// SPDX-License-Identifier: GPL-2.0+
/*
 * IIO driver for PAC1921 High-Side Power/Current Monitor
 *
 * Copyright (C) 2024 Matteo Martelli <matteomartelli3@gmail.com>
 */

#include <linux/unaligned.h>
#include <linux/bitfield.h>
#include <linux/i2c.h>
#include <linux/iio/events.h>
#include <linux/iio/iio.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/limits.h>
#include <linux/regmap.h>
#include <linux/units.h>

/* pac1921 registers */
#define PAC1921_REG_GAIN_CFG		0x00
#define PAC1921_REG_INT_CFG		0x01
#define PAC1921_REG_CONTROL		0x02
#define PAC1921_REG_VBUS		0x10
#define PAC1921_REG_VSENSE		0x12
#define PAC1921_REG_OVERFLOW_STS	0x1C
#define PAC1921_REG_VPOWER		0x1D

/* pac1921 gain configuration bits */
#define PAC1921_GAIN_DI_GAIN_MASK	GENMASK(5, 3)
#define PAC1921_GAIN_DV_GAIN_MASK	GENMASK(2, 0)

/* pac1921 integration configuration bits */
#define PAC1921_INT_CFG_SMPL_MASK	GENMASK(7, 4)
#define PAC1921_INT_CFG_VSFEN		BIT(3)
#define PAC1921_INT_CFG_VBFEN		BIT(2)
#define PAC1921_INT_CFG_RIOV		BIT(1)
#define PAC1921_INT_CFG_INTEN		BIT(0)

/* pac1921 control bits */
#define PAC1921_CONTROL_MXSL_MASK	GENMASK(7, 6)
enum pac1921_mxsl {
	PAC1921_MXSL_VPOWER_PIN = 0,
	PAC1921_MXSL_VSENSE_FREE_RUN = 1,
	PAC1921_MXSL_VBUS_FREE_RUN = 2,
	PAC1921_MXSL_VPOWER_FREE_RUN = 3,
};
#define PAC1921_CONTROL_SLEEP		BIT(2)

/* pac1921 result registers mask and resolution */
#define PAC1921_RES_MASK		GENMASK(15, 6)
#define PAC1921_RES_RESOLUTION		1023

/* pac1921 overflow status bits */
#define PAC1921_OVERFLOW_VSOV		BIT(2)
#define PAC1921_OVERFLOW_VBOV		BIT(1)
#define PAC1921_OVERFLOW_VPOV		BIT(0)

/* pac1921 constants */
#define PAC1921_MAX_VSENSE_MV		100
#define PAC1921_MAX_VBUS_V		32
/* Time to first communication after power up (tINT_T) */
#define PAC1921_POWERUP_TIME_MS		20
/* Time from Sleep State to Start of Integration Period (tSLEEP_TO_INT) */
#define PAC1921_SLEEP_TO_INT_TIME_US	86

/* pac1921 defaults */
#define PAC1921_DEFAULT_DV_GAIN		0 /* 2^(value): 1x gain (HW default) */
#define PAC1921_DEFAULT_DI_GAIN		0 /* 2^(value): 1x gain (HW default) */
#define PAC1921_DEFAULT_NUM_SAMPLES	0 /* 2^(value): 1 sample (HW default) */

#define PAC1921_ACPI_GET_uOHMS_VALS             0
#define PAC1921_ACPI_GET_LABEL			1

/* f7bb9932-86ee-4516-a236-7a7a742e55cb */
static const guid_t pac1921_guid =
			GUID_INIT(0xf7bb9932, 0x86ee, 0x4516, 0xa2,
				  0x36, 0x7a, 0x7a, 0x74, 0x2e, 0x55, 0xcb);

/*
 * Pre-computed scale factors for BUS voltage
 * format: IIO_VAL_INT_PLUS_NANO
 * unit: mV
 *
 * Vbus scale (mV) = max_vbus (mV) / dv_gain / resolution
 */
static const int pac1921_vbus_scales[][2] = {
	{ 31, 280547409 },	/* dv_gain x1 */
	{ 15, 640273704 },	/* dv_gain x2 */
	{ 7, 820136852 },	/* dv_gain x4 */
	{ 3, 910068426 },	/* dv_gain x8 */
	{ 1, 955034213 },	/* dv_gain x16 */
	{ 0, 977517106 },	/* dv_gain x32 */
};

/*
 * Pre-computed scales for SENSE voltage
 * format: IIO_VAL_INT_PLUS_NANO
 * unit: mV
 *
 * Vsense scale (mV) = max_vsense (mV) / di_gain / resolution
 */
static const int pac1921_vsense_scales[][2] = {
	{ 0, 97751710 },	/* di_gain x1 */
	{ 0, 48875855 },	/* di_gain x2 */
	{ 0, 24437927 },	/* di_gain x4 */
	{ 0, 12218963 },	/* di_gain x8 */
	{ 0, 6109481 },		/* di_gain x16 */
	{ 0, 3054740 },		/* di_gain x32 */
	{ 0, 1527370 },		/* di_gain x64 */
	{ 0, 763685 },		/* di_gain x128 */
};

/*
 * Numbers of samples used to integrate measurements at the end of an
 * integration period.
 *
 * Changing the number of samples affects the integration period: higher the
 * number of samples, longer the integration period.
 *
 * These correspond to the oversampling ratios available exposed to userspace.
 */
static const int pac1921_int_num_samples[] = {
	1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048
};

/*
 * The integration period depends on the configuration of number of integration
 * samples, measurement resolution and post filters. The following array
 * contains integration periods, in microsecs unit, based on table 4-5 from
 * datasheet considering power integration mode, 14-Bit resolution and post
 * filters on. Each index corresponds to a specific number of samples from 1
 * to 2048.
 */
static const unsigned int pac1921_int_periods_usecs[] = {
	2720,		/* 1 sample */
	4050,		/* 2 samples */
	6790,		/* 4 samples */
	12200,		/* 8 samples */
	23000,		/* 16 samples */
	46000,		/* 32 samples */
	92000,		/* 64 samples */
	184000,		/* 128 samples */
	368000,		/* 256 samples */
	736000,		/* 512 samples */
	1471000,	/* 1024 samples */
	2941000		/* 2048 samples */
};

/* pac1921 regmap configuration */
static const struct regmap_range pac1921_regmap_wr_ranges[] = {
	regmap_reg_range(PAC1921_REG_GAIN_CFG, PAC1921_REG_CONTROL),
};

static const struct regmap_access_table pac1921_regmap_wr_table = {
	.yes_ranges = pac1921_regmap_wr_ranges,
	.n_yes_ranges = ARRAY_SIZE(pac1921_regmap_wr_ranges),
};

static const struct regmap_range pac1921_regmap_rd_ranges[] = {
	regmap_reg_range(PAC1921_REG_GAIN_CFG, PAC1921_REG_CONTROL),
	regmap_reg_range(PAC1921_REG_VBUS, PAC1921_REG_VPOWER + 1),
};

static const struct regmap_access_table pac1921_regmap_rd_table = {
	.yes_ranges = pac1921_regmap_rd_ranges,
	.n_yes_ranges = ARRAY_SIZE(pac1921_regmap_rd_ranges),
};

static const struct regmap_config pac1921_regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
	.rd_table = &pac1921_regmap_rd_table,
	.wr_table = &pac1921_regmap_wr_table,
};

enum pac1921_channels {
	PAC1921_CHAN_VBUS = 0,
	PAC1921_CHAN_VSENSE = 1,
	PAC1921_CHAN_CURRENT = 2,
	PAC1921_CHAN_POWER = 3,
};
#define PAC1921_NUM_MEAS_CHANS 4

struct pac1921_priv {
	struct i2c_client *client;
	struct regmap *regmap;
	struct regulator *vdd;
	struct iio_info iio_info;

	/*
	 * Synchronize access to private members, and ensure atomicity of
	 * consecutive regmap operations.
	 */
	struct mutex lock;

	u32 rshunt_uohm; /* uOhm */
	u8 dv_gain;
	u8 di_gain;
	u8 n_samples;
	u8 prev_ovf_flags;
	u8 ovf_enabled_events;

	bool first_integr_started;
	bool first_integr_done;
	unsigned long integr_started_time_jiffies;
	unsigned int integr_period_usecs;

	int current_scales[ARRAY_SIZE(pac1921_vsense_scales)][2];

	struct {
		u16 chan[PAC1921_NUM_MEAS_CHANS];
		aligned_s64 timestamp;
	} scan;
};

/*
 * Check if first integration after configuration update has completed.
 *
 * Must be called with lock held.
 */
static bool pac1921_data_ready(struct pac1921_priv *priv)
{
	if (!priv->first_integr_started)
		return false;

	if (!priv->first_integr_done) {
		unsigned long t_ready;

		/*
		 * Data valid after the device entered into integration state,
		 * considering worst case where the device was in sleep state,
		 * and completed the first integration period.
		 */
		t_ready = priv->integr_started_time_jiffies +
			  usecs_to_jiffies(PAC1921_SLEEP_TO_INT_TIME_US) +
			  usecs_to_jiffies(priv->integr_period_usecs);

		if (time_before(jiffies, t_ready))
			return false;

		priv->first_integr_done = true;
	}

	return true;
}

static inline void pac1921_calc_scale(int dividend, int divisor, int *val,
				      int *val2)
{
	s64 tmp;

	tmp = div_s64(dividend * (s64)NANO, divisor);
	*val = div_s64_rem(tmp, NANO, val2);
}

/*
 * Fill the table of scale factors for current
 * format: IIO_VAL_INT_PLUS_NANO
 * unit: mA
 *
 * Vsense LSB (nV) = max_vsense (nV) * di_gain / resolution
 * Current scale (mA) = Vsense LSB (nV) / shunt (uOhm)
 *
 * Must be called with held lock when updating after first initialization.
 */
static void pac1921_calc_current_scales(struct pac1921_priv *priv)
{
	for (unsigned int i = 0; i < ARRAY_SIZE(priv->current_scales); i++) {
		int max = (PAC1921_MAX_VSENSE_MV * MICRO) >> i;
		int vsense_lsb = DIV_ROUND_CLOSEST(max, PAC1921_RES_RESOLUTION);

		pac1921_calc_scale(vsense_lsb, priv->rshunt_uohm,
				   &priv->current_scales[i][0],
				   &priv->current_scales[i][1]);
	}
}

/*
 * Check if overflow occurred and if so, push the corresponding events.
 *
 * Must be called with lock held.
 */
static int pac1921_check_push_overflow(struct iio_dev *indio_dev, s64 timestamp)
{
	struct pac1921_priv *priv = iio_priv(indio_dev);
	unsigned int flags;
	int ret;

	ret = regmap_read(priv->regmap, PAC1921_REG_OVERFLOW_STS, &flags);
	if (ret)
		return ret;

	if (flags & PAC1921_OVERFLOW_VBOV &&
	    !(priv->prev_ovf_flags & PAC1921_OVERFLOW_VBOV) &&
	    priv->ovf_enabled_events & PAC1921_OVERFLOW_VBOV) {
		iio_push_event(indio_dev,
			       IIO_UNMOD_EVENT_CODE(
				       IIO_VOLTAGE, PAC1921_CHAN_VBUS,
				       IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
			       timestamp);
	}
	if (flags & PAC1921_OVERFLOW_VSOV &&
	    !(priv->prev_ovf_flags & PAC1921_OVERFLOW_VSOV) &&
	    priv->ovf_enabled_events & PAC1921_OVERFLOW_VSOV) {
		iio_push_event(indio_dev,
			       IIO_UNMOD_EVENT_CODE(
				       IIO_VOLTAGE, PAC1921_CHAN_VSENSE,
				       IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
			       timestamp);
		iio_push_event(indio_dev,
			       IIO_UNMOD_EVENT_CODE(
				       IIO_CURRENT, PAC1921_CHAN_CURRENT,
				       IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
			       timestamp);
	}
	if (flags & PAC1921_OVERFLOW_VPOV &&
	    !(priv->prev_ovf_flags & PAC1921_OVERFLOW_VPOV) &&
	    priv->ovf_enabled_events & PAC1921_OVERFLOW_VPOV) {
		iio_push_event(indio_dev,
			       IIO_UNMOD_EVENT_CODE(
				       IIO_POWER, PAC1921_CHAN_POWER,
				       IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
			       timestamp);
	}

	priv->prev_ovf_flags = flags;

	return 0;
}

/*
 * Read the value from a result register
 *
 * Result registers contain the most recent averaged values of Vbus, Vsense and
 * Vpower. Each value is 10 bits wide and spread across two consecutive 8 bit
 * registers, with 6 bit LSB zero padding.
 */
static int pac1921_read_res(struct pac1921_priv *priv, unsigned long reg,
			    u16 *val)
{
	int ret = regmap_bulk_read(priv->regmap, reg, val, sizeof(*val));
	if (ret)
		return ret;

	*val = FIELD_GET(PAC1921_RES_MASK, get_unaligned_be16(val));

	return 0;
}

static int pac1921_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan, int *val,
			    int *val2, long mask)
{
	struct pac1921_priv *priv = iio_priv(indio_dev);

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

	switch (mask) {
	case IIO_CHAN_INFO_RAW: {
		s64 ts;
		u16 res_val;
		int ret;

		if (!pac1921_data_ready(priv))
			return -EBUSY;

		ts = iio_get_time_ns(indio_dev);

		ret = pac1921_check_push_overflow(indio_dev, ts);
		if (ret)
			return ret;

		ret = pac1921_read_res(priv, chan->address, &res_val);
		if (ret)
			return ret;

		*val = res_val;

		return IIO_VAL_INT;
	}
	case IIO_CHAN_INFO_SCALE:
		switch (chan->channel) {
		case PAC1921_CHAN_VBUS:
			*val = pac1921_vbus_scales[priv->dv_gain][0];
			*val2 = pac1921_vbus_scales[priv->dv_gain][1];
			return IIO_VAL_INT_PLUS_NANO;

		case PAC1921_CHAN_VSENSE:
			*val = pac1921_vsense_scales[priv->di_gain][0];
			*val2 = pac1921_vsense_scales[priv->di_gain][1];
			return IIO_VAL_INT_PLUS_NANO;

		case PAC1921_CHAN_CURRENT:
			*val = priv->current_scales[priv->di_gain][0];
			*val2 = priv->current_scales[priv->di_gain][1];
			return IIO_VAL_INT_PLUS_NANO;

		case PAC1921_CHAN_POWER: {
			/*
			 * Power scale factor in mW:
			 * Current scale (mA) * max_vbus (V) / dv_gain
			 */

			/* Get current scale based on di_gain */
			int *curr_scale = priv->current_scales[priv->di_gain];

			/* Convert current_scale from INT_PLUS_NANO to INT */
			s64 tmp = curr_scale[0] * (s64)NANO + curr_scale[1];

			/* Multiply by max_vbus (V) / dv_gain */
			tmp *= PAC1921_MAX_VBUS_V >> priv->dv_gain;

			/* Convert back to INT_PLUS_NANO */
			*val = div_s64_rem(tmp, NANO, val2);

			return IIO_VAL_INT_PLUS_NANO;
		}
		default:
			return -EINVAL;
		}

	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
		*val = pac1921_int_num_samples[priv->n_samples];
		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SAMP_FREQ:
		/*
		 * The sampling frequency (Hz) is read-only and corresponds to
		 * how often the device provides integrated measurements into
		 * the result registers, thus it's 1/integration_period.
		 * The integration period depends on the number of integration
		 * samples, measurement resolution and post filters.
		 *
		 * 1/(integr_period_usecs/MICRO) = MICRO/integr_period_usecs
		 */
		*val = MICRO;
		*val2 = priv->integr_period_usecs;
		return IIO_VAL_FRACTIONAL;

	default:
		return -EINVAL;
	}
}

static int pac1921_read_avail(struct iio_dev *indio_dev,
			      struct iio_chan_spec const *chan,
			      const int **vals, int *type, int *length,
			      long mask)
{
	switch (mask) {
	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
		*type = IIO_VAL_INT;
		*vals = pac1921_int_num_samples;
		*length = ARRAY_SIZE(pac1921_int_num_samples);
		return IIO_AVAIL_LIST;
	default:
		return -EINVAL;
	}
}

/*
 * Perform configuration update sequence: set the device into read state, then
 * write the config register and set the device back into integration state.
 * Also reset integration start time and mark first integration to be yet
 * completed.
 *
 * Must be called with lock held.
 */
static int pac1921_update_cfg_reg(struct pac1921_priv *priv, unsigned int reg,
				  unsigned int mask, unsigned int val)
{
	/* Enter READ state before configuration */
	int ret = regmap_update_bits(priv->regmap, PAC1921_REG_INT_CFG,
				     PAC1921_INT_CFG_INTEN, 0);
	if (ret)
		return ret;

	/* Update configuration value */
	ret = regmap_update_bits(priv->regmap, reg, mask, val);
	if (ret)
		return ret;

	/* Re-enable integration */
	ret = regmap_update_bits(priv->regmap, PAC1921_REG_INT_CFG,
				 PAC1921_INT_CFG_INTEN, PAC1921_INT_CFG_INTEN);
	if (ret)
		return ret;

	/*
	 * Reset integration started time and mark this integration period as
	 * the first one so that new measurements will be considered as valid
	 * only at the end of this integration period.
	 */
	priv->integr_started_time_jiffies = jiffies;
	priv->first_integr_done = false;

	return 0;
}

/*
 * Retrieve the index of the given scale (represented by scale_val and
 * scale_val2) from scales_tbl. The returned index (if found) is the log2 of
 * the gain corresponding to the given scale.
 *
 * Must be called with lock held if the scales_tbl can change runtime (e.g. for
 * the current scales table)
 */
static int pac1921_lookup_scale(const int (*const scales_tbl)[2], size_t size,
				int scale_val, int scale_val2)
{
	for (unsigned int i = 0; i < size; i++)
		if (scales_tbl[i][0] == scale_val &&
		    scales_tbl[i][1] == scale_val2)
			return i;

	return -EINVAL;
}

/*
 * Configure device with the given gain (only if changed)
 *
 * Must be called with lock held.
 */
static int pac1921_update_gain(struct pac1921_priv *priv, u8 *priv_val, u8 gain,
			       unsigned int mask)
{
	unsigned int reg_val;
	int ret;

	if (*priv_val == gain)
		return 0;

	reg_val = (gain << __ffs(mask)) & mask;
	ret = pac1921_update_cfg_reg(priv, PAC1921_REG_GAIN_CFG, mask, reg_val);
	if (ret)
		return ret;

	*priv_val = gain;

	return 0;
}

/*
 * Given a scale factor represented by scale_val and scale_val2 with format
 * IIO_VAL_INT_PLUS_NANO, find the corresponding gain value and write it to the
 * device.
 *
 * Must be called with lock held.
 */
static int pac1921_update_gain_from_scale(struct pac1921_priv *priv,
					  struct iio_chan_spec const *chan,
					  int scale_val, int scale_val2)
{
	int ret;

	switch (chan->channel) {
	case PAC1921_CHAN_VBUS:
		ret = pac1921_lookup_scale(pac1921_vbus_scales,
					   ARRAY_SIZE(pac1921_vbus_scales),
					   scale_val, scale_val2);
		if (ret < 0)
			return ret;

		return pac1921_update_gain(priv, &priv->dv_gain, ret,
					   PAC1921_GAIN_DV_GAIN_MASK);
	case PAC1921_CHAN_VSENSE:
		ret = pac1921_lookup_scale(pac1921_vsense_scales,
					   ARRAY_SIZE(pac1921_vsense_scales),
					   scale_val, scale_val2);
		if (ret < 0)
			return ret;

		return pac1921_update_gain(priv, &priv->di_gain, ret,
					   PAC1921_GAIN_DI_GAIN_MASK);
	case PAC1921_CHAN_CURRENT:
		ret = pac1921_lookup_scale(priv->current_scales,
					   ARRAY_SIZE(priv->current_scales),
					   scale_val, scale_val2);
		if (ret < 0)
			return ret;

		return pac1921_update_gain(priv, &priv->di_gain, ret,
					   PAC1921_GAIN_DI_GAIN_MASK);
	default:
		return -EINVAL;
	}
}

/*
 * Retrieve the index of the given number of samples from the constant table.
 * The returned index (if found) is the log2 of the given num_samples.
 */
static int pac1921_lookup_int_num_samples(int num_samples)
{
	for (unsigned int i = 0; i < ARRAY_SIZE(pac1921_int_num_samples); i++)
		if (pac1921_int_num_samples[i] == num_samples)
			return i;

	return -EINVAL;
}

/*
 * Update the device with the given number of integration samples.
 *
 * Must be called with lock held.
 */
static int pac1921_update_int_num_samples(struct pac1921_priv *priv,
					  int num_samples)
{
	unsigned int reg_val;
	u8 n_samples;
	int ret;

	ret = pac1921_lookup_int_num_samples(num_samples);
	if (ret < 0)
		return ret;

	n_samples = ret;

	if (priv->n_samples == n_samples)
		return 0;

	reg_val = FIELD_PREP(PAC1921_INT_CFG_SMPL_MASK, n_samples);

	ret = pac1921_update_cfg_reg(priv, PAC1921_REG_INT_CFG,
				     PAC1921_INT_CFG_SMPL_MASK, reg_val);
	if (ret)
		return ret;

	priv->n_samples = n_samples;

	priv->integr_period_usecs = pac1921_int_periods_usecs[priv->n_samples];

	return 0;
}

static int pac1921_write_raw_get_fmt(struct iio_dev *indio_dev,
				     struct iio_chan_spec const *chan,
				     long info)
{
	switch (info) {
	case IIO_CHAN_INFO_SCALE:
		return IIO_VAL_INT_PLUS_NANO;
	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
		return IIO_VAL_INT;
	default:
		return -EINVAL;
	}
}

static int pac1921_write_raw(struct iio_dev *indio_dev,
			     struct iio_chan_spec const *chan, int val,
			     int val2, long mask)
{
	struct pac1921_priv *priv = iio_priv(indio_dev);

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

	switch (mask) {
	case IIO_CHAN_INFO_SCALE:
		return pac1921_update_gain_from_scale(priv, chan, val, val2);
	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
		return pac1921_update_int_num_samples(priv, val);
	default:
		return -EINVAL;
	}
}

static int pac1921_read_label(struct iio_dev *indio_dev,
			      struct iio_chan_spec const *chan, char *label)
{
	switch (chan->channel) {
	case PAC1921_CHAN_VBUS:
		return sprintf(label, "vbus\n");
	case PAC1921_CHAN_VSENSE:
		return sprintf(label, "vsense\n");
	case PAC1921_CHAN_CURRENT:
		return sprintf(label, "current\n");
	case PAC1921_CHAN_POWER:
		return sprintf(label, "power\n");
	default:
		return -EINVAL;
	}
}

static int pac1921_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 pac1921_priv *priv = iio_priv(indio_dev);

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

	switch (chan->channel) {
	case PAC1921_CHAN_VBUS:
		return !!(priv->ovf_enabled_events & PAC1921_OVERFLOW_VBOV);
	case PAC1921_CHAN_VSENSE:
	case PAC1921_CHAN_CURRENT:
		return !!(priv->ovf_enabled_events & PAC1921_OVERFLOW_VSOV);
	case PAC1921_CHAN_POWER:
		return !!(priv->ovf_enabled_events & PAC1921_OVERFLOW_VPOV);
	default:
		return -EINVAL;
	}
}

static int pac1921_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 pac1921_priv *priv = iio_priv(indio_dev);
	u8 ovf_bit;

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

	switch (chan->channel) {
	case PAC1921_CHAN_VBUS:
		ovf_bit = PAC1921_OVERFLOW_VBOV;
		break;
	case PAC1921_CHAN_VSENSE:
	case PAC1921_CHAN_CURRENT:
		ovf_bit = PAC1921_OVERFLOW_VSOV;
		break;
	case PAC1921_CHAN_POWER:
		ovf_bit = PAC1921_OVERFLOW_VPOV;
		break;
	default:
		return -EINVAL;
	}

	if (state)
		priv->ovf_enabled_events |= ovf_bit;
	else
		priv->ovf_enabled_events &= ~ovf_bit;

	return 0;
}

static int pac1921_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)
{
	switch (info) {
	case IIO_EV_INFO_VALUE:
		*val = PAC1921_RES_RESOLUTION;
		return IIO_VAL_INT;
	default:
		return -EINVAL;
	}
}

static const struct iio_info pac1921_iio = {
	.read_raw = pac1921_read_raw,
	.read_avail = pac1921_read_avail,
	.write_raw = pac1921_write_raw,
	.write_raw_get_fmt = pac1921_write_raw_get_fmt,
	.read_label = pac1921_read_label,
	.read_event_config = pac1921_read_event_config,
	.write_event_config = pac1921_write_event_config,
	.read_event_value = pac1921_read_event_value,
};

static ssize_t pac1921_read_shunt_resistor(struct iio_dev *indio_dev,
					    uintptr_t private,
					    const struct iio_chan_spec *chan,
					    char *buf)
{
	struct pac1921_priv *priv = iio_priv(indio_dev);
	int vals[2];

	if (chan->channel != PAC1921_CHAN_CURRENT)
		return -EINVAL;

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

	vals[0] = priv->rshunt_uohm;
	vals[1] = MICRO;

	return iio_format_value(buf, IIO_VAL_FRACTIONAL, 1, vals);
}

static ssize_t pac1921_write_shunt_resistor(struct iio_dev *indio_dev,
					    uintptr_t private,
					    const struct iio_chan_spec *chan,
					    const char *buf, size_t len)
{
	struct pac1921_priv *priv = iio_priv(indio_dev);
	u32 rshunt_uohm;
	int val, val_fract;
	int ret;

	if (chan->channel != PAC1921_CHAN_CURRENT)
		return -EINVAL;

	ret = iio_str_to_fixpoint(buf, 100000, &val, &val_fract);
	if (ret)
		return ret;

	/*
	 * This check validates the shunt is not zero and does not surpass
	 * INT_MAX. The check is done before calculating in order to avoid
	 * val * MICRO overflowing.
	 */
	if ((!val && !val_fract) || val > INT_MAX / MICRO ||
	    (val == INT_MAX / MICRO && val_fract > INT_MAX % MICRO))
		return -EINVAL;

	rshunt_uohm = val * MICRO + val_fract;

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

	priv->rshunt_uohm = rshunt_uohm;

	pac1921_calc_current_scales(priv);

	return len;
}

/*
 * Emit on sysfs the list of available scales contained in scales_tbl
 *
 * TODO:: this function can be replaced with iio_format_avail_list() if the
 * latter will ever be exported.
 *
 * Must be called with lock held if the scales_tbl can change runtime (e.g. for
 * the current scales table)
 */
static ssize_t pac1921_format_scale_avail(const int (*const scales_tbl)[2],
					  size_t size, char *buf)
{
	ssize_t len = 0;

	for (unsigned int i = 0; i < size; i++) {
		if (i != 0) {
			len += sysfs_emit_at(buf, len, " ");
			if (len >= PAGE_SIZE)
				return -EFBIG;
		}
		len += sysfs_emit_at(buf, len, "%d.%09d", scales_tbl[i][0],
				     scales_tbl[i][1]);
		if (len >= PAGE_SIZE)
			return -EFBIG;
	}

	len += sysfs_emit_at(buf, len, "\n");
	return len;
}

/*
 * Read available scales for a specific channel
 *
 * NOTE: using extended info insted of iio.read_avail() because access to
 * current scales must be locked as they depend on shunt resistor which may
 * change runtime. Caller of iio.read_avail() would access the table unlocked
 * instead.
 */
static ssize_t pac1921_read_scale_avail(struct iio_dev *indio_dev,
					uintptr_t private,
					const struct iio_chan_spec *chan,
					char *buf)
{
	struct pac1921_priv *priv = iio_priv(indio_dev);
	const int (*scales_tbl)[2];
	size_t size;

	switch (chan->channel) {
	case PAC1921_CHAN_VBUS:
		scales_tbl = pac1921_vbus_scales;
		size = ARRAY_SIZE(pac1921_vbus_scales);
		return pac1921_format_scale_avail(scales_tbl, size, buf);

	case PAC1921_CHAN_VSENSE:
		scales_tbl = pac1921_vsense_scales;
		size = ARRAY_SIZE(pac1921_vsense_scales);
		return pac1921_format_scale_avail(scales_tbl, size, buf);

	case PAC1921_CHAN_CURRENT: {
		guard(mutex)(&priv->lock);
		scales_tbl = priv->current_scales;
		size = ARRAY_SIZE(priv->current_scales);
		return pac1921_format_scale_avail(scales_tbl, size, buf);
	}
	default:
		return -EINVAL;
	}
}

#define PAC1921_EXT_INFO_SCALE_AVAIL {					\
	.name = "scale_available",					\
	.read = pac1921_read_scale_avail,				\
	.shared = IIO_SEPARATE,						\
}

static const struct iio_chan_spec_ext_info pac1921_ext_info_voltage[] = {
	PAC1921_EXT_INFO_SCALE_AVAIL,
	{}
};

static const struct iio_chan_spec_ext_info pac1921_ext_info_current[] = {
	PAC1921_EXT_INFO_SCALE_AVAIL,
	{
		.name = "shunt_resistor",
		.read = pac1921_read_shunt_resistor,
		.write = pac1921_write_shunt_resistor,
		.shared = IIO_SEPARATE,
	},
	{}
};

static const struct iio_event_spec pac1921_overflow_event[] = {
	{
		.type = IIO_EV_TYPE_THRESH,
		.dir = IIO_EV_DIR_RISING,
		.mask_shared_by_all = BIT(IIO_EV_INFO_VALUE),
		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
	},
};

static const struct iio_chan_spec pac1921_channels[] = {
	{
		.type = IIO_VOLTAGE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
				      BIT(IIO_CHAN_INFO_SCALE),
		.info_mask_shared_by_all =
			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
			BIT(IIO_CHAN_INFO_SAMP_FREQ),
		.info_mask_shared_by_all_available =
			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
		.channel = PAC1921_CHAN_VBUS,
		.address = PAC1921_REG_VBUS,
		.scan_index = PAC1921_CHAN_VBUS,
		.scan_type = {
			.sign = 'u',
			.realbits = 10,
			.storagebits = 16,
			.endianness = IIO_CPU
		},
		.indexed = 1,
		.event_spec = pac1921_overflow_event,
		.num_event_specs = ARRAY_SIZE(pac1921_overflow_event),
		.ext_info = pac1921_ext_info_voltage,
	},
	{
		.type = IIO_VOLTAGE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
				      BIT(IIO_CHAN_INFO_SCALE),
		.info_mask_shared_by_all =
			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
			BIT(IIO_CHAN_INFO_SAMP_FREQ),
		.info_mask_shared_by_all_available =
			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
		.channel = PAC1921_CHAN_VSENSE,
		.address = PAC1921_REG_VSENSE,
		.scan_index = PAC1921_CHAN_VSENSE,
		.scan_type = {
			.sign = 'u',
			.realbits = 10,
			.storagebits = 16,
			.endianness = IIO_CPU
		},
		.indexed = 1,
		.event_spec = pac1921_overflow_event,
		.num_event_specs = ARRAY_SIZE(pac1921_overflow_event),
		.ext_info = pac1921_ext_info_voltage,
	},
	{
		.type = IIO_CURRENT,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
				      BIT(IIO_CHAN_INFO_SCALE),
		.info_mask_shared_by_all =
			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
			BIT(IIO_CHAN_INFO_SAMP_FREQ),
		.info_mask_shared_by_all_available =
			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
		.channel = PAC1921_CHAN_CURRENT,
		.address = PAC1921_REG_VSENSE,
		.scan_index = PAC1921_CHAN_CURRENT,
		.scan_type = {
			.sign = 'u',
			.realbits = 10,
			.storagebits = 16,
			.endianness = IIO_CPU
		},
		.event_spec = pac1921_overflow_event,
		.num_event_specs = ARRAY_SIZE(pac1921_overflow_event),
		.ext_info = pac1921_ext_info_current,
	},
	{
		.type = IIO_POWER,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
				      BIT(IIO_CHAN_INFO_SCALE),
		.info_mask_shared_by_all =
			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
			BIT(IIO_CHAN_INFO_SAMP_FREQ),
		.info_mask_shared_by_all_available =
			BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
		.channel = PAC1921_CHAN_POWER,
		.address = PAC1921_REG_VPOWER,
		.scan_index = PAC1921_CHAN_POWER,
		.scan_type = {
			.sign = 'u',
			.realbits = 10,
			.storagebits = 16,
			.endianness = IIO_CPU
		},
		.event_spec = pac1921_overflow_event,
		.num_event_specs = ARRAY_SIZE(pac1921_overflow_event),
	},
	IIO_CHAN_SOFT_TIMESTAMP(PAC1921_NUM_MEAS_CHANS),
};

static irqreturn_t pac1921_trigger_handler(int irq, void *p)
{
	struct iio_poll_func *pf = p;
	struct iio_dev *idev = pf->indio_dev;
	struct pac1921_priv *priv = iio_priv(idev);
	int ret;
	int bit;
	int ch = 0;

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

	if (!pac1921_data_ready(priv))
		goto done;

	ret = pac1921_check_push_overflow(idev, pf->timestamp);
	if (ret)
		goto done;

	iio_for_each_active_channel(idev, bit) {
		u16 val;

		ret = pac1921_read_res(priv, idev->channels[ch].address, &val);
		if (ret)
			goto done;

		priv->scan.chan[ch++] = val;
	}

	iio_push_to_buffers_with_timestamp(idev, &priv->scan, pf->timestamp);

done:
	iio_trigger_notify_done(idev->trig);

	return IRQ_HANDLED;
}

/*
 * Initialize device by writing initial configuration and putting it into
 * integration state.
 *
 * Must be called with lock held when called after first initialization
 * (e.g. from pm resume)
 */
static int pac1921_init(struct pac1921_priv *priv)
{
	unsigned int val;
	int ret;

	/* Enter READ state before configuration */
	ret = regmap_update_bits(priv->regmap, PAC1921_REG_INT_CFG,
				 PAC1921_INT_CFG_INTEN, 0);
	if (ret)
		return ret;

	/* Configure gains, use 14-bits measurement resolution (HW default) */
	val = FIELD_PREP(PAC1921_GAIN_DI_GAIN_MASK, priv->di_gain) |
	      FIELD_PREP(PAC1921_GAIN_DV_GAIN_MASK, priv->dv_gain);
	ret = regmap_write(priv->regmap, PAC1921_REG_GAIN_CFG, val);
	if (ret)
		return ret;

	/*
	 * Configure integration:
	 * - num of integration samples
	 * - filters enabled (HW default)
	 * - set READ/INT pin override (RIOV) to control operation mode via
	 *   register instead of pin
	 */
	val = FIELD_PREP(PAC1921_INT_CFG_SMPL_MASK, priv->n_samples) |
	      PAC1921_INT_CFG_VSFEN | PAC1921_INT_CFG_VBFEN |
	      PAC1921_INT_CFG_RIOV;
	ret = regmap_write(priv->regmap, PAC1921_REG_INT_CFG, val);
	if (ret)
		return ret;

	/*
	 * Init control register:
	 * - VPower free run integration mode
	 * - OUT pin full scale range: 3V (HW default)
	 * - no timeout, no sleep, no sleep override, no recalc (HW defaults)
	 */
	val = FIELD_PREP(PAC1921_CONTROL_MXSL_MASK,
			 PAC1921_MXSL_VPOWER_FREE_RUN);
	ret = regmap_write(priv->regmap, PAC1921_REG_CONTROL, val);
	if (ret)
		return ret;

	/* Enable integration */
	ret = regmap_update_bits(priv->regmap, PAC1921_REG_INT_CFG,
				 PAC1921_INT_CFG_INTEN, PAC1921_INT_CFG_INTEN);
	if (ret)
		return ret;

	priv->first_integr_started = true;
	priv->integr_started_time_jiffies = jiffies;
	priv->integr_period_usecs = pac1921_int_periods_usecs[priv->n_samples];

	return 0;
}

static int pac1921_suspend(struct device *dev)
{
	struct iio_dev *indio_dev = dev_get_drvdata(dev);
	struct pac1921_priv *priv = iio_priv(indio_dev);
	int ret;

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

	priv->first_integr_started = false;
	priv->first_integr_done = false;

	ret = regmap_update_bits(priv->regmap, PAC1921_REG_INT_CFG,
				     PAC1921_INT_CFG_INTEN, 0);
	if (ret)
		return ret;

	ret = regmap_update_bits(priv->regmap, PAC1921_REG_CONTROL,
				 PAC1921_CONTROL_SLEEP, PAC1921_CONTROL_SLEEP);
	if (ret)
		return ret;

	return regulator_disable(priv->vdd);

}

static int pac1921_resume(struct device *dev)
{
	struct iio_dev *indio_dev = dev_get_drvdata(dev);
	struct pac1921_priv *priv = iio_priv(indio_dev);
	int ret;

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

	ret = regulator_enable(priv->vdd);
	if (ret)
		return ret;

	msleep(PAC1921_POWERUP_TIME_MS);

	return pac1921_init(priv);
}

static DEFINE_SIMPLE_DEV_PM_OPS(pac1921_pm_ops, pac1921_suspend,
				pac1921_resume);

static void pac1921_regulator_disable(void *data)
{
	struct regulator *regulator = data;

	regulator_disable(regulator);
}

/*
 * Documentation related to the ACPI device definition
 * https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ApplicationNotes/ApplicationNotes/PAC193X-Integration-Notes-for-Microsoft-Windows-10-and-Windows-11-Driver-Support-DS00002534.pdf
 */
static int pac1921_match_acpi_device(struct iio_dev *indio_dev)
{
	acpi_handle handle;
	union acpi_object *status;
	char *label;
	struct pac1921_priv *priv = iio_priv(indio_dev);
	struct device *dev = &priv->client->dev;

	handle = ACPI_HANDLE(dev);

	status = acpi_evaluate_dsm(handle, &pac1921_guid, 1,
				   PAC1921_ACPI_GET_uOHMS_VALS, NULL);
	if (!status)
		return dev_err_probe(dev, -EINVAL,
				     "Could not read shunt from ACPI table\n");

	priv->rshunt_uohm = status->package.elements[0].integer.value;
	ACPI_FREE(status);

	status = acpi_evaluate_dsm(handle, &pac1921_guid, 1,
				   PAC1921_ACPI_GET_LABEL, NULL);
	if (!status)
		return dev_err_probe(dev, -EINVAL,
				     "Could not read label from ACPI table\n");

	label = devm_kstrdup(dev, status->package.elements[0].string.pointer,
			     GFP_KERNEL);
	if (!label)
		return -ENOMEM;

	indio_dev->label = label;
	ACPI_FREE(status);

	return 0;
}

static int pac1921_parse_of_fw(struct iio_dev *indio_dev)
{
	int ret;
	struct pac1921_priv *priv = iio_priv(indio_dev);
	struct device *dev = &priv->client->dev;

	ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms",
				       &priv->rshunt_uohm);
	if (ret)
		return dev_err_probe(dev, ret,
				     "Cannot read shunt resistor property\n");

	return 0;
}

static int pac1921_probe(struct i2c_client *client)
{
	struct device *dev = &client->dev;
	struct pac1921_priv *priv;
	struct iio_dev *indio_dev;
	int ret;

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

	priv = iio_priv(indio_dev);
	priv->client = client;
	i2c_set_clientdata(client, indio_dev);

	priv->regmap = devm_regmap_init_i2c(client, &pac1921_regmap_config);
	if (IS_ERR(priv->regmap))
		return dev_err_probe(dev, PTR_ERR(priv->regmap),
				     "Cannot initialize register map\n");

	ret = devm_mutex_init(dev, &priv->lock);
	if (ret)
		return ret;

	priv->dv_gain = PAC1921_DEFAULT_DV_GAIN;
	priv->di_gain = PAC1921_DEFAULT_DI_GAIN;
	priv->n_samples = PAC1921_DEFAULT_NUM_SAMPLES;

	if (is_acpi_device_node(dev->fwnode))
		ret = pac1921_match_acpi_device(indio_dev);
	else
		ret = pac1921_parse_of_fw(indio_dev);
	if (ret)
		return dev_err_probe(dev, ret,
				     "Parameter parsing error\n");

	if (priv->rshunt_uohm == 0 || priv->rshunt_uohm > INT_MAX)
		return dev_err_probe(dev, -EINVAL,
				     "Invalid shunt resistor: %u\n",
				     priv->rshunt_uohm);

	pac1921_calc_current_scales(priv);

	priv->vdd = devm_regulator_get(dev, "vdd");
	if (IS_ERR(priv->vdd))
		return dev_err_probe(dev, PTR_ERR(priv->vdd),
				     "Cannot get vdd regulator\n");

	ret = regulator_enable(priv->vdd);
	if (ret)
		return dev_err_probe(dev, ret, "Cannot enable vdd regulator\n");

	ret = devm_add_action_or_reset(dev, pac1921_regulator_disable,
				       priv->vdd);
	if (ret)
		return dev_err_probe(dev, ret,
			"Cannot add action for vdd regulator disposal\n");

	msleep(PAC1921_POWERUP_TIME_MS);

	ret = pac1921_init(priv);
	if (ret)
		return dev_err_probe(dev, ret, "Cannot initialize device\n");

	priv->iio_info = pac1921_iio;

	indio_dev->name = "pac1921";
	indio_dev->info = &priv->iio_info;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = pac1921_channels;
	indio_dev->num_channels = ARRAY_SIZE(pac1921_channels);

	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
					      &iio_pollfunc_store_time,
					      &pac1921_trigger_handler, NULL);
	if (ret)
		return dev_err_probe(dev, ret,
				     "Cannot setup IIO triggered buffer\n");

	ret = devm_iio_device_register(dev, indio_dev);
	if (ret)
		return dev_err_probe(dev, ret, "Cannot register IIO device\n");

	return 0;
}

static const struct i2c_device_id pac1921_id[] = {
	{ .name = "pac1921", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, pac1921_id);

static const struct of_device_id pac1921_of_match[] = {
	{ .compatible = "microchip,pac1921" },
	{ }
};
MODULE_DEVICE_TABLE(of, pac1921_of_match);

static const struct acpi_device_id pac1921_acpi_match[] = {
	{ "MCHP1921" },
	{ }
};
MODULE_DEVICE_TABLE(acpi, pac1921_acpi_match);

static struct i2c_driver pac1921_driver = {
	.driver	 = {
		.name = "pac1921",
		.pm = pm_sleep_ptr(&pac1921_pm_ops),
		.of_match_table = pac1921_of_match,
		.acpi_match_table = pac1921_acpi_match,
	},
	.probe = pac1921_probe,
	.id_table = pac1921_id,
};

module_i2c_driver(pac1921_driver);

MODULE_AUTHOR("Matteo Martelli <matteomartelli3@gmail.com>");
MODULE_DESCRIPTION("IIO driver for PAC1921 High-Side Power/Current Monitor");
MODULE_LICENSE("GPL");