drivers/rtc/ds1307.c - github/trini/u-boot - Gitiles

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * (C) Copyright 2001, 2002, 2003
  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
  * Keith Outwater, keith_outwater@mvis.com`
  * Steven Scholz, steven.scholz@imc-berlin.de
  */

 /*
  * Date & Time support (no alarms) for Dallas Semiconductor (now Maxim)
  * DS1307 and DS1338/9 Real Time Clock (RTC).
  *
  * based on ds1337.c
  */

 #include <config.h>
 #include <command.h>
 #include <dm.h>
 #include <log.h>
 #include <rtc.h>
 #include <i2c.h>

 enum ds_type {
 	ds_1307,
 	ds_1337,
 	ds_1339,
 	ds_1340,
 	m41t11,
 	mcp794xx,
 };

 /*
  * RTC register addresses
  */
 #define RTC_SEC_REG_ADDR	0x00
 #define RTC_MIN_REG_ADDR	0x01
 #define RTC_HR_REG_ADDR		0x02
 #define RTC_DAY_REG_ADDR	0x03
 #define RTC_DATE_REG_ADDR	0x04
 #define RTC_MON_REG_ADDR	0x05
 #define RTC_YR_REG_ADDR		0x06
 #define RTC_CTL_REG_ADDR	0x07

 #define DS1337_CTL_REG_ADDR	0x0e
 #define DS1337_STAT_REG_ADDR	0x0f
 #define DS1340_STAT_REG_ADDR	0x09

 #define RTC_STAT_BIT_OSF	0x80

 #define RTC_SEC_BIT_CH		0x80	/* Clock Halt (in Register 0)   */

 /* DS1307-specific bits */
 #define RTC_CTL_BIT_RS0		0x01	/* Rate select 0                */
 #define RTC_CTL_BIT_RS1		0x02	/* Rate select 1                */
 #define RTC_CTL_BIT_SQWE	0x10	/* Square Wave Enable           */
 #define RTC_CTL_BIT_OUT		0x80	/* Output Control               */

 /* DS1337-specific bits */
 #define DS1337_CTL_BIT_RS1	0x08	/* Rate select 1                */
 #define DS1337_CTL_BIT_RS2	0x10	/* Rate select 2                */
 #define DS1337_CTL_BIT_EOSC	0x80	/* Enable Oscillator            */

 /* DS1340-specific bits */
 #define DS1340_SEC_BIT_EOSC	0x80	/* Enable Oscillator            */
 #define DS1340_CTL_BIT_OUT	0x80	/* Output Control               */

 /* MCP7941X-specific bits */
 #define MCP7941X_BIT_ST		0x80
 #define MCP7941X_BIT_VBATEN	0x08

 #ifndef CONFIG_DM_RTC

 /*---------------------------------------------------------------------*/
 #undef DEBUG_RTC

 #ifdef DEBUG_RTC
 #define DEBUGR(fmt, args...) printf(fmt, ##args)
 #else
 #define DEBUGR(fmt, args...)
 #endif
 /*---------------------------------------------------------------------*/

 #ifndef CFG_SYS_I2C_RTC_ADDR
 # define CFG_SYS_I2C_RTC_ADDR	0x68
 #endif

 #if defined(CONFIG_RTC_DS1307) && (CONFIG_SYS_I2C_SPEED > 100000)
 # error The DS1307 is specified only up to 100kHz!
 #endif

 static uchar rtc_read (uchar reg);
 static void rtc_write (uchar reg, uchar val);

 /*
  * Get the current time from the RTC
  */
 int rtc_get (struct rtc_time *tmp)
 {
 	int rel = 0;
 	uchar sec, min, hour, mday, wday, mon, year;

 #ifdef CONFIG_RTC_MCP79411
 read_rtc:
 #endif
 	sec = rtc_read (RTC_SEC_REG_ADDR);
 	min = rtc_read (RTC_MIN_REG_ADDR);
 	hour = rtc_read (RTC_HR_REG_ADDR);
 	wday = rtc_read (RTC_DAY_REG_ADDR);
 	mday = rtc_read (RTC_DATE_REG_ADDR);
 	mon = rtc_read (RTC_MON_REG_ADDR);
 	year = rtc_read (RTC_YR_REG_ADDR);

 	DEBUGR ("Get RTC year: %02x mon: %02x mday: %02x wday: %02x "
 		"hr: %02x min: %02x sec: %02x\n",
 		year, mon, mday, wday, hour, min, sec);

 #ifdef CONFIG_RTC_DS1307
 	if (sec & RTC_SEC_BIT_CH) {
 		printf ("### Warning: RTC oscillator has stopped\n");
 		/* clear the CH flag */
 		rtc_write (RTC_SEC_REG_ADDR,
 			   rtc_read (RTC_SEC_REG_ADDR) & ~RTC_SEC_BIT_CH);
 		rel = -1;
 	}
 #endif

 #ifdef CONFIG_RTC_MCP79411
 	/* make sure that the backup battery is enabled */
 	if (!(wday & MCP7941X_BIT_VBATEN)) {
 		rtc_write(RTC_DAY_REG_ADDR,
 			  wday | MCP7941X_BIT_VBATEN);
 	}

 	/* clock halted?  turn it on, so clock can tick. */
 	if (!(sec & MCP7941X_BIT_ST)) {
 		rtc_write(RTC_SEC_REG_ADDR, MCP7941X_BIT_ST);
 		printf("Started RTC\n");
 		goto read_rtc;
 	}
 #endif

 	tmp->tm_sec  = bcd2bin (sec & 0x7F);
 	tmp->tm_min  = bcd2bin (min & 0x7F);
 	tmp->tm_hour = bcd2bin (hour & 0x3F);
 	tmp->tm_mday = bcd2bin (mday & 0x3F);
 	tmp->tm_mon  = bcd2bin (mon & 0x1F);
 	tmp->tm_year = bcd2bin (year) + ( bcd2bin (year) >= 70 ? 1900 : 2000);
 	tmp->tm_wday = bcd2bin ((wday - 1) & 0x07);
 	tmp->tm_yday = 0;
 	tmp->tm_isdst= 0;

 	DEBUGR ("Get DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
 		tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
 		tmp->tm_hour, tmp->tm_min, tmp->tm_sec);

 	return rel;
 }

 /*
  * Set the RTC
  */
 int rtc_set (struct rtc_time *tmp)
 {
 	DEBUGR ("Set DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
 		tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
 		tmp->tm_hour, tmp->tm_min, tmp->tm_sec);

 	if (tmp->tm_year < 1970 || tmp->tm_year > 2069)
 		printf("WARNING: year should be between 1970 and 2069!\n");

 	rtc_write (RTC_YR_REG_ADDR, bin2bcd (tmp->tm_year % 100));
 	rtc_write (RTC_MON_REG_ADDR, bin2bcd (tmp->tm_mon));
 #ifdef CONFIG_RTC_MCP79411
 	rtc_write (RTC_DAY_REG_ADDR,
 		   bin2bcd (tmp->tm_wday + 1) | MCP7941X_BIT_VBATEN);
 #else
 	rtc_write (RTC_DAY_REG_ADDR, bin2bcd (tmp->tm_wday + 1));
 #endif
 	rtc_write (RTC_DATE_REG_ADDR, bin2bcd (tmp->tm_mday));
 	rtc_write (RTC_HR_REG_ADDR, bin2bcd (tmp->tm_hour));
 	rtc_write (RTC_MIN_REG_ADDR, bin2bcd (tmp->tm_min));
 #ifdef CONFIG_RTC_MCP79411
 	rtc_write (RTC_SEC_REG_ADDR, bin2bcd (tmp->tm_sec) | MCP7941X_BIT_ST);
 #else
 	rtc_write (RTC_SEC_REG_ADDR, bin2bcd (tmp->tm_sec));
 #endif

 	return 0;
 }

 /*
  * Reset the RTC. We setting the date back to 1970-01-01.
  * We also enable the oscillator output on the SQW/OUT pin and program
  * it for 32,768 Hz output. Note that according to the datasheet, turning
  * on the square wave output increases the current drain on the backup
  * battery to something between 480nA and 800nA.
  */
 void rtc_reset (void)
 {
 	rtc_write (RTC_SEC_REG_ADDR, 0x00);	/* clearing Clock Halt	*/
 	rtc_write (RTC_CTL_REG_ADDR, RTC_CTL_BIT_SQWE | RTC_CTL_BIT_RS1 | RTC_CTL_BIT_RS0);
 }

 /*
  * Helper functions
  */

 static
 uchar rtc_read (uchar reg)
 {
 	return (i2c_reg_read (CFG_SYS_I2C_RTC_ADDR, reg));
 }

 static void rtc_write (uchar reg, uchar val)
 {
 	i2c_reg_write (CFG_SYS_I2C_RTC_ADDR, reg, val);
 }

 #endif /* !CONFIG_DM_RTC */

 #ifdef CONFIG_DM_RTC
 static int ds1307_rtc_set(struct udevice *dev, const struct rtc_time *tm)
 {
 	int ret;
 	uchar buf[7];
 	enum ds_type type = dev_get_driver_data(dev);

 	debug("Set DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
 	      tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_wday,
 	      tm->tm_hour, tm->tm_min, tm->tm_sec);

 	if (tm->tm_year < 1970 || tm->tm_year > 2069)
 		printf("WARNING: year should be between 1970 and 2069!\n");

 	buf[RTC_YR_REG_ADDR] = bin2bcd(tm->tm_year % 100);
 	buf[RTC_MON_REG_ADDR] = bin2bcd(tm->tm_mon);
 	buf[RTC_DAY_REG_ADDR] = bin2bcd(tm->tm_wday + 1);
 	buf[RTC_DATE_REG_ADDR] = bin2bcd(tm->tm_mday);
 	buf[RTC_HR_REG_ADDR] = bin2bcd(tm->tm_hour);
 	buf[RTC_MIN_REG_ADDR] = bin2bcd(tm->tm_min);
 	buf[RTC_SEC_REG_ADDR] = bin2bcd(tm->tm_sec);

 	if (type == mcp794xx) {
 		buf[RTC_DAY_REG_ADDR] |= MCP7941X_BIT_VBATEN;
 		buf[RTC_SEC_REG_ADDR] |= MCP7941X_BIT_ST;
 	}

 	ret = dm_i2c_write(dev, 0, buf, sizeof(buf));
 	if (ret < 0)
 		return ret;

 	if (type == ds_1337) {
 		/* Ensure oscillator is enabled */
 		dm_i2c_reg_write(dev, DS1337_CTL_REG_ADDR, 0);
 	}

 	return 0;
 }

 static int ds1307_rtc_get(struct udevice *dev, struct rtc_time *tm)
 {
 	int ret;
 	uchar buf[7];
 	enum ds_type type = dev_get_driver_data(dev);

 	ret = dm_i2c_read(dev, 0, buf, sizeof(buf));
 	if (ret < 0)
 		return ret;

 	if (type == ds_1337 || type == ds_1340) {
 		uint reg = (type == ds_1337) ? DS1337_STAT_REG_ADDR :
 					       DS1340_STAT_REG_ADDR;
 		int status = dm_i2c_reg_read(dev, reg);

 		if (status >= 0 && (status & RTC_STAT_BIT_OSF)) {
 			printf("### Warning: RTC oscillator has stopped\n");
 			/* clear the OSF flag */
 			dm_i2c_reg_write(dev, reg, status & ~RTC_STAT_BIT_OSF);
 		}
 	}

 	tm->tm_sec  = bcd2bin(buf[RTC_SEC_REG_ADDR] & 0x7F);
 	tm->tm_min  = bcd2bin(buf[RTC_MIN_REG_ADDR] & 0x7F);
 	tm->tm_hour = bcd2bin(buf[RTC_HR_REG_ADDR] & 0x3F);
 	tm->tm_mday = bcd2bin(buf[RTC_DATE_REG_ADDR] & 0x3F);
 	tm->tm_mon  = bcd2bin(buf[RTC_MON_REG_ADDR] & 0x1F);
 	tm->tm_year = bcd2bin(buf[RTC_YR_REG_ADDR]) +
 			      (bcd2bin(buf[RTC_YR_REG_ADDR]) >= 70 ?
 			       1900 : 2000);
 	tm->tm_wday = bcd2bin((buf[RTC_DAY_REG_ADDR] - 1) & 0x07);
 	tm->tm_yday = 0;
 	tm->tm_isdst = 0;

 	debug("Get DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
 	      tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_wday,
 	      tm->tm_hour, tm->tm_min, tm->tm_sec);

 	return 0;
 }

 static int ds1307_rtc_reset(struct udevice *dev)
 {
 	int ret;
 	enum ds_type type = dev_get_driver_data(dev);

 	/*
 	 * reset clock/oscillator in the seconds register:
 	 * on DS1307 bit 7 enables Clock Halt (CH),
 	 * on DS1340 bit 7 disables the oscillator (not EOSC)
 	 * on MCP794xx bit 7 enables Start Oscillator (ST)
 	 */
 	ret = dm_i2c_reg_write(dev, RTC_SEC_REG_ADDR, 0x00);
 	if (ret < 0)
 		return ret;

 	if (type == ds_1307) {
 		/* Write control register in order to enable square-wave
 		 * output (SQWE) and set a default rate of 32.768kHz (RS1|RS0).
 		 */
 		ret = dm_i2c_reg_write(dev, RTC_CTL_REG_ADDR,
 				       RTC_CTL_BIT_SQWE | RTC_CTL_BIT_RS1 |
 				       RTC_CTL_BIT_RS0);
 	} else if (type == ds_1337) {
 		/* Write control register in order to enable oscillator output
 		 * (not EOSC) and set a default rate of 32.768kHz (RS2|RS1).
 		 */
 		ret = dm_i2c_reg_write(dev, DS1337_CTL_REG_ADDR,
 				       DS1337_CTL_BIT_RS2 | DS1337_CTL_BIT_RS1);
 	} else if (type == ds_1340 || type == mcp794xx || type == m41t11) {
 		/* Reset clock calibration, frequency test and output level. */
 		ret = dm_i2c_reg_write(dev, RTC_CTL_REG_ADDR, 0x00);
 	}

 	return ret;
 }

 static int ds1307_probe(struct udevice *dev)
 {
 	i2c_set_chip_flags(dev, DM_I2C_CHIP_RD_ADDRESS |
 			   DM_I2C_CHIP_WR_ADDRESS);

 	return 0;
 }

 static const struct rtc_ops ds1307_rtc_ops = {
 	.get = ds1307_rtc_get,
 	.set = ds1307_rtc_set,
 	.reset = ds1307_rtc_reset,
 };

 static const struct udevice_id ds1307_rtc_ids[] = {
 	{ .compatible = "dallas,ds1307", .data = ds_1307 },
 	{ .compatible = "dallas,ds1337", .data = ds_1337 },
 	{ .compatible = "dallas,ds1339", .data = ds_1339 },
 	{ .compatible = "dallas,ds1340", .data = ds_1340 },
 	{ .compatible = "microchip,mcp7940x", .data = mcp794xx },
 	{ .compatible = "microchip,mcp7941x", .data = mcp794xx },
 	{ .compatible = "st,m41t11", .data = m41t11 },
 	{ }
 };

 U_BOOT_DRIVER(rtc_ds1307) = {
 	.name	= "rtc-ds1307",
 	.id	= UCLASS_RTC,
 	.probe	= ds1307_probe,
 	.of_match = ds1307_rtc_ids,
 	.ops	= &ds1307_rtc_ops,
 };
 #endif /* CONFIG_DM_RTC */
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* (C) Copyright 2001, 2002, 2003
	* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
	* Keith Outwater, keith_outwater@mvis.com`
	* Steven Scholz, steven.scholz@imc-berlin.de
	*/

	/*
	* Date & Time support (no alarms) for Dallas Semiconductor (now Maxim)
	* DS1307 and DS1338/9 Real Time Clock (RTC).
	*
	* based on ds1337.c
	*/

	#include <config.h>
	#include <command.h>
	#include <dm.h>
	#include <log.h>
	#include <rtc.h>
	#include <i2c.h>

	enum ds_type {
	ds_1307,
	ds_1337,
	ds_1339,
	ds_1340,
	m41t11,
	mcp794xx,
	};

	/*
	* RTC register addresses
	*/
	#define RTC_SEC_REG_ADDR 0x00
	#define RTC_MIN_REG_ADDR 0x01
	#define RTC_HR_REG_ADDR 0x02
	#define RTC_DAY_REG_ADDR 0x03
	#define RTC_DATE_REG_ADDR 0x04
	#define RTC_MON_REG_ADDR 0x05
	#define RTC_YR_REG_ADDR 0x06
	#define RTC_CTL_REG_ADDR 0x07

	#define DS1337_CTL_REG_ADDR 0x0e
	#define DS1337_STAT_REG_ADDR 0x0f
	#define DS1340_STAT_REG_ADDR 0x09

	#define RTC_STAT_BIT_OSF 0x80

	#define RTC_SEC_BIT_CH 0x80 /* Clock Halt (in Register 0) */

	/* DS1307-specific bits */
	#define RTC_CTL_BIT_RS0 0x01 /* Rate select 0 */
	#define RTC_CTL_BIT_RS1 0x02 /* Rate select 1 */
	#define RTC_CTL_BIT_SQWE 0x10 /* Square Wave Enable */
	#define RTC_CTL_BIT_OUT 0x80 /* Output Control */

	/* DS1337-specific bits */
	#define DS1337_CTL_BIT_RS1 0x08 /* Rate select 1 */
	#define DS1337_CTL_BIT_RS2 0x10 /* Rate select 2 */
	#define DS1337_CTL_BIT_EOSC 0x80 /* Enable Oscillator */

	/* DS1340-specific bits */
	#define DS1340_SEC_BIT_EOSC 0x80 /* Enable Oscillator */
	#define DS1340_CTL_BIT_OUT 0x80 /* Output Control */

	/* MCP7941X-specific bits */
	#define MCP7941X_BIT_ST 0x80
	#define MCP7941X_BIT_VBATEN 0x08

	#ifndef CONFIG_DM_RTC

	/---------------------------------------------------------------------/
	#undef DEBUG_RTC

	#ifdef DEBUG_RTC
	#define DEBUGR(fmt, args...) printf(fmt, ##args)
	#else
	#define DEBUGR(fmt, args...)
	#endif
	/---------------------------------------------------------------------/

	#ifndef CFG_SYS_I2C_RTC_ADDR
	# define CFG_SYS_I2C_RTC_ADDR 0x68
	#endif

	#if defined(CONFIG_RTC_DS1307) && (CONFIG_SYS_I2C_SPEED > 100000)
	# error The DS1307 is specified only up to 100kHz!
	#endif

	static uchar rtc_read (uchar reg);
	static void rtc_write (uchar reg, uchar val);

	/*
	* Get the current time from the RTC
	*/
	int rtc_get (struct rtc_time *tmp)
	{
	int rel = 0;
	uchar sec, min, hour, mday, wday, mon, year;

	#ifdef CONFIG_RTC_MCP79411
	read_rtc:
	#endif
	sec = rtc_read (RTC_SEC_REG_ADDR);
	min = rtc_read (RTC_MIN_REG_ADDR);
	hour = rtc_read (RTC_HR_REG_ADDR);
	wday = rtc_read (RTC_DAY_REG_ADDR);
	mday = rtc_read (RTC_DATE_REG_ADDR);
	mon = rtc_read (RTC_MON_REG_ADDR);
	year = rtc_read (RTC_YR_REG_ADDR);

	DEBUGR ("Get RTC year: %02x mon: %02x mday: %02x wday: %02x "
	"hr: %02x min: %02x sec: %02x\n",
	year, mon, mday, wday, hour, min, sec);

	#ifdef CONFIG_RTC_DS1307
	if (sec & RTC_SEC_BIT_CH) {
	printf ("### Warning: RTC oscillator has stopped\n");
	/* clear the CH flag */
	rtc_write (RTC_SEC_REG_ADDR,
	rtc_read (RTC_SEC_REG_ADDR) & ~RTC_SEC_BIT_CH);
	rel = -1;
	}
	#endif

	#ifdef CONFIG_RTC_MCP79411
	/* make sure that the backup battery is enabled */
	if (!(wday & MCP7941X_BIT_VBATEN)) {
	rtc_write(RTC_DAY_REG_ADDR,
	wday \| MCP7941X_BIT_VBATEN);
	}

	/* clock halted? turn it on, so clock can tick. */
	if (!(sec & MCP7941X_BIT_ST)) {
	rtc_write(RTC_SEC_REG_ADDR, MCP7941X_BIT_ST);
	printf("Started RTC\n");
	goto read_rtc;
	}
	#endif

	tmp->tm_sec = bcd2bin (sec & 0x7F);
	tmp->tm_min = bcd2bin (min & 0x7F);
	tmp->tm_hour = bcd2bin (hour & 0x3F);
	tmp->tm_mday = bcd2bin (mday & 0x3F);
	tmp->tm_mon = bcd2bin (mon & 0x1F);
	tmp->tm_year = bcd2bin (year) + ( bcd2bin (year) >= 70 ? 1900 : 2000);
	tmp->tm_wday = bcd2bin ((wday - 1) & 0x07);
	tmp->tm_yday = 0;
	tmp->tm_isdst= 0;

	DEBUGR ("Get DATE: %4d-%02d-%02d (wday=%d) TIME: %2d:%02d:%02d\n",
	tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
	tmp->tm_hour, tmp->tm_min, tmp->tm_sec);

	return rel;
	}

	/*
	* Set the RTC
	*/
	int rtc_set (struct rtc_time *tmp)
	{
	DEBUGR ("Set DATE: %4d-%02d-%02d (wday=%d) TIME: %2d:%02d:%02d\n",
	tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
	tmp->tm_hour, tmp->tm_min, tmp->tm_sec);

	if (tmp->tm_year < 1970 \|\| tmp->tm_year > 2069)
	printf("WARNING: year should be between 1970 and 2069!\n");

	rtc_write (RTC_YR_REG_ADDR, bin2bcd (tmp->tm_year % 100));
	rtc_write (RTC_MON_REG_ADDR, bin2bcd (tmp->tm_mon));
	#ifdef CONFIG_RTC_MCP79411
	rtc_write (RTC_DAY_REG_ADDR,
	bin2bcd (tmp->tm_wday + 1) \| MCP7941X_BIT_VBATEN);
	#else
	rtc_write (RTC_DAY_REG_ADDR, bin2bcd (tmp->tm_wday + 1));
	#endif
	rtc_write (RTC_DATE_REG_ADDR, bin2bcd (tmp->tm_mday));
	rtc_write (RTC_HR_REG_ADDR, bin2bcd (tmp->tm_hour));
	rtc_write (RTC_MIN_REG_ADDR, bin2bcd (tmp->tm_min));
	#ifdef CONFIG_RTC_MCP79411
	rtc_write (RTC_SEC_REG_ADDR, bin2bcd (tmp->tm_sec) \| MCP7941X_BIT_ST);
	#else
	rtc_write (RTC_SEC_REG_ADDR, bin2bcd (tmp->tm_sec));
	#endif

	return 0;
	}

	/*
	* Reset the RTC. We setting the date back to 1970-01-01.
	* We also enable the oscillator output on the SQW/OUT pin and program
	* it for 32,768 Hz output. Note that according to the datasheet, turning
	* on the square wave output increases the current drain on the backup
	* battery to something between 480nA and 800nA.
	*/
	void rtc_reset (void)
	{
	rtc_write (RTC_SEC_REG_ADDR, 0x00); /* clearing Clock Halt */
	rtc_write (RTC_CTL_REG_ADDR, RTC_CTL_BIT_SQWE \| RTC_CTL_BIT_RS1 \| RTC_CTL_BIT_RS0);
	}

	/*
	* Helper functions
	*/

	static
	uchar rtc_read (uchar reg)
	{
	return (i2c_reg_read (CFG_SYS_I2C_RTC_ADDR, reg));
	}

	static void rtc_write (uchar reg, uchar val)
	{
	i2c_reg_write (CFG_SYS_I2C_RTC_ADDR, reg, val);
	}

	#endif /* !CONFIG_DM_RTC */

	#ifdef CONFIG_DM_RTC
	static int ds1307_rtc_set(struct udevice dev, const struct rtc_time tm)
	{
	int ret;
	uchar buf[7];
	enum ds_type type = dev_get_driver_data(dev);

	debug("Set DATE: %4d-%02d-%02d (wday=%d) TIME: %2d:%02d:%02d\n",
	tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_wday,
	tm->tm_hour, tm->tm_min, tm->tm_sec);

	if (tm->tm_year < 1970 \|\| tm->tm_year > 2069)
	printf("WARNING: year should be between 1970 and 2069!\n");

	buf[RTC_YR_REG_ADDR] = bin2bcd(tm->tm_year % 100);
	buf[RTC_MON_REG_ADDR] = bin2bcd(tm->tm_mon);
	buf[RTC_DAY_REG_ADDR] = bin2bcd(tm->tm_wday + 1);
	buf[RTC_DATE_REG_ADDR] = bin2bcd(tm->tm_mday);
	buf[RTC_HR_REG_ADDR] = bin2bcd(tm->tm_hour);
	buf[RTC_MIN_REG_ADDR] = bin2bcd(tm->tm_min);
	buf[RTC_SEC_REG_ADDR] = bin2bcd(tm->tm_sec);

	if (type == mcp794xx) {
	buf[RTC_DAY_REG_ADDR] \|= MCP7941X_BIT_VBATEN;
	buf[RTC_SEC_REG_ADDR] \|= MCP7941X_BIT_ST;
	}

	ret = dm_i2c_write(dev, 0, buf, sizeof(buf));
	if (ret < 0)
	return ret;

	if (type == ds_1337) {
	/* Ensure oscillator is enabled */
	dm_i2c_reg_write(dev, DS1337_CTL_REG_ADDR, 0);
	}

	return 0;
	}

	static int ds1307_rtc_get(struct udevice dev, struct rtc_time tm)
	{
	int ret;
	uchar buf[7];
	enum ds_type type = dev_get_driver_data(dev);

	ret = dm_i2c_read(dev, 0, buf, sizeof(buf));
	if (ret < 0)
	return ret;

	if (type == ds_1337 \|\| type == ds_1340) {
	uint reg = (type == ds_1337) ? DS1337_STAT_REG_ADDR :
	DS1340_STAT_REG_ADDR;
	int status = dm_i2c_reg_read(dev, reg);

	if (status >= 0 && (status & RTC_STAT_BIT_OSF)) {
	printf("### Warning: RTC oscillator has stopped\n");
	/* clear the OSF flag */
	dm_i2c_reg_write(dev, reg, status & ~RTC_STAT_BIT_OSF);
	}
	}

	tm->tm_sec = bcd2bin(buf[RTC_SEC_REG_ADDR] & 0x7F);
	tm->tm_min = bcd2bin(buf[RTC_MIN_REG_ADDR] & 0x7F);
	tm->tm_hour = bcd2bin(buf[RTC_HR_REG_ADDR] & 0x3F);
	tm->tm_mday = bcd2bin(buf[RTC_DATE_REG_ADDR] & 0x3F);
	tm->tm_mon = bcd2bin(buf[RTC_MON_REG_ADDR] & 0x1F);
	tm->tm_year = bcd2bin(buf[RTC_YR_REG_ADDR]) +
	(bcd2bin(buf[RTC_YR_REG_ADDR]) >= 70 ?
	1900 : 2000);
	tm->tm_wday = bcd2bin((buf[RTC_DAY_REG_ADDR] - 1) & 0x07);
	tm->tm_yday = 0;
	tm->tm_isdst = 0;

	debug("Get DATE: %4d-%02d-%02d (wday=%d) TIME: %2d:%02d:%02d\n",
	tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_wday,
	tm->tm_hour, tm->tm_min, tm->tm_sec);

	return 0;
	}

	static int ds1307_rtc_reset(struct udevice *dev)
	{
	int ret;
	enum ds_type type = dev_get_driver_data(dev);

	/*
	* reset clock/oscillator in the seconds register:
	* on DS1307 bit 7 enables Clock Halt (CH),
	* on DS1340 bit 7 disables the oscillator (not EOSC)
	* on MCP794xx bit 7 enables Start Oscillator (ST)
	*/
	ret = dm_i2c_reg_write(dev, RTC_SEC_REG_ADDR, 0x00);
	if (ret < 0)
	return ret;

	if (type == ds_1307) {
	/* Write control register in order to enable square-wave
	* output (SQWE) and set a default rate of 32.768kHz (RS1\|RS0).
	*/
	ret = dm_i2c_reg_write(dev, RTC_CTL_REG_ADDR,
	RTC_CTL_BIT_SQWE \| RTC_CTL_BIT_RS1 \|
	RTC_CTL_BIT_RS0);
	} else if (type == ds_1337) {
	/* Write control register in order to enable oscillator output
	* (not EOSC) and set a default rate of 32.768kHz (RS2\|RS1).
	*/
	ret = dm_i2c_reg_write(dev, DS1337_CTL_REG_ADDR,
	DS1337_CTL_BIT_RS2 \| DS1337_CTL_BIT_RS1);
	} else if (type == ds_1340 \|\| type == mcp794xx \|\| type == m41t11) {
	/* Reset clock calibration, frequency test and output level. */
	ret = dm_i2c_reg_write(dev, RTC_CTL_REG_ADDR, 0x00);
	}

	return ret;
	}

	static int ds1307_probe(struct udevice *dev)
	{
	i2c_set_chip_flags(dev, DM_I2C_CHIP_RD_ADDRESS \|
	DM_I2C_CHIP_WR_ADDRESS);

	return 0;
	}

	static const struct rtc_ops ds1307_rtc_ops = {
	.get = ds1307_rtc_get,
	.set = ds1307_rtc_set,
	.reset = ds1307_rtc_reset,
	};

	static const struct udevice_id ds1307_rtc_ids[] = {
	{ .compatible = "dallas,ds1307", .data = ds_1307 },
	{ .compatible = "dallas,ds1337", .data = ds_1337 },
	{ .compatible = "dallas,ds1339", .data = ds_1339 },
	{ .compatible = "dallas,ds1340", .data = ds_1340 },
	{ .compatible = "microchip,mcp7940x", .data = mcp794xx },
	{ .compatible = "microchip,mcp7941x", .data = mcp794xx },
	{ .compatible = "st,m41t11", .data = m41t11 },
	{ }
	};

	U_BOOT_DRIVER(rtc_ds1307) = {
	.name = "rtc-ds1307",
	.id = UCLASS_RTC,
	.probe = ds1307_probe,
	.of_match = ds1307_rtc_ids,
	.ops = &ds1307_rtc_ops,
	};
	#endif /* CONFIG_DM_RTC */