/*
 * arch/xtensa/kernel/time.c
 *
 * Timer and clock support.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2005 Tensilica Inc.
 *
 * Chris Zankel <chris@zankel.net>
 */

#include <linux/errno.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/profile.h>
#include <linux/delay.h>

#include <asm/timex.h>
#include <asm/platform.h>


DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);


#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
unsigned long ccount_per_jiffy;         /* per 1/HZ */
unsigned long nsec_per_ccount;          /* nsec per ccount increment */
#endif

static long last_rtc_update = 0;

/*
 * Scheduler clock - returns current tim in nanosec units.
 */

unsigned long long sched_clock(void)
{
        return (unsigned long long)jiffies * (1000000000 / HZ);
}

static irqreturn_t timer_interrupt(int irq, void *dev_id);
static struct irqaction timer_irqaction = {
        .handler =      timer_interrupt,
        .flags =        IRQF_DISABLED,
        .name =         "timer",
};

void __init time_init(void)
{
        time_t sec_o, sec_n = 0;

        /* The platform must provide a function to calibrate the processor
         * speed for the CALIBRATE.
         */

#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
        printk("Calibrating CPU frequency ");
        platform_calibrate_ccount();
        printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
                        (int)(ccount_per_jiffy/(10000/HZ))%100);
#endif

        /* Set time from RTC (if provided) */

        if (platform_get_rtc_time(&sec_o) == 0)
                while (platform_get_rtc_time(&sec_n))
                        if (sec_o != sec_n)
                                break;

        xtime.tv_nsec = 0;
        last_rtc_update = xtime.tv_sec = sec_n;

        set_normalized_timespec(&wall_to_monotonic,
                -xtime.tv_sec, -xtime.tv_nsec);

        /* Initialize the linux timer interrupt. */

        setup_irq(LINUX_TIMER_INT, &timer_irqaction);
        set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
}


int do_settimeofday(struct timespec *tv)
{
        time_t wtm_sec, sec = tv->tv_sec;
        long wtm_nsec, nsec = tv->tv_nsec;
        unsigned long delta;

        if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
                return -EINVAL;

        write_seqlock_irq(&xtime_lock);

        /* This is revolting. We need to set "xtime" correctly. However, the
         * value in this location is the value at the most recent update of
         * wall time.  Discover what correction gettimeofday() would have
         * made, and then undo it!
         */

        delta = CCOUNT_PER_JIFFY;
        delta += get_ccount() - get_linux_timer();
        nsec -= delta * NSEC_PER_CCOUNT;

        wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
        wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);

        set_normalized_timespec(&xtime, sec, nsec);
        set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);

        ntp_clear();
        write_sequnlock_irq(&xtime_lock);
        return 0;
}

EXPORT_SYMBOL(do_settimeofday);


void do_gettimeofday(struct timeval *tv)
{
        unsigned long flags;
        unsigned long volatile sec, usec, delta, seq;

        do {
                seq = read_seqbegin_irqsave(&xtime_lock, flags);

                sec = xtime.tv_sec;
                usec = (xtime.tv_nsec / NSEC_PER_USEC);

                delta = get_linux_timer() - get_ccount();

        } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));

        usec += (((unsigned long) CCOUNT_PER_JIFFY - delta)
                 * (unsigned long) NSEC_PER_CCOUNT) / NSEC_PER_USEC;

        for (; usec >= 1000000; sec++, usec -= 1000000)
                ;

        tv->tv_sec = sec;
        tv->tv_usec = usec;
}

EXPORT_SYMBOL(do_gettimeofday);

/*
 * The timer interrupt is called HZ times per second.
 */

irqreturn_t timer_interrupt (int irq, void *dev_id)
{

        unsigned long next;

        next = get_linux_timer();

again:
        while ((signed long)(get_ccount() - next) > 0) {

                profile_tick(CPU_PROFILING);
#ifndef CONFIG_SMP
                update_process_times(user_mode(get_irq_regs()));
#endif

                write_seqlock(&xtime_lock);

                do_timer(1); /* Linux handler in kernel/timer.c */

                /* Note that writing CCOMPARE clears the interrupt. */

                next += CCOUNT_PER_JIFFY;
                set_linux_timer(next);

                if (ntp_synced() &&
                    xtime.tv_sec - last_rtc_update >= 659 &&
                    abs((xtime.tv_nsec/1000)-(1000000-1000000/HZ))<5000000/HZ) {

                        if (platform_set_rtc_time(xtime.tv_sec+1) == 0)
                                last_rtc_update = xtime.tv_sec+1;
                        else
                                /* Do it again in 60 s */
                                last_rtc_update += 60;
                }
                write_sequnlock(&xtime_lock);
        }

        /* Allow platform to do something useful (Wdog). */

        platform_heartbeat();

        /* Make sure we didn't miss any tick... */

        if ((signed long)(get_ccount() - next) > 0)
                goto again;

        return IRQ_HANDLED;
}

#ifndef CONFIG_GENERIC_CALIBRATE_DELAY
void __cpuinit calibrate_delay(void)
{
        loops_per_jiffy = CCOUNT_PER_JIFFY;
        printk("Calibrating delay loop (skipped)... "
               "%lu.%02lu BogoMIPS preset\n",
               loops_per_jiffy/(1000000/HZ),
               (loops_per_jiffy/(10000/HZ)) % 100);
}
#endif