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time.c

/*
 * 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/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/clocksource.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 <asm/system.h>

#include "fsyscall_gtod_data.h"

static cycle_t itc_get_cycles(struct clocksource *cs);

struct fsyscall_gtod_data_t fsyscall_gtod_data = {
      .lock = SEQLOCK_UNLOCKED,
};

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),
      .mult           = 0, /*to be calculated*/
      .shift          = 16,
      .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);

/*
 * 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 ia64_account_on_switch(struct task_struct *prev, struct task_struct *next)
{
      struct thread_info *pi = task_thread_info(prev);
      struct thread_info *ni = task_thread_info(next);
      cputime_t delta_stime, delta_utime;
      __u64 now;

      now = ia64_get_itc();

      delta_stime = cycle_to_cputime(pi->ac_stime + (now - pi->ac_stamp));
      if (idle_task(smp_processor_id()) != prev)
            account_system_time(prev, 0, delta_stime, delta_stime);
      else
            account_idle_time(delta_stime);

      if (pi->ac_utime) {
            delta_utime = cycle_to_cputime(pi->ac_utime);
            account_user_time(prev, delta_utime, delta_utime);
      }

      pi->ac_stamp = ni->ac_stamp = now;
      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.
 */
void account_system_vtime(struct task_struct *tsk)
{
      struct thread_info *ti = task_thread_info(tsk);
      unsigned long flags;
      cputime_t delta_stime;
      __u64 now;

      local_irq_save(flags);

      now = ia64_get_itc();

      delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
      if (irq_count() || idle_task(smp_processor_id()) != tsk)
            account_system_time(tsk, 0, delta_stime, delta_stime);
      else
            account_idle_time(delta_stime);
      ti->ac_stime = 0;

      ti->ac_stamp = now;

      local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(account_system_vtime);

/*
 * 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)
{
      struct thread_info *ti = task_thread_info(p);
      cputime_t delta_utime;

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

#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) {
                  /*
                   * 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(1);
                  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;

            /*
             * 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
             * 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;
}

/*
 * 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) {
            /* Sort out mult/shift values: */
            clocksource_itc.mult =
                  clocksource_hz2mult(local_cpu_data->itc_freq,
                                    clocksource_itc.shift);
            clocksource_register(&clocksource_itc);
            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(struct timespec *wall, struct timespec *wtm,
                  struct clocksource *c, u32 mult)
{
        unsigned long flags;

        write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);

        /* 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->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_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
}


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