[deliverable/linux.git] / drivers / rtc / rtc-bfin.c

/*
 * Blackfin On-Chip Real Time Clock Driver
 *  Supports BF52[257]/BF53[123]/BF53[467]/BF54[24789]
 *
 * Copyright 2004-2007 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.
 */

#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 <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)
{
        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_ISTAT_WRITE_COMPLETE);
        bfin_write_RTC_SWCNT(0);
        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_ictl;

        dev_dbg_stamp(dev);

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

        if (rtc_istat & RTC_ISTAT_WRITE_COMPLETE) {
                bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE);
                write_complete = true;
                complete(&bfin_write_complete);
        }

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

        if (rtc_ictl & RTC_ISTAT_STOPWATCH) {
                if (rtc_istat & RTC_ISTAT_STOPWATCH) {
                        bfin_write_RTC_ISTAT(RTC_ISTAT_STOPWATCH);
                        events |= RTC_PF | RTC_IRQF;
                        bfin_write_RTC_SWCNT(rtc->rtc_dev->irq_freq);
                }
        }

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

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

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

static int bfin_rtc_open(struct device *dev)
{
        int ret;

        dev_dbg_stamp(dev);

        ret = request_irq(IRQ_RTC, bfin_rtc_interrupt, IRQF_SHARED, to_platform_device(dev)->name, dev);
        if (!ret)
                bfin_rtc_reset(dev);

        return ret;
}

static void bfin_rtc_release(struct device *dev)
{
        dev_dbg_stamp(dev);
        bfin_rtc_reset(dev);
        free_irq(IRQ_RTC, dev);
}

static void bfin_rtc_int_set(struct bfin_rtc *rtc, 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(struct bfin_rtc *rtc, 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->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_PIE_ON:
                dev_dbg_stamp(dev);
                bfin_rtc_int_set(rtc, RTC_ISTAT_STOPWATCH);
                bfin_write_RTC_SWCNT(rtc->rtc_dev->irq_freq);
                break;
        case RTC_PIE_OFF:
                dev_dbg_stamp(dev);
                bfin_rtc_int_clear(rtc, ~RTC_ISTAT_STOPWATCH);
                break;

        case RTC_UIE_ON:
                dev_dbg_stamp(dev);
                bfin_rtc_int_set(rtc, RTC_ISTAT_SEC);
                break;
        case RTC_UIE_OFF:
                dev_dbg_stamp(dev);
                bfin_rtc_int_clear(rtc, ~RTC_ISTAT_SEC);
                break;

        case RTC_AIE_ON:
                dev_dbg_stamp(dev);
                bfin_rtc_int_set_alarm(rtc);
                break;
        case RTC_AIE_OFF:
                dev_dbg_stamp(dev);
                bfin_rtc_int_clear(rtc, ~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
                break;

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

        return ret;
}

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"
                "periodic_IRQ\t: %s\n",
                yesno(ictl & RTC_ISTAT_ALARM),
                yesno(ictl & RTC_ISTAT_ALARM_DAY),
                yesno(ictl & RTC_ISTAT_SEC),
                yesno(ictl & RTC_ISTAT_STOPWATCH));
        return 0;
#undef yesno
}

/**
 *      bfin_irq_set_freq - make sure hardware supports requested freq
 *      @dev: pointer to RTC device structure
 *      @freq: requested frequency rate
 *
 *      The Blackfin RTC can only generate periodic events at 1 per
 *      second (1 Hz), so reject any attempt at changing it.
 */
static int bfin_irq_set_freq(struct device *dev, int freq)
{
        dev_dbg_stamp(dev);
        return -ENOTTY;
}

static struct rtc_class_ops bfin_rtc_ops = {
        .open          = bfin_rtc_open,
        .release       = bfin_rtc_release,
        .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,
        .irq_set_freq  = bfin_irq_set_freq,
};

static int __devinit bfin_rtc_probe(struct platform_device *pdev)
{
        struct bfin_rtc *rtc;
        int ret = 0;

        dev_dbg_stamp(&pdev->dev);

        rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
        if (unlikely(!rtc))
                return -ENOMEM;

        rtc->rtc_dev = rtc_device_register(pdev->name, &pdev->dev, &bfin_rtc_ops, THIS_MODULE);
        if (unlikely(IS_ERR(rtc))) {
                ret = PTR_ERR(rtc->rtc_dev);
                goto err;
        }
        rtc->rtc_dev->irq_freq = 1;

        platform_set_drvdata(pdev, rtc);

        return 0;

 err:
        kfree(rtc);
        return ret;
}

static int __devexit bfin_rtc_remove(struct platform_device *pdev)
{
        struct bfin_rtc *rtc = platform_get_drvdata(pdev);

        rtc_device_unregister(rtc->rtc_dev);
        platform_set_drvdata(pdev, NULL);
        kfree(rtc);

        return 0;
}

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

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");