/* * Common time routines among all ppc machines. * * Written by Cort Dougan (cort@cs.nmt.edu) to merge * Paul Mackerras' version and mine for PReP and Pmac. * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net). * * First round of bugfixes by Gabriel Paubert (paubert@iram.es) * to make clock more stable (2.4.0-test5). The only thing * that this code assumes is that the timebases have been synchronized * by firmware on SMP and are never stopped (never do sleep * on SMP then, nap and doze are OK). * * TODO (not necessarily in this file): * - improve precision and reproducibility of timebase frequency * measurement at boot time. * - get rid of xtime_lock for gettimeofday (generic kernel problem * to be implemented on all architectures for SMP scalability and * eventually implementing gettimeofday without entering the kernel). * - put all time/clock related variables in a single structure * to minimize number of cache lines touched by gettimeofday() * - for astronomical applications: add a new function to get * non ambiguous timestamps even around leap seconds. This needs * a new timestamp format and a good name. * * * The following comment is partially obsolete (at least the long wait * is no more a valid reason): * Since the MPC8xx has a programmable interrupt timer, I decided to * use that rather than the decrementer. Two reasons: 1.) the clock * frequency is low, causing 2.) a long wait in the timer interrupt * while ((d = get_dec()) == dval) * loop. The MPC8xx can be driven from a variety of input clocks, * so a number of assumptions have been made here because the kernel * parameter HZ is a constant. We assume (correctly, today :-) that * the MPC8xx on the MBX board is driven from a 32.768 kHz crystal. * This is then divided by 4, providing a 8192 Hz clock into the PIT. * Since it is not possible to get a nice 100 Hz clock out of this, without * creating a software PLL, I have set HZ to 128. -- Dan * * 1997-09-10 Updated NTP code according to technical memorandum Jan '96 * "A Kernel Model for Precision Timekeeping" by Dave Mills */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include unsigned long disarm_decr[NR_CPUS]; extern int do_sys_settimeofday(struct timeval *tv, struct timezone *tz); /* keep track of when we need to update the rtc */ time_t last_rtc_update; extern rwlock_t xtime_lock; /* The decrementer counts down by 128 every 128ns on a 601. */ #define DECREMENTER_COUNT_601 (1000000000 / HZ) unsigned tb_ticks_per_jiffy; unsigned tb_to_us; unsigned tb_last_stamp; extern unsigned long wall_jiffies; static long timezone_offset; spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED; EXPORT_SYMBOL(rtc_lock); /* Timer interrupt helper function */ static inline int tb_delta(unsigned *jiffy_stamp) { int delta; if (__USE_RTC()) { delta = get_rtcl(); if (delta < *jiffy_stamp) *jiffy_stamp -= 1000000000; delta -= *jiffy_stamp; } else { delta = get_tbl() - *jiffy_stamp; } return delta; } extern unsigned long prof_cpu_mask; extern unsigned int * prof_buffer; extern unsigned long prof_len; extern unsigned long prof_shift; extern char _stext; static inline void ppc_do_profile (unsigned long nip) { if (!prof_buffer) return; /* * Only measure the CPUs specified by /proc/irq/prof_cpu_mask. * (default is all CPUs.) */ if (!((1<>= prof_shift; /* * Don't ignore out-of-bounds EIP values silently, * put them into the last histogram slot, so if * present, they will show up as a sharp peak. */ if (nip > prof_len-1) nip = prof_len-1; atomic_inc((atomic_t *)&prof_buffer[nip]); } /* * timer_interrupt - gets called when the decrementer overflows, * with interrupts disabled. * We set it up to overflow again in 1/HZ seconds. */ int timer_interrupt(struct pt_regs * regs) { int next_dec; unsigned long cpu = smp_processor_id(); unsigned jiffy_stamp = last_jiffy_stamp(cpu); extern void do_IRQ(struct pt_regs *); if (atomic_read(&ppc_n_lost_interrupts) != 0) do_IRQ(regs); hardirq_enter(cpu); while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) <= 0) { jiffy_stamp += tb_ticks_per_jiffy; if (!user_mode(regs)) ppc_do_profile(instruction_pointer(regs)); if (unlikely(!heartbeat_count(cpu)--) && heartbeat_reset(cpu)) { ppc_md.heartbeat(); heartbeat_count(cpu) = heartbeat_reset(cpu); } if (cpu) continue; /* We are in an interrupt, no need to save/restore flags */ write_lock(&xtime_lock); tb_last_stamp = jiffy_stamp; do_timer(regs); /* * update the rtc when needed, this should be performed on the * right fraction of a second. Half or full second ? * Full second works on mk48t59 clocks, others need testing. * Note that this update is basically only used through * the adjtimex system calls. Setting the HW clock in * any other way is a /dev/rtc and userland business. * This is still wrong by -0.5/+1.5 jiffies because of the * timer interrupt resolution and possible delay, but here we * hit a quantization limit which can only be solved by higher * resolution timers and decoupling time management from timer * interrupts. This is also wrong on the clocks * which require being written at the half second boundary. * We should have an rtc call that only sets the minutes and * seconds like on Intel to avoid problems with non UTC clocks. */ if ( ppc_md.set_rtc_time && (time_status & STA_UNSYNC) == 0 && xtime.tv_sec - last_rtc_update >= 659 && abs(xtime.tv_usec - (1000000-1000000/HZ)) < 500000/HZ && jiffies - wall_jiffies == 1) { if (ppc_md.set_rtc_time(xtime.tv_sec+1 + timezone_offset) == 0) last_rtc_update = xtime.tv_sec+1; else /* Try again one minute later */ last_rtc_update += 60; } write_unlock(&xtime_lock); } if (!disarm_decr[cpu]) set_dec(next_dec); last_jiffy_stamp(cpu) = jiffy_stamp; #ifdef CONFIG_SMP smp_local_timer_interrupt(regs); #endif /* CONFIG_SMP */ hardirq_exit(cpu); if (softirq_pending(cpu)) do_softirq(); return 1; /* lets ret_from_int know we can do checks */ } /* * This version of gettimeofday has microsecond resolution. */ void do_gettimeofday(struct timeval *tv) { unsigned long flags; unsigned delta, lost_ticks, usec, sec; read_lock_irqsave(&xtime_lock, flags); sec = xtime.tv_sec; usec = xtime.tv_usec; delta = tb_ticks_since(tb_last_stamp); #ifdef CONFIG_SMP /* As long as timebases are not in sync, gettimeofday can only * have jiffy resolution on SMP. */ if (!smp_tb_synchronized) delta = 0; #endif /* CONFIG_SMP */ lost_ticks = jiffies - wall_jiffies; read_unlock_irqrestore(&xtime_lock, flags); usec += mulhwu(tb_to_us, tb_ticks_per_jiffy * lost_ticks + delta); while (usec >= 1000000) { sec++; usec -= 1000000; } tv->tv_sec = sec; tv->tv_usec = usec; } void do_settimeofday(struct timeval *tv) { unsigned long flags; int tb_delta, new_usec, new_sec; write_lock_irqsave(&xtime_lock, flags); /* Updating the RTC is not the job of this code. If the time is * stepped under NTP, the RTC will be update after STA_UNSYNC * is cleared. Tool like clock/hwclock either copy the RTC * to the system time, in which case there is no point in writing * to the RTC again, or write to the RTC but then they don't call * settimeofday to perform this operation. Note also that * we don't touch the decrementer since: * a) it would lose timer interrupt synchronization on SMP * (if it is working one day) * b) it could make one jiffy spuriously shorter or longer * which would introduce another source of uncertainty potentially * harmful to relatively short timers. */ /* This works perfectly on SMP only if the tb are in sync but * guarantees an error < 1 jiffy even if they are off by eons, * still reasonable when gettimeofday resolution is 1 jiffy. */ tb_delta = tb_ticks_since(last_jiffy_stamp(smp_processor_id())); tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy; new_sec = tv->tv_sec; new_usec = tv->tv_usec - mulhwu(tb_to_us, tb_delta); while (new_usec <0) { new_sec--; new_usec += 1000000; } xtime.tv_usec = new_usec; xtime.tv_sec = new_sec; /* In case of a large backwards jump in time with NTP, we want the * clock to be updated as soon as the PLL is again in lock. */ last_rtc_update = new_sec - 658; time_adjust = 0; /* stop active adjtime() */ time_status |= STA_UNSYNC; time_state = TIME_ERROR; /* p. 24, (a) */ time_maxerror = NTP_PHASE_LIMIT; time_esterror = NTP_PHASE_LIMIT; write_unlock_irqrestore(&xtime_lock, flags); } /* This function is only called on the boot processor */ void __init time_init(void) { time_t sec, old_sec; unsigned old_stamp, stamp, elapsed; if (ppc_md.time_init != NULL) timezone_offset = ppc_md.time_init(); if (__USE_RTC()) { /* 601 processor: dec counts down by 128 every 128ns */ tb_ticks_per_jiffy = DECREMENTER_COUNT_601; /* mulhwu_scale_factor(1000000000, 1000000) is 0x418937 */ tb_to_us = 0x418937; } else { ppc_md.calibrate_decr(); } /* Now that the decrementer is calibrated, it can be used in case the * clock is stuck, but the fact that we have to handle the 601 * makes things more complex. Repeatedly read the RTC until the * next second boundary to try to achieve some precision. If there * is no RTC, we still need to set tb_last_stamp and * last_jiffy_stamp(cpu 0) to the current stamp. */ stamp = get_native_tbl(); if (ppc_md.get_rtc_time) { sec = ppc_md.get_rtc_time(); elapsed = 0; do { old_stamp = stamp; old_sec = sec; stamp = get_native_tbl(); if (__USE_RTC() && stamp < old_stamp) old_stamp -= 1000000000; elapsed += stamp - old_stamp; sec = ppc_md.get_rtc_time(); } while ( sec == old_sec && elapsed < 2*HZ*tb_ticks_per_jiffy); if (sec == old_sec) printk("Warning: real time clock seems stuck!\n"); xtime.tv_sec = sec; xtime.tv_usec = 0; /* No update now, we just read the time from the RTC ! */ last_rtc_update = xtime.tv_sec; } last_jiffy_stamp(0) = tb_last_stamp = stamp; /* Not exact, but the timer interrupt takes care of this */ set_dec(tb_ticks_per_jiffy); /* If platform provided a timezone (pmac), we correct the time * using do_sys_settimeofday() which in turn calls warp_clock() */ if (timezone_offset) { struct timezone tz; tz.tz_minuteswest = -timezone_offset / 60; tz.tz_dsttime = 0; do_sys_settimeofday(NULL, &tz); } } #define FEBRUARY 2 #define STARTOFTIME 1970 #define SECDAY 86400L #define SECYR (SECDAY * 365) #define leapyear(y) ((!(y % 4) && (y % 100)) || !(y % 400)) #define days_in_year(a) (leapyear(a) ? 366 : 365) #define days_in_month(a) (month_days[(a) - 1]) static int month_days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; void to_tm(int tim, struct rtc_time * tm) { register int i; register long hms, day, gday; gday = day = tim / SECDAY; hms = tim % SECDAY; /* Hours, minutes, seconds are easy */ tm->tm_hour = hms / 3600; tm->tm_min = (hms % 3600) / 60; tm->tm_sec = (hms % 3600) % 60; /* Number of years in days */ for (i = STARTOFTIME; day >= days_in_year(i); i++) day -= days_in_year(i); tm->tm_year = i; /* Number of months in days left */ if (leapyear(tm->tm_year)) days_in_month(FEBRUARY) = 29; for (i = 1; day >= days_in_month(i); i++) day -= days_in_month(i); days_in_month(FEBRUARY) = 28; tm->tm_mon = i; /* Days are what is left over (+1) from all that. */ tm->tm_mday = day + 1; /* * Determine the day of week. Jan. 1, 1970 was a Thursday. */ tm->tm_wday = (gday + 4) % 7; } /* Auxiliary function to compute scaling factors */ /* Actually the choice of a timebase running at 1/4 the of the bus * frequency giving resolution of a few tens of nanoseconds is quite nice. * It makes this computation very precise (27-28 bits typically) which * is optimistic considering the stability of most processor clock * oscillators and the precision with which the timebase frequency * is measured but does not harm. */ unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) { unsigned mlt=0, tmp, err; /* No concern for performance, it's done once: use a stupid * but safe and compact method to find the multiplier. */ for (tmp = 1U<<31; tmp != 0; tmp >>= 1) { if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp; } /* We might still be off by 1 for the best approximation. * A side effect of this is that if outscale is too large * the returned value will be zero. * Many corner cases have been checked and seem to work, * some might have been forgotten in the test however. */ err = inscale*(mlt+1); if (err <= inscale/2) mlt++; return mlt; }