source: trunk/packages/xen-common/xen-common/xen/arch/ia64/linux-xen/time.c @ 34

/*
 * linux/arch/ia64/kernel/time.c
 *
 * Copyright (C) 1998-2003 Hewlett-Packard Co
 *      Stephane Eranian <eranian@hpl.hp.com>
 *      David Mosberger <davidm@hpl.hp.com>
 * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
 * Copyright (C) 1999-2000 VA Linux Systems
 * Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
 */
#include <linux/config.h>

#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/profile.h>
#include <linux/timex.h>

#include <asm/machvec.h>
#include <asm/delay.h>
#include <asm/hw_irq.h>
#include <asm/ptrace.h>
#include <asm/sal.h>
#include <asm/sections.h>
#include <asm/system.h>
#ifdef XEN
#include <linux/jiffies.h>      // not included by xen/sched.h
#endif

extern unsigned long wall_jiffies;

u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;

EXPORT_SYMBOL(jiffies_64);

#define 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

#ifndef XEN
static struct time_interpolator itc_interpolator = {
        .shift = 16,
        .mask = 0xffffffffffffffffLL,
        .source = TIME_SOURCE_CPU
};

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

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

        platform_timer_interrupt(irq, dev_id, regs);

        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, regs);

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

                new_itm += local_cpu_data->itm_delta;

                if (smp_processor_id() == TIME_KEEPER_ID) {
                        /*
                         * Here we are in the timer irq handler. We have irqs locally
                         * disabled, but we don't know if the timer_bh is running on
                         * another CPU. We need to avoid to SMP race by acquiring the
                         * xtime_lock.
                         */
                        write_seqlock(&xtime_lock);
                        do_timer(regs);
                        local_cpu_data->itm_next = new_itm;
                        write_sequnlock(&xtime_lock);
                } else
                        local_cpu_data->itm_next = new_itm;

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

        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
                 * do_timer() 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;
}
#endif

/*
 * 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;
#ifdef XEN /* warning cleanup */
        unsigned long status, platform_base_drift, itc_drift;
#else
        long status, platform_base_drift, itc_drift;
#endif

        /*
         * 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=%lu/%lu, "
               "ITC freq=%lu.%03luMHz", smp_processor_id(),
               platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
#ifdef XEN
               (u64)itc_ratio.num, (u64)itc_ratio.den,
               itc_freq / 1000000, (itc_freq / 1000) % 1000);
#else
               itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
#endif

        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)) {
#ifndef XEN
                itc_interpolator.frequency = local_cpu_data->itc_freq;
                itc_interpolator.drift = 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_interpolator.jitter = 1;
#endif
                register_time_interpolator(&itc_interpolator);
#endif
        }

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

#ifndef XEN
static struct irqaction timer_irqaction = {
        .handler =      timer_interrupt,
        .flags =        SA_INTERRUPT,
        .name =         "timer"
};

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

        /*
         * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
         * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
         */
        set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
}
#endif