3 * Common time routines among all ppc machines.
5 * Written by Cort Dougan (cort@cs.nmt.edu) to merge
6 * Paul Mackerras' version and mine for PReP and Pmac.
7 * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
8 * Converted for 64-bit by Mike Corrigan (mikejc@us.ibm.com)
10 * First round of bugfixes by Gabriel Paubert (paubert@iram.es)
11 * to make clock more stable (2.4.0-test5). The only thing
12 * that this code assumes is that the timebases have been synchronized
13 * by firmware on SMP and are never stopped (never do sleep
14 * on SMP then, nap and doze are OK).
16 * Speeded up do_gettimeofday by getting rid of references to
17 * xtime (which required locks for consistency). (mikejc@us.ibm.com)
19 * TODO (not necessarily in this file):
20 * - improve precision and reproducibility of timebase frequency
21 * measurement at boot time. (for iSeries, we calibrate the timebase
22 * against the Titan chip's clock.)
23 * - for astronomical applications: add a new function to get
24 * non ambiguous timestamps even around leap seconds. This needs
25 * a new timestamp format and a good name.
27 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
28 * "A Kernel Model for Precision Timekeeping" by Dave Mills
30 * This program is free software; you can redistribute it and/or
31 * modify it under the terms of the GNU General Public License
32 * as published by the Free Software Foundation; either version
33 * 2 of the License, or (at your option) any later version.
36 #include <linux/config.h>
37 #include <linux/errno.h>
38 #include <linux/module.h>
39 #include <linux/sched.h>
40 #include <linux/kernel.h>
41 #include <linux/param.h>
42 #include <linux/string.h>
44 #include <linux/interrupt.h>
45 #include <linux/timex.h>
46 #include <linux/kernel_stat.h>
47 #include <linux/mc146818rtc.h>
48 #include <linux/time.h>
49 #include <linux/init.h>
50 #include <linux/profile.h>
52 #include <asm/segment.h>
54 #include <asm/processor.h>
55 #include <asm/nvram.h>
56 #include <asm/cache.h>
57 #include <asm/machdep.h>
58 #ifdef CONFIG_PPC_ISERIES
59 #include <asm/iSeries/ItLpQueue.h>
60 #include <asm/iSeries/HvCallXm.h>
62 #include <asm/uaccess.h>
64 #include <asm/ppcdebug.h>
66 #include <asm/sections.h>
68 void smp_local_timer_interrupt(struct pt_regs *);
70 u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
72 EXPORT_SYMBOL(jiffies_64);
74 /* keep track of when we need to update the rtc */
75 time_t last_rtc_update;
76 extern int piranha_simulator;
77 #ifdef CONFIG_PPC_ISERIES
78 unsigned long iSeries_recal_titan = 0;
79 unsigned long iSeries_recal_tb = 0;
80 static unsigned long first_settimeofday = 1;
83 #define XSEC_PER_SEC (1024*1024)
85 unsigned long tb_ticks_per_jiffy;
86 unsigned long tb_ticks_per_usec;
87 unsigned long tb_ticks_per_sec;
88 unsigned long next_xtime_sync_tb;
89 unsigned long xtime_sync_interval;
90 unsigned long tb_to_xs;
92 unsigned long processor_freq;
93 spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
95 unsigned long tb_to_ns_scale;
96 unsigned long tb_to_ns_shift;
98 struct gettimeofday_struct do_gtod;
100 extern unsigned long wall_jiffies;
101 extern unsigned long lpevent_count;
102 extern int smp_tb_synchronized;
104 void ppc_adjtimex(void);
106 static unsigned adjusting_time = 0;
109 * The profiling function is SMP safe. (nothing can mess
110 * around with "current", and the profiling counters are
111 * updated with atomic operations). This is especially
112 * useful with a profiling multiplier != 1
114 static inline void ppc64_do_profile(struct pt_regs *regs)
117 extern unsigned long prof_cpu_mask;
127 nip = instruction_pointer(regs);
130 * Only measure the CPUs specified by /proc/irq/prof_cpu_mask.
131 * (default is all CPUs.)
133 if (!((1<<smp_processor_id()) & prof_cpu_mask))
136 nip -= (unsigned long)_stext;
139 * Don't ignore out-of-bounds EIP values silently,
140 * put them into the last histogram slot, so if
141 * present, they will show up as a sharp peak.
143 if (nip > prof_len-1)
145 atomic_inc((atomic_t *)&prof_buffer[nip]);
148 static __inline__ void timer_check_rtc(void)
151 * update the rtc when needed, this should be performed on the
152 * right fraction of a second. Half or full second ?
153 * Full second works on mk48t59 clocks, others need testing.
154 * Note that this update is basically only used through
155 * the adjtimex system calls. Setting the HW clock in
156 * any other way is a /dev/rtc and userland business.
157 * This is still wrong by -0.5/+1.5 jiffies because of the
158 * timer interrupt resolution and possible delay, but here we
159 * hit a quantization limit which can only be solved by higher
160 * resolution timers and decoupling time management from timer
161 * interrupts. This is also wrong on the clocks
162 * which require being written at the half second boundary.
163 * We should have an rtc call that only sets the minutes and
164 * seconds like on Intel to avoid problems with non UTC clocks.
166 if ( (time_status & STA_UNSYNC) == 0 &&
167 xtime.tv_sec - last_rtc_update >= 659 &&
168 abs((xtime.tv_nsec/1000) - (1000000-1000000/HZ)) < 500000/HZ &&
169 jiffies - wall_jiffies == 1) {
171 to_tm(xtime.tv_sec+1, &tm);
174 if (ppc_md.set_rtc_time(&tm) == 0)
175 last_rtc_update = xtime.tv_sec+1;
177 /* Try again one minute later */
178 last_rtc_update += 60;
182 /* Synchronize xtime with do_gettimeofday */
184 static __inline__ void timer_sync_xtime( unsigned long cur_tb )
186 struct timeval my_tv;
188 if ( cur_tb > next_xtime_sync_tb ) {
189 next_xtime_sync_tb = cur_tb + xtime_sync_interval;
190 do_gettimeofday( &my_tv );
191 if ( xtime.tv_sec <= my_tv.tv_sec ) {
192 xtime.tv_sec = my_tv.tv_sec;
193 xtime.tv_nsec = my_tv.tv_usec * 1000;
198 #ifdef CONFIG_PPC_ISERIES
201 * This function recalibrates the timebase based on the 49-bit time-of-day
202 * value in the Titan chip. The Titan is much more accurate than the value
203 * returned by the service processor for the timebase frequency.
206 static void iSeries_tb_recal(void)
208 struct div_result divres;
209 unsigned long titan, tb;
211 titan = HvCallXm_loadTod();
212 if ( iSeries_recal_titan ) {
213 unsigned long tb_ticks = tb - iSeries_recal_tb;
214 unsigned long titan_usec = (titan - iSeries_recal_titan) >> 12;
215 unsigned long new_tb_ticks_per_sec = (tb_ticks * USEC_PER_SEC)/titan_usec;
216 unsigned long new_tb_ticks_per_jiffy = (new_tb_ticks_per_sec+(HZ/2))/HZ;
217 long tick_diff = new_tb_ticks_per_jiffy - tb_ticks_per_jiffy;
219 /* make sure tb_ticks_per_sec and tb_ticks_per_jiffy are consistent */
220 new_tb_ticks_per_sec = new_tb_ticks_per_jiffy * HZ;
222 if ( tick_diff < 0 ) {
223 tick_diff = -tick_diff;
227 if ( tick_diff < tb_ticks_per_jiffy/25 ) {
228 printk( "Titan recalibrate: new tb_ticks_per_jiffy = %lu (%c%ld)\n",
229 new_tb_ticks_per_jiffy, sign, tick_diff );
230 tb_ticks_per_jiffy = new_tb_ticks_per_jiffy;
231 tb_ticks_per_sec = new_tb_ticks_per_sec;
232 div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres );
233 do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
234 tb_to_xs = divres.result_low;
235 do_gtod.varp->tb_to_xs = tb_to_xs;
238 printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
239 " new tb_ticks_per_jiffy = %lu\n"
240 " old tb_ticks_per_jiffy = %lu\n",
241 new_tb_ticks_per_jiffy, tb_ticks_per_jiffy );
245 iSeries_recal_titan = titan;
246 iSeries_recal_tb = tb;
251 * For iSeries shared processors, we have to let the hypervisor
252 * set the hardware decrementer. We set a virtual decrementer
253 * in the ItLpPaca and call the hypervisor if the virtual
254 * decrementer is less than the current value in the hardware
255 * decrementer. (almost always the new decrementer value will
256 * be greater than the current hardware decementer so the hypervisor
257 * call will not be needed)
260 unsigned long tb_last_stamp __cacheline_aligned_in_smp;
263 * timer_interrupt - gets called when the decrementer overflows,
264 * with interrupts disabled.
266 int timer_interrupt(struct pt_regs * regs)
269 unsigned long cur_tb;
270 struct paca_struct *lpaca = get_paca();
271 unsigned long cpu = smp_processor_id();
275 #ifndef CONFIG_PPC_ISERIES
276 ppc64_do_profile(regs);
279 lpaca->lppaca.xIntDword.xFields.xDecrInt = 0;
281 while (lpaca->next_jiffy_update_tb <= (cur_tb = get_tb())) {
284 smp_local_timer_interrupt(regs);
286 if (cpu == boot_cpuid) {
287 write_seqlock(&xtime_lock);
288 tb_last_stamp = lpaca->next_jiffy_update_tb;
290 timer_sync_xtime( cur_tb );
292 write_sequnlock(&xtime_lock);
293 if ( adjusting_time && (time_adjust == 0) )
296 lpaca->next_jiffy_update_tb += tb_ticks_per_jiffy;
299 next_dec = lpaca->next_jiffy_update_tb - cur_tb;
300 if (next_dec > lpaca->default_decr)
301 next_dec = lpaca->default_decr;
304 #ifdef CONFIG_PPC_ISERIES
306 struct ItLpQueue *lpq = lpaca->lpqueue_ptr;
307 if (lpq && ItLpQueue_isLpIntPending(lpq))
308 lpevent_count += ItLpQueue_process(lpq, regs);
318 * Scheduler clock - returns current time in nanosec units.
320 * Note: mulhdu(a, b) (multiply high double unsigned) returns
321 * the high 64 bits of a * b, i.e. (a * b) >> 64, where a and b
322 * are 64-bit unsigned numbers.
324 unsigned long long sched_clock(void)
326 return mulhdu(get_tb(), tb_to_ns_scale) << tb_to_ns_shift;
330 * This version of gettimeofday has microsecond resolution.
332 void do_gettimeofday(struct timeval *tv)
334 unsigned long sec, usec, tb_ticks;
335 unsigned long xsec, tb_xsec;
336 struct gettimeofday_vars * temp_varp;
337 unsigned long temp_tb_to_xs, temp_stamp_xsec;
339 /* These calculations are faster (gets rid of divides)
340 * if done in units of 1/2^20 rather than microseconds.
341 * The conversion to microseconds at the end is done
342 * without a divide (and in fact, without a multiply) */
343 tb_ticks = get_tb() - do_gtod.tb_orig_stamp;
344 temp_varp = do_gtod.varp;
345 temp_tb_to_xs = temp_varp->tb_to_xs;
346 temp_stamp_xsec = temp_varp->stamp_xsec;
347 tb_xsec = mulhdu( tb_ticks, temp_tb_to_xs );
348 xsec = temp_stamp_xsec + tb_xsec;
349 sec = xsec / XSEC_PER_SEC;
350 xsec -= sec * XSEC_PER_SEC;
351 usec = (xsec * USEC_PER_SEC)/XSEC_PER_SEC;
357 EXPORT_SYMBOL(do_gettimeofday);
359 int do_settimeofday(struct timespec *tv)
361 time_t wtm_sec, new_sec = tv->tv_sec;
362 long wtm_nsec, new_nsec = tv->tv_nsec;
364 unsigned long delta_xsec;
366 unsigned long new_xsec;
368 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
371 write_seqlock_irqsave(&xtime_lock, flags);
372 /* Updating the RTC is not the job of this code. If the time is
373 * stepped under NTP, the RTC will be update after STA_UNSYNC
374 * is cleared. Tool like clock/hwclock either copy the RTC
375 * to the system time, in which case there is no point in writing
376 * to the RTC again, or write to the RTC but then they don't call
377 * settimeofday to perform this operation.
379 #ifdef CONFIG_PPC_ISERIES
380 if ( first_settimeofday ) {
382 first_settimeofday = 0;
385 tb_delta = tb_ticks_since(tb_last_stamp);
386 tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;
388 new_nsec -= tb_delta / tb_ticks_per_usec / 1000;
390 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec);
391 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec);
393 set_normalized_timespec(&xtime, new_sec, new_nsec);
394 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
396 /* In case of a large backwards jump in time with NTP, we want the
397 * clock to be updated as soon as the PLL is again in lock.
399 last_rtc_update = new_sec - 658;
401 time_adjust = 0; /* stop active adjtime() */
402 time_status |= STA_UNSYNC;
403 time_maxerror = NTP_PHASE_LIMIT;
404 time_esterror = NTP_PHASE_LIMIT;
406 delta_xsec = mulhdu( (tb_last_stamp-do_gtod.tb_orig_stamp), do_gtod.varp->tb_to_xs );
407 new_xsec = (new_nsec * XSEC_PER_SEC) / NSEC_PER_SEC;
408 new_xsec += new_sec * XSEC_PER_SEC;
409 if ( new_xsec > delta_xsec ) {
410 do_gtod.varp->stamp_xsec = new_xsec - delta_xsec;
413 /* This is only for the case where the user is setting the time
414 * way back to a time such that the boot time would have been
415 * before 1970 ... eg. we booted ten days ago, and we are setting
416 * the time to Jan 5, 1970 */
417 do_gtod.varp->stamp_xsec = new_xsec;
418 do_gtod.tb_orig_stamp = tb_last_stamp;
421 write_sequnlock_irqrestore(&xtime_lock, flags);
426 EXPORT_SYMBOL(do_settimeofday);
429 * This function is a copy of the architecture independent function
430 * but which calls do_settimeofday rather than setting the xtime
431 * fields itself. This way, the fields which are used for
432 * do_settimeofday get updated too.
434 long ppc64_sys32_stime(int __user * tptr)
437 struct timespec myTimeval;
439 if (!capable(CAP_SYS_TIME))
442 if (get_user(value, tptr))
445 myTimeval.tv_sec = value;
446 myTimeval.tv_nsec = 0;
448 do_settimeofday(&myTimeval);
454 * This function is a copy of the architecture independent function
455 * but which calls do_settimeofday rather than setting the xtime
456 * fields itself. This way, the fields which are used for
457 * do_settimeofday get updated too.
459 long ppc64_sys_stime(long __user * tptr)
462 struct timespec myTimeval;
464 if (!capable(CAP_SYS_TIME))
467 if (get_user(value, tptr))
470 myTimeval.tv_sec = value;
471 myTimeval.tv_nsec = 0;
473 do_settimeofday(&myTimeval);
478 void __init time_init(void)
480 /* This function is only called on the boot processor */
483 struct div_result res;
484 unsigned long scale, shift;
486 ppc_md.calibrate_decr();
489 * Compute scale factor for sched_clock.
490 * The calibrate_decr() function has set tb_ticks_per_sec,
491 * which is the timebase frequency.
492 * We compute 1e9 * 2^64 / tb_ticks_per_sec and interpret
493 * the 128-bit result as a 64.64 fixed-point number.
494 * We then shift that number right until it is less than 1.0,
495 * giving us the scale factor and shift count to use in
498 div128_by_32(1000000000, 0, tb_ticks_per_sec, &res);
499 scale = res.result_low;
500 for (shift = 0; res.result_high != 0; ++shift) {
501 scale = (scale >> 1) | (res.result_high << 63);
502 res.result_high >>= 1;
504 tb_to_ns_scale = scale;
505 tb_to_ns_shift = shift;
507 #ifdef CONFIG_PPC_ISERIES
508 if (!piranha_simulator)
510 ppc_md.get_boot_time(&tm);
512 write_seqlock_irqsave(&xtime_lock, flags);
513 xtime.tv_sec = mktime(tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
514 tm.tm_hour, tm.tm_min, tm.tm_sec);
515 tb_last_stamp = get_tb();
516 do_gtod.tb_orig_stamp = tb_last_stamp;
517 do_gtod.varp = &do_gtod.vars[0];
519 do_gtod.varp->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC;
520 do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
521 do_gtod.varp->tb_to_xs = tb_to_xs;
522 do_gtod.tb_to_us = tb_to_us;
524 xtime_sync_interval = tb_ticks_per_sec - (tb_ticks_per_sec/8);
525 next_xtime_sync_tb = tb_last_stamp + xtime_sync_interval;
530 last_rtc_update = xtime.tv_sec;
531 set_normalized_timespec(&wall_to_monotonic,
532 -xtime.tv_sec, -xtime.tv_nsec);
533 write_sequnlock_irqrestore(&xtime_lock, flags);
535 /* Not exact, but the timer interrupt takes care of this */
536 set_dec(tb_ticks_per_jiffy);
540 * After adjtimex is called, adjust the conversion of tb ticks
541 * to microseconds to keep do_gettimeofday synchronized
544 * Use the time_adjust, time_freq and time_offset computed by adjtimex to
545 * adjust the frequency.
548 /* #define DEBUG_PPC_ADJTIMEX 1 */
550 void ppc_adjtimex(void)
552 unsigned long den, new_tb_ticks_per_sec, tb_ticks, old_xsec, new_tb_to_xs, new_xsec, new_stamp_xsec;
553 unsigned long tb_ticks_per_sec_delta;
554 long delta_freq, ltemp;
555 struct div_result divres;
557 struct gettimeofday_vars * temp_varp;
559 long singleshot_ppm = 0;
561 /* Compute parts per million frequency adjustment to accomplish the time adjustment
562 implied by time_offset to be applied over the elapsed time indicated by time_constant.
563 Use SHIFT_USEC to get it into the same units as time_freq. */
564 if ( time_offset < 0 ) {
565 ltemp = -time_offset;
566 ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
567 ltemp >>= SHIFT_KG + time_constant;
572 ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
573 ltemp >>= SHIFT_KG + time_constant;
576 /* If there is a single shot time adjustment in progress */
578 #ifdef DEBUG_PPC_ADJTIMEX
579 printk("ppc_adjtimex: ");
580 if ( adjusting_time == 0 )
582 printk("single shot time_adjust = %ld\n", time_adjust);
587 /* Compute parts per million frequency adjustment to match time_adjust */
588 singleshot_ppm = tickadj * HZ;
590 * The adjustment should be tickadj*HZ to match the code in
591 * linux/kernel/timer.c, but experiments show that this is too
592 * large. 3/4 of tickadj*HZ seems about right
594 singleshot_ppm -= singleshot_ppm / 4;
595 /* Use SHIFT_USEC to get it into the same units as time_freq */
596 singleshot_ppm <<= SHIFT_USEC;
597 if ( time_adjust < 0 )
598 singleshot_ppm = -singleshot_ppm;
601 #ifdef DEBUG_PPC_ADJTIMEX
602 if ( adjusting_time )
603 printk("ppc_adjtimex: ending single shot time_adjust\n");
608 /* Add up all of the frequency adjustments */
609 delta_freq = time_freq + ltemp + singleshot_ppm;
611 /* Compute a new value for tb_ticks_per_sec based on the frequency adjustment */
612 den = 1000000 * (1 << (SHIFT_USEC - 8));
613 if ( delta_freq < 0 ) {
614 tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( (-delta_freq) >> (SHIFT_USEC - 8))) / den;
615 new_tb_ticks_per_sec = tb_ticks_per_sec + tb_ticks_per_sec_delta;
618 tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( delta_freq >> (SHIFT_USEC - 8))) / den;
619 new_tb_ticks_per_sec = tb_ticks_per_sec - tb_ticks_per_sec_delta;
622 #ifdef DEBUG_PPC_ADJTIMEX
623 printk("ppc_adjtimex: ltemp = %ld, time_freq = %ld, singleshot_ppm = %ld\n", ltemp, time_freq, singleshot_ppm);
624 printk("ppc_adjtimex: tb_ticks_per_sec - base = %ld new = %ld\n", tb_ticks_per_sec, new_tb_ticks_per_sec);
627 /* Compute a new value of tb_to_xs (used to convert tb to microseconds and a new value of
628 stamp_xsec which is the time (in 1/2^20 second units) corresponding to tb_orig_stamp. This
629 new value of stamp_xsec compensates for the change in frequency (implied by the new tb_to_xs)
630 which guarantees that the current time remains the same */
631 tb_ticks = get_tb() - do_gtod.tb_orig_stamp;
632 div128_by_32( 1024*1024, 0, new_tb_ticks_per_sec, &divres );
633 new_tb_to_xs = divres.result_low;
634 new_xsec = mulhdu( tb_ticks, new_tb_to_xs );
636 write_seqlock_irqsave( &xtime_lock, flags );
637 old_xsec = mulhdu( tb_ticks, do_gtod.varp->tb_to_xs );
638 new_stamp_xsec = do_gtod.varp->stamp_xsec + old_xsec - new_xsec;
640 /* There are two copies of tb_to_xs and stamp_xsec so that no lock is needed to access and use these
641 values in do_gettimeofday. We alternate the copies and as long as a reasonable time elapses between
642 changes, there will never be inconsistent values. ntpd has a minimum of one minute between updates */
644 if (do_gtod.var_idx == 0) {
645 temp_varp = &do_gtod.vars[1];
649 temp_varp = &do_gtod.vars[0];
652 temp_varp->tb_to_xs = new_tb_to_xs;
653 temp_varp->stamp_xsec = new_stamp_xsec;
655 do_gtod.varp = temp_varp;
656 do_gtod.var_idx = temp_idx;
658 write_sequnlock_irqrestore( &xtime_lock, flags );
663 #define TICK_SIZE tick
665 #define STARTOFTIME 1970
666 #define SECDAY 86400L
667 #define SECYR (SECDAY * 365)
668 #define leapyear(year) ((year) % 4 == 0)
669 #define days_in_year(a) (leapyear(a) ? 366 : 365)
670 #define days_in_month(a) (month_days[(a) - 1])
672 static int month_days[12] = {
673 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
677 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
679 void GregorianDay(struct rtc_time * tm)
684 int MonthOffset[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
686 lastYear=tm->tm_year-1;
689 * Number of leap corrections to apply up to end of last year
691 leapsToDate = lastYear/4 - lastYear/100 + lastYear/400;
694 * This year is a leap year if it is divisible by 4 except when it is
695 * divisible by 100 unless it is divisible by 400
697 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be
699 if((tm->tm_year%4==0) &&
700 ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) &&
704 * We are past Feb. 29 in a leap year
713 day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] +
719 void to_tm(int tim, struct rtc_time * tm)
722 register long hms, day;
727 /* Hours, minutes, seconds are easy */
728 tm->tm_hour = hms / 3600;
729 tm->tm_min = (hms % 3600) / 60;
730 tm->tm_sec = (hms % 3600) % 60;
732 /* Number of years in days */
733 for (i = STARTOFTIME; day >= days_in_year(i); i++)
734 day -= days_in_year(i);
737 /* Number of months in days left */
738 if (leapyear(tm->tm_year))
739 days_in_month(FEBRUARY) = 29;
740 for (i = 1; day >= days_in_month(i); i++)
741 day -= days_in_month(i);
742 days_in_month(FEBRUARY) = 28;
745 /* Days are what is left over (+1) from all that. */
746 tm->tm_mday = day + 1;
749 * Determine the day of week
754 /* Auxiliary function to compute scaling factors */
755 /* Actually the choice of a timebase running at 1/4 the of the bus
756 * frequency giving resolution of a few tens of nanoseconds is quite nice.
757 * It makes this computation very precise (27-28 bits typically) which
758 * is optimistic considering the stability of most processor clock
759 * oscillators and the precision with which the timebase frequency
760 * is measured but does not harm.
762 unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
763 unsigned mlt=0, tmp, err;
764 /* No concern for performance, it's done once: use a stupid
765 * but safe and compact method to find the multiplier.
768 for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
769 if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
772 /* We might still be off by 1 for the best approximation.
773 * A side effect of this is that if outscale is too large
774 * the returned value will be zero.
775 * Many corner cases have been checked and seem to work,
776 * some might have been forgotten in the test however.
779 err = inscale*(mlt+1);
780 if (err <= inscale/2) mlt++;
785 * Divide a 128-bit dividend by a 32-bit divisor, leaving a 128 bit
789 void div128_by_32( unsigned long dividend_high, unsigned long dividend_low,
790 unsigned divisor, struct div_result *dr )
792 unsigned long a,b,c,d, w,x,y,z, ra,rb,rc;
794 a = dividend_high >> 32;
795 b = dividend_high & 0xffffffff;
796 c = dividend_low >> 32;
797 d = dividend_low & 0xffffffff;
800 ra = (a - (w * divisor)) << 32;
802 x = (ra + b)/divisor;
803 rb = ((ra + b) - (x * divisor)) << 32;
805 y = (rb + c)/divisor;
806 rc = ((rb + b) - (y * divisor)) << 32;
808 z = (rc + d)/divisor;
810 dr->result_high = (w << 32) + x;
811 dr->result_low = (y << 32) + z;