/* * 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 unsigned long disarm_decr[NR_CPUS]; extern struct timezone sys_tz; /* keep track of when we need to update the rtc */ time_t last_rtc_update; /* 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; unsigned long tb_to_ns_scale; /* used for timezone offset */ static long timezone_offset; DEFINE_SPINLOCK(rtc_lock); 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; } #ifdef CONFIG_SMP unsigned long profile_pc(struct pt_regs *regs) { unsigned long pc = instruction_pointer(regs); if (in_lock_functions(pc)) return regs->link; return pc; } EXPORT_SYMBOL(profile_pc); #endif void wakeup_decrementer(void) { set_dec(tb_ticks_per_jiffy); /* No currently-supported powerbook has a 601, * so use get_tbl, not native */ last_jiffy_stamp(0) = tb_last_stamp = get_tbl(); } /* * timer_interrupt - gets called when the decrementer overflows, * with interrupts disabled. * We set it up to overflow again in 1/HZ seconds. */ void timer_interrupt(struct pt_regs * regs) { struct pt_regs *old_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); old_regs = set_irq_regs(regs); irq_enter(); while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) <= 0) { jiffy_stamp += tb_ticks_per_jiffy; profile_tick(CPU_PROFILING); update_process_times(user_mode(regs)); if (smp_processor_id()) continue; /* We are in an interrupt, no need to save/restore flags */ write_seqlock(&xtime_lock); tb_last_stamp = jiffy_stamp; do_timer(1); /* * 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 && ntp_synced() && xtime.tv_sec - last_rtc_update >= 659 && abs((xtime.tv_nsec / 1000) - (1000000-1000000/HZ)) < 500000/HZ) { 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_sequnlock(&xtime_lock); } if ( !disarm_decr[smp_processor_id()] ) set_dec(next_dec); last_jiffy_stamp(cpu) = jiffy_stamp; if (ppc_md.heartbeat && !ppc_md.heartbeat_count--) ppc_md.heartbeat(); irq_exit(); set_irq_regs(old_regs); } /* * This version of gettimeofday has microsecond resolution. */ void do_gettimeofday(struct timeval *tv) { unsigned long flags; unsigned long seq; unsigned delta, usec, sec; do { seq = read_seqbegin_irqsave(&xtime_lock, flags); sec = xtime.tv_sec; usec = (xtime.tv_nsec / 1000); 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 */ } while (read_seqretry_irqrestore(&xtime_lock, seq, flags)); usec += mulhwu(tb_to_us, delta); while (usec >= 1000000) { sec++; usec -= 1000000; } tv->tv_sec = sec; tv->tv_usec = usec; } EXPORT_SYMBOL(do_gettimeofday); int do_settimeofday(struct timespec *tv) { time_t wtm_sec, new_sec = tv->tv_sec; long wtm_nsec, new_nsec = tv->tv_nsec; unsigned long flags; int tb_delta; if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) return -EINVAL; write_seqlock_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())); new_nsec -= 1000 * mulhwu(tb_to_us, tb_delta); wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec); wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec); set_normalized_timespec(&xtime, new_sec, new_nsec); set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec); /* 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; ntp_clear(); write_sequnlock_irqrestore(&xtime_lock, flags); clock_was_set(); return 0; } EXPORT_SYMBOL(do_settimeofday); /* 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(); tb_to_ns_scale = mulhwu(tb_to_us, 1000 << 10); } /* 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_nsec = 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 */ if (timezone_offset) { sys_tz.tz_minuteswest = -timezone_offset / 60; sys_tz.tz_dsttime = 0; xtime.tv_sec -= timezone_offset; } set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec); } #define FEBRUARY 2 #define STARTOFTIME 1970 #define SECDAY 86400L #define SECYR (SECDAY * 365) /* * Note: this is wrong for 2100, but our signed 32-bit time_t will * have overflowed long before that, so who cares. -- paulus */ #define leapyear(year) ((year) % 4 == 0) #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; } unsigned long long sched_clock(void) { unsigned long lo, hi, hi2; unsigned long long tb; if (!__USE_RTC()) { do { hi = get_tbu(); lo = get_tbl(); hi2 = get_tbu(); } while (hi2 != hi); tb = ((unsigned long long) hi << 32) | lo; tb = (tb * tb_to_ns_scale) >> 10; } else { do { hi = get_rtcu(); lo = get_rtcl(); hi2 = get_rtcu(); } while (hi2 != hi); tb = ((unsigned long long) hi) * 1000000000 + lo; } return tb; }