1 /*
2 * Common time routines among all ppc machines.
3 *
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).
7 *
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).
13 *
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.
25 *
26 *
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
40 *
41 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
42 * "A Kernel Model for Precision Timekeeping" by Dave Mills
43 */
44
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>
51 #include <linux/mm.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
60 #include <asm/segment.h>
61 #include <asm/io.h>
62 #include <asm/processor.h>
63 #include <asm/nvram.h>
64 #include <asm/cache.h>
65 #include <asm/8xx_immap.h>
66 #include <asm/machdep.h>
67
68 #include <asm/time.h>
69
70 unsigned long disarm_decr[NR_CPUS];
71
72 extern int do_sys_settimeofday(struct timeval *tv, struct timezone *tz);
73
74 /* keep track of when we need to update the rtc */
75 time_t last_rtc_update;
76 extern rwlock_t xtime_lock;
77
78 /* The decrementer counts down by 128 every 128ns on a 601. */
79 #define DECREMENTER_COUNT_601 (1000000000 / HZ)
80
81 unsigned tb_ticks_per_jiffy;
82 unsigned tb_to_us;
83 unsigned tb_last_stamp;
84
85 extern unsigned long wall_jiffies;
86
87 static long timezone_offset;
88
89 spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
90
91 EXPORT_SYMBOL(rtc_lock);
92
93 /* Timer interrupt helper function */
tb_delta(unsigned * jiffy_stamp)94 static inline int tb_delta(unsigned *jiffy_stamp) {
95 int delta;
96 if (__USE_RTC()) {
97 delta = get_rtcl();
98 if (delta < *jiffy_stamp) *jiffy_stamp -= 1000000000;
99 delta -= *jiffy_stamp;
100 } else {
101 delta = get_tbl() - *jiffy_stamp;
102 }
103 return delta;
104 }
105
106 extern unsigned long prof_cpu_mask;
107 extern unsigned int * prof_buffer;
108 extern unsigned long prof_len;
109 extern unsigned long prof_shift;
110 extern char _stext;
111
ppc_do_profile(unsigned long nip)112 static inline void ppc_do_profile (unsigned long nip)
113 {
114 if (!prof_buffer)
115 return;
116
117 /*
118 * Only measure the CPUs specified by /proc/irq/prof_cpu_mask.
119 * (default is all CPUs.)
120 */
121 if (!((1<<smp_processor_id()) & prof_cpu_mask))
122 return;
123
124 nip -= (unsigned long) &_stext;
125 nip >>= prof_shift;
126 /*
127 * Don't ignore out-of-bounds EIP values silently,
128 * put them into the last histogram slot, so if
129 * present, they will show up as a sharp peak.
130 */
131 if (nip > prof_len-1)
132 nip = prof_len-1;
133 atomic_inc((atomic_t *)&prof_buffer[nip]);
134 }
135
136 /*
137 * timer_interrupt - gets called when the decrementer overflows,
138 * with interrupts disabled.
139 * We set it up to overflow again in 1/HZ seconds.
140 */
timer_interrupt(struct pt_regs * regs)141 int timer_interrupt(struct pt_regs * regs)
142 {
143 int next_dec;
144 unsigned long cpu = smp_processor_id();
145 unsigned jiffy_stamp = last_jiffy_stamp(cpu);
146 extern void do_IRQ(struct pt_regs *);
147
148 if (atomic_read(&ppc_n_lost_interrupts) != 0)
149 do_IRQ(regs);
150
151 hardirq_enter(cpu);
152
153 while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) <= 0) {
154 jiffy_stamp += tb_ticks_per_jiffy;
155 if (!user_mode(regs))
156 ppc_do_profile(instruction_pointer(regs));
157 if (unlikely(!heartbeat_count(cpu)--)
158 && heartbeat_reset(cpu)) {
159 ppc_md.heartbeat();
160 heartbeat_count(cpu) = heartbeat_reset(cpu);
161 }
162 if (cpu)
163 continue;
164
165 /* We are in an interrupt, no need to save/restore flags */
166 write_lock(&xtime_lock);
167 tb_last_stamp = jiffy_stamp;
168 do_timer(regs);
169
170 /*
171 * update the rtc when needed, this should be performed on the
172 * right fraction of a second. Half or full second ?
173 * Full second works on mk48t59 clocks, others need testing.
174 * Note that this update is basically only used through
175 * the adjtimex system calls. Setting the HW clock in
176 * any other way is a /dev/rtc and userland business.
177 * This is still wrong by -0.5/+1.5 jiffies because of the
178 * timer interrupt resolution and possible delay, but here we
179 * hit a quantization limit which can only be solved by higher
180 * resolution timers and decoupling time management from timer
181 * interrupts. This is also wrong on the clocks
182 * which require being written at the half second boundary.
183 * We should have an rtc call that only sets the minutes and
184 * seconds like on Intel to avoid problems with non UTC clocks.
185 */
186 if ( ppc_md.set_rtc_time && (time_status & STA_UNSYNC) == 0 &&
187 xtime.tv_sec - last_rtc_update >= 659 &&
188 abs(xtime.tv_usec - (1000000-1000000/HZ)) < 500000/HZ &&
189 jiffies - wall_jiffies == 1) {
190 if (ppc_md.set_rtc_time(xtime.tv_sec+1 + timezone_offset) == 0)
191 last_rtc_update = xtime.tv_sec+1;
192 else
193 /* Try again one minute later */
194 last_rtc_update += 60;
195 }
196 write_unlock(&xtime_lock);
197 }
198 if (!disarm_decr[cpu])
199 set_dec(next_dec);
200 last_jiffy_stamp(cpu) = jiffy_stamp;
201
202 #ifdef CONFIG_SMP
203 smp_local_timer_interrupt(regs);
204 #endif /* CONFIG_SMP */
205
206 hardirq_exit(cpu);
207
208 if (softirq_pending(cpu))
209 do_softirq();
210
211 return 1; /* lets ret_from_int know we can do checks */
212 }
213
214 /*
215 * This version of gettimeofday has microsecond resolution.
216 */
do_gettimeofday(struct timeval * tv)217 void do_gettimeofday(struct timeval *tv)
218 {
219 unsigned long flags;
220 unsigned delta, lost_ticks, usec, sec;
221
222 read_lock_irqsave(&xtime_lock, flags);
223 sec = xtime.tv_sec;
224 usec = xtime.tv_usec;
225 delta = tb_ticks_since(tb_last_stamp);
226 #ifdef CONFIG_SMP
227 /* As long as timebases are not in sync, gettimeofday can only
228 * have jiffy resolution on SMP.
229 */
230 if (!smp_tb_synchronized)
231 delta = 0;
232 #endif /* CONFIG_SMP */
233 lost_ticks = jiffies - wall_jiffies;
234 read_unlock_irqrestore(&xtime_lock, flags);
235
236 usec += mulhwu(tb_to_us, tb_ticks_per_jiffy * lost_ticks + delta);
237 while (usec >= 1000000) {
238 sec++;
239 usec -= 1000000;
240 }
241 tv->tv_sec = sec;
242 tv->tv_usec = usec;
243 }
244
do_settimeofday(struct timeval * tv)245 void do_settimeofday(struct timeval *tv)
246 {
247 unsigned long flags;
248 int tb_delta, new_usec, new_sec;
249
250 write_lock_irqsave(&xtime_lock, flags);
251 /* Updating the RTC is not the job of this code. If the time is
252 * stepped under NTP, the RTC will be update after STA_UNSYNC
253 * is cleared. Tool like clock/hwclock either copy the RTC
254 * to the system time, in which case there is no point in writing
255 * to the RTC again, or write to the RTC but then they don't call
256 * settimeofday to perform this operation. Note also that
257 * we don't touch the decrementer since:
258 * a) it would lose timer interrupt synchronization on SMP
259 * (if it is working one day)
260 * b) it could make one jiffy spuriously shorter or longer
261 * which would introduce another source of uncertainty potentially
262 * harmful to relatively short timers.
263 */
264
265 /* This works perfectly on SMP only if the tb are in sync but
266 * guarantees an error < 1 jiffy even if they are off by eons,
267 * still reasonable when gettimeofday resolution is 1 jiffy.
268 */
269 tb_delta = tb_ticks_since(last_jiffy_stamp(smp_processor_id()));
270 tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;
271 new_sec = tv->tv_sec;
272 new_usec = tv->tv_usec - mulhwu(tb_to_us, tb_delta);
273 while (new_usec <0) {
274 new_sec--;
275 new_usec += 1000000;
276 }
277 xtime.tv_usec = new_usec;
278 xtime.tv_sec = new_sec;
279
280 /* In case of a large backwards jump in time with NTP, we want the
281 * clock to be updated as soon as the PLL is again in lock.
282 */
283 last_rtc_update = new_sec - 658;
284
285 time_adjust = 0; /* stop active adjtime() */
286 time_status |= STA_UNSYNC;
287 time_state = TIME_ERROR; /* p. 24, (a) */
288 time_maxerror = NTP_PHASE_LIMIT;
289 time_esterror = NTP_PHASE_LIMIT;
290 write_unlock_irqrestore(&xtime_lock, flags);
291 }
292
293 /* This function is only called on the boot processor */
time_init(void)294 void __init time_init(void)
295 {
296 time_t sec, old_sec;
297 unsigned old_stamp, stamp, elapsed;
298
299 if (ppc_md.time_init != NULL)
300 timezone_offset = ppc_md.time_init();
301
302 if (__USE_RTC()) {
303 /* 601 processor: dec counts down by 128 every 128ns */
304 tb_ticks_per_jiffy = DECREMENTER_COUNT_601;
305 /* mulhwu_scale_factor(1000000000, 1000000) is 0x418937 */
306 tb_to_us = 0x418937;
307 } else {
308 ppc_md.calibrate_decr();
309 }
310
311 /* Now that the decrementer is calibrated, it can be used in case the
312 * clock is stuck, but the fact that we have to handle the 601
313 * makes things more complex. Repeatedly read the RTC until the
314 * next second boundary to try to achieve some precision. If there
315 * is no RTC, we still need to set tb_last_stamp and
316 * last_jiffy_stamp(cpu 0) to the current stamp.
317 */
318 stamp = get_native_tbl();
319 if (ppc_md.get_rtc_time) {
320 sec = ppc_md.get_rtc_time();
321 elapsed = 0;
322 do {
323 old_stamp = stamp;
324 old_sec = sec;
325 stamp = get_native_tbl();
326 if (__USE_RTC() && stamp < old_stamp)
327 old_stamp -= 1000000000;
328 elapsed += stamp - old_stamp;
329 sec = ppc_md.get_rtc_time();
330 } while ( sec == old_sec && elapsed < 2*HZ*tb_ticks_per_jiffy);
331 if (sec == old_sec)
332 printk("Warning: real time clock seems stuck!\n");
333 xtime.tv_sec = sec;
334 xtime.tv_usec = 0;
335 /* No update now, we just read the time from the RTC ! */
336 last_rtc_update = xtime.tv_sec;
337 }
338
339 last_jiffy_stamp(0) = tb_last_stamp = stamp;
340
341 /* Not exact, but the timer interrupt takes care of this */
342 set_dec(tb_ticks_per_jiffy);
343
344 /* If platform provided a timezone (pmac), we correct the time
345 * using do_sys_settimeofday() which in turn calls warp_clock()
346 */
347 if (timezone_offset) {
348 struct timezone tz;
349 tz.tz_minuteswest = -timezone_offset / 60;
350 tz.tz_dsttime = 0;
351 do_sys_settimeofday(NULL, &tz);
352 }
353 }
354
355 #define FEBRUARY 2
356 #define STARTOFTIME 1970
357 #define SECDAY 86400L
358 #define SECYR (SECDAY * 365)
359 #define leapyear(y) ((!(y % 4) && (y % 100)) || !(y % 400))
360 #define days_in_year(a) (leapyear(a) ? 366 : 365)
361 #define days_in_month(a) (month_days[(a) - 1])
362
363 static int month_days[12] = {
364 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
365 };
366
to_tm(int tim,struct rtc_time * tm)367 void to_tm(int tim, struct rtc_time * tm)
368 {
369 register int i;
370 register long hms, day, gday;
371
372 gday = day = tim / SECDAY;
373 hms = tim % SECDAY;
374
375 /* Hours, minutes, seconds are easy */
376 tm->tm_hour = hms / 3600;
377 tm->tm_min = (hms % 3600) / 60;
378 tm->tm_sec = (hms % 3600) % 60;
379
380 /* Number of years in days */
381 for (i = STARTOFTIME; day >= days_in_year(i); i++)
382 day -= days_in_year(i);
383 tm->tm_year = i;
384
385 /* Number of months in days left */
386 if (leapyear(tm->tm_year))
387 days_in_month(FEBRUARY) = 29;
388 for (i = 1; day >= days_in_month(i); i++)
389 day -= days_in_month(i);
390 days_in_month(FEBRUARY) = 28;
391 tm->tm_mon = i;
392
393 /* Days are what is left over (+1) from all that. */
394 tm->tm_mday = day + 1;
395
396 /*
397 * Determine the day of week. Jan. 1, 1970 was a Thursday.
398 */
399 tm->tm_wday = (gday + 4) % 7;
400 }
401
402 /* Auxiliary function to compute scaling factors */
403 /* Actually the choice of a timebase running at 1/4 the of the bus
404 * frequency giving resolution of a few tens of nanoseconds is quite nice.
405 * It makes this computation very precise (27-28 bits typically) which
406 * is optimistic considering the stability of most processor clock
407 * oscillators and the precision with which the timebase frequency
408 * is measured but does not harm.
409 */
mulhwu_scale_factor(unsigned inscale,unsigned outscale)410 unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
411 unsigned mlt=0, tmp, err;
412 /* No concern for performance, it's done once: use a stupid
413 * but safe and compact method to find the multiplier.
414 */
415 for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
416 if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
417 }
418 /* We might still be off by 1 for the best approximation.
419 * A side effect of this is that if outscale is too large
420 * the returned value will be zero.
421 * Many corner cases have been checked and seem to work,
422 * some might have been forgotten in the test however.
423 */
424 err = inscale*(mlt+1);
425 if (err <= inscale/2) mlt++;
426 return mlt;
427 }
428
429