FreeBSD/Linux Kernel Cross Reference
sys/i386/xen/clock.c

     /*-
      * Copyright (c) 1990 The Regents of the University of California.
      * All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * William Jolitz and Don Ahn.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: @(#)clock.c       7.2 (Berkeley) 5/12/91
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    /* #define DELAYDEBUG */
    /*
     * Routines to handle clock hardware.
     */
    
    #include "opt_ddb.h"
    #include "opt_clock.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    #include <sys/clock.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/time.h>
    #include <sys/timeet.h>
    #include <sys/timetc.h>
    #include <sys/kernel.h>
    #include <sys/limits.h>
    #include <sys/sysctl.h>
    #include <sys/cons.h>
    #include <sys/power.h>
    
    #include <machine/clock.h>
    #include <machine/cputypes.h>
    #include <machine/frame.h>
    #include <machine/intr_machdep.h>
    #include <machine/md_var.h>
    #include <machine/psl.h>
    #if defined(SMP)
    #include <machine/smp.h>
    #endif
    #include <machine/specialreg.h>
    #include <machine/timerreg.h>
    
    #include <x86/isa/icu.h>
    #include <x86/isa/isa.h>
    #include <isa/rtc.h>
    
    #include <xen/xen_intr.h>
    #include <vm/vm.h>
    #include <vm/pmap.h>
    #include <machine/pmap.h>
    #include <xen/hypervisor.h>
    #include <machine/xen/xen-os.h>
    #include <machine/xen/xenfunc.h>
    #include <xen/interface/vcpu.h>
    #include <machine/cpu.h>
    #include <machine/xen/xen_clock_util.h>
    
    /*
     * 32-bit time_t's can't reach leap years before 1904 or after 2036, so we
     * can use a simple formula for leap years.
     */
    #define LEAPYEAR(y)     (!((y) % 4))
    #define DAYSPERYEAR     (28+30*4+31*7)
    
   #ifndef TIMER_FREQ
   #define TIMER_FREQ      1193182
   #endif
   
   #ifdef CYC2NS_SCALE_FACTOR
   #undef  CYC2NS_SCALE_FACTOR
   #endif
   #define CYC2NS_SCALE_FACTOR     10
   
   /* Values for timerX_state: */
   #define RELEASED        0
   #define RELEASE_PENDING 1
   #define ACQUIRED        2
   #define ACQUIRE_PENDING 3
   
   struct mtx clock_lock;
   #define RTC_LOCK_INIT                                                   \
           mtx_init(&clock_lock, "clk", NULL, MTX_SPIN | MTX_NOPROFILE)
   #define RTC_LOCK        mtx_lock_spin(&clock_lock)
   #define RTC_UNLOCK      mtx_unlock_spin(&clock_lock)
   
   int adjkerntz;          /* local offset from GMT in seconds */
   int clkintr_pending;
   int pscnt = 1;
   int psdiv = 1;
   int wall_cmos_clock;
   u_int timer_freq = TIMER_FREQ;
   static int independent_wallclock;
   static int xen_disable_rtc_set;
   static u_long cyc2ns_scale; 
   static struct timespec shadow_tv;
   static uint32_t shadow_tv_version;      /* XXX: lazy locking */
   static uint64_t processed_system_time;  /* stime (ns) at last processing. */
   
   static  const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
   
   SYSCTL_INT(_machdep, OID_AUTO, independent_wallclock,
       CTLFLAG_RW, &independent_wallclock, 0, "");
   SYSCTL_INT(_machdep, OID_AUTO, xen_disable_rtc_set,
       CTLFLAG_RW, &xen_disable_rtc_set, 1, "");
   
   
   #define do_div(n,base) ({ \
           unsigned long __upper, __low, __high, __mod, __base; \
           __base = (base); \
           __asm("":"=a" (__low), "=d" (__high):"A" (n)); \
           __upper = __high; \
           if (__high) { \
                   __upper = __high % (__base); \
                   __high = __high / (__base); \
           } \
           __asm("divl %2":"=a" (__low), "=d" (__mod):"rm" (__base), "" (__low), "1" (__upper)); \
           __asm("":"=A" (n):"a" (__low),"d" (__high)); \
           __mod; \
   })
   
   
   #define NS_PER_TICK (1000000000ULL/hz)
   
   #define rdtscll(val) \
       __asm__ __volatile__("rdtsc" : "=A" (val))
   
   
   /* convert from cycles(64bits) => nanoseconds (64bits)
    *  basic equation:
    *              ns = cycles / (freq / ns_per_sec)
    *              ns = cycles * (ns_per_sec / freq)
    *              ns = cycles * (10^9 / (cpu_mhz * 10^6))
    *              ns = cycles * (10^3 / cpu_mhz)
    *
    *      Then we use scaling math (suggested by george@mvista.com) to get:
    *              ns = cycles * (10^3 * SC / cpu_mhz) / SC
    *              ns = cycles * cyc2ns_scale / SC
    *
    *      And since SC is a constant power of two, we can convert the div
    *  into a shift.   
    *                      -johnstul@us.ibm.com "math is hard, lets go shopping!"
    */
   static inline void set_cyc2ns_scale(unsigned long cpu_mhz)
   {
           cyc2ns_scale = (1000 << CYC2NS_SCALE_FACTOR)/cpu_mhz;
   }
   
   static inline unsigned long long cycles_2_ns(unsigned long long cyc)
   {
           return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
   }
   
   /*
    * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
    * yielding a 64-bit result.
    */
   static inline uint64_t 
   scale_delta(uint64_t delta, uint32_t mul_frac, int shift)
   {
           uint64_t product;
           uint32_t tmp1, tmp2;
   
           if ( shift < 0 )
                   delta >>= -shift;
           else
                   delta <<= shift;
   
           __asm__ (
                   "mul  %5       ; "
                   "mov  %4,%%eax ; "
                   "mov  %%edx,%4 ; "
                   "mul  %5       ; "
                   "xor  %5,%5    ; "
                   "add  %4,%%eax ; "
                   "adc  %5,%%edx ; "
                   : "=A" (product), "=r" (tmp1), "=r" (tmp2)
                   : "a" ((uint32_t)delta), "1" ((uint32_t)(delta >> 32)), "2" (mul_frac) );
   
           return product;
   }
   
   static uint64_t
   get_nsec_offset(struct shadow_time_info *shadow)
   {
           uint64_t now, delta;
           rdtscll(now);
           delta = now - shadow->tsc_timestamp;
           return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
   }
   
   static void update_wallclock(void)
   {
           shared_info_t *s = HYPERVISOR_shared_info;
   
           do {
                   shadow_tv_version = s->wc_version;
                   rmb();
                   shadow_tv.tv_sec  = s->wc_sec;
                   shadow_tv.tv_nsec = s->wc_nsec;
                   rmb();
           }
           while ((s->wc_version & 1) | (shadow_tv_version ^ s->wc_version));
   
   }
   
   static void
   add_uptime_to_wallclock(void)
   {
           struct timespec ut;
   
           xen_fetch_uptime(&ut);
           timespecadd(&shadow_tv, &ut);
   }
   
   /*
    * Reads a consistent set of time-base values from Xen, into a shadow data
    * area. Must be called with the xtime_lock held for writing.
    */
   static void __get_time_values_from_xen(void)
   {
           shared_info_t           *s = HYPERVISOR_shared_info;
           struct vcpu_time_info   *src;
           struct shadow_time_info *dst;
           uint32_t pre_version, post_version;
   
           src = &s->vcpu_info[smp_processor_id()].time;
           dst = &per_cpu(shadow_time, smp_processor_id());
   
           spinlock_enter();
           do {
                   pre_version = dst->version = src->version;
                   rmb();
                   dst->tsc_timestamp     = src->tsc_timestamp;
                   dst->system_timestamp  = src->system_time;
                   dst->tsc_to_nsec_mul   = src->tsc_to_system_mul;
                   dst->tsc_shift         = src->tsc_shift;
                   rmb();
                   post_version = src->version;
           }
           while ((pre_version & 1) | (pre_version ^ post_version));
   
           dst->tsc_to_usec_mul = dst->tsc_to_nsec_mul / 1000;
           spinlock_exit();
   }
   
   
   static inline int time_values_up_to_date(int cpu)
   {
           struct vcpu_time_info   *src;
           struct shadow_time_info *dst;
   
           src = &HYPERVISOR_shared_info->vcpu_info[cpu].time; 
           dst = &per_cpu(shadow_time, cpu); 
   
           rmb();
           return (dst->version == src->version);
   }
   
   static  unsigned xen_get_timecount(struct timecounter *tc);
   
   static struct timecounter xen_timecounter = {
           xen_get_timecount,      /* get_timecount */
           0,                      /* no poll_pps */
           ~0u,                    /* counter_mask */
           0,                      /* frequency */
           "ixen",                 /* name */
           0                       /* quality */
   };
   
   static struct eventtimer xen_et;
   
   struct xen_et_state {
           int             mode;
   #define MODE_STOP       0
   #define MODE_PERIODIC   1
   #define MODE_ONESHOT    2
           int64_t         period;
           int64_t         next;
   };
   
   static DPCPU_DEFINE(struct xen_et_state, et_state);
   
   static int
   clkintr(void *arg)
   {
           int64_t now;
           int cpu = smp_processor_id();
           struct shadow_time_info *shadow = &per_cpu(shadow_time, cpu);
           struct xen_et_state *state = DPCPU_PTR(et_state);
   
           do {
                   __get_time_values_from_xen();
                   now = shadow->system_timestamp + get_nsec_offset(shadow);
           } while (!time_values_up_to_date(cpu));
   
           /* Process elapsed ticks since last call. */
           processed_system_time = now;
           if (state->mode == MODE_PERIODIC) {
                   while (now >= state->next) {
                           state->next += state->period;
                           if (xen_et.et_active)
                                   xen_et.et_event_cb(&xen_et, xen_et.et_arg);
                   }
                   HYPERVISOR_set_timer_op(state->next + 50000);
           } else if (state->mode == MODE_ONESHOT) {
                   if (xen_et.et_active)
                           xen_et.et_event_cb(&xen_et, xen_et.et_arg);
           }
           /*
            * Take synchronised time from Xen once a minute if we're not
            * synchronised ourselves, and we haven't chosen to keep an independent
            * time base.
            */
           
           if (shadow_tv_version != HYPERVISOR_shared_info->wc_version &&
               !independent_wallclock) {
                   printf("[XEN] hypervisor wallclock nudged; nudging TOD.\n");
                   update_wallclock();
                   add_uptime_to_wallclock();
                   tc_setclock(&shadow_tv);
           }
           
           /* XXX TODO */
           return (FILTER_HANDLED);
   }
   static uint32_t
   getit(void)
   {
           struct shadow_time_info *shadow;
           uint64_t time;
           uint32_t local_time_version;
   
           shadow = &per_cpu(shadow_time, smp_processor_id());
   
           do {
             local_time_version = shadow->version;
             barrier();
             time = shadow->system_timestamp + get_nsec_offset(shadow);
             if (!time_values_up_to_date(smp_processor_id()))
               __get_time_values_from_xen(/*cpu */);
             barrier();
           } while (local_time_version != shadow->version);
   
             return (time);
   }
   
   
   /*
    * XXX: timer needs more SMP work.
    */
   void
   i8254_init(void)
   {
   
           RTC_LOCK_INIT;
   }
   
   /*
    * Wait "n" microseconds.
    * Relies on timer 1 counting down from (timer_freq / hz)
    * Note: timer had better have been programmed before this is first used!
    */
   void
   DELAY(int n)
   {
           int delta, ticks_left;
           uint32_t tick, prev_tick;
   #ifdef DELAYDEBUG
           int getit_calls = 1;
           int n1;
           static int state = 0;
   
           if (state == 0) {
                   state = 1;
                   for (n1 = 1; n1 <= 10000000; n1 *= 10)
                           DELAY(n1);
                   state = 2;
           }
           if (state == 1)
                   printf("DELAY(%d)...", n);
   #endif
           /*
            * Read the counter first, so that the rest of the setup overhead is
            * counted.  Guess the initial overhead is 20 usec (on most systems it
            * takes about 1.5 usec for each of the i/o's in getit().  The loop
            * takes about 6 usec on a 486/33 and 13 usec on a 386/20.  The
            * multiplications and divisions to scale the count take a while).
            *
            * However, if ddb is active then use a fake counter since reading
            * the i8254 counter involves acquiring a lock.  ddb must not go
            * locking for many reasons, but it calls here for at least atkbd
            * input.
            */
           prev_tick = getit();
   
           n -= 0;                 /* XXX actually guess no initial overhead */
           /*
            * Calculate (n * (timer_freq / 1e6)) without using floating point
            * and without any avoidable overflows.
            */
           if (n <= 0)
                   ticks_left = 0;
           else if (n < 256)
                   /*
                    * Use fixed point to avoid a slow division by 1000000.
                    * 39099 = 1193182 * 2^15 / 10^6 rounded to nearest.
                    * 2^15 is the first power of 2 that gives exact results
                    * for n between 0 and 256.
                    */
                   ticks_left = ((u_int)n * 39099 + (1 << 15) - 1) >> 15;
           else
                   /*
                    * Don't bother using fixed point, although gcc-2.7.2
                    * generates particularly poor code for the long long
                    * division, since even the slow way will complete long
                    * before the delay is up (unless we're interrupted).
                    */
                   ticks_left = ((u_int)n * (long long)timer_freq + 999999)
                           / 1000000;
   
           while (ticks_left > 0) {
                   tick = getit();
   #ifdef DELAYDEBUG
                   ++getit_calls;
   #endif
                   delta = tick - prev_tick;
                   prev_tick = tick;
                   if (delta < 0) {
                           /*
                            * Guard against timer0_max_count being wrong.
                            * This shouldn't happen in normal operation,
                            * but it may happen if set_timer_freq() is
                            * traced.
                            */
                           /* delta += timer0_max_count; ??? */
                           if (delta < 0)
                                   delta = 0;
                   }
                   ticks_left -= delta;
           }
   #ifdef DELAYDEBUG
           if (state == 1)
                   printf(" %d calls to getit() at %d usec each\n",
                          getit_calls, (n + 5) / getit_calls);
   #endif
   }
   
   
   /*
    * Restore all the timers non-atomically (XXX: should be atomically).
    *
    * This function is called from pmtimer_resume() to restore all the timers.
    * This should not be necessary, but there are broken laptops that do not
    * restore all the timers on resume.
    */
   void
   timer_restore(void)
   {
           struct xen_et_state *state = DPCPU_PTR(et_state);
   
           /* Get timebases for new environment. */ 
           __get_time_values_from_xen();
   
           /* Reset our own concept of passage of system time. */
           processed_system_time = per_cpu(shadow_time, 0).system_timestamp;
           state->next = processed_system_time;
   }
   
   void
   startrtclock()
   {
           unsigned long long alarm;
           uint64_t __cpu_khz;
           uint32_t cpu_khz;
           struct vcpu_time_info *info;
   
           /* initialize xen values */
           __get_time_values_from_xen();
           processed_system_time = per_cpu(shadow_time, 0).system_timestamp;
   
           __cpu_khz = 1000000ULL << 32;
           info = &HYPERVISOR_shared_info->vcpu_info[0].time;
   
           (void)do_div(__cpu_khz, info->tsc_to_system_mul);
           if ( info->tsc_shift < 0 )
                   cpu_khz = __cpu_khz << -info->tsc_shift;
           else
                   cpu_khz = __cpu_khz >> info->tsc_shift;
   
           printf("Xen reported: %u.%03u MHz processor.\n", 
                  cpu_khz / 1000, cpu_khz % 1000);
   
           /* (10^6 * 2^32) / cpu_hz = (10^3 * 2^32) / cpu_khz =
              (2^32 * 1 / (clocks/us)) */
   
           set_cyc2ns_scale(cpu_khz/1000);
           tsc_freq = cpu_khz * 1000;
   
           timer_freq = 1000000000LL;
           xen_timecounter.tc_frequency = timer_freq >> 9;
           tc_init(&xen_timecounter);
   
           rdtscll(alarm);
   }
   
   /*
    * RTC support routines
    */
   
   
   static __inline int
   readrtc(int port)
   {
           return(bcd2bin(rtcin(port)));
   }
   
   
   #ifdef XEN_PRIVILEGED_GUEST
   
   /*
    * Initialize the time of day register, based on the time base which is, e.g.
    * from a filesystem.
    */
   static void
   domu_inittodr(time_t base)
   {
           unsigned long   sec;
           int             s, y;
           struct timespec ts;
   
           update_wallclock();
           add_uptime_to_wallclock();
           
           RTC_LOCK;
           
           if (base) {
                   ts.tv_sec = base;
                   ts.tv_nsec = 0;
                   tc_setclock(&ts);
           }
   
           sec += tz_minuteswest * 60 + (wall_cmos_clock ? adjkerntz : 0);
   
           y = time_second - shadow_tv.tv_sec;
           if (y <= -2 || y >= 2) {
                   /* badly off, adjust it */
                   tc_setclock(&shadow_tv);
           }
           RTC_UNLOCK;
   }
   
   /*
    * Write system time back to RTC.  
    */
   static void
   domu_resettodr(void)
   {
           unsigned long tm;
           int s;
           dom0_op_t op;
           struct shadow_time_info *shadow;
   
           shadow = &per_cpu(shadow_time, smp_processor_id());
           if (xen_disable_rtc_set)
                   return;
           
           s = splclock();
           tm = time_second;
           splx(s);
           
           tm -= tz_minuteswest * 60 + (wall_cmos_clock ? adjkerntz : 0);
           
           if ((xen_start_info->flags & SIF_INITDOMAIN) &&
               !independent_wallclock)
           {
                   op.cmd = DOM0_SETTIME;
                   op.u.settime.secs        = tm;
                   op.u.settime.nsecs       = 0;
                   op.u.settime.system_time = shadow->system_timestamp;
                   HYPERVISOR_dom0_op(&op);
                   update_wallclock();
                   add_uptime_to_wallclock();
           } else if (independent_wallclock) {
                   /* notyet */
                   ;
           }               
   }
   
   /*
    * Initialize the time of day register, based on the time base which is, e.g.
    * from a filesystem.
    */
   void
   inittodr(time_t base)
   {
           unsigned long   sec, days;
           int             year, month;
           int             y, m, s;
           struct timespec ts;
   
           if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
                   domu_inittodr(base);
                   return;
           }
   
           if (base) {
                   s = splclock();
                   ts.tv_sec = base;
                   ts.tv_nsec = 0;
                   tc_setclock(&ts);
                   splx(s);
           }
   
           /* Look if we have a RTC present and the time is valid */
           if (!(rtcin(RTC_STATUSD) & RTCSD_PWR))
                   goto wrong_time;
   
           /* wait for time update to complete */
           /* If RTCSA_TUP is zero, we have at least 244us before next update */
           s = splhigh();
           while (rtcin(RTC_STATUSA) & RTCSA_TUP) {
                   splx(s);
                   s = splhigh();
           }
   
           days = 0;
   #ifdef USE_RTC_CENTURY
           year = readrtc(RTC_YEAR) + readrtc(RTC_CENTURY) * 100;
   #else
           year = readrtc(RTC_YEAR) + 1900;
           if (year < 1970)
                   year += 100;
   #endif
           if (year < 1970) {
                   splx(s);
                   goto wrong_time;
           }
           month = readrtc(RTC_MONTH);
           for (m = 1; m < month; m++)
                   days += daysinmonth[m-1];
           if ((month > 2) && LEAPYEAR(year))
                   days ++;
           days += readrtc(RTC_DAY) - 1;
           for (y = 1970; y < year; y++)
                   days += DAYSPERYEAR + LEAPYEAR(y);
           sec = ((( days * 24 +
                     readrtc(RTC_HRS)) * 60 +
                   readrtc(RTC_MIN)) * 60 +
                  readrtc(RTC_SEC));
           /* sec now contains the number of seconds, since Jan 1 1970,
              in the local time zone */
   
           sec += tz_minuteswest * 60 + (wall_cmos_clock ? adjkerntz : 0);
   
           y = time_second - sec;
           if (y <= -2 || y >= 2) {
                   /* badly off, adjust it */
                   ts.tv_sec = sec;
                   ts.tv_nsec = 0;
                   tc_setclock(&ts);
           }
           splx(s);
           return;
   
    wrong_time:
           printf("Invalid time in real time clock.\n");
           printf("Check and reset the date immediately!\n");
   }
   
   
   /*
    * Write system time back to RTC
    */
   void
   resettodr()
   {
           unsigned long   tm;
           int             y, m, s;
   
           if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
                   domu_resettodr();
                   return;
           }
                  
           if (xen_disable_rtc_set)
                   return;
   
           s = splclock();
           tm = time_second;
           splx(s);
   
           /* Disable RTC updates and interrupts. */
           writertc(RTC_STATUSB, RTCSB_HALT | RTCSB_24HR);
   
           /* Calculate local time to put in RTC */
   
           tm -= tz_minuteswest * 60 + (wall_cmos_clock ? adjkerntz : 0);
   
           writertc(RTC_SEC, bin2bcd(tm%60)); tm /= 60;    /* Write back Seconds */
           writertc(RTC_MIN, bin2bcd(tm%60)); tm /= 60;    /* Write back Minutes */
           writertc(RTC_HRS, bin2bcd(tm%24)); tm /= 24;    /* Write back Hours   */
   
           /* We have now the days since 01-01-1970 in tm */
           writertc(RTC_WDAY, (tm + 4) % 7 + 1);           /* Write back Weekday */
           for (y = 1970, m = DAYSPERYEAR + LEAPYEAR(y);
                tm >= m;
                y++,      m = DAYSPERYEAR + LEAPYEAR(y))
                   tm -= m;
   
           /* Now we have the years in y and the day-of-the-year in tm */
           writertc(RTC_YEAR, bin2bcd(y%100));             /* Write back Year    */
   #ifdef USE_RTC_CENTURY
           writertc(RTC_CENTURY, bin2bcd(y/100));          /* ... and Century    */
   #endif
           for (m = 0; ; m++) {
                   int ml;
   
                   ml = daysinmonth[m];
                   if (m == 1 && LEAPYEAR(y))
                           ml++;
                   if (tm < ml)
                           break;
                   tm -= ml;
           }
   
           writertc(RTC_MONTH, bin2bcd(m + 1));            /* Write back Month   */
           writertc(RTC_DAY, bin2bcd(tm + 1));             /* Write back Month Day */
   
           /* Reenable RTC updates and interrupts. */
           writertc(RTC_STATUSB, RTCSB_24HR);
           rtcin(RTC_INTR);
   }
   #endif
   
   static int
   xen_et_start(struct eventtimer *et,
       struct bintime *first, struct bintime *period)
   {
           struct xen_et_state *state = DPCPU_PTR(et_state);
           struct shadow_time_info *shadow;
           int64_t fperiod;
   
           __get_time_values_from_xen();
   
           if (period != NULL) {
                   state->mode = MODE_PERIODIC;
                   state->period = (1000000000LL *
                       (uint32_t)(period->frac >> 32)) >> 32;
                   if (period->sec != 0)
                           state->period += 1000000000LL * period->sec;
           } else {
                   state->mode = MODE_ONESHOT;
                   state->period = 0;
           }
           if (first != NULL) {
                   fperiod = (1000000000LL * (uint32_t)(first->frac >> 32)) >> 32;
                   if (first->sec != 0)
                           fperiod += 1000000000LL * first->sec;
           } else
                   fperiod = state->period;
   
           shadow = &per_cpu(shadow_time, smp_processor_id());
           state->next = shadow->system_timestamp + get_nsec_offset(shadow);
           state->next += fperiod;
           HYPERVISOR_set_timer_op(state->next + 50000);
           return (0);
   }
   
   static int
   xen_et_stop(struct eventtimer *et)
   {
           struct xen_et_state *state = DPCPU_PTR(et_state);
   
           state->mode = MODE_STOP;
           HYPERVISOR_set_timer_op(0);
           return (0);
   }
   
   /*
    * Start clocks running.
    */
   void
   cpu_initclocks(void)
   {
           unsigned int time_irq;
           int error;
   
           HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, 0, NULL);
           error = bind_virq_to_irqhandler(VIRQ_TIMER, 0, "cpu0:timer",
               clkintr, NULL, NULL, INTR_TYPE_CLK, &time_irq);
           if (error)
                   panic("failed to register clock interrupt\n");
           /* should fast clock be enabled ? */
   
           bzero(&xen_et, sizeof(xen_et));
           xen_et.et_name = "ixen";
           xen_et.et_flags = ET_FLAGS_PERIODIC | ET_FLAGS_ONESHOT |
               ET_FLAGS_PERCPU;
           xen_et.et_quality = 600;
           xen_et.et_frequency = 0;
           xen_et.et_min_period.sec = 0;
           xen_et.et_min_period.frac = 0x00400000LL << 32;
           xen_et.et_max_period.sec = 2;
           xen_et.et_max_period.frac = 0;
           xen_et.et_start = xen_et_start;
           xen_et.et_stop = xen_et_stop;
           xen_et.et_priv = NULL;
           et_register(&xen_et);
   
           cpu_initclocks_bsp();
   }
   
   int
   ap_cpu_initclocks(int cpu)
   {
           char buf[MAXCOMLEN + 1];
           unsigned int time_irq;
           int error;
   
           HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL);
           snprintf(buf, sizeof(buf), "cpu%d:timer", cpu);
           error = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, buf,
               clkintr, NULL, NULL, INTR_TYPE_CLK, &time_irq);
           if (error)
                   panic("failed to register clock interrupt\n");
   
           return (0);
   }
   
   static uint32_t
   xen_get_timecount(struct timecounter *tc)
   {       
           uint64_t clk;
           struct shadow_time_info *shadow;
           shadow = &per_cpu(shadow_time, smp_processor_id());
   
           __get_time_values_from_xen();
           
           clk = shadow->system_timestamp + get_nsec_offset(shadow);
   
           return (uint32_t)(clk >> 9);
   
   }
   
   /* Return system time offset by ticks */
   uint64_t
   get_system_time(int ticks)
   {
       return processed_system_time + (ticks * NS_PER_TICK);
   }
   
   void
   idle_block(void)
   {
   
           HYPERVISOR_sched_op(SCHEDOP_block, 0);
   }
   
   int
   timer_spkr_acquire(void)
   {
   
           return (0);
   }
   
   int
   timer_spkr_release(void)
   {
   
           return (0);
   }
   
   void
   timer_spkr_setfreq(int freq)
   {
   
   }
   

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