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[PATCH] ntp: add ntp_update_frequency

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This introduces ntp_update_frequency() and deinlines ntp_clear() (as it's not
performance critical).  ntp_update_frequency() calculates the base tick length
using tick_usec and adds a base adjustment, in case the frequency doesn't
divide evenly by HZ.

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 23:28:22 -07:00 committed by Linus Torvalds
parent 4c7ee8de95
commit b0ee75561b
3 changed files with 50 additions and 25 deletions
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14
include/linux/timex.h
View File

@ -219,18 +219,8 @@ extern long time_reftime; /* time at last adjustment (s) */
extern long time_adjust; /* The amount of adjtime left */
extern long time_next_adjust; /* Value for time_adjust at next tick */
/**
* ntp_clear - Clears the NTP state variables
*
* Must be called while holding a write on the xtime_lock
*/
static inline void ntp_clear(void)
{
time_adjust = 0; /* stop active adjtime() */
time_status |= STA_UNSYNC;
time_maxerror = NTP_PHASE_LIMIT;
time_esterror = NTP_PHASE_LIMIT;
}
extern void ntp_clear(void);
extern void ntp_update_frequency(void);
/**
* ntp_synced - Returns 1 if the NTP status is not UNSYNC

50
kernel/time/ntp.c
View File

@ -15,6 +15,13 @@
#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;
/* Don't completely fail for HZ > 500. */
int tickadj = 500/HZ ? : 1; /* microsecs */
@ -37,6 +44,36 @@ long time_reftime; /* time at last adjustment (s) */
long time_adjust;
long time_next_adjust;
/**
* 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;
}
#define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE)
#define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / (s64)CLOCK_TICK_RATE)
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;
do_div(tick_length_base, HZ);
tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT;
}
/*
* this routine handles the overflow of the microsecond field
*
@ -151,6 +188,7 @@ void second_overflow(void)
*/
time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
#endif
tick_length = tick_length_base;
}
/*
@ -204,14 +242,13 @@ void update_ntp_one_tick(void)
*/
u64 current_tick_length(void)
{
long delta_nsec;
u64 ret;
/* calculate the finest interval NTP will allow.
* ie: nanosecond value shifted by (SHIFT_SCALE - 10)
*/
delta_nsec = tick_nsec + adjtime_adjustment() * 1000;
ret = (u64)delta_nsec << TICK_LENGTH_SHIFT;
ret = tick_length;
ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT;
ret += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10));
return ret;
@ -351,10 +388,11 @@ int do_adjtimex(struct timex *txc)
time_freq = max(time_freq, -time_tolerance);
} /* STA_PLL */
} /* txc->modes & ADJ_OFFSET */
if (txc->modes & ADJ_TICK) {
if (txc->modes & ADJ_TICK)
tick_usec = txc->tick;
tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
}
if (txc->modes & ADJ_TICK)
ntp_update_frequency();
} /* txc->modes */
leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
result = TIME_ERROR;

11
kernel/timer.c
View File

@ -562,12 +562,6 @@ found:
/******************************************************************/
/*
* Timekeeping variables
*/
unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */
unsigned long tick_nsec = TICK_NSEC; /* ACTHZ period (nsec) */
/*
* The current time
* wall_to_monotonic is what we need to add to xtime (or xtime corrected
@ -757,10 +751,13 @@ void __init timekeeping_init(void)
unsigned long flags;
write_seqlock_irqsave(&xtime_lock, flags);
ntp_clear();
clock = clocksource_get_next();
clocksource_calculate_interval(clock, tick_nsec);
clock->cycle_last = clocksource_read(clock);
ntp_clear();
write_sequnlock_irqrestore(&xtime_lock, flags);
}