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authorRoman Zippel <zippel@linux-m68k.org>2006-09-30 23:28:22 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-01 00:39:26 -0700
commitb0ee75561beadc4db4d9a899c8ef4a7db50aa0ab (patch)
treee50354c74ce17f6ea78dc1d7fac608788de517f3 /kernel/time
parent4c7ee8de956fc250fe31e2fa91f6da980fabe317 (diff)
[PATCH] ntp: add ntp_update_frequency
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>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/ntp.c50
1 files changed, 44 insertions, 6 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 8ccce15b4b2..77137bec2ae 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -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;