/*
 * I2C client/driver for the ST M41T80 family of i2c rtc chips.
 *
 * Author: Alexander Bigga <ab@mycable.de>
 *
 * Based on m41t00.c by Mark A. Greer <mgreer@mvista.com>
 *
 * 2006 (c) mycable GmbH
 *
 * 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/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/i2c.h>
#include <linux/rtc.h>
#include <linux/bcd.h>

#define M41T80_REG_SSEC	0
#define M41T80_REG_SEC	1
#define M41T80_REG_MIN	2
#define M41T80_REG_HOUR	3
#define M41T80_REG_WDAY	4
#define M41T80_REG_DAY	5
#define M41T80_REG_MON	6
#define M41T80_REG_YEAR	7
#define M41T80_REG_ALARM_MON	0xa
#define M41T80_REG_ALARM_DAY	0xb
#define M41T80_REG_ALARM_HOUR	0xc
#define M41T80_REG_ALARM_MIN	0xd
#define M41T80_REG_ALARM_SEC	0xe
#define M41T80_REG_FLAGS	0xf
#define M41T80_REG_SQW	0x13

#define M41T80_DATETIME_REG_SIZE	(M41T80_REG_YEAR + 1)
#define M41T80_ALARM_REG_SIZE	\
	(M41T80_REG_ALARM_SEC + 1 - M41T80_REG_ALARM_MON)

#define M41T80_SEC_ST		(1 << 7)	/* ST: Stop Bit */
#define M41T80_ALMON_AFE	(1 << 7)	/* AFE: AF Enable Bit */
#define M41T80_ALMON_SQWE	(1 << 6)	/* SQWE: SQW Enable Bit */
#define M41T80_ALHOUR_HT	(1 << 6)	/* HT: Halt Update Bit */
#define M41T80_FLAGS_AF		(1 << 6)	/* AF: Alarm Flag Bit */
#define M41T80_FLAGS_BATT_LOW	(1 << 4)	/* BL: Battery Low Bit */

#define M41T80_FEATURE_HT	(1 << 0)
#define M41T80_FEATURE_BL	(1 << 1)

#define DRV_VERSION "0.05"

struct m41t80_chip_info {
	const char *name;
	u8 features;
};

static const struct m41t80_chip_info m41t80_chip_info_tbl[] = {
	{
		.name		= "m41t80",
		.features	= 0,
	},
	{
		.name		= "m41t81",
		.features	= M41T80_FEATURE_HT,
	},
	{
		.name		= "m41t81s",
		.features	= M41T80_FEATURE_HT | M41T80_FEATURE_BL,
	},
	{
		.name		= "m41t82",
		.features	= M41T80_FEATURE_HT | M41T80_FEATURE_BL,
	},
	{
		.name		= "m41t83",
		.features	= M41T80_FEATURE_HT | M41T80_FEATURE_BL,
	},
	{
		.name		= "m41st84",
		.features	= M41T80_FEATURE_HT | M41T80_FEATURE_BL,
	},
	{
		.name		= "m41st85",
		.features	= M41T80_FEATURE_HT | M41T80_FEATURE_BL,
	},
	{
		.name		= "m41st87",
		.features	= M41T80_FEATURE_HT | M41T80_FEATURE_BL,
	},
};

struct m41t80_data {
	const struct m41t80_chip_info *chip;
	struct rtc_device *rtc;
};

static int m41t80_get_datetime(struct i2c_client *client,
			       struct rtc_time *tm)
{
	u8 buf[M41T80_DATETIME_REG_SIZE], dt_addr[1] = { M41T80_REG_SEC };
	struct i2c_msg msgs[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1,
			.buf	= dt_addr,
		},
		{
			.addr	= client->addr,
			.flags	= I2C_M_RD,
			.len	= M41T80_DATETIME_REG_SIZE - M41T80_REG_SEC,
			.buf	= buf + M41T80_REG_SEC,
		},
	};

	if (i2c_transfer(client->adapter, msgs, 2) < 0) {
		dev_err(&client->dev, "read error\n");
		return -EIO;
	}

	tm->tm_sec = BCD2BIN(buf[M41T80_REG_SEC] & 0x7f);
	tm->tm_min = BCD2BIN(buf[M41T80_REG_MIN] & 0x7f);
	tm->tm_hour = BCD2BIN(buf[M41T80_REG_HOUR] & 0x3f);
	tm->tm_mday = BCD2BIN(buf[M41T80_REG_DAY] & 0x3f);
	tm->tm_wday = buf[M41T80_REG_WDAY] & 0x07;
	tm->tm_mon = BCD2BIN(buf[M41T80_REG_MON] & 0x1f) - 1;

	/* assume 20YY not 19YY, and ignore the Century Bit */
	tm->tm_year = BCD2BIN(buf[M41T80_REG_YEAR]) + 100;
	return 0;
}

/* Sets the given date and time to the real time clock. */
static int m41t80_set_datetime(struct i2c_client *client, struct rtc_time *tm)
{
	u8 wbuf[1 + M41T80_DATETIME_REG_SIZE];
	u8 *buf = &wbuf[1];
	u8 dt_addr[1] = { M41T80_REG_SEC };
	struct i2c_msg msgs_in[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1,
			.buf	= dt_addr,
		},
		{
			.addr	= client->addr,
			.flags	= I2C_M_RD,
			.len	= M41T80_DATETIME_REG_SIZE - M41T80_REG_SEC,
			.buf	= buf + M41T80_REG_SEC,
		},
	};
	struct i2c_msg msgs[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1 + M41T80_DATETIME_REG_SIZE,
			.buf	= wbuf,
		 },
	};

	/* Read current reg values into buf[1..7] */
	if (i2c_transfer(client->adapter, msgs_in, 2) < 0) {
		dev_err(&client->dev, "read error\n");
		return -EIO;
	}

	wbuf[0] = 0; /* offset into rtc's regs */
	/* Merge time-data and register flags into buf[0..7] */
	buf[M41T80_REG_SSEC] = 0;
	buf[M41T80_REG_SEC] =
		BIN2BCD(tm->tm_sec) | (buf[M41T80_REG_SEC] & ~0x7f);
	buf[M41T80_REG_MIN] =
		BIN2BCD(tm->tm_min) | (buf[M41T80_REG_MIN] & ~0x7f);
	buf[M41T80_REG_HOUR] =
		BIN2BCD(tm->tm_hour) | (buf[M41T80_REG_HOUR] & ~0x3f) ;
	buf[M41T80_REG_WDAY] =
		(tm->tm_wday & 0x07) | (buf[M41T80_REG_WDAY] & ~0x07);
	buf[M41T80_REG_DAY] =
		BIN2BCD(tm->tm_mday) | (buf[M41T80_REG_DAY] & ~0x3f);
	buf[M41T80_REG_MON] =
		BIN2BCD(tm->tm_mon + 1) | (buf[M41T80_REG_MON] & ~0x1f);
	/* assume 20YY not 19YY */
	buf[M41T80_REG_YEAR] = BIN2BCD(tm->tm_year % 100);

	if (i2c_transfer(client->adapter, msgs, 1) != 1) {
		dev_err(&client->dev, "write error\n");
		return -EIO;
	}
	return 0;
}

#if defined(CONFIG_RTC_INTF_PROC) || defined(CONFIG_RTC_INTF_PROC_MODULE)
static int m41t80_rtc_proc(struct device *dev, struct seq_file *seq)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct m41t80_data *clientdata = i2c_get_clientdata(client);
	u8 reg;

	if (clientdata->chip->features & M41T80_FEATURE_BL) {
		reg = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
		seq_printf(seq, "battery\t\t: %s\n",
			   (reg & M41T80_FLAGS_BATT_LOW) ? "exhausted" : "ok");
	}
	return 0;
}
#else
#define m41t80_rtc_proc NULL
#endif

static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	return m41t80_get_datetime(to_i2c_client(dev), tm);
}

static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	return m41t80_set_datetime(to_i2c_client(dev), tm);
}

#if defined(CONFIG_RTC_INTF_DEV) || defined(CONFIG_RTC_INTF_DEV_MODULE)
static int
m41t80_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
	struct i2c_client *client = to_i2c_client(dev);
	int rc;

	switch (cmd) {
	case RTC_AIE_OFF:
	case RTC_AIE_ON:
		break;
	default:
		return -ENOIOCTLCMD;
	}

	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
	if (rc < 0)
		goto err;
	switch (cmd) {
	case RTC_AIE_OFF:
		rc &= ~M41T80_ALMON_AFE;
		break;
	case RTC_AIE_ON:
		rc |= M41T80_ALMON_AFE;
		break;
	}
	if (i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, rc) < 0)
		goto err;
	return 0;
err:
	return -EIO;
}
#else
#define	m41t80_rtc_ioctl NULL
#endif

static int m41t80_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
	struct i2c_client *client = to_i2c_client(dev);
	u8 wbuf[1 + M41T80_ALARM_REG_SIZE];
	u8 *buf = &wbuf[1];
	u8 *reg = buf - M41T80_REG_ALARM_MON;
	u8 dt_addr[1] = { M41T80_REG_ALARM_MON };
	struct i2c_msg msgs_in[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1,
			.buf	= dt_addr,
		},
		{
			.addr	= client->addr,
			.flags	= I2C_M_RD,
			.len	= M41T80_ALARM_REG_SIZE,
			.buf	= buf,
		},
	};
	struct i2c_msg msgs[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1 + M41T80_ALARM_REG_SIZE,
			.buf	= wbuf,
		 },
	};

	if (i2c_transfer(client->adapter, msgs_in, 2) < 0) {
		dev_err(&client->dev, "read error\n");
		return -EIO;
	}
	reg[M41T80_REG_ALARM_MON] &= ~(0x1f | M41T80_ALMON_AFE);
	reg[M41T80_REG_ALARM_DAY] = 0;
	reg[M41T80_REG_ALARM_HOUR] &= ~(0x3f | 0x80);
	reg[M41T80_REG_ALARM_MIN] = 0;
	reg[M41T80_REG_ALARM_SEC] = 0;

	wbuf[0] = M41T80_REG_ALARM_MON; /* offset into rtc's regs */
	reg[M41T80_REG_ALARM_SEC] |= t->time.tm_sec >= 0 ?
		BIN2BCD(t->time.tm_sec) : 0x80;
	reg[M41T80_REG_ALARM_MIN] |= t->time.tm_min >= 0 ?
		BIN2BCD(t->time.tm_min) : 0x80;
	reg[M41T80_REG_ALARM_HOUR] |= t->time.tm_hour >= 0 ?
		BIN2BCD(t->time.tm_hour) : 0x80;
	reg[M41T80_REG_ALARM_DAY] |= t->time.tm_mday >= 0 ?
		BIN2BCD(t->time.tm_mday) : 0x80;
	if (t->time.tm_mon >= 0)
		reg[M41T80_REG_ALARM_MON] |= BIN2BCD(t->time.tm_mon + 1);
	else
		reg[M41T80_REG_ALARM_DAY] |= 0x40;

	if (i2c_transfer(client->adapter, msgs, 1) != 1) {
		dev_err(&client->dev, "write error\n");
		return -EIO;
	}

	if (t->enabled) {
		reg[M41T80_REG_ALARM_MON] |= M41T80_ALMON_AFE;
		if (i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
					      reg[M41T80_REG_ALARM_MON]) < 0) {
			dev_err(&client->dev, "write error\n");
			return -EIO;
		}
	}
	return 0;
}

static int m41t80_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
	struct i2c_client *client = to_i2c_client(dev);
	u8 buf[M41T80_ALARM_REG_SIZE + 1]; /* all alarm regs and flags */
	u8 dt_addr[1] = { M41T80_REG_ALARM_MON };
	u8 *reg = buf - M41T80_REG_ALARM_MON;
	struct i2c_msg msgs[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1,
			.buf	= dt_addr,
		},
		{
			.addr	= client->addr,
			.flags	= I2C_M_RD,
			.len	= M41T80_ALARM_REG_SIZE + 1,
			.buf	= buf,
		},
	};

	if (i2c_transfer(client->adapter, msgs, 2) < 0) {
		dev_err(&client->dev, "read error\n");
		return -EIO;
	}
	t->time.tm_sec = -1;
	t->time.tm_min = -1;
	t->time.tm_hour = -1;
	t->time.tm_mday = -1;
	t->time.tm_mon = -1;
	if (!(reg[M41T80_REG_ALARM_SEC] & 0x80))
		t->time.tm_sec = BCD2BIN(reg[M41T80_REG_ALARM_SEC] & 0x7f);
	if (!(reg[M41T80_REG_ALARM_MIN] & 0x80))
		t->time.tm_min = BCD2BIN(reg[M41T80_REG_ALARM_MIN] & 0x7f);
	if (!(reg[M41T80_REG_ALARM_HOUR] & 0x80))
		t->time.tm_hour = BCD2BIN(reg[M41T80_REG_ALARM_HOUR] & 0x3f);
	if (!(reg[M41T80_REG_ALARM_DAY] & 0x80))
		t->time.tm_mday = BCD2BIN(reg[M41T80_REG_ALARM_DAY] & 0x3f);
	if (!(reg[M41T80_REG_ALARM_DAY] & 0x40))
		t->time.tm_mon = BCD2BIN(reg[M41T80_REG_ALARM_MON] & 0x1f) - 1;
	t->time.tm_year = -1;
	t->time.tm_wday = -1;
	t->time.tm_yday = -1;
	t->time.tm_isdst = -1;
	t->enabled = !!(reg[M41T80_REG_ALARM_MON] & M41T80_ALMON_AFE);
	t->pending = !!(reg[M41T80_REG_FLAGS] & M41T80_FLAGS_AF);
	return 0;
}

static struct rtc_class_ops m41t80_rtc_ops = {
	.read_time = m41t80_rtc_read_time,
	.set_time = m41t80_rtc_set_time,
	.read_alarm = m41t80_rtc_read_alarm,
	.set_alarm = m41t80_rtc_set_alarm,
	.proc = m41t80_rtc_proc,
	.ioctl = m41t80_rtc_ioctl,
};

#if defined(CONFIG_RTC_INTF_SYSFS) || defined(CONFIG_RTC_INTF_SYSFS_MODULE)
static ssize_t m41t80_sysfs_show_flags(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	struct i2c_client *client = to_i2c_client(dev);
	int val;

	val = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
	if (val < 0)
		return -EIO;
	return sprintf(buf, "%#x\n", val);
}
static DEVICE_ATTR(flags, S_IRUGO, m41t80_sysfs_show_flags, NULL);

static ssize_t m41t80_sysfs_show_sqwfreq(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	struct i2c_client *client = to_i2c_client(dev);
	int val;

	val = i2c_smbus_read_byte_data(client, M41T80_REG_SQW);
	if (val < 0)
		return -EIO;
	val = (val >> 4) & 0xf;
	switch (val) {
	case 0:
		break;
	case 1:
		val = 32768;
		break;
	default:
		val = 32768 >> val;
	}
	return sprintf(buf, "%d\n", val);
}
static ssize_t m41t80_sysfs_set_sqwfreq(struct device *dev,
				struct device_attribute *attr,
				const char *buf, size_t count)
{
	struct i2c_client *client = to_i2c_client(dev);
	int almon, sqw;
	int val = simple_strtoul(buf, NULL, 0);

	if (val) {
		if (!is_power_of_2(val))
			return -EINVAL;
		val = ilog2(val);
		if (val == 15)
			val = 1;
		else if (val < 14)
			val = 15 - val;
		else
			return -EINVAL;
	}
	/* disable SQW, set SQW frequency & re-enable */
	almon = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
	if (almon < 0)
		return -EIO;
	sqw = i2c_smbus_read_byte_data(client, M41T80_REG_SQW);
	if (sqw < 0)
		return -EIO;
	sqw = (sqw & 0x0f) | (val << 4);
	if (i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
				      almon & ~M41T80_ALMON_SQWE) < 0 ||
	    i2c_smbus_write_byte_data(client, M41T80_REG_SQW, sqw) < 0)
		return -EIO;
	if (val && i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
					     almon | M41T80_ALMON_SQWE) < 0)
		return -EIO;
	return count;
}
static DEVICE_ATTR(sqwfreq, S_IRUGO | S_IWUSR,
		   m41t80_sysfs_show_sqwfreq, m41t80_sysfs_set_sqwfreq);

static struct attribute *attrs[] = {
	&dev_attr_flags.attr,
	&dev_attr_sqwfreq.attr,
	NULL,
};
static struct attribute_group attr_group = {
	.attrs = attrs,
};

static int m41t80_sysfs_register(struct device *dev)
{
	return sysfs_create_group(&dev->kobj, &attr_group);
}
#else
static int m41t80_sysfs_register(struct device *dev)
{
	return 0;
}
#endif

/*
 *****************************************************************************
 *
 *	Driver Interface
 *
 *****************************************************************************
 */
static int m41t80_probe(struct i2c_client *client)
{
	int i, rc = 0;
	struct rtc_device *rtc = NULL;
	struct rtc_time tm;
	const struct m41t80_chip_info *chip;
	struct m41t80_data *clientdata = NULL;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C
				     | I2C_FUNC_SMBUS_BYTE_DATA)) {
		rc = -ENODEV;
		goto exit;
	}

	dev_info(&client->dev,
		 "chip found, driver version " DRV_VERSION "\n");

	chip = NULL;
	for (i = 0; i < ARRAY_SIZE(m41t80_chip_info_tbl); i++) {
		if (!strcmp(m41t80_chip_info_tbl[i].name, client->name)) {
			chip = &m41t80_chip_info_tbl[i];
			break;
		}
	}
	if (!chip) {
		dev_err(&client->dev, "%s is not supported\n", client->name);
		rc = -ENODEV;
		goto exit;
	}

	clientdata = kzalloc(sizeof(*clientdata), GFP_KERNEL);
	if (!clientdata) {
		rc = -ENOMEM;
		goto exit;
	}

	rtc = rtc_device_register(client->name, &client->dev,
				  &m41t80_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc)) {
		rc = PTR_ERR(rtc);
		rtc = NULL;
		goto exit;
	}

	clientdata->rtc = rtc;
	clientdata->chip = chip;
	i2c_set_clientdata(client, clientdata);

	/* Make sure HT (Halt Update) bit is cleared */
	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);
	if (rc < 0)
		goto ht_err;

	if (rc & M41T80_ALHOUR_HT) {
		if (chip->features & M41T80_FEATURE_HT) {
			m41t80_get_datetime(client, &tm);
			dev_info(&client->dev, "HT bit was set!\n");
			dev_info(&client->dev,
				 "Power Down at "
				 "%04i-%02i-%02i %02i:%02i:%02i\n",
				 tm.tm_year + 1900,
				 tm.tm_mon + 1, tm.tm_mday, tm.tm_hour,
				 tm.tm_min, tm.tm_sec);
		}
		if (i2c_smbus_write_byte_data(client,
					      M41T80_REG_ALARM_HOUR,
					      rc & ~M41T80_ALHOUR_HT) < 0)
			goto ht_err;
	}

	/* Make sure ST (stop) bit is cleared */
	rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);
	if (rc < 0)
		goto st_err;

	if (rc & M41T80_SEC_ST) {
		if (i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
					      rc & ~M41T80_SEC_ST) < 0)
			goto st_err;
	}

	rc = m41t80_sysfs_register(&client->dev);
	if (rc)
		goto exit;

	return 0;

st_err:
	rc = -EIO;
	dev_err(&client->dev, "Can't clear ST bit\n");
	goto exit;
ht_err:
	rc = -EIO;
	dev_err(&client->dev, "Can't clear HT bit\n");
	goto exit;

exit:
	if (rtc)
		rtc_device_unregister(rtc);
	kfree(clientdata);
	return rc;
}

static int m41t80_remove(struct i2c_client *client)
{
	struct m41t80_data *clientdata = i2c_get_clientdata(client);
	struct rtc_device *rtc = clientdata->rtc;

	if (rtc)
		rtc_device_unregister(rtc);
	kfree(clientdata);

	return 0;
}

static struct i2c_driver m41t80_driver = {
	.driver = {
		.name = "m41t80",
	},
	.probe = m41t80_probe,
	.remove = m41t80_remove,
};

static int __init m41t80_rtc_init(void)
{
	return i2c_add_driver(&m41t80_driver);
}

static void __exit m41t80_rtc_exit(void)
{
	i2c_del_driver(&m41t80_driver);
}

MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);

module_init(m41t80_rtc_init);
module_exit(m41t80_rtc_exit);