/*
 * Gas Gauge driver for SBS Compliant Batteries
 *
 * Copyright (c) 2010, NVIDIA Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */

#include <linux/delay.h>
#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/power/sbs-battery.h>
#include <linux/power_supply.h>
#include <linux/slab.h>
#include <linux/stat.h>

enum {
	REG_MANUFACTURER_DATA,
	REG_TEMPERATURE,
	REG_VOLTAGE,
	REG_CURRENT,
	REG_CAPACITY,
	REG_TIME_TO_EMPTY,
	REG_TIME_TO_FULL,
	REG_STATUS,
	REG_CAPACITY_LEVEL,
	REG_CYCLE_COUNT,
	REG_SERIAL_NUMBER,
	REG_REMAINING_CAPACITY,
	REG_REMAINING_CAPACITY_CHARGE,
	REG_FULL_CHARGE_CAPACITY,
	REG_FULL_CHARGE_CAPACITY_CHARGE,
	REG_DESIGN_CAPACITY,
	REG_DESIGN_CAPACITY_CHARGE,
	REG_DESIGN_VOLTAGE_MIN,
	REG_DESIGN_VOLTAGE_MAX,
	REG_MANUFACTURER,
	REG_MODEL_NAME,
};

/* Battery Mode defines */
#define BATTERY_MODE_OFFSET		0x03
#define BATTERY_MODE_MASK		0x8000
enum sbs_battery_mode {
	BATTERY_MODE_AMPS = 0,
	BATTERY_MODE_WATTS = 0x8000
};

/* manufacturer access defines */
#define MANUFACTURER_ACCESS_STATUS	0x0006
#define MANUFACTURER_ACCESS_SLEEP	0x0011

/* battery status value bits */
#define BATTERY_INITIALIZED		0x80
#define BATTERY_DISCHARGING		0x40
#define BATTERY_FULL_CHARGED		0x20
#define BATTERY_FULL_DISCHARGED		0x10

/* min_value and max_value are only valid for numerical data */
#define SBS_DATA(_psp, _addr, _min_value, _max_value) { \
	.psp = _psp, \
	.addr = _addr, \
	.min_value = _min_value, \
	.max_value = _max_value, \
}

static const struct chip_data {
	enum power_supply_property psp;
	u8 addr;
	int min_value;
	int max_value;
} sbs_data[] = {
	[REG_MANUFACTURER_DATA] =
		SBS_DATA(POWER_SUPPLY_PROP_PRESENT, 0x00, 0, 65535),
	[REG_TEMPERATURE] =
		SBS_DATA(POWER_SUPPLY_PROP_TEMP, 0x08, 0, 65535),
	[REG_VOLTAGE] =
		SBS_DATA(POWER_SUPPLY_PROP_VOLTAGE_NOW, 0x09, 0, 20000),
	[REG_CURRENT] =
		SBS_DATA(POWER_SUPPLY_PROP_CURRENT_NOW, 0x0A, -32768, 32767),
	[REG_CAPACITY] =
		SBS_DATA(POWER_SUPPLY_PROP_CAPACITY, 0x0D, 0, 100),
	[REG_REMAINING_CAPACITY] =
		SBS_DATA(POWER_SUPPLY_PROP_ENERGY_NOW, 0x0F, 0, 65535),
	[REG_REMAINING_CAPACITY_CHARGE] =
		SBS_DATA(POWER_SUPPLY_PROP_CHARGE_NOW, 0x0F, 0, 65535),
	[REG_FULL_CHARGE_CAPACITY] =
		SBS_DATA(POWER_SUPPLY_PROP_ENERGY_FULL, 0x10, 0, 65535),
	[REG_FULL_CHARGE_CAPACITY_CHARGE] =
		SBS_DATA(POWER_SUPPLY_PROP_CHARGE_FULL, 0x10, 0, 65535),
	[REG_TIME_TO_EMPTY] =
		SBS_DATA(POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG, 0x12, 0, 65535),
	[REG_TIME_TO_FULL] =
		SBS_DATA(POWER_SUPPLY_PROP_TIME_TO_FULL_AVG, 0x13, 0, 65535),
	[REG_STATUS] =
		SBS_DATA(POWER_SUPPLY_PROP_STATUS, 0x16, 0, 65535),
	[REG_CAPACITY_LEVEL] =
		SBS_DATA(POWER_SUPPLY_PROP_CAPACITY_LEVEL, 0x16, 0, 65535),
	[REG_CYCLE_COUNT] =
		SBS_DATA(POWER_SUPPLY_PROP_CYCLE_COUNT, 0x17, 0, 65535),
	[REG_DESIGN_CAPACITY] =
		SBS_DATA(POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN, 0x18, 0, 65535),
	[REG_DESIGN_CAPACITY_CHARGE] =
		SBS_DATA(POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN, 0x18, 0, 65535),
	[REG_DESIGN_VOLTAGE_MIN] =
		SBS_DATA(POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN, 0x19, 0, 65535),
	[REG_DESIGN_VOLTAGE_MAX] =
		SBS_DATA(POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN, 0x19, 0, 65535),
	[REG_SERIAL_NUMBER] =
		SBS_DATA(POWER_SUPPLY_PROP_SERIAL_NUMBER, 0x1C, 0, 65535),
	/* Properties of type `const char *' */
	[REG_MANUFACTURER] =
		SBS_DATA(POWER_SUPPLY_PROP_MANUFACTURER, 0x20, 0, 65535),
	[REG_MODEL_NAME] =
		SBS_DATA(POWER_SUPPLY_PROP_MODEL_NAME, 0x21, 0, 65535)
};

static enum power_supply_property sbs_properties[] = {
	POWER_SUPPLY_PROP_STATUS,
	POWER_SUPPLY_PROP_CAPACITY_LEVEL,
	POWER_SUPPLY_PROP_HEALTH,
	POWER_SUPPLY_PROP_PRESENT,
	POWER_SUPPLY_PROP_TECHNOLOGY,
	POWER_SUPPLY_PROP_CYCLE_COUNT,
	POWER_SUPPLY_PROP_VOLTAGE_NOW,
	POWER_SUPPLY_PROP_CURRENT_NOW,
	POWER_SUPPLY_PROP_CAPACITY,
	POWER_SUPPLY_PROP_TEMP,
	POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG,
	POWER_SUPPLY_PROP_TIME_TO_FULL_AVG,
	POWER_SUPPLY_PROP_SERIAL_NUMBER,
	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
	POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
	POWER_SUPPLY_PROP_ENERGY_NOW,
	POWER_SUPPLY_PROP_ENERGY_FULL,
	POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN,
	POWER_SUPPLY_PROP_CHARGE_NOW,
	POWER_SUPPLY_PROP_CHARGE_FULL,
	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
	/* Properties of type `const char *' */
	POWER_SUPPLY_PROP_MANUFACTURER,
	POWER_SUPPLY_PROP_MODEL_NAME
};

struct sbs_info {
	struct i2c_client		*client;
	struct power_supply		*power_supply;
	bool				is_present;
	struct gpio_desc		*gpio_detect;
	bool				enable_detection;
	int				last_state;
	int				poll_time;
	u32				i2c_retry_count;
	u32				poll_retry_count;
	struct delayed_work		work;
	struct mutex			mode_lock;
};

static char model_name[I2C_SMBUS_BLOCK_MAX + 1];
static char manufacturer[I2C_SMBUS_BLOCK_MAX + 1];
static bool force_load;

static int sbs_read_word_data(struct i2c_client *client, u8 address)
{
	struct sbs_info *chip = i2c_get_clientdata(client);
	int retries = chip->i2c_retry_count;
	s32 ret = 0;

	while (retries > 0) {
		ret = i2c_smbus_read_word_data(client, address);
		if (ret >= 0)
			break;
		retries--;
	}

	if (ret < 0) {
		dev_dbg(&client->dev,
			"%s: i2c read at address 0x%x failed\n",
			__func__, address);
		return ret;
	}

	return ret;
}

static int sbs_read_string_data(struct i2c_client *client, u8 address,
				char *values)
{
	struct sbs_info *chip = i2c_get_clientdata(client);
	s32 ret = 0, block_length = 0;
	int retries_length, retries_block;
	u8 block_buffer[I2C_SMBUS_BLOCK_MAX + 1];

	retries_length = chip->i2c_retry_count;
	retries_block = chip->i2c_retry_count;

	/* Adapter needs to support these two functions */
	if (!i2c_check_functionality(client->adapter,
				     I2C_FUNC_SMBUS_BYTE_DATA |
				     I2C_FUNC_SMBUS_I2C_BLOCK)){
		return -ENODEV;
	}

	/* Get the length of block data */
	while (retries_length > 0) {
		ret = i2c_smbus_read_byte_data(client, address);
		if (ret >= 0)
			break;
		retries_length--;
	}

	if (ret < 0) {
		dev_dbg(&client->dev,
			"%s: i2c read at address 0x%x failed\n",
			__func__, address);
		return ret;
	}

	/* block_length does not include NULL terminator */
	block_length = ret;
	if (block_length > I2C_SMBUS_BLOCK_MAX) {
		dev_err(&client->dev,
			"%s: Returned block_length is longer than 0x%x\n",
			__func__, I2C_SMBUS_BLOCK_MAX);
		return -EINVAL;
	}

	/* Get the block data */
	while (retries_block > 0) {
		ret = i2c_smbus_read_i2c_block_data(
				client, address,
				block_length + 1, block_buffer);
		if (ret >= 0)
			break;
		retries_block--;
	}

	if (ret < 0) {
		dev_dbg(&client->dev,
			"%s: i2c read at address 0x%x failed\n",
			__func__, address);
		return ret;
	}

	/* block_buffer[0] == block_length */
	memcpy(values, block_buffer + 1, block_length);
	values[block_length] = '\0';

	return ret;
}

static int sbs_write_word_data(struct i2c_client *client, u8 address,
	u16 value)
{
	struct sbs_info *chip = i2c_get_clientdata(client);
	int retries = chip->i2c_retry_count;
	s32 ret = 0;

	while (retries > 0) {
		ret = i2c_smbus_write_word_data(client, address, value);
		if (ret >= 0)
			break;
		retries--;
	}

	if (ret < 0) {
		dev_dbg(&client->dev,
			"%s: i2c write to address 0x%x failed\n",
			__func__, address);
		return ret;
	}

	return 0;
}

static int sbs_status_correct(struct i2c_client *client, int *intval)
{
	int ret;

	ret = sbs_read_word_data(client, sbs_data[REG_CURRENT].addr);
	if (ret < 0)
		return ret;

	ret = (s16)ret;

	/* Not drawing current means full (cannot be not charging) */
	if (ret == 0)
		*intval = POWER_SUPPLY_STATUS_FULL;

	if (*intval == POWER_SUPPLY_STATUS_FULL) {
		/* Drawing or providing current when full */
		if (ret > 0)
			*intval = POWER_SUPPLY_STATUS_CHARGING;
		else if (ret < 0)
			*intval = POWER_SUPPLY_STATUS_DISCHARGING;
	}

	return 0;
}

static int sbs_get_battery_presence_and_health(
	struct i2c_client *client, enum power_supply_property psp,
	union power_supply_propval *val)
{
	s32 ret;

	/*
	 * Write to ManufacturerAccess with ManufacturerAccess command
	 * and then read the status. Do not check for error on the write
	 * since not all batteries implement write access to this command,
	 * while others mandate it.
	 */
	sbs_write_word_data(client, sbs_data[REG_MANUFACTURER_DATA].addr,
			    MANUFACTURER_ACCESS_STATUS);

	ret = sbs_read_word_data(client, sbs_data[REG_MANUFACTURER_DATA].addr);
	if (ret < 0) {
		if (psp == POWER_SUPPLY_PROP_PRESENT)
			val->intval = 0; /* battery removed */
		return ret;
	}

	if (ret < sbs_data[REG_MANUFACTURER_DATA].min_value ||
	    ret > sbs_data[REG_MANUFACTURER_DATA].max_value) {
		val->intval = 0;
		return 0;
	}

	/* Mask the upper nibble of 2nd byte and
	 * lower byte of response then
	 * shift the result by 8 to get status*/
	ret &= 0x0F00;
	ret >>= 8;
	if (psp == POWER_SUPPLY_PROP_PRESENT) {
		if (ret == 0x0F)
			/* battery removed */
			val->intval = 0;
		else
			val->intval = 1;
	} else if (psp == POWER_SUPPLY_PROP_HEALTH) {
		if (ret == 0x09)
			val->intval = POWER_SUPPLY_HEALTH_UNSPEC_FAILURE;
		else if (ret == 0x0B)
			val->intval = POWER_SUPPLY_HEALTH_OVERHEAT;
		else if (ret == 0x0C)
			val->intval = POWER_SUPPLY_HEALTH_DEAD;
		else
			val->intval = POWER_SUPPLY_HEALTH_GOOD;
	}

	return 0;
}

static int sbs_get_battery_property(struct i2c_client *client,
	int reg_offset, enum power_supply_property psp,
	union power_supply_propval *val)
{
	struct sbs_info *chip = i2c_get_clientdata(client);
	s32 ret;

	ret = sbs_read_word_data(client, sbs_data[reg_offset].addr);
	if (ret < 0)
		return ret;

	/* returned values are 16 bit */
	if (sbs_data[reg_offset].min_value < 0)
		ret = (s16)ret;

	if (ret >= sbs_data[reg_offset].min_value &&
	    ret <= sbs_data[reg_offset].max_value) {
		val->intval = ret;
		if (psp == POWER_SUPPLY_PROP_CAPACITY_LEVEL) {
			if (!(ret & BATTERY_INITIALIZED))
				val->intval =
					POWER_SUPPLY_CAPACITY_LEVEL_UNKNOWN;
			else if (ret & BATTERY_FULL_CHARGED)
				val->intval =
					POWER_SUPPLY_CAPACITY_LEVEL_FULL;
			else if (ret & BATTERY_FULL_DISCHARGED)
				val->intval =
					POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
			else
				val->intval =
					POWER_SUPPLY_CAPACITY_LEVEL_NORMAL;
			return 0;
		} else if (psp != POWER_SUPPLY_PROP_STATUS) {
			return 0;
		}

		if (ret & BATTERY_FULL_CHARGED)
			val->intval = POWER_SUPPLY_STATUS_FULL;
		else if (ret & BATTERY_DISCHARGING)
			val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
		else
			val->intval = POWER_SUPPLY_STATUS_CHARGING;

		sbs_status_correct(client, &val->intval);

		if (chip->poll_time == 0)
			chip->last_state = val->intval;
		else if (chip->last_state != val->intval) {
			cancel_delayed_work_sync(&chip->work);
			power_supply_changed(chip->power_supply);
			chip->poll_time = 0;
		}
	} else {
		if (psp == POWER_SUPPLY_PROP_STATUS)
			val->intval = POWER_SUPPLY_STATUS_UNKNOWN;
		else if (psp == POWER_SUPPLY_PROP_CAPACITY)
			/* sbs spec says that this can be >100 %
			 * even if max value is 100 %
			 */
			val->intval = min(ret, 100);
		else
			val->intval = 0;
	}

	return 0;
}

static int sbs_get_battery_string_property(struct i2c_client *client,
	int reg_offset, enum power_supply_property psp, char *val)
{
	s32 ret;

	ret = sbs_read_string_data(client, sbs_data[reg_offset].addr, val);

	if (ret < 0)
		return ret;

	return 0;
}

static void  sbs_unit_adjustment(struct i2c_client *client,
	enum power_supply_property psp, union power_supply_propval *val)
{
#define BASE_UNIT_CONVERSION		1000
#define BATTERY_MODE_CAP_MULT_WATT	(10 * BASE_UNIT_CONVERSION)
#define TIME_UNIT_CONVERSION		60
#define TEMP_KELVIN_TO_CELSIUS		2731
	switch (psp) {
	case POWER_SUPPLY_PROP_ENERGY_NOW:
	case POWER_SUPPLY_PROP_ENERGY_FULL:
	case POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN:
		/* sbs provides energy in units of 10mWh.
		 * Convert to µWh
		 */
		val->intval *= BATTERY_MODE_CAP_MULT_WATT;
		break;

	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
	case POWER_SUPPLY_PROP_CURRENT_NOW:
	case POWER_SUPPLY_PROP_CHARGE_NOW:
	case POWER_SUPPLY_PROP_CHARGE_FULL:
	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
		val->intval *= BASE_UNIT_CONVERSION;
		break;

	case POWER_SUPPLY_PROP_TEMP:
		/* sbs provides battery temperature in 0.1K
		 * so convert it to 0.1°C
		 */
		val->intval -= TEMP_KELVIN_TO_CELSIUS;
		break;

	case POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG:
	case POWER_SUPPLY_PROP_TIME_TO_FULL_AVG:
		/* sbs provides time to empty and time to full in minutes.
		 * Convert to seconds
		 */
		val->intval *= TIME_UNIT_CONVERSION;
		break;

	default:
		dev_dbg(&client->dev,
			"%s: no need for unit conversion %d\n", __func__, psp);
	}
}

static enum sbs_battery_mode sbs_set_battery_mode(struct i2c_client *client,
	enum sbs_battery_mode mode)
{
	int ret, original_val;

	original_val = sbs_read_word_data(client, BATTERY_MODE_OFFSET);
	if (original_val < 0)
		return original_val;

	if ((original_val & BATTERY_MODE_MASK) == mode)
		return mode;

	if (mode == BATTERY_MODE_AMPS)
		ret = original_val & ~BATTERY_MODE_MASK;
	else
		ret = original_val | BATTERY_MODE_MASK;

	ret = sbs_write_word_data(client, BATTERY_MODE_OFFSET, ret);
	if (ret < 0)
		return ret;

	usleep_range(1000, 2000);

	return original_val & BATTERY_MODE_MASK;
}

static int sbs_get_battery_capacity(struct i2c_client *client,
	int reg_offset, enum power_supply_property psp,
	union power_supply_propval *val)
{
	s32 ret;
	enum sbs_battery_mode mode = BATTERY_MODE_WATTS;

	if (power_supply_is_amp_property(psp))
		mode = BATTERY_MODE_AMPS;

	mode = sbs_set_battery_mode(client, mode);
	if (mode < 0)
		return mode;

	ret = sbs_read_word_data(client, sbs_data[reg_offset].addr);
	if (ret < 0)
		return ret;

	val->intval = ret;

	ret = sbs_set_battery_mode(client, mode);
	if (ret < 0)
		return ret;

	return 0;
}

static char sbs_serial[5];
static int sbs_get_battery_serial_number(struct i2c_client *client,
	union power_supply_propval *val)
{
	int ret;

	ret = sbs_read_word_data(client, sbs_data[REG_SERIAL_NUMBER].addr);
	if (ret < 0)
		return ret;

	sprintf(sbs_serial, "%04x", ret);
	val->strval = sbs_serial;

	return 0;
}

static int sbs_get_property_index(struct i2c_client *client,
	enum power_supply_property psp)
{
	int count;
	for (count = 0; count < ARRAY_SIZE(sbs_data); count++)
		if (psp == sbs_data[count].psp)
			return count;

	dev_warn(&client->dev,
		"%s: Invalid Property - %d\n", __func__, psp);

	return -EINVAL;
}

static int sbs_get_property(struct power_supply *psy,
	enum power_supply_property psp,
	union power_supply_propval *val)
{
	int ret = 0;
	struct sbs_info *chip = power_supply_get_drvdata(psy);
	struct i2c_client *client = chip->client;

	if (chip->gpio_detect) {
		ret = gpiod_get_value_cansleep(chip->gpio_detect);
		if (ret < 0)
			return ret;
		if (psp == POWER_SUPPLY_PROP_PRESENT) {
			val->intval = ret;
			chip->is_present = val->intval;
			return 0;
		}
		if (ret == 0)
			return -ENODATA;
	}

	switch (psp) {
	case POWER_SUPPLY_PROP_PRESENT:
	case POWER_SUPPLY_PROP_HEALTH:
		ret = sbs_get_battery_presence_and_health(client, psp, val);
		if (psp == POWER_SUPPLY_PROP_PRESENT)
			return 0;
		break;

	case POWER_SUPPLY_PROP_TECHNOLOGY:
		val->intval = POWER_SUPPLY_TECHNOLOGY_LION;
		goto done; /* don't trigger power_supply_changed()! */

	case POWER_SUPPLY_PROP_ENERGY_NOW:
	case POWER_SUPPLY_PROP_ENERGY_FULL:
	case POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN:
	case POWER_SUPPLY_PROP_CHARGE_NOW:
	case POWER_SUPPLY_PROP_CHARGE_FULL:
	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
		ret = sbs_get_property_index(client, psp);
		if (ret < 0)
			break;

		/* sbs_get_battery_capacity() will change the battery mode
		 * temporarily to read the requested attribute. Ensure we stay
		 * in the desired mode for the duration of the attribute read.
		 */
		mutex_lock(&chip->mode_lock);
		ret = sbs_get_battery_capacity(client, ret, psp, val);
		mutex_unlock(&chip->mode_lock);
		break;

	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
		ret = sbs_get_battery_serial_number(client, val);
		break;

	case POWER_SUPPLY_PROP_STATUS:
	case POWER_SUPPLY_PROP_CAPACITY_LEVEL:
	case POWER_SUPPLY_PROP_CYCLE_COUNT:
	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
	case POWER_SUPPLY_PROP_CURRENT_NOW:
	case POWER_SUPPLY_PROP_TEMP:
	case POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG:
	case POWER_SUPPLY_PROP_TIME_TO_FULL_AVG:
	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
	case POWER_SUPPLY_PROP_CAPACITY:
		ret = sbs_get_property_index(client, psp);
		if (ret < 0)
			break;

		ret = sbs_get_battery_property(client, ret, psp, val);
		break;

	case POWER_SUPPLY_PROP_MODEL_NAME:
		ret = sbs_get_property_index(client, psp);
		if (ret < 0)
			break;

		ret = sbs_get_battery_string_property(client, ret, psp,
						      model_name);
		val->strval = model_name;
		break;

	case POWER_SUPPLY_PROP_MANUFACTURER:
		ret = sbs_get_property_index(client, psp);
		if (ret < 0)
			break;

		ret = sbs_get_battery_string_property(client, ret, psp,
						      manufacturer);
		val->strval = manufacturer;
		break;

	default:
		dev_err(&client->dev,
			"%s: INVALID property\n", __func__);
		return -EINVAL;
	}

	if (!chip->enable_detection)
		goto done;

	if (!chip->gpio_detect &&
		chip->is_present != (ret >= 0)) {
		chip->is_present = (ret >= 0);
		power_supply_changed(chip->power_supply);
	}

done:
	if (!ret) {
		/* Convert units to match requirements for power supply class */
		sbs_unit_adjustment(client, psp, val);
	}

	dev_dbg(&client->dev,
		"%s: property = %d, value = %x\n", __func__, psp, val->intval);

	if (ret && chip->is_present)
		return ret;

	/* battery not present, so return NODATA for properties */
	if (ret)
		return -ENODATA;

	return 0;
}

static void sbs_supply_changed(struct sbs_info *chip)
{
	struct power_supply *battery = chip->power_supply;
	int ret;

	ret = gpiod_get_value_cansleep(chip->gpio_detect);
	if (ret < 0)
		return;
	chip->is_present = ret;
	power_supply_changed(battery);
}

static irqreturn_t sbs_irq(int irq, void *devid)
{
	sbs_supply_changed(devid);
	return IRQ_HANDLED;
}

static void sbs_alert(struct i2c_client *client, enum i2c_alert_protocol prot,
	unsigned int data)
{
	sbs_supply_changed(i2c_get_clientdata(client));
}

static void sbs_external_power_changed(struct power_supply *psy)
{
	struct sbs_info *chip = power_supply_get_drvdata(psy);

	/* cancel outstanding work */
	cancel_delayed_work_sync(&chip->work);

	schedule_delayed_work(&chip->work, HZ);
	chip->poll_time = chip->poll_retry_count;
}

static void sbs_delayed_work(struct work_struct *work)
{
	struct sbs_info *chip;
	s32 ret;

	chip = container_of(work, struct sbs_info, work.work);

	ret = sbs_read_word_data(chip->client, sbs_data[REG_STATUS].addr);
	/* if the read failed, give up on this work */
	if (ret < 0) {
		chip->poll_time = 0;
		return;
	}

	if (ret & BATTERY_FULL_CHARGED)
		ret = POWER_SUPPLY_STATUS_FULL;
	else if (ret & BATTERY_DISCHARGING)
		ret = POWER_SUPPLY_STATUS_DISCHARGING;
	else
		ret = POWER_SUPPLY_STATUS_CHARGING;

	sbs_status_correct(chip->client, &ret);

	if (chip->last_state != ret) {
		chip->poll_time = 0;
		power_supply_changed(chip->power_supply);
		return;
	}
	if (chip->poll_time > 0) {
		schedule_delayed_work(&chip->work, HZ);
		chip->poll_time--;
		return;
	}
}

static const struct power_supply_desc sbs_default_desc = {
	.type = POWER_SUPPLY_TYPE_BATTERY,
	.properties = sbs_properties,
	.num_properties = ARRAY_SIZE(sbs_properties),
	.get_property = sbs_get_property,
	.external_power_changed = sbs_external_power_changed,
};

static int sbs_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
{
	struct sbs_info *chip;
	struct power_supply_desc *sbs_desc;
	struct sbs_platform_data *pdata = client->dev.platform_data;
	struct power_supply_config psy_cfg = {};
	int rc;
	int irq;

	sbs_desc = devm_kmemdup(&client->dev, &sbs_default_desc,
			sizeof(*sbs_desc), GFP_KERNEL);
	if (!sbs_desc)
		return -ENOMEM;

	sbs_desc->name = devm_kasprintf(&client->dev, GFP_KERNEL, "sbs-%s",
			dev_name(&client->dev));
	if (!sbs_desc->name)
		return -ENOMEM;

	chip = devm_kzalloc(&client->dev, sizeof(struct sbs_info), GFP_KERNEL);
	if (!chip)
		return -ENOMEM;

	chip->client = client;
	chip->enable_detection = false;
	psy_cfg.of_node = client->dev.of_node;
	psy_cfg.drv_data = chip;
	chip->last_state = POWER_SUPPLY_STATUS_UNKNOWN;
	mutex_init(&chip->mode_lock);

	/* use pdata if available, fall back to DT properties,
	 * or hardcoded defaults if not
	 */
	rc = of_property_read_u32(client->dev.of_node, "sbs,i2c-retry-count",
				  &chip->i2c_retry_count);
	if (rc)
		chip->i2c_retry_count = 0;

	rc = of_property_read_u32(client->dev.of_node, "sbs,poll-retry-count",
				  &chip->poll_retry_count);
	if (rc)
		chip->poll_retry_count = 0;

	if (pdata) {
		chip->poll_retry_count = pdata->poll_retry_count;
		chip->i2c_retry_count  = pdata->i2c_retry_count;
	}
	chip->i2c_retry_count = chip->i2c_retry_count + 1;

	chip->gpio_detect = devm_gpiod_get_optional(&client->dev,
			"sbs,battery-detect", GPIOD_IN);
	if (IS_ERR(chip->gpio_detect)) {
		dev_err(&client->dev, "Failed to get gpio: %ld\n",
			PTR_ERR(chip->gpio_detect));
		return PTR_ERR(chip->gpio_detect);
	}

	i2c_set_clientdata(client, chip);

	if (!chip->gpio_detect)
		goto skip_gpio;

	irq = gpiod_to_irq(chip->gpio_detect);
	if (irq <= 0) {
		dev_warn(&client->dev, "Failed to get gpio as irq: %d\n", irq);
		goto skip_gpio;
	}

	rc = devm_request_threaded_irq(&client->dev, irq, NULL, sbs_irq,
		IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
		dev_name(&client->dev), chip);
	if (rc) {
		dev_warn(&client->dev, "Failed to request irq: %d\n", rc);
		goto skip_gpio;
	}

skip_gpio:
	/*
	 * Before we register, we might need to make sure we can actually talk
	 * to the battery.
	 */
	if (!(force_load || chip->gpio_detect)) {
		rc = sbs_read_word_data(client, sbs_data[REG_STATUS].addr);

		if (rc < 0) {
			dev_err(&client->dev, "%s: Failed to get device status\n",
				__func__);
			goto exit_psupply;
		}
	}

	chip->power_supply = devm_power_supply_register(&client->dev, sbs_desc,
						   &psy_cfg);
	if (IS_ERR(chip->power_supply)) {
		dev_err(&client->dev,
			"%s: Failed to register power supply\n", __func__);
		rc = PTR_ERR(chip->power_supply);
		goto exit_psupply;
	}

	dev_info(&client->dev,
		"%s: battery gas gauge device registered\n", client->name);

	INIT_DELAYED_WORK(&chip->work, sbs_delayed_work);

	chip->enable_detection = true;

	return 0;

exit_psupply:
	return rc;
}

static int sbs_remove(struct i2c_client *client)
{
	struct sbs_info *chip = i2c_get_clientdata(client);

	cancel_delayed_work_sync(&chip->work);

	return 0;
}

#if defined CONFIG_PM_SLEEP

static int sbs_suspend(struct device *dev)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct sbs_info *chip = i2c_get_clientdata(client);

	if (chip->poll_time > 0)
		cancel_delayed_work_sync(&chip->work);

	/*
	 * Write to manufacturer access with sleep command.
	 * Support is manufacturer dependend, so ignore errors.
	 */
	sbs_write_word_data(client, sbs_data[REG_MANUFACTURER_DATA].addr,
		MANUFACTURER_ACCESS_SLEEP);

	return 0;
}

static SIMPLE_DEV_PM_OPS(sbs_pm_ops, sbs_suspend, NULL);
#define SBS_PM_OPS (&sbs_pm_ops)

#else
#define SBS_PM_OPS NULL
#endif

static const struct i2c_device_id sbs_id[] = {
	{ "bq20z75", 0 },
	{ "sbs-battery", 1 },
	{}
};
MODULE_DEVICE_TABLE(i2c, sbs_id);

static const struct of_device_id sbs_dt_ids[] = {
	{ .compatible = "sbs,sbs-battery" },
	{ .compatible = "ti,bq20z75" },
	{ }
};
MODULE_DEVICE_TABLE(of, sbs_dt_ids);

static struct i2c_driver sbs_battery_driver = {
	.probe		= sbs_probe,
	.remove		= sbs_remove,
	.alert		= sbs_alert,
	.id_table	= sbs_id,
	.driver = {
		.name	= "sbs-battery",
		.of_match_table = sbs_dt_ids,
		.pm	= SBS_PM_OPS,
	},
};
module_i2c_driver(sbs_battery_driver);

MODULE_DESCRIPTION("SBS battery monitor driver");
MODULE_LICENSE("GPL");

module_param(force_load, bool, S_IRUSR | S_IRGRP | S_IROTH);
MODULE_PARM_DESC(force_load,
		 "Attempt to load the driver even if no battery is connected");