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![Roman Zippel](/assets/img/avatar_default.png)
This converts time_freq to a scaled nsec value and adds around 6bit of extra resolution. This pushes the time_freq to its 32bit limits so the calculatons have to be done with 64bit. Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Cc: john stultz <johnstul@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
363 lines
11 KiB
C
363 lines
11 KiB
C
/*
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* linux/kernel/time/ntp.c
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*
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* NTP state machine interfaces and logic.
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*
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* This code was mainly moved from kernel/timer.c and kernel/time.c
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* Please see those files for relevant copyright info and historical
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* changelogs.
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*/
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#include <linux/mm.h>
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#include <linux/time.h>
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#include <linux/timex.h>
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#include <asm/div64.h>
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#include <asm/timex.h>
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/*
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* Timekeeping variables
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*/
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unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */
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unsigned long tick_nsec; /* ACTHZ period (nsec) */
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static u64 tick_length, tick_length_base;
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#define MAX_TICKADJ 500 /* microsecs */
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#define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
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TICK_LENGTH_SHIFT) / HZ)
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/*
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* phase-lock loop variables
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*/
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/* TIME_ERROR prevents overwriting the CMOS clock */
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int time_state = TIME_OK; /* clock synchronization status */
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int time_status = STA_UNSYNC; /* clock status bits */
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long time_offset; /* time adjustment (ns) */
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long time_constant = 2; /* pll time constant */
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long time_precision = 1; /* clock precision (us) */
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long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */
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long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
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long time_freq; /* frequency offset (scaled ppm)*/
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long time_reftime; /* time at last adjustment (s) */
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long time_adjust;
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/**
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* ntp_clear - Clears the NTP state variables
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*
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* Must be called while holding a write on the xtime_lock
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*/
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void ntp_clear(void)
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{
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time_adjust = 0; /* stop active adjtime() */
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time_status |= STA_UNSYNC;
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time_maxerror = NTP_PHASE_LIMIT;
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time_esterror = NTP_PHASE_LIMIT;
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ntp_update_frequency();
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tick_length = tick_length_base;
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time_offset = 0;
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}
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#define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE)
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#define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / (s64)CLOCK_TICK_RATE)
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void ntp_update_frequency(void)
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{
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tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
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tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
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tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
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do_div(tick_length_base, HZ);
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tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT;
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}
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/*
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* this routine handles the overflow of the microsecond field
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*
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* The tricky bits of code to handle the accurate clock support
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* were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
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* They were originally developed for SUN and DEC kernels.
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* All the kudos should go to Dave for this stuff.
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*/
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void second_overflow(void)
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{
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long time_adj;
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/* Bump the maxerror field */
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time_maxerror += MAXFREQ >> SHIFT_USEC;
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if (time_maxerror > NTP_PHASE_LIMIT) {
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time_maxerror = NTP_PHASE_LIMIT;
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time_status |= STA_UNSYNC;
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}
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/*
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* Leap second processing. If in leap-insert state at the end of the
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* day, the system clock is set back one second; if in leap-delete
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* state, the system clock is set ahead one second. The microtime()
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* routine or external clock driver will insure that reported time is
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* always monotonic. The ugly divides should be replaced.
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*/
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switch (time_state) {
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case TIME_OK:
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if (time_status & STA_INS)
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time_state = TIME_INS;
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else if (time_status & STA_DEL)
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time_state = TIME_DEL;
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break;
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case TIME_INS:
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if (xtime.tv_sec % 86400 == 0) {
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xtime.tv_sec--;
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wall_to_monotonic.tv_sec++;
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/*
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* The timer interpolator will make time change
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* gradually instead of an immediate jump by one second
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*/
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time_interpolator_update(-NSEC_PER_SEC);
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time_state = TIME_OOP;
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clock_was_set();
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printk(KERN_NOTICE "Clock: inserting leap second "
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"23:59:60 UTC\n");
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}
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break;
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case TIME_DEL:
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if ((xtime.tv_sec + 1) % 86400 == 0) {
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xtime.tv_sec++;
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wall_to_monotonic.tv_sec--;
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/*
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* Use of time interpolator for a gradual change of
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* time
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*/
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time_interpolator_update(NSEC_PER_SEC);
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time_state = TIME_WAIT;
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clock_was_set();
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printk(KERN_NOTICE "Clock: deleting leap second "
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"23:59:59 UTC\n");
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}
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break;
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case TIME_OOP:
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time_state = TIME_WAIT;
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break;
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case TIME_WAIT:
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if (!(time_status & (STA_INS | STA_DEL)))
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time_state = TIME_OK;
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}
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/*
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* Compute the phase adjustment for the next second. In PLL mode, the
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* offset is reduced by a fixed factor times the time constant. In FLL
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* mode the offset is used directly. In either mode, the maximum phase
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* adjustment for each second is clamped so as to spread the adjustment
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* over not more than the number of seconds between updates.
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*/
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tick_length = tick_length_base;
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time_adj = time_offset;
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if (!(time_status & STA_FLL))
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time_adj = shift_right(time_adj, SHIFT_KG + time_constant);
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time_adj = min(time_adj, -((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
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time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
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time_offset -= time_adj;
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tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
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if (unlikely(time_adjust)) {
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if (time_adjust > MAX_TICKADJ) {
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time_adjust -= MAX_TICKADJ;
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tick_length += MAX_TICKADJ_SCALED;
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} else if (time_adjust < -MAX_TICKADJ) {
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time_adjust += MAX_TICKADJ;
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tick_length -= MAX_TICKADJ_SCALED;
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} else {
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time_adjust = 0;
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tick_length += (s64)(time_adjust * NSEC_PER_USEC /
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HZ) << TICK_LENGTH_SHIFT;
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}
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}
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}
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/*
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* Return how long ticks are at the moment, that is, how much time
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* update_wall_time_one_tick will add to xtime next time we call it
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* (assuming no calls to do_adjtimex in the meantime).
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* The return value is in fixed-point nanoseconds shifted by the
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* specified number of bits to the right of the binary point.
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* This function has no side-effects.
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*/
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u64 current_tick_length(void)
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{
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return tick_length;
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}
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void __attribute__ ((weak)) notify_arch_cmos_timer(void)
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{
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return;
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}
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/* adjtimex mainly allows reading (and writing, if superuser) of
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* kernel time-keeping variables. used by xntpd.
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*/
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int do_adjtimex(struct timex *txc)
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{
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long ltemp, mtemp, save_adjust;
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s64 freq_adj;
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int result;
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/* In order to modify anything, you gotta be super-user! */
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if (txc->modes && !capable(CAP_SYS_TIME))
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return -EPERM;
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/* Now we validate the data before disabling interrupts */
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if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
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/* singleshot must not be used with any other mode bits */
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if (txc->modes != ADJ_OFFSET_SINGLESHOT)
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return -EINVAL;
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if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
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/* adjustment Offset limited to +- .512 seconds */
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if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
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return -EINVAL;
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/* if the quartz is off by more than 10% something is VERY wrong ! */
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if (txc->modes & ADJ_TICK)
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if (txc->tick < 900000/USER_HZ ||
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txc->tick > 1100000/USER_HZ)
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return -EINVAL;
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write_seqlock_irq(&xtime_lock);
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result = time_state; /* mostly `TIME_OK' */
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/* Save for later - semantics of adjtime is to return old value */
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save_adjust = time_adjust;
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#if 0 /* STA_CLOCKERR is never set yet */
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time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
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#endif
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/* If there are input parameters, then process them */
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if (txc->modes)
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{
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if (txc->modes & ADJ_STATUS) /* only set allowed bits */
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time_status = (txc->status & ~STA_RONLY) |
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(time_status & STA_RONLY);
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if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */
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if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
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result = -EINVAL;
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goto leave;
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}
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time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC);
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}
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if (txc->modes & ADJ_MAXERROR) {
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if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
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result = -EINVAL;
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goto leave;
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}
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time_maxerror = txc->maxerror;
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}
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if (txc->modes & ADJ_ESTERROR) {
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if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
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result = -EINVAL;
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goto leave;
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}
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time_esterror = txc->esterror;
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}
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if (txc->modes & ADJ_TIMECONST) { /* p. 24 */
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if (txc->constant < 0) { /* NTP v4 uses values > 6 */
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result = -EINVAL;
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goto leave;
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}
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time_constant = txc->constant;
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}
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if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
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if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
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/* adjtime() is independent from ntp_adjtime() */
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time_adjust = txc->offset;
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}
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else if (time_status & STA_PLL) {
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ltemp = txc->offset * NSEC_PER_USEC;
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/*
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* Scale the phase adjustment and
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* clamp to the operating range.
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*/
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time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC);
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time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC);
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/*
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* Select whether the frequency is to be controlled
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* and in which mode (PLL or FLL). Clamp to the operating
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* range. Ugly multiply/divide should be replaced someday.
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*/
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if (time_status & STA_FREQHOLD || time_reftime == 0)
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time_reftime = xtime.tv_sec;
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mtemp = xtime.tv_sec - time_reftime;
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time_reftime = xtime.tv_sec;
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freq_adj = 0;
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if (time_status & STA_FLL) {
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if (mtemp >= MINSEC) {
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freq_adj = (s64)time_offset << (SHIFT_NSEC - SHIFT_KH);
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if (time_offset < 0) {
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freq_adj = -freq_adj;
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do_div(freq_adj, mtemp);
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freq_adj = -freq_adj;
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} else
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do_div(freq_adj, mtemp);
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} else /* calibration interval too short (p. 12) */
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result = TIME_ERROR;
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} else { /* PLL mode */
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if (mtemp < MAXSEC) {
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freq_adj = (s64)ltemp * mtemp;
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freq_adj = shift_right(freq_adj,(time_constant +
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time_constant +
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SHIFT_KF - SHIFT_NSEC));
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} else /* calibration interval too long (p. 12) */
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result = TIME_ERROR;
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}
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freq_adj += time_freq;
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freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
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time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
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time_offset = (time_offset / HZ) << SHIFT_UPDATE;
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} /* STA_PLL */
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} /* txc->modes & ADJ_OFFSET */
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if (txc->modes & ADJ_TICK)
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tick_usec = txc->tick;
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if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
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ntp_update_frequency();
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} /* txc->modes */
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leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
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result = TIME_ERROR;
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if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
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txc->offset = save_adjust;
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else
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txc->offset = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000;
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txc->freq = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC);
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txc->maxerror = time_maxerror;
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txc->esterror = time_esterror;
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txc->status = time_status;
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txc->constant = time_constant;
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txc->precision = time_precision;
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txc->tolerance = MAXFREQ;
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txc->tick = tick_usec;
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/* PPS is not implemented, so these are zero */
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txc->ppsfreq = 0;
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txc->jitter = 0;
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txc->shift = 0;
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txc->stabil = 0;
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txc->jitcnt = 0;
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txc->calcnt = 0;
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txc->errcnt = 0;
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txc->stbcnt = 0;
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write_sequnlock_irq(&xtime_lock);
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do_gettimeofday(&txc->time);
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notify_arch_cmos_timer();
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return(result);
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}
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