drivers/rtc/rtc-bfin.c - kernel/msm - Gitiles

 /*
  * Blackfin On-Chip Real Time Clock Driver
  *  Supports BF51x/BF52x/BF53[123]/BF53[467]/BF54x
  *
  * Copyright 2004-2010 Analog Devices Inc.
  *
  * Enter bugs at http://blackfin.uclinux.org/
  *
  * Licensed under the GPL-2 or later.
  */

 /* The biggest issue we deal with in this driver is that register writes are
  * synced to the RTC frequency of 1Hz.  So if you write to a register and
  * attempt to write again before the first write has completed, the new write
  * is simply discarded.  This can easily be troublesome if userspace disables
  * one event (say periodic) and then right after enables an event (say alarm).
  * Since all events are maintained in the same interrupt mask register, if
  * we wrote to it to disable the first event and then wrote to it again to
  * enable the second event, that second event would not be enabled as the
  * write would be discarded and things quickly fall apart.
  *
  * To keep this delay from significantly degrading performance (we, in theory,
  * would have to sleep for up to 1 second everytime we wanted to write a
  * register), we only check the write pending status before we start to issue
  * a new write.  We bank on the idea that it doesnt matter when the sync
  * happens so long as we don't attempt another write before it does.  The only
  * time userspace would take this penalty is when they try and do multiple
  * operations right after another ... but in this case, they need to take the
  * sync penalty, so we should be OK.
  *
  * Also note that the RTC_ISTAT register does not suffer this penalty; its
  * writes to clear status registers complete immediately.
  */

 /* It may seem odd that there is no SWCNT code in here (which would be exposed
  * via the periodic interrupt event, or PIE).  Since the Blackfin RTC peripheral
  * runs in units of seconds (N/HZ) but the Linux framework runs in units of HZ
  * (2^N HZ), there is no point in keeping code that only provides 1 HZ PIEs.
  * The same exact behavior can be accomplished by using the update interrupt
  * event (UIE).  Maybe down the line the RTC peripheral will suck less in which
  * case we can re-introduce PIE support.
  */

 #include <linux/bcd.h>
 #include <linux/completion.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/rtc.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>

 #include <asm/blackfin.h>

 #define dev_dbg_stamp(dev) dev_dbg(dev, "%s:%i: here i am\n", __func__, __LINE__)

 struct bfin_rtc {
 	struct rtc_device *rtc_dev;
 	struct rtc_time rtc_alarm;
 	u16 rtc_wrote_regs;
 };

 /* Bit values for the ISTAT / ICTL registers */
 #define RTC_ISTAT_WRITE_COMPLETE  0x8000
 #define RTC_ISTAT_WRITE_PENDING   0x4000
 #define RTC_ISTAT_ALARM_DAY       0x0040
 #define RTC_ISTAT_24HR            0x0020
 #define RTC_ISTAT_HOUR            0x0010
 #define RTC_ISTAT_MIN             0x0008
 #define RTC_ISTAT_SEC             0x0004
 #define RTC_ISTAT_ALARM           0x0002
 #define RTC_ISTAT_STOPWATCH       0x0001

 /* Shift values for RTC_STAT register */
 #define DAY_BITS_OFF    17
 #define HOUR_BITS_OFF   12
 #define MIN_BITS_OFF    6
 #define SEC_BITS_OFF    0

 /* Some helper functions to convert between the common RTC notion of time
  * and the internal Blackfin notion that is encoded in 32bits.
  */
 static inline u32 rtc_time_to_bfin(unsigned long now)
 {
 	u32 sec  = (now % 60);
 	u32 min  = (now % (60 * 60)) / 60;
 	u32 hour = (now % (60 * 60 * 24)) / (60 * 60);
 	u32 days = (now / (60 * 60 * 24));
 	return (sec  << SEC_BITS_OFF) +
 	       (min  << MIN_BITS_OFF) +
 	       (hour << HOUR_BITS_OFF) +
 	       (days << DAY_BITS_OFF);
 }
 static inline unsigned long rtc_bfin_to_time(u32 rtc_bfin)
 {
 	return (((rtc_bfin >> SEC_BITS_OFF)  & 0x003F)) +
 	       (((rtc_bfin >> MIN_BITS_OFF)  & 0x003F) * 60) +
 	       (((rtc_bfin >> HOUR_BITS_OFF) & 0x001F) * 60 * 60) +
 	       (((rtc_bfin >> DAY_BITS_OFF)  & 0x7FFF) * 60 * 60 * 24);
 }
 static inline void rtc_bfin_to_tm(u32 rtc_bfin, struct rtc_time *tm)
 {
 	rtc_time_to_tm(rtc_bfin_to_time(rtc_bfin), tm);
 }

 /**
  *	bfin_rtc_sync_pending - make sure pending writes have complete
  *
  * Wait for the previous write to a RTC register to complete.
  * Unfortunately, we can't sleep here as that introduces a race condition when
  * turning on interrupt events.  Consider this:
  *  - process sets alarm
  *  - process enables alarm
  *  - process sleeps while waiting for rtc write to sync
  *  - interrupt fires while process is sleeping
  *  - interrupt acks the event by writing to ISTAT
  *  - interrupt sets the WRITE PENDING bit
  *  - interrupt handler finishes
  *  - process wakes up, sees WRITE PENDING bit set, goes to sleep
  *  - interrupt fires while process is sleeping
  * If anyone can point out the obvious solution here, i'm listening :).  This
  * shouldn't be an issue on an SMP or preempt system as this function should
  * only be called with the rtc lock held.
  *
  * Other options:
  *  - disable PREN so the sync happens at 32.768kHZ ... but this changes the
  *    inc rate for all RTC registers from 1HZ to 32.768kHZ ...
  *  - use the write complete IRQ
  */
 /*
 static void bfin_rtc_sync_pending_polled(void)
 {
 	while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_COMPLETE))
 		if (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING))
 			break;
 	bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE);
 }
 */
 static DECLARE_COMPLETION(bfin_write_complete);
 static void bfin_rtc_sync_pending(struct device *dev)
 {
 	dev_dbg_stamp(dev);
 	while (bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)
 		wait_for_completion_timeout(&bfin_write_complete, HZ * 5);
 	dev_dbg_stamp(dev);
 }

 /**
  *	bfin_rtc_reset - set RTC to sane/known state
  *
  * Initialize the RTC.  Enable pre-scaler to scale RTC clock
  * to 1Hz and clear interrupt/status registers.
  */
 static void bfin_rtc_reset(struct device *dev, u16 rtc_ictl)
 {
 	struct bfin_rtc *rtc = dev_get_drvdata(dev);
 	dev_dbg_stamp(dev);
 	bfin_rtc_sync_pending(dev);
 	bfin_write_RTC_PREN(0x1);
 	bfin_write_RTC_ICTL(rtc_ictl);
 	bfin_write_RTC_ALARM(0);
 	bfin_write_RTC_ISTAT(0xFFFF);
 	rtc->rtc_wrote_regs = 0;
 }

 /**
  *	bfin_rtc_interrupt - handle interrupt from RTC
  *
  * Since we handle all RTC events here, we have to make sure the requested
  * interrupt is enabled (in RTC_ICTL) as the event status register (RTC_ISTAT)
  * always gets updated regardless of the interrupt being enabled.  So when one
  * even we care about (e.g. stopwatch) goes off, we don't want to turn around
  * and say that other events have happened as well (e.g. second).  We do not
  * have to worry about pending writes to the RTC_ICTL register as interrupts
  * only fire if they are enabled in the RTC_ICTL register.
  */
 static irqreturn_t bfin_rtc_interrupt(int irq, void *dev_id)
 {
 	struct device *dev = dev_id;
 	struct bfin_rtc *rtc = dev_get_drvdata(dev);
 	unsigned long events = 0;
 	bool write_complete = false;
 	u16 rtc_istat, rtc_istat_clear, rtc_ictl, bits;

 	dev_dbg_stamp(dev);

 	rtc_istat = bfin_read_RTC_ISTAT();
 	rtc_ictl = bfin_read_RTC_ICTL();
 	rtc_istat_clear = 0;

 	bits = RTC_ISTAT_WRITE_COMPLETE;
 	if (rtc_istat & bits) {
 		rtc_istat_clear |= bits;
 		write_complete = true;
 		complete(&bfin_write_complete);
 	}

 	bits = (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY);
 	if (rtc_ictl & bits) {
 		if (rtc_istat & bits) {
 			rtc_istat_clear |= bits;
 			events |= RTC_AF | RTC_IRQF;
 		}
 	}

 	bits = RTC_ISTAT_SEC;
 	if (rtc_ictl & bits) {
 		if (rtc_istat & bits) {
 			rtc_istat_clear |= bits;
 			events |= RTC_UF | RTC_IRQF;
 		}
 	}

 	if (events)
 		rtc_update_irq(rtc->rtc_dev, 1, events);

 	if (write_complete || events) {
 		bfin_write_RTC_ISTAT(rtc_istat_clear);
 		return IRQ_HANDLED;
 	} else
 		return IRQ_NONE;
 }

 static void bfin_rtc_int_set(u16 rtc_int)
 {
 	bfin_write_RTC_ISTAT(rtc_int);
 	bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | rtc_int);
 }
 static void bfin_rtc_int_clear(u16 rtc_int)
 {
 	bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & rtc_int);
 }
 static void bfin_rtc_int_set_alarm(struct bfin_rtc *rtc)
 {
 	/* Blackfin has different bits for whether the alarm is
 	 * more than 24 hours away.
 	 */
 	bfin_rtc_int_set(rtc->rtc_alarm.tm_yday == -1 ? RTC_ISTAT_ALARM : RTC_ISTAT_ALARM_DAY);
 }
 static int bfin_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 {
 	struct bfin_rtc *rtc = dev_get_drvdata(dev);
 	int ret = 0;

 	dev_dbg_stamp(dev);

 	bfin_rtc_sync_pending(dev);

 	switch (cmd) {
 	case RTC_UIE_ON:
 		dev_dbg_stamp(dev);
 		bfin_rtc_int_set(RTC_ISTAT_SEC);
 		break;
 	case RTC_UIE_OFF:
 		dev_dbg_stamp(dev);
 		bfin_rtc_int_clear(~RTC_ISTAT_SEC);
 		break;

 	default:
 		dev_dbg_stamp(dev);
 		ret = -ENOIOCTLCMD;
 	}

 	return ret;
 }

 static int bfin_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
 {
 	struct bfin_rtc *rtc = dev_get_drvdata(dev);

 	dev_dbg_stamp(dev);
 	if (enabled)
 		bfin_rtc_int_set_alarm(rtc);
 	else
 		bfin_rtc_int_clear(~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
 }

 static int bfin_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct bfin_rtc *rtc = dev_get_drvdata(dev);

 	dev_dbg_stamp(dev);

 	if (rtc->rtc_wrote_regs & 0x1)
 		bfin_rtc_sync_pending(dev);

 	rtc_bfin_to_tm(bfin_read_RTC_STAT(), tm);

 	return 0;
 }

 static int bfin_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct bfin_rtc *rtc = dev_get_drvdata(dev);
 	int ret;
 	unsigned long now;

 	dev_dbg_stamp(dev);

 	ret = rtc_tm_to_time(tm, &now);
 	if (ret == 0) {
 		if (rtc->rtc_wrote_regs & 0x1)
 			bfin_rtc_sync_pending(dev);
 		bfin_write_RTC_STAT(rtc_time_to_bfin(now));
 		rtc->rtc_wrote_regs = 0x1;
 	}

 	return ret;
 }

 static int bfin_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct bfin_rtc *rtc = dev_get_drvdata(dev);
 	dev_dbg_stamp(dev);
 	alrm->time = rtc->rtc_alarm;
 	bfin_rtc_sync_pending(dev);
 	alrm->enabled = !!(bfin_read_RTC_ICTL() & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
 	return 0;
 }

 static int bfin_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct bfin_rtc *rtc = dev_get_drvdata(dev);
 	unsigned long rtc_alarm;

 	dev_dbg_stamp(dev);

 	if (rtc_tm_to_time(&alrm->time, &rtc_alarm))
 		return -EINVAL;

 	rtc->rtc_alarm = alrm->time;

 	bfin_rtc_sync_pending(dev);
 	bfin_write_RTC_ALARM(rtc_time_to_bfin(rtc_alarm));
 	if (alrm->enabled)
 		bfin_rtc_int_set_alarm(rtc);

 	return 0;
 }

 static int bfin_rtc_proc(struct device *dev, struct seq_file *seq)
 {
 #define yesno(x) ((x) ? "yes" : "no")
 	u16 ictl = bfin_read_RTC_ICTL();
 	dev_dbg_stamp(dev);
 	seq_printf(seq,
 		"alarm_IRQ\t: %s\n"
 		"wkalarm_IRQ\t: %s\n"
 		"seconds_IRQ\t: %s\n",
 		yesno(ictl & RTC_ISTAT_ALARM),
 		yesno(ictl & RTC_ISTAT_ALARM_DAY),
 		yesno(ictl & RTC_ISTAT_SEC));
 	return 0;
 #undef yesno
 }

 static struct rtc_class_ops bfin_rtc_ops = {
 	.ioctl         = bfin_rtc_ioctl,
 	.read_time     = bfin_rtc_read_time,
 	.set_time      = bfin_rtc_set_time,
 	.read_alarm    = bfin_rtc_read_alarm,
 	.set_alarm     = bfin_rtc_set_alarm,
 	.proc          = bfin_rtc_proc,
 	.alarm_irq_enable = bfin_rtc_alarm_irq_enable,
 };

 static int __devinit bfin_rtc_probe(struct platform_device *pdev)
 {
 	struct bfin_rtc *rtc;
 	struct device *dev = &pdev->dev;
 	int ret = 0;
 	unsigned long timeout = jiffies + HZ;

 	dev_dbg_stamp(dev);

 	/* Allocate memory for our RTC struct */
 	rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
 	if (unlikely(!rtc))
 		return -ENOMEM;
 	platform_set_drvdata(pdev, rtc);
 	device_init_wakeup(dev, 1);

 	/* Register our RTC with the RTC framework */
 	rtc->rtc_dev = rtc_device_register(pdev->name, dev, &bfin_rtc_ops,
 						THIS_MODULE);
 	if (unlikely(IS_ERR(rtc->rtc_dev))) {
 		ret = PTR_ERR(rtc->rtc_dev);
 		goto err;
 	}

 	/* Grab the IRQ and init the hardware */
 	ret = request_irq(IRQ_RTC, bfin_rtc_interrupt, 0, pdev->name, dev);
 	if (unlikely(ret))
 		goto err_reg;
 	/* sometimes the bootloader touched things, but the write complete was not
 	 * enabled, so let's just do a quick timeout here since the IRQ will not fire ...
 	 */
 	while (bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)
 		if (time_after(jiffies, timeout))
 			break;
 	bfin_rtc_reset(dev, RTC_ISTAT_WRITE_COMPLETE);
 	bfin_write_RTC_SWCNT(0);

 	return 0;

 err_reg:
 	rtc_device_unregister(rtc->rtc_dev);
 err:
 	kfree(rtc);
 	return ret;
 }

 static int __devexit bfin_rtc_remove(struct platform_device *pdev)
 {
 	struct bfin_rtc *rtc = platform_get_drvdata(pdev);
 	struct device *dev = &pdev->dev;

 	bfin_rtc_reset(dev, 0);
 	free_irq(IRQ_RTC, dev);
 	rtc_device_unregister(rtc->rtc_dev);
 	platform_set_drvdata(pdev, NULL);
 	kfree(rtc);

 	return 0;
 }

 #ifdef CONFIG_PM
 static int bfin_rtc_suspend(struct platform_device *pdev, pm_message_t state)
 {
 	struct device *dev = &pdev->dev;

 	dev_dbg_stamp(dev);

 	if (device_may_wakeup(dev)) {
 		enable_irq_wake(IRQ_RTC);
 		bfin_rtc_sync_pending(dev);
 	} else
 		bfin_rtc_int_clear(0);

 	return 0;
 }

 static int bfin_rtc_resume(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;

 	dev_dbg_stamp(dev);

 	if (device_may_wakeup(dev))
 		disable_irq_wake(IRQ_RTC);

 	/*
 	 * Since only some of the RTC bits are maintained externally in the
 	 * Vbat domain, we need to wait for the RTC MMRs to be synced into
 	 * the core after waking up.  This happens every RTC 1HZ.  Once that
 	 * has happened, we can go ahead and re-enable the important write
 	 * complete interrupt event.
 	 */
 	while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_SEC))
 		continue;
 	bfin_rtc_int_set(RTC_ISTAT_WRITE_COMPLETE);

 	return 0;
 }
 #else
 # define bfin_rtc_suspend NULL
 # define bfin_rtc_resume  NULL
 #endif

 static struct platform_driver bfin_rtc_driver = {
 	.driver		= {
 		.name	= "rtc-bfin",
 		.owner	= THIS_MODULE,
 	},
 	.probe		= bfin_rtc_probe,
 	.remove		= __devexit_p(bfin_rtc_remove),
 	.suspend	= bfin_rtc_suspend,
 	.resume		= bfin_rtc_resume,
 };

 static int __init bfin_rtc_init(void)
 {
 	return platform_driver_register(&bfin_rtc_driver);
 }

 static void __exit bfin_rtc_exit(void)
 {
 	platform_driver_unregister(&bfin_rtc_driver);
 }

 module_init(bfin_rtc_init);
 module_exit(bfin_rtc_exit);

 MODULE_DESCRIPTION("Blackfin On-Chip Real Time Clock Driver");
 MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:rtc-bfin");
	/*
	* Blackfin On-Chip Real Time Clock Driver
	* Supports BF51x/BF52x/BF53[123]/BF53[467]/BF54x
	*
	* Copyright 2004-2010 Analog Devices Inc.
	*
	* Enter bugs at http://blackfin.uclinux.org/
	*
	* Licensed under the GPL-2 or later.
	*/

	/* The biggest issue we deal with in this driver is that register writes are
	* synced to the RTC frequency of 1Hz. So if you write to a register and
	* attempt to write again before the first write has completed, the new write
	* is simply discarded. This can easily be troublesome if userspace disables
	* one event (say periodic) and then right after enables an event (say alarm).
	* Since all events are maintained in the same interrupt mask register, if
	* we wrote to it to disable the first event and then wrote to it again to
	* enable the second event, that second event would not be enabled as the
	* write would be discarded and things quickly fall apart.
	*
	* To keep this delay from significantly degrading performance (we, in theory,
	* would have to sleep for up to 1 second everytime we wanted to write a
	* register), we only check the write pending status before we start to issue
	* a new write. We bank on the idea that it doesnt matter when the sync
	* happens so long as we don't attempt another write before it does. The only
	* time userspace would take this penalty is when they try and do multiple
	* operations right after another ... but in this case, they need to take the
	* sync penalty, so we should be OK.
	*
	* Also note that the RTC_ISTAT register does not suffer this penalty; its
	* writes to clear status registers complete immediately.
	*/

	/* It may seem odd that there is no SWCNT code in here (which would be exposed
	* via the periodic interrupt event, or PIE). Since the Blackfin RTC peripheral
	* runs in units of seconds (N/HZ) but the Linux framework runs in units of HZ
	* (2^N HZ), there is no point in keeping code that only provides 1 HZ PIEs.
	* The same exact behavior can be accomplished by using the update interrupt
	* event (UIE). Maybe down the line the RTC peripheral will suck less in which
	* case we can re-introduce PIE support.
	*/

	#include <linux/bcd.h>
	#include <linux/completion.h>
	#include <linux/delay.h>
	#include <linux/init.h>
	#include <linux/interrupt.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/rtc.h>
	#include <linux/seq_file.h>
	#include <linux/slab.h>

	#include <asm/blackfin.h>

	#define dev_dbg_stamp(dev) dev_dbg(dev, "%s:%i: here i am\n", __func__, __LINE__)

	struct bfin_rtc {
	struct rtc_device *rtc_dev;
	struct rtc_time rtc_alarm;
	u16 rtc_wrote_regs;
	};

	/* Bit values for the ISTAT / ICTL registers */
	#define RTC_ISTAT_WRITE_COMPLETE 0x8000
	#define RTC_ISTAT_WRITE_PENDING 0x4000
	#define RTC_ISTAT_ALARM_DAY 0x0040
	#define RTC_ISTAT_24HR 0x0020
	#define RTC_ISTAT_HOUR 0x0010
	#define RTC_ISTAT_MIN 0x0008
	#define RTC_ISTAT_SEC 0x0004
	#define RTC_ISTAT_ALARM 0x0002
	#define RTC_ISTAT_STOPWATCH 0x0001

	/* Shift values for RTC_STAT register */
	#define DAY_BITS_OFF 17
	#define HOUR_BITS_OFF 12
	#define MIN_BITS_OFF 6
	#define SEC_BITS_OFF 0

	/* Some helper functions to convert between the common RTC notion of time
	* and the internal Blackfin notion that is encoded in 32bits.
	*/
	static inline u32 rtc_time_to_bfin(unsigned long now)
	{
	u32 sec = (now % 60);
	u32 min = (now % (60 * 60)) / 60;
	u32 hour = (now % (60 * 60 * 24)) / (60 * 60);
	u32 days = (now / (60 * 60 * 24));
	return (sec << SEC_BITS_OFF) +
	(min << MIN_BITS_OFF) +
	(hour << HOUR_BITS_OFF) +
	(days << DAY_BITS_OFF);
	}
	static inline unsigned long rtc_bfin_to_time(u32 rtc_bfin)
	{
	return (((rtc_bfin >> SEC_BITS_OFF) & 0x003F)) +
	(((rtc_bfin >> MIN_BITS_OFF) & 0x003F) * 60) +
	(((rtc_bfin >> HOUR_BITS_OFF) & 0x001F) * 60 * 60) +
	(((rtc_bfin >> DAY_BITS_OFF) & 0x7FFF) * 60 * 60 * 24);
	}
	static inline void rtc_bfin_to_tm(u32 rtc_bfin, struct rtc_time *tm)
	{
	rtc_time_to_tm(rtc_bfin_to_time(rtc_bfin), tm);
	}

	/**
	* bfin_rtc_sync_pending - make sure pending writes have complete
	*
	* Wait for the previous write to a RTC register to complete.
	* Unfortunately, we can't sleep here as that introduces a race condition when
	* turning on interrupt events. Consider this:
	* - process sets alarm
	* - process enables alarm
	* - process sleeps while waiting for rtc write to sync
	* - interrupt fires while process is sleeping
	* - interrupt acks the event by writing to ISTAT
	* - interrupt sets the WRITE PENDING bit
	* - interrupt handler finishes
	* - process wakes up, sees WRITE PENDING bit set, goes to sleep
	* - interrupt fires while process is sleeping
	* If anyone can point out the obvious solution here, i'm listening :). This
	* shouldn't be an issue on an SMP or preempt system as this function should
	* only be called with the rtc lock held.
	*
	* Other options:
	* - disable PREN so the sync happens at 32.768kHZ ... but this changes the
	* inc rate for all RTC registers from 1HZ to 32.768kHZ ...
	* - use the write complete IRQ
	*/
	/*
	static void bfin_rtc_sync_pending_polled(void)
	{
	while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_COMPLETE))
	if (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING))
	break;
	bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE);
	}
	*/
	static DECLARE_COMPLETION(bfin_write_complete);
	static void bfin_rtc_sync_pending(struct device *dev)
	{
	dev_dbg_stamp(dev);
	while (bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)
	wait_for_completion_timeout(&bfin_write_complete, HZ * 5);
	dev_dbg_stamp(dev);
	}

	/**
	* bfin_rtc_reset - set RTC to sane/known state
	*
	* Initialize the RTC. Enable pre-scaler to scale RTC clock
	* to 1Hz and clear interrupt/status registers.
	*/
	static void bfin_rtc_reset(struct device *dev, u16 rtc_ictl)
	{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	dev_dbg_stamp(dev);
	bfin_rtc_sync_pending(dev);
	bfin_write_RTC_PREN(0x1);
	bfin_write_RTC_ICTL(rtc_ictl);
	bfin_write_RTC_ALARM(0);
	bfin_write_RTC_ISTAT(0xFFFF);
	rtc->rtc_wrote_regs = 0;
	}

	/**
	* bfin_rtc_interrupt - handle interrupt from RTC
	*
	* Since we handle all RTC events here, we have to make sure the requested
	* interrupt is enabled (in RTC_ICTL) as the event status register (RTC_ISTAT)
	* always gets updated regardless of the interrupt being enabled. So when one
	* even we care about (e.g. stopwatch) goes off, we don't want to turn around
	* and say that other events have happened as well (e.g. second). We do not
	* have to worry about pending writes to the RTC_ICTL register as interrupts
	* only fire if they are enabled in the RTC_ICTL register.
	*/
	static irqreturn_t bfin_rtc_interrupt(int irq, void *dev_id)
	{
	struct device *dev = dev_id;
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	unsigned long events = 0;
	bool write_complete = false;
	u16 rtc_istat, rtc_istat_clear, rtc_ictl, bits;

	dev_dbg_stamp(dev);

	rtc_istat = bfin_read_RTC_ISTAT();
	rtc_ictl = bfin_read_RTC_ICTL();
	rtc_istat_clear = 0;

	bits = RTC_ISTAT_WRITE_COMPLETE;
	if (rtc_istat & bits) {
	rtc_istat_clear \|= bits;
	write_complete = true;
	complete(&bfin_write_complete);
	}

	bits = (RTC_ISTAT_ALARM \| RTC_ISTAT_ALARM_DAY);
	if (rtc_ictl & bits) {
	if (rtc_istat & bits) {
	rtc_istat_clear \|= bits;
	events \|= RTC_AF \| RTC_IRQF;
	}
	}

	bits = RTC_ISTAT_SEC;
	if (rtc_ictl & bits) {
	if (rtc_istat & bits) {
	rtc_istat_clear \|= bits;
	events \|= RTC_UF \| RTC_IRQF;
	}
	}

	if (events)
	rtc_update_irq(rtc->rtc_dev, 1, events);

	if (write_complete \|\| events) {
	bfin_write_RTC_ISTAT(rtc_istat_clear);
	return IRQ_HANDLED;
	} else
	return IRQ_NONE;
	}

	static void bfin_rtc_int_set(u16 rtc_int)
	{
	bfin_write_RTC_ISTAT(rtc_int);
	bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() \| rtc_int);
	}
	static void bfin_rtc_int_clear(u16 rtc_int)
	{
	bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & rtc_int);
	}
	static void bfin_rtc_int_set_alarm(struct bfin_rtc *rtc)
	{
	/* Blackfin has different bits for whether the alarm is
	* more than 24 hours away.
	*/
	bfin_rtc_int_set(rtc->rtc_alarm.tm_yday == -1 ? RTC_ISTAT_ALARM : RTC_ISTAT_ALARM_DAY);
	}
	static int bfin_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
	{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	int ret = 0;

	dev_dbg_stamp(dev);

	bfin_rtc_sync_pending(dev);

	switch (cmd) {
	case RTC_UIE_ON:
	dev_dbg_stamp(dev);
	bfin_rtc_int_set(RTC_ISTAT_SEC);
	break;
	case RTC_UIE_OFF:
	dev_dbg_stamp(dev);
	bfin_rtc_int_clear(~RTC_ISTAT_SEC);
	break;

	default:
	dev_dbg_stamp(dev);
	ret = -ENOIOCTLCMD;
	}

	return ret;
	}

	static int bfin_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
	{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);

	dev_dbg_stamp(dev);
	if (enabled)
	bfin_rtc_int_set_alarm(rtc);
	else
	bfin_rtc_int_clear(~(RTC_ISTAT_ALARM \| RTC_ISTAT_ALARM_DAY));
	}

	static int bfin_rtc_read_time(struct device dev, struct rtc_time tm)
	{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);

	dev_dbg_stamp(dev);

	if (rtc->rtc_wrote_regs & 0x1)
	bfin_rtc_sync_pending(dev);

	rtc_bfin_to_tm(bfin_read_RTC_STAT(), tm);

	return 0;
	}

	static int bfin_rtc_set_time(struct device dev, struct rtc_time tm)
	{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	int ret;
	unsigned long now;

	dev_dbg_stamp(dev);

	ret = rtc_tm_to_time(tm, &now);
	if (ret == 0) {
	if (rtc->rtc_wrote_regs & 0x1)
	bfin_rtc_sync_pending(dev);
	bfin_write_RTC_STAT(rtc_time_to_bfin(now));
	rtc->rtc_wrote_regs = 0x1;
	}

	return ret;
	}

	static int bfin_rtc_read_alarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	dev_dbg_stamp(dev);
	alrm->time = rtc->rtc_alarm;
	bfin_rtc_sync_pending(dev);
	alrm->enabled = !!(bfin_read_RTC_ICTL() & (RTC_ISTAT_ALARM \| RTC_ISTAT_ALARM_DAY));
	return 0;
	}

	static int bfin_rtc_set_alarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	unsigned long rtc_alarm;

	dev_dbg_stamp(dev);

	if (rtc_tm_to_time(&alrm->time, &rtc_alarm))
	return -EINVAL;

	rtc->rtc_alarm = alrm->time;

	bfin_rtc_sync_pending(dev);
	bfin_write_RTC_ALARM(rtc_time_to_bfin(rtc_alarm));
	if (alrm->enabled)
	bfin_rtc_int_set_alarm(rtc);

	return 0;
	}

	static int bfin_rtc_proc(struct device dev, struct seq_file seq)
	{
	#define yesno(x) ((x) ? "yes" : "no")
	u16 ictl = bfin_read_RTC_ICTL();
	dev_dbg_stamp(dev);
	seq_printf(seq,
	"alarm_IRQ\t: %s\n"
	"wkalarm_IRQ\t: %s\n"
	"seconds_IRQ\t: %s\n",
	yesno(ictl & RTC_ISTAT_ALARM),
	yesno(ictl & RTC_ISTAT_ALARM_DAY),
	yesno(ictl & RTC_ISTAT_SEC));
	return 0;
	#undef yesno
	}

	static struct rtc_class_ops bfin_rtc_ops = {
	.ioctl = bfin_rtc_ioctl,
	.read_time = bfin_rtc_read_time,
	.set_time = bfin_rtc_set_time,
	.read_alarm = bfin_rtc_read_alarm,
	.set_alarm = bfin_rtc_set_alarm,
	.proc = bfin_rtc_proc,
	.alarm_irq_enable = bfin_rtc_alarm_irq_enable,
	};

	static int __devinit bfin_rtc_probe(struct platform_device *pdev)
	{
	struct bfin_rtc *rtc;
	struct device *dev = &pdev->dev;
	int ret = 0;
	unsigned long timeout = jiffies + HZ;

	dev_dbg_stamp(dev);

	/* Allocate memory for our RTC struct */
	rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
	if (unlikely(!rtc))
	return -ENOMEM;
	platform_set_drvdata(pdev, rtc);
	device_init_wakeup(dev, 1);

	/* Register our RTC with the RTC framework */
	rtc->rtc_dev = rtc_device_register(pdev->name, dev, &bfin_rtc_ops,
	THIS_MODULE);
	if (unlikely(IS_ERR(rtc->rtc_dev))) {
	ret = PTR_ERR(rtc->rtc_dev);
	goto err;
	}

	/* Grab the IRQ and init the hardware */
	ret = request_irq(IRQ_RTC, bfin_rtc_interrupt, 0, pdev->name, dev);
	if (unlikely(ret))
	goto err_reg;
	/* sometimes the bootloader touched things, but the write complete was not
	* enabled, so let's just do a quick timeout here since the IRQ will not fire ...
	*/
	while (bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)
	if (time_after(jiffies, timeout))
	break;
	bfin_rtc_reset(dev, RTC_ISTAT_WRITE_COMPLETE);
	bfin_write_RTC_SWCNT(0);

	return 0;

	err_reg:
	rtc_device_unregister(rtc->rtc_dev);
	err:
	kfree(rtc);
	return ret;
	}

	static int __devexit bfin_rtc_remove(struct platform_device *pdev)
	{
	struct bfin_rtc *rtc = platform_get_drvdata(pdev);
	struct device *dev = &pdev->dev;

	bfin_rtc_reset(dev, 0);
	free_irq(IRQ_RTC, dev);
	rtc_device_unregister(rtc->rtc_dev);
	platform_set_drvdata(pdev, NULL);
	kfree(rtc);

	return 0;
	}

	#ifdef CONFIG_PM
	static int bfin_rtc_suspend(struct platform_device *pdev, pm_message_t state)
	{
	struct device *dev = &pdev->dev;

	dev_dbg_stamp(dev);

	if (device_may_wakeup(dev)) {
	enable_irq_wake(IRQ_RTC);
	bfin_rtc_sync_pending(dev);
	} else
	bfin_rtc_int_clear(0);

	return 0;
	}

	static int bfin_rtc_resume(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;

	dev_dbg_stamp(dev);

	if (device_may_wakeup(dev))
	disable_irq_wake(IRQ_RTC);

	/*
	* Since only some of the RTC bits are maintained externally in the
	* Vbat domain, we need to wait for the RTC MMRs to be synced into
	* the core after waking up. This happens every RTC 1HZ. Once that
	* has happened, we can go ahead and re-enable the important write
	* complete interrupt event.
	*/
	while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_SEC))
	continue;
	bfin_rtc_int_set(RTC_ISTAT_WRITE_COMPLETE);

	return 0;
	}
	#else
	# define bfin_rtc_suspend NULL
	# define bfin_rtc_resume NULL
	#endif

	static struct platform_driver bfin_rtc_driver = {
	.driver = {
	.name = "rtc-bfin",
	.owner = THIS_MODULE,
	},
	.probe = bfin_rtc_probe,
	.remove = __devexit_p(bfin_rtc_remove),
	.suspend = bfin_rtc_suspend,
	.resume = bfin_rtc_resume,
	};

	static int __init bfin_rtc_init(void)
	{
	return platform_driver_register(&bfin_rtc_driver);
	}

	static void __exit bfin_rtc_exit(void)
	{
	platform_driver_unregister(&bfin_rtc_driver);
	}

	module_init(bfin_rtc_init);
	module_exit(bfin_rtc_exit);

	MODULE_DESCRIPTION("Blackfin On-Chip Real Time Clock Driver");
	MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("platform:rtc-bfin");