/*
 * A driver for the I2C members of the Abracon AB x8xx RTC family,
 * and compatible: AB 1805 and AB 0805
 *
 * Copyright 2014-2015 Macq S.A.
 *
 * Author: Philippe De Muyter <phdm@macqel.be>
 * Author: Alexandre Belloni <alexandre.belloni@free-electrons.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/bcd.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/rtc.h>

#define ABX8XX_REG_HTH		0x00
#define ABX8XX_REG_SC		0x01
#define ABX8XX_REG_MN		0x02
#define ABX8XX_REG_HR		0x03
#define ABX8XX_REG_DA		0x04
#define ABX8XX_REG_MO		0x05
#define ABX8XX_REG_YR		0x06
#define ABX8XX_REG_WD		0x07

#define ABX8XX_REG_CTRL1	0x10
#define ABX8XX_CTRL_WRITE	BIT(1)
#define ABX8XX_CTRL_12_24	BIT(6)

#define ABX8XX_REG_CFG_KEY	0x1f
#define ABX8XX_CFG_KEY_MISC	0x9d

#define ABX8XX_REG_ID0		0x28

#define ABX8XX_REG_TRICKLE	0x20
#define ABX8XX_TRICKLE_CHARGE_ENABLE	0xa0
#define ABX8XX_TRICKLE_STANDARD_DIODE	0x8
#define ABX8XX_TRICKLE_SCHOTTKY_DIODE	0x4

static u8 trickle_resistors[] = {0, 3, 6, 11};

enum abx80x_chip {AB0801, AB0803, AB0804, AB0805,
	AB1801, AB1803, AB1804, AB1805, ABX80X};

struct abx80x_cap {
	u16 pn;
	bool has_tc;
};

static struct abx80x_cap abx80x_caps[] = {
	[AB0801] = {.pn = 0x0801},
	[AB0803] = {.pn = 0x0803},
	[AB0804] = {.pn = 0x0804, .has_tc = true},
	[AB0805] = {.pn = 0x0805, .has_tc = true},
	[AB1801] = {.pn = 0x1801},
	[AB1803] = {.pn = 0x1803},
	[AB1804] = {.pn = 0x1804, .has_tc = true},
	[AB1805] = {.pn = 0x1805, .has_tc = true},
	[ABX80X] = {.pn = 0}
};

static struct i2c_driver abx80x_driver;

static int abx80x_enable_trickle_charger(struct i2c_client *client,
					 u8 trickle_cfg)
{
	int err;

	/*
	 * Write the configuration key register to enable access to the Trickle
	 * register
	 */
	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CFG_KEY,
					ABX8XX_CFG_KEY_MISC);
	if (err < 0) {
		dev_err(&client->dev, "Unable to write configuration key\n");
		return -EIO;
	}

	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_TRICKLE,
					ABX8XX_TRICKLE_CHARGE_ENABLE |
					trickle_cfg);
	if (err < 0) {
		dev_err(&client->dev, "Unable to write trickle register\n");
		return -EIO;
	}

	return 0;
}

static int abx80x_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct i2c_client *client = to_i2c_client(dev);
	unsigned char buf[8];
	int err;

	err = i2c_smbus_read_i2c_block_data(client, ABX8XX_REG_HTH,
					    sizeof(buf), buf);
	if (err < 0) {
		dev_err(&client->dev, "Unable to read date\n");
		return -EIO;
	}

	tm->tm_sec = bcd2bin(buf[ABX8XX_REG_SC] & 0x7F);
	tm->tm_min = bcd2bin(buf[ABX8XX_REG_MN] & 0x7F);
	tm->tm_hour = bcd2bin(buf[ABX8XX_REG_HR] & 0x3F);
	tm->tm_wday = buf[ABX8XX_REG_WD] & 0x7;
	tm->tm_mday = bcd2bin(buf[ABX8XX_REG_DA] & 0x3F);
	tm->tm_mon = bcd2bin(buf[ABX8XX_REG_MO] & 0x1F) - 1;
	tm->tm_year = bcd2bin(buf[ABX8XX_REG_YR]) + 100;

	err = rtc_valid_tm(tm);
	if (err < 0)
		dev_err(&client->dev, "retrieved date/time is not valid.\n");

	return err;
}

static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct i2c_client *client = to_i2c_client(dev);
	unsigned char buf[8];
	int err;

	if (tm->tm_year < 100)
		return -EINVAL;

	buf[ABX8XX_REG_HTH] = 0;
	buf[ABX8XX_REG_SC] = bin2bcd(tm->tm_sec);
	buf[ABX8XX_REG_MN] = bin2bcd(tm->tm_min);
	buf[ABX8XX_REG_HR] = bin2bcd(tm->tm_hour);
	buf[ABX8XX_REG_DA] = bin2bcd(tm->tm_mday);
	buf[ABX8XX_REG_MO] = bin2bcd(tm->tm_mon + 1);
	buf[ABX8XX_REG_YR] = bin2bcd(tm->tm_year - 100);
	buf[ABX8XX_REG_WD] = tm->tm_wday;

	err = i2c_smbus_write_i2c_block_data(client, ABX8XX_REG_HTH,
					     sizeof(buf), buf);
	if (err < 0) {
		dev_err(&client->dev, "Unable to write to date registers\n");
		return -EIO;
	}

	return 0;
}

static const struct rtc_class_ops abx80x_rtc_ops = {
	.read_time	= abx80x_rtc_read_time,
	.set_time	= abx80x_rtc_set_time,
};

static int abx80x_dt_trickle_cfg(struct device_node *np)
{
	const char *diode;
	int trickle_cfg = 0;
	int i, ret;
	u32 tmp;

	ret = of_property_read_string(np, "abracon,tc-diode", &diode);
	if (ret)
		return ret;

	if (!strcmp(diode, "standard"))
		trickle_cfg |= ABX8XX_TRICKLE_STANDARD_DIODE;
	else if (!strcmp(diode, "schottky"))
		trickle_cfg |= ABX8XX_TRICKLE_SCHOTTKY_DIODE;
	else
		return -EINVAL;

	ret = of_property_read_u32(np, "abracon,tc-resistor", &tmp);
	if (ret)
		return ret;

	for (i = 0; i < sizeof(trickle_resistors); i++)
		if (trickle_resistors[i] == tmp)
			break;

	if (i == sizeof(trickle_resistors))
		return -EINVAL;

	return (trickle_cfg | i);
}

static int abx80x_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct device_node *np = client->dev.of_node;
	struct rtc_device *rtc;
	int i, data, err, trickle_cfg = -EINVAL;
	char buf[7];
	unsigned int part = id->driver_data;
	unsigned int partnumber;
	unsigned int majrev, minrev;
	unsigned int lot;
	unsigned int wafer;
	unsigned int uid;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
		return -ENODEV;

	err = i2c_smbus_read_i2c_block_data(client, ABX8XX_REG_ID0,
					    sizeof(buf), buf);
	if (err < 0) {
		dev_err(&client->dev, "Unable to read partnumber\n");
		return -EIO;
	}

	partnumber = (buf[0] << 8) | buf[1];
	majrev = buf[2] >> 3;
	minrev = buf[2] & 0x7;
	lot = ((buf[4] & 0x80) << 2) | ((buf[6] & 0x80) << 1) | buf[3];
	uid = ((buf[4] & 0x7f) << 8) | buf[5];
	wafer = (buf[6] & 0x7c) >> 2;
	dev_info(&client->dev, "model %04x, revision %u.%u, lot %x, wafer %x, uid %x\n",
		 partnumber, majrev, minrev, lot, wafer, uid);

	data = i2c_smbus_read_byte_data(client, ABX8XX_REG_CTRL1);
	if (data < 0) {
		dev_err(&client->dev, "Unable to read control register\n");
		return -EIO;
	}

	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CTRL1,
					((data & ~ABX8XX_CTRL_12_24) |
					 ABX8XX_CTRL_WRITE));
	if (err < 0) {
		dev_err(&client->dev, "Unable to write control register\n");
		return -EIO;
	}

	/* part autodetection */
	if (part == ABX80X) {
		for (i = 0; abx80x_caps[i].pn; i++)
			if (partnumber == abx80x_caps[i].pn)
				break;
		if (abx80x_caps[i].pn == 0) {
			dev_err(&client->dev, "Unknown part: %04x\n",
				partnumber);
			return -EINVAL;
		}
		part = i;
	}

	if (partnumber != abx80x_caps[part].pn) {
		dev_err(&client->dev, "partnumber mismatch %04x != %04x\n",
			partnumber, abx80x_caps[part].pn);
		return -EINVAL;
	}

	if (np && abx80x_caps[part].has_tc)
		trickle_cfg = abx80x_dt_trickle_cfg(np);

	if (trickle_cfg > 0) {
		dev_info(&client->dev, "Enabling trickle charger: %02x\n",
			 trickle_cfg);
		abx80x_enable_trickle_charger(client, trickle_cfg);
	}

	rtc = devm_rtc_device_register(&client->dev, abx80x_driver.driver.name,
				       &abx80x_rtc_ops, THIS_MODULE);

	if (IS_ERR(rtc))
		return PTR_ERR(rtc);

	i2c_set_clientdata(client, rtc);

	return 0;
}

static int abx80x_remove(struct i2c_client *client)
{
	return 0;
}

static const struct i2c_device_id abx80x_id[] = {
	{ "abx80x", ABX80X },
	{ "ab0801", AB0801 },
	{ "ab0803", AB0803 },
	{ "ab0804", AB0804 },
	{ "ab0805", AB0805 },
	{ "ab1801", AB1801 },
	{ "ab1803", AB1803 },
	{ "ab1804", AB1804 },
	{ "ab1805", AB1805 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, abx80x_id);

static struct i2c_driver abx80x_driver = {
	.driver		= {
		.name	= "rtc-abx80x",
	},
	.probe		= abx80x_probe,
	.remove		= abx80x_remove,
	.id_table	= abx80x_id,
};

module_i2c_driver(abx80x_driver);

MODULE_AUTHOR("Philippe De Muyter <phdm@macqel.be>");
MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
MODULE_DESCRIPTION("Abracon ABX80X RTC driver");
MODULE_LICENSE("GPL v2");