/*
* linux/kernel/time/ntp.c
*
* NTP state machine interfaces and logic.
*
* This code was mainly moved from kernel/timer.c and kernel/time.c
* Please see those files for relevant copyright info and historical
* changelogs.
*/
#include <linux/mm.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <asm/div64.h>
#include <asm/timex.h>
/*
* Timekeeping variables
*/
unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */
unsigned long tick_nsec; /* ACTHZ period (nsec) */
static u64 tick_length, tick_length_base;
#define MAX_TICKADJ 500 /* microsecs */
#define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
TICK_LENGTH_SHIFT) / HZ)
/*
* phase-lock loop variables
*/
/* TIME_ERROR prevents overwriting the CMOS clock */
static int time_state = TIME_OK; /* clock synchronization status */
int time_status = STA_UNSYNC; /* clock status bits */
static long time_offset; /* time adjustment (ns) */
static long time_constant = 2; /* pll time constant */
long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */
long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
long time_freq; /* frequency offset (scaled ppm)*/
static long time_reftime; /* time at last adjustment (s) */
long time_adjust;
#define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE)
#define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / \
(s64)CLOCK_TICK_RATE)
static void ntp_update_frequency(void)
{
tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
do_div(tick_length_base, HZ);
tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT;
}
/**
* ntp_clear - Clears the NTP state variables
*
* Must be called while holding a write on the xtime_lock
*/
void ntp_clear(void)
{
time_adjust = 0; /* stop active adjtime() */
time_status |= STA_UNSYNC;
time_maxerror = NTP_PHASE_LIMIT;
time_esterror = NTP_PHASE_LIMIT;
ntp_update_frequency();
tick_length = tick_length_base;
time_offset = 0;
}
/*
* this routine handles the overflow of the microsecond field
*
* The tricky bits of code to handle the accurate clock support
* were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
* They were originally developed for SUN and DEC kernels.
* All the kudos should go to Dave for this stuff.
*/
void second_overflow(void)
{
long time_adj;
/* Bump the maxerror field */
time_maxerror += MAXFREQ >> SHIFT_USEC;
if (time_maxerror > NTP_PHASE_LIMIT) {
time_maxerror = NTP_PHASE_LIMIT;
time_status |= STA_UNSYNC;
}
/*
* Leap second processing. If in leap-insert state at the end of the
* day, the system clock is set back one second; if in leap-delete
* state, the system clock is set ahead one second. The microtime()
* routine or external clock driver will insure that reported time is
* always monotonic. The ugly divides should be replaced.
*/
switch (time_state) {
case TIME_OK:
if (time_status & STA_INS)
time_state = TIME_INS;
else if (time_status & STA_DEL)
time_state = TIME_DEL;
break;
case TIME_INS:
if (xtime.tv_sec % 86400 == 0) {
xtime.tv_sec--;
wall_to_monotonic.tv_sec++;
/*
* The timer interpolator will make time change
* gradually instead of an immediate jump by one second
*/
time_interpolator_update(-NSEC_PER_SEC);
time_state = TIME_OOP;
clock_was_set();
printk(KERN_NOTICE "Clock: inserting leap second "
"23:59:60 UTC\n");
}
break;
case TIME_DEL:
if ((xtime.tv_sec + 1) % 86400 == 0) {
xtime.tv_sec++;
wall_to_monotonic.tv_sec--;
/*
* Use of time interpolator for a gradual change of
* time
*/
time_interpolator_update(NSEC_PER_SEC);
time_state = TIME_WAIT;
clock_was_set();
printk(KERN_NOTICE "Clock: deleting leap second "
"23:59:59 UTC\n");
}
break;
case TIME_OOP:
time_state = TIME_WAIT;
break;
case TIME_WAIT:
if (!(time_status & (STA_INS | STA_DEL)))
time_state = TIME_OK;
}
/*
* Compute the phase adjustment for the next second. The offset is
* reduced by a fixed factor times the time constant.
*/
tick_length = tick_length_base;
time_adj = shift_right(time_offset, SHIFT_PLL + time_constant);
time_offset -= time_adj;
tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
if (unlikely(time_adjust)) {
if (time_adjust > MAX_TICKADJ) {
time_adjust -= MAX_TICKADJ;
tick_length += MAX_TICKADJ_SCALED;
} else if (time_adjust < -MAX_TICKADJ) {
time_adjust += MAX_TICKADJ;
tick_length -= MAX_TICKADJ_SCALED;
} else {
time_adjust = 0;
tick_length += (s64)(time_adjust * NSEC_PER_USEC /
HZ) << TICK_LENGTH_SHIFT;
}
}
}
/*
* Return how long ticks are at the moment, that is, how much time
* update_wall_time_one_tick will add to xtime next time we call it
* (assuming no calls to do_adjtimex in the meantime).
* The return value is in fixed-point nanoseconds shifted by the
* specified number of bits to the right of the binary point.
* This function has no side-effects.
*/
u64 current_tick_length(void)
{
return tick_length;
}
void __attribute__ ((weak)) notify_arch_cmos_timer(void)
{
return;
}
/* adjtimex mainly allows reading (and writing, if superuser) of
* kernel time-keeping variables. used by xntpd.
*/
int do_adjtimex(struct timex *txc)
{
long ltemp, mtemp, save_adjust;
s64 freq_adj, temp64;
int result;
/* In order to modify anything, you gotta be super-user! */
if (txc->modes && !capable(CAP_SYS_TIME))
return -EPERM;
/* Now we validate the data before disabling interrupts */
if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
/* singleshot must not be used with any other mode bits */
if (txc->modes != ADJ_OFFSET_SINGLESHOT)
return -EINVAL;
if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
/* adjustment Offset limited to +- .512 seconds */
if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
return -EINVAL;
/* if the quartz is off by more than 10% something is VERY wrong ! */
if (txc->modes & ADJ_TICK)
if (txc->tick < 900000/USER_HZ ||
txc->tick > 1100000/USER_HZ)
return -EINVAL;
write_seqlock_irq(&xtime_lock);
result = time_state; /* mostly `TIME_OK' */
/* Save for later - semantics of adjtime is to return old value */
save_adjust = time_adjust;
#if 0 /* STA_CLOCKERR is never set yet */
time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
#endif
/* If there are input parameters, then process them */
if (txc->modes)
{
if (txc->modes & ADJ_STATUS) /* only set allowed bits */
time_status = (txc->status & ~STA_RONLY) |
(time_status & STA_RONLY);
if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */
if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
result = -EINVAL;
goto leave;
}
time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC);
}
if (txc->modes & ADJ_MAXERROR) {
if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
result = -EINVAL;
goto leave;
}
time_maxerror = txc->maxerror;
}
if (txc->modes & ADJ_ESTERROR) {
if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
result = -EINVAL;
goto leave;
}
time_esterror = txc->esterror;
}
if (txc->modes & ADJ_TIMECONST) { /* p. 24 */
if (txc->constant < 0) { /* NTP v4 uses values > 6 */
result = -EINVAL;
goto leave;
}
time_constant = min(txc->constant + 4, (long)MAXTC);
}
if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
/* adjtime() is independent from ntp_adjtime() */
time_adjust = txc->offset;
}
else if (time_status & STA_PLL) {
ltemp = txc->offset * NSEC_PER_USEC;
/*
* Scale the phase adjustment and
* clamp to the operating range.
*/
time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC);
time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC);
/*
* Select whether the frequency is to be controlled
* and in which mode (PLL or FLL). Clamp to the operating
* range. Ugly multiply/divide should be replaced someday.
*/
if (time_status & STA_FREQHOLD || time_reftime == 0)
time_reftime = xtime.tv_sec;
mtemp = xtime.tv_sec - time_reftime;
time_reftime = xtime.tv_sec;
freq_adj = (s64)time_offset * mtemp;
freq_adj = shift_right(freq_adj, time_constant * 2 +
(SHIFT_PLL + 2) * 2 - SHIFT_NSEC);
if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
temp64 = (s64)time_offset << (SHIFT_NSEC - SHIFT_FLL);
if (time_offset < 0) {
temp64 = -temp64;
do_div(temp64, mtemp);
freq_adj -= temp64;
} else {
do_div(temp64, mtemp);
freq_adj += temp64;
}
}
freq_adj += time_freq;
freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
time_offset = (time_offset / HZ) << SHIFT_UPDATE;
} /* STA_PLL */
} /* txc->modes & ADJ_OFFSET */
if (txc->modes & ADJ_TICK)
tick_usec = txc->tick;
if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
ntp_update_frequency();
} /* txc->modes */
leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
result = TIME_ERROR;
if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
txc->offset = save_adjust;
else
txc->offset = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000;
txc->freq = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC);
txc->maxerror = time_maxerror;
txc->esterror = time_esterror;
txc->status = time_status;
txc->constant = time_constant;
txc->precision = 1;
txc->tolerance = MAXFREQ;
txc->tick = tick_usec;
/* PPS is not implemented, so these are zero */
txc->ppsfreq = 0;
txc->jitter = 0;
txc->shift = 0;
txc->stabil = 0;
txc->jitcnt = 0;
txc->calcnt = 0;
txc->errcnt = 0;
txc->stbcnt = 0;
write_sequnlock_irq(&xtime_lock);
do_gettimeofday(&txc->time);
notify_arch_cmos_timer();
return(result);
}
