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/HvCallXm.h>
61 #include <asm/uaccess.h>
63 #include <asm/ppcdebug.h>
65 #include <asm/sections.h>
67 void smp_local_timer_interrupt(struct pt_regs *);
69 u64 jiffies_64 = INITIAL_JIFFIES;
71 EXPORT_SYMBOL(jiffies_64);
73 /* keep track of when we need to update the rtc */
74 time_t last_rtc_update;
75 extern int piranha_simulator;
76 #ifdef CONFIG_PPC_ISERIES
77 unsigned long iSeries_recal_titan = 0;
78 unsigned long iSeries_recal_tb = 0;
79 static unsigned long first_settimeofday = 1;
82 #define XSEC_PER_SEC (1024*1024)
84 unsigned long tb_ticks_per_jiffy;
85 unsigned long tb_ticks_per_usec;
86 unsigned long tb_ticks_per_sec;
87 unsigned long next_xtime_sync_tb;
88 unsigned long xtime_sync_interval;
89 unsigned long tb_to_xs;
91 unsigned long processor_freq;
92 spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
94 unsigned long tb_to_ns_scale;
95 unsigned long tb_to_ns_shift;
97 struct gettimeofday_struct do_gtod;
99 extern unsigned long wall_jiffies;
100 extern unsigned long lpEvent_count;
101 extern int smp_tb_synchronized;
103 void ppc_adjtimex(void);
105 static unsigned adjusting_time = 0;
108 * The profiling function is SMP safe. (nothing can mess
109 * around with "current", and the profiling counters are
110 * updated with atomic operations). This is especially
111 * useful with a profiling multiplier != 1
113 static inline void ppc64_do_profile(struct pt_regs *regs)
116 extern unsigned long prof_cpu_mask;
126 nip = instruction_pointer(regs);
129 * Only measure the CPUs specified by /proc/irq/prof_cpu_mask.
130 * (default is all CPUs.)
132 if (!((1<<smp_processor_id()) & prof_cpu_mask))
135 nip -= (unsigned long)_stext;
138 * Don't ignore out-of-bounds EIP values silently,
139 * put them into the last histogram slot, so if
140 * present, they will show up as a sharp peak.
142 if (nip > prof_len-1)
144 atomic_inc((atomic_t *)&prof_buffer[nip]);
147 static __inline__ void timer_check_rtc(void)
150 * update the rtc when needed, this should be performed on the
151 * right fraction of a second. Half or full second ?
152 * Full second works on mk48t59 clocks, others need testing.
153 * Note that this update is basically only used through
154 * the adjtimex system calls. Setting the HW clock in
155 * any other way is a /dev/rtc and userland business.
156 * This is still wrong by -0.5/+1.5 jiffies because of the
157 * timer interrupt resolution and possible delay, but here we
158 * hit a quantization limit which can only be solved by higher
159 * resolution timers and decoupling time management from timer
160 * interrupts. This is also wrong on the clocks
161 * which require being written at the half second boundary.
162 * We should have an rtc call that only sets the minutes and
163 * seconds like on Intel to avoid problems with non UTC clocks.
165 if ( (time_status & STA_UNSYNC) == 0 &&
166 xtime.tv_sec - last_rtc_update >= 659 &&
167 abs((xtime.tv_nsec/1000) - (1000000-1000000/HZ)) < 500000/HZ &&
168 jiffies - wall_jiffies == 1) {
170 to_tm(xtime.tv_sec+1, &tm);
173 if (ppc_md.set_rtc_time(&tm) == 0)
174 last_rtc_update = xtime.tv_sec+1;
176 /* Try again one minute later */
177 last_rtc_update += 60;
181 /* Synchronize xtime with do_gettimeofday */
183 static __inline__ void timer_sync_xtime( unsigned long cur_tb )
185 struct timeval my_tv;
187 if ( cur_tb > next_xtime_sync_tb ) {
188 next_xtime_sync_tb = cur_tb + xtime_sync_interval;
189 do_gettimeofday( &my_tv );
190 if ( xtime.tv_sec <= my_tv.tv_sec ) {
191 xtime.tv_sec = my_tv.tv_sec;
192 xtime.tv_nsec = my_tv.tv_usec * 1000;
197 #ifdef CONFIG_PPC_ISERIES
200 * This function recalibrates the timebase based on the 49-bit time-of-day
201 * value in the Titan chip. The Titan is much more accurate than the value
202 * returned by the service processor for the timebase frequency.
205 static void iSeries_tb_recal(void)
207 struct div_result divres;
208 unsigned long titan, tb;
210 titan = HvCallXm_loadTod();
211 if ( iSeries_recal_titan ) {
212 unsigned long tb_ticks = tb - iSeries_recal_tb;
213 unsigned long titan_usec = (titan - iSeries_recal_titan) >> 12;
214 unsigned long new_tb_ticks_per_sec = (tb_ticks * USEC_PER_SEC)/titan_usec;
215 unsigned long new_tb_ticks_per_jiffy = (new_tb_ticks_per_sec+(HZ/2))/HZ;
216 long tick_diff = new_tb_ticks_per_jiffy - tb_ticks_per_jiffy;
218 /* make sure tb_ticks_per_sec and tb_ticks_per_jiffy are consistent */
219 new_tb_ticks_per_sec = new_tb_ticks_per_jiffy * HZ;
221 if ( tick_diff < 0 ) {
222 tick_diff = -tick_diff;
226 if ( tick_diff < tb_ticks_per_jiffy/25 ) {
227 printk( "Titan recalibrate: new tb_ticks_per_jiffy = %lu (%c%ld)\n",
228 new_tb_ticks_per_jiffy, sign, tick_diff );
229 tb_ticks_per_jiffy = new_tb_ticks_per_jiffy;
230 tb_ticks_per_sec = new_tb_ticks_per_sec;
231 div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres );
232 do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
233 tb_to_xs = divres.result_low;
234 do_gtod.varp->tb_to_xs = tb_to_xs;
237 printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
238 " new tb_ticks_per_jiffy = %lu\n"
239 " old tb_ticks_per_jiffy = %lu\n",
240 new_tb_ticks_per_jiffy, tb_ticks_per_jiffy );
244 iSeries_recal_titan = titan;
245 iSeries_recal_tb = tb;
250 * For iSeries shared processors, we have to let the hypervisor
251 * set the hardware decrementer. We set a virtual decrementer
252 * in the ItLpPaca and call the hypervisor if the virtual
253 * decrementer is less than the current value in the hardware
254 * decrementer. (almost always the new decrementer value will
255 * be greater than the current hardware decementer so the hypervisor
256 * call will not be needed)
259 unsigned long tb_last_stamp=0;
262 * timer_interrupt - gets called when the decrementer overflows,
263 * with interrupts disabled.
265 int timer_interrupt(struct pt_regs * regs)
268 unsigned long cur_tb;
269 struct paca_struct *lpaca = get_paca();
270 unsigned long cpu = smp_processor_id();
274 #ifndef CONFIG_PPC_ISERIES
275 ppc64_do_profile(regs);
278 lpaca->xLpPaca.xIntDword.xFields.xDecrInt = 0;
280 while (lpaca->next_jiffy_update_tb <= (cur_tb = get_tb())) {
283 smp_local_timer_interrupt(regs);
285 if (cpu == boot_cpuid) {
286 write_seqlock(&xtime_lock);
287 tb_last_stamp = lpaca->next_jiffy_update_tb;
289 timer_sync_xtime( cur_tb );
291 write_sequnlock(&xtime_lock);
292 if ( adjusting_time && (time_adjust == 0) )
295 lpaca->next_jiffy_update_tb += tb_ticks_per_jiffy;
298 next_dec = lpaca->next_jiffy_update_tb - cur_tb;
299 if (next_dec > lpaca->default_decr)
300 next_dec = lpaca->default_decr;
303 #ifdef CONFIG_PPC_ISERIES
305 struct ItLpQueue *lpq = lpaca->lpQueuePtr;
306 if (lpq && ItLpQueue_isLpIntPending(lpq))
307 lpEvent_count += ItLpQueue_process(lpq, regs);
317 * Scheduler clock - returns current time in nanosec units.
319 * Note: mulhdu(a, b) (multiply high double unsigned) returns
320 * the high 64 bits of a * b, i.e. (a * b) >> 64, where a and b
321 * are 64-bit unsigned numbers.
323 unsigned long long sched_clock(void)
325 return mulhdu(get_tb(), tb_to_ns_scale) << tb_to_ns_shift;
329 * This version of gettimeofday has microsecond resolution.
331 void do_gettimeofday(struct timeval *tv)
333 unsigned long sec, usec, tb_ticks;
334 unsigned long xsec, tb_xsec;
335 struct gettimeofday_vars * temp_varp;
336 unsigned long temp_tb_to_xs, temp_stamp_xsec;
338 /* These calculations are faster (gets rid of divides)
339 * if done in units of 1/2^20 rather than microseconds.
340 * The conversion to microseconds at the end is done
341 * without a divide (and in fact, without a multiply) */
342 tb_ticks = get_tb() - do_gtod.tb_orig_stamp;
343 temp_varp = do_gtod.varp;
344 temp_tb_to_xs = temp_varp->tb_to_xs;
345 temp_stamp_xsec = temp_varp->stamp_xsec;
346 tb_xsec = mulhdu( tb_ticks, temp_tb_to_xs );
347 xsec = temp_stamp_xsec + tb_xsec;
348 sec = xsec / XSEC_PER_SEC;
349 xsec -= sec * XSEC_PER_SEC;
350 usec = (xsec * USEC_PER_SEC)/XSEC_PER_SEC;
356 EXPORT_SYMBOL(do_gettimeofday);
358 int do_settimeofday(struct timespec *tv)
360 time_t wtm_sec, new_sec = tv->tv_sec;
361 long wtm_nsec, new_nsec = tv->tv_nsec;
363 unsigned long delta_xsec;
365 unsigned long new_xsec;
367 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
370 write_seqlock_irqsave(&xtime_lock, flags);
371 /* Updating the RTC is not the job of this code. If the time is
372 * stepped under NTP, the RTC will be update after STA_UNSYNC
373 * is cleared. Tool like clock/hwclock either copy the RTC
374 * to the system time, in which case there is no point in writing
375 * to the RTC again, or write to the RTC but then they don't call
376 * settimeofday to perform this operation.
378 #ifdef CONFIG_PPC_ISERIES
379 if ( first_settimeofday ) {
381 first_settimeofday = 0;
384 tb_delta = tb_ticks_since(tb_last_stamp);
385 tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;
387 new_nsec -= tb_delta / tb_ticks_per_usec / 1000;
389 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec);
390 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec);
392 set_normalized_timespec(&xtime, new_sec, new_nsec);
393 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
395 /* In case of a large backwards jump in time with NTP, we want the
396 * clock to be updated as soon as the PLL is again in lock.
398 last_rtc_update = new_sec - 658;
400 time_adjust = 0; /* stop active adjtime() */
401 time_status |= STA_UNSYNC;
402 time_maxerror = NTP_PHASE_LIMIT;
403 time_esterror = NTP_PHASE_LIMIT;
405 delta_xsec = mulhdu( (tb_last_stamp-do_gtod.tb_orig_stamp), do_gtod.varp->tb_to_xs );
406 new_xsec = (new_nsec * XSEC_PER_SEC) / NSEC_PER_SEC;
407 new_xsec += new_sec * XSEC_PER_SEC;
408 if ( new_xsec > delta_xsec ) {
409 do_gtod.varp->stamp_xsec = new_xsec - delta_xsec;
412 /* This is only for the case where the user is setting the time
413 * way back to a time such that the boot time would have been
414 * before 1970 ... eg. we booted ten days ago, and we are setting
415 * the time to Jan 5, 1970 */
416 do_gtod.varp->stamp_xsec = new_xsec;
417 do_gtod.tb_orig_stamp = tb_last_stamp;
420 write_sequnlock_irqrestore(&xtime_lock, flags);
425 EXPORT_SYMBOL(do_settimeofday);
428 * This function is a copy of the architecture independent function
429 * but which calls do_settimeofday rather than setting the xtime
430 * fields itself. This way, the fields which are used for
431 * do_settimeofday get updated too.
433 long ppc64_sys32_stime(int* tptr)
436 struct timespec myTimeval;
438 if (!capable(CAP_SYS_TIME))
441 if (get_user(value, tptr))
444 myTimeval.tv_sec = value;
445 myTimeval.tv_nsec = 0;
447 do_settimeofday(&myTimeval);
453 * This function is a copy of the architecture independent function
454 * but which calls do_settimeofday rather than setting the xtime
455 * fields itself. This way, the fields which are used for
456 * do_settimeofday get updated too.
458 long ppc64_sys_stime(long* tptr)
461 struct timespec myTimeval;
463 if (!capable(CAP_SYS_TIME))
466 if (get_user(value, tptr))
469 myTimeval.tv_sec = value;
470 myTimeval.tv_nsec = 0;
472 do_settimeofday(&myTimeval);
477 void __init time_init(void)
479 /* This function is only called on the boot processor */
482 struct div_result res;
483 unsigned long scale, shift;
485 ppc_md.calibrate_decr();
488 * Compute scale factor for sched_clock.
489 * The calibrate_decr() function has set tb_ticks_per_sec,
490 * which is the timebase frequency.
491 * We compute 1e9 * 2^64 / tb_ticks_per_sec and interpret
492 * the 128-bit result as a 64.64 fixed-point number.
493 * We then shift that number right until it is less than 1.0,
494 * giving us the scale factor and shift count to use in
497 div128_by_32(1000000000, 0, tb_ticks_per_sec, &res);
498 scale = res.result_low;
499 for (shift = 0; res.result_high != 0; ++shift) {
500 scale = (scale >> 1) | (res.result_high << 63);
501 res.result_high >>= 1;
503 tb_to_ns_scale = scale;
504 tb_to_ns_shift = shift;
506 #ifdef CONFIG_PPC_ISERIES
507 if (!piranha_simulator)
509 ppc_md.get_boot_time(&tm);
511 write_seqlock_irqsave(&xtime_lock, flags);
512 xtime.tv_sec = mktime(tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
513 tm.tm_hour, tm.tm_min, tm.tm_sec);
514 tb_last_stamp = get_tb();
515 do_gtod.tb_orig_stamp = tb_last_stamp;
516 do_gtod.varp = &do_gtod.vars[0];
518 do_gtod.varp->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC;
519 do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
520 do_gtod.varp->tb_to_xs = tb_to_xs;
521 do_gtod.tb_to_us = tb_to_us;
523 xtime_sync_interval = tb_ticks_per_sec - (tb_ticks_per_sec/8);
524 next_xtime_sync_tb = tb_last_stamp + xtime_sync_interval;
529 last_rtc_update = xtime.tv_sec;
530 set_normalized_timespec(&wall_to_monotonic,
531 -xtime.tv_sec, -xtime.tv_nsec);
532 write_sequnlock_irqrestore(&xtime_lock, flags);
534 /* Not exact, but the timer interrupt takes care of this */
535 set_dec(tb_ticks_per_jiffy);
539 * After adjtimex is called, adjust the conversion of tb ticks
540 * to microseconds to keep do_gettimeofday synchronized
543 * Use the time_adjust, time_freq and time_offset computed by adjtimex to
544 * adjust the frequency.
547 /* #define DEBUG_PPC_ADJTIMEX 1 */
549 void ppc_adjtimex(void)
551 unsigned long den, new_tb_ticks_per_sec, tb_ticks, old_xsec, new_tb_to_xs, new_xsec, new_stamp_xsec;
552 unsigned long tb_ticks_per_sec_delta;
553 long delta_freq, ltemp;
554 struct div_result divres;
556 struct gettimeofday_vars * temp_varp;
558 long singleshot_ppm = 0;
560 /* Compute parts per million frequency adjustment to accomplish the time adjustment
561 implied by time_offset to be applied over the elapsed time indicated by time_constant.
562 Use SHIFT_USEC to get it into the same units as time_freq. */
563 if ( time_offset < 0 ) {
564 ltemp = -time_offset;
565 ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
566 ltemp >>= SHIFT_KG + time_constant;
571 ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
572 ltemp >>= SHIFT_KG + time_constant;
575 /* If there is a single shot time adjustment in progress */
577 #ifdef DEBUG_PPC_ADJTIMEX
578 printk("ppc_adjtimex: ");
579 if ( adjusting_time == 0 )
581 printk("single shot time_adjust = %ld\n", time_adjust);
586 /* Compute parts per million frequency adjustment to match time_adjust */
587 singleshot_ppm = tickadj * HZ;
589 * The adjustment should be tickadj*HZ to match the code in
590 * linux/kernel/timer.c, but experiments show that this is too
591 * large. 3/4 of tickadj*HZ seems about right
593 singleshot_ppm -= singleshot_ppm / 4;
594 /* Use SHIFT_USEC to get it into the same units as time_freq */
595 singleshot_ppm <<= SHIFT_USEC;
596 if ( time_adjust < 0 )
597 singleshot_ppm = -singleshot_ppm;
600 #ifdef DEBUG_PPC_ADJTIMEX
601 if ( adjusting_time )
602 printk("ppc_adjtimex: ending single shot time_adjust\n");
607 /* Add up all of the frequency adjustments */
608 delta_freq = time_freq + ltemp + singleshot_ppm;
610 /* Compute a new value for tb_ticks_per_sec based on the frequency adjustment */
611 den = 1000000 * (1 << (SHIFT_USEC - 8));
612 if ( delta_freq < 0 ) {
613 tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( (-delta_freq) >> (SHIFT_USEC - 8))) / den;
614 new_tb_ticks_per_sec = tb_ticks_per_sec + tb_ticks_per_sec_delta;
617 tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( delta_freq >> (SHIFT_USEC - 8))) / den;
618 new_tb_ticks_per_sec = tb_ticks_per_sec - tb_ticks_per_sec_delta;
621 #ifdef DEBUG_PPC_ADJTIMEX
622 printk("ppc_adjtimex: ltemp = %ld, time_freq = %ld, singleshot_ppm = %ld\n", ltemp, time_freq, singleshot_ppm);
623 printk("ppc_adjtimex: tb_ticks_per_sec - base = %ld new = %ld\n", tb_ticks_per_sec, new_tb_ticks_per_sec);
626 /* Compute a new value of tb_to_xs (used to convert tb to microseconds and a new value of
627 stamp_xsec which is the time (in 1/2^20 second units) corresponding to tb_orig_stamp. This
628 new value of stamp_xsec compensates for the change in frequency (implied by the new tb_to_xs)
629 which guarantees that the current time remains the same */
630 tb_ticks = get_tb() - do_gtod.tb_orig_stamp;
631 div128_by_32( 1024*1024, 0, new_tb_ticks_per_sec, &divres );
632 new_tb_to_xs = divres.result_low;
633 new_xsec = mulhdu( tb_ticks, new_tb_to_xs );
635 write_seqlock_irqsave( &xtime_lock, flags );
636 old_xsec = mulhdu( tb_ticks, do_gtod.varp->tb_to_xs );
637 new_stamp_xsec = do_gtod.varp->stamp_xsec + old_xsec - new_xsec;
639 /* There are two copies of tb_to_xs and stamp_xsec so that no lock is needed to access and use these
640 values in do_gettimeofday. We alternate the copies and as long as a reasonable time elapses between
641 changes, there will never be inconsistent values. ntpd has a minimum of one minute between updates */
643 if (do_gtod.var_idx == 0) {
644 temp_varp = &do_gtod.vars[1];
648 temp_varp = &do_gtod.vars[0];
651 temp_varp->tb_to_xs = new_tb_to_xs;
652 temp_varp->stamp_xsec = new_stamp_xsec;
654 do_gtod.varp = temp_varp;
655 do_gtod.var_idx = temp_idx;
657 write_sequnlock_irqrestore( &xtime_lock, flags );
662 #define TICK_SIZE tick
664 #define STARTOFTIME 1970
665 #define SECDAY 86400L
666 #define SECYR (SECDAY * 365)
667 #define leapyear(year) ((year) % 4 == 0)
668 #define days_in_year(a) (leapyear(a) ? 366 : 365)
669 #define days_in_month(a) (month_days[(a) - 1])
671 static int month_days[12] = {
672 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
676 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
678 void GregorianDay(struct rtc_time * tm)
683 int MonthOffset[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
685 lastYear=tm->tm_year-1;
688 * Number of leap corrections to apply up to end of last year
690 leapsToDate = lastYear/4 - lastYear/100 + lastYear/400;
693 * This year is a leap year if it is divisible by 4 except when it is
694 * divisible by 100 unless it is divisible by 400
696 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be
698 if((tm->tm_year%4==0) &&
699 ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) &&
703 * We are past Feb. 29 in a leap year
712 day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] +
718 void to_tm(int tim, struct rtc_time * tm)
721 register long hms, day;
726 /* Hours, minutes, seconds are easy */
727 tm->tm_hour = hms / 3600;
728 tm->tm_min = (hms % 3600) / 60;
729 tm->tm_sec = (hms % 3600) % 60;
731 /* Number of years in days */
732 for (i = STARTOFTIME; day >= days_in_year(i); i++)
733 day -= days_in_year(i);
736 /* Number of months in days left */
737 if (leapyear(tm->tm_year))
738 days_in_month(FEBRUARY) = 29;
739 for (i = 1; day >= days_in_month(i); i++)
740 day -= days_in_month(i);
741 days_in_month(FEBRUARY) = 28;
744 /* Days are what is left over (+1) from all that. */
745 tm->tm_mday = day + 1;
748 * Determine the day of week
753 /* Auxiliary function to compute scaling factors */
754 /* Actually the choice of a timebase running at 1/4 the of the bus
755 * frequency giving resolution of a few tens of nanoseconds is quite nice.
756 * It makes this computation very precise (27-28 bits typically) which
757 * is optimistic considering the stability of most processor clock
758 * oscillators and the precision with which the timebase frequency
759 * is measured but does not harm.
761 unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
762 unsigned mlt=0, tmp, err;
763 /* No concern for performance, it's done once: use a stupid
764 * but safe and compact method to find the multiplier.
767 for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
768 if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
771 /* We might still be off by 1 for the best approximation.
772 * A side effect of this is that if outscale is too large
773 * the returned value will be zero.
774 * Many corner cases have been checked and seem to work,
775 * some might have been forgotten in the test however.
778 err = inscale*(mlt+1);
779 if (err <= inscale/2) mlt++;
784 * Divide a 128-bit dividend by a 32-bit divisor, leaving a 128 bit
788 void div128_by_32( unsigned long dividend_high, unsigned long dividend_low,
789 unsigned divisor, struct div_result *dr )
791 unsigned long a,b,c,d, w,x,y,z, ra,rb,rc;
793 a = dividend_high >> 32;
794 b = dividend_high & 0xffffffff;
795 c = dividend_low >> 32;
796 d = dividend_low & 0xffffffff;
799 ra = (a - (w * divisor)) << 32;
801 x = (ra + b)/divisor;
802 rb = ((ra + b) - (x * divisor)) << 32;
804 y = (rb + c)/divisor;
805 rc = ((rb + b) - (y * divisor)) << 32;
807 z = (rc + d)/divisor;
809 dr->result_high = (w << 32) + x;
810 dr->result_low = (y << 32) + z;