ppc64/kernel/time.c

/*
 *
 * Common time routines among all ppc machines.
 *
 * Written by Cort Dougan (cort@cs.nmt.edu) to merge
 * Paul Mackerras' version and mine for PReP and Pmac.
 * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
 * Converted for 64-bit by Mike Corrigan (mikejc@us.ibm.com)
 *
 * First round of bugfixes by Gabriel Paubert (paubert@iram.es)
 * to make clock more stable (2.4.0-test5). The only thing
 * that this code assumes is that the timebases have been synchronized
 * by firmware on SMP and are never stopped (never do sleep
 * on SMP then, nap and doze are OK).
 *
 * Speeded up do_gettimeofday by getting rid of references to
 * xtime (which required locks for consistency). (mikejc@us.ibm.com)
 *
 * TODO (not necessarily in this file):
 * - improve precision and reproducibility of timebase frequency
 * measurement at boot time. (for iSeries, we calibrate the timebase
 * against the Titan chip's clock.)
 * - for astronomical applications: add a new function to get
 * non ambiguous timestamps even around leap seconds. This needs
 * a new timestamp format and a good name.
 *
 * 1997-09-10  Updated NTP code according to technical memorandum Jan '96
 *             "A Kernel Model for Precision Timekeeping" by Dave Mills
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#include <linux/config.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/kernel_stat.h>
#include <linux/mc146818rtc.h>
#include <linux/time.h>
#include <linux/init.h>

#include <asm/naca.h>
#include <asm/segment.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/nvram.h>
#include <asm/cache.h>
#include <asm/machdep.h>
#include <asm/init.h>
#ifdef CONFIG_PPC_ISERIES
#include <asm/iSeries/HvCallXm.h>
#endif
#include <asm/uaccess.h>

#include <asm/time.h>
#include <asm/ppcdebug.h>

void smp_local_timer_interrupt(struct pt_regs *);

extern void setup_before_console_init();

/* keep track of when we need to update the rtc */
time_t last_rtc_update;
extern rwlock_t xtime_lock;
extern int piranha_simulator;
#ifdef CONFIG_PPC_ISERIES
unsigned long iSeries_recal_titan = 0;
unsigned long iSeries_recal_tb = 0;
static unsigned long first_settimeofday = 1;
#endif

#define XSEC_PER_SEC (1024*1024)
#define USEC_PER_SEC (1000000)

unsigned long tb_ticks_per_jiffy;
unsigned long tb_ticks_per_usec;
unsigned long tb_ticks_per_sec;
unsigned long next_xtime_sync_tb;
unsigned long xtime_sync_interval;
unsigned long tb_to_xs;
unsigned long processor_freq;
spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;

extern unsigned long wall_jiffies;
extern unsigned long lpEvent_count;
extern int smp_tb_synchronized;

extern unsigned long prof_cpu_mask;
extern unsigned int * prof_buffer;
extern unsigned long prof_len;
extern unsigned long prof_shift;
extern char _stext;

extern struct timezone sys_tz;

void ppc_adjtimex(void);

static unsigned adjusting_time = 0;

static void ppc_do_profile (unsigned long nip)
{
	/*
	 * Only measure the CPUs specified by /proc/irq/prof_cpu_mask.
	 * (default is all CPUs.)
	 */
	if (!((1<<smp_processor_id()) & prof_cpu_mask))
		return;

	nip -= (unsigned long) &_stext;
	nip >>= prof_shift;
	/*
	 * Don't ignore out-of-bounds EIP values silently,
	 * put them into the last histogram slot, so if
	 * present, they will show up as a sharp peak.
	 */
	if (nip > prof_len-1)
		nip = prof_len-1;
	atomic_inc((atomic_t *)&prof_buffer[nip]);
}


static __inline__ void timer_check_rtc(void)
{
        /*
         * update the rtc when needed, this should be performed on the
         * right fraction of a second. Half or full second ?
         * Full second works on mk48t59 clocks, others need testing.
         * Note that this update is basically only used through
         * the adjtimex system calls. Setting the HW clock in
         * any other way is a /dev/rtc and userland business.
         * This is still wrong by -0.5/+1.5 jiffies because of the
         * timer interrupt resolution and possible delay, but here we
         * hit a quantization limit which can only be solved by higher
         * resolution timers and decoupling time management from timer
         * interrupts. This is also wrong on the clocks
         * which require being written at the half second boundary.
         * We should have an rtc call that only sets the minutes and
         * seconds like on Intel to avoid problems with non UTC clocks.
         */
        if ( (time_status & STA_UNSYNC) == 0 &&
             xtime.tv_sec - last_rtc_update >= 659 &&
             abs(xtime.tv_usec - (1000000-1000000/HZ)) < 500000/HZ &&
             jiffies - wall_jiffies == 1) {
	    struct rtc_time tm;
	    to_tm(xtime.tv_sec+1, &tm);
	    tm.tm_year -= 1900;
	    tm.tm_mon -= 1;
            if (ppc_md.set_rtc_time(&tm) == 0)
                last_rtc_update = xtime.tv_sec+1;
            else
                /* Try again one minute later */
                last_rtc_update += 60;
        }
}

/* Synchronize xtime with do_gettimeofday */

static __inline__ void timer_sync_xtime( unsigned long cur_tb )
{
	struct timeval my_tv;

	if ( cur_tb > next_xtime_sync_tb ) {
		next_xtime_sync_tb = cur_tb + xtime_sync_interval;
		do_gettimeofday( &my_tv );
		if ( xtime.tv_sec <= my_tv.tv_sec ) {
			xtime.tv_sec = my_tv.tv_sec;
			xtime.tv_usec = my_tv.tv_usec;
		}
	}
}

#ifdef CONFIG_PPC_ISERIES

/*
 * This function recalibrates the timebase based on the 49-bit time-of-day
 * value in the Titan chip.  The Titan is much more accurate than the value
 * returned by the service processor for the timebase frequency.
 */

static void iSeries_tb_recal(void)
{
	struct div_result divres;
	unsigned long titan, tb;
	tb = get_tb();
	titan = HvCallXm_loadTod();
	if ( iSeries_recal_titan ) {
		unsigned long tb_ticks = tb - iSeries_recal_tb;
		unsigned long titan_usec = (titan - iSeries_recal_titan) >> 12;
		unsigned long new_tb_ticks_per_sec   = (tb_ticks * USEC_PER_SEC)/titan_usec;
		unsigned long new_tb_ticks_per_jiffy = (new_tb_ticks_per_sec+(HZ/2))/HZ;
		long tick_diff = new_tb_ticks_per_jiffy - tb_ticks_per_jiffy;
		char sign = '+';
		/* make sure tb_ticks_per_sec and tb_ticks_per_jiffy are consistent */
		new_tb_ticks_per_sec = new_tb_ticks_per_jiffy * HZ;

		if ( tick_diff < 0 ) {
			tick_diff = -tick_diff;
			sign = '-';
		}
		if ( tick_diff ) {
			if ( tick_diff < tb_ticks_per_jiffy/25 ) {
				printk( "Titan recalibrate: new tb_ticks_per_jiffy = %lu (%c%ld)\n",
						new_tb_ticks_per_jiffy, sign, tick_diff );
				tb_ticks_per_jiffy = new_tb_ticks_per_jiffy;
				tb_ticks_per_sec   = new_tb_ticks_per_sec;
				div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres );
				systemcfg->tb_ticks_per_sec = tb_ticks_per_sec;
				tb_to_xs = divres.result_low;
				systemcfg->tb_to_xs = tb_to_xs;
			}
			else {
				printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
					"                   new tb_ticks_per_jiffy = %lu\n"
					"                   old tb_ticks_per_jiffy = %lu\n",
					new_tb_ticks_per_jiffy, tb_ticks_per_jiffy );
			}
		}
	}
	iSeries_recal_titan = titan;
	iSeries_recal_tb = tb;
}
#endif

/*
 * For iSeries shared processors, we have to let the hypervisor
 * set the hardware decrementer.  We set a virtual decrementer
 * in the ItLpPaca and call the hypervisor if the virtual
 * decrementer is less than the current value in the hardware
 * decrementer. (almost always the new decrementer value will
 * be greater than the current hardware decementer so the hypervisor
 * call will not be needed)
 */

unsigned long tb_last_stamp=0;

/*
 * timer_interrupt - gets called when the decrementer overflows,
 * with interrupts disabled.
 */
int timer_interrupt(struct pt_regs * regs)
{
	int next_dec;
	unsigned long cur_tb;
	struct paca_struct *lpaca = get_paca();
	unsigned long cpu = lpaca->xPacaIndex;
	struct ItLpQueue * lpq;

	irq_enter(cpu);

	if ((!user_mode(regs)) && (prof_buffer))
		ppc_do_profile(instruction_pointer(regs));

	pmc_timeslice_tick(); /* Hack this in for now */

	lpaca->xLpPaca.xIntDword.xFields.xDecrInt = 0;

	while (lpaca->next_jiffy_update_tb <= (cur_tb = get_tb())) {

#ifdef CONFIG_SMP
		smp_local_timer_interrupt(regs);
#endif
		if (cpu == 0) {
			write_lock(&xtime_lock);
			tb_last_stamp = lpaca->next_jiffy_update_tb;
			do_timer(regs);
			timer_sync_xtime( cur_tb );
			timer_check_rtc();
			write_unlock(&xtime_lock);
			if ( adjusting_time && (time_adjust == 0) )
				ppc_adjtimex();
		}
		lpaca->next_jiffy_update_tb += tb_ticks_per_jiffy;
	}

	next_dec = lpaca->next_jiffy_update_tb - cur_tb;
	if (next_dec > lpaca->default_decr)
        	next_dec = lpaca->default_decr;
	set_dec(next_dec);

	lpq = lpaca->lpQueuePtr;
	if (lpq && ItLpQueue_isLpIntPending(lpq))
		lpEvent_count += ItLpQueue_process(lpq, regs);

	irq_exit(cpu);

	if (softirq_pending(cpu))
		do_softirq();

	return 1;
}


/*
 * This version of gettimeofday has microsecond resolution.
 */
void do_gettimeofday(struct timeval *tv)
{
        unsigned long sec, usec, tb_ticks;
	unsigned long xsec, tb_xsec;
	unsigned long temp_tb_to_xs, temp_stamp_xsec;
	unsigned long tb_count_1, tb_count_2;
	unsigned long always_zero;
	struct systemcfg *gtdp;

	gtdp = systemcfg;
	/*
	 * The following loop guarantees that we see a consistent view of the
	 * tb_to_xs and stamp_xsec variables.  These two variables can change
	 * (eg. when xntpd adjusts the clock frequency) and an inconsistent
	 * view (one variable changed, the other not) could result in a wildly
	 * wrong result for do_gettimeofday.
	 *
	 * The code which updates these variables (ppc_adjtimex below)
	 * increments tb_update_count, then updates the two variables and then
	 * increments tb_update_count again.  This code reads tb_update_count,
	 * reads the two variables and then reads tb_update_count again.  It
	 * loops doing this until the two reads of tb_update_count yield the
	 * same value and that value is even.  This ensures a consistent view
	 * of the two variables.
	 *
	 * The strange looking assembler code below causes the hardware to
	 * think that reading the two variables is dependent on the first read
	 * of tb_update_count and that the second reading of tb_update_count is
	 * dependent on reading the two variables.  This assures ordering
	 * without the need for a lwsync, which is much more expensive.
	 */
	do {
		tb_ticks = get_tb() - gtdp->tb_orig_stamp;

		tb_count_1 = gtdp->tb_update_count;

		__asm__ __volatile__ (
"		andc 	%0,%2,%2\n\
		add	%1,%3,%0\n\
"		: "=&r"(always_zero), "=r"(gtdp)
		: "r"(tb_count_1), "r"(gtdp) );

		temp_tb_to_xs = gtdp->tb_to_xs;
		temp_stamp_xsec = gtdp->stamp_xsec;

		__asm__ __volatile__ (
"		add	%0,%2,%3\n\
		andc	%0,%0,%0\n\
		add	%1,%4,%0\n\
"		: "=&r"(always_zero), "=r"(gtdp)
		: "r"(temp_stamp_xsec), "r"(temp_tb_to_xs), "r"(gtdp) );

		tb_count_2 = gtdp->tb_update_count;

	} while ( tb_count_2 - ( tb_count_1 & 0xfffffffffffffffe ) );

	/* These calculations are faster (gets rid of divides)
	 * if done in units of 1/2^20 rather than microseconds.
	 * The conversion to microseconds at the end is done
	 * without a divide (and in fact, without a multiply) */
	tb_xsec = mulhdu( tb_ticks, temp_tb_to_xs );
	xsec = temp_stamp_xsec + tb_xsec;
	sec = xsec / XSEC_PER_SEC;
	xsec -= sec * XSEC_PER_SEC;
	usec = (xsec * USEC_PER_SEC)/XSEC_PER_SEC;

        tv->tv_sec = sec;
        tv->tv_usec = usec;
}

void do_settimeofday(struct timeval *tv)
{
	unsigned long flags;
	unsigned long delta_xsec;
	long int tb_delta, new_usec, new_sec;
	unsigned long new_xsec;

	write_lock_irqsave(&xtime_lock, flags);
	/* Updating the RTC is not the job of this code. If the time is
	 * stepped under NTP, the RTC will be update after STA_UNSYNC
	 * is cleared. Tool like clock/hwclock either copy the RTC
	 * to the system time, in which case there is no point in writing
	 * to the RTC again, or write to the RTC but then they don't call
	 * settimeofday to perform this operation.
	 */
#ifdef CONFIG_PPC_ISERIES
	if ( first_settimeofday ) {
		iSeries_tb_recal();
		first_settimeofday = 0;
	}
#endif
	tb_delta = tb_ticks_since(tb_last_stamp);
	tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;

	new_sec = tv->tv_sec;
	new_usec = tv->tv_usec - tb_delta / tb_ticks_per_usec;
	while (new_usec <0) {
		new_sec--;
		new_usec += USEC_PER_SEC;
	}
	xtime.tv_usec = new_usec;
	xtime.tv_sec = new_sec;

	/* In case of a large backwards jump in time with NTP, we want the
	 * clock to be updated as soon as the PLL is again in lock.
	 */
	last_rtc_update = new_sec - 658;

	time_adjust = 0;                /* stop active adjtime() */
	time_status |= STA_UNSYNC;
	time_maxerror = NTP_PHASE_LIMIT;
	time_esterror = NTP_PHASE_LIMIT;

	delta_xsec = mulhdu( (tb_last_stamp-systemcfg->tb_orig_stamp), systemcfg->tb_to_xs );
	new_xsec = (tv->tv_usec * XSEC_PER_SEC) / USEC_PER_SEC;
	new_xsec += tv->tv_sec * XSEC_PER_SEC;
	if ( new_xsec > delta_xsec ) {
		systemcfg->stamp_xsec = new_xsec - delta_xsec;
	}
	else {
		/* This is only for the case where the user is setting the time
		 * way back to a time such that the boot time would have been
		 * before 1970 ... eg. we booted ten days ago, and we are
		 * setting the time to Jan 5, 1970 */
		systemcfg->stamp_xsec = new_xsec;
		systemcfg->tb_orig_stamp = tb_last_stamp;
	}

	systemcfg->tz_minuteswest = sys_tz.tz_minuteswest;
	systemcfg->tz_dsttime = sys_tz.tz_dsttime;

	write_unlock_irqrestore(&xtime_lock, flags);
}

/*
 * This function is a copy of the architecture independent function
 * but which calls do_settimeofday rather than setting the xtime
 * fields itself.  This way, the fields which are used for
 * do_settimeofday get updated too.
 */
long ppc64_sys32_stime(int* tptr)
{
	int value;
	struct timeval myTimeval;

	if (!capable(CAP_SYS_TIME))
		return -EPERM;

	if (get_user(value, tptr))
		return -EFAULT;

	myTimeval.tv_sec = value;
	myTimeval.tv_usec = 0;

	do_settimeofday(&myTimeval);

	return 0;
}

/*
 * This function is a copy of the architecture independent function
 * but which calls do_settimeofday rather than setting the xtime
 * fields itself.  This way, the fields which are used for
 * do_settimeofday get updated too.
 */
long ppc64_sys_stime(long* tptr)
{
	long value;
	struct timeval myTimeval;

	if (!capable(CAP_SYS_TIME))
		return -EPERM;

	if (get_user(value, tptr))
		return -EFAULT;

	myTimeval.tv_sec = value;
	myTimeval.tv_usec = 0;

	do_settimeofday(&myTimeval);

	return 0;
}

void __init time_init(void)
{
	/* This function is only called on the boot processor */
	unsigned long flags;
	struct rtc_time tm;

	ppc_md.calibrate_decr();

	if ( ! piranha_simulator ) {
		ppc_md.get_boot_time(&tm);
	}
	write_lock_irqsave(&xtime_lock, flags);
	xtime.tv_sec = mktime(tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
			      tm.tm_hour, tm.tm_min, tm.tm_sec);
	tb_last_stamp = get_tb();
	systemcfg->tb_orig_stamp = tb_last_stamp;
	systemcfg->tb_update_count = 0;
	systemcfg->tb_ticks_per_sec = tb_ticks_per_sec;
	systemcfg->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC;
	systemcfg->tb_to_xs = tb_to_xs;

	xtime_sync_interval = tb_ticks_per_sec - (tb_ticks_per_sec/8);
	next_xtime_sync_tb = tb_last_stamp + xtime_sync_interval;

	time_freq = 0;

	xtime.tv_usec = 0;
	last_rtc_update = xtime.tv_sec;
	write_unlock_irqrestore(&xtime_lock, flags);

	/* Not exact, but the timer interrupt takes care of this */
	set_dec(tb_ticks_per_jiffy);

	/* This horrible hack gives setup a hook just before console_init */
	setup_before_console_init();
}

/*
 * After adjtimex is called, adjust the conversion of tb ticks
 * to microseconds to keep do_gettimeofday synchronized
 * with ntpd.
 *
 * Use the time_adjust, time_freq and time_offset computed by adjtimex to
 * adjust the frequency.
 */

/* #define DEBUG_PPC_ADJTIMEX 1 */

void ppc_adjtimex(void)
{
	unsigned long den, new_tb_ticks_per_sec, tb_ticks, old_xsec, new_tb_to_xs, new_xsec, new_stamp_xsec;
	unsigned long tb_ticks_per_sec_delta;
	long delta_freq, ltemp;
	struct div_result divres;
	unsigned long flags;
	long singleshot_ppm = 0;

	/* Compute parts per million frequency adjustment to accomplish the time adjustment
	   implied by time_offset to be applied over the elapsed time indicated by time_constant.
	   Use SHIFT_USEC to get it into the same units as time_freq. */
	if ( time_offset < 0 ) {
		ltemp = -time_offset;
		ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
		ltemp >>= SHIFT_KG + time_constant;
		ltemp = -ltemp;
	}
	else {
		ltemp = time_offset;
		ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
		ltemp >>= SHIFT_KG + time_constant;
	}

	/* If there is a single shot time adjustment in progress */
	if ( time_adjust ) {
#ifdef DEBUG_PPC_ADJTIMEX
		printk("ppc_adjtimex: ");
		if ( adjusting_time == 0 )
			printk("starting ");
		printk("single shot time_adjust = %ld\n", time_adjust);
#endif

		adjusting_time = 1;

		/* Compute parts per million frequency adjustment to match time_adjust */
		singleshot_ppm = tickadj * HZ;
		/*
		 * The adjustment should be tickadj*HZ to match the code in
		 * linux/kernel/timer.c, but experiments show that this is too
		 * large. 3/4 of tickadj*HZ seems about right
		 */
		singleshot_ppm -= singleshot_ppm / 4;
		/* Use SHIFT_USEC to get it into the same units as time_freq */
		singleshot_ppm <<= SHIFT_USEC;
		if ( time_adjust < 0 )
			singleshot_ppm = -singleshot_ppm;
	}
	else {
#ifdef DEBUG_PPC_ADJTIMEX
		if ( adjusting_time )
			printk("ppc_adjtimex: ending single shot time_adjust\n");
#endif
		adjusting_time = 0;
	}

	/* Add up all of the frequency adjustments */
	delta_freq = time_freq + ltemp + singleshot_ppm;

	/* Compute a new value for tb_ticks_per_sec based on the frequency adjustment */
	den = 1000000 * (1 << (SHIFT_USEC - 8));
	if ( delta_freq < 0 ) {
		tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( (-delta_freq) >> (SHIFT_USEC - 8))) / den;
		new_tb_ticks_per_sec = tb_ticks_per_sec + tb_ticks_per_sec_delta;
	}
	else {
		tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( delta_freq >> (SHIFT_USEC - 8))) / den;
		new_tb_ticks_per_sec = tb_ticks_per_sec - tb_ticks_per_sec_delta;
	}

#ifdef DEBUG_PPC_ADJTIMEX
	printk("ppc_adjtimex: ltemp = %ld, time_freq = %ld, singleshot_ppm = %ld\n", ltemp, time_freq, singleshot_ppm);
	printk("ppc_adjtimex: tb_ticks_per_sec - base = %ld  new = %ld\n", tb_ticks_per_sec, new_tb_ticks_per_sec);
#endif

	/*
	 * Compute a new value of tb_to_xs (used to convert tb to microseconds
	 * and a new value of stamp_xsec which is the time (in 1/2^20 second
	 * units) corresponding to tb_orig_stamp.  This new value of stamp_xsec
	 * compensates for the change in frequency (implied by the new
	 * tb_to_xs) and so guarantees that the current time remains the same
	 *
	 */
	tb_ticks = get_tb() - systemcfg->tb_orig_stamp;
	div128_by_32( 1024*1024, 0, new_tb_ticks_per_sec, &divres );
	new_tb_to_xs = divres.result_low;
	new_xsec = mulhdu( tb_ticks, new_tb_to_xs );

	write_lock_irqsave( &xtime_lock, flags );
	old_xsec = mulhdu( tb_ticks, systemcfg->tb_to_xs );
	new_stamp_xsec = systemcfg->stamp_xsec + old_xsec - new_xsec;

	/*
	 * tb_update_count is used to allow the problem state gettimeofday code
	 * to assure itself that it sees a consistent view of the tb_to_xs and
	 * stamp_xsec variables.  It reads the tb_update_count, then reads
	 * tb_to_xs and stamp_xsec and then reads tb_update_count again.  If
	 * the two values of tb_update_count match and are even then the
	 * tb_to_xs and stamp_xsec values are consistent.  If not, then it
	 * loops back and reads them again until this criteria is met.
	 */
	++(systemcfg->tb_update_count);
	wmb();
	systemcfg->tb_to_xs = new_tb_to_xs;
	systemcfg->stamp_xsec = new_stamp_xsec;
	wmb();
	++(systemcfg->tb_update_count);

	write_unlock_irqrestore( &xtime_lock, flags );

}


#define TICK_SIZE tick
#define FEBRUARY	2
#define	STARTOFTIME	1970
#define SECDAY		86400L
#define SECYR		(SECDAY * 365)
#define	leapyear(year)		((year) % 4 == 0)
#define	days_in_year(a) 	(leapyear(a) ? 366 : 365)
#define	days_in_month(a) 	(month_days[(a) - 1])

static int month_days[12] = {
	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

/*
 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
 */
void GregorianDay(struct rtc_time * tm)
{
	int leapsToDate;
	int lastYear;
	int day;
	int MonthOffset[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };

	lastYear=tm->tm_year-1;

	/*
	 * Number of leap corrections to apply up to end of last year
	 */
	leapsToDate = lastYear/4 - lastYear/100 + lastYear/400;

	/*
	 * This year is a leap year if it is divisible by 4 except when it is
	 * divisible by 100 unless it is divisible by 400
	 *
	 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be
	 */
	if((tm->tm_year%4==0) &&
	   ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) &&
	   (tm->tm_mon>2))
	{
		/*
		 * We are past Feb. 29 in a leap year
		 */
		day=1;
	}
	else
	{
		day=0;
	}

	day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] +
		   tm->tm_mday;

	tm->tm_wday=day%7;
}

void to_tm(int tim, struct rtc_time * tm)
{
	register int    i;
	register long   hms, day;

	day = tim / SECDAY;
	hms = tim % SECDAY;

	/* Hours, minutes, seconds are easy */
	tm->tm_hour = hms / 3600;
	tm->tm_min = (hms % 3600) / 60;
	tm->tm_sec = (hms % 3600) % 60;

	/* Number of years in days */
	for (i = STARTOFTIME; day >= days_in_year(i); i++)
		day -= days_in_year(i);
	tm->tm_year = i;

	/* Number of months in days left */
	if (leapyear(tm->tm_year))
		days_in_month(FEBRUARY) = 29;
	for (i = 1; day >= days_in_month(i); i++)
		day -= days_in_month(i);
	days_in_month(FEBRUARY) = 28;
	tm->tm_mon = i;

	/* Days are what is left over (+1) from all that. */
	tm->tm_mday = day + 1;

	/*
	 * Determine the day of week
	 */
	GregorianDay(tm);
}

#if 0
/* Auxiliary function to compute scaling factors */
/* Actually the choice of a timebase running at 1/4 the of the bus
 * frequency giving resolution of a few tens of nanoseconds is quite nice.
 * It makes this computation very precise (27-28 bits typically) which
 * is optimistic considering the stability of most processor clock
 * oscillators and the precision with which the timebase frequency
 * is measured but does not harm.
 */
unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
        unsigned mlt=0, tmp, err;
        /* No concern for performance, it's done once: use a stupid
         * but safe and compact method to find the multiplier.
         */

        for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
                if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
        }

        /* We might still be off by 1 for the best approximation.
         * A side effect of this is that if outscale is too large
         * the returned value will be zero.
         * Many corner cases have been checked and seem to work,
         * some might have been forgotten in the test however.
         */

        err = inscale*(mlt+1);
        if (err <= inscale/2) mlt++;
        return mlt;
  }
#endif

/*
 * Divide a 128-bit dividend by a 32-bit divisor, leaving a 128 bit
 * result.
 */

void div128_by_32( unsigned long dividend_high, unsigned long dividend_low,
		   unsigned divisor, struct div_result *dr )
{
	unsigned long a,b,c,d, w,x,y,z, ra,rb,rc;

	a = dividend_high >> 32;
	b = dividend_high & 0xffffffff;
	c = dividend_low >> 32;
	d = dividend_low & 0xffffffff;

	w = a/divisor;
	ra = (a - (w * divisor)) << 32;

	x = (ra + b)/divisor;
	rb = ((ra + b) - (x * divisor)) << 32;

	y = (rb + c)/divisor;
	rc = ((rb + b) - (y * divisor)) << 32;

	z = (rc + d)/divisor;

	dr->result_high = (w << 32) + x;
	dr->result_low  = (y << 32) + z;

}