456 lines
12 KiB
C
456 lines
12 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 <linux/jiffies.h>
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#include <linux/hrtimer.h>
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#include <linux/capability.h>
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#include <linux/math64.h>
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#include <linux/clocksource.h>
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#include <linux/workqueue.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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u64 tick_length;
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static u64 tick_length_base;
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static struct hrtimer leap_timer;
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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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NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
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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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static int time_state = TIME_OK; /* clock synchronization status */
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int time_status = STA_UNSYNC; /* clock status bits */
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static long time_tai; /* TAI offset (s) */
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static s64 time_offset; /* time adjustment (ns) */
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static long time_constant = 2; /* pll time constant */
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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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static s64 time_freq; /* frequency offset (scaled ns/s)*/
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static long time_reftime; /* time at last adjustment (s) */
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long time_adjust;
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static long ntp_tick_adj;
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static void ntp_update_frequency(void)
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{
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u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
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<< NTP_SCALE_SHIFT;
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second_length += (s64)ntp_tick_adj << NTP_SCALE_SHIFT;
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second_length += time_freq;
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tick_length_base = second_length;
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tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
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tick_length_base = div_u64(tick_length_base, NTP_INTERVAL_FREQ);
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}
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static void ntp_update_offset(long offset)
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{
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long mtemp;
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s64 freq_adj;
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if (!(time_status & STA_PLL))
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return;
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if (!(time_status & STA_NANO))
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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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offset = min(offset, MAXPHASE);
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offset = max(offset, -MAXPHASE);
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/*
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* Select how the frequency is to be controlled
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* and in which mode (PLL or FLL).
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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 = (s64)offset * mtemp;
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freq_adj <<= NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant);
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time_status &= ~STA_MODE;
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if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
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freq_adj += div_s64((s64)offset << (NTP_SCALE_SHIFT - SHIFT_FLL),
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mtemp);
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time_status |= STA_MODE;
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}
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freq_adj += time_freq;
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freq_adj = min(freq_adj, MAXFREQ_SCALED);
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time_freq = max(freq_adj, -MAXFREQ_SCALED);
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time_offset = div_s64((s64)offset << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
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}
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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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/*
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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.
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*/
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static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
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{
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enum hrtimer_restart res = HRTIMER_NORESTART;
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write_seqlock_irq(&xtime_lock);
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switch (time_state) {
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case TIME_OK:
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break;
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case TIME_INS:
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xtime.tv_sec--;
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wall_to_monotonic.tv_sec++;
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time_state = TIME_OOP;
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printk(KERN_NOTICE "Clock: "
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"inserting leap second 23:59:60 UTC\n");
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leap_timer.expires = ktime_add_ns(leap_timer.expires,
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NSEC_PER_SEC);
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res = HRTIMER_RESTART;
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break;
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case TIME_DEL:
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xtime.tv_sec++;
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time_tai--;
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wall_to_monotonic.tv_sec--;
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time_state = TIME_WAIT;
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printk(KERN_NOTICE "Clock: "
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"deleting leap second 23:59:59 UTC\n");
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break;
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case TIME_OOP:
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time_tai++;
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time_state = TIME_WAIT;
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/* fall through */
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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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break;
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}
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update_vsyscall(&xtime, clock);
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write_sequnlock_irq(&xtime_lock);
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return res;
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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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s64 time_adj;
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/* Bump the maxerror field */
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time_maxerror += MAXFREQ / NSEC_PER_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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* Compute the phase adjustment for the next second. The offset is
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* reduced by a fixed factor times the time constant.
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*/
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tick_length = tick_length_base;
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time_adj = shift_right(time_offset, SHIFT_PLL + time_constant);
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time_offset -= time_adj;
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tick_length += time_adj;
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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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tick_length += (s64)(time_adjust * NSEC_PER_USEC /
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NTP_INTERVAL_FREQ) << NTP_SCALE_SHIFT;
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time_adjust = 0;
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}
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}
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}
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#ifdef CONFIG_GENERIC_CMOS_UPDATE
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/* Disable the cmos update - used by virtualization and embedded */
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int no_sync_cmos_clock __read_mostly;
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static void sync_cmos_clock(struct work_struct *work);
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static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
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static void sync_cmos_clock(struct work_struct *work)
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{
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struct timespec now, next;
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int fail = 1;
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/*
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* If we have an externally synchronized Linux clock, then update
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* CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
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* called as close as possible to 500 ms before the new second starts.
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* This code is run on a timer. If the clock is set, that timer
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* may not expire at the correct time. Thus, we adjust...
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*/
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if (!ntp_synced())
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/*
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* Not synced, exit, do not restart a timer (if one is
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* running, let it run out).
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*/
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return;
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getnstimeofday(&now);
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if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
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fail = update_persistent_clock(now);
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next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec;
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if (next.tv_nsec <= 0)
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next.tv_nsec += NSEC_PER_SEC;
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if (!fail)
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next.tv_sec = 659;
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else
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next.tv_sec = 0;
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if (next.tv_nsec >= NSEC_PER_SEC) {
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next.tv_sec++;
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next.tv_nsec -= NSEC_PER_SEC;
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}
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schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
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}
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static void notify_cmos_timer(void)
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{
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if (!no_sync_cmos_clock)
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schedule_delayed_work(&sync_cmos_work, 0);
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}
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#else
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static inline void notify_cmos_timer(void) { }
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#endif
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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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struct timespec ts;
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int result;
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/* Validate the data before disabling interrupts */
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if (txc->modes & ADJ_ADJTIME) {
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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_READONLY) &&
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!capable(CAP_SYS_TIME))
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return -EPERM;
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} else {
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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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/* 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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(txc->tick < 900000/USER_HZ ||
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txc->tick > 1100000/USER_HZ))
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return -EINVAL;
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if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
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hrtimer_cancel(&leap_timer);
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}
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getnstimeofday(&ts);
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write_seqlock_irq(&xtime_lock);
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/* If there are input parameters, then process them */
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if (txc->modes & ADJ_ADJTIME) {
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long save_adjust = time_adjust;
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if (!(txc->modes & ADJ_OFFSET_READONLY)) {
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/* adjtime() is independent from ntp_adjtime() */
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time_adjust = txc->offset;
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ntp_update_frequency();
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}
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txc->offset = save_adjust;
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goto adj_done;
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}
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if (txc->modes) {
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long sec;
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if (txc->modes & ADJ_STATUS) {
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if ((time_status & STA_PLL) &&
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!(txc->status & STA_PLL)) {
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time_state = TIME_OK;
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time_status = STA_UNSYNC;
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}
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/* only set allowed bits */
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time_status &= STA_RONLY;
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time_status |= txc->status & ~STA_RONLY;
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switch (time_state) {
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case TIME_OK:
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start_timer:
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sec = ts.tv_sec;
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if (time_status & STA_INS) {
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time_state = TIME_INS;
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sec += 86400 - sec % 86400;
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hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS);
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} else if (time_status & STA_DEL) {
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time_state = TIME_DEL;
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sec += 86400 - (sec + 1) % 86400;
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hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS);
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}
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break;
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case TIME_INS:
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case TIME_DEL:
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time_state = TIME_OK;
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goto start_timer;
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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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break;
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case TIME_OOP:
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hrtimer_restart(&leap_timer);
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break;
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}
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}
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if (txc->modes & ADJ_NANO)
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time_status |= STA_NANO;
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if (txc->modes & ADJ_MICRO)
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time_status &= ~STA_NANO;
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if (txc->modes & ADJ_FREQUENCY) {
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time_freq = (s64)txc->freq * PPM_SCALE;
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time_freq = min(time_freq, MAXFREQ_SCALED);
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time_freq = max(time_freq, -MAXFREQ_SCALED);
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}
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if (txc->modes & ADJ_MAXERROR)
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time_maxerror = txc->maxerror;
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if (txc->modes & ADJ_ESTERROR)
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time_esterror = txc->esterror;
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if (txc->modes & ADJ_TIMECONST) {
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time_constant = txc->constant;
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if (!(time_status & STA_NANO))
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time_constant += 4;
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time_constant = min(time_constant, (long)MAXTC);
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time_constant = max(time_constant, 0l);
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}
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if (txc->modes & ADJ_TAI && txc->constant > 0)
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time_tai = txc->constant;
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if (txc->modes & ADJ_OFFSET)
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ntp_update_offset(txc->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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}
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txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
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NTP_SCALE_SHIFT);
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if (!(time_status & STA_NANO))
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txc->offset /= NSEC_PER_USEC;
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adj_done:
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result = time_state; /* mostly `TIME_OK' */
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if (time_status & (STA_UNSYNC|STA_CLOCKERR))
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result = TIME_ERROR;
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txc->freq = shift_right((s32)(time_freq >> PPM_SCALE_INV_SHIFT) *
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(s64)PPM_SCALE_INV,
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NTP_SCALE_SHIFT);
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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 = 1;
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txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
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txc->tick = tick_usec;
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txc->tai = time_tai;
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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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txc->time.tv_sec = ts.tv_sec;
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txc->time.tv_usec = ts.tv_nsec;
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if (!(time_status & STA_NANO))
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txc->time.tv_usec /= NSEC_PER_USEC;
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notify_cmos_timer();
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return result;
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}
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static int __init ntp_tick_adj_setup(char *str)
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{
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ntp_tick_adj = simple_strtol(str, NULL, 0);
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return 1;
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}
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__setup("ntp_tick_adj=", ntp_tick_adj_setup);
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void __init ntp_init(void)
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{
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ntp_clear();
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hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
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leap_timer.function = ntp_leap_second;
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}
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