2 * Common time routines among all ppc machines.
4 * Written by Cort Dougan (cort@cs.nmt.edu) to merge
5 * Paul Mackerras' version and mine for PReP and Pmac.
6 * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
8 * First round of bugfixes by Gabriel Paubert (paubert@iram.es)
9 * to make clock more stable (2.4.0-test5). The only thing
10 * that this code assumes is that the timebases have been synchronized
11 * by firmware on SMP and are never stopped (never do sleep
12 * on SMP then, nap and doze are OK).
14 * TODO (not necessarily in this file):
15 * - improve precision and reproducibility of timebase frequency
16 * measurement at boot time.
17 * - get rid of xtime_lock for gettimeofday (generic kernel problem
18 * to be implemented on all architectures for SMP scalability and
19 * eventually implementing gettimeofday without entering the kernel).
20 * - put all time/clock related variables in a single structure
21 * to minimize number of cache lines touched by gettimeofday()
22 * - for astronomical applications: add a new function to get
23 * non ambiguous timestamps even around leap seconds. This needs
24 * a new timestamp format and a good name.
27 * The following comment is partially obsolete (at least the long wait
28 * is no more a valid reason):
29 * Since the MPC8xx has a programmable interrupt timer, I decided to
30 * use that rather than the decrementer. Two reasons: 1.) the clock
31 * frequency is low, causing 2.) a long wait in the timer interrupt
32 * while ((d = get_dec()) == dval)
33 * loop. The MPC8xx can be driven from a variety of input clocks,
34 * so a number of assumptions have been made here because the kernel
35 * parameter HZ is a constant. We assume (correctly, today :-) that
36 * the MPC8xx on the MBX board is driven from a 32.768 kHz crystal.
37 * This is then divided by 4, providing a 8192 Hz clock into the PIT.
38 * Since it is not possible to get a nice 100 Hz clock out of this, without
39 * creating a software PLL, I have set HZ to 128. -- Dan
41 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
42 * "A Kernel Model for Precision Timekeeping" by Dave Mills
45 #include <linux/config.h>
46 #include <linux/errno.h>
47 #include <linux/sched.h>
48 #include <linux/kernel.h>
49 #include <linux/param.h>
50 #include <linux/string.h>
52 #include <linux/module.h>
53 #include <linux/interrupt.h>
54 #include <linux/timex.h>
55 #include <linux/kernel_stat.h>
56 #include <linux/mc146818rtc.h>
57 #include <linux/time.h>
58 #include <linux/init.h>
59 #include <linux/profile.h>
62 #include <asm/nvram.h>
63 #include <asm/cache.h>
64 #include <asm/8xx_immap.h>
65 #include <asm/machdep.h>
69 unsigned long disarm_decr
[NR_CPUS
];
71 extern struct timezone sys_tz
;
73 /* keep track of when we need to update the rtc */
74 time_t last_rtc_update
;
76 /* The decrementer counts down by 128 every 128ns on a 601. */
77 #define DECREMENTER_COUNT_601 (1000000000 / HZ)
79 unsigned tb_ticks_per_jiffy
;
81 unsigned tb_last_stamp
;
82 unsigned long tb_to_ns_scale
;
84 extern unsigned long wall_jiffies
;
86 /* used for timezone offset */
87 static long timezone_offset
;
89 DEFINE_SPINLOCK(rtc_lock
);
91 EXPORT_SYMBOL(rtc_lock
);
93 /* Timer interrupt helper function */
94 static inline int tb_delta(unsigned *jiffy_stamp
) {
98 if (delta
< *jiffy_stamp
) *jiffy_stamp
-= 1000000000;
99 delta
-= *jiffy_stamp
;
101 delta
= get_tbl() - *jiffy_stamp
;
107 unsigned long profile_pc(struct pt_regs
*regs
)
109 unsigned long pc
= instruction_pointer(regs
);
111 if (in_lock_functions(pc
))
116 EXPORT_SYMBOL(profile_pc
);
119 void wakeup_decrementer(void)
121 set_dec(tb_ticks_per_jiffy
);
122 /* No currently-supported powerbook has a 601,
123 * so use get_tbl, not native
125 last_jiffy_stamp(0) = tb_last_stamp
= get_tbl();
129 * timer_interrupt - gets called when the decrementer overflows,
130 * with interrupts disabled.
131 * We set it up to overflow again in 1/HZ seconds.
133 void timer_interrupt(struct pt_regs
* regs
)
136 unsigned long cpu
= smp_processor_id();
137 unsigned jiffy_stamp
= last_jiffy_stamp(cpu
);
138 extern void do_IRQ(struct pt_regs
*);
140 if (atomic_read(&ppc_n_lost_interrupts
) != 0)
145 while ((next_dec
= tb_ticks_per_jiffy
- tb_delta(&jiffy_stamp
)) <= 0) {
146 jiffy_stamp
+= tb_ticks_per_jiffy
;
148 profile_tick(CPU_PROFILING
, regs
);
149 update_process_times(user_mode(regs
));
151 if (smp_processor_id())
154 /* We are in an interrupt, no need to save/restore flags */
155 write_seqlock(&xtime_lock
);
156 tb_last_stamp
= jiffy_stamp
;
160 * update the rtc when needed, this should be performed on the
161 * right fraction of a second. Half or full second ?
162 * Full second works on mk48t59 clocks, others need testing.
163 * Note that this update is basically only used through
164 * the adjtimex system calls. Setting the HW clock in
165 * any other way is a /dev/rtc and userland business.
166 * This is still wrong by -0.5/+1.5 jiffies because of the
167 * timer interrupt resolution and possible delay, but here we
168 * hit a quantization limit which can only be solved by higher
169 * resolution timers and decoupling time management from timer
170 * interrupts. This is also wrong on the clocks
171 * which require being written at the half second boundary.
172 * We should have an rtc call that only sets the minutes and
173 * seconds like on Intel to avoid problems with non UTC clocks.
175 if ( ppc_md
.set_rtc_time
&& ntp_synced() &&
176 xtime
.tv_sec
- last_rtc_update
>= 659 &&
177 abs((xtime
.tv_nsec
/ 1000) - (1000000-1000000/HZ
)) < 500000/HZ
&&
178 jiffies
- wall_jiffies
== 1) {
179 if (ppc_md
.set_rtc_time(xtime
.tv_sec
+1 + timezone_offset
) == 0)
180 last_rtc_update
= xtime
.tv_sec
+1;
182 /* Try again one minute later */
183 last_rtc_update
+= 60;
185 write_sequnlock(&xtime_lock
);
187 if ( !disarm_decr
[smp_processor_id()] )
189 last_jiffy_stamp(cpu
) = jiffy_stamp
;
191 if (ppc_md
.heartbeat
&& !ppc_md
.heartbeat_count
--)
198 * This version of gettimeofday has microsecond resolution.
200 void do_gettimeofday(struct timeval
*tv
)
204 unsigned delta
, lost_ticks
, usec
, sec
;
207 seq
= read_seqbegin_irqsave(&xtime_lock
, flags
);
209 usec
= (xtime
.tv_nsec
/ 1000);
210 delta
= tb_ticks_since(tb_last_stamp
);
212 /* As long as timebases are not in sync, gettimeofday can only
213 * have jiffy resolution on SMP.
215 if (!smp_tb_synchronized
)
217 #endif /* CONFIG_SMP */
218 lost_ticks
= jiffies
- wall_jiffies
;
219 } while (read_seqretry_irqrestore(&xtime_lock
, seq
, flags
));
221 usec
+= mulhwu(tb_to_us
, tb_ticks_per_jiffy
* lost_ticks
+ delta
);
222 while (usec
>= 1000000) {
230 EXPORT_SYMBOL(do_gettimeofday
);
232 int do_settimeofday(struct timespec
*tv
)
234 time_t wtm_sec
, new_sec
= tv
->tv_sec
;
235 long wtm_nsec
, new_nsec
= tv
->tv_nsec
;
239 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
242 write_seqlock_irqsave(&xtime_lock
, flags
);
243 /* Updating the RTC is not the job of this code. If the time is
244 * stepped under NTP, the RTC will be update after STA_UNSYNC
245 * is cleared. Tool like clock/hwclock either copy the RTC
246 * to the system time, in which case there is no point in writing
247 * to the RTC again, or write to the RTC but then they don't call
248 * settimeofday to perform this operation. Note also that
249 * we don't touch the decrementer since:
250 * a) it would lose timer interrupt synchronization on SMP
251 * (if it is working one day)
252 * b) it could make one jiffy spuriously shorter or longer
253 * which would introduce another source of uncertainty potentially
254 * harmful to relatively short timers.
257 /* This works perfectly on SMP only if the tb are in sync but
258 * guarantees an error < 1 jiffy even if they are off by eons,
259 * still reasonable when gettimeofday resolution is 1 jiffy.
261 tb_delta
= tb_ticks_since(last_jiffy_stamp(smp_processor_id()));
262 tb_delta
+= (jiffies
- wall_jiffies
) * tb_ticks_per_jiffy
;
264 new_nsec
-= 1000 * mulhwu(tb_to_us
, tb_delta
);
266 wtm_sec
= wall_to_monotonic
.tv_sec
+ (xtime
.tv_sec
- new_sec
);
267 wtm_nsec
= wall_to_monotonic
.tv_nsec
+ (xtime
.tv_nsec
- new_nsec
);
269 set_normalized_timespec(&xtime
, new_sec
, new_nsec
);
270 set_normalized_timespec(&wall_to_monotonic
, wtm_sec
, wtm_nsec
);
272 /* In case of a large backwards jump in time with NTP, we want the
273 * clock to be updated as soon as the PLL is again in lock.
275 last_rtc_update
= new_sec
- 658;
278 write_sequnlock_irqrestore(&xtime_lock
, flags
);
283 EXPORT_SYMBOL(do_settimeofday
);
285 /* This function is only called on the boot processor */
286 void __init
time_init(void)
289 unsigned old_stamp
, stamp
, elapsed
;
291 if (ppc_md
.time_init
!= NULL
)
292 timezone_offset
= ppc_md
.time_init();
295 /* 601 processor: dec counts down by 128 every 128ns */
296 tb_ticks_per_jiffy
= DECREMENTER_COUNT_601
;
297 /* mulhwu_scale_factor(1000000000, 1000000) is 0x418937 */
300 ppc_md
.calibrate_decr();
301 tb_to_ns_scale
= mulhwu(tb_to_us
, 1000 << 10);
304 /* Now that the decrementer is calibrated, it can be used in case the
305 * clock is stuck, but the fact that we have to handle the 601
306 * makes things more complex. Repeatedly read the RTC until the
307 * next second boundary to try to achieve some precision. If there
308 * is no RTC, we still need to set tb_last_stamp and
309 * last_jiffy_stamp(cpu 0) to the current stamp.
311 stamp
= get_native_tbl();
312 if (ppc_md
.get_rtc_time
) {
313 sec
= ppc_md
.get_rtc_time();
318 stamp
= get_native_tbl();
319 if (__USE_RTC() && stamp
< old_stamp
)
320 old_stamp
-= 1000000000;
321 elapsed
+= stamp
- old_stamp
;
322 sec
= ppc_md
.get_rtc_time();
323 } while ( sec
== old_sec
&& elapsed
< 2*HZ
*tb_ticks_per_jiffy
);
325 printk("Warning: real time clock seems stuck!\n");
328 /* No update now, we just read the time from the RTC ! */
329 last_rtc_update
= xtime
.tv_sec
;
331 last_jiffy_stamp(0) = tb_last_stamp
= stamp
;
333 /* Not exact, but the timer interrupt takes care of this */
334 set_dec(tb_ticks_per_jiffy
);
336 /* If platform provided a timezone (pmac), we correct the time */
337 if (timezone_offset
) {
338 sys_tz
.tz_minuteswest
= -timezone_offset
/ 60;
339 sys_tz
.tz_dsttime
= 0;
340 xtime
.tv_sec
-= timezone_offset
;
342 set_normalized_timespec(&wall_to_monotonic
,
343 -xtime
.tv_sec
, -xtime
.tv_nsec
);
347 #define STARTOFTIME 1970
348 #define SECDAY 86400L
349 #define SECYR (SECDAY * 365)
352 * Note: this is wrong for 2100, but our signed 32-bit time_t will
353 * have overflowed long before that, so who cares. -- paulus
355 #define leapyear(year) ((year) % 4 == 0)
356 #define days_in_year(a) (leapyear(a) ? 366 : 365)
357 #define days_in_month(a) (month_days[(a) - 1])
359 static int month_days
[12] = {
360 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
363 void to_tm(int tim
, struct rtc_time
* tm
)
366 register long hms
, day
, gday
;
368 gday
= day
= tim
/ SECDAY
;
371 /* Hours, minutes, seconds are easy */
372 tm
->tm_hour
= hms
/ 3600;
373 tm
->tm_min
= (hms
% 3600) / 60;
374 tm
->tm_sec
= (hms
% 3600) % 60;
376 /* Number of years in days */
377 for (i
= STARTOFTIME
; day
>= days_in_year(i
); i
++)
378 day
-= days_in_year(i
);
381 /* Number of months in days left */
382 if (leapyear(tm
->tm_year
))
383 days_in_month(FEBRUARY
) = 29;
384 for (i
= 1; day
>= days_in_month(i
); i
++)
385 day
-= days_in_month(i
);
386 days_in_month(FEBRUARY
) = 28;
389 /* Days are what is left over (+1) from all that. */
390 tm
->tm_mday
= day
+ 1;
393 * Determine the day of week. Jan. 1, 1970 was a Thursday.
395 tm
->tm_wday
= (gday
+ 4) % 7;
398 /* Auxiliary function to compute scaling factors */
399 /* Actually the choice of a timebase running at 1/4 the of the bus
400 * frequency giving resolution of a few tens of nanoseconds is quite nice.
401 * It makes this computation very precise (27-28 bits typically) which
402 * is optimistic considering the stability of most processor clock
403 * oscillators and the precision with which the timebase frequency
404 * is measured but does not harm.
406 unsigned mulhwu_scale_factor(unsigned inscale
, unsigned outscale
) {
407 unsigned mlt
=0, tmp
, err
;
408 /* No concern for performance, it's done once: use a stupid
409 * but safe and compact method to find the multiplier.
411 for (tmp
= 1U<<31; tmp
!= 0; tmp
>>= 1) {
412 if (mulhwu(inscale
, mlt
|tmp
) < outscale
) mlt
|=tmp
;
414 /* We might still be off by 1 for the best approximation.
415 * A side effect of this is that if outscale is too large
416 * the returned value will be zero.
417 * Many corner cases have been checked and seem to work,
418 * some might have been forgotten in the test however.
420 err
= inscale
*(mlt
+1);
421 if (err
<= inscale
/2) mlt
++;
425 unsigned long long sched_clock(void)
427 unsigned long lo
, hi
, hi2
;
428 unsigned long long tb
;
436 tb
= ((unsigned long long) hi
<< 32) | lo
;
437 tb
= (tb
* tb_to_ns_scale
) >> 10;
444 tb
= ((unsigned long long) hi
) * 1000000000 + lo
;