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>
51 #include <linux/cpu.h>
52 #include <linux/security.h>
54 #include <asm/segment.h>
56 #include <asm/processor.h>
57 #include <asm/nvram.h>
58 #include <asm/cache.h>
59 #include <asm/machdep.h>
60 #ifdef CONFIG_PPC_ISERIES
61 #include <asm/iSeries/ItLpQueue.h>
62 #include <asm/iSeries/HvCallXm.h>
64 #include <asm/uaccess.h>
66 #include <asm/ppcdebug.h>
68 #include <asm/sections.h>
70 void smp_local_timer_interrupt(struct pt_regs *);
72 u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
74 EXPORT_SYMBOL(jiffies_64);
76 /* keep track of when we need to update the rtc */
77 time_t last_rtc_update;
78 extern int piranha_simulator;
79 #ifdef CONFIG_PPC_ISERIES
80 unsigned long iSeries_recal_titan = 0;
81 unsigned long iSeries_recal_tb = 0;
82 static unsigned long first_settimeofday = 1;
85 #define XSEC_PER_SEC (1024*1024)
87 unsigned long tb_ticks_per_jiffy;
88 unsigned long tb_ticks_per_usec = 100; /* sane default */
89 unsigned long tb_ticks_per_sec;
90 unsigned long next_xtime_sync_tb;
91 unsigned long xtime_sync_interval;
92 unsigned long tb_to_xs;
94 unsigned long processor_freq;
95 spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
97 unsigned long tb_to_ns_scale;
98 unsigned long tb_to_ns_shift;
100 struct gettimeofday_struct do_gtod;
102 extern unsigned long wall_jiffies;
103 extern unsigned long lpevent_count;
104 extern int smp_tb_synchronized;
106 extern struct timezone sys_tz;
108 void ppc_adjtimex(void);
110 static unsigned adjusting_time = 0;
112 static __inline__ void timer_check_rtc(void)
115 * update the rtc when needed, this should be performed on the
116 * right fraction of a second. Half or full second ?
117 * Full second works on mk48t59 clocks, others need testing.
118 * Note that this update is basically only used through
119 * the adjtimex system calls. Setting the HW clock in
120 * any other way is a /dev/rtc and userland business.
121 * This is still wrong by -0.5/+1.5 jiffies because of the
122 * timer interrupt resolution and possible delay, but here we
123 * hit a quantization limit which can only be solved by higher
124 * resolution timers and decoupling time management from timer
125 * interrupts. This is also wrong on the clocks
126 * which require being written at the half second boundary.
127 * We should have an rtc call that only sets the minutes and
128 * seconds like on Intel to avoid problems with non UTC clocks.
130 if ( (time_status & STA_UNSYNC) == 0 &&
131 xtime.tv_sec - last_rtc_update >= 659 &&
132 abs((xtime.tv_nsec/1000) - (1000000-1000000/HZ)) < 500000/HZ &&
133 jiffies - wall_jiffies == 1) {
135 to_tm(xtime.tv_sec+1, &tm);
138 if (ppc_md.set_rtc_time(&tm) == 0)
139 last_rtc_update = xtime.tv_sec+1;
141 /* Try again one minute later */
142 last_rtc_update += 60;
146 /* Synchronize xtime with do_gettimeofday */
148 static __inline__ void timer_sync_xtime( unsigned long cur_tb )
150 struct timeval my_tv;
152 if ( cur_tb > next_xtime_sync_tb ) {
153 next_xtime_sync_tb = cur_tb + xtime_sync_interval;
154 do_gettimeofday( &my_tv );
155 if ( xtime.tv_sec <= my_tv.tv_sec ) {
156 xtime.tv_sec = my_tv.tv_sec;
157 xtime.tv_nsec = my_tv.tv_usec * 1000;
163 unsigned long profile_pc(struct pt_regs *regs)
165 unsigned long pc = instruction_pointer(regs);
167 if (in_lock_functions(pc))
172 EXPORT_SYMBOL(profile_pc);
175 #ifdef CONFIG_PPC_ISERIES
178 * This function recalibrates the timebase based on the 49-bit time-of-day
179 * value in the Titan chip. The Titan is much more accurate than the value
180 * returned by the service processor for the timebase frequency.
183 static void iSeries_tb_recal(void)
185 struct div_result divres;
186 unsigned long titan, tb;
188 titan = HvCallXm_loadTod();
189 if ( iSeries_recal_titan ) {
190 unsigned long tb_ticks = tb - iSeries_recal_tb;
191 unsigned long titan_usec = (titan - iSeries_recal_titan) >> 12;
192 unsigned long new_tb_ticks_per_sec = (tb_ticks * USEC_PER_SEC)/titan_usec;
193 unsigned long new_tb_ticks_per_jiffy = (new_tb_ticks_per_sec+(HZ/2))/HZ;
194 long tick_diff = new_tb_ticks_per_jiffy - tb_ticks_per_jiffy;
196 /* make sure tb_ticks_per_sec and tb_ticks_per_jiffy are consistent */
197 new_tb_ticks_per_sec = new_tb_ticks_per_jiffy * HZ;
199 if ( tick_diff < 0 ) {
200 tick_diff = -tick_diff;
204 if ( tick_diff < tb_ticks_per_jiffy/25 ) {
205 printk( "Titan recalibrate: new tb_ticks_per_jiffy = %lu (%c%ld)\n",
206 new_tb_ticks_per_jiffy, sign, tick_diff );
207 tb_ticks_per_jiffy = new_tb_ticks_per_jiffy;
208 tb_ticks_per_sec = new_tb_ticks_per_sec;
209 div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres );
210 do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
211 tb_to_xs = divres.result_low;
212 do_gtod.varp->tb_to_xs = tb_to_xs;
213 systemcfg->tb_ticks_per_sec = tb_ticks_per_sec;
214 systemcfg->tb_to_xs = tb_to_xs;
217 printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
218 " new tb_ticks_per_jiffy = %lu\n"
219 " old tb_ticks_per_jiffy = %lu\n",
220 new_tb_ticks_per_jiffy, tb_ticks_per_jiffy );
224 iSeries_recal_titan = titan;
225 iSeries_recal_tb = tb;
230 * For iSeries shared processors, we have to let the hypervisor
231 * set the hardware decrementer. We set a virtual decrementer
232 * in the ItLpPaca and call the hypervisor if the virtual
233 * decrementer is less than the current value in the hardware
234 * decrementer. (almost always the new decrementer value will
235 * be greater than the current hardware decementer so the hypervisor
236 * call will not be needed)
239 unsigned long tb_last_stamp __cacheline_aligned_in_smp;
242 * timer_interrupt - gets called when the decrementer overflows,
243 * with interrupts disabled.
245 int timer_interrupt(struct pt_regs * regs)
248 unsigned long cur_tb;
249 struct paca_struct *lpaca = get_paca();
250 unsigned long cpu = smp_processor_id();
254 #ifndef CONFIG_PPC_ISERIES
255 profile_tick(CPU_PROFILING, regs);
258 lpaca->lppaca.xIntDword.xFields.xDecrInt = 0;
260 while (lpaca->next_jiffy_update_tb <= (cur_tb = get_tb())) {
264 * We cannot disable the decrementer, so in the period
265 * between this cpu's being marked offline in cpu_online_map
266 * and calling stop-self, it is taking timer interrupts.
267 * Avoid calling into the scheduler rebalancing code if this
270 if (!cpu_is_offline(cpu))
271 smp_local_timer_interrupt(regs);
274 * No need to check whether cpu is offline here; boot_cpuid
275 * should have been fixed up by now.
277 if (cpu == boot_cpuid) {
278 write_seqlock(&xtime_lock);
279 tb_last_stamp = lpaca->next_jiffy_update_tb;
282 update_process_times(user_mode(regs));
284 timer_sync_xtime( cur_tb );
286 write_sequnlock(&xtime_lock);
287 if ( adjusting_time && (time_adjust == 0) )
290 lpaca->next_jiffy_update_tb += tb_ticks_per_jiffy;
293 next_dec = lpaca->next_jiffy_update_tb - cur_tb;
294 if (next_dec > lpaca->default_decr)
295 next_dec = lpaca->default_decr;
298 #ifdef CONFIG_PPC_ISERIES
300 struct ItLpQueue *lpq = lpaca->lpqueue_ptr;
301 if (lpq && ItLpQueue_isLpIntPending(lpq))
302 lpevent_count += ItLpQueue_process(lpq, regs);
312 * Scheduler clock - returns current time in nanosec units.
314 * Note: mulhdu(a, b) (multiply high double unsigned) returns
315 * the high 64 bits of a * b, i.e. (a * b) >> 64, where a and b
316 * are 64-bit unsigned numbers.
318 unsigned long long sched_clock(void)
320 return mulhdu(get_tb(), tb_to_ns_scale) << tb_to_ns_shift;
324 * This version of gettimeofday has microsecond resolution.
326 void do_gettimeofday(struct timeval *tv)
328 unsigned long sec, usec, tb_ticks;
329 unsigned long xsec, tb_xsec;
330 struct gettimeofday_vars * temp_varp;
331 unsigned long temp_tb_to_xs, temp_stamp_xsec;
333 /* These calculations are faster (gets rid of divides)
334 * if done in units of 1/2^20 rather than microseconds.
335 * The conversion to microseconds at the end is done
336 * without a divide (and in fact, without a multiply) */
337 tb_ticks = get_tb() - do_gtod.tb_orig_stamp;
338 temp_varp = do_gtod.varp;
339 temp_tb_to_xs = temp_varp->tb_to_xs;
340 temp_stamp_xsec = temp_varp->stamp_xsec;
341 tb_xsec = mulhdu( tb_ticks, temp_tb_to_xs );
342 xsec = temp_stamp_xsec + tb_xsec;
343 sec = xsec / XSEC_PER_SEC;
344 xsec -= sec * XSEC_PER_SEC;
345 usec = (xsec * USEC_PER_SEC)/XSEC_PER_SEC;
351 EXPORT_SYMBOL(do_gettimeofday);
353 int do_settimeofday(struct timespec *tv)
355 time_t wtm_sec, new_sec = tv->tv_sec;
356 long wtm_nsec, new_nsec = tv->tv_nsec;
358 unsigned long delta_xsec;
360 unsigned long new_xsec;
362 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
365 write_seqlock_irqsave(&xtime_lock, flags);
366 /* Updating the RTC is not the job of this code. If the time is
367 * stepped under NTP, the RTC will be update after STA_UNSYNC
368 * is cleared. Tool like clock/hwclock either copy the RTC
369 * to the system time, in which case there is no point in writing
370 * to the RTC again, or write to the RTC but then they don't call
371 * settimeofday to perform this operation.
373 #ifdef CONFIG_PPC_ISERIES
374 if ( first_settimeofday ) {
376 first_settimeofday = 0;
379 tb_delta = tb_ticks_since(tb_last_stamp);
380 tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;
382 new_nsec -= tb_delta / tb_ticks_per_usec / 1000;
384 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec);
385 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec);
387 set_normalized_timespec(&xtime, new_sec, new_nsec);
388 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
390 /* In case of a large backwards jump in time with NTP, we want the
391 * clock to be updated as soon as the PLL is again in lock.
393 last_rtc_update = new_sec - 658;
395 time_adjust = 0; /* stop active adjtime() */
396 time_status |= STA_UNSYNC;
397 time_maxerror = NTP_PHASE_LIMIT;
398 time_esterror = NTP_PHASE_LIMIT;
400 delta_xsec = mulhdu( (tb_last_stamp-do_gtod.tb_orig_stamp), do_gtod.varp->tb_to_xs );
401 new_xsec = (new_nsec * XSEC_PER_SEC) / NSEC_PER_SEC;
402 new_xsec += new_sec * XSEC_PER_SEC;
403 if ( new_xsec > delta_xsec ) {
404 do_gtod.varp->stamp_xsec = new_xsec - delta_xsec;
405 systemcfg->stamp_xsec = new_xsec - delta_xsec;
408 /* This is only for the case where the user is setting the time
409 * way back to a time such that the boot time would have been
410 * before 1970 ... eg. we booted ten days ago, and we are setting
411 * the time to Jan 5, 1970 */
412 do_gtod.varp->stamp_xsec = new_xsec;
413 do_gtod.tb_orig_stamp = tb_last_stamp;
414 systemcfg->stamp_xsec = new_xsec;
415 systemcfg->tb_orig_stamp = tb_last_stamp;
418 systemcfg->tz_minuteswest = sys_tz.tz_minuteswest;
419 systemcfg->tz_dsttime = sys_tz.tz_dsttime;
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;
440 if (get_user(value, tptr))
443 myTimeval.tv_sec = value;
444 myTimeval.tv_nsec = 0;
446 err = security_settime(&myTimeval, NULL);
450 do_settimeofday(&myTimeval);
456 * This function is a copy of the architecture independent function
457 * but which calls do_settimeofday rather than setting the xtime
458 * fields itself. This way, the fields which are used for
459 * do_settimeofday get updated too.
461 long ppc64_sys_stime(long __user * tptr)
464 struct timespec myTimeval;
467 if (get_user(value, tptr))
470 myTimeval.tv_sec = value;
471 myTimeval.tv_nsec = 0;
473 err = security_settime(&myTimeval, NULL);
477 do_settimeofday(&myTimeval);
482 void __init time_init(void)
484 /* This function is only called on the boot processor */
487 struct div_result res;
488 unsigned long scale, shift;
490 ppc_md.calibrate_decr();
493 * Compute scale factor for sched_clock.
494 * The calibrate_decr() function has set tb_ticks_per_sec,
495 * which is the timebase frequency.
496 * We compute 1e9 * 2^64 / tb_ticks_per_sec and interpret
497 * the 128-bit result as a 64.64 fixed-point number.
498 * We then shift that number right until it is less than 1.0,
499 * giving us the scale factor and shift count to use in
502 div128_by_32(1000000000, 0, tb_ticks_per_sec, &res);
503 scale = res.result_low;
504 for (shift = 0; res.result_high != 0; ++shift) {
505 scale = (scale >> 1) | (res.result_high << 63);
506 res.result_high >>= 1;
508 tb_to_ns_scale = scale;
509 tb_to_ns_shift = shift;
511 #ifdef CONFIG_PPC_ISERIES
512 if (!piranha_simulator)
514 ppc_md.get_boot_time(&tm);
516 write_seqlock_irqsave(&xtime_lock, flags);
517 xtime.tv_sec = mktime(tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
518 tm.tm_hour, tm.tm_min, tm.tm_sec);
519 tb_last_stamp = get_tb();
520 do_gtod.tb_orig_stamp = tb_last_stamp;
521 do_gtod.varp = &do_gtod.vars[0];
523 do_gtod.varp->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC;
524 do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
525 do_gtod.varp->tb_to_xs = tb_to_xs;
526 do_gtod.tb_to_us = tb_to_us;
527 systemcfg->tb_orig_stamp = tb_last_stamp;
528 systemcfg->tb_update_count = 0;
529 systemcfg->tb_ticks_per_sec = tb_ticks_per_sec;
530 systemcfg->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC;
531 systemcfg->tb_to_xs = tb_to_xs;
533 xtime_sync_interval = tb_ticks_per_sec - (tb_ticks_per_sec/8);
534 next_xtime_sync_tb = tb_last_stamp + xtime_sync_interval;
539 last_rtc_update = xtime.tv_sec;
540 set_normalized_timespec(&wall_to_monotonic,
541 -xtime.tv_sec, -xtime.tv_nsec);
542 write_sequnlock_irqrestore(&xtime_lock, flags);
544 /* Not exact, but the timer interrupt takes care of this */
545 set_dec(tb_ticks_per_jiffy);
549 * After adjtimex is called, adjust the conversion of tb ticks
550 * to microseconds to keep do_gettimeofday synchronized
553 * Use the time_adjust, time_freq and time_offset computed by adjtimex to
554 * adjust the frequency.
557 /* #define DEBUG_PPC_ADJTIMEX 1 */
559 void ppc_adjtimex(void)
561 unsigned long den, new_tb_ticks_per_sec, tb_ticks, old_xsec, new_tb_to_xs, new_xsec, new_stamp_xsec;
562 unsigned long tb_ticks_per_sec_delta;
563 long delta_freq, ltemp;
564 struct div_result divres;
566 struct gettimeofday_vars * temp_varp;
568 long singleshot_ppm = 0;
570 /* Compute parts per million frequency adjustment to accomplish the time adjustment
571 implied by time_offset to be applied over the elapsed time indicated by time_constant.
572 Use SHIFT_USEC to get it into the same units as time_freq. */
573 if ( time_offset < 0 ) {
574 ltemp = -time_offset;
575 ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
576 ltemp >>= SHIFT_KG + time_constant;
581 ltemp <<= SHIFT_USEC - SHIFT_UPDATE;
582 ltemp >>= SHIFT_KG + time_constant;
585 /* If there is a single shot time adjustment in progress */
587 #ifdef DEBUG_PPC_ADJTIMEX
588 printk("ppc_adjtimex: ");
589 if ( adjusting_time == 0 )
591 printk("single shot time_adjust = %ld\n", time_adjust);
596 /* Compute parts per million frequency adjustment to match time_adjust */
597 singleshot_ppm = tickadj * HZ;
599 * The adjustment should be tickadj*HZ to match the code in
600 * linux/kernel/timer.c, but experiments show that this is too
601 * large. 3/4 of tickadj*HZ seems about right
603 singleshot_ppm -= singleshot_ppm / 4;
604 /* Use SHIFT_USEC to get it into the same units as time_freq */
605 singleshot_ppm <<= SHIFT_USEC;
606 if ( time_adjust < 0 )
607 singleshot_ppm = -singleshot_ppm;
610 #ifdef DEBUG_PPC_ADJTIMEX
611 if ( adjusting_time )
612 printk("ppc_adjtimex: ending single shot time_adjust\n");
617 /* Add up all of the frequency adjustments */
618 delta_freq = time_freq + ltemp + singleshot_ppm;
620 /* Compute a new value for tb_ticks_per_sec based on the frequency adjustment */
621 den = 1000000 * (1 << (SHIFT_USEC - 8));
622 if ( delta_freq < 0 ) {
623 tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( (-delta_freq) >> (SHIFT_USEC - 8))) / den;
624 new_tb_ticks_per_sec = tb_ticks_per_sec + tb_ticks_per_sec_delta;
627 tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( delta_freq >> (SHIFT_USEC - 8))) / den;
628 new_tb_ticks_per_sec = tb_ticks_per_sec - tb_ticks_per_sec_delta;
631 #ifdef DEBUG_PPC_ADJTIMEX
632 printk("ppc_adjtimex: ltemp = %ld, time_freq = %ld, singleshot_ppm = %ld\n", ltemp, time_freq, singleshot_ppm);
633 printk("ppc_adjtimex: tb_ticks_per_sec - base = %ld new = %ld\n", tb_ticks_per_sec, new_tb_ticks_per_sec);
636 /* Compute a new value of tb_to_xs (used to convert tb to microseconds and a new value of
637 stamp_xsec which is the time (in 1/2^20 second units) corresponding to tb_orig_stamp. This
638 new value of stamp_xsec compensates for the change in frequency (implied by the new tb_to_xs)
639 which guarantees that the current time remains the same */
640 tb_ticks = get_tb() - do_gtod.tb_orig_stamp;
641 div128_by_32( 1024*1024, 0, new_tb_ticks_per_sec, &divres );
642 new_tb_to_xs = divres.result_low;
643 new_xsec = mulhdu( tb_ticks, new_tb_to_xs );
645 write_seqlock_irqsave( &xtime_lock, flags );
646 old_xsec = mulhdu( tb_ticks, do_gtod.varp->tb_to_xs );
647 new_stamp_xsec = do_gtod.varp->stamp_xsec + old_xsec - new_xsec;
649 /* There are two copies of tb_to_xs and stamp_xsec so that no lock is needed to access and use these
650 values in do_gettimeofday. We alternate the copies and as long as a reasonable time elapses between
651 changes, there will never be inconsistent values. ntpd has a minimum of one minute between updates */
653 if (do_gtod.var_idx == 0) {
654 temp_varp = &do_gtod.vars[1];
658 temp_varp = &do_gtod.vars[0];
661 temp_varp->tb_to_xs = new_tb_to_xs;
662 temp_varp->stamp_xsec = new_stamp_xsec;
664 do_gtod.varp = temp_varp;
665 do_gtod.var_idx = temp_idx;
668 * tb_update_count is used to allow the problem state gettimeofday code
669 * to assure itself that it sees a consistent view of the tb_to_xs and
670 * stamp_xsec variables. It reads the tb_update_count, then reads
671 * tb_to_xs and stamp_xsec and then reads tb_update_count again. If
672 * the two values of tb_update_count match and are even then the
673 * tb_to_xs and stamp_xsec values are consistent. If not, then it
674 * loops back and reads them again until this criteria is met.
676 ++(systemcfg->tb_update_count);
678 systemcfg->tb_to_xs = new_tb_to_xs;
679 systemcfg->stamp_xsec = new_stamp_xsec;
681 ++(systemcfg->tb_update_count);
683 write_sequnlock_irqrestore( &xtime_lock, flags );
688 #define TICK_SIZE tick
690 #define STARTOFTIME 1970
691 #define SECDAY 86400L
692 #define SECYR (SECDAY * 365)
693 #define leapyear(year) ((year) % 4 == 0)
694 #define days_in_year(a) (leapyear(a) ? 366 : 365)
695 #define days_in_month(a) (month_days[(a) - 1])
697 static int month_days[12] = {
698 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
702 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
704 void GregorianDay(struct rtc_time * tm)
709 int MonthOffset[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
711 lastYear=tm->tm_year-1;
714 * Number of leap corrections to apply up to end of last year
716 leapsToDate = lastYear/4 - lastYear/100 + lastYear/400;
719 * This year is a leap year if it is divisible by 4 except when it is
720 * divisible by 100 unless it is divisible by 400
722 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be
724 if((tm->tm_year%4==0) &&
725 ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) &&
729 * We are past Feb. 29 in a leap year
738 day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] +
744 void to_tm(int tim, struct rtc_time * tm)
747 register long hms, day;
752 /* Hours, minutes, seconds are easy */
753 tm->tm_hour = hms / 3600;
754 tm->tm_min = (hms % 3600) / 60;
755 tm->tm_sec = (hms % 3600) % 60;
757 /* Number of years in days */
758 for (i = STARTOFTIME; day >= days_in_year(i); i++)
759 day -= days_in_year(i);
762 /* Number of months in days left */
763 if (leapyear(tm->tm_year))
764 days_in_month(FEBRUARY) = 29;
765 for (i = 1; day >= days_in_month(i); i++)
766 day -= days_in_month(i);
767 days_in_month(FEBRUARY) = 28;
770 /* Days are what is left over (+1) from all that. */
771 tm->tm_mday = day + 1;
774 * Determine the day of week
779 /* Auxiliary function to compute scaling factors */
780 /* Actually the choice of a timebase running at 1/4 the of the bus
781 * frequency giving resolution of a few tens of nanoseconds is quite nice.
782 * It makes this computation very precise (27-28 bits typically) which
783 * is optimistic considering the stability of most processor clock
784 * oscillators and the precision with which the timebase frequency
785 * is measured but does not harm.
787 unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
788 unsigned mlt=0, tmp, err;
789 /* No concern for performance, it's done once: use a stupid
790 * but safe and compact method to find the multiplier.
793 for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
794 if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
797 /* We might still be off by 1 for the best approximation.
798 * A side effect of this is that if outscale is too large
799 * the returned value will be zero.
800 * Many corner cases have been checked and seem to work,
801 * some might have been forgotten in the test however.
804 err = inscale*(mlt+1);
805 if (err <= inscale/2) mlt++;
810 * Divide a 128-bit dividend by a 32-bit divisor, leaving a 128 bit
814 void div128_by_32( unsigned long dividend_high, unsigned long dividend_low,
815 unsigned divisor, struct div_result *dr )
817 unsigned long a,b,c,d, w,x,y,z, ra,rb,rc;
819 a = dividend_high >> 32;
820 b = dividend_high & 0xffffffff;
821 c = dividend_low >> 32;
822 d = dividend_low & 0xffffffff;
825 ra = (a - (w * divisor)) << 32;
827 x = (ra + b)/divisor;
828 rb = ((ra + b) - (x * divisor)) << 32;
830 y = (rb + c)/divisor;
831 rc = ((rb + b) - (y * divisor)) << 32;
833 z = (rc + d)/divisor;
835 dr->result_high = (w << 32) + x;
836 dr->result_low = (y << 32) + z;