// SPDX-License-Identifier: GPL-2.0+
/*
 * IIO driver for PAC1934 Multi-Channel DC Power/Energy Monitor
 *
 * Copyright (C) 2017-2024 Microchip Technology Inc. and its subsidiaries
 *
 * Author: Bogdan Bolocan <bogdan.bolocan@microchip.com>
 * Author: Victor Tudose
 * Author: Marius Cristea <marius.cristea@microchip.com>
 *
 * Datasheet for PAC1931, PAC1932, PAC1933 and PAC1934 can be found here:
 * https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/PAC1931-Family-Data-Sheet-DS20005850E.pdf
 */

#include <linux/acpi.h>
#include <linux/bitfield.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <asm/unaligned.h>

/*
 * maximum accumulation time should be (17 * 60 * 1000) around 17 minutes@1024 sps
 * till PAC1934 accumulation registers starts to saturate
 */
#define PAC1934_MAX_RFSH_LIMIT_MS		60000
/* 50msec is the timeout for validity of the cached registers */
#define PAC1934_MIN_POLLING_TIME_MS		50
/*
 * 1000usec is the minimum wait time for normal conversions when sample
 * rate doesn't change
 */
#define PAC1934_MIN_UPDATE_WAIT_TIME_US		1000

/* 32000mV */
#define PAC1934_VOLTAGE_MILLIVOLTS_MAX		32000
/* voltage bits resolution when set for unsigned values */
#define PAC1934_VOLTAGE_U_RES			16
/* voltage bits resolution when set for signed values */
#define PAC1934_VOLTAGE_S_RES			15

/*
 * max signed value that can be stored on 32 bits and 8 digits fractional value
 * (2^31 - 1) * 10^8 + 99999999
 */
#define PAC_193X_MAX_POWER_ACC			214748364799999999LL
/*
 * min signed value that can be stored on 32 bits and 8 digits fractional value
 * -(2^31) * 10^8 - 99999999
 */
#define PAC_193X_MIN_POWER_ACC			-214748364899999999LL

#define PAC1934_MAX_NUM_CHANNELS		4

#define PAC1934_MEAS_REG_LEN			76
#define PAC1934_CTRL_REG_LEN			12

#define PAC1934_DEFAULT_CHIP_SAMP_SPEED_HZ	1024

/* I2C address map */
#define PAC1934_REFRESH_REG_ADDR		0x00
#define PAC1934_CTRL_REG_ADDR			0x01
#define PAC1934_ACC_COUNT_REG_ADDR		0x02
#define PAC1934_VPOWER_ACC_1_ADDR		0x03
#define PAC1934_VPOWER_ACC_2_ADDR		0x04
#define PAC1934_VPOWER_ACC_3_ADDR		0x05
#define PAC1934_VPOWER_ACC_4_ADDR		0x06
#define PAC1934_VBUS_1_ADDR			0x07
#define PAC1934_VBUS_2_ADDR			0x08
#define PAC1934_VBUS_3_ADDR			0x09
#define PAC1934_VBUS_4_ADDR			0x0A
#define PAC1934_VSENSE_1_ADDR			0x0B
#define PAC1934_VSENSE_2_ADDR			0x0C
#define PAC1934_VSENSE_3_ADDR			0x0D
#define PAC1934_VSENSE_4_ADDR			0x0E
#define PAC1934_VBUS_AVG_1_ADDR			0x0F
#define PAC1934_VBUS_AVG_2_ADDR			0x10
#define PAC1934_VBUS_AVG_3_ADDR			0x11
#define PAC1934_VBUS_AVG_4_ADDR			0x12
#define PAC1934_VSENSE_AVG_1_ADDR		0x13
#define PAC1934_VSENSE_AVG_2_ADDR		0x14
#define PAC1934_VSENSE_AVG_3_ADDR		0x15
#define PAC1934_VSENSE_AVG_4_ADDR		0x16
#define PAC1934_VPOWER_1_ADDR			0x17
#define PAC1934_VPOWER_2_ADDR			0x18
#define PAC1934_VPOWER_3_ADDR			0x19
#define PAC1934_VPOWER_4_ADDR			0x1A
#define PAC1934_REFRESH_V_REG_ADDR		0x1F
#define PAC1934_CTRL_STAT_REGS_ADDR		0x1C
#define PAC1934_PID_REG_ADDR			0xFD
#define PAC1934_MID_REG_ADDR			0xFE
#define PAC1934_RID_REG_ADDR			0xFF

/* PRODUCT ID REGISTER + MANUFACTURER ID REGISTER + REVISION ID REGISTER */
#define PAC1934_ID_REG_LEN			3
#define PAC1934_PID_IDX				0
#define PAC1934_MID_IDX				1
#define PAC1934_RID_IDX				2

#define PAC1934_ACPI_GET_NAMES_AND_MOHMS_VALS	1
#define PAC1934_ACPI_GET_UOHMS_VALS		2
#define PAC1934_ACPI_GET_BIPOLAR_SETTINGS	4
#define PAC1934_ACPI_GET_SAMP			5

#define PAC1934_SAMPLE_RATE_SHIFT		6

#define PAC1934_VBUS_SENSE_REG_LEN		2
#define PAC1934_ACC_REG_LEN			3
#define PAC1934_VPOWER_REG_LEN			4
#define PAC1934_VPOWER_ACC_REG_LEN		6
#define PAC1934_MAX_REGISTER_LENGTH		6

#define PAC1934_CUSTOM_ATTR_FOR_CHANNEL		1

/*
 * relative offsets when using multi-byte reads/writes even though these
 * bytes are read one after the other, they are not at adjacent memory
 * locations within the I2C memory map. The chip can skip some addresses
 */
#define PAC1934_CHANNEL_DIS_REG_OFF		0
#define PAC1934_NEG_PWR_REG_OFF			1

/*
 * when reading/writing multiple bytes from offset PAC1934_CHANNEL_DIS_REG_OFF,
 * the chip jumps over the 0x1E (REFRESH_G) and 0x1F (REFRESH_V) offsets
 */
#define PAC1934_SLOW_REG_OFF			2
#define PAC1934_CTRL_ACT_REG_OFF		3
#define PAC1934_CHANNEL_DIS_ACT_REG_OFF		4
#define PAC1934_NEG_PWR_ACT_REG_OFF		5
#define PAC1934_CTRL_LAT_REG_OFF		6
#define PAC1934_CHANNEL_DIS_LAT_REG_OFF		7
#define PAC1934_NEG_PWR_LAT_REG_OFF		8
#define PAC1934_PID_REG_OFF			9
#define PAC1934_MID_REG_OFF			10
#define PAC1934_REV_REG_OFF			11
#define PAC1934_CTRL_STATUS_INFO_LEN		12

#define PAC1934_MID				0x5D
#define PAC1931_PID				0x58
#define PAC1932_PID				0x59
#define PAC1933_PID				0x5A
#define PAC1934_PID				0x5B

/* Scale constant = (10^3 * 3.2 * 10^9 / 2^28) for mili Watt-second */
#define PAC1934_SCALE_CONSTANT			11921

#define PAC1934_MAX_VPOWER_RSHIFTED_BY_28B	11921
#define PAC1934_MAX_VSENSE_RSHIFTED_BY_16B	1525

#define PAC1934_DEV_ATTR(name) (&iio_dev_attr_##name.dev_attr.attr)

#define PAC1934_CRTL_SAMPLE_RATE_MASK	GENMASK(7, 6)
#define PAC1934_CHAN_SLEEP_MASK		BIT(5)
#define PAC1934_CHAN_SLEEP_SET		BIT(5)
#define PAC1934_CHAN_SINGLE_MASK	BIT(4)
#define PAC1934_CHAN_SINGLE_SHOT_SET	BIT(4)
#define PAC1934_CHAN_ALERT_MASK		BIT(3)
#define PAC1934_CHAN_ALERT_EN		BIT(3)
#define PAC1934_CHAN_ALERT_CC_MASK	BIT(2)
#define PAC1934_CHAN_ALERT_CC_EN	BIT(2)
#define PAC1934_CHAN_OVF_ALERT_MASK	BIT(1)
#define PAC1934_CHAN_OVF_ALERT_EN	BIT(1)
#define PAC1934_CHAN_OVF_MASK		BIT(0)

#define PAC1934_CHAN_DIS_CH1_OFF_MASK	BIT(7)
#define PAC1934_CHAN_DIS_CH2_OFF_MASK	BIT(6)
#define PAC1934_CHAN_DIS_CH3_OFF_MASK	BIT(5)
#define PAC1934_CHAN_DIS_CH4_OFF_MASK	BIT(4)
#define PAC1934_SMBUS_TIMEOUT_MASK	BIT(3)
#define PAC1934_SMBUS_BYTECOUNT_MASK	BIT(2)
#define PAC1934_SMBUS_NO_SKIP_MASK	BIT(1)

#define PAC1934_NEG_PWR_CH1_BIDI_MASK	BIT(7)
#define PAC1934_NEG_PWR_CH2_BIDI_MASK	BIT(6)
#define PAC1934_NEG_PWR_CH3_BIDI_MASK	BIT(5)
#define PAC1934_NEG_PWR_CH4_BIDI_MASK	BIT(4)
#define PAC1934_NEG_PWR_CH1_BIDV_MASK	BIT(3)
#define PAC1934_NEG_PWR_CH2_BIDV_MASK	BIT(2)
#define PAC1934_NEG_PWR_CH3_BIDV_MASK	BIT(1)
#define PAC1934_NEG_PWR_CH4_BIDV_MASK	BIT(0)

/*
 * Universal Unique Identifier (UUID),
 * 033771E0-1705-47B4-9535-D1BBE14D9A09,
 * is reserved to Microchip for the PAC1934.
 */
#define PAC1934_DSM_UUID		"033771E0-1705-47B4-9535-D1BBE14D9A09"

enum pac1934_ids {
	PAC1931,
	PAC1932,
	PAC1933,
	PAC1934
};

enum pac1934_samps {
	PAC1934_SAMP_1024SPS,
	PAC1934_SAMP_256SPS,
	PAC1934_SAMP_64SPS,
	PAC1934_SAMP_8SPS
};

/*
 * these indexes are exactly describing the element order within a single
 * PAC1934 phys channel IIO channel descriptor; see the static const struct
 * iio_chan_spec pac1934_single_channel[] declaration
 */
enum pac1934_ch_idx {
	PAC1934_CH_ENERGY,
	PAC1934_CH_POWER,
	PAC1934_CH_VOLTAGE,
	PAC1934_CH_CURRENT,
	PAC1934_CH_VOLTAGE_AVERAGE,
	PAC1934_CH_CURRENT_AVERAGE
};

/**
 * struct pac1934_features - features of a pac1934 instance
 * @phys_channels:	number of physical channels supported by the chip
 * @name:		chip's name
 */
struct pac1934_features {
	u8		phys_channels;
	const char	*name;
};

static const unsigned int samp_rate_map_tbl[] = {
	[PAC1934_SAMP_1024SPS] = 1024,
	[PAC1934_SAMP_256SPS] = 256,
	[PAC1934_SAMP_64SPS] = 64,
	[PAC1934_SAMP_8SPS] = 8,
};

static const struct pac1934_features pac1934_chip_config[] = {
	[PAC1931] = {
	    .phys_channels = 1,
	    .name = "pac1931",
	},
	[PAC1932] = {
	    .phys_channels = 2,
	    .name = "pac1932",
	},
	[PAC1933] = {
	    .phys_channels = 3,
	    .name = "pac1933",
	},
	[PAC1934] = {
	    .phys_channels = 4,
	    .name = "pac1934",
	},
};

/**
 * struct reg_data - data from the registers
 * @meas_regs:			snapshot of raw measurements registers
 * @ctrl_regs:			snapshot of control registers
 * @energy_sec_acc:		snapshot of energy values
 * @vpower_acc:			accumulated vpower values
 * @vpower:			snapshot of vpower registers
 * @vbus:			snapshot of vbus registers
 * @vbus_avg:			averages of vbus registers
 * @vsense:			snapshot of vsense registers
 * @vsense_avg:			averages of vsense registers
 * @num_enabled_channels:	count of how many chip channels are currently enabled
 */
struct reg_data {
	u8	meas_regs[PAC1934_MEAS_REG_LEN];
	u8	ctrl_regs[PAC1934_CTRL_REG_LEN];
	s64	energy_sec_acc[PAC1934_MAX_NUM_CHANNELS];
	s64	vpower_acc[PAC1934_MAX_NUM_CHANNELS];
	s32	vpower[PAC1934_MAX_NUM_CHANNELS];
	s32	vbus[PAC1934_MAX_NUM_CHANNELS];
	s32	vbus_avg[PAC1934_MAX_NUM_CHANNELS];
	s32	vsense[PAC1934_MAX_NUM_CHANNELS];
	s32	vsense_avg[PAC1934_MAX_NUM_CHANNELS];
	u8	num_enabled_channels;
};

/**
 * struct pac1934_chip_info - information about the chip
 * @client:			the i2c-client attached to the device
 * @lock:			synchronize access to driver's state members
 * @work_chip_rfsh:		work queue used for refresh commands
 * @phys_channels:		phys channels count
 * @active_channels:		array of values, true means that channel is active
 * @enable_energy:		array of values, true means that channel energy is measured
 * @bi_dir:			array of bools, true means that channel is bidirectional
 * @chip_variant:		chip variant
 * @chip_revision:		chip revision
 * @shunts:			shunts
 * @chip_reg_data:		chip reg data
 * @sample_rate_value:		sampling frequency
 * @labels:			table with channels labels
 * @iio_info:			iio_info
 * @tstamp:			chip's uptime
 */
struct pac1934_chip_info {
	struct i2c_client	*client;
	struct mutex		lock; /* synchronize access to driver's state members */
	struct delayed_work	work_chip_rfsh;
	u8			phys_channels;
	bool			active_channels[PAC1934_MAX_NUM_CHANNELS];
	bool			enable_energy[PAC1934_MAX_NUM_CHANNELS];
	bool			bi_dir[PAC1934_MAX_NUM_CHANNELS];
	u8			chip_variant;
	u8			chip_revision;
	u32			shunts[PAC1934_MAX_NUM_CHANNELS];
	struct reg_data		chip_reg_data;
	s32			sample_rate_value;
	char			*labels[PAC1934_MAX_NUM_CHANNELS];
	struct iio_info		iio_info;
	unsigned long		tstamp;
};

#define TO_PAC1934_CHIP_INFO(d) container_of(d, struct pac1934_chip_info, work_chip_rfsh)

#define PAC1934_VPOWER_ACC_CHANNEL(_index, _si, _address) {			\
	.type = IIO_ENERGY,							\
	.address = (_address),							\
	.indexed = 1,								\
	.channel = (_index),							\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)	|			\
			      BIT(IIO_CHAN_INFO_SCALE)	|			\
			      BIT(IIO_CHAN_INFO_ENABLE),			\
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),		\
	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
	.scan_index = (_si),							\
	.scan_type = {								\
		.sign = 'u',							\
		.realbits = 48,							\
		.storagebits = 64,						\
		.endianness = IIO_CPU,						\
	}									\
}

#define PAC1934_VBUS_CHANNEL(_index, _si, _address) {				\
	.type = IIO_VOLTAGE,							\
	.address = (_address),							\
	.indexed = 1,								\
	.channel = (_index),							\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)	|			\
			      BIT(IIO_CHAN_INFO_SCALE),				\
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),		\
	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
	.scan_index = (_si),							\
	.scan_type = {								\
		.sign = 'u',							\
		.realbits = 16,							\
		.storagebits = 16,						\
		.endianness = IIO_CPU,						\
	}									\
}

#define PAC1934_VBUS_AVG_CHANNEL(_index, _si, _address) {			\
	.type = IIO_VOLTAGE,							\
	.address = (_address),							\
	.indexed = 1,								\
	.channel = (_index),							\
	.info_mask_separate = BIT(IIO_CHAN_INFO_AVERAGE_RAW)	|		\
			      BIT(IIO_CHAN_INFO_SCALE),				\
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),		\
	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
	.scan_index = (_si),							\
	.scan_type = {								\
		.sign = 'u',							\
		.realbits = 16,							\
		.storagebits = 16,						\
		.endianness = IIO_CPU,						\
	}									\
}

#define PAC1934_VSENSE_CHANNEL(_index, _si, _address) {				\
	.type = IIO_CURRENT,							\
	.address = (_address),							\
	.indexed = 1,								\
	.channel = (_index),							\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)	|			\
			      BIT(IIO_CHAN_INFO_SCALE),				\
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),		\
	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
	.scan_index = (_si),							\
	.scan_type = {								\
		.sign = 'u',							\
		.realbits = 16,							\
		.storagebits = 16,						\
		.endianness = IIO_CPU,						\
	}									\
}

#define PAC1934_VSENSE_AVG_CHANNEL(_index, _si, _address) {			\
	.type = IIO_CURRENT,							\
	.address = (_address),							\
	.indexed = 1,								\
	.channel = (_index),							\
	.info_mask_separate = BIT(IIO_CHAN_INFO_AVERAGE_RAW)	|		\
			      BIT(IIO_CHAN_INFO_SCALE),				\
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),		\
	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
	.scan_index = (_si),							\
	.scan_type = {								\
		.sign = 'u',							\
		.realbits = 16,							\
		.storagebits = 16,						\
		.endianness = IIO_CPU,						\
	}									\
}

#define PAC1934_VPOWER_CHANNEL(_index, _si, _address) {				\
	.type = IIO_POWER,							\
	.address = (_address),							\
	.indexed = 1,								\
	.channel = (_index),							\
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)	|			\
			      BIT(IIO_CHAN_INFO_SCALE),				\
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),		\
	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
	.scan_index = (_si),							\
	.scan_type = {								\
		.sign = 'u',							\
		.realbits = 28,							\
		.storagebits = 32,						\
		.shift = 4,							\
		.endianness = IIO_CPU,						\
	}									\
}

static const struct iio_chan_spec pac1934_single_channel[] = {
	PAC1934_VPOWER_ACC_CHANNEL(0, 0, PAC1934_VPOWER_ACC_1_ADDR),
	PAC1934_VPOWER_CHANNEL(0, 0, PAC1934_VPOWER_1_ADDR),
	PAC1934_VBUS_CHANNEL(0, 0, PAC1934_VBUS_1_ADDR),
	PAC1934_VSENSE_CHANNEL(0, 0, PAC1934_VSENSE_1_ADDR),
	PAC1934_VBUS_AVG_CHANNEL(0, 0, PAC1934_VBUS_AVG_1_ADDR),
	PAC1934_VSENSE_AVG_CHANNEL(0, 0, PAC1934_VSENSE_AVG_1_ADDR),
};

/* Low-level I2c functions used to transfer up to 76 bytes at once */
static int pac1934_i2c_read(struct i2c_client *client, u8 reg_addr,
			    void *databuf, u8 len)
{
	int ret;
	struct i2c_msg msgs[2] = {
		{
			.addr = client->addr,
			.len = 1,
			.buf = (u8 *)&reg_addr,
		},
		{
			.addr = client->addr,
			.len = len,
			.buf = databuf,
			.flags = I2C_M_RD
		}
	};

	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
	if (ret < 0)
		return ret;

	return 0;
}

static int pac1934_get_samp_rate_idx(struct pac1934_chip_info *info,
				     u32 new_samp_rate)
{
	int cnt;

	for (cnt = 0; cnt < ARRAY_SIZE(samp_rate_map_tbl); cnt++)
		if (new_samp_rate == samp_rate_map_tbl[cnt])
			return cnt;

	/* not a valid sample rate value */
	return -EINVAL;
}

static ssize_t pac1934_shunt_value_show(struct device *dev,
					struct device_attribute *attr,
					char *buf)
{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct pac1934_chip_info *info = iio_priv(indio_dev);
	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);

	return sysfs_emit(buf, "%u\n", info->shunts[this_attr->address]);
}

static ssize_t pac1934_shunt_value_store(struct device *dev,
					 struct device_attribute *attr,
					 const char *buf, size_t count)
{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct pac1934_chip_info *info = iio_priv(indio_dev);
	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
	int sh_val;

	if (kstrtouint(buf, 10, &sh_val)) {
		dev_err(dev, "Shunt value is not valid\n");
		return -EINVAL;
	}

	scoped_guard(mutex, &info->lock)
		info->shunts[this_attr->address] = sh_val;

	return count;
}

static int pac1934_read_avail(struct iio_dev *indio_dev,
			      struct iio_chan_spec const *channel,
			      const int **vals, int *type, int *length, long mask)
{
	switch (mask) {
	case IIO_CHAN_INFO_SAMP_FREQ:
		*type = IIO_VAL_INT;
		*vals = samp_rate_map_tbl;
		*length = ARRAY_SIZE(samp_rate_map_tbl);
		return IIO_AVAIL_LIST;
	}

	return -EINVAL;
}

static int pac1934_send_refresh(struct pac1934_chip_info *info,
				u8 refresh_cmd, u32 wait_time)
{
	/* this function only sends REFRESH or REFRESH_V */
	struct i2c_client *client = info->client;
	int ret;
	u8 bidir_reg;
	bool revision_bug = false;

	if (info->chip_revision == 2 || info->chip_revision == 3) {
		/*
		 * chip rev 2 and 3 bug workaround
		 * see: PAC1934 Family Data Sheet Errata DS80000836A.pdf
		 */
		revision_bug = true;

		bidir_reg =
			FIELD_PREP(PAC1934_NEG_PWR_CH1_BIDI_MASK, info->bi_dir[0]) |
			FIELD_PREP(PAC1934_NEG_PWR_CH2_BIDI_MASK, info->bi_dir[1]) |
			FIELD_PREP(PAC1934_NEG_PWR_CH3_BIDI_MASK, info->bi_dir[2]) |
			FIELD_PREP(PAC1934_NEG_PWR_CH4_BIDI_MASK, info->bi_dir[3]) |
			FIELD_PREP(PAC1934_NEG_PWR_CH1_BIDV_MASK, info->bi_dir[0]) |
			FIELD_PREP(PAC1934_NEG_PWR_CH2_BIDV_MASK, info->bi_dir[1]) |
			FIELD_PREP(PAC1934_NEG_PWR_CH3_BIDV_MASK, info->bi_dir[2]) |
			FIELD_PREP(PAC1934_NEG_PWR_CH4_BIDV_MASK, info->bi_dir[3]);

		ret = i2c_smbus_write_byte_data(client,
						PAC1934_CTRL_STAT_REGS_ADDR +
						PAC1934_NEG_PWR_REG_OFF,
						bidir_reg);
		if (ret)
			return ret;
	}

	ret = i2c_smbus_write_byte(client, refresh_cmd);
	if (ret) {
		dev_err(&client->dev, "%s - cannot send 0x%02X\n",
			__func__, refresh_cmd);
		return ret;
	}

	if (revision_bug) {
		/*
		 * chip rev 2 and 3 bug workaround - write again the same
		 * register write the updated registers back
		 */
		ret = i2c_smbus_write_byte_data(client,
						PAC1934_CTRL_STAT_REGS_ADDR +
						PAC1934_NEG_PWR_REG_OFF, bidir_reg);
		if (ret)
			return ret;
	}

	/* register data retrieval timestamp */
	info->tstamp = jiffies;

	/* wait till the data is available */
	usleep_range(wait_time, wait_time + 100);

	return ret;
}

static int pac1934_reg_snapshot(struct pac1934_chip_info *info,
				bool do_refresh, u8 refresh_cmd, u32 wait_time)
{
	int ret;
	struct i2c_client *client = info->client;
	u8 samp_shift, ctrl_regs_tmp;
	u8 *offset_reg_data_p;
	u16 tmp_value;
	u32 samp_rate, cnt, tmp;
	s64 curr_energy, inc;
	u64 tmp_energy;
	struct reg_data *reg_data;

	guard(mutex)(&info->lock);

	if (do_refresh) {
		ret = pac1934_send_refresh(info, refresh_cmd, wait_time);
		if (ret < 0) {
			dev_err(&client->dev,
				"%s - cannot send refresh\n",
				__func__);
			return ret;
		}
	}

	ret = i2c_smbus_read_i2c_block_data(client, PAC1934_CTRL_STAT_REGS_ADDR,
					    PAC1934_CTRL_REG_LEN,
					    (u8 *)info->chip_reg_data.ctrl_regs);
	if (ret < 0) {
		dev_err(&client->dev,
			"%s - cannot read ctrl/status registers\n",
			__func__);
		return ret;
	}

	reg_data = &info->chip_reg_data;

	/* read the data registers */
	ret = pac1934_i2c_read(client, PAC1934_ACC_COUNT_REG_ADDR,
			       (u8 *)reg_data->meas_regs, PAC1934_MEAS_REG_LEN);
	if (ret) {
		dev_err(&client->dev,
			"%s - cannot read ACC_COUNT register: %d:%d\n",
			__func__, ret, PAC1934_MEAS_REG_LEN);
		return ret;
	}

	/* see how much shift is required by the sample rate */
	samp_rate = samp_rate_map_tbl[((reg_data->ctrl_regs[PAC1934_CTRL_LAT_REG_OFF]) >> 6)];
	samp_shift = get_count_order(samp_rate);

	ctrl_regs_tmp = reg_data->ctrl_regs[PAC1934_CHANNEL_DIS_LAT_REG_OFF];
	offset_reg_data_p = &reg_data->meas_regs[PAC1934_ACC_REG_LEN];

	/* start with VPOWER_ACC */
	for (cnt = 0; cnt < info->phys_channels; cnt++) {
		/* check if the channel is active, skip all fields if disabled */
		if ((ctrl_regs_tmp << cnt) & 0x80)
			continue;

		/* skip if the energy accumulation is disabled */
		if (info->enable_energy[cnt]) {
			curr_energy = info->chip_reg_data.energy_sec_acc[cnt];

			tmp_energy = get_unaligned_be48(offset_reg_data_p);

			if (info->bi_dir[cnt])
				reg_data->vpower_acc[cnt] = sign_extend64(tmp_energy, 47);
			else
				reg_data->vpower_acc[cnt] = tmp_energy;

			/*
			 * compute the scaled to 1 second accumulated energy value;
			 * energy accumulator scaled to 1sec = VPOWER_ACC/2^samp_shift
			 * the chip's sampling rate is 2^samp_shift samples/sec
			 */
			inc = (reg_data->vpower_acc[cnt] >> samp_shift);

			/* add the power_acc field */
			curr_energy += inc;

			clamp(curr_energy, PAC_193X_MIN_POWER_ACC, PAC_193X_MAX_POWER_ACC);

			reg_data->energy_sec_acc[cnt] = curr_energy;
		}

		offset_reg_data_p += PAC1934_VPOWER_ACC_REG_LEN;
	}

	/* continue with VBUS */
	for (cnt = 0; cnt < info->phys_channels; cnt++) {
		if ((ctrl_regs_tmp << cnt) & 0x80)
			continue;

		tmp_value = get_unaligned_be16(offset_reg_data_p);

		if (info->bi_dir[cnt])
			reg_data->vbus[cnt] = sign_extend32((u32)(tmp_value), 15);
		else
			reg_data->vbus[cnt] = tmp_value;

		offset_reg_data_p += PAC1934_VBUS_SENSE_REG_LEN;
	}

	/* VSENSE */
	for (cnt = 0; cnt < info->phys_channels; cnt++) {
		if ((ctrl_regs_tmp << cnt) & 0x80)
			continue;

		tmp_value = get_unaligned_be16(offset_reg_data_p);

		if (info->bi_dir[cnt])
			reg_data->vsense[cnt] = sign_extend32((u32)(tmp_value), 15);
		else
			reg_data->vsense[cnt] = tmp_value;

		offset_reg_data_p += PAC1934_VBUS_SENSE_REG_LEN;
	}

	/* VBUS_AVG */
	for (cnt = 0; cnt < info->phys_channels; cnt++) {
		if ((ctrl_regs_tmp << cnt) & 0x80)
			continue;

		tmp_value = get_unaligned_be16(offset_reg_data_p);

		if (info->bi_dir[cnt])
			reg_data->vbus_avg[cnt] = sign_extend32((u32)(tmp_value), 15);
		else
			reg_data->vbus_avg[cnt] = tmp_value;

		offset_reg_data_p += PAC1934_VBUS_SENSE_REG_LEN;
	}

	/* VSENSE_AVG */
	for (cnt = 0; cnt < info->phys_channels; cnt++) {
		if ((ctrl_regs_tmp << cnt) & 0x80)
			continue;

		tmp_value = get_unaligned_be16(offset_reg_data_p);

		if (info->bi_dir[cnt])
			reg_data->vsense_avg[cnt] = sign_extend32((u32)(tmp_value), 15);
		else
			reg_data->vsense_avg[cnt] = tmp_value;

		offset_reg_data_p += PAC1934_VBUS_SENSE_REG_LEN;
	}

	/* VPOWER */
	for (cnt = 0; cnt < info->phys_channels; cnt++) {
		if ((ctrl_regs_tmp << cnt) & 0x80)
			continue;

		tmp = get_unaligned_be32(offset_reg_data_p) >> 4;

		if (info->bi_dir[cnt])
			reg_data->vpower[cnt] = sign_extend32(tmp, 27);
		else
			reg_data->vpower[cnt] = tmp;

		offset_reg_data_p += PAC1934_VPOWER_REG_LEN;
	}

	return 0;
}

static int pac1934_retrieve_data(struct pac1934_chip_info *info,
				 u32 wait_time)
{
	int ret = 0;

	/*
	 * check if the minimal elapsed time has passed and if so,
	 * re-read the chip, otherwise the cached info is just fine
	 */
	if (time_after(jiffies, info->tstamp + msecs_to_jiffies(PAC1934_MIN_POLLING_TIME_MS))) {
		ret = pac1934_reg_snapshot(info, true, PAC1934_REFRESH_REG_ADDR,
					   wait_time);

		/*
		 * Re-schedule the work for the read registers on timeout
		 * (to prevent chip registers saturation)
		 */
		mod_delayed_work(system_wq, &info->work_chip_rfsh,
				 msecs_to_jiffies(PAC1934_MAX_RFSH_LIMIT_MS));
	}

	return ret;
}

static int pac1934_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan, int *val,
			    int *val2, long mask)
{
	struct pac1934_chip_info *info = iio_priv(indio_dev);
	s64 curr_energy;
	int ret, channel = chan->channel - 1;

	/*
	 * For AVG the index should be between 5 to 8.
	 * To calculate PAC1934_CH_VOLTAGE_AVERAGE,
	 * respectively PAC1934_CH_CURRENT real index, we need
	 * to remove the added offset (PAC1934_MAX_NUM_CHANNELS).
	 */
	if (channel >= PAC1934_MAX_NUM_CHANNELS)
		channel = channel - PAC1934_MAX_NUM_CHANNELS;

	ret = pac1934_retrieve_data(info, PAC1934_MIN_UPDATE_WAIT_TIME_US);
	if (ret < 0)
		return ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		switch (chan->type) {
		case IIO_VOLTAGE:
			*val = info->chip_reg_data.vbus[channel];
			return IIO_VAL_INT;
		case IIO_CURRENT:
			*val = info->chip_reg_data.vsense[channel];
			return IIO_VAL_INT;
		case IIO_POWER:
			*val = info->chip_reg_data.vpower[channel];
			return IIO_VAL_INT;
		case IIO_ENERGY:
			curr_energy = info->chip_reg_data.energy_sec_acc[channel];
			*val = (u32)curr_energy;
			*val2 = (u32)(curr_energy >> 32);
			return IIO_VAL_INT_64;
		default:
			return -EINVAL;
		}
	case IIO_CHAN_INFO_AVERAGE_RAW:
		switch (chan->type) {
		case IIO_VOLTAGE:
			*val = info->chip_reg_data.vbus_avg[channel];
			return IIO_VAL_INT;
		case IIO_CURRENT:
			*val = info->chip_reg_data.vsense_avg[channel];
			return IIO_VAL_INT;
		default:
			return -EINVAL;
		}
	case IIO_CHAN_INFO_SCALE:
		switch (chan->address) {
		/* Voltages - scale for millivolts */
		case PAC1934_VBUS_1_ADDR:
		case PAC1934_VBUS_2_ADDR:
		case PAC1934_VBUS_3_ADDR:
		case PAC1934_VBUS_4_ADDR:
		case PAC1934_VBUS_AVG_1_ADDR:
		case PAC1934_VBUS_AVG_2_ADDR:
		case PAC1934_VBUS_AVG_3_ADDR:
		case PAC1934_VBUS_AVG_4_ADDR:
			*val = PAC1934_VOLTAGE_MILLIVOLTS_MAX;
			if (chan->scan_type.sign == 'u')
				*val2 = PAC1934_VOLTAGE_U_RES;
			else
				*val2 = PAC1934_VOLTAGE_S_RES;
			return IIO_VAL_FRACTIONAL_LOG2;
		/*
		 * Currents - scale for mA - depends on the
		 * channel's shunt value
		 * (100mV * 1000000) / (2^16 * shunt(uohm))
		 */
		case PAC1934_VSENSE_1_ADDR:
		case PAC1934_VSENSE_2_ADDR:
		case PAC1934_VSENSE_3_ADDR:
		case PAC1934_VSENSE_4_ADDR:
		case PAC1934_VSENSE_AVG_1_ADDR:
		case PAC1934_VSENSE_AVG_2_ADDR:
		case PAC1934_VSENSE_AVG_3_ADDR:
		case PAC1934_VSENSE_AVG_4_ADDR:
			*val = PAC1934_MAX_VSENSE_RSHIFTED_BY_16B;
			if (chan->scan_type.sign == 'u')
				*val2 = info->shunts[channel];
			else
				*val2 = info->shunts[channel] >> 1;
			return IIO_VAL_FRACTIONAL;
		/*
		 * Power - uW - it will use the combined scale
		 * for current and voltage
		 * current(mA) * voltage(mV) = power (uW)
		 */
		case PAC1934_VPOWER_1_ADDR:
		case PAC1934_VPOWER_2_ADDR:
		case PAC1934_VPOWER_3_ADDR:
		case PAC1934_VPOWER_4_ADDR:
			*val = PAC1934_MAX_VPOWER_RSHIFTED_BY_28B;
			if (chan->scan_type.sign == 'u')
				*val2 = info->shunts[channel];
			else
				*val2 = info->shunts[channel] >> 1;
			return IIO_VAL_FRACTIONAL;
		case PAC1934_VPOWER_ACC_1_ADDR:
		case PAC1934_VPOWER_ACC_2_ADDR:
		case PAC1934_VPOWER_ACC_3_ADDR:
		case PAC1934_VPOWER_ACC_4_ADDR:
			/*
			 * expresses the 32 bit scale value here compute
			 * the scale for energy (miliWatt-second or miliJoule)
			 */
			*val = PAC1934_SCALE_CONSTANT;

			if (chan->scan_type.sign == 'u')
				*val2 = info->shunts[channel];
			else
				*val2 = info->shunts[channel] >> 1;
			return IIO_VAL_FRACTIONAL;
		default:
			return -EINVAL;
		}
	case IIO_CHAN_INFO_SAMP_FREQ:
		*val = info->sample_rate_value;
		return IIO_VAL_INT;
	case IIO_CHAN_INFO_ENABLE:
		*val = info->enable_energy[channel];
		return IIO_VAL_INT;
	default:
		return -EINVAL;
	}
}

static int pac1934_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
			     int val, int val2, long mask)
{
	struct pac1934_chip_info *info = iio_priv(indio_dev);
	struct i2c_client *client = info->client;
	int ret = -EINVAL;
	s32 old_samp_rate;
	u8 ctrl_reg;

	switch (mask) {
	case IIO_CHAN_INFO_SAMP_FREQ:
		ret = pac1934_get_samp_rate_idx(info, val);
		if (ret < 0)
			return ret;

		/* write the new sampling value and trigger a snapshot(incl refresh) */
		scoped_guard(mutex, &info->lock) {
			ctrl_reg = FIELD_PREP(PAC1934_CRTL_SAMPLE_RATE_MASK, ret);
			ret = i2c_smbus_write_byte_data(client, PAC1934_CTRL_REG_ADDR, ctrl_reg);
			if (ret) {
				dev_err(&client->dev,
					"%s - can't update sample rate\n",
					__func__);
				return ret;
			}
		}

		old_samp_rate = info->sample_rate_value;
		info->sample_rate_value = val;

		/*
		 * now, force a snapshot with refresh - call retrieve
		 * data in order to update the refresh timer
		 * alter the timestamp in order to force trigger a
		 * register snapshot and a timestamp update
		 */
		info->tstamp -= msecs_to_jiffies(PAC1934_MIN_POLLING_TIME_MS);
		ret = pac1934_retrieve_data(info, (1024 / old_samp_rate) * 1000);
		if (ret < 0) {
			dev_err(&client->dev,
				"%s - cannot snapshot ctrl and measurement regs\n",
				__func__);
			return ret;
		}

		return 0;
	case IIO_CHAN_INFO_ENABLE:
		scoped_guard(mutex, &info->lock) {
			info->enable_energy[chan->channel - 1] = val ? true : false;
			if (!val)
				info->chip_reg_data.energy_sec_acc[chan->channel - 1] = 0;
		}

		return 0;
	default:
		return -EINVAL;
	}
}

static int pac1934_read_label(struct iio_dev *indio_dev,
			      struct iio_chan_spec const *chan, char *label)
{
	struct pac1934_chip_info *info = iio_priv(indio_dev);

	switch (chan->address) {
	case PAC1934_VBUS_1_ADDR:
	case PAC1934_VBUS_2_ADDR:
	case PAC1934_VBUS_3_ADDR:
	case PAC1934_VBUS_4_ADDR:
		return sysfs_emit(label, "%s_VBUS_%d\n",
				  info->labels[chan->scan_index],
				  chan->scan_index + 1);
	case PAC1934_VBUS_AVG_1_ADDR:
	case PAC1934_VBUS_AVG_2_ADDR:
	case PAC1934_VBUS_AVG_3_ADDR:
	case PAC1934_VBUS_AVG_4_ADDR:
		return sysfs_emit(label, "%s_VBUS_AVG_%d\n",
				  info->labels[chan->scan_index],
				  chan->scan_index + 1);
	case PAC1934_VSENSE_1_ADDR:
	case PAC1934_VSENSE_2_ADDR:
	case PAC1934_VSENSE_3_ADDR:
	case PAC1934_VSENSE_4_ADDR:
		return sysfs_emit(label, "%s_IBUS_%d\n",
				  info->labels[chan->scan_index],
				  chan->scan_index + 1);
	case PAC1934_VSENSE_AVG_1_ADDR:
	case PAC1934_VSENSE_AVG_2_ADDR:
	case PAC1934_VSENSE_AVG_3_ADDR:
	case PAC1934_VSENSE_AVG_4_ADDR:
		return sysfs_emit(label, "%s_IBUS_AVG_%d\n",
				  info->labels[chan->scan_index],
				  chan->scan_index + 1);
	case PAC1934_VPOWER_1_ADDR:
	case PAC1934_VPOWER_2_ADDR:
	case PAC1934_VPOWER_3_ADDR:
	case PAC1934_VPOWER_4_ADDR:
		return sysfs_emit(label, "%s_POWER_%d\n",
				  info->labels[chan->scan_index],
				  chan->scan_index + 1);
	case PAC1934_VPOWER_ACC_1_ADDR:
	case PAC1934_VPOWER_ACC_2_ADDR:
	case PAC1934_VPOWER_ACC_3_ADDR:
	case PAC1934_VPOWER_ACC_4_ADDR:
		return sysfs_emit(label, "%s_ENERGY_%d\n",
				  info->labels[chan->scan_index],
				  chan->scan_index + 1);
	}

	return 0;
}

static void pac1934_work_periodic_rfsh(struct work_struct *work)
{
	struct pac1934_chip_info *info = TO_PAC1934_CHIP_INFO((struct delayed_work *)work);
	struct device *dev = &info->client->dev;

	dev_dbg(dev, "%s - Periodic refresh\n", __func__);

	/* do a REFRESH, then read */
	pac1934_reg_snapshot(info, true, PAC1934_REFRESH_REG_ADDR,
			     PAC1934_MIN_UPDATE_WAIT_TIME_US);

	schedule_delayed_work(&info->work_chip_rfsh,
			      msecs_to_jiffies(PAC1934_MAX_RFSH_LIMIT_MS));
}

static int pac1934_read_revision(struct pac1934_chip_info *info, u8 *buf)
{
	int ret;
	struct i2c_client *client = info->client;

	ret = i2c_smbus_read_i2c_block_data(client, PAC1934_PID_REG_ADDR,
					    PAC1934_ID_REG_LEN,
					    buf);
	if (ret < 0) {
		dev_err(&client->dev, "cannot read revision\n");
		return ret;
	}

	return 0;
}

static int pac1934_chip_identify(struct pac1934_chip_info *info)
{
	u8 rev_info[PAC1934_ID_REG_LEN];
	struct device *dev = &info->client->dev;
	int ret = 0;

	ret = pac1934_read_revision(info, (u8 *)rev_info);
	if (ret)
		return ret;

	info->chip_variant = rev_info[PAC1934_PID_IDX];
	info->chip_revision = rev_info[PAC1934_RID_IDX];

	dev_dbg(dev, "Chip variant: 0x%02X\n", info->chip_variant);
	dev_dbg(dev, "Chip revision: 0x%02X\n", info->chip_revision);

	switch (info->chip_variant) {
	case PAC1934_PID:
		return PAC1934;
	case PAC1933_PID:
		return PAC1933;
	case PAC1932_PID:
		return PAC1932;
	case PAC1931_PID:
		return PAC1931;
	default:
		return -EINVAL;
	}
}

/*
 * documentation related to the ACPI device definition
 * https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ApplicationNotes/ApplicationNotes/PAC1934-Integration-Notes-for-Microsoft-Windows-10-and-Windows-11-Driver-Support-DS00002534.pdf
 */
static int pac1934_acpi_parse_channel_config(struct i2c_client *client,
					     struct pac1934_chip_info *info)
{
	acpi_handle handle;
	union acpi_object *rez;
	struct device *dev = &client->dev;
	unsigned short bi_dir_mask;
	int idx, i;
	guid_t guid;

	handle = ACPI_HANDLE(dev);

	guid_parse(PAC1934_DSM_UUID, &guid);

	rez = acpi_evaluate_dsm(handle, &guid, 0, PAC1934_ACPI_GET_NAMES_AND_MOHMS_VALS, NULL);
	if (!rez)
		return -EINVAL;

	for (i = 0; i < rez->package.count; i += 2) {
		idx = i / 2;
		info->labels[idx] =
			devm_kmemdup(dev, rez->package.elements[i].string.pointer,
				     (size_t)rez->package.elements[i].string.length + 1,
				     GFP_KERNEL);
		info->labels[idx][rez->package.elements[i].string.length] = '\0';
		info->shunts[idx] = rez->package.elements[i + 1].integer.value * 1000;
		info->active_channels[idx] = (info->shunts[idx] != 0);
	}

	ACPI_FREE(rez);

	rez = acpi_evaluate_dsm(handle, &guid, 1, PAC1934_ACPI_GET_UOHMS_VALS, NULL);
	if (!rez) {
		/*
		 * initializing with default values
		 * we assume all channels are unidirectional(the mask is zero)
		 * and assign the default sampling rate
		 */
		info->sample_rate_value = PAC1934_DEFAULT_CHIP_SAMP_SPEED_HZ;
		return 0;
	}

	for (i = 0; i < rez->package.count; i++) {
		idx = i;
		info->shunts[idx] = rez->package.elements[i].integer.value;
		info->active_channels[idx] = (info->shunts[idx] != 0);
	}

	ACPI_FREE(rez);

	rez = acpi_evaluate_dsm(handle, &guid, 1, PAC1934_ACPI_GET_BIPOLAR_SETTINGS, NULL);
	if (!rez)
		return -EINVAL;

	bi_dir_mask = rez->package.elements[0].integer.value;
	info->bi_dir[0] = ((bi_dir_mask & (1 << 3)) | (bi_dir_mask & (1 << 7))) != 0;
	info->bi_dir[1] = ((bi_dir_mask & (1 << 2)) | (bi_dir_mask & (1 << 6))) != 0;
	info->bi_dir[2] = ((bi_dir_mask & (1 << 1)) | (bi_dir_mask & (1 << 5))) != 0;
	info->bi_dir[3] = ((bi_dir_mask & (1 << 0)) | (bi_dir_mask & (1 << 4))) != 0;

	ACPI_FREE(rez);

	rez = acpi_evaluate_dsm(handle, &guid, 1, PAC1934_ACPI_GET_SAMP, NULL);
	if (!rez)
		return -EINVAL;

	info->sample_rate_value = rez->package.elements[0].integer.value;

	ACPI_FREE(rez);

	return 0;
}

static int pac1934_fw_parse_channel_config(struct i2c_client *client,
					   struct pac1934_chip_info *info)
{
	struct device *dev = &client->dev;
	unsigned int current_channel;
	int idx, ret;

	info->sample_rate_value = 1024;
	current_channel = 1;

	device_for_each_child_node_scoped(dev, node) {
		ret = fwnode_property_read_u32(node, "reg", &idx);
		if (ret)
			return dev_err_probe(dev, ret,
					     "reading invalid channel index\n");

		/* adjust idx to match channel index (1 to 4) from the datasheet */
		idx--;

		if (current_channel >= (info->phys_channels + 1) ||
		    idx >= info->phys_channels || idx < 0)
			return dev_err_probe(dev, -EINVAL,
					     "%s: invalid channel_index %d value\n",
					     fwnode_get_name(node), idx);

		/* enable channel */
		info->active_channels[idx] = true;

		ret = fwnode_property_read_u32(node, "shunt-resistor-micro-ohms",
					       &info->shunts[idx]);
		if (ret)
			return dev_err_probe(dev, ret,
					     "%s: invalid shunt-resistor value: %d\n",
					     fwnode_get_name(node), info->shunts[idx]);

		if (fwnode_property_present(node, "label")) {
			ret = fwnode_property_read_string(node, "label",
							  (const char **)&info->labels[idx]);
			if (ret)
				return dev_err_probe(dev, ret,
						     "%s: invalid rail-name value\n",
						     fwnode_get_name(node));
		}

		info->bi_dir[idx] = fwnode_property_read_bool(node, "bipolar");

		current_channel++;
	}

	return 0;
}

static void pac1934_cancel_delayed_work(void *dwork)
{
	cancel_delayed_work_sync(dwork);
}

static int pac1934_chip_configure(struct pac1934_chip_info *info)
{
	int cnt, ret;
	struct i2c_client *client = info->client;
	u8 regs[PAC1934_CTRL_STATUS_INFO_LEN], idx, ctrl_reg;
	u32 wait_time;

	info->chip_reg_data.num_enabled_channels = 0;
	for (cnt = 0;  cnt < info->phys_channels; cnt++) {
		if (info->active_channels[cnt])
			info->chip_reg_data.num_enabled_channels++;
	}

	/*
	 * read whatever information was gathered before the driver was loaded
	 * establish which channels are enabled/disabled and then establish the
	 * information retrieval mode (using SKIP or no).
	 * Read the chip ID values
	 */
	ret = i2c_smbus_read_i2c_block_data(client, PAC1934_CTRL_STAT_REGS_ADDR,
					    ARRAY_SIZE(regs),
					    (u8 *)regs);
	if (ret < 0) {
		dev_err_probe(&client->dev, ret,
			      "%s - cannot read regs from 0x%02X\n",
			      __func__, PAC1934_CTRL_STAT_REGS_ADDR);
		return ret;
	}

	/* write the CHANNEL_DIS and the NEG_PWR registers */
	regs[PAC1934_CHANNEL_DIS_REG_OFF] =
		FIELD_PREP(PAC1934_CHAN_DIS_CH1_OFF_MASK, info->active_channels[0] ? 0 : 1) |
		FIELD_PREP(PAC1934_CHAN_DIS_CH2_OFF_MASK, info->active_channels[1] ? 0 : 1) |
		FIELD_PREP(PAC1934_CHAN_DIS_CH3_OFF_MASK, info->active_channels[2] ? 0 : 1) |
		FIELD_PREP(PAC1934_CHAN_DIS_CH4_OFF_MASK, info->active_channels[3] ? 0 : 1) |
		FIELD_PREP(PAC1934_SMBUS_TIMEOUT_MASK, 0) |
		FIELD_PREP(PAC1934_SMBUS_BYTECOUNT_MASK, 0) |
		FIELD_PREP(PAC1934_SMBUS_NO_SKIP_MASK, 0);

	regs[PAC1934_NEG_PWR_REG_OFF] =
		FIELD_PREP(PAC1934_NEG_PWR_CH1_BIDI_MASK, info->bi_dir[0]) |
		FIELD_PREP(PAC1934_NEG_PWR_CH2_BIDI_MASK, info->bi_dir[1]) |
		FIELD_PREP(PAC1934_NEG_PWR_CH3_BIDI_MASK, info->bi_dir[2]) |
		FIELD_PREP(PAC1934_NEG_PWR_CH4_BIDI_MASK, info->bi_dir[3]) |
		FIELD_PREP(PAC1934_NEG_PWR_CH1_BIDV_MASK, info->bi_dir[0]) |
		FIELD_PREP(PAC1934_NEG_PWR_CH2_BIDV_MASK, info->bi_dir[1]) |
		FIELD_PREP(PAC1934_NEG_PWR_CH3_BIDV_MASK, info->bi_dir[2]) |
		FIELD_PREP(PAC1934_NEG_PWR_CH4_BIDV_MASK, info->bi_dir[3]);

	/* no SLOW triggered REFRESH, clear POR */
	regs[PAC1934_SLOW_REG_OFF] = 0;

	ret =  i2c_smbus_write_block_data(client, PAC1934_CTRL_STAT_REGS_ADDR,
					  ARRAY_SIZE(regs), (u8 *)regs);
	if (ret)
		return ret;

	/* Default sampling rate */
	ctrl_reg = FIELD_PREP(PAC1934_CRTL_SAMPLE_RATE_MASK, PAC1934_SAMP_1024SPS);

	ret = i2c_smbus_write_byte_data(client, PAC1934_CTRL_REG_ADDR, ctrl_reg);
	if (ret)
		return ret;

	/*
	 * send a REFRESH to the chip, so the new settings take place
	 * as well as resetting the accumulators
	 */
	ret = i2c_smbus_write_byte(client, PAC1934_REFRESH_REG_ADDR);
	if (ret) {
		dev_err(&client->dev,
			"%s - cannot send 0x%02X\n",
			__func__, PAC1934_REFRESH_REG_ADDR);
		return ret;
	}

	/*
	 * get the current(in the chip) sampling speed and compute the
	 * required timeout based on its value
	 * the timeout is 1/sampling_speed
	 */
	idx = regs[PAC1934_CTRL_ACT_REG_OFF] >> PAC1934_SAMPLE_RATE_SHIFT;
	wait_time = (1024 / samp_rate_map_tbl[idx]) * 1000;

	/*
	 * wait the maximum amount of time to be on the safe side
	 * the maximum wait time is for 8sps
	 */
	usleep_range(wait_time, wait_time + 100);

	INIT_DELAYED_WORK(&info->work_chip_rfsh, pac1934_work_periodic_rfsh);
	/* Setup the latest moment for reading the regs before saturation */
	schedule_delayed_work(&info->work_chip_rfsh,
			      msecs_to_jiffies(PAC1934_MAX_RFSH_LIMIT_MS));

	return devm_add_action_or_reset(&client->dev, pac1934_cancel_delayed_work,
					&info->work_chip_rfsh);
}

static int pac1934_prep_iio_channels(struct pac1934_chip_info *info, struct iio_dev *indio_dev)
{
	struct iio_chan_spec *ch_sp;
	int channel_size, attribute_count, cnt;
	void *dyn_ch_struct, *tmp_data;
	struct device *dev = &info->client->dev;

	/* find out dynamically how many IIO channels we need */
	attribute_count = 0;
	channel_size = 0;
	for (cnt = 0; cnt < info->phys_channels; cnt++) {
		if (!info->active_channels[cnt])
			continue;

		/* add the size of the properties of one chip physical channel */
		channel_size += sizeof(pac1934_single_channel);
		/* count how many enabled channels we have */
		attribute_count += ARRAY_SIZE(pac1934_single_channel);
		dev_dbg(dev, ":%s: Channel %d active\n", __func__, cnt + 1);
	}

	dyn_ch_struct = devm_kzalloc(dev, channel_size, GFP_KERNEL);
	if (!dyn_ch_struct)
		return -EINVAL;

	tmp_data = dyn_ch_struct;

	/* populate the dynamic channels and make all the adjustments */
	for (cnt = 0; cnt < info->phys_channels; cnt++) {
		if (!info->active_channels[cnt])
			continue;

		memcpy(tmp_data, pac1934_single_channel, sizeof(pac1934_single_channel));
		ch_sp = (struct iio_chan_spec *)tmp_data;
		ch_sp[PAC1934_CH_ENERGY].channel = cnt + 1;
		ch_sp[PAC1934_CH_ENERGY].scan_index = cnt;
		ch_sp[PAC1934_CH_ENERGY].address = cnt + PAC1934_VPOWER_ACC_1_ADDR;
		ch_sp[PAC1934_CH_POWER].channel = cnt + 1;
		ch_sp[PAC1934_CH_POWER].scan_index = cnt;
		ch_sp[PAC1934_CH_POWER].address = cnt + PAC1934_VPOWER_1_ADDR;
		ch_sp[PAC1934_CH_VOLTAGE].channel = cnt + 1;
		ch_sp[PAC1934_CH_VOLTAGE].scan_index = cnt;
		ch_sp[PAC1934_CH_VOLTAGE].address = cnt + PAC1934_VBUS_1_ADDR;
		ch_sp[PAC1934_CH_CURRENT].channel = cnt + 1;
		ch_sp[PAC1934_CH_CURRENT].scan_index = cnt;
		ch_sp[PAC1934_CH_CURRENT].address = cnt + PAC1934_VSENSE_1_ADDR;

		/*
		 * In order to be able to use labels for PAC1934_CH_VOLTAGE, and
		 * PAC1934_CH_VOLTAGE_AVERAGE,respectively PAC1934_CH_CURRENT
		 * and PAC1934_CH_CURRENT_AVERAGE we need to use different
		 * channel numbers. We will add +5 (+1 to maximum PAC channels).
		 */
		ch_sp[PAC1934_CH_VOLTAGE_AVERAGE].channel = cnt + 5;
		ch_sp[PAC1934_CH_VOLTAGE_AVERAGE].scan_index = cnt;
		ch_sp[PAC1934_CH_VOLTAGE_AVERAGE].address = cnt + PAC1934_VBUS_AVG_1_ADDR;
		ch_sp[PAC1934_CH_CURRENT_AVERAGE].channel = cnt + 5;
		ch_sp[PAC1934_CH_CURRENT_AVERAGE].scan_index = cnt;
		ch_sp[PAC1934_CH_CURRENT_AVERAGE].address = cnt + PAC1934_VSENSE_AVG_1_ADDR;

		/*
		 * now modify the parameters in all channels if the
		 * whole chip rail(channel) is bi-directional
		 */
		if (info->bi_dir[cnt]) {
			ch_sp[PAC1934_CH_ENERGY].scan_type.sign = 's';
			ch_sp[PAC1934_CH_ENERGY].scan_type.realbits = 47;
			ch_sp[PAC1934_CH_POWER].scan_type.sign = 's';
			ch_sp[PAC1934_CH_POWER].scan_type.realbits = 27;
			ch_sp[PAC1934_CH_VOLTAGE].scan_type.sign = 's';
			ch_sp[PAC1934_CH_VOLTAGE].scan_type.realbits = 15;
			ch_sp[PAC1934_CH_CURRENT].scan_type.sign = 's';
			ch_sp[PAC1934_CH_CURRENT].scan_type.realbits = 15;
			ch_sp[PAC1934_CH_VOLTAGE_AVERAGE].scan_type.sign = 's';
			ch_sp[PAC1934_CH_VOLTAGE_AVERAGE].scan_type.realbits = 15;
			ch_sp[PAC1934_CH_CURRENT_AVERAGE].scan_type.sign = 's';
			ch_sp[PAC1934_CH_CURRENT_AVERAGE].scan_type.realbits = 15;
		}
		tmp_data += sizeof(pac1934_single_channel);
	}

	/*
	 * send the updated dynamic channel structure information towards IIO
	 * prepare the required field for IIO class registration
	 */
	indio_dev->num_channels = attribute_count;
	indio_dev->channels = (const struct iio_chan_spec *)dyn_ch_struct;

	return 0;
}

static IIO_DEVICE_ATTR(in_shunt_resistor1, 0644,
		       pac1934_shunt_value_show, pac1934_shunt_value_store, 0);
static IIO_DEVICE_ATTR(in_shunt_resistor2, 0644,
		       pac1934_shunt_value_show, pac1934_shunt_value_store, 1);
static IIO_DEVICE_ATTR(in_shunt_resistor3, 0644,
		       pac1934_shunt_value_show, pac1934_shunt_value_store, 2);
static IIO_DEVICE_ATTR(in_shunt_resistor4, 0644,
		       pac1934_shunt_value_show, pac1934_shunt_value_store, 3);

static int pac1934_prep_custom_attributes(struct pac1934_chip_info *info,
					  struct iio_dev *indio_dev)
{
	int i, active_channels_count = 0;
	struct attribute **pac1934_custom_attr;
	struct attribute_group *pac1934_group;
	struct device *dev = &info->client->dev;

	for (i = 0 ; i < info->phys_channels; i++)
		if (info->active_channels[i])
			active_channels_count++;

	pac1934_group = devm_kzalloc(dev, sizeof(*pac1934_group), GFP_KERNEL);
	if (!pac1934_group)
		return -ENOMEM;

	pac1934_custom_attr = devm_kzalloc(dev,
					   (PAC1934_CUSTOM_ATTR_FOR_CHANNEL *
					   active_channels_count)
					   * sizeof(*pac1934_group) + 1,
					   GFP_KERNEL);
	if (!pac1934_custom_attr)
		return -ENOMEM;

	i = 0;
	if (info->active_channels[0])
		pac1934_custom_attr[i++] = PAC1934_DEV_ATTR(in_shunt_resistor1);

	if (info->active_channels[1])
		pac1934_custom_attr[i++] = PAC1934_DEV_ATTR(in_shunt_resistor2);

	if (info->active_channels[2])
		pac1934_custom_attr[i++] = PAC1934_DEV_ATTR(in_shunt_resistor3);

	if (info->active_channels[3])
		pac1934_custom_attr[i] = PAC1934_DEV_ATTR(in_shunt_resistor4);

	pac1934_group->attrs = pac1934_custom_attr;
	info->iio_info.attrs = pac1934_group;

	return 0;
}

static void pac1934_mutex_destroy(void *data)
{
	struct mutex *lock = data;

	mutex_destroy(lock);
}

static const struct iio_info pac1934_info = {
	.read_raw = pac1934_read_raw,
	.write_raw = pac1934_write_raw,
	.read_avail = pac1934_read_avail,
	.read_label = pac1934_read_label,
};

static int pac1934_probe(struct i2c_client *client)
{
	struct pac1934_chip_info *info;
	const struct pac1934_features *chip;
	struct iio_dev *indio_dev;
	int cnt, ret;
	struct device *dev = &client->dev;

	indio_dev = devm_iio_device_alloc(dev, sizeof(*info));
	if (!indio_dev)
		return -ENOMEM;

	info = iio_priv(indio_dev);

	info->client = client;

	/* always start with energy accumulation enabled */
	for (cnt = 0; cnt < PAC1934_MAX_NUM_CHANNELS; cnt++)
		info->enable_energy[cnt] = true;

	ret = pac1934_chip_identify(info);
	if (ret < 0) {
		/*
		 * If failed to identify the hardware based on internal
		 * registers, try using fallback compatible in device tree
		 * to deal with some newer part number.
		 */
		chip = i2c_get_match_data(client);
		if (!chip)
			return -EINVAL;

		info->phys_channels = chip->phys_channels;
		indio_dev->name = chip->name;
	} else {
		info->phys_channels = pac1934_chip_config[ret].phys_channels;
		indio_dev->name = pac1934_chip_config[ret].name;
	}

	if (acpi_match_device(dev->driver->acpi_match_table, dev))
		ret = pac1934_acpi_parse_channel_config(client, info);
	else
		/*
		 * This makes it possible to use also ACPI PRP0001 for
		 * registering the device using device tree properties.
		 */
		ret = pac1934_fw_parse_channel_config(client, info);

	if (ret)
		return dev_err_probe(dev, ret,
				     "parameter parsing returned an error\n");

	mutex_init(&info->lock);
	ret = devm_add_action_or_reset(dev, pac1934_mutex_destroy,
				       &info->lock);
	if (ret < 0)
		return ret;

	/*
	 * do now any chip specific initialization (e.g. read/write
	 * some registers), enable/disable certain channels, change the sampling
	 * rate to the requested value
	 */
	ret = pac1934_chip_configure(info);
	if (ret < 0)
		return ret;

	/* prepare the channel information */
	ret = pac1934_prep_iio_channels(info, indio_dev);
	if (ret < 0)
		return ret;

	info->iio_info = pac1934_info;
	indio_dev->info = &info->iio_info;
	indio_dev->modes = INDIO_DIRECT_MODE;

	ret = pac1934_prep_custom_attributes(info, indio_dev);
	if (ret < 0)
		return dev_err_probe(dev, ret,
				     "Can't configure custom attributes for PAC1934 device\n");

	/*
	 * read whatever has been accumulated in the chip so far
	 * and reset the accumulators
	 */
	ret = pac1934_reg_snapshot(info, true, PAC1934_REFRESH_REG_ADDR,
				   PAC1934_MIN_UPDATE_WAIT_TIME_US);
	if (ret < 0)
		return ret;

	ret = devm_iio_device_register(dev, indio_dev);
	if (ret < 0)
		return dev_err_probe(dev, ret,
				     "Can't register IIO device\n");

	return 0;
}

static const struct i2c_device_id pac1934_id[] = {
	{ .name = "pac1931", .driver_data = (kernel_ulong_t)&pac1934_chip_config[PAC1931] },
	{ .name = "pac1932", .driver_data = (kernel_ulong_t)&pac1934_chip_config[PAC1932] },
	{ .name = "pac1933", .driver_data = (kernel_ulong_t)&pac1934_chip_config[PAC1933] },
	{ .name = "pac1934", .driver_data = (kernel_ulong_t)&pac1934_chip_config[PAC1934] },
	{}
};
MODULE_DEVICE_TABLE(i2c, pac1934_id);

static const struct of_device_id pac1934_of_match[] = {
	{
		.compatible = "microchip,pac1931",
		.data = &pac1934_chip_config[PAC1931]
	},
	{
		.compatible = "microchip,pac1932",
		.data = &pac1934_chip_config[PAC1932]
	},
	{
		.compatible = "microchip,pac1933",
		.data = &pac1934_chip_config[PAC1933]
	},
	{
		.compatible = "microchip,pac1934",
		.data = &pac1934_chip_config[PAC1934]
	},
	{}
};
MODULE_DEVICE_TABLE(of, pac1934_of_match);

/*
 * using MCHP1930 to be compatible with BIOS ACPI. See example:
 * https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ApplicationNotes/ApplicationNotes/PAC1934-Integration-Notes-for-Microsoft-Windows-10-and-Windows-11-Driver-Support-DS00002534.pdf
 */
static const struct acpi_device_id pac1934_acpi_match[] = {
	{ "MCHP1930", .driver_data = (kernel_ulong_t)&pac1934_chip_config[PAC1934] },
	{}
};
MODULE_DEVICE_TABLE(acpi, pac1934_acpi_match);

static struct i2c_driver pac1934_driver = {
	.driver	 = {
		.name = "pac1934",
		.of_match_table = pac1934_of_match,
		.acpi_match_table = pac1934_acpi_match
	},
	.probe = pac1934_probe,
	.id_table = pac1934_id,
};

module_i2c_driver(pac1934_driver);

MODULE_AUTHOR("Bogdan Bolocan <bogdan.bolocan@microchip.com>");
MODULE_AUTHOR("Victor Tudose");
MODULE_AUTHOR("Marius Cristea <marius.cristea@microchip.com>");
MODULE_DESCRIPTION("IIO driver for PAC1934 Multi-Channel DC Power/Energy Monitor");
MODULE_LICENSE("GPL");