[PATCH 3/10] NTP: add ntp_update_frequency

[Roman Zippel]

This introduces ntp_update_frequency and deinlines ntp_clear() (as it's
not performance critical).
It also changes how tick_nsec is calculated from tick_usec, instead of
scaling it using TICK_USEC_TO_NSEC it's simply shifted by the difference.
Since ntp doesn't change the tick value, the result in practice is the
same, but it's easier to change this into a clock parameter, which can
be calculated during boot.



Signed-off-by: Roman Zippel <zippel@xxxxxxxxxxxxxx>

---

 include/linux/timex.h |   14 ++------------
 kernel/time.c         |    7 ++++---
 kernel/timer.c        |   28 ++++++++++++++++++++++++++--
 3 files changed, 32 insertions(+), 17 deletions(-)

Index: linux-2.6-mm/include/linux/timex.h
===================================================================
--- linux-2.6-mm.orig/include/linux/timex.h	2005-12-21 12:11:56.000000000 +0100
+++ linux-2.6-mm/include/linux/timex.h	2005-12-21 12:12:00.000000000 +0100
@@ -219,18 +219,8 @@ extern long time_reftime;	/* time at las
 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
Index: linux-2.6-mm/kernel/time.c
===================================================================
--- linux-2.6-mm.orig/kernel/time.c	2005-12-21 12:11:48.000000000 +0100
+++ linux-2.6-mm/kernel/time.c	2005-12-21 12:12:00.000000000 +0100
@@ -334,10 +334,11 @@ 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;
Index: linux-2.6-mm/kernel/timer.c
===================================================================
--- linux-2.6-mm.orig/kernel/timer.c	2005-12-21 12:11:56.000000000 +0100
+++ linux-2.6-mm/kernel/timer.c	2005-12-21 12:12:00.000000000 +0100
@@ -551,8 +551,8 @@ found:
  * Timekeeping variables
  */
 unsigned long tick_usec = TICK_USEC; 		/* USER_HZ period (usec) */
-unsigned long tick_nsec = TICK_NSEC;		/* ACTHZ period (nsec) */
-static unsigned long tick_nsec_curr = TICK_NSEC;
+unsigned long tick_nsec;			/* ACTHZ period (nsec) */
+static unsigned long tick_nsec_curr;
 
 /* 
  * The current time 
@@ -591,6 +591,29 @@ long time_reftime;			/* time at last adj
 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_nsec_curr = tick_nsec;
+}
+
+void ntp_update_frequency(void)
+{
+	tick_nsec = tick_usec * 1000;
+	tick_nsec -= NSEC_PER_SEC / HZ - TICK_NSEC;
+}
+
 /*
  * this routine handles the overflow of the microsecond field
  *
@@ -1348,6 +1371,7 @@ static struct notifier_block __devinitda
 
 void __init init_timers(void)
 {
+	ntp_clear();
 	timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
 				(void *)(long)smp_processor_id());
 	register_cpu_notifier(&timers_nb);
-
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