	struct regmap *regmap16;
+	int num_vin_channels;
+	u16 vin_mask;
+};
+
+struct nct7201_adc_model_data {
+	const char *model_name;
+	const struct iio_chan_spec *channels;
+	const int num_channels;
+	int num_vin_channels;
+};
+
+static const struct iio_event_spec nct7201_events[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_RISING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE) |
+				 BIT(IIO_EV_INFO_ENABLE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE) |
+				 BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+#define NCT7201_VOLTAGE_CHANNEL(chan, addr)				\
+	{								\
+		.type = IIO_VOLTAGE,					\
+		.indexed = 1,						\
+		.channel = chan,					\
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+		.address = addr,					\
+		.event_spec = nct7201_events,				\
+		.num_event_specs = ARRAY_SIZE(nct7201_events),		\
+	}
+
+static const struct iio_chan_spec nct7201_channels[] = {
+	NCT7201_VOLTAGE_CHANNEL(1, 0),
+	NCT7201_VOLTAGE_CHANNEL(2, 1),
+	NCT7201_VOLTAGE_CHANNEL(3, 2),
+	NCT7201_VOLTAGE_CHANNEL(4, 3),
+	NCT7201_VOLTAGE_CHANNEL(5, 4),
+	NCT7201_VOLTAGE_CHANNEL(6, 5),
+	NCT7201_VOLTAGE_CHANNEL(7, 6),
+	NCT7201_VOLTAGE_CHANNEL(8, 7),
+};
+
+static const struct iio_chan_spec nct7202_channels[] = {
+	NCT7201_VOLTAGE_CHANNEL(1, 0),
+	NCT7201_VOLTAGE_CHANNEL(2, 1),
+	NCT7201_VOLTAGE_CHANNEL(3, 2),
+	NCT7201_VOLTAGE_CHANNEL(4, 3),
+	NCT7201_VOLTAGE_CHANNEL(5, 4),
+	NCT7201_VOLTAGE_CHANNEL(6, 5),
+	NCT7201_VOLTAGE_CHANNEL(7, 6),
+	NCT7201_VOLTAGE_CHANNEL(8, 7),
+	NCT7201_VOLTAGE_CHANNEL(9, 8),
+	NCT7201_VOLTAGE_CHANNEL(10, 9),
+	NCT7201_VOLTAGE_CHANNEL(11, 10),
+	NCT7201_VOLTAGE_CHANNEL(12, 11),
+};
+
+static int nct7201_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	u16 volt;
+	unsigned int value;
+	int err;
+	struct nct7201_chip_info *chip = iio_priv(indio_dev);
+
+	if (chan->type != IIO_VOLTAGE)
+		return -EOPNOTSUPP;
+
+	guard(mutex)(&chip->access_lock);
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		err = regmap_read(chip->regmap16, NCT7201_REG_VIN(chan->address), &value);
+		if (err < 0)
+			return err;
+		volt = value;
+		*val = FIELD_GET(NCT7201_REG_VIN_MASK, volt);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		/* From the datasheet, we have to multiply by 0.0004995 */
+		*val = 0;
+		*val2 = 499500;
+		return IIO_VAL_INT_PLUS_NANO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int nct7201_read_event_value(struct iio_dev *indio_dev,
+				    const struct iio_chan_spec *chan,
+				    enum iio_event_type type,
+				    enum iio_event_direction dir,
+				    enum iio_event_info info,
+				    int *val, int *val2)
+{
+	struct nct7201_chip_info *chip = iio_priv(indio_dev);
+	u16 volt;
+	unsigned int value;
+	int err;
+
+	if (chan->type != IIO_VOLTAGE)
+		return -EOPNOTSUPP;
+
+	if (info != IIO_EV_INFO_VALUE)
+		return -EINVAL;
+
+	if (dir == IIO_EV_DIR_FALLING) {
+		err = regmap_read(chip->regmap16, NCT7201_REG_VIN_LOW_LIMIT(chan->address),
+				  &value);
+		if (err < 0)
+			return err;
+		volt = value;
+	} else {
+		err = regmap_read(chip->regmap16, NCT7201_REG_VIN_HIGH_LIMIT(chan->address),
+				  &value);
+		if (err < 0)
+			return err;
+		volt = value;
+	}
+
+	*val = FIELD_GET(NCT7201_REG_VIN_MASK, volt);
+
+	return IIO_VAL_INT;
+}
+
+static int nct7201_write_event_value(struct iio_dev *indio_dev,
+				     const struct iio_chan_spec *chan,
+				     enum iio_event_type type,
+				     enum iio_event_direction dir,
+				     enum iio_event_info info,
+				     int val, int val2)
+{
+	struct nct7201_chip_info *chip = iio_priv(indio_dev);
+
+	if (chan->type != IIO_VOLTAGE)
+		return -EOPNOTSUPP;
+
+	if (info != IIO_EV_INFO_VALUE)
+		return -EOPNOTSUPP;
+
+	if (dir == IIO_EV_DIR_FALLING)
+		regmap_write(chip->regmap16, NCT7201_REG_VIN_LOW_LIMIT(chan->address),
+			     FIELD_PREP(NCT7201_REG_VIN_MASK, val));
+	else
+		regmap_write(chip->regmap16, NCT7201_REG_VIN_HIGH_LIMIT(chan->address),
+			     FIELD_PREP(NCT7201_REG_VIN_MASK, val));
+
+	return 0;
+}
+
+static int nct7201_read_event_config(struct iio_dev *indio_dev,
+				     const struct iio_chan_spec *chan,
+				     enum iio_event_type type,
+				     enum iio_event_direction dir)
+{
+	struct nct7201_chip_info *chip = iio_priv(indio_dev);
+
+	if (chan->type != IIO_VOLTAGE)
+		return -EOPNOTSUPP;
+
+	return !!(chip->vin_mask & BIT(chan->address));
+}
+
+static int nct7201_write_event_config(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan,
+				      enum iio_event_type type,
+				      enum iio_event_direction dir,
+				      bool state)
+{
+	struct nct7201_chip_info *chip = iio_priv(indio_dev);
+	unsigned int mask;
+
+	if (chan->type != IIO_VOLTAGE)
+		return -EOPNOTSUPP;
+
+	mask = BIT(chan->address);
+
+	if (!state && (chip->vin_mask & mask))
+		chip->vin_mask &= ~mask;
+	else if (state && !(chip->vin_mask & mask))
+		chip->vin_mask |= mask;
+
+	if (chip->num_vin_channels <= 8)
+		regmap_write(chip->regmap, NCT7201_REG_CHANNEL_ENABLE_1, chip->vin_mask);
+	else
+		regmap_bulk_write(chip->regmap, NCT7201_REG_CHANNEL_ENABLE_1,
+				  &chip->vin_mask, sizeof(chip->vin_mask));
+
+	return 0;
+}
+
+static const struct iio_info nct7201_info = {
+	.read_raw = nct7201_read_raw,
+	.read_event_config = nct7201_read_event_config,
+	.write_event_config = nct7201_write_event_config,
+	.read_event_value = nct7201_read_event_value,
+	.write_event_value = nct7201_write_event_value,
+};
+
+static const struct iio_info nct7201_info_no_irq = {
+	.read_raw = nct7201_read_raw,
+};
+
+static const struct nct7201_adc_model_data nct7201_model_data = {
+	.model_name = "nct7201",
+	.channels = nct7201_channels,
+	.num_channels = ARRAY_SIZE(nct7201_channels),
+	.num_vin_channels = 8,
+};
+
+static const struct nct7201_adc_model_data nct7202_model_data = {
+	.model_name = "nct7202",
+	.channels = nct7202_channels,
+	.num_channels = ARRAY_SIZE(nct7202_channels),
+	.num_vin_channels = 12,
+};
+
+static int nct7201_init_chip(struct nct7201_chip_info *chip)
+{
+	u8 data[2];
+	unsigned int value;
+	int err;
+
+	regmap_write(chip->regmap, NCT7201_REG_CONFIGURATION,
+		     NCT7201_BIT_CONFIGURATION_RESET);
+
+	/*
+	 * After about 25 msecs, the device should be ready and then
+	 * the Power Up bit will be set to 1. If not, wait for it.
+	 */
+	mdelay(25);
+	err = regmap_read(chip->regmap, NCT7201_REG_BUSY_STATUS, &value);
+	if (err < 0)
+		return err;
+	if (!(value & NCT7201_BIT_PWR_UP))
+		return dev_err_probe(&chip->client->dev, -EIO,
+				     "Failed to power up after reset\n");
+
+	/* Enable Channel */
+	if (chip->num_vin_channels <= 8) {
+		data[0] = NCT7201_REG_CHANNEL_ENABLE_1_MASK;
+		err = regmap_write(chip->regmap, NCT7201_REG_CHANNEL_ENABLE_1, data[0]);
+		if (err < 0)
+			return dev_err_probe(&chip->client->dev, -EIO,
+					     "Failed to write NCT7201_REG_CHANNEL_ENABLE_1\n");
+	} else {
+		data[0] = NCT7201_REG_CHANNEL_ENABLE_1_MASK;
+		data[1] = NCT7201_REG_CHANNEL_ENABLE_2_MASK;
+		err = regmap_bulk_write(chip->regmap, NCT7201_REG_CHANNEL_ENABLE_1,
+					data, ARRAY_SIZE(data));
+		if (err < 0)
+			return dev_err_probe(&chip->client->dev, -EIO,
+					    "Failed to write NCT7201_REG_CHANNEL_ENABLE_1 and NCT7201_REG_CHANNEL_ENABLE_2\n");
+	}
+
+	value = get_unaligned_le16(data);
+	chip->vin_mask = value;
+
+	/* Start monitoring if needed */
+	err = regmap_read(chip->regmap, NCT7201_REG_CONFIGURATION, &value);
+	if (err < 0)
+		return dev_err_probe(&chip->client->dev, -EIO,
+				     "Failed to read NCT7201_REG_CONFIGURATION\n");
+
+	regmap_set_bits(chip->regmap, NCT7201_REG_CONFIGURATION, NCT7201_BIT_CONFIGURATION_START);
+
+	return 0;
+}
+
+static int nct7201_probe(struct i2c_client *client)
+{
+	const struct nct7201_adc_model_data *model_data;
+	struct nct7201_chip_info *chip;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	model_data = i2c_get_match_data(client);
+	if (!model_data)
+		return -EINVAL;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*chip));
+	if (!indio_dev)
+		return -ENOMEM;
+	chip = iio_priv(indio_dev);
+
+	chip->regmap = devm_regmap_init_i2c(client, &nct7201_regmap8_config);
+	if (IS_ERR(chip->regmap))
+		return dev_err_probe(&client->dev, PTR_ERR(chip->regmap),
+			"Failed to init regmap\n");
+
+	chip->regmap16 = devm_regmap_init_i2c(client, &nct7201_regmap16_config);
+	if (IS_ERR(chip->regmap16))
+		return dev_err_probe(&client->dev, PTR_ERR(chip->regmap16),
+			"Failed to init regmap16\n");
+
+	chip->num_vin_channels = model_data->num_vin_channels;
+
+	ret = devm_mutex_init(&client->dev, &chip->access_lock);
+	if (ret)
+		return ret;
+
+	chip->client = client;
+
+	ret = nct7201_init_chip(chip);
+	if (ret < 0)
+		return ret;
+
+	indio_dev->name = model_data->model_name;
+	indio_dev->channels = model_data->channels;
+	indio_dev->num_channels = model_data->num_channels;
+	if (client->irq)
+		indio_dev->info = &nct7201_info;
+	else
+		indio_dev->info = &nct7201_info_no_irq;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id nct7201_id[] = {
+	{ .name = "nct7201", .driver_data = (kernel_ulong_t)&nct7201_model_data },
+	{ .name = "nct7202", .driver_data = (kernel_ulong_t)&nct7202_model_data },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, nct7201_id);
+
+static const struct of_device_id nct7201_of_match[] = {
+	{
+		.compatible = "nuvoton,nct7201",
+		.data = &nct7201_model_data,
+	},
+	{
+		.compatible = "nuvoton,nct7202",
+		.data = &nct7202_model_data,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, nct7201_of_match);
+
+static struct i2c_driver nct7201_driver = {
+	.driver = {
+		.name	= "nct7201",
+		.of_match_table = nct7201_of_match,
+	},
+	.probe = nct7201_probe,
+	.id_table = nct7201_id,
+};
+module_i2c_driver(nct7201_driver);
+
+MODULE_AUTHOR("Eason Yang <j2anfernee@gmail.com>");
+MODULE_DESCRIPTION("Nuvoton NCT7201 voltage monitor driver");
+MODULE_LICENSE("GPL");
-- 
2.34.1