/*
 * Real Time Clock interface for StrongARM SA1x00 and XScale PXA2xx
 *
 * Copyright (c) 2000 Nils Faerber
 *
 * Based on rtc.c by Paul Gortmaker
 *
 * Original Driver by Nils Faerber <nils@kernelconcepts.de>
 *
 * Modifications from:
 *   CIH <cih@coventive.com>
 *   Nicolas Pitre <nico@fluxnic.net>
 *   Andrew Christian <andrew.christian@hp.com>
 *
 * Converted to the RTC subsystem and Driver Model
 *   by Richard Purdie <rpurdie@rpsys.net>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/platform_device.h>
#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/interrupt.h>
#include <linux/string.h>
#include <linux/pm.h>
#include <linux/bitops.h>

#include <mach/hardware.h>
#include <asm/irq.h>

#ifdef CONFIG_ARCH_PXA
#include <mach/regs-rtc.h>
#include <mach/regs-ost.h>
#endif

#define RTC_DEF_DIVIDER         (32768 - 1)
#define RTC_DEF_TRIM            0

static const unsigned long RTC_FREQ = 1024;
static unsigned long timer_freq;
static struct rtc_time rtc_alarm;
static DEFINE_SPINLOCK(sa1100_rtc_lock);

static inline int rtc_periodic_alarm(struct rtc_time *tm)
{
        return  (tm->tm_year == -1) ||
                ((unsigned)tm->tm_mon >= 12) ||
                ((unsigned)(tm->tm_mday - 1) >= 31) ||
                ((unsigned)tm->tm_hour > 23) ||
                ((unsigned)tm->tm_min > 59) ||
                ((unsigned)tm->tm_sec > 59);
}

/*
 * Calculate the next alarm time given the requested alarm time mask
 * and the current time.
 */
static void rtc_next_alarm_time(struct rtc_time *next, struct rtc_time *now,
        struct rtc_time *alrm)
{
        unsigned long next_time;
        unsigned long now_time;

        next->tm_year = now->tm_year;
        next->tm_mon = now->tm_mon;
        next->tm_mday = now->tm_mday;
        next->tm_hour = alrm->tm_hour;
        next->tm_min = alrm->tm_min;
        next->tm_sec = alrm->tm_sec;

        rtc_tm_to_time(now, &now_time);
        rtc_tm_to_time(next, &next_time);

        if (next_time < now_time) {
                /* Advance one day */
                next_time += 60 * 60 * 24;
                rtc_time_to_tm(next_time, next);
        }
}

static int rtc_update_alarm(struct rtc_time *alrm)
{
        struct rtc_time alarm_tm, now_tm;
        unsigned long now, time;
        int ret;

        do {
                now = RCNR;
                rtc_time_to_tm(now, &now_tm);
                rtc_next_alarm_time(&alarm_tm, &now_tm, alrm);
                ret = rtc_tm_to_time(&alarm_tm, &time);
                if (ret != 0)
                        break;

                RTSR = RTSR & (RTSR_HZE|RTSR_ALE|RTSR_AL);
                RTAR = time;
        } while (now != RCNR);

        return ret;
}

static irqreturn_t sa1100_rtc_interrupt(int irq, void *dev_id)
{
        struct platform_device *pdev = to_platform_device(dev_id);
        struct rtc_device *rtc = platform_get_drvdata(pdev);
        unsigned int rtsr;
        unsigned long events = 0;

        spin_lock(&sa1100_rtc_lock);

        rtsr = RTSR;
        /* clear interrupt sources */
        RTSR = 0;
        /* Fix for a nasty initialization problem the in SA11xx RTSR register.
         * See also the comments in sa1100_rtc_probe(). */
        if (rtsr & (RTSR_ALE | RTSR_HZE)) {
                /* This is the original code, before there was the if test
                 * above. This code does not clear interrupts that were not
                 * enabled. */
                RTSR = (RTSR_AL | RTSR_HZ) & (rtsr >> 2);
        } else {
                /* For some reason, it is possible to enter this routine
                 * without interruptions enabled, it has been tested with
                 * several units (Bug in SA11xx chip?).
                 *
                 * This situation leads to an infinite "loop" of interrupt
                 * routine calling and as a result the processor seems to
                 * lock on its first call to open(). */
                RTSR = RTSR_AL | RTSR_HZ;
        }

        /* clear alarm interrupt if it has occurred */
        if (rtsr & RTSR_AL)
                rtsr &= ~RTSR_ALE;
        RTSR = rtsr & (RTSR_ALE | RTSR_HZE);

        /* update irq data & counter */
        if (rtsr & RTSR_AL)
                events |= RTC_AF | RTC_IRQF;
        if (rtsr & RTSR_HZ)
                events |= RTC_UF | RTC_IRQF;

        rtc_update_irq(rtc, 1, events);

        if (rtsr & RTSR_AL && rtc_periodic_alarm(&rtc_alarm))
                rtc_update_alarm(&rtc_alarm);

        spin_unlock(&sa1100_rtc_lock);

        return IRQ_HANDLED;
}

static int sa1100_irq_set_freq(struct device *dev, int freq)
{
        if (freq < 1 || freq > timer_freq) {
                return -EINVAL;
        } else {
                struct rtc_device *rtc = (struct rtc_device *)dev;

                rtc->irq_freq = freq;

                return 0;
        }
}

static int rtc_timer1_count;

static int sa1100_irq_set_state(struct device *dev, int enabled)
{
        spin_lock_irq(&sa1100_rtc_lock);
        if (enabled) {
                struct rtc_device *rtc = (struct rtc_device *)dev;

                OSMR1 = timer_freq / rtc->irq_freq + OSCR;
                OIER |= OIER_E1;
                rtc_timer1_count = 1;
        } else {
                OIER &= ~OIER_E1;
        }
        spin_unlock_irq(&sa1100_rtc_lock);

        return 0;
}

static inline int sa1100_timer1_retrigger(struct rtc_device *rtc)
{
        unsigned long diff;
        unsigned long period = timer_freq / rtc->irq_freq;

        spin_lock_irq(&sa1100_rtc_lock);

        do {
                OSMR1 += period;
                diff = OSMR1 - OSCR;
                /* If OSCR > OSMR1, diff is a very large number (unsigned
                 * math). This means we have a lost interrupt. */
        } while (diff > period);
        OIER |= OIER_E1;

        spin_unlock_irq(&sa1100_rtc_lock);

        return 0;
}

static irqreturn_t timer1_interrupt(int irq, void *dev_id)
{
        struct platform_device *pdev = to_platform_device(dev_id);
        struct rtc_device *rtc = platform_get_drvdata(pdev);

        /*
         * If we match for the first time, rtc_timer1_count will be 1.
         * Otherwise, we wrapped around (very unlikely but
         * still possible) so compute the amount of missed periods.
         * The match reg is updated only when the data is actually retrieved
         * to avoid unnecessary interrupts.
         */
        OSSR = OSSR_M1; /* clear match on timer1 */

        rtc_update_irq(rtc, rtc_timer1_count, RTC_PF | RTC_IRQF);

        if (rtc_timer1_count == 1)
                rtc_timer1_count =
                        (rtc->irq_freq * ((1 << 30) / (timer_freq >> 2)));

        /* retrigger. */
        sa1100_timer1_retrigger(rtc);

        return IRQ_HANDLED;
}

static int sa1100_rtc_read_callback(struct device *dev, int data)
{
        if (data & RTC_PF) {
                struct rtc_device *rtc = (struct rtc_device *)dev;

                /* interpolate missed periods and set match for the next */
                unsigned long period = timer_freq / rtc->irq_freq;
                unsigned long oscr = OSCR;
                unsigned long osmr1 = OSMR1;
                unsigned long missed = (oscr - osmr1)/period;
                data += missed << 8;
                OSSR = OSSR_M1; /* clear match on timer 1 */
                OSMR1 = osmr1 + (missed + 1)*period;
                /* Ensure we didn't miss another match in the mean time.
                 * Here we compare (match - OSCR) 8 instead of 0 --
                 * see comment in pxa_timer_interrupt() for explanation.
                 */
                while ((signed long)((osmr1 = OSMR1) - OSCR) <= 8) {
                        data += 0x100;
                        OSSR = OSSR_M1; /* clear match on timer 1 */
                        OSMR1 = osmr1 + period;
                }
        }
        return data;
}

static int sa1100_rtc_open(struct device *dev)
{
        int ret;
        struct rtc_device *rtc = (struct rtc_device *)dev;

        ret = request_irq(IRQ_RTC1Hz, sa1100_rtc_interrupt, IRQF_DISABLED,
                "rtc 1Hz", dev);
        if (ret) {
                dev_err(dev, "IRQ %d already in use.\n", IRQ_RTC1Hz);
                goto fail_ui;
        }
        ret = request_irq(IRQ_RTCAlrm, sa1100_rtc_interrupt, IRQF_DISABLED,
                "rtc Alrm", dev);
        if (ret) {
                dev_err(dev, "IRQ %d already in use.\n", IRQ_RTCAlrm);
                goto fail_ai;
        }
        ret = request_irq(IRQ_OST1, timer1_interrupt, IRQF_DISABLED,
                "rtc timer", dev);
        if (ret) {
                dev_err(dev, "IRQ %d already in use.\n", IRQ_OST1);
                goto fail_pi;
        }
        rtc->max_user_freq = RTC_FREQ;
        sa1100_irq_set_freq(dev, RTC_FREQ);

        return 0;

 fail_pi:
        free_irq(IRQ_RTCAlrm, dev);
 fail_ai:
        free_irq(IRQ_RTC1Hz, dev);
 fail_ui:
        return ret;
}

static void sa1100_rtc_release(struct device *dev)
{
        spin_lock_irq(&sa1100_rtc_lock);
        RTSR = 0;
        OIER &= ~OIER_E1;
        OSSR = OSSR_M1;
        spin_unlock_irq(&sa1100_rtc_lock);

        free_irq(IRQ_OST1, dev);
        free_irq(IRQ_RTCAlrm, dev);
        free_irq(IRQ_RTC1Hz, dev);
}


static int sa1100_rtc_ioctl(struct device *dev, unsigned int cmd,
                unsigned long arg)
{
        switch (cmd) {
        case RTC_UIE_OFF:
                spin_lock_irq(&sa1100_rtc_lock);
                RTSR &= ~RTSR_HZE;
                spin_unlock_irq(&sa1100_rtc_lock);
                return 0;
        case RTC_UIE_ON:
                spin_lock_irq(&sa1100_rtc_lock);
                RTSR |= RTSR_HZE;
                spin_unlock_irq(&sa1100_rtc_lock);
                return 0;
        }
        return -ENOIOCTLCMD;
}

static int sa1100_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        spin_lock_irq(&sa1100_rtc_lock);
        if (enabled)
                RTSR |= RTSR_ALE;
        else
                RTSR &= ~RTSR_ALE;
        spin_unlock_irq(&sa1100_rtc_lock);
        return 0;
}

static int sa1100_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        rtc_time_to_tm(RCNR, tm);
        return 0;
}

static int sa1100_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        unsigned long time;
        int ret;

        ret = rtc_tm_to_time(tm, &time);
        if (ret == 0)
                RCNR = time;
        return ret;
}

static int sa1100_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        u32     rtsr;

        memcpy(&alrm->time, &rtc_alarm, sizeof(struct rtc_time));
        rtsr = RTSR;
        alrm->enabled = (rtsr & RTSR_ALE) ? 1 : 0;
        alrm->pending = (rtsr & RTSR_AL) ? 1 : 0;
        return 0;
}

static int sa1100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        int ret;

        spin_lock_irq(&sa1100_rtc_lock);
        ret = rtc_update_alarm(&alrm->time);
        if (ret == 0) {
                if (alrm->enabled)
                        RTSR |= RTSR_ALE;
                else
                        RTSR &= ~RTSR_ALE;
        }
        spin_unlock_irq(&sa1100_rtc_lock);

        return ret;
}

static int sa1100_rtc_proc(struct device *dev, struct seq_file *seq)
{
        struct rtc_device *rtc = (struct rtc_device *)dev;

        seq_printf(seq, "trim/divider\t: 0x%08x\n", (u32) RTTR);
        seq_printf(seq, "update_IRQ\t: %s\n",
                        (RTSR & RTSR_HZE) ? "yes" : "no");
        seq_printf(seq, "periodic_IRQ\t: %s\n",
                        (OIER & OIER_E1) ? "yes" : "no");
        seq_printf(seq, "periodic_freq\t: %d\n", rtc->irq_freq);
        seq_printf(seq, "RTSR\t\t: 0x%08x\n", (u32)RTSR);

        return 0;
}

static const struct rtc_class_ops sa1100_rtc_ops = {
        .open = sa1100_rtc_open,
        .read_callback = sa1100_rtc_read_callback,
        .release = sa1100_rtc_release,
        .ioctl = sa1100_rtc_ioctl,
        .read_time = sa1100_rtc_read_time,
        .set_time = sa1100_rtc_set_time,
        .read_alarm = sa1100_rtc_read_alarm,
        .set_alarm = sa1100_rtc_set_alarm,
        .proc = sa1100_rtc_proc,
        .irq_set_freq = sa1100_irq_set_freq,
        .irq_set_state = sa1100_irq_set_state,
        .alarm_irq_enable = sa1100_rtc_alarm_irq_enable,
};

static int sa1100_rtc_probe(struct platform_device *pdev)
{
        struct rtc_device *rtc;

        timer_freq = get_clock_tick_rate();

        /*
         * According to the manual we should be able to let RTTR be zero
         * and then a default diviser for a 32.768KHz clock is used.
         * Apparently this doesn't work, at least for my SA1110 rev 5.
         * If the clock divider is uninitialized then reset it to the
         * default value to get the 1Hz clock.
         */
        if (RTTR == 0) {
                RTTR = RTC_DEF_DIVIDER + (RTC_DEF_TRIM << 16);
                dev_warn(&pdev->dev, "warning: "
                        "initializing default clock divider/trim value\n");
                /* The current RTC value probably doesn't make sense either */
                RCNR = 0;
        }

        device_init_wakeup(&pdev->dev, 1);

        rtc = rtc_device_register(pdev->name, &pdev->dev, &sa1100_rtc_ops,
                THIS_MODULE);

        if (IS_ERR(rtc))
                return PTR_ERR(rtc);

        platform_set_drvdata(pdev, rtc);

        /* Set the irq_freq */
        /*TODO: Find out who is messing with this value after we initialize
         * it here.*/
        rtc->irq_freq = RTC_FREQ;

        /* Fix for a nasty initialization problem the in SA11xx RTSR register.
         * See also the comments in sa1100_rtc_interrupt().
         *
         * Sometimes bit 1 of the RTSR (RTSR_HZ) will wake up 1, which means an
         * interrupt pending, even though interrupts were never enabled.
         * In this case, this bit it must be reset before enabling
         * interruptions to avoid a nonexistent interrupt to occur.
         *
         * In principle, the same problem would apply to bit 0, although it has
         * never been observed to happen.
         *
         * This issue is addressed both here and in sa1100_rtc_interrupt().
         * If the issue is not addressed here, in the times when the processor
         * wakes up with the bit set there will be one spurious interrupt.
         *
         * The issue is also dealt with in sa1100_rtc_interrupt() to be on the
         * safe side, once the condition that lead to this strange
         * initialization is unknown and could in principle happen during
         * normal processing.
         *
         * Notice that clearing bit 1 and 0 is accomplished by writting ONES to
         * the corresponding bits in RTSR. */
        RTSR = RTSR_AL | RTSR_HZ;

        return 0;
}

static int sa1100_rtc_remove(struct platform_device *pdev)
{
        struct rtc_device *rtc = platform_get_drvdata(pdev);

        if (rtc)
                rtc_device_unregister(rtc);

        return 0;
}

#ifdef CONFIG_PM
static int sa1100_rtc_suspend(struct device *dev)
{
        if (device_may_wakeup(dev))
                enable_irq_wake(IRQ_RTCAlrm);
        return 0;
}

static int sa1100_rtc_resume(struct device *dev)
{
        if (device_may_wakeup(dev))
                disable_irq_wake(IRQ_RTCAlrm);
        return 0;
}

static const struct dev_pm_ops sa1100_rtc_pm_ops = {
        .suspend        = sa1100_rtc_suspend,
        .resume         = sa1100_rtc_resume,
};
#endif

static struct platform_driver sa1100_rtc_driver = {
        .probe          = sa1100_rtc_probe,
        .remove         = sa1100_rtc_remove,
        .driver         = {
                .name   = "sa1100-rtc",
#ifdef CONFIG_PM
                .pm     = &sa1100_rtc_pm_ops,
#endif
        },
};

static int __init sa1100_rtc_init(void)
{
        return platform_driver_register(&sa1100_rtc_driver);
}

static void __exit sa1100_rtc_exit(void)
{
        platform_driver_unregister(&sa1100_rtc_driver);
}

module_init(sa1100_rtc_init);
module_exit(sa1100_rtc_exit);

MODULE_AUTHOR("Richard Purdie <rpurdie@rpsys.net>");
MODULE_DESCRIPTION("SA11x0/PXA2xx Realtime Clock Driver (RTC)");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:sa1100-rtc");