time.c

Go to the documentation of this file.

/*
 * linux/arch/ia64/kernel/time.c
 *
 * Copyright (C) 1998-2003 Hewlett-Packard Co
 *  Stephane Eranian <[email protected]>
 *  David Mosberger <[email protected]>
 * Copyright (C) 1999 Don Dugger <[email protected]>
 * Copyright (C) 1999-2000 VA Linux Systems
 * Copyright (C) 1999-2000 Walt Drummond <[email protected]>
 */

#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/efi.h>
#include <linux/timex.h>
#include <linux/timekeeper_internal.h>
#include <linux/platform_device.h>

#include <asm/machvec.h>
#include <asm/delay.h>
#include <asm/hw_irq.h>
#include <asm/paravirt.h>
#include <asm/ptrace.h>
#include <asm/sal.h>
#include <asm/sections.h>

#include "fsyscall_gtod_data.h"

static cycle_t itc_get_cycles(struct clocksource *cs);

struct fsyscall_gtod_data_t fsyscall_gtod_data;

struct itc_jitter_data_t itc_jitter_data;

volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */

#ifdef CONFIG_IA64_DEBUG_IRQ

unsigned long last_cli_ip;
EXPORT_SYMBOL(last_cli_ip);

#endif

#ifdef CONFIG_PARAVIRT
/* We need to define a real function for sched_clock, to override the
   weak default version */
unsigned long long sched_clock(void)
{
        return paravirt_sched_clock();
}
#endif

#ifdef CONFIG_PARAVIRT
static void
paravirt_clocksource_resume(struct clocksource *cs)
{
    if (pv_time_ops.clocksource_resume)
        pv_time_ops.clocksource_resume();
}
#endif

static struct clocksource clocksource_itc = {
    .name           = "itc",
    .rating         = 350,
    .read           = itc_get_cycles,
    .mask           = CLOCKSOURCE_MASK(64),
    .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
#ifdef CONFIG_PARAVIRT
    .resume     = paravirt_clocksource_resume,
#endif
};
static struct clocksource *itc_clocksource;

#ifdef CONFIG_VIRT_CPU_ACCOUNTING

#include <linux/kernel_stat.h>

extern cputime_t cycle_to_cputime(u64 cyc);

static void vtime_account_user(struct task_struct *tsk)
{
    cputime_t delta_utime;
    struct thread_info *ti = task_thread_info(tsk);

    if (ti->ac_utime) {
        delta_utime = cycle_to_cputime(ti->ac_utime);
        account_user_time(tsk, delta_utime, delta_utime);
        ti->ac_utime = 0;
    }
}

/*
 * Called from the context switch with interrupts disabled, to charge all
 * accumulated times to the current process, and to prepare accounting on
 * the next process.
 */
void vtime_task_switch(struct task_struct *prev)
{
    struct thread_info *pi = task_thread_info(prev);
    struct thread_info *ni = task_thread_info(current);

    if (idle_task(smp_processor_id()) != prev)
        vtime_account_system(prev);
    else
        vtime_account_idle(prev);

    vtime_account_user(prev);

    pi->ac_stamp = ni->ac_stamp;
    ni->ac_stime = ni->ac_utime = 0;
}

/*
 * Account time for a transition between system, hard irq or soft irq state.
 * Note that this function is called with interrupts enabled.
 */
static cputime_t vtime_delta(struct task_struct *tsk)
{
    struct thread_info *ti = task_thread_info(tsk);
    cputime_t delta_stime;
    __u64 now;

    now = ia64_get_itc();

    delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
    ti->ac_stime = 0;
    ti->ac_stamp = now;

    return delta_stime;
}

void vtime_account_system(struct task_struct *tsk)
{
    cputime_t delta = vtime_delta(tsk);

    account_system_time(tsk, 0, delta, delta);
}

void vtime_account_idle(struct task_struct *tsk)
{
    account_idle_time(vtime_delta(tsk));
}

/*
 * Called from the timer interrupt handler to charge accumulated user time
 * to the current process.  Must be called with interrupts disabled.
 */
void account_process_tick(struct task_struct *p, int user_tick)
{
    vtime_account_user(p);
}

#endif /* CONFIG_VIRT_CPU_ACCOUNTING */

static irqreturn_t
timer_interrupt (int irq, void *dev_id)
{
    unsigned long new_itm;

    if (cpu_is_offline(smp_processor_id())) {
        return IRQ_HANDLED;
    }

    platform_timer_interrupt(irq, dev_id);

    new_itm = local_cpu_data->itm_next;

    if (!time_after(ia64_get_itc(), new_itm))
        printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
               ia64_get_itc(), new_itm);

    profile_tick(CPU_PROFILING);

    if (paravirt_do_steal_accounting(&new_itm))
        goto skip_process_time_accounting;

    while (1) {
        update_process_times(user_mode(get_irq_regs()));

        new_itm += local_cpu_data->itm_delta;

        if (smp_processor_id() == time_keeper_id)
            xtime_update(1);

        local_cpu_data->itm_next = new_itm;

        if (time_after(new_itm, ia64_get_itc()))
            break;

        /*
         * Allow IPIs to interrupt the timer loop.
         */
        local_irq_enable();
        local_irq_disable();
    }

skip_process_time_accounting:

    do {
        /*
         * If we're too close to the next clock tick for
         * comfort, we increase the safety margin by
         * intentionally dropping the next tick(s).  We do NOT
         * update itm.next because that would force us to call
         * xtime_update() which in turn would let our clock run
         * too fast (with the potentially devastating effect
         * of losing monotony of time).
         */
        while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
            new_itm += local_cpu_data->itm_delta;
        ia64_set_itm(new_itm);
        /* double check, in case we got hit by a (slow) PMI: */
    } while (time_after_eq(ia64_get_itc(), new_itm));
    return IRQ_HANDLED;
}

/*
 * Encapsulate access to the itm structure for SMP.
 */
void
ia64_cpu_local_tick (void)
{
    int cpu = smp_processor_id();
    unsigned long shift = 0, delta;

    /* arrange for the cycle counter to generate a timer interrupt: */
    ia64_set_itv(IA64_TIMER_VECTOR);

    delta = local_cpu_data->itm_delta;
    /*
     * Stagger the timer tick for each CPU so they don't occur all at (almost) the
     * same time:
     */
    if (cpu) {
        unsigned long hi = 1UL << ia64_fls(cpu);
        shift = (2*(cpu - hi) + 1) * delta/hi/2;
    }
    local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
    ia64_set_itm(local_cpu_data->itm_next);
}

static int nojitter;

static int __init nojitter_setup(char *str)
{
    nojitter = 1;
    printk("Jitter checking for ITC timers disabled\n");
    return 1;
}

__setup("nojitter", nojitter_setup);


void __devinit
ia64_init_itm (void)
{
    unsigned long platform_base_freq, itc_freq;
    struct pal_freq_ratio itc_ratio, proc_ratio;
    long status, platform_base_drift, itc_drift;

    /*
     * According to SAL v2.6, we need to use a SAL call to determine the platform base
     * frequency and then a PAL call to determine the frequency ratio between the ITC
     * and the base frequency.
     */
    status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
                    &platform_base_freq, &platform_base_drift);
    if (status != 0) {
        printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
    } else {
        status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
        if (status != 0)
            printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
    }
    if (status != 0) {
        /* invent "random" values */
        printk(KERN_ERR
               "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
        platform_base_freq = 100000000;
        platform_base_drift = -1;   /* no drift info */
        itc_ratio.num = 3;
        itc_ratio.den = 1;
    }
    if (platform_base_freq < 40000000) {
        printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
               platform_base_freq);
        platform_base_freq = 75000000;
        platform_base_drift = -1;
    }
    if (!proc_ratio.den)
        proc_ratio.den = 1; /* avoid division by zero */
    if (!itc_ratio.den)
        itc_ratio.den = 1;  /* avoid division by zero */

    itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;

    local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
    printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
           "ITC freq=%lu.%03luMHz", smp_processor_id(),
           platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
           itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);

    if (platform_base_drift != -1) {
        itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
        printk("+/-%ldppm\n", itc_drift);
    } else {
        itc_drift = -1;
        printk("\n");
    }

    local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
    local_cpu_data->itc_freq = itc_freq;
    local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
    local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
                    + itc_freq/2)/itc_freq;

    if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
#ifdef CONFIG_SMP
        /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
         * Jitter compensation requires a cmpxchg which may limit
         * the scalability of the syscalls for retrieving time.
         * The ITC synchronization is usually successful to within a few
         * ITC ticks but this is not a sure thing. If you need to improve
         * timer performance in SMP situations then boot the kernel with the
         * "nojitter" option. However, doing so may result in time fluctuating (maybe
         * even going backward) if the ITC offsets between the individual CPUs
         * are too large.
         */
        if (!nojitter)
            itc_jitter_data.itc_jitter = 1;
#endif
    } else
        /*
         * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
         * ITC values may fluctuate significantly between processors.
         * Clock should not be used for hrtimers. Mark itc as only
         * useful for boot and testing.
         *
         * Note that jitter compensation is off! There is no point of
         * synchronizing ITCs since they may be large differentials
         * that change over time.
         *
         * The only way to fix this would be to repeatedly sync the
         * ITCs. Until that time we have to avoid ITC.
         */
        clocksource_itc.rating = 50;

    paravirt_init_missing_ticks_accounting(smp_processor_id());

    /* avoid softlock up message when cpu is unplug and plugged again. */
    touch_softlockup_watchdog();

    /* Setup the CPU local timer tick */
    ia64_cpu_local_tick();

    if (!itc_clocksource) {
        clocksource_register_hz(&clocksource_itc,
                        local_cpu_data->itc_freq);
        itc_clocksource = &clocksource_itc;
    }
}

static cycle_t itc_get_cycles(struct clocksource *cs)
{
    unsigned long lcycle, now, ret;

    if (!itc_jitter_data.itc_jitter)
        return get_cycles();

    lcycle = itc_jitter_data.itc_lastcycle;
    now = get_cycles();
    if (lcycle && time_after(lcycle, now))
        return lcycle;

    /*
     * Keep track of the last timer value returned.
     * In an SMP environment, you could lose out in contention of
     * cmpxchg. If so, your cmpxchg returns new value which the
     * winner of contention updated to. Use the new value instead.
     */
    ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
    if (unlikely(ret != lcycle))
        return ret;

    return now;
}


static struct irqaction timer_irqaction = {
    .handler =  timer_interrupt,
    .flags =    IRQF_DISABLED | IRQF_IRQPOLL,
    .name =     "timer"
};

static struct platform_device rtc_efi_dev = {
    .name = "rtc-efi",
    .id = -1,
};

static int __init rtc_init(void)
{
    if (platform_device_register(&rtc_efi_dev) < 0)
        printk(KERN_ERR "unable to register rtc device...\n");

    /* not necessarily an error */
    return 0;
}
module_init(rtc_init);

void read_persistent_clock(struct timespec *ts)
{
    efi_gettimeofday(ts);
}

void __init
time_init (void)
{
    register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
    ia64_init_itm();
}

/*
 * Generic udelay assumes that if preemption is allowed and the thread
 * migrates to another CPU, that the ITC values are synchronized across
 * all CPUs.
 */
static void
ia64_itc_udelay (unsigned long usecs)
{
    unsigned long start = ia64_get_itc();
    unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;

    while (time_before(ia64_get_itc(), end))
        cpu_relax();
}

void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;

void
udelay (unsigned long usecs)
{
    (*ia64_udelay)(usecs);
}
EXPORT_SYMBOL(udelay);

/* IA64 doesn't cache the timezone */
void update_vsyscall_tz(void)
{
}

void update_vsyscall_old(struct timespec *wall, struct timespec *wtm,
            struct clocksource *c, u32 mult)
{
    write_seqcount_begin(&fsyscall_gtod_data.seq);

        /* copy fsyscall clock data */
        fsyscall_gtod_data.clk_mask = c->mask;
        fsyscall_gtod_data.clk_mult = mult;
        fsyscall_gtod_data.clk_shift = c->shift;
        fsyscall_gtod_data.clk_fsys_mmio = c->archdata.fsys_mmio;
        fsyscall_gtod_data.clk_cycle_last = c->cycle_last;

    /* copy kernel time structures */
        fsyscall_gtod_data.wall_time.tv_sec = wall->tv_sec;
        fsyscall_gtod_data.wall_time.tv_nsec = wall->tv_nsec;
    fsyscall_gtod_data.monotonic_time.tv_sec = wtm->tv_sec
                            + wall->tv_sec;
    fsyscall_gtod_data.monotonic_time.tv_nsec = wtm->tv_nsec
                            + wall->tv_nsec;

    /* normalize */
    while (fsyscall_gtod_data.monotonic_time.tv_nsec >= NSEC_PER_SEC) {
        fsyscall_gtod_data.monotonic_time.tv_nsec -= NSEC_PER_SEC;
        fsyscall_gtod_data.monotonic_time.tv_sec++;
    }

    write_seqcount_end(&fsyscall_gtod_data.seq);
}