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>
69 #include <asm/systemcfg.h>
71 u64 jiffies_64 __cacheline_aligned_in_smp
= INITIAL_JIFFIES
;
73 EXPORT_SYMBOL(jiffies_64
);
75 /* keep track of when we need to update the rtc */
76 time_t last_rtc_update
;
77 extern int piranha_simulator
;
78 #ifdef CONFIG_PPC_ISERIES
79 unsigned long iSeries_recal_titan
= 0;
80 unsigned long iSeries_recal_tb
= 0;
81 static unsigned long first_settimeofday
= 1;
84 #define XSEC_PER_SEC (1024*1024)
86 unsigned long tb_ticks_per_jiffy
;
87 unsigned long tb_ticks_per_usec
= 100; /* sane default */
88 EXPORT_SYMBOL(tb_ticks_per_usec
);
89 unsigned long tb_ticks_per_sec
;
90 unsigned long tb_to_xs
;
92 unsigned long processor_freq
;
93 DEFINE_SPINLOCK(rtc_lock
);
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 extern struct timezone sys_tz
;
106 void ppc_adjtimex(void);
108 static unsigned adjusting_time
= 0;
110 static __inline__
void timer_check_rtc(void)
113 * update the rtc when needed, this should be performed on the
114 * right fraction of a second. Half or full second ?
115 * Full second works on mk48t59 clocks, others need testing.
116 * Note that this update is basically only used through
117 * the adjtimex system calls. Setting the HW clock in
118 * any other way is a /dev/rtc and userland business.
119 * This is still wrong by -0.5/+1.5 jiffies because of the
120 * timer interrupt resolution and possible delay, but here we
121 * hit a quantization limit which can only be solved by higher
122 * resolution timers and decoupling time management from timer
123 * interrupts. This is also wrong on the clocks
124 * which require being written at the half second boundary.
125 * We should have an rtc call that only sets the minutes and
126 * seconds like on Intel to avoid problems with non UTC clocks.
128 if ( (time_status
& STA_UNSYNC
) == 0 &&
129 xtime
.tv_sec
- last_rtc_update
>= 659 &&
130 abs((xtime
.tv_nsec
/1000) - (1000000-1000000/HZ
)) < 500000/HZ
&&
131 jiffies
- wall_jiffies
== 1) {
133 to_tm(xtime
.tv_sec
+1, &tm
);
136 if (ppc_md
.set_rtc_time(&tm
) == 0)
137 last_rtc_update
= xtime
.tv_sec
+1;
139 /* Try again one minute later */
140 last_rtc_update
+= 60;
145 * This version of gettimeofday has microsecond resolution.
147 static inline void __do_gettimeofday(struct timeval
*tv
, unsigned long tb_val
)
149 unsigned long sec
, usec
, tb_ticks
;
150 unsigned long xsec
, tb_xsec
;
151 struct gettimeofday_vars
* temp_varp
;
152 unsigned long temp_tb_to_xs
, temp_stamp_xsec
;
155 * These calculations are faster (gets rid of divides)
156 * if done in units of 1/2^20 rather than microseconds.
157 * The conversion to microseconds at the end is done
158 * without a divide (and in fact, without a multiply)
160 temp_varp
= do_gtod
.varp
;
161 tb_ticks
= tb_val
- temp_varp
->tb_orig_stamp
;
162 temp_tb_to_xs
= temp_varp
->tb_to_xs
;
163 temp_stamp_xsec
= temp_varp
->stamp_xsec
;
164 tb_xsec
= mulhdu( tb_ticks
, temp_tb_to_xs
);
165 xsec
= temp_stamp_xsec
+ tb_xsec
;
166 sec
= xsec
/ XSEC_PER_SEC
;
167 xsec
-= sec
* XSEC_PER_SEC
;
168 usec
= (xsec
* USEC_PER_SEC
)/XSEC_PER_SEC
;
174 void do_gettimeofday(struct timeval
*tv
)
176 __do_gettimeofday(tv
, get_tb());
179 EXPORT_SYMBOL(do_gettimeofday
);
181 /* Synchronize xtime with do_gettimeofday */
183 static inline void timer_sync_xtime(unsigned long cur_tb
)
185 struct timeval my_tv
;
187 __do_gettimeofday(&my_tv
, cur_tb
);
189 if (xtime
.tv_sec
<= my_tv
.tv_sec
) {
190 xtime
.tv_sec
= my_tv
.tv_sec
;
191 xtime
.tv_nsec
= my_tv
.tv_usec
* 1000;
196 * When the timebase - tb_orig_stamp gets too big, we do a manipulation
197 * between tb_orig_stamp and stamp_xsec. The goal here is to keep the
198 * difference tb - tb_orig_stamp small enough to always fit inside a
199 * 32 bits number. This is a requirement of our fast 32 bits userland
200 * implementation in the vdso. If we "miss" a call to this function
201 * (interrupt latency, CPU locked in a spinlock, ...) and we end up
202 * with a too big difference, then the vdso will fallback to calling
205 static __inline__
void timer_recalc_offset(unsigned long cur_tb
)
207 struct gettimeofday_vars
* temp_varp
;
209 unsigned long offset
, new_stamp_xsec
, new_tb_orig_stamp
;
211 if (((cur_tb
- do_gtod
.varp
->tb_orig_stamp
) & 0x80000000u
) == 0)
214 temp_idx
= (do_gtod
.var_idx
== 0);
215 temp_varp
= &do_gtod
.vars
[temp_idx
];
217 new_tb_orig_stamp
= cur_tb
;
218 offset
= new_tb_orig_stamp
- do_gtod
.varp
->tb_orig_stamp
;
219 new_stamp_xsec
= do_gtod
.varp
->stamp_xsec
+ mulhdu(offset
, do_gtod
.varp
->tb_to_xs
);
221 temp_varp
->tb_to_xs
= do_gtod
.varp
->tb_to_xs
;
222 temp_varp
->tb_orig_stamp
= new_tb_orig_stamp
;
223 temp_varp
->stamp_xsec
= new_stamp_xsec
;
225 do_gtod
.varp
= temp_varp
;
226 do_gtod
.var_idx
= temp_idx
;
228 ++(systemcfg
->tb_update_count
);
230 systemcfg
->tb_orig_stamp
= new_tb_orig_stamp
;
231 systemcfg
->stamp_xsec
= new_stamp_xsec
;
233 ++(systemcfg
->tb_update_count
);
237 unsigned long profile_pc(struct pt_regs
*regs
)
239 unsigned long pc
= instruction_pointer(regs
);
241 if (in_lock_functions(pc
))
246 EXPORT_SYMBOL(profile_pc
);
249 #ifdef CONFIG_PPC_ISERIES
252 * This function recalibrates the timebase based on the 49-bit time-of-day
253 * value in the Titan chip. The Titan is much more accurate than the value
254 * returned by the service processor for the timebase frequency.
257 static void iSeries_tb_recal(void)
259 struct div_result divres
;
260 unsigned long titan
, tb
;
262 titan
= HvCallXm_loadTod();
263 if ( iSeries_recal_titan
) {
264 unsigned long tb_ticks
= tb
- iSeries_recal_tb
;
265 unsigned long titan_usec
= (titan
- iSeries_recal_titan
) >> 12;
266 unsigned long new_tb_ticks_per_sec
= (tb_ticks
* USEC_PER_SEC
)/titan_usec
;
267 unsigned long new_tb_ticks_per_jiffy
= (new_tb_ticks_per_sec
+(HZ
/2))/HZ
;
268 long tick_diff
= new_tb_ticks_per_jiffy
- tb_ticks_per_jiffy
;
270 /* make sure tb_ticks_per_sec and tb_ticks_per_jiffy are consistent */
271 new_tb_ticks_per_sec
= new_tb_ticks_per_jiffy
* HZ
;
273 if ( tick_diff
< 0 ) {
274 tick_diff
= -tick_diff
;
278 if ( tick_diff
< tb_ticks_per_jiffy
/25 ) {
279 printk( "Titan recalibrate: new tb_ticks_per_jiffy = %lu (%c%ld)\n",
280 new_tb_ticks_per_jiffy
, sign
, tick_diff
);
281 tb_ticks_per_jiffy
= new_tb_ticks_per_jiffy
;
282 tb_ticks_per_sec
= new_tb_ticks_per_sec
;
283 div128_by_32( XSEC_PER_SEC
, 0, tb_ticks_per_sec
, &divres
);
284 do_gtod
.tb_ticks_per_sec
= tb_ticks_per_sec
;
285 tb_to_xs
= divres
.result_low
;
286 do_gtod
.varp
->tb_to_xs
= tb_to_xs
;
287 systemcfg
->tb_ticks_per_sec
= tb_ticks_per_sec
;
288 systemcfg
->tb_to_xs
= tb_to_xs
;
291 printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
292 " new tb_ticks_per_jiffy = %lu\n"
293 " old tb_ticks_per_jiffy = %lu\n",
294 new_tb_ticks_per_jiffy
, tb_ticks_per_jiffy
);
298 iSeries_recal_titan
= titan
;
299 iSeries_recal_tb
= tb
;
304 * For iSeries shared processors, we have to let the hypervisor
305 * set the hardware decrementer. We set a virtual decrementer
306 * in the lppaca and call the hypervisor if the virtual
307 * decrementer is less than the current value in the hardware
308 * decrementer. (almost always the new decrementer value will
309 * be greater than the current hardware decementer so the hypervisor
310 * call will not be needed)
313 unsigned long tb_last_stamp __cacheline_aligned_in_smp
;
316 * timer_interrupt - gets called when the decrementer overflows,
317 * with interrupts disabled.
319 int timer_interrupt(struct pt_regs
* regs
)
322 unsigned long cur_tb
;
323 struct paca_struct
*lpaca
= get_paca();
324 unsigned long cpu
= smp_processor_id();
328 profile_tick(CPU_PROFILING
, regs
);
330 lpaca
->lppaca
.int_dword
.fields
.decr_int
= 0;
332 while (lpaca
->next_jiffy_update_tb
<= (cur_tb
= get_tb())) {
334 * We cannot disable the decrementer, so in the period
335 * between this cpu's being marked offline in cpu_online_map
336 * and calling stop-self, it is taking timer interrupts.
337 * Avoid calling into the scheduler rebalancing code if this
340 if (!cpu_is_offline(cpu
))
341 update_process_times(user_mode(regs
));
343 * No need to check whether cpu is offline here; boot_cpuid
344 * should have been fixed up by now.
346 if (cpu
== boot_cpuid
) {
347 write_seqlock(&xtime_lock
);
348 tb_last_stamp
= lpaca
->next_jiffy_update_tb
;
349 timer_recalc_offset(lpaca
->next_jiffy_update_tb
);
351 timer_sync_xtime(lpaca
->next_jiffy_update_tb
);
353 write_sequnlock(&xtime_lock
);
354 if ( adjusting_time
&& (time_adjust
== 0) )
357 lpaca
->next_jiffy_update_tb
+= tb_ticks_per_jiffy
;
360 next_dec
= lpaca
->next_jiffy_update_tb
- cur_tb
;
361 if (next_dec
> lpaca
->default_decr
)
362 next_dec
= lpaca
->default_decr
;
365 #ifdef CONFIG_PPC_ISERIES
367 struct ItLpQueue
*lpq
= lpaca
->lpqueue_ptr
;
368 if (lpq
&& ItLpQueue_isLpIntPending(lpq
))
369 lpevent_count
+= ItLpQueue_process(lpq
, regs
);
373 /* collect purr register values often, for accurate calculations */
374 #if defined(CONFIG_PPC_PSERIES)
375 if (cur_cpu_spec
->firmware_features
& FW_FEATURE_SPLPAR
) {
376 struct cpu_usage
*cu
= &__get_cpu_var(cpu_usage_array
);
377 cu
->current_tb
= mfspr(SPRN_PURR
);
387 * Scheduler clock - returns current time in nanosec units.
389 * Note: mulhdu(a, b) (multiply high double unsigned) returns
390 * the high 64 bits of a * b, i.e. (a * b) >> 64, where a and b
391 * are 64-bit unsigned numbers.
393 unsigned long long sched_clock(void)
395 return mulhdu(get_tb(), tb_to_ns_scale
) << tb_to_ns_shift
;
398 int do_settimeofday(struct timespec
*tv
)
400 time_t wtm_sec
, new_sec
= tv
->tv_sec
;
401 long wtm_nsec
, new_nsec
= tv
->tv_nsec
;
403 unsigned long delta_xsec
;
405 unsigned long new_xsec
;
407 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
410 write_seqlock_irqsave(&xtime_lock
, flags
);
411 /* Updating the RTC is not the job of this code. If the time is
412 * stepped under NTP, the RTC will be update after STA_UNSYNC
413 * is cleared. Tool like clock/hwclock either copy the RTC
414 * to the system time, in which case there is no point in writing
415 * to the RTC again, or write to the RTC but then they don't call
416 * settimeofday to perform this operation.
418 #ifdef CONFIG_PPC_ISERIES
419 if ( first_settimeofday
) {
421 first_settimeofday
= 0;
424 tb_delta
= tb_ticks_since(tb_last_stamp
);
425 tb_delta
+= (jiffies
- wall_jiffies
) * tb_ticks_per_jiffy
;
427 new_nsec
-= tb_delta
/ tb_ticks_per_usec
/ 1000;
429 wtm_sec
= wall_to_monotonic
.tv_sec
+ (xtime
.tv_sec
- new_sec
);
430 wtm_nsec
= wall_to_monotonic
.tv_nsec
+ (xtime
.tv_nsec
- new_nsec
);
432 set_normalized_timespec(&xtime
, new_sec
, new_nsec
);
433 set_normalized_timespec(&wall_to_monotonic
, wtm_sec
, wtm_nsec
);
435 /* In case of a large backwards jump in time with NTP, we want the
436 * clock to be updated as soon as the PLL is again in lock.
438 last_rtc_update
= new_sec
- 658;
440 time_adjust
= 0; /* stop active adjtime() */
441 time_status
|= STA_UNSYNC
;
442 time_maxerror
= NTP_PHASE_LIMIT
;
443 time_esterror
= NTP_PHASE_LIMIT
;
445 delta_xsec
= mulhdu( (tb_last_stamp
-do_gtod
.varp
->tb_orig_stamp
),
446 do_gtod
.varp
->tb_to_xs
);
448 new_xsec
= (new_nsec
* XSEC_PER_SEC
) / NSEC_PER_SEC
;
449 new_xsec
+= new_sec
* XSEC_PER_SEC
;
450 if ( new_xsec
> delta_xsec
) {
451 do_gtod
.varp
->stamp_xsec
= new_xsec
- delta_xsec
;
452 systemcfg
->stamp_xsec
= new_xsec
- delta_xsec
;
455 /* This is only for the case where the user is setting the time
456 * way back to a time such that the boot time would have been
457 * before 1970 ... eg. we booted ten days ago, and we are setting
458 * the time to Jan 5, 1970 */
459 do_gtod
.varp
->stamp_xsec
= new_xsec
;
460 do_gtod
.varp
->tb_orig_stamp
= tb_last_stamp
;
461 systemcfg
->stamp_xsec
= new_xsec
;
462 systemcfg
->tb_orig_stamp
= tb_last_stamp
;
465 systemcfg
->tz_minuteswest
= sys_tz
.tz_minuteswest
;
466 systemcfg
->tz_dsttime
= sys_tz
.tz_dsttime
;
468 write_sequnlock_irqrestore(&xtime_lock
, flags
);
473 EXPORT_SYMBOL(do_settimeofday
);
475 void __init
time_init(void)
477 /* This function is only called on the boot processor */
480 struct div_result res
;
481 unsigned long scale
, shift
;
483 ppc_md
.calibrate_decr();
486 * Compute scale factor for sched_clock.
487 * The calibrate_decr() function has set tb_ticks_per_sec,
488 * which is the timebase frequency.
489 * We compute 1e9 * 2^64 / tb_ticks_per_sec and interpret
490 * the 128-bit result as a 64.64 fixed-point number.
491 * We then shift that number right until it is less than 1.0,
492 * giving us the scale factor and shift count to use in
495 div128_by_32(1000000000, 0, tb_ticks_per_sec
, &res
);
496 scale
= res
.result_low
;
497 for (shift
= 0; res
.result_high
!= 0; ++shift
) {
498 scale
= (scale
>> 1) | (res
.result_high
<< 63);
499 res
.result_high
>>= 1;
501 tb_to_ns_scale
= scale
;
502 tb_to_ns_shift
= shift
;
504 #ifdef CONFIG_PPC_ISERIES
505 if (!piranha_simulator
)
507 ppc_md
.get_boot_time(&tm
);
509 write_seqlock_irqsave(&xtime_lock
, flags
);
510 xtime
.tv_sec
= mktime(tm
.tm_year
+ 1900, tm
.tm_mon
+ 1, tm
.tm_mday
,
511 tm
.tm_hour
, tm
.tm_min
, tm
.tm_sec
);
512 tb_last_stamp
= get_tb();
513 do_gtod
.varp
= &do_gtod
.vars
[0];
515 do_gtod
.varp
->tb_orig_stamp
= tb_last_stamp
;
516 get_paca()->next_jiffy_update_tb
= tb_last_stamp
+ tb_ticks_per_jiffy
;
517 do_gtod
.varp
->stamp_xsec
= xtime
.tv_sec
* XSEC_PER_SEC
;
518 do_gtod
.tb_ticks_per_sec
= tb_ticks_per_sec
;
519 do_gtod
.varp
->tb_to_xs
= tb_to_xs
;
520 do_gtod
.tb_to_us
= tb_to_us
;
521 systemcfg
->tb_orig_stamp
= tb_last_stamp
;
522 systemcfg
->tb_update_count
= 0;
523 systemcfg
->tb_ticks_per_sec
= tb_ticks_per_sec
;
524 systemcfg
->stamp_xsec
= xtime
.tv_sec
* XSEC_PER_SEC
;
525 systemcfg
->tb_to_xs
= tb_to_xs
;
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 write_seqlock_irqsave( &xtime_lock
, flags
);
632 tb_ticks
= get_tb() - do_gtod
.varp
->tb_orig_stamp
;
633 div128_by_32( 1024*1024, 0, new_tb_ticks_per_sec
, &divres
);
634 new_tb_to_xs
= divres
.result_low
;
635 new_xsec
= mulhdu( tb_ticks
, new_tb_to_xs
);
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 temp_idx
= (do_gtod
.var_idx
== 0);
645 temp_varp
= &do_gtod
.vars
[temp_idx
];
647 temp_varp
->tb_to_xs
= new_tb_to_xs
;
648 temp_varp
->stamp_xsec
= new_stamp_xsec
;
649 temp_varp
->tb_orig_stamp
= do_gtod
.varp
->tb_orig_stamp
;
651 do_gtod
.varp
= temp_varp
;
652 do_gtod
.var_idx
= temp_idx
;
655 * tb_update_count is used to allow the problem state gettimeofday code
656 * to assure itself that it sees a consistent view of the tb_to_xs and
657 * stamp_xsec variables. It reads the tb_update_count, then reads
658 * tb_to_xs and stamp_xsec and then reads tb_update_count again. If
659 * the two values of tb_update_count match and are even then the
660 * tb_to_xs and stamp_xsec values are consistent. If not, then it
661 * loops back and reads them again until this criteria is met.
663 ++(systemcfg
->tb_update_count
);
665 systemcfg
->tb_to_xs
= new_tb_to_xs
;
666 systemcfg
->stamp_xsec
= new_stamp_xsec
;
668 ++(systemcfg
->tb_update_count
);
670 write_sequnlock_irqrestore( &xtime_lock
, flags
);
675 #define TICK_SIZE tick
677 #define STARTOFTIME 1970
678 #define SECDAY 86400L
679 #define SECYR (SECDAY * 365)
680 #define leapyear(year) ((year) % 4 == 0)
681 #define days_in_year(a) (leapyear(a) ? 366 : 365)
682 #define days_in_month(a) (month_days[(a) - 1])
684 static int month_days
[12] = {
685 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
689 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
691 void GregorianDay(struct rtc_time
* tm
)
696 int MonthOffset
[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
698 lastYear
=tm
->tm_year
-1;
701 * Number of leap corrections to apply up to end of last year
703 leapsToDate
= lastYear
/4 - lastYear
/100 + lastYear
/400;
706 * This year is a leap year if it is divisible by 4 except when it is
707 * divisible by 100 unless it is divisible by 400
709 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be
711 if((tm
->tm_year
%4==0) &&
712 ((tm
->tm_year
%100!=0) || (tm
->tm_year
%400==0)) &&
716 * We are past Feb. 29 in a leap year
725 day
+= lastYear
*365 + leapsToDate
+ MonthOffset
[tm
->tm_mon
-1] +
731 void to_tm(int tim
, struct rtc_time
* tm
)
734 register long hms
, day
;
739 /* Hours, minutes, seconds are easy */
740 tm
->tm_hour
= hms
/ 3600;
741 tm
->tm_min
= (hms
% 3600) / 60;
742 tm
->tm_sec
= (hms
% 3600) % 60;
744 /* Number of years in days */
745 for (i
= STARTOFTIME
; day
>= days_in_year(i
); i
++)
746 day
-= days_in_year(i
);
749 /* Number of months in days left */
750 if (leapyear(tm
->tm_year
))
751 days_in_month(FEBRUARY
) = 29;
752 for (i
= 1; day
>= days_in_month(i
); i
++)
753 day
-= days_in_month(i
);
754 days_in_month(FEBRUARY
) = 28;
757 /* Days are what is left over (+1) from all that. */
758 tm
->tm_mday
= day
+ 1;
761 * Determine the day of week
766 /* Auxiliary function to compute scaling factors */
767 /* Actually the choice of a timebase running at 1/4 the of the bus
768 * frequency giving resolution of a few tens of nanoseconds is quite nice.
769 * It makes this computation very precise (27-28 bits typically) which
770 * is optimistic considering the stability of most processor clock
771 * oscillators and the precision with which the timebase frequency
772 * is measured but does not harm.
774 unsigned mulhwu_scale_factor(unsigned inscale
, unsigned outscale
) {
775 unsigned mlt
=0, tmp
, err
;
776 /* No concern for performance, it's done once: use a stupid
777 * but safe and compact method to find the multiplier.
780 for (tmp
= 1U<<31; tmp
!= 0; tmp
>>= 1) {
781 if (mulhwu(inscale
, mlt
|tmp
) < outscale
) mlt
|=tmp
;
784 /* We might still be off by 1 for the best approximation.
785 * A side effect of this is that if outscale is too large
786 * the returned value will be zero.
787 * Many corner cases have been checked and seem to work,
788 * some might have been forgotten in the test however.
791 err
= inscale
*(mlt
+1);
792 if (err
<= inscale
/2) mlt
++;
797 * Divide a 128-bit dividend by a 32-bit divisor, leaving a 128 bit
801 void div128_by_32( unsigned long dividend_high
, unsigned long dividend_low
,
802 unsigned divisor
, struct div_result
*dr
)
804 unsigned long a
,b
,c
,d
, w
,x
,y
,z
, ra
,rb
,rc
;
806 a
= dividend_high
>> 32;
807 b
= dividend_high
& 0xffffffff;
808 c
= dividend_low
>> 32;
809 d
= dividend_low
& 0xffffffff;
812 ra
= (a
- (w
* divisor
)) << 32;
814 x
= (ra
+ b
)/divisor
;
815 rb
= ((ra
+ b
) - (x
* divisor
)) << 32;
817 y
= (rb
+ c
)/divisor
;
818 rc
= ((rb
+ b
) - (y
* divisor
)) << 32;
820 z
= (rc
+ d
)/divisor
;
822 dr
->result_high
= (w
<< 32) + x
;
823 dr
->result_low
= (y
<< 32) + z
;