/*
 * Copyright (C) 2017 IBM Corp.
 *
 * 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.
 *
 * Driver for the Nuvoton W83773G SMBus temperature sensor IC.
 * Supported models: W83773G
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/of_device.h>
#include <linux/regmap.h>

/* W83773 has 3 channels */
#define W83773_CHANNELS				3

/* The W83773 registers */
#define W83773_CONVERSION_RATE_REG_READ		0x04
#define W83773_CONVERSION_RATE_REG_WRITE	0x0A
#define W83773_MANUFACTURER_ID_REG		0xFE
#define W83773_LOCAL_TEMP			0x00

static const u8 W83773_STATUS[2] = { 0x02, 0x17 };

static const u8 W83773_TEMP_LSB[2] = { 0x10, 0x25 };
static const u8 W83773_TEMP_MSB[2] = { 0x01, 0x24 };

static const u8 W83773_OFFSET_LSB[2] = { 0x12, 0x16 };
static const u8 W83773_OFFSET_MSB[2] = { 0x11, 0x15 };

/* this is the number of sensors in the device */
static const struct i2c_device_id w83773_id[] = {
	{ "w83773g" },
	{ }
};

MODULE_DEVICE_TABLE(i2c, w83773_id);

static const struct of_device_id w83773_of_match[] = {
	{
		.compatible = "nuvoton,w83773g"
	},
	{ },
};
MODULE_DEVICE_TABLE(of, w83773_of_match);

static inline long temp_of_local(s8 reg)
{
	return reg * 1000;
}

static inline long temp_of_remote(s8 hb, u8 lb)
{
	return (hb << 3 | lb >> 5) * 125;
}

static int get_local_temp(struct regmap *regmap, long *val)
{
	unsigned int regval;
	int ret;

	ret = regmap_read(regmap, W83773_LOCAL_TEMP, &regval);
	if (ret < 0)
		return ret;

	*val = temp_of_local(regval);
	return 0;
}

static int get_remote_temp(struct regmap *regmap, int index, long *val)
{
	unsigned int regval_high;
	unsigned int regval_low;
	int ret;

	ret = regmap_read(regmap, W83773_TEMP_MSB[index], &regval_high);
	if (ret < 0)
		return ret;

	ret = regmap_read(regmap, W83773_TEMP_LSB[index], &regval_low);
	if (ret < 0)
		return ret;

	*val = temp_of_remote(regval_high, regval_low);
	return 0;
}

static int get_fault(struct regmap *regmap, int index, long *val)
{
	unsigned int regval;
	int ret;

	ret = regmap_read(regmap, W83773_STATUS[index], &regval);
	if (ret < 0)
		return ret;

	*val = (regval & 0x04) >> 2;
	return 0;
}

static int get_offset(struct regmap *regmap, int index, long *val)
{
	unsigned int regval_high;
	unsigned int regval_low;
	int ret;

	ret = regmap_read(regmap, W83773_OFFSET_MSB[index], &regval_high);
	if (ret < 0)
		return ret;

	ret = regmap_read(regmap, W83773_OFFSET_LSB[index], &regval_low);
	if (ret < 0)
		return ret;

	*val = temp_of_remote(regval_high, regval_low);
	return 0;
}

static int set_offset(struct regmap *regmap, int index, long val)
{
	int ret;
	u8 high_byte;
	u8 low_byte;

	val = clamp_val(val, -127825, 127825);
	/* offset value equals to (high_byte << 3 | low_byte >> 5) * 125 */
	val /= 125;
	high_byte = val >> 3;
	low_byte = (val & 0x07) << 5;

	ret = regmap_write(regmap, W83773_OFFSET_MSB[index], high_byte);
	if (ret < 0)
		return ret;

	return regmap_write(regmap, W83773_OFFSET_LSB[index], low_byte);
}

static int get_update_interval(struct regmap *regmap, long *val)
{
	unsigned int regval;
	int ret;

	ret = regmap_read(regmap, W83773_CONVERSION_RATE_REG_READ, &regval);
	if (ret < 0)
		return ret;

	*val = 16000 >> regval;
	return 0;
}

static int set_update_interval(struct regmap *regmap, long val)
{
	int rate;

	/*
	 * For valid rates, interval can be calculated as
	 *	interval = (1 << (8 - rate)) * 62.5;
	 * Rounded rate is therefore
	 *	rate = 8 - __fls(interval * 8 / (62.5 * 7));
	 * Use clamp_val() to avoid overflows, and to ensure valid input
	 * for __fls.
	 */
	val = clamp_val(val, 62, 16000) * 10;
	rate = 8 - __fls((val * 8 / (625 * 7)));
	return regmap_write(regmap, W83773_CONVERSION_RATE_REG_WRITE, rate);
}

static int w83773_read(struct device *dev, enum hwmon_sensor_types type,
		       u32 attr, int channel, long *val)
{
	struct regmap *regmap = dev_get_drvdata(dev);

	if (type == hwmon_chip) {
		if (attr == hwmon_chip_update_interval)
			return get_update_interval(regmap, val);
		return -EOPNOTSUPP;
	}

	switch (attr) {
	case hwmon_temp_input:
		if (channel == 0)
			return get_local_temp(regmap, val);
		return get_remote_temp(regmap, channel - 1, val);
	case hwmon_temp_fault:
		return get_fault(regmap, channel - 1, val);
	case hwmon_temp_offset:
		return get_offset(regmap, channel - 1, val);
	default:
		return -EOPNOTSUPP;
	}
}

static int w83773_write(struct device *dev, enum hwmon_sensor_types type,
			u32 attr, int channel, long val)
{
	struct regmap *regmap = dev_get_drvdata(dev);

	if (type == hwmon_chip && attr == hwmon_chip_update_interval)
		return set_update_interval(regmap, val);

	if (type == hwmon_temp && attr == hwmon_temp_offset)
		return set_offset(regmap, channel - 1, val);

	return -EOPNOTSUPP;
}

static umode_t w83773_is_visible(const void *data, enum hwmon_sensor_types type,
				 u32 attr, int channel)
{
	switch (type) {
	case hwmon_chip:
		switch (attr) {
		case hwmon_chip_update_interval:
			return 0644;
		}
		break;
	case hwmon_temp:
		switch (attr) {
		case hwmon_temp_input:
		case hwmon_temp_fault:
			return 0444;
		case hwmon_temp_offset:
			return 0644;
		}
		break;
	default:
		break;
	}
	return 0;
}

static const u32 w83773_chip_config[] = {
	HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL,
	0
};

static const struct hwmon_channel_info w83773_chip = {
	.type = hwmon_chip,
	.config = w83773_chip_config,
};

static const u32 w83773_temp_config[] = {
	HWMON_T_INPUT,
	HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_OFFSET,
	HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_OFFSET,
	0
};

static const struct hwmon_channel_info w83773_temp = {
	.type = hwmon_temp,
	.config = w83773_temp_config,
};

static const struct hwmon_channel_info *w83773_info[] = {
	&w83773_chip,
	&w83773_temp,
	NULL
};

static const struct hwmon_ops w83773_ops = {
	.is_visible = w83773_is_visible,
	.read = w83773_read,
	.write = w83773_write,
};

static const struct hwmon_chip_info w83773_chip_info = {
	.ops = &w83773_ops,
	.info = w83773_info,
};

static const struct regmap_config w83773_regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
};

static int w83773_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct device *dev = &client->dev;
	struct device *hwmon_dev;
	struct regmap *regmap;
	int ret;

	regmap = devm_regmap_init_i2c(client, &w83773_regmap_config);
	if (IS_ERR(regmap)) {
		dev_err(dev, "failed to allocate register map\n");
		return PTR_ERR(regmap);
	}

	/* Set the conversion rate to 2 Hz */
	ret = regmap_write(regmap, W83773_CONVERSION_RATE_REG_WRITE, 0x05);
	if (ret < 0) {
		dev_err(&client->dev, "error writing config rate register\n");
		return ret;
	}

	i2c_set_clientdata(client, regmap);

	hwmon_dev = devm_hwmon_device_register_with_info(dev,
							 client->name,
							 regmap,
							 &w83773_chip_info,
							 NULL);
	return PTR_ERR_OR_ZERO(hwmon_dev);
}

static struct i2c_driver w83773_driver = {
	.class = I2C_CLASS_HWMON,
	.driver = {
		.name	= "w83773g",
		.of_match_table = of_match_ptr(w83773_of_match),
	},
	.probe = w83773_probe,
	.id_table = w83773_id,
};

module_i2c_driver(w83773_driver);

MODULE_AUTHOR("Lei YU <mine260309@gmail.com>");
MODULE_DESCRIPTION("W83773G temperature sensor driver");
MODULE_LICENSE("GPL");