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authorRoman Zippel <zippel@linux-m68k.org>2006-09-30 23:28:25 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-01 00:39:26 -0700
commit3d3675cc3d04d7fd4bb11e8c1ea79e5ade4f5e44 (patch)
tree7beeef2896cb92e06b0a2ee8fa62b17f1732b72b /kernel
parentdc6a43e46f1b6de22701f97bec022e97088cfa90 (diff)
[PATCH] ntp: prescale time_offset
This converts time_offset into a scaled per tick value. This avoids now completely the crude compensation in second_overflow(). 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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/ntp.c64
1 files changed, 16 insertions, 48 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index ab21eb06e09b..238ce47ef09d 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -31,7 +31,7 @@ int tickadj = 500/HZ ? : 1; /* microsecs */
/* TIME_ERROR prevents overwriting the CMOS clock */
int time_state = TIME_OK; /* clock synchronization status */
int time_status = STA_UNSYNC; /* clock status bits */
-long time_offset; /* time adjustment (us) */
+long time_offset; /* time adjustment (ns) */
long time_constant = 2; /* pll time constant */
long time_tolerance = MAXFREQ; /* frequency tolerance (ppm) */
long time_precision = 1; /* clock precision (us) */
@@ -57,6 +57,7 @@ void ntp_clear(void)
ntp_update_frequency();
tick_length = tick_length_base;
+ time_offset = 0;
}
#define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE)
@@ -83,7 +84,7 @@ void ntp_update_frequency(void)
*/
void second_overflow(void)
{
- long ltemp, time_adj;
+ long time_adj;
/* Bump the maxerror field */
time_maxerror += time_tolerance >> SHIFT_USEC;
@@ -151,42 +152,14 @@ void second_overflow(void)
* adjustment for each second is clamped so as to spread the adjustment
* over not more than the number of seconds between updates.
*/
- ltemp = time_offset;
- if (!(time_status & STA_FLL))
- ltemp = shift_right(ltemp, SHIFT_KG + time_constant);
- ltemp = min(ltemp, (MAXPHASE / MINSEC) << SHIFT_UPDATE);
- ltemp = max(ltemp, -(MAXPHASE / MINSEC) << SHIFT_UPDATE);
- time_offset -= ltemp;
- time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
-
- /*
- * Compute the frequency estimate and additional phase adjustment due
- * to frequency error for the next second.
- */
-
-#if HZ == 100
- /*
- * Compensate for (HZ==100) != (1 << SHIFT_HZ). Add 25% and 3.125% to
- * get 128.125; => only 0.125% error (p. 14)
- */
- time_adj += shift_right(time_adj, 2) + shift_right(time_adj, 5);
-#endif
-#if HZ == 250
- /*
- * Compensate for (HZ==250) != (1 << SHIFT_HZ). Add 1.5625% and
- * 0.78125% to get 255.85938; => only 0.05% error (p. 14)
- */
- time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
-#endif
-#if HZ == 1000
- /*
- * Compensate for (HZ==1000) != (1 << SHIFT_HZ). Add 1.5625% and
- * 0.78125% to get 1023.4375; => only 0.05% error (p. 14)
- */
- time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
-#endif
tick_length = tick_length_base;
- tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10));
+ time_adj = time_offset;
+ if (!(time_status & STA_FLL))
+ time_adj = shift_right(time_adj, SHIFT_KG + time_constant);
+ time_adj = min(time_adj, -((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
+ time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
+ time_offset -= time_adj;
+ tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
}
/*
@@ -347,12 +320,8 @@ int do_adjtimex(struct timex *txc)
* Scale the phase adjustment and
* clamp to the operating range.
*/
- if (ltemp > MAXPHASE)
- time_offset = MAXPHASE << SHIFT_UPDATE;
- else if (ltemp < -MAXPHASE)
- time_offset = -(MAXPHASE << SHIFT_UPDATE);
- else
- time_offset = ltemp << SHIFT_UPDATE;
+ time_offset = min(ltemp, MAXPHASE);
+ time_offset = max(time_offset, -MAXPHASE);
/*
* Select whether the frequency is to be controlled
@@ -366,8 +335,7 @@ int do_adjtimex(struct timex *txc)
time_reftime = xtime.tv_sec;
if (time_status & STA_FLL) {
if (mtemp >= MINSEC) {
- ltemp = (time_offset / mtemp) << (SHIFT_USEC -
- SHIFT_UPDATE);
+ ltemp = ((time_offset << 12) / mtemp) << (SHIFT_USEC - 12);
time_freq += shift_right(ltemp, SHIFT_KH);
} else /* calibration interval too short (p. 12) */
result = TIME_ERROR;
@@ -382,6 +350,7 @@ int do_adjtimex(struct timex *txc)
}
time_freq = min(time_freq, time_tolerance);
time_freq = max(time_freq, -time_tolerance);
+ time_offset = (time_offset * NSEC_PER_USEC / HZ) << SHIFT_UPDATE;
} /* STA_PLL */
} /* txc->modes & ADJ_OFFSET */
if (txc->modes & ADJ_TICK)
@@ -395,9 +364,8 @@ leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
txc->offset = save_adjust;
- else {
- txc->offset = shift_right(time_offset, SHIFT_UPDATE);
- }
+ else
+ txc->offset = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000;
txc->freq = time_freq;
txc->maxerror = time_maxerror;
txc->esterror = time_esterror;

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