/*
   * rtc-ds1307.c - RTC driver for some mostly-compatible I2C chips.
   *
   *  Copyright (C) 2005 James Chapman (ds1337 core)
   *  Copyright (C) 2006 David Brownell
   *  Copyright (C) 2009 Matthias Fuchs (rx8025 support)
   *  Copyright (C) 2012 Bertrand Achard (nvram access fixes)
   *
   * 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/i2c.h>
  #include <linux/string.h>
  #include <linux/rtc.h>
  #include <linux/bcd.h>
  #include <linux/rtc/ds1307.h>
  
  /*
   * We can't determine type by probing, but if we expect pre-Linux code
   * to have set the chip up as a clock (turning on the oscillator and
   * setting the date and time), Linux can ignore the non-clock features.
   * That's a natural job for a factory or repair bench.
   */
  enum ds_type {
  	ds_1307,
  	ds_1337,
  	ds_1338,
  	ds_1339,
  	ds_1340,
  	ds_1388,
  	ds_3231,
  	m41t00,
  	mcp7941x,
  	rx_8025,
  	last_ds_type /* always last */
  	/* rs5c372 too?  different address... */
  };
  
  
  /* RTC registers don't differ much, except for the century flag */
  #define DS1307_REG_SECS		0x00	/* 00-59 */
  #	define DS1307_BIT_CH		0x80
  #	define DS1340_BIT_nEOSC		0x80
  #	define MCP7941X_BIT_ST		0x80
  #define DS1307_REG_MIN		0x01	/* 00-59 */
  #define DS1307_REG_HOUR		0x02	/* 00-23, or 1-12{am,pm} */
  #	define DS1307_BIT_12HR		0x40	/* in REG_HOUR */
  #	define DS1307_BIT_PM		0x20	/* in REG_HOUR */
  #	define DS1340_BIT_CENTURY_EN	0x80	/* in REG_HOUR */
  #	define DS1340_BIT_CENTURY	0x40	/* in REG_HOUR */
  #define DS1307_REG_WDAY		0x03	/* 01-07 */
  #	define MCP7941X_BIT_VBATEN	0x08
  #define DS1307_REG_MDAY		0x04	/* 01-31 */
  #define DS1307_REG_MONTH	0x05	/* 01-12 */
  #	define DS1337_BIT_CENTURY	0x80	/* in REG_MONTH */
  #define DS1307_REG_YEAR		0x06	/* 00-99 */
  
  /*
   * Other registers (control, status, alarms, trickle charge, NVRAM, etc)
   * start at 7, and they differ a LOT. Only control and status matter for
   * basic RTC date and time functionality; be careful using them.
   */
  #define DS1307_REG_CONTROL	0x07		/* or ds1338 */
  #	define DS1307_BIT_OUT		0x80
  #	define DS1338_BIT_OSF		0x20
  #	define DS1307_BIT_SQWE		0x10
  #	define DS1307_BIT_RS1		0x02
  #	define DS1307_BIT_RS0		0x01
  #define DS1337_REG_CONTROL	0x0e
  #	define DS1337_BIT_nEOSC		0x80
  #	define DS1339_BIT_BBSQI		0x20
  #	define DS3231_BIT_BBSQW		0x40 /* same as BBSQI */
  #	define DS1337_BIT_RS2		0x10
  #	define DS1337_BIT_RS1		0x08
  #	define DS1337_BIT_INTCN		0x04
  #	define DS1337_BIT_A2IE		0x02
  #	define DS1337_BIT_A1IE		0x01
  #define DS1340_REG_CONTROL	0x07
  #	define DS1340_BIT_OUT		0x80
  #	define DS1340_BIT_FT		0x40
  #	define DS1340_BIT_CALIB_SIGN	0x20
  #	define DS1340_M_CALIBRATION	0x1f
  #define DS1340_REG_FLAG		0x09
  #	define DS1340_BIT_OSF		0x80
  #define DS1337_REG_STATUS	0x0f
  #	define DS1337_BIT_OSF		0x80
  #	define DS1337_BIT_A2I		0x02
  #	define DS1337_BIT_A1I		0x01
  #define DS1339_REG_ALARM1_SECS	0x07
  
  #define DS13XX_TRICKLE_CHARGER_MAGIC	0xa0
  
  #define RX8025_REG_CTRL1	0x0e
  #	define RX8025_BIT_2412		0x20
  #define RX8025_REG_CTRL2	0x0f
  #	define RX8025_BIT_PON		0x10
  #	define RX8025_BIT_VDET		0x40
  #	define RX8025_BIT_XST		0x20
  
  
  struct ds1307 {
  	u8			offset; /* register's offset */
  	u8			regs[11];
  	u16			nvram_offset;
  	struct bin_attribute	*nvram;
  	enum ds_type		type;
  	unsigned long		flags;
  #define HAS_NVRAM	0		/* bit 0 == sysfs file active */
  #define HAS_ALARM	1		/* bit 1 == irq claimed */
  	struct i2c_client	*client;
  	struct rtc_device	*rtc;
  	struct work_struct	work;
  	s32 (*read_block_data)(const struct i2c_client *client, u8 command,
  			       u8 length, u8 *values);
  	s32 (*write_block_data)(const struct i2c_client *client, u8 command,
  				u8 length, const u8 *values);
  };
  
  struct chip_desc {
  	unsigned		alarm:1;
  	u16			nvram_offset;
  	u16			nvram_size;
  	u16			trickle_charger_reg;
  };
  
  static const struct chip_desc chips[last_ds_type] = {
  	[ds_1307] = {
  		.nvram_offset	= 8,
  		.nvram_size	= 56,
  	},
  	[ds_1337] = {
  		.alarm		= 1,
  	},
  	[ds_1338] = {
  		.nvram_offset	= 8,
  		.nvram_size	= 56,
  	},
  	[ds_1339] = {
  		.alarm		= 1,
  		.trickle_charger_reg = 0x10,
  	},
  	[ds_1340] = {
  		.trickle_charger_reg = 0x08,
  	},
  	[ds_1388] = {
  		.trickle_charger_reg = 0x0a,
  	},
  	[ds_3231] = {
  		.alarm		= 1,
  	},
  	[mcp7941x] = {
  		/* this is battery backed SRAM */
  		.nvram_offset	= 0x20,
  		.nvram_size	= 0x40,
  	},
  };
  
  static const struct i2c_device_id ds1307_id[] = {
  	{ "ds1307", ds_1307 },
  	{ "ds1337", ds_1337 },
  	{ "ds1338", ds_1338 },
  	{ "ds1339", ds_1339 },
  	{ "ds1388", ds_1388 },
  	{ "ds1340", ds_1340 },
  	{ "ds3231", ds_3231 },
  	{ "m41t00", m41t00 },
  	{ "mcp7941x", mcp7941x },
  	{ "pt7c4338", ds_1307 },
  	{ "rx8025", rx_8025 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, ds1307_id);
  
  /*----------------------------------------------------------------------*/
  
  #define BLOCK_DATA_MAX_TRIES 10
  
  static s32 ds1307_read_block_data_once(const struct i2c_client *client,
  				       u8 command, u8 length, u8 *values)
  {
  	s32 i, data;
  
  	for (i = 0; i < length; i++) {
  		data = i2c_smbus_read_byte_data(client, command + i);
  		if (data < 0)
  			return data;
  		values[i] = data;
  	}
  	return i;
  }
  
  static s32 ds1307_read_block_data(const struct i2c_client *client, u8 command,
  				  u8 length, u8 *values)
  {
  	u8 oldvalues[255];
  	s32 ret;
  	int tries = 0;
  
  	dev_dbg(&client->dev, "ds1307_read_block_data (length=%d)
  ", length);
  	ret = ds1307_read_block_data_once(client, command, length, values);
  	if (ret < 0)
  		return ret;
  	do {
  		if (++tries > BLOCK_DATA_MAX_TRIES) {
  			dev_err(&client->dev,
  				"ds1307_read_block_data failed
  ");
  			return -EIO;
  		}
  		memcpy(oldvalues, values, length);
  		ret = ds1307_read_block_data_once(client, command, length,
  						  values);
  		if (ret < 0)
  			return ret;
  	} while (memcmp(oldvalues, values, length));
  	return length;
  }
  
  static s32 ds1307_write_block_data(const struct i2c_client *client, u8 command,
  				   u8 length, const u8 *values)
  {
  	u8 currvalues[255];
  	int tries = 0;
  
  	dev_dbg(&client->dev, "ds1307_write_block_data (length=%d)
  ", length);
  	do {
  		s32 i, ret;
  
  		if (++tries > BLOCK_DATA_MAX_TRIES) {
  			dev_err(&client->dev,
  				"ds1307_write_block_data failed
  ");
  			return -EIO;
  		}
  		for (i = 0; i < length; i++) {
  			ret = i2c_smbus_write_byte_data(client, command + i,
  							values[i]);
  			if (ret < 0)
  				return ret;
  		}
  		ret = ds1307_read_block_data_once(client, command, length,
  						  currvalues);
  		if (ret < 0)
  			return ret;
  	} while (memcmp(currvalues, values, length));
  	return length;
  }
  
  /*----------------------------------------------------------------------*/
  
  /* These RTC devices are not designed to be connected to a SMbus adapter.
     SMbus limits block operations length to 32 bytes, whereas it's not
     limited on I2C buses. As a result, accesses may exceed 32 bytes;
     in that case, split them into smaller blocks */
  
  static s32 ds1307_native_smbus_write_block_data(const struct i2c_client *client,
  				u8 command, u8 length, const u8 *values)
  {
  	u8 suboffset = 0;
  
  	if (length <= I2C_SMBUS_BLOCK_MAX)
  		return i2c_smbus_write_i2c_block_data(client,
  					command, length, values);
  
  	while (suboffset < length) {
  		s32 retval = i2c_smbus_write_i2c_block_data(client,
  				command + suboffset,
  				min(I2C_SMBUS_BLOCK_MAX, length - suboffset),
  				values + suboffset);
  		if (retval < 0)
  			return retval;
  
  		suboffset += I2C_SMBUS_BLOCK_MAX;
  	}
  	return length;
  }
  
  static s32 ds1307_native_smbus_read_block_data(const struct i2c_client *client,
  				u8 command, u8 length, u8 *values)
  {
  	u8 suboffset = 0;
  
  	if (length <= I2C_SMBUS_BLOCK_MAX)
  		return i2c_smbus_read_i2c_block_data(client,
  					command, length, values);
  
  	while (suboffset < length) {
  		s32 retval = i2c_smbus_read_i2c_block_data(client,
  				command + suboffset,
  				min(I2C_SMBUS_BLOCK_MAX, length - suboffset),
  				values + suboffset);
  		if (retval < 0)
  			return retval;
  
  		suboffset += I2C_SMBUS_BLOCK_MAX;
  	}
  	return length;
  }
  
  /*----------------------------------------------------------------------*/
  
  /*
   * The IRQ logic includes a "real" handler running in IRQ context just
   * long enough to schedule this workqueue entry.   We need a task context
   * to talk to the RTC, since I2C I/O calls require that; and disable the
   * IRQ until we clear its status on the chip, so that this handler can
   * work with any type of triggering (not just falling edge).
   *
   * The ds1337 and ds1339 both have two alarms, but we only use the first
   * one (with a "seconds" field).  For ds1337 we expect nINTA is our alarm
   * signal; ds1339 chips have only one alarm signal.
   */
  static void ds1307_work(struct work_struct *work)
  {
  	struct ds1307		*ds1307;
  	struct i2c_client	*client;
  	struct mutex		*lock;
  	int			stat, control;
  
  	ds1307 = container_of(work, struct ds1307, work);
  	client = ds1307->client;
  	lock = &ds1307->rtc->ops_lock;
  
  	mutex_lock(lock);
  	stat = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);
  	if (stat < 0)
  		goto out;
  
  	if (stat & DS1337_BIT_A1I) {
  		stat &= ~DS1337_BIT_A1I;
  		i2c_smbus_write_byte_data(client, DS1337_REG_STATUS, stat);
  
  		control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
  		if (control < 0)
  			goto out;
  
  		control &= ~DS1337_BIT_A1IE;
  		i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, control);
  
  		rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
  	}
  
  out:
  	if (test_bit(HAS_ALARM, &ds1307->flags))
  		enable_irq(client->irq);
  	mutex_unlock(lock);
  }
  
  static irqreturn_t ds1307_irq(int irq, void *dev_id)
  {
  	struct i2c_client	*client = dev_id;
  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  
  	disable_irq_nosync(irq);
  	schedule_work(&ds1307->work);
  	return IRQ_HANDLED;
  }
  
  /*----------------------------------------------------------------------*/
  
  static int ds1307_get_time(struct device *dev, struct rtc_time *t)
  {
  	struct ds1307	*ds1307 = dev_get_drvdata(dev);
  	int		tmp;
  
  	/* read the RTC date and time registers all at once */
  	tmp = ds1307->read_block_data(ds1307->client,
  		ds1307->offset, 7, ds1307->regs);
  	if (tmp != 7) {
  		dev_err(dev, "%s error %d
  ", "read", tmp);
  		return -EIO;
  	}
  
  	dev_dbg(dev, "%s: %7ph
  ", "read", ds1307->regs);
  
  	t->tm_sec = bcd2bin(ds1307->regs[DS1307_REG_SECS] & 0x7f);
  	t->tm_min = bcd2bin(ds1307->regs[DS1307_REG_MIN] & 0x7f);
  	tmp = ds1307->regs[DS1307_REG_HOUR] & 0x3f;
  	t->tm_hour = bcd2bin(tmp);
  	t->tm_wday = bcd2bin(ds1307->regs[DS1307_REG_WDAY] & 0x07) - 1;
  	t->tm_mday = bcd2bin(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
  	tmp = ds1307->regs[DS1307_REG_MONTH] & 0x1f;
  	t->tm_mon = bcd2bin(tmp) - 1;
  
  	/* assume 20YY not 19YY, and ignore DS1337_BIT_CENTURY */
  	t->tm_year = bcd2bin(ds1307->regs[DS1307_REG_YEAR]) + 100;
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d
  ",
  		"read", t->tm_sec, t->tm_min,
  		t->tm_hour, t->tm_mday,
  		t->tm_mon, t->tm_year, t->tm_wday);
  
  	/* initial clock setting can be undefined */
  	return rtc_valid_tm(t);
  }
  
  static int ds1307_set_time(struct device *dev, struct rtc_time *t)
  {
  	struct ds1307	*ds1307 = dev_get_drvdata(dev);
  	int		result;
  	int		tmp;
  	u8		*buf = ds1307->regs;
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d
  ",
  		"write", t->tm_sec, t->tm_min,
  		t->tm_hour, t->tm_mday,
  		t->tm_mon, t->tm_year, t->tm_wday);
  
  	buf[DS1307_REG_SECS] = bin2bcd(t->tm_sec);
  	buf[DS1307_REG_MIN] = bin2bcd(t->tm_min);
  	buf[DS1307_REG_HOUR] = bin2bcd(t->tm_hour);
  	buf[DS1307_REG_WDAY] = bin2bcd(t->tm_wday + 1);
  	buf[DS1307_REG_MDAY] = bin2bcd(t->tm_mday);
  	buf[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);
  
  	/* assume 20YY not 19YY */
  	tmp = t->tm_year - 100;
  	buf[DS1307_REG_YEAR] = bin2bcd(tmp);
  
  	switch (ds1307->type) {
  	case ds_1337:
  	case ds_1339:
  	case ds_3231:
  		buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;
  		break;
  	case ds_1340:
  		buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
  				| DS1340_BIT_CENTURY;
  		break;
  	case mcp7941x:
  		/*
  		 * these bits were cleared when preparing the date/time
  		 * values and need to be set again before writing the
  		 * buffer out to the device.
  		 */
  		buf[DS1307_REG_SECS] |= MCP7941X_BIT_ST;
  		buf[DS1307_REG_WDAY] |= MCP7941X_BIT_VBATEN;
  		break;
  	default:
  		break;
  	}
  
  	dev_dbg(dev, "%s: %7ph
  ", "write", buf);
  
  	result = ds1307->write_block_data(ds1307->client,
  		ds1307->offset, 7, buf);
  	if (result < 0) {
  		dev_err(dev, "%s error %d
  ", "write", result);
  		return result;
  	}
  	return 0;
  }
  
  static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)
  {
  	struct i2c_client       *client = to_i2c_client(dev);
  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  	int			ret;
  
  	if (!test_bit(HAS_ALARM, &ds1307->flags))
  		return -EINVAL;
  
  	/* read all ALARM1, ALARM2, and status registers at once */
  	ret = ds1307->read_block_data(client,
  			DS1339_REG_ALARM1_SECS, 9, ds1307->regs);
  	if (ret != 9) {
  		dev_err(dev, "%s error %d
  ", "alarm read", ret);
  		return -EIO;
  	}
  
  	dev_dbg(dev, "%s: %02x %02x %02x %02x, %02x %02x %02x, %02x %02x
  ",
  			"alarm read",
  			ds1307->regs[0], ds1307->regs[1],
  			ds1307->regs[2], ds1307->regs[3],
  			ds1307->regs[4], ds1307->regs[5],
  			ds1307->regs[6], ds1307->regs[7],
  			ds1307->regs[8]);
  
  	/*
  	 * report alarm time (ALARM1); assume 24 hour and day-of-month modes,
  	 * and that all four fields are checked matches
  	 */
  	t->time.tm_sec = bcd2bin(ds1307->regs[0] & 0x7f);
  	t->time.tm_min = bcd2bin(ds1307->regs[1] & 0x7f);
  	t->time.tm_hour = bcd2bin(ds1307->regs[2] & 0x3f);
  	t->time.tm_mday = bcd2bin(ds1307->regs[3] & 0x3f);
  	t->time.tm_mon = -1;
  	t->time.tm_year = -1;
  	t->time.tm_wday = -1;
  	t->time.tm_yday = -1;
  	t->time.tm_isdst = -1;
  
  	/* ... and status */
  	t->enabled = !!(ds1307->regs[7] & DS1337_BIT_A1IE);
  	t->pending = !!(ds1307->regs[8] & DS1337_BIT_A1I);
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, enabled=%d, pending=%d
  ",
  		"alarm read", t->time.tm_sec, t->time.tm_min,
  		t->time.tm_hour, t->time.tm_mday,
  		t->enabled, t->pending);
  
  	return 0;
  }
  
  static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t)
  {
  	struct i2c_client	*client = to_i2c_client(dev);
  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  	unsigned char		*buf = ds1307->regs;
  	u8			control, status;
  	int			ret;
  
  	if (!test_bit(HAS_ALARM, &ds1307->flags))
  		return -EINVAL;
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, enabled=%d, pending=%d
  ",
  		"alarm set", t->time.tm_sec, t->time.tm_min,
  		t->time.tm_hour, t->time.tm_mday,
  		t->enabled, t->pending);
  
  	/* read current status of both alarms and the chip */
  	ret = ds1307->read_block_data(client,
  			DS1339_REG_ALARM1_SECS, 9, buf);
  	if (ret != 9) {
  		dev_err(dev, "%s error %d
  ", "alarm write", ret);
  		return -EIO;
  	}
  	control = ds1307->regs[7];
  	status = ds1307->regs[8];
  
  	dev_dbg(dev, "%s: %02x %02x %02x %02x, %02x %02x %02x, %02x %02x
  ",
  			"alarm set (old status)",
  			ds1307->regs[0], ds1307->regs[1],
  			ds1307->regs[2], ds1307->regs[3],
  			ds1307->regs[4], ds1307->regs[5],
  			ds1307->regs[6], control, status);
  
  	/* set ALARM1, using 24 hour and day-of-month modes */
  	buf[0] = bin2bcd(t->time.tm_sec);
  	buf[1] = bin2bcd(t->time.tm_min);
  	buf[2] = bin2bcd(t->time.tm_hour);
  	buf[3] = bin2bcd(t->time.tm_mday);
  
  	/* set ALARM2 to non-garbage */
  	buf[4] = 0;
  	buf[5] = 0;
  	buf[6] = 0;
  
  	/* optionally enable ALARM1 */
  	buf[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
  	if (t->enabled) {
  		dev_dbg(dev, "alarm IRQ armed
  ");
  		buf[7] |= DS1337_BIT_A1IE;	/* only ALARM1 is used */
  	}
  	buf[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);
  
  	ret = ds1307->write_block_data(client,
  			DS1339_REG_ALARM1_SECS, 9, buf);
  	if (ret < 0) {
  		dev_err(dev, "can't set alarm time
  ");
  		return ret;
  	}
  
  	return 0;
  }
  
  static int ds1307_alarm_irq_enable(struct device *dev, unsigned int enabled)
  {
  	struct i2c_client	*client = to_i2c_client(dev);
  	struct ds1307		*ds1307 = i2c_get_clientdata(client);
  	int			ret;
  
  	if (!test_bit(HAS_ALARM, &ds1307->flags))
  		return -ENOTTY;
  
  	ret = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
  	if (ret < 0)
  		return ret;
  
  	if (enabled)
  		ret |= DS1337_BIT_A1IE;
  	else
  		ret &= ~DS1337_BIT_A1IE;
  
  	ret = i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, ret);
  	if (ret < 0)
  		return ret;
  
  	return 0;
  }
  
  static const struct rtc_class_ops ds13xx_rtc_ops = {
  	.read_time	= ds1307_get_time,
  	.set_time	= ds1307_set_time,
  	.read_alarm	= ds1337_read_alarm,
  	.set_alarm	= ds1337_set_alarm,
  	.alarm_irq_enable = ds1307_alarm_irq_enable,
  };
  
  /*----------------------------------------------------------------------*/
  
  static ssize_t
  ds1307_nvram_read(struct file *filp, struct kobject *kobj,
  		struct bin_attribute *attr,
  		char *buf, loff_t off, size_t count)
  {
  	struct i2c_client	*client;
  	struct ds1307		*ds1307;
  	int			result;
  
  	client = kobj_to_i2c_client(kobj);
  	ds1307 = i2c_get_clientdata(client);
  
  	if (unlikely(off >= ds1307->nvram->size))
  		return 0;
  	if ((off + count) > ds1307->nvram->size)
  		count = ds1307->nvram->size - off;
  	if (unlikely(!count))
  		return count;
  
  	result = ds1307->read_block_data(client, ds1307->nvram_offset + off,
  								count, buf);
  	if (result < 0)
  		dev_err(&client->dev, "%s error %d
  ", "nvram read", result);
  	return result;
  }
  
  static ssize_t
  ds1307_nvram_write(struct file *filp, struct kobject *kobj,
  		struct bin_attribute *attr,
  		char *buf, loff_t off, size_t count)
  {
  	struct i2c_client	*client;
  	struct ds1307		*ds1307;
  	int			result;
  
  	client = kobj_to_i2c_client(kobj);
  	ds1307 = i2c_get_clientdata(client);
  
  	if (unlikely(off >= ds1307->nvram->size))
  		return -EFBIG;
  	if ((off + count) > ds1307->nvram->size)
  		count = ds1307->nvram->size - off;
  	if (unlikely(!count))
  		return count;
  
  	result = ds1307->write_block_data(client, ds1307->nvram_offset + off,
  								count, buf);
  	if (result < 0) {
  		dev_err(&client->dev, "%s error %d
  ", "nvram write", result);
  		return result;
  	}
  	return count;
  }
  
  /*----------------------------------------------------------------------*/
  
  static int ds1307_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)
  {
  	struct ds1307		*ds1307;
  	int			err = -ENODEV;
  	int			tmp;
  	const struct chip_desc	*chip = &chips[id->driver_data];
  	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);
  	bool			want_irq = false;
  	unsigned char		*buf;
  	struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev);
  	static const int	bbsqi_bitpos[] = {
  		[ds_1337] = 0,
  		[ds_1339] = DS1339_BIT_BBSQI,
  		[ds_3231] = DS3231_BIT_BBSQW,
  	};
  
  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)
  	    && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_I2C_BLOCK))
  		return -EIO;
  
  	ds1307 = devm_kzalloc(&client->dev, sizeof(struct ds1307), GFP_KERNEL);
  	if (!ds1307)
  		return -ENOMEM;
  
  	i2c_set_clientdata(client, ds1307);
  
  	ds1307->client	= client;
  	ds1307->type	= id->driver_data;
  
  	if (pdata && pdata->trickle_charger_setup && chip->trickle_charger_reg)
  		i2c_smbus_write_byte_data(client, chip->trickle_charger_reg,
  			DS13XX_TRICKLE_CHARGER_MAGIC | pdata->trickle_charger_setup);
  
  	buf = ds1307->regs;
  	if (i2c_check_functionality(adapter, I2C_FUNC_SMBUS_I2C_BLOCK)) {
  		ds1307->read_block_data = ds1307_native_smbus_read_block_data;
  		ds1307->write_block_data = ds1307_native_smbus_write_block_data;
  	} else {
  		ds1307->read_block_data = ds1307_read_block_data;
  		ds1307->write_block_data = ds1307_write_block_data;
  	}
  
  	switch (ds1307->type) {
  	case ds_1337:
  	case ds_1339:
  	case ds_3231:
  		/* get registers that the "rtc" read below won't read... */
  		tmp = ds1307->read_block_data(ds1307->client,
  				DS1337_REG_CONTROL, 2, buf);
  		if (tmp != 2) {
  			dev_dbg(&client->dev, "read error %d
  ", tmp);
  			err = -EIO;
  			goto exit;
  		}
  
  		/* oscillator off?  turn it on, so clock can tick. */
  		if (ds1307->regs[0] & DS1337_BIT_nEOSC)
  			ds1307->regs[0] &= ~DS1337_BIT_nEOSC;
  
  		/*
  		 * Using IRQ?  Disable the square wave and both alarms.
  		 * For some variants, be sure alarms can trigger when we're
  		 * running on Vbackup (BBSQI/BBSQW)
  		 */
  		if (ds1307->client->irq > 0 && chip->alarm) {
  			INIT_WORK(&ds1307->work, ds1307_work);
  
  			ds1307->regs[0] |= DS1337_BIT_INTCN
  					| bbsqi_bitpos[ds1307->type];
  			ds1307->regs[0] &= ~(DS1337_BIT_A2IE | DS1337_BIT_A1IE);
  
  			want_irq = true;
  		}
  
  		i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL,
  							ds1307->regs[0]);
  
  		/* oscillator fault?  clear flag, and warn */
  		if (ds1307->regs[1] & DS1337_BIT_OSF) {
  			i2c_smbus_write_byte_data(client, DS1337_REG_STATUS,
  				ds1307->regs[1] & ~DS1337_BIT_OSF);
  			dev_warn(&client->dev, "SET TIME!
  ");
  		}
  		break;
  
  	case rx_8025:
  		tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
  				RX8025_REG_CTRL1 << 4 | 0x08, 2, buf);
  		if (tmp != 2) {
  			dev_dbg(&client->dev, "read error %d
  ", tmp);
  			err = -EIO;
  			goto exit;
  		}
  
  		/* oscillator off?  turn it on, so clock can tick. */
  		if (!(ds1307->regs[1] & RX8025_BIT_XST)) {
  			ds1307->regs[1] |= RX8025_BIT_XST;
  			i2c_smbus_write_byte_data(client,
  						  RX8025_REG_CTRL2 << 4 | 0x08,
  						  ds1307->regs[1]);
  			dev_warn(&client->dev,
  				 "oscillator stop detected - SET TIME!
  ");
  		}
  
  		if (ds1307->regs[1] & RX8025_BIT_PON) {
  			ds1307->regs[1] &= ~RX8025_BIT_PON;
  			i2c_smbus_write_byte_data(client,
  						  RX8025_REG_CTRL2 << 4 | 0x08,
  						  ds1307->regs[1]);
  			dev_warn(&client->dev, "power-on detected
  ");
  		}
  
  		if (ds1307->regs[1] & RX8025_BIT_VDET) {
  			ds1307->regs[1] &= ~RX8025_BIT_VDET;
  			i2c_smbus_write_byte_data(client,
  						  RX8025_REG_CTRL2 << 4 | 0x08,
  						  ds1307->regs[1]);
  			dev_warn(&client->dev, "voltage drop detected
  ");
  		}
  
  		/* make sure we are running in 24hour mode */
  		if (!(ds1307->regs[0] & RX8025_BIT_2412)) {
  			u8 hour;
  
  			/* switch to 24 hour mode */
  			i2c_smbus_write_byte_data(client,
  						  RX8025_REG_CTRL1 << 4 | 0x08,
  						  ds1307->regs[0] |
  						  RX8025_BIT_2412);
  
  			tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
  					RX8025_REG_CTRL1 << 4 | 0x08, 2, buf);
  			if (tmp != 2) {
  				dev_dbg(&client->dev, "read error %d
  ", tmp);
  				err = -EIO;
  				goto exit;
  			}
  
  			/* correct hour */
  			hour = bcd2bin(ds1307->regs[DS1307_REG_HOUR]);
  			if (hour == 12)
  				hour = 0;
  			if (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
  				hour += 12;
  
  			i2c_smbus_write_byte_data(client,
  						  DS1307_REG_HOUR << 4 | 0x08,
  						  hour);
  		}
  		break;
  	case ds_1388:
  		ds1307->offset = 1; /* Seconds starts at 1 */
  		break;
  	default:
  		break;
  	}
  
  read_rtc:
  	/* read RTC registers */
  	tmp = ds1307->read_block_data(ds1307->client, ds1307->offset, 8, buf);
  	if (tmp != 8) {
  		dev_dbg(&client->dev, "read error %d
  ", tmp);
  		err = -EIO;
  		goto exit;
  	}
  
  	/*
  	 * minimal sanity checking; some chips (like DS1340) don't
  	 * specify the extra bits as must-be-zero, but there are
  	 * still a few values that are clearly out-of-range.
  	 */
  	tmp = ds1307->regs[DS1307_REG_SECS];
  	switch (ds1307->type) {
  	case ds_1307:
  	case m41t00:
  		/* clock halted?  turn it on, so clock can tick. */
  		if (tmp & DS1307_BIT_CH) {
  			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
  			dev_warn(&client->dev, "SET TIME!
  ");
  			goto read_rtc;
  		}
  		break;
  	case ds_1338:
  		/* clock halted?  turn it on, so clock can tick. */
  		if (tmp & DS1307_BIT_CH)
  			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
  
  		/* oscillator fault?  clear flag, and warn */
  		if (ds1307->regs[DS1307_REG_CONTROL] & DS1338_BIT_OSF) {
  			i2c_smbus_write_byte_data(client, DS1307_REG_CONTROL,
  					ds1307->regs[DS1307_REG_CONTROL]
  					& ~DS1338_BIT_OSF);
  			dev_warn(&client->dev, "SET TIME!
  ");
  			goto read_rtc;
  		}
  		break;
  	case ds_1340:
  		/* clock halted?  turn it on, so clock can tick. */
  		if (tmp & DS1340_BIT_nEOSC)
  			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
  
  		tmp = i2c_smbus_read_byte_data(client, DS1340_REG_FLAG);
  		if (tmp < 0) {
  			dev_dbg(&client->dev, "read error %d
  ", tmp);
  			err = -EIO;
  			goto exit;
  		}
  
  		/* oscillator fault?  clear flag, and warn */
  		if (tmp & DS1340_BIT_OSF) {
  			i2c_smbus_write_byte_data(client, DS1340_REG_FLAG, 0);
  			dev_warn(&client->dev, "SET TIME!
  ");
  		}
  		break;
  	case mcp7941x:
  		/* make sure that the backup battery is enabled */
  		if (!(ds1307->regs[DS1307_REG_WDAY] & MCP7941X_BIT_VBATEN)) {
  			i2c_smbus_write_byte_data(client, DS1307_REG_WDAY,
  					ds1307->regs[DS1307_REG_WDAY]
  					| MCP7941X_BIT_VBATEN);
  		}
  
  		/* clock halted?  turn it on, so clock can tick. */
  		if (!(tmp & MCP7941X_BIT_ST)) {
  			i2c_smbus_write_byte_data(client, DS1307_REG_SECS,
  					MCP7941X_BIT_ST);
  			dev_warn(&client->dev, "SET TIME!
  ");
  			goto read_rtc;
  		}
  
  		break;
  	default:
  		break;
  	}
  
  	tmp = ds1307->regs[DS1307_REG_HOUR];
  	switch (ds1307->type) {
  	case ds_1340:
  	case m41t00:
  		/*
  		 * NOTE: ignores century bits; fix before deploying
  		 * systems that will run through year 2100.
  		 */
  		break;
  	case rx_8025:
  		break;
  	default:
  		if (!(tmp & DS1307_BIT_12HR))
  			break;
  
  		/*
  		 * Be sure we're in 24 hour mode.  Multi-master systems
  		 * take note...
  		 */
  		tmp = bcd2bin(tmp & 0x1f);
  		if (tmp == 12)
  			tmp = 0;
  		if (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
  			tmp += 12;
  		i2c_smbus_write_byte_data(client,
  				ds1307->offset + DS1307_REG_HOUR,
  				bin2bcd(tmp));
  	}
  
  	ds1307->rtc = devm_rtc_device_register(&client->dev, client->name,
  				&ds13xx_rtc_ops, THIS_MODULE);
  	if (IS_ERR(ds1307->rtc)) {
  		err = PTR_ERR(ds1307->rtc);
  		dev_err(&client->dev,
  			"unable to register the class device
  ");
  		goto exit;
  	}
  
  	if (want_irq) {
  		err = request_irq(client->irq, ds1307_irq, IRQF_SHARED,
  			  ds1307->rtc->name, client);
  		if (err) {
  			dev_err(&client->dev,
  				"unable to request IRQ!
  ");
  			goto exit;
  		}
  
  		device_set_wakeup_capable(&client->dev, 1);
  		set_bit(HAS_ALARM, &ds1307->flags);
  		dev_dbg(&client->dev, "got IRQ %d
  ", client->irq);
  	}
  
  	if (chip->nvram_size) {
  		ds1307->nvram = devm_kzalloc(&client->dev,
  					sizeof(struct bin_attribute),
  					GFP_KERNEL);
  		if (!ds1307->nvram) {
  			err = -ENOMEM;
  			goto err_irq;
  		}
  		ds1307->nvram->attr.name = "nvram";
  		ds1307->nvram->attr.mode = S_IRUGO | S_IWUSR;
  		sysfs_bin_attr_init(ds1307->nvram);
  		ds1307->nvram->read = ds1307_nvram_read;
  		ds1307->nvram->write = ds1307_nvram_write;
  		ds1307->nvram->size = chip->nvram_size;
  		ds1307->nvram_offset = chip->nvram_offset;
  		err = sysfs_create_bin_file(&client->dev.kobj, ds1307->nvram);
  		if (err)
  			goto err_irq;
  		set_bit(HAS_NVRAM, &ds1307->flags);
  		dev_info(&client->dev, "%zu bytes nvram
  ", ds1307->nvram->size);
  	}
  
  	return 0;
  
  err_irq:
  	free_irq(client->irq, client);
  exit:
  	return err;
  }
  
  static int ds1307_remove(struct i2c_client *client)
  {
  	struct ds1307 *ds1307 = i2c_get_clientdata(client);
  
  	if (test_and_clear_bit(HAS_ALARM, &ds1307->flags)) {
  		free_irq(client->irq, client);
  		cancel_work_sync(&ds1307->work);
  	}
  
  	if (test_and_clear_bit(HAS_NVRAM, &ds1307->flags))
  		sysfs_remove_bin_file(&client->dev.kobj, ds1307->nvram);
  
  	return 0;
  }
  
  static struct i2c_driver ds1307_driver = {
  	.driver = {
  		.name	= "rtc-ds1307",
  		.owner	= THIS_MODULE,
  	},
  	.probe		= ds1307_probe,
  	.remove		= ds1307_remove,
  	.id_table	= ds1307_id,
  };
  
  module_i2c_driver(ds1307_driver);
  
  MODULE_DESCRIPTION("RTC driver for DS1307 and similar chips");
  MODULE_LICENSE("GPL");