/*
 * Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
 *
 * Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>
 *
 * 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; version 2 of the License.
 *
 * This driver is based on the ds1621 and ina209 drivers.
 *
 * Datasheet:
 * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/jiffies.h>
#include <linux/i2c/ltc4245.h>

/* Here are names of the chip's registers (a.k.a. commands) */
enum ltc4245_cmd {
	LTC4245_STATUS			= 0x00, /* readonly */
	LTC4245_ALERT			= 0x01,
	LTC4245_CONTROL			= 0x02,
	LTC4245_ON			= 0x03,
	LTC4245_FAULT1			= 0x04,
	LTC4245_FAULT2			= 0x05,
	LTC4245_GPIO			= 0x06,
	LTC4245_ADCADR			= 0x07,

	LTC4245_12VIN			= 0x10,
	LTC4245_12VSENSE		= 0x11,
	LTC4245_12VOUT			= 0x12,
	LTC4245_5VIN			= 0x13,
	LTC4245_5VSENSE			= 0x14,
	LTC4245_5VOUT			= 0x15,
	LTC4245_3VIN			= 0x16,
	LTC4245_3VSENSE			= 0x17,
	LTC4245_3VOUT			= 0x18,
	LTC4245_VEEIN			= 0x19,
	LTC4245_VEESENSE		= 0x1a,
	LTC4245_VEEOUT			= 0x1b,
	LTC4245_GPIOADC			= 0x1c,
};

struct ltc4245_data {
	struct i2c_client *client;

	struct mutex update_lock;
	bool valid;
	unsigned long last_updated; /* in jiffies */

	/* Control registers */
	u8 cregs[0x08];

	/* Voltage registers */
	u8 vregs[0x0d];

	/* GPIO ADC registers */
	bool use_extra_gpios;
	int gpios[3];
};

/*
 * Update the readings from the GPIO pins. If the driver has been configured to
 * sample all GPIO's as analog voltages, a round-robin sampling method is used.
 * Otherwise, only the configured GPIO pin is sampled.
 *
 * LOCKING: must hold data->update_lock
 */
static void ltc4245_update_gpios(struct device *dev)
{
	struct ltc4245_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	u8 gpio_curr, gpio_next, gpio_reg;
	int i;

	/* no extra gpio support, we're basically done */
	if (!data->use_extra_gpios) {
		data->gpios[0] = data->vregs[LTC4245_GPIOADC - 0x10];
		return;
	}

	/*
	 * If the last reading was too long ago, then we mark all old GPIO
	 * readings as stale by setting them to -EAGAIN
	 */
	if (time_after(jiffies, data->last_updated + 5 * HZ)) {
		for (i = 0; i < ARRAY_SIZE(data->gpios); i++)
			data->gpios[i] = -EAGAIN;
	}

	/*
	 * Get the current GPIO pin
	 *
	 * The datasheet calls these GPIO[1-3], but we'll calculate the zero
	 * based array index instead, and call them GPIO[0-2]. This is much
	 * easier to think about.
	 */
	gpio_curr = (data->cregs[LTC4245_GPIO] & 0xc0) >> 6;
	if (gpio_curr > 0)
		gpio_curr -= 1;

	/* Read the GPIO voltage from the GPIOADC register */
	data->gpios[gpio_curr] = data->vregs[LTC4245_GPIOADC - 0x10];

	/* Find the next GPIO pin to read */
	gpio_next = (gpio_curr + 1) % ARRAY_SIZE(data->gpios);

	/*
	 * Calculate the correct setting for the GPIO register so it will
	 * sample the next GPIO pin
	 */
	gpio_reg = (data->cregs[LTC4245_GPIO] & 0x3f) | ((gpio_next + 1) << 6);

	/* Update the GPIO register */
	i2c_smbus_write_byte_data(client, LTC4245_GPIO, gpio_reg);

	/* Update saved data */
	data->cregs[LTC4245_GPIO] = gpio_reg;
}

static struct ltc4245_data *ltc4245_update_device(struct device *dev)
{
	struct ltc4245_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	s32 val;
	int i;

	mutex_lock(&data->update_lock);

	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {

		/* Read control registers -- 0x00 to 0x07 */
		for (i = 0; i < ARRAY_SIZE(data->cregs); i++) {
			val = i2c_smbus_read_byte_data(client, i);
			if (unlikely(val < 0))
				data->cregs[i] = 0;
			else
				data->cregs[i] = val;
		}

		/* Read voltage registers -- 0x10 to 0x1c */
		for (i = 0; i < ARRAY_SIZE(data->vregs); i++) {
			val = i2c_smbus_read_byte_data(client, i+0x10);
			if (unlikely(val < 0))
				data->vregs[i] = 0;
			else
				data->vregs[i] = val;
		}

		/* Update GPIO readings */
		ltc4245_update_gpios(dev);

		data->last_updated = jiffies;
		data->valid = true;
	}

	mutex_unlock(&data->update_lock);

	return data;
}

/* Return the voltage from the given register in millivolts */
static int ltc4245_get_voltage(struct device *dev, u8 reg)
{
	struct ltc4245_data *data = ltc4245_update_device(dev);
	const u8 regval = data->vregs[reg - 0x10];
	u32 voltage = 0;

	switch (reg) {
	case LTC4245_12VIN:
	case LTC4245_12VOUT:
		voltage = regval * 55;
		break;
	case LTC4245_5VIN:
	case LTC4245_5VOUT:
		voltage = regval * 22;
		break;
	case LTC4245_3VIN:
	case LTC4245_3VOUT:
		voltage = regval * 15;
		break;
	case LTC4245_VEEIN:
	case LTC4245_VEEOUT:
		voltage = regval * -55;
		break;
	case LTC4245_GPIOADC:
		voltage = regval * 10;
		break;
	default:
		/* If we get here, the developer messed up */
		WARN_ON_ONCE(1);
		break;
	}

	return voltage;
}

/* Return the current in the given sense register in milliAmperes */
static unsigned int ltc4245_get_current(struct device *dev, u8 reg)
{
	struct ltc4245_data *data = ltc4245_update_device(dev);
	const u8 regval = data->vregs[reg - 0x10];
	unsigned int voltage;
	unsigned int curr;

	/*
	 * The strange looking conversions that follow are fixed-point
	 * math, since we cannot do floating point in the kernel.
	 *
	 * Step 1: convert sense register to microVolts
	 * Step 2: convert voltage to milliAmperes
	 *
	 * If you play around with the V=IR equation, you come up with
	 * the following: X uV / Y mOhm == Z mA
	 *
	 * With the resistors that are fractions of a milliOhm, we multiply
	 * the voltage and resistance by 10, to shift the decimal point.
	 * Now we can use the normal division operator again.
	 */

	switch (reg) {
	case LTC4245_12VSENSE:
		voltage = regval * 250; /* voltage in uV */
		curr = voltage / 50; /* sense resistor 50 mOhm */
		break;
	case LTC4245_5VSENSE:
		voltage = regval * 125; /* voltage in uV */
		curr = (voltage * 10) / 35; /* sense resistor 3.5 mOhm */
		break;
	case LTC4245_3VSENSE:
		voltage = regval * 125; /* voltage in uV */
		curr = (voltage * 10) / 25; /* sense resistor 2.5 mOhm */
		break;
	case LTC4245_VEESENSE:
		voltage = regval * 250; /* voltage in uV */
		curr = voltage / 100; /* sense resistor 100 mOhm */
		break;
	default:
		/* If we get here, the developer messed up */
		WARN_ON_ONCE(1);
		curr = 0;
		break;
	}

	return curr;
}

/* Map from voltage channel index to voltage register */

static const s8 ltc4245_in_regs[] = {
	LTC4245_12VIN, LTC4245_5VIN, LTC4245_3VIN, LTC4245_VEEIN,
	LTC4245_12VOUT, LTC4245_5VOUT, LTC4245_3VOUT, LTC4245_VEEOUT,
};

/* Map from current channel index to current register */

static const s8 ltc4245_curr_regs[] = {
	LTC4245_12VSENSE, LTC4245_5VSENSE, LTC4245_3VSENSE, LTC4245_VEESENSE,
};

static int ltc4245_read_curr(struct device *dev, u32 attr, int channel,
			     long *val)
{
	struct ltc4245_data *data = ltc4245_update_device(dev);

	switch (attr) {
	case hwmon_curr_input:
		*val = ltc4245_get_current(dev, ltc4245_curr_regs[channel]);
		return 0;
	case hwmon_curr_max_alarm:
		*val = !!(data->cregs[LTC4245_FAULT1] & BIT(channel + 4));
		return 0;
	default:
		return -EOPNOTSUPP;
	}
}

static int ltc4245_read_in(struct device *dev, u32 attr, int channel, long *val)
{
	struct ltc4245_data *data = ltc4245_update_device(dev);

	switch (attr) {
	case hwmon_in_input:
		if (channel < 8) {
			*val = ltc4245_get_voltage(dev,
						ltc4245_in_regs[channel]);
		} else {
			int regval = data->gpios[channel - 8];

			if (regval < 0)
				return regval;
			*val = regval * 10;
		}
		return 0;
	case hwmon_in_min_alarm:
		if (channel < 4)
			*val = !!(data->cregs[LTC4245_FAULT1] & BIT(channel));
		else
			*val = !!(data->cregs[LTC4245_FAULT2] &
				  BIT(channel - 4));
		return 0;
	default:
		return -EOPNOTSUPP;
	}
}

static int ltc4245_read_power(struct device *dev, u32 attr, int channel,
			      long *val)
{
	unsigned long curr;
	long voltage;

	switch (attr) {
	case hwmon_power_input:
		(void)ltc4245_update_device(dev);
		curr = ltc4245_get_current(dev, ltc4245_curr_regs[channel]);
		voltage = ltc4245_get_voltage(dev, ltc4245_in_regs[channel]);
		*val = abs(curr * voltage);
		return 0;
	default:
		return -EOPNOTSUPP;
	}
}

static int ltc4245_read(struct device *dev, enum hwmon_sensor_types type,
			u32 attr, int channel, long *val)
{

	switch (type) {
	case hwmon_curr:
		return ltc4245_read_curr(dev, attr, channel, val);
	case hwmon_power:
		return ltc4245_read_power(dev, attr, channel, val);
	case hwmon_in:
		return ltc4245_read_in(dev, attr, channel - 1, val);
	default:
		return -EOPNOTSUPP;
	}
}

static umode_t ltc4245_is_visible(const void *_data,
				  enum hwmon_sensor_types type,
				  u32 attr, int channel)
{
	const struct ltc4245_data *data = _data;

	switch (type) {
	case hwmon_in:
		if (channel == 0)
			return 0;
		switch (attr) {
		case hwmon_in_input:
			if (channel > 9 && !data->use_extra_gpios)
				return 0;
			return S_IRUGO;
		case hwmon_in_min_alarm:
			if (channel > 8)
				return 0;
			return S_IRUGO;
		default:
			return 0;
		}
	case hwmon_curr:
		switch (attr) {
		case hwmon_curr_input:
		case hwmon_curr_max_alarm:
			return S_IRUGO;
		default:
			return 0;
		}
	case hwmon_power:
		switch (attr) {
		case hwmon_power_input:
			return S_IRUGO;
		default:
			return 0;
		}
	default:
		return 0;
	}
}

static const u32 ltc4245_in_config[] = {
	HWMON_I_INPUT,			/* dummy, skipped in is_visible */
	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
	HWMON_I_INPUT,
	HWMON_I_INPUT,
	HWMON_I_INPUT,
	0
};

static const struct hwmon_channel_info ltc4245_in = {
	.type = hwmon_in,
	.config = ltc4245_in_config,
};

static const u32 ltc4245_curr_config[] = {
	HWMON_C_INPUT | HWMON_C_MAX_ALARM,
	HWMON_C_INPUT | HWMON_C_MAX_ALARM,
	HWMON_C_INPUT | HWMON_C_MAX_ALARM,
	HWMON_C_INPUT | HWMON_C_MAX_ALARM,
	0
};

static const struct hwmon_channel_info ltc4245_curr = {
	.type = hwmon_curr,
	.config = ltc4245_curr_config,
};

static const u32 ltc4245_power_config[] = {
	HWMON_P_INPUT,
	HWMON_P_INPUT,
	HWMON_P_INPUT,
	HWMON_P_INPUT,
	0
};

static const struct hwmon_channel_info ltc4245_power = {
	.type = hwmon_power,
	.config = ltc4245_power_config,
};

static const struct hwmon_channel_info *ltc4245_info[] = {
	&ltc4245_in,
	&ltc4245_curr,
	&ltc4245_power,
	NULL
};

static const struct hwmon_ops ltc4245_hwmon_ops = {
	.is_visible = ltc4245_is_visible,
	.read = ltc4245_read,
};

static const struct hwmon_chip_info ltc4245_chip_info = {
	.ops = &ltc4245_hwmon_ops,
	.info = ltc4245_info,
};

static bool ltc4245_use_extra_gpios(struct i2c_client *client)
{
	struct ltc4245_platform_data *pdata = dev_get_platdata(&client->dev);
	struct device_node *np = client->dev.of_node;

	/* prefer platform data */
	if (pdata)
		return pdata->use_extra_gpios;

	/* fallback on OF */
	if (of_find_property(np, "ltc4245,use-extra-gpios", NULL))
		return true;

	return false;
}

static int ltc4245_probe(struct i2c_client *client,
			 const struct i2c_device_id *id)
{
	struct i2c_adapter *adapter = client->adapter;
	struct ltc4245_data *data;
	struct device *hwmon_dev;

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
		return -ENODEV;

	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	data->client = client;
	mutex_init(&data->update_lock);
	data->use_extra_gpios = ltc4245_use_extra_gpios(client);

	/* Initialize the LTC4245 chip */
	i2c_smbus_write_byte_data(client, LTC4245_FAULT1, 0x00);
	i2c_smbus_write_byte_data(client, LTC4245_FAULT2, 0x00);

	hwmon_dev = devm_hwmon_device_register_with_info(&client->dev,
							 client->name, data,
							 &ltc4245_chip_info,
							 NULL);
	return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id ltc4245_id[] = {
	{ "ltc4245", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, ltc4245_id);

/* This is the driver that will be inserted */
static struct i2c_driver ltc4245_driver = {
	.driver = {
		.name	= "ltc4245",
	},
	.probe		= ltc4245_probe,
	.id_table	= ltc4245_id,
};

module_i2c_driver(ltc4245_driver);

MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
MODULE_DESCRIPTION("LTC4245 driver");
MODULE_LICENSE("GPL");