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/*

 * linux/arch/ia64/kernel/time.c

 *

 * Copyright (C) 1998-2001 Hewlett-Packard Co

 * Copyright (C) 1998-2000 Stephane Eranian <eranian@hpl.hp.com>

 * Copyright (C) 1999-2001 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/init.h>

#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/time.h>

#include <linux/interrupt.h>

#include <linux/efi.h>

#include <asm/delay.h>

#include <asm/hw_irq.h>

#include <asm/ptrace.h>

#include <asm/sal.h>

#include <asm/system.h>

extern rwlock_t xtime_lock;

extern unsigned long wall_jiffies;

extern unsigned long last_time_offset;

#ifdef CONFIG_IA64_DEBUG_IRQ

unsigned long last_cli_ip;

#endif

static void

do_profile (unsigned long ip)

{

        extern unsigned long prof_cpu_mask;

        extern char _stext;

        if (!prof_buffer)

                return;

        if (!((1UL << smp_processor_id()) & prof_cpu_mask))

                return;

        ip -= (unsigned long) &_stext;

        ip >>= prof_shift;

        /*

         * Don't ignore out-of-bounds IP values silently, put them into the last

         * histogram slot, so if present, they will show up as a sharp peak.

         */

        if (ip > prof_len - 1)

                ip = prof_len - 1;

        atomic_inc((atomic_t *) &prof_buffer[ip]);

}

/*

 * Return the number of micro-seconds that elapsed since the last update to jiffy.  The

 * xtime_lock must be at least read-locked when calling this routine.

 */

static inline unsigned long

gettimeoffset (void)

{

        unsigned long elapsed_cycles, lost = jiffies - wall_jiffies;

        unsigned long now, last_tick;

#       define time_keeper_id   0        /* smp_processor_id() of time-keeper */

        last_tick = (cpu_data(time_keeper_id)->itm_next

                     - (lost + 1)*cpu_data(time_keeper_id)->itm_delta);

        now = ia64_get_itc();

        if ((long) (now - last_tick) < 0) {

                printk(KERN_ERR "CPU %d: now < last_tick (now=0x%lx,last_tick=0x%lx)!\n",

                       smp_processor_id(), now, last_tick);

                return last_time_offset;

        }

        elapsed_cycles = now - last_tick;

        return (elapsed_cycles*local_cpu_data->usec_per_cyc) >> IA64_USEC_PER_CYC_SHIFT;

}

void

do_settimeofday (struct timeval *tv)

{

        write_lock_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 done, and then undo

                 * it!

                 */

                tv->tv_usec -= gettimeoffset();

                while (tv->tv_usec < 0) {

                        tv->tv_usec += 1000000;

                        tv->tv_sec--;

                }

                xtime = *tv;

                time_adjust = 0;         /* stop active adjtime() */

                time_status |= STA_UNSYNC;

                time_maxerror = NTP_PHASE_LIMIT;

                time_esterror = NTP_PHASE_LIMIT;

        }

        write_unlock_irq(&xtime_lock);

}

void

do_gettimeofday (struct timeval *tv)

{

        unsigned long flags, usec, sec, old;

        read_lock_irqsave(&xtime_lock, flags);

        {

                usec = gettimeoffset();

                /*

                 * Ensure time never goes backwards, even when ITC on different CPUs are

                 * not perfectly synchronized.

                 */

                do {

                        old = last_time_offset;

                        if (usec <= old) {

                                usec = old;

                                break;

                        }

                } while (cmpxchg(&last_time_offset, old, usec) != old);

                sec = xtime.tv_sec;

                usec += xtime.tv_usec;

        }

        read_unlock_irqrestore(&xtime_lock, flags);

        while (usec >= 1000000) {

                usec -= 1000000;

                ++sec;

        }

        tv->tv_sec = sec;

        tv->tv_usec = usec;

}

static void

timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)

{

        unsigned long new_itm;

        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);

        while (1) {

                /*

                 * Do kernel PC profiling here.  We multiply the instruction number by

                 * four so that we can use a prof_shift of 2 to get instruction-level

                 * instead of just bundle-level accuracy.

                 */

                if (!user_mode(regs))

                        do_profile(regs->cr_iip + 4*ia64_psr(regs)->ri);

#ifdef CONFIG_SMP

                smp_do_timer(regs);

#endif

                new_itm += local_cpu_data->itm_delta;

                if (smp_processor_id() == 0) {

                        /*

                         * 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_lock(&xtime_lock);

                        do_timer(regs);

                        local_cpu_data->itm_next = new_itm;

                        write_unlock(&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

             * saftey 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));

}

/*

 * Encapsulate access to the itm structure for SMP.

 */

void __init

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);

}

void __init

ia64_init_itm (void)

{

        unsigned long platform_base_freq, itc_freq, drift;

        struct pal_freq_ratio itc_ratio, proc_ratio;

        long status;

        /*

         * 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, &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, 0, &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 reasonably values\n");

                platform_base_freq = 100000000;

                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;

        }

        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_INFO "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%lu/%lu, "

               "ITC freq=%lu.%03luMHz\n", 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);

        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 + 500000) / 1000000;

        local_cpu_data->usec_per_cyc = ((1000000UL<<IA64_USEC_PER_CYC_SHIFT)

                                        + itc_freq/2)/itc_freq;

        /* Setup the CPU local timer tick */

        ia64_cpu_local_tick();

}

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((struct timeval *) &xtime);

        ia64_init_itm();

}