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 <[email protected]>
---
include/linux/timex.h | 2 ++
kernel/time/ntp.c | 36 ++++++++++++++++++++++--------------
2 files changed, 24 insertions(+), 14 deletions(-)
Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h
+++ linux-2.6-mm/include/linux/timex.h
@@ -92,10 +92,12 @@
#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 */
Index: linux-2.6-mm/kernel/time/ntp.c
===================================================================
--- linux-2.6-mm.orig/kernel/time/ntp.c
+++ linux-2.6-mm/kernel/time/ntp.c
@@ -72,7 +72,7 @@ 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);
@@ -206,6 +206,7 @@ void __attribute__ ((weak)) notify_arch_
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! */
@@ -251,7 +252,7 @@ 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) {
@@ -284,14 +285,14 @@ 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
@@ -303,24 +304,31 @@ 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)
@@ -336,7 +344,7 @@ leave: if ((time_status & (STA_UNSYNC|ST
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;
--
-
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