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32 results

ordered-data.c

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  • rtc-ds1307.c 41.41 KiB
    /*
     * 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/bcd.h>
    #include <linux/i2c.h>
    #include <linux/init.h>
    #include <linux/module.h>
    #include <linux/rtc/ds1307.h>
    #include <linux/rtc.h>
    #include <linux/slab.h>
    #include <linux/string.h>
    #include <linux/hwmon.h>
    #include <linux/hwmon-sysfs.h>
    #include <linux/clk-provider.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,
    	mcp794xx,
    	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 MCP794XX_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 MCP794XX_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 DS3231_BIT_EN32KHZ	0x08
    #	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;
    	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);
    #ifdef CONFIG_COMMON_CLK
    	struct clk_hw		clks[2];
    #endif
    };
    
    struct chip_desc {
    	unsigned		alarm:1;
    	u16			nvram_offset;
    	u16			nvram_size;
    	u16			trickle_charger_reg;
    	u8			trickle_charger_setup;
    	u8			(*do_trickle_setup)(struct i2c_client *, uint32_t, bool);
    };
    
    static u8 do_trickle_setup_ds1339(struct i2c_client *,
    				  uint32_t ohms, bool diode);
    
    static 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,
    		.do_trickle_setup = &do_trickle_setup_ds1339,
    	},
    	[ds_1340] = {
    		.trickle_charger_reg = 0x08,
    	},
    	[ds_1388] = {
    		.trickle_charger_reg = 0x0a,
    	},
    	[ds_3231] = {
    		.alarm		= 1,
    	},
    	[mcp794xx] = {
    		.alarm		= 1,
    		/* 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 },
    	{ "mcp7940x", mcp794xx },
    	{ "mcp7941x", mcp794xx },
    	{ "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)\n", 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\n");
    			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)\n", length);
    	do {
    		s32 i, ret;
    
    		if (++tries > BLOCK_DATA_MAX_TRIES) {
    			dev_err(&client->dev,
    				"ds1307_write_block_data failed\n");
    			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 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 irqreturn_t ds1307_irq(int irq, void *dev_id)
    {
    	struct i2c_client	*client = dev_id;
    	struct ds1307		*ds1307 = i2c_get_clientdata(client);
    	struct mutex		*lock = &ds1307->rtc->ops_lock;
    	int			stat, control;
    
    	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:
    	mutex_unlock(lock);
    
    	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\n", "read", tmp);
    		return -EIO;
    	}
    
    	dev_dbg(dev, "%s: %7ph\n", "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\n",
    		"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\n",
    		"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 mcp794xx:
    		/*
    		 * 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] |= MCP794XX_BIT_ST;
    		buf[DS1307_REG_WDAY] |= MCP794XX_BIT_VBATEN;
    		break;
    	default:
    		break;
    	}
    
    	dev_dbg(dev, "%s: %7ph\n", "write", buf);
    
    	result = ds1307->write_block_data(ds1307->client,
    		ds1307->offset, 7, buf);
    	if (result < 0) {
    		dev_err(dev, "%s error %d\n", "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\n", "alarm read", ret);
    		return -EIO;
    	}
    
    	dev_dbg(dev, "%s: %4ph, %3ph, %2ph\n", "alarm read",
    		&ds1307->regs[0], &ds1307->regs[4], &ds1307->regs[7]);
    
    	/*
    	 * 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\n",
    		"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\n",
    		"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\n", "alarm write", ret);
    		return -EIO;
    	}
    	control = ds1307->regs[7];
    	status = ds1307->regs[8];
    
    	dev_dbg(dev, "%s: %4ph, %3ph, %02x %02x\n", "alarm set (old status)",
    		&ds1307->regs[0], &ds1307->regs[4], 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\n");
    		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\n");
    		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,
    };
    
    /*----------------------------------------------------------------------*/
    
    /*
     * Alarm support for mcp794xx devices.
     */
    
    #define MCP794XX_REG_CONTROL		0x07
    #	define MCP794XX_BIT_ALM0_EN	0x10
    #	define MCP794XX_BIT_ALM1_EN	0x20
    #define MCP794XX_REG_ALARM0_BASE	0x0a
    #define MCP794XX_REG_ALARM0_CTRL	0x0d
    #define MCP794XX_REG_ALARM1_BASE	0x11
    #define MCP794XX_REG_ALARM1_CTRL	0x14
    #	define MCP794XX_BIT_ALMX_IF	(1 << 3)
    #	define MCP794XX_BIT_ALMX_C0	(1 << 4)
    #	define MCP794XX_BIT_ALMX_C1	(1 << 5)
    #	define MCP794XX_BIT_ALMX_C2	(1 << 6)
    #	define MCP794XX_BIT_ALMX_POL	(1 << 7)
    #	define MCP794XX_MSK_ALMX_MATCH	(MCP794XX_BIT_ALMX_C0 | \
    					 MCP794XX_BIT_ALMX_C1 | \
    					 MCP794XX_BIT_ALMX_C2)
    
    static irqreturn_t mcp794xx_irq(int irq, void *dev_id)
    {
    	struct i2c_client       *client = dev_id;
    	struct ds1307           *ds1307 = i2c_get_clientdata(client);
    	struct mutex            *lock = &ds1307->rtc->ops_lock;
    	int reg, ret;
    
    	mutex_lock(lock);
    
    	/* Check and clear alarm 0 interrupt flag. */
    	reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_ALARM0_CTRL);
    	if (reg < 0)
    		goto out;
    	if (!(reg & MCP794XX_BIT_ALMX_IF))
    		goto out;
    	reg &= ~MCP794XX_BIT_ALMX_IF;
    	ret = i2c_smbus_write_byte_data(client, MCP794XX_REG_ALARM0_CTRL, reg);
    	if (ret < 0)
    		goto out;
    
    	/* Disable alarm 0. */
    	reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_CONTROL);
    	if (reg < 0)
    		goto out;
    	reg &= ~MCP794XX_BIT_ALM0_EN;
    	ret = i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, reg);
    	if (ret < 0)
    		goto out;
    
    	rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
    
    out:
    	mutex_unlock(lock);
    
    	return IRQ_HANDLED;
    }
    
    static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t)
    {
    	struct i2c_client *client = to_i2c_client(dev);
    	struct ds1307 *ds1307 = i2c_get_clientdata(client);
    	u8 *regs = ds1307->regs;
    	int ret;
    
    	if (!test_bit(HAS_ALARM, &ds1307->flags))
    		return -EINVAL;
    
    	/* Read control and alarm 0 registers. */
    	ret = ds1307->read_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
    	if (ret < 0)
    		return ret;
    
    	t->enabled = !!(regs[0] & MCP794XX_BIT_ALM0_EN);
    
    	/* Report alarm 0 time assuming 24-hour and day-of-month modes. */
    	t->time.tm_sec = bcd2bin(ds1307->regs[3] & 0x7f);
    	t->time.tm_min = bcd2bin(ds1307->regs[4] & 0x7f);
    	t->time.tm_hour = bcd2bin(ds1307->regs[5] & 0x3f);
    	t->time.tm_wday = bcd2bin(ds1307->regs[6] & 0x7) - 1;
    	t->time.tm_mday = bcd2bin(ds1307->regs[7] & 0x3f);
    	t->time.tm_mon = bcd2bin(ds1307->regs[8] & 0x1f) - 1;
    	t->time.tm_year = -1;
    	t->time.tm_yday = -1;
    	t->time.tm_isdst = -1;
    
    	dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
    		"enabled=%d polarity=%d irq=%d match=%d\n", __func__,
    		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
    		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon, t->enabled,
    		!!(ds1307->regs[6] & MCP794XX_BIT_ALMX_POL),
    		!!(ds1307->regs[6] & MCP794XX_BIT_ALMX_IF),
    		(ds1307->regs[6] & MCP794XX_MSK_ALMX_MATCH) >> 4);
    
    	return 0;
    }
    
    static int mcp794xx_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 *regs = ds1307->regs;
    	int ret;
    
    	if (!test_bit(HAS_ALARM, &ds1307->flags))
    		return -EINVAL;
    
    	dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
    		"enabled=%d pending=%d\n", __func__,
    		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
    		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon,
    		t->enabled, t->pending);
    
    	/* Read control and alarm 0 registers. */
    	ret = ds1307->read_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
    	if (ret < 0)
    		return ret;
    
    	/* Set alarm 0, using 24-hour and day-of-month modes. */
    	regs[3] = bin2bcd(t->time.tm_sec);
    	regs[4] = bin2bcd(t->time.tm_min);
    	regs[5] = bin2bcd(t->time.tm_hour);
    	regs[6] = bin2bcd(t->time.tm_wday + 1);
    	regs[7] = bin2bcd(t->time.tm_mday);
    	regs[8] = bin2bcd(t->time.tm_mon + 1);
    
    	/* Clear the alarm 0 interrupt flag. */
    	regs[6] &= ~MCP794XX_BIT_ALMX_IF;
    	/* Set alarm match: second, minute, hour, day, date, month. */
    	regs[6] |= MCP794XX_MSK_ALMX_MATCH;
    	/* Disable interrupt. We will not enable until completely programmed */
    	regs[0] &= ~MCP794XX_BIT_ALM0_EN;
    
    	ret = ds1307->write_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
    	if (ret < 0)
    		return ret;
    
    	if (!t->enabled)
    		return 0;
    	regs[0] |= MCP794XX_BIT_ALM0_EN;
    	return i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, regs[0]);
    }
    
    static int mcp794xx_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 reg;
    
    	if (!test_bit(HAS_ALARM, &ds1307->flags))
    		return -EINVAL;
    
    	reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_CONTROL);
    	if (reg < 0)
    		return reg;
    
    	if (enabled)
    		reg |= MCP794XX_BIT_ALM0_EN;
    	else
    		reg &= ~MCP794XX_BIT_ALM0_EN;
    
    	return i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, reg);
    }
    
    static const struct rtc_class_ops mcp794xx_rtc_ops = {
    	.read_time	= ds1307_get_time,
    	.set_time	= ds1307_set_time,
    	.read_alarm	= mcp794xx_read_alarm,
    	.set_alarm	= mcp794xx_set_alarm,
    	.alarm_irq_enable = mcp794xx_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);
    
    	result = ds1307->read_block_data(client, ds1307->nvram_offset + off,
    								count, buf);
    	if (result < 0)
    		dev_err(&client->dev, "%s error %d\n", "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);
    
    	result = ds1307->write_block_data(client, ds1307->nvram_offset + off,
    								count, buf);
    	if (result < 0) {
    		dev_err(&client->dev, "%s error %d\n", "nvram write", result);
    		return result;
    	}
    	return count;
    }
    
    
    /*----------------------------------------------------------------------*/
    
    static u8 do_trickle_setup_ds1339(struct i2c_client *client,
    				  uint32_t ohms, bool diode)
    {
    	u8 setup = (diode) ? DS1307_TRICKLE_CHARGER_DIODE :
    		DS1307_TRICKLE_CHARGER_NO_DIODE;
    
    	switch (ohms) {
    	case 250:
    		setup |= DS1307_TRICKLE_CHARGER_250_OHM;
    		break;
    	case 2000:
    		setup |= DS1307_TRICKLE_CHARGER_2K_OHM;
    		break;
    	case 4000:
    		setup |= DS1307_TRICKLE_CHARGER_4K_OHM;
    		break;
    	default:
    		dev_warn(&client->dev,
    			 "Unsupported ohm value %u in dt\n", ohms);
    		return 0;
    	}
    	return setup;
    }
    
    static void ds1307_trickle_of_init(struct i2c_client *client,
    				   struct chip_desc *chip)
    {
    	uint32_t ohms = 0;
    	bool diode = true;
    
    	if (!chip->do_trickle_setup)
    		goto out;
    	if (of_property_read_u32(client->dev.of_node, "trickle-resistor-ohms" , &ohms))
    		goto out;
    	if (of_property_read_bool(client->dev.of_node, "trickle-diode-disable"))
    		diode = false;
    	chip->trickle_charger_setup = chip->do_trickle_setup(client,
    							     ohms, diode);
    out:
    	return;
    }
    
    /*----------------------------------------------------------------------*/
    
    #ifdef CONFIG_RTC_DRV_DS1307_HWMON
    
    /*
     * Temperature sensor support for ds3231 devices.
     */
    
    #define DS3231_REG_TEMPERATURE	0x11
    
    /*
     * A user-initiated temperature conversion is not started by this function,
     * so the temperature is updated once every 64 seconds.
     */
    static int ds3231_hwmon_read_temp(struct device *dev, s16 *mC)
    {
    	struct ds1307 *ds1307 = dev_get_drvdata(dev);
    	u8 temp_buf[2];
    	s16 temp;
    	int ret;
    
    	ret = ds1307->read_block_data(ds1307->client, DS3231_REG_TEMPERATURE,
    					sizeof(temp_buf), temp_buf);
    	if (ret < 0)
    		return ret;
    	if (ret != sizeof(temp_buf))
    		return -EIO;
    
    	/*
    	 * Temperature is represented as a 10-bit code with a resolution of
    	 * 0.25 degree celsius and encoded in two's complement format.
    	 */
    	temp = (temp_buf[0] << 8) | temp_buf[1];
    	temp >>= 6;
    	*mC = temp * 250;
    
    	return 0;
    }
    
    static ssize_t ds3231_hwmon_show_temp(struct device *dev,
    				struct device_attribute *attr, char *buf)
    {
    	int ret;
    	s16 temp;
    
    	ret = ds3231_hwmon_read_temp(dev, &temp);
    	if (ret)
    		return ret;
    
    	return sprintf(buf, "%d\n", temp);
    }
    static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, ds3231_hwmon_show_temp,
    			NULL, 0);
    
    static struct attribute *ds3231_hwmon_attrs[] = {
    	&sensor_dev_attr_temp1_input.dev_attr.attr,
    	NULL,
    };
    ATTRIBUTE_GROUPS(ds3231_hwmon);
    
    static void ds1307_hwmon_register(struct ds1307 *ds1307)
    {
    	struct device *dev;
    
    	if (ds1307->type != ds_3231)
    		return;
    
    	dev = devm_hwmon_device_register_with_groups(&ds1307->client->dev,
    						ds1307->client->name,
    						ds1307, ds3231_hwmon_groups);
    	if (IS_ERR(dev)) {
    		dev_warn(&ds1307->client->dev,
    			"unable to register hwmon device %ld\n", PTR_ERR(dev));
    	}
    }
    
    #else
    
    static void ds1307_hwmon_register(struct ds1307 *ds1307)
    {
    }
    
    #endif /* CONFIG_RTC_DRV_DS1307_HWMON */
    
    /*----------------------------------------------------------------------*/
    
    /*
     * Square-wave output support for DS3231
     * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS3231.pdf
     */
    #ifdef CONFIG_COMMON_CLK
    
    enum {
    	DS3231_CLK_SQW = 0,
    	DS3231_CLK_32KHZ,
    };
    
    #define clk_sqw_to_ds1307(clk)	\
    	container_of(clk, struct ds1307, clks[DS3231_CLK_SQW])
    #define clk_32khz_to_ds1307(clk)	\
    	container_of(clk, struct ds1307, clks[DS3231_CLK_32KHZ])
    
    static int ds3231_clk_sqw_rates[] = {
    	1,
    	1024,
    	4096,
    	8192,
    };
    
    static int ds1337_write_control(struct ds1307 *ds1307, u8 mask, u8 value)
    {
    	struct i2c_client *client = ds1307->client;
    	struct mutex *lock = &ds1307->rtc->ops_lock;
    	int control;
    	int ret;
    
    	mutex_lock(lock);
    
    	control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
    	if (control < 0) {
    		ret = control;
    		goto out;
    	}
    
    	control &= ~mask;
    	control |= value;
    
    	ret = i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, control);
    out:
    	mutex_unlock(lock);
    
    	return ret;
    }
    
    static unsigned long ds3231_clk_sqw_recalc_rate(struct clk_hw *hw,
    						unsigned long parent_rate)
    {
    	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
    	int control;
    	int rate_sel = 0;
    
    	control = i2c_smbus_read_byte_data(ds1307->client, DS1337_REG_CONTROL);
    	if (control < 0)
    		return control;
    	if (control & DS1337_BIT_RS1)
    		rate_sel += 1;
    	if (control & DS1337_BIT_RS2)
    		rate_sel += 2;
    
    	return ds3231_clk_sqw_rates[rate_sel];
    }
    
    static long ds3231_clk_sqw_round_rate(struct clk_hw *hw, unsigned long rate,
    					unsigned long *prate)
    {
    	int i;
    
    	for (i = ARRAY_SIZE(ds3231_clk_sqw_rates) - 1; i >= 0; i--) {
    		if (ds3231_clk_sqw_rates[i] <= rate)
    			return ds3231_clk_sqw_rates[i];
    	}
    
    	return 0;
    }
    
    static int ds3231_clk_sqw_set_rate(struct clk_hw *hw, unsigned long rate,
    					unsigned long parent_rate)
    {
    	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
    	int control = 0;
    	int rate_sel;
    
    	for (rate_sel = 0; rate_sel < ARRAY_SIZE(ds3231_clk_sqw_rates);
    			rate_sel++) {
    		if (ds3231_clk_sqw_rates[rate_sel] == rate)
    			break;
    	}
    
    	if (rate_sel == ARRAY_SIZE(ds3231_clk_sqw_rates))
    		return -EINVAL;
    
    	if (rate_sel & 1)
    		control |= DS1337_BIT_RS1;
    	if (rate_sel & 2)
    		control |= DS1337_BIT_RS2;
    
    	return ds1337_write_control(ds1307, DS1337_BIT_RS1 | DS1337_BIT_RS2,
    				control);
    }
    
    static int ds3231_clk_sqw_prepare(struct clk_hw *hw)
    {
    	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
    
    	return ds1337_write_control(ds1307, DS1337_BIT_INTCN, 0);
    }
    
    static void ds3231_clk_sqw_unprepare(struct clk_hw *hw)
    {
    	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
    
    	ds1337_write_control(ds1307, DS1337_BIT_INTCN, DS1337_BIT_INTCN);
    }
    
    static int ds3231_clk_sqw_is_prepared(struct clk_hw *hw)
    {
    	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
    	int control;
    
    	control = i2c_smbus_read_byte_data(ds1307->client, DS1337_REG_CONTROL);
    	if (control < 0)
    		return control;
    
    	return !(control & DS1337_BIT_INTCN);
    }
    
    static const struct clk_ops ds3231_clk_sqw_ops = {
    	.prepare = ds3231_clk_sqw_prepare,
    	.unprepare = ds3231_clk_sqw_unprepare,
    	.is_prepared = ds3231_clk_sqw_is_prepared,
    	.recalc_rate = ds3231_clk_sqw_recalc_rate,
    	.round_rate = ds3231_clk_sqw_round_rate,
    	.set_rate = ds3231_clk_sqw_set_rate,
    };
    
    static unsigned long ds3231_clk_32khz_recalc_rate(struct clk_hw *hw,
    						unsigned long parent_rate)
    {
    	return 32768;
    }
    
    static int ds3231_clk_32khz_control(struct ds1307 *ds1307, bool enable)
    {
    	struct i2c_client *client = ds1307->client;
    	struct mutex *lock = &ds1307->rtc->ops_lock;
    	int status;
    	int ret;
    
    	mutex_lock(lock);
    
    	status = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);
    	if (status < 0) {
    		ret = status;
    		goto out;
    	}
    
    	if (enable)
    		status |= DS3231_BIT_EN32KHZ;
    	else
    		status &= ~DS3231_BIT_EN32KHZ;
    
    	ret = i2c_smbus_write_byte_data(client, DS1337_REG_STATUS, status);
    out:
    	mutex_unlock(lock);
    
    	return ret;
    }
    
    static int ds3231_clk_32khz_prepare(struct clk_hw *hw)
    {
    	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);
    
    	return ds3231_clk_32khz_control(ds1307, true);
    }
    
    static void ds3231_clk_32khz_unprepare(struct clk_hw *hw)
    {
    	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);
    
    	ds3231_clk_32khz_control(ds1307, false);
    }
    
    static int ds3231_clk_32khz_is_prepared(struct clk_hw *hw)
    {
    	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);
    	int status;
    
    	status = i2c_smbus_read_byte_data(ds1307->client, DS1337_REG_STATUS);
    	if (status < 0)
    		return status;
    
    	return !!(status & DS3231_BIT_EN32KHZ);
    }
    
    static const struct clk_ops ds3231_clk_32khz_ops = {
    	.prepare = ds3231_clk_32khz_prepare,
    	.unprepare = ds3231_clk_32khz_unprepare,
    	.is_prepared = ds3231_clk_32khz_is_prepared,
    	.recalc_rate = ds3231_clk_32khz_recalc_rate,
    };
    
    static struct clk_init_data ds3231_clks_init[] = {
    	[DS3231_CLK_SQW] = {
    		.name = "ds3231_clk_sqw",
    		.ops = &ds3231_clk_sqw_ops,
    		.flags = CLK_IS_ROOT,
    	},
    	[DS3231_CLK_32KHZ] = {
    		.name = "ds3231_clk_32khz",
    		.ops = &ds3231_clk_32khz_ops,
    		.flags = CLK_IS_ROOT,
    	},
    };
    
    static int ds3231_clks_register(struct ds1307 *ds1307)
    {
    	struct i2c_client *client = ds1307->client;
    	struct device_node *node = client->dev.of_node;
    	struct clk_onecell_data	*onecell;
    	int i;
    
    	onecell = devm_kzalloc(&client->dev, sizeof(*onecell), GFP_KERNEL);
    	if (!onecell)
    		return -ENOMEM;
    
    	onecell->clk_num = ARRAY_SIZE(ds3231_clks_init);
    	onecell->clks = devm_kcalloc(&client->dev, onecell->clk_num,
    					sizeof(onecell->clks[0]), GFP_KERNEL);
    	if (!onecell->clks)
    		return -ENOMEM;
    
    	for (i = 0; i < ARRAY_SIZE(ds3231_clks_init); i++) {
    		struct clk_init_data init = ds3231_clks_init[i];
    
    		/*
    		 * Interrupt signal due to alarm conditions and square-wave
    		 * output share same pin, so don't initialize both.
    		 */
    		if (i == DS3231_CLK_SQW && test_bit(HAS_ALARM, &ds1307->flags))
    			continue;
    
    		/* optional override of the clockname */
    		of_property_read_string_index(node, "clock-output-names", i,
    						&init.name);
    		ds1307->clks[i].init = &init;
    
    		onecell->clks[i] = devm_clk_register(&client->dev,
    							&ds1307->clks[i]);
    		if (IS_ERR(onecell->clks[i]))
    			return PTR_ERR(onecell->clks[i]);
    	}
    
    	if (!node)
    		return 0;
    
    	of_clk_add_provider(node, of_clk_src_onecell_get, onecell);
    
    	return 0;
    }
    
    static void ds1307_clks_register(struct ds1307 *ds1307)
    {
    	int ret;
    
    	if (ds1307->type != ds_3231)
    		return;
    
    	ret = ds3231_clks_register(ds1307);
    	if (ret) {
    		dev_warn(&ds1307->client->dev,
    			"unable to register clock device %d\n", ret);
    	}
    }
    
    #else
    
    static void ds1307_clks_register(struct ds1307 *ds1307)
    {
    }
    
    #endif /* CONFIG_COMMON_CLK */
    
    static int ds1307_probe(struct i2c_client *client,
    			const struct i2c_device_id *id)
    {
    	struct ds1307		*ds1307;
    	int			err = -ENODEV;
    	int			tmp;
    	struct chip_desc	*chip = &chips[id->driver_data];
    	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);
    	bool			want_irq = false;
    	bool			ds1307_can_wakeup_device = false;
    	unsigned char		*buf;
    	struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev);
    	irq_handler_t	irq_handler = ds1307_irq;
    
    	static const int	bbsqi_bitpos[] = {
    		[ds_1337] = 0,
    		[ds_1339] = DS1339_BIT_BBSQI,
    		[ds_3231] = DS3231_BIT_BBSQW,
    	};
    	const struct rtc_class_ops *rtc_ops = &ds13xx_rtc_ops;
    
    	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 && client->dev.of_node)
    		ds1307_trickle_of_init(client, chip);
    	else if (pdata && pdata->trickle_charger_setup)
    		chip->trickle_charger_setup = pdata->trickle_charger_setup;
    
    	if (chip->trickle_charger_setup && chip->trickle_charger_reg) {
    		dev_dbg(&client->dev, "writing trickle charger info 0x%x to 0x%x\n",
    		    DS13XX_TRICKLE_CHARGER_MAGIC | chip->trickle_charger_setup,
    		    chip->trickle_charger_reg);
    		i2c_smbus_write_byte_data(client, chip->trickle_charger_reg,
    		    DS13XX_TRICKLE_CHARGER_MAGIC |
    		    chip->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;
    	}
    
    #ifdef CONFIG_OF
    /*
     * For devices with no IRQ directly connected to the SoC, the RTC chip
     * can be forced as a wakeup source by stating that explicitly in
     * the device's .dts file using the "wakeup-source" boolean property.
     * If the "wakeup-source" property is set, don't request an IRQ.
     * This will guarantee the 'wakealarm' sysfs entry is available on the device,
     * if supported by the RTC.
     */
    	if (of_property_read_bool(client->dev.of_node, "wakeup-source")) {
    		ds1307_can_wakeup_device = true;
    	}
    #endif
    
    	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\n", 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 or defined as wakeup-source?
    		 * Disable the square wave and both alarms.
    		 * For some variants, be sure alarms can trigger when we're
    		 * running on Vbackup (BBSQI/BBSQW)
    		 */
    		if (chip->alarm && (ds1307->client->irq > 0 ||
    						ds1307_can_wakeup_device)) {
    			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!\n");
    		}
    		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\n", 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!\n");
    		}
    
    		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\n");
    		}
    
    		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\n");
    		}
    
    		/* 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\n", 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;
    	case mcp794xx:
    		rtc_ops = &mcp794xx_rtc_ops;
    		if (ds1307->client->irq > 0 && chip->alarm) {
    			irq_handler = mcp794xx_irq;
    			want_irq = true;
    		}
    		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\n", 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!\n");
    			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!\n");
    			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\n", 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!\n");
    		}
    		break;
    	case mcp794xx:
    		/* make sure that the backup battery is enabled */
    		if (!(ds1307->regs[DS1307_REG_WDAY] & MCP794XX_BIT_VBATEN)) {
    			i2c_smbus_write_byte_data(client, DS1307_REG_WDAY,
    					ds1307->regs[DS1307_REG_WDAY]
    					| MCP794XX_BIT_VBATEN);
    		}
    
    		/* clock halted?  turn it on, so clock can tick. */
    		if (!(tmp & MCP794XX_BIT_ST)) {
    			i2c_smbus_write_byte_data(client, DS1307_REG_SECS,
    					MCP794XX_BIT_ST);
    			dev_warn(&client->dev, "SET TIME!\n");
    			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));
    	}
    
    	if (want_irq) {
    		device_set_wakeup_capable(&client->dev, true);
    		set_bit(HAS_ALARM, &ds1307->flags);
    	}
    	ds1307->rtc = devm_rtc_device_register(&client->dev, client->name,
    				rtc_ops, THIS_MODULE);
    	if (IS_ERR(ds1307->rtc)) {
    		return PTR_ERR(ds1307->rtc);
    	}
    
    	if (ds1307_can_wakeup_device) {
    		/* Disable request for an IRQ */
    		want_irq = false;
    		dev_info(&client->dev, "'wakeup-source' is set, request for an IRQ is disabled!\n");
    		/* We cannot support UIE mode if we do not have an IRQ line */
    		ds1307->rtc->uie_unsupported = 1;
    	}
    
    	if (want_irq) {
    		err = devm_request_threaded_irq(&client->dev,
    						client->irq, NULL, irq_handler,
    						IRQF_SHARED | IRQF_ONESHOT,
    						ds1307->rtc->name, client);
    		if (err) {
    			client->irq = 0;
    			device_set_wakeup_capable(&client->dev, false);
    			clear_bit(HAS_ALARM, &ds1307->flags);
    			dev_err(&client->dev, "unable to request IRQ!\n");
    		} else
    			dev_dbg(&client->dev, "got IRQ %d\n", client->irq);
    	}
    
    	if (chip->nvram_size) {
    
    		ds1307->nvram = devm_kzalloc(&client->dev,
    					sizeof(struct bin_attribute),
    					GFP_KERNEL);
    		if (!ds1307->nvram) {
    			dev_err(&client->dev, "cannot allocate memory for nvram sysfs\n");
    		} else {
    
    			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) {
    				dev_err(&client->dev,
    					"unable to create sysfs file: %s\n",
    					ds1307->nvram->attr.name);
    			} else {
    				set_bit(HAS_NVRAM, &ds1307->flags);
    				dev_info(&client->dev, "%zu bytes nvram\n",
    					 ds1307->nvram->size);
    			}
    		}
    	}
    
    	ds1307_hwmon_register(ds1307);
    	ds1307_clks_register(ds1307);
    
    	return 0;
    
    exit:
    	return err;
    }
    
    static int ds1307_remove(struct i2c_client *client)
    {
    	struct ds1307 *ds1307 = i2c_get_clientdata(client);
    
    	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",
    	},
    	.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");