From 3d3675cc3d04d7fd4bb11e8c1ea79e5ade4f5e44 Mon Sep 17 00:00:00 2001 From: Roman Zippel Date: Sat, 30 Sep 2006 23:28:25 -0700 Subject: [PATCH] [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 Cc: john stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/timex.h | 2 +- kernel/time/ntp.c | 64 +++++++++++-------------------------------- 2 files changed, 17 insertions(+), 49 deletions(-) diff --git a/include/linux/timex.h b/include/linux/timex.h index b589c8218bb9..1cde6f6a2712 100644 --- a/include/linux/timex.h +++ b/include/linux/timex.h @@ -89,7 +89,7 @@ * FINENSEC is 1 ns in SHIFT_UPDATE units of the time_phase variable. */ #define SHIFT_SCALE 22 /* phase scale (shift) */ -#define SHIFT_UPDATE (SHIFT_KG + MAXTC) /* time offset scale (shift) */ +#define SHIFT_UPDATE (SHIFT_HZ + 1) /* time offset scale (shift) */ #define SHIFT_USEC 16 /* frequency offset scale (shift) */ #define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */ 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; -- 2.20.1