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[PATCH] ntp: convert time_freq to nsec value

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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>
This commit is contained in:
Roman Zippel 2006-09-30 23:28:27 -07:00 committed by Linus Torvalds
parent 97eebe138c
commit 04b617e71e
2 changed files with 24 additions and 14 deletions
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2
include/linux/timex.h
View file

@ -91,10 +91,12 @@
#define SHIFT_SCALE 22 /* phase scale (shift) */
#define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */
#define SHIFT_USEC 16 /* frequency offset scale (shift) */
#define SHIFT_NSEC 12 /* kernel frequency offset scale */
#define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
#define MAXPHASE 512000L /* max phase error (us) */
#define MAXFREQ (512L << SHIFT_USEC) /* max frequency error (ppm) */
#define MAXFREQ_NSEC (512000L << SHIFT_NSEC) /* max frequency error (ppb) */
#define MINSEC 16L /* min interval between updates (s) */
#define MAXSEC 1200L /* max interval between updates (s) */
#define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */

36
kernel/time/ntp.c
View file

@ -66,7 +66,7 @@ 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 * NSEC_PER_USEC) << (TICK_LENGTH_SHIFT - SHIFT_USEC);
tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
do_div(tick_length_base, HZ);
@ -200,6 +200,7 @@ void __attribute__ ((weak)) notify_arch_cmos_timer(void)
int do_adjtimex(struct timex *txc)
{
long ltemp, mtemp, save_adjust;
s64 freq_adj;
int result;
/* In order to modify anything, you gotta be super-user! */
@ -245,7 +246,7 @@ int do_adjtimex(struct timex *txc)
result = -EINVAL;
goto leave;
}
time_freq = txc->freq;
time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC);
}
if (txc->modes & ADJ_MAXERROR) {
@ -278,14 +279,14 @@ int do_adjtimex(struct timex *txc)
time_adjust = txc->offset;
}
else if (time_status & STA_PLL) {
ltemp = txc->offset;
ltemp = txc->offset * NSEC_PER_USEC;
/*
* Scale the phase adjustment and
* clamp to the operating range.
*/
time_offset = min(ltemp, MAXPHASE);
time_offset = max(time_offset, -MAXPHASE);
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
@ -297,24 +298,31 @@ int do_adjtimex(struct timex *txc)
time_reftime = xtime.tv_sec;
mtemp = xtime.tv_sec - time_reftime;
time_reftime = xtime.tv_sec;
freq_adj = 0;
if (time_status & STA_FLL) {
if (mtemp >= MINSEC) {
ltemp = ((time_offset << 12) / mtemp) << (SHIFT_USEC - 12);
time_freq += shift_right(ltemp, SHIFT_KH);
freq_adj = (s64)time_offset << (SHIFT_NSEC - SHIFT_KH);
if (time_offset < 0) {
freq_adj = -freq_adj;
do_div(freq_adj, mtemp);
freq_adj = -freq_adj;
} else
do_div(freq_adj, mtemp);
} else /* calibration interval too short (p. 12) */
result = TIME_ERROR;
} else { /* PLL mode */
if (mtemp < MAXSEC) {
ltemp *= mtemp;
time_freq += shift_right(ltemp,(time_constant +
freq_adj = (s64)ltemp * mtemp;
freq_adj = shift_right(freq_adj,(time_constant +
time_constant +
SHIFT_KF - SHIFT_USEC));
SHIFT_KF - SHIFT_NSEC));
} else /* calibration interval too long (p. 12) */
result = TIME_ERROR;
}
time_freq = min(time_freq, MAXFREQ);
time_freq = max(time_freq, -MAXFREQ);
time_offset = (time_offset * NSEC_PER_USEC / HZ) << SHIFT_UPDATE;
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)
@ -330,7 +338,7 @@ leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
txc->offset = save_adjust;
else
txc->offset = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000;
txc->freq = time_freq;
txc->freq = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC);
txc->maxerror = time_maxerror;
txc->esterror = time_esterror;
txc->status = time_status;