[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>

kernel/timer.c

diff --git a/kernel/timer.c b/kernel/timer.c
index 5fccc7c..78d3fa1 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -562,12 +562,6 @@
 
 /******************************************************************/
 
-/*
- * 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 @@
 	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);
 }