time.c

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/*
 * 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 <[email protected]>
 */

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/clocksource.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>

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

static cycle_t ccount_read(void)
{
    return (cycle_t)get_ccount();
}

static struct clocksource ccount_clocksource = {
    .name = "ccount",
    .rating = 200,
    .read = ccount_read,
    .mask = CLOCKSOURCE_MASK(32),
};

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)
{
#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
    clocksource_register_hz(&ccount_clocksource, CCOUNT_PER_JIFFY * HZ);

    /* Initialize the linux timer interrupt. */

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

/*
 * 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

        xtime_update(1); /* Linux handler in kernel/time/timekeeping */

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

        next += CCOUNT_PER_JIFFY;
        set_linux_timer(next);
    }

    /* 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