Index: arch/mips/kernel/time.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/kernel/time.c,v
retrieving revision 1.53
diff -u -r1.53 time.c
--- arch/mips/kernel/time.c	17 Apr 2003 22:55:51 -0000	1.53
+++ arch/mips/kernel/time.c	23 Apr 2003 01:01:39 -0000
@@ -148,23 +148,8 @@
 /* Cycle counter value at the previous timer interrupt.. */
 static unsigned int timerhi, timerlo;
 
-/* 
- * Cycle counter value after which next timer interrupt is considered "missed".
- * Suppose we are serving timer interrupt scheduled at time t, the theorectical 
- * expiriing point for next interrupt is t + 2 * cycles_per_jiffy.
- * In practice, we set it a little earlier, which is 
- * 	t + 2 * cycles_per_jiffy - EXTRA_CUSHION_CYCLES
- * just to make sure we still have some time to set registers after we
- * decide whether a timer interrupt is missed.
- */
-static unsigned int expirehi, expirelo;
-
-/* 
- * extra "cushion" cycles used when we decide whether we have missed an
- * timer interrupt (in the case of using cpu counter).  It should be long
- * enough to cover at least 20 instructions.
- */
-#define	EXTRA_CUSHION_CYCLES	200
+/* expirelo is the count value for next CPU timer interrupt */
+static unsigned int expirelo;
 
 /* last time when xtime and rtc are sync'ed up */
 static long last_rtc_update;
@@ -356,41 +341,26 @@
  * high-level timer interrupt service routines.  This function
  * is set as irqaction->handler and is invoked through do_IRQ.
  */
-static inline int 
-bit64_compare(unsigned hi1, unsigned lo1, unsigned hi2, unsigned lo2)
-{
-	if (hi1 == hi2) 
-		return lo1 - lo2;
-	else
-		return hi1 - hi2;
-}
-
 void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
 	if (cpu_has_counter) {
 		unsigned int count;
 
-		/*
-		 * The cycle counter is only 32 bit which is good for about
-		 * a minute at current count rates of upto 150MHz or so.
-		 */
+		/* ack timer interrupt, and try to set next interrupt */
+		expirelo += cycles_per_jiffy;
+		write_c0_compare(expirelo);
 		count = read_c0_count();
-		timerhi += count < timerlo;	/* Wrap around */
-		timerlo = count;
 
-		/* check to see if we have missed a timer interrupt */
-		if (bit64_compare(timerhi, timerlo, expirehi, expirelo) < 0) {
-			unsigned int old_expirelo=expirelo;
-			expirelo += cycles_per_jiffy;
-			expirehi += expirelo < old_expirelo;
-			write_c0_compare(old_expirelo + EXTRA_CUSHION_CYCLES);
-		} else {
-			// missed_timer_count ++;
-			/* we have missed at least one timer interrupt */
-			expirelo = timerlo + cycles_per_jiffy*2 - EXTRA_CUSHION_CYCLES;
-			expirehi = timerhi + (expirelo < timerlo);
-			write_c0_compare(timerlo + cycles_per_jiffy);
+		/* check to see if we have missed any timer interrupts */
+		if ((count - expirelo) < 0x7fffffff) {
+			/* missed_timer_count ++; */
+			expirelo = count + cycles_per_jiffy;
+			write_c0_compare(expirelo);
 		}
+
+		/* Update timerhi/timerlo for intra-jiffy calibration. */
+		timerhi += count < timerlo;	/* Wrap around */
+		timerlo = count;
 	}
 
 	/*
@@ -558,7 +528,7 @@
 		 */
 		write_c0_compare(cycles_per_jiffy);
 		write_c0_count(0);
-		expirelo = cycles_per_jiffy * 2 - EXTRA_CUSHION_CYCLES;
+		expirelo = cycles_per_jiffy;
 	}
 
 	/*
Index: arch/mips64/kernel/time.c
===================================================================
RCS file: /home/cvs/linux/arch/mips64/kernel/time.c,v
retrieving revision 1.16
diff -u -r1.16 time.c
--- arch/mips64/kernel/time.c	17 Apr 2003 22:55:51 -0000	1.16
+++ arch/mips64/kernel/time.c	23 Apr 2003 01:01:39 -0000
@@ -148,23 +148,8 @@
 /* Cycle counter value at the previous timer interrupt.. */
 static unsigned int timerhi, timerlo;
 
-/* 
- * Cycle counter value after which next timer interrupt is considered "missed".
- * Suppose we are serving timer interrupt scheduled at time t, the theorectical 
- * expiriing point for next interrupt is t + 2 * cycles_per_jiffy.
- * In practice, we set it a little earlier, which is 
- * 	t + 2 * cycles_per_jiffy - EXTRA_CUSHION_CYCLES
- * just to make sure we still have some time to set registers after we
- * decide whether a timer interrupt is missed.
- */
-static unsigned int expirehi, expirelo;
-
-/* 
- * extra "cushion" cycles used when we decide whether we have missed an
- * timer interrupt (in the case of using cpu counter).  It should be long
- * enough to cover at least 20 instructions.
- */
-#define	EXTRA_CUSHION_CYCLES	200
+/* expirelo is the count value for next CPU timer interrupt */
+static unsigned int expirelo;
 
 /* last time when xtime and rtc are sync'ed up */
 static long last_rtc_update;
@@ -356,41 +341,26 @@
  * high-level timer interrupt service routines.  This function
  * is set as irqaction->handler and is invoked through do_IRQ.
  */
-static inline int 
-bit64_compare(unsigned hi1, unsigned lo1, unsigned hi2, unsigned lo2)
-{
-	if (hi1 == hi2) 
-		return lo1 - lo2;
-	else 
-		return hi1 - hi2;
-}
-
 void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
 	if (cpu_has_counter) {
 		unsigned int count;
 
-		/*
-		 * The cycle counter is only 32 bit which is good for about
-		 * a minute at current count rates of upto 150MHz or so.
-		 */
+		/* ack timer interrupt, and try to set next interrupt */
+		expirelo += cycles_per_jiffy;
+		write_c0_compare(expirelo);
 		count = read_c0_count();
-		timerhi += count < timerlo;	/* Wrap around */
-		timerlo = count;
 
-		/* check to see if we have missed a timer interrupt */
-		if (bit64_compare(timerhi, timerlo, expirehi, expirelo) < 0) {
-			unsigned int old_expirelo=expirelo;
-			expirelo += cycles_per_jiffy;
-			expirehi += expirelo < old_expirelo;
-			write_c0_compare(old_expirelo + EXTRA_CUSHION_CYCLES);
-		} else {
-			// missed_timer_count ++;
-			/* we have missed at least one timer interrupt */
-			expirelo = timerlo + cycles_per_jiffy*2 - EXTRA_CUSHION_CYCLES;
-			expirehi = timerhi + (expirelo < timerlo);
-			write_c0_compare(timerlo + cycles_per_jiffy);
+		/* check to see if we have missed any timer interrupts */
+		if ((count - expirelo) < 0x7fffffff) {
+			/* missed_timer_count ++; */
+			expirelo = count + cycles_per_jiffy;
+			write_c0_compare(expirelo);
 		}
+
+		/* Update timerhi/timerlo for intra-jiffy calibration. */
+		timerhi += count < timerlo;	/* Wrap around */
+		timerlo = count;
 	}
 
 	/*
@@ -558,7 +528,7 @@
 		 */
 		write_c0_compare(cycles_per_jiffy);
 		write_c0_count(0);
-		expirelo = cycles_per_jiffy * 2 - EXTRA_CUSHION_CYCLES;
+		expirelo = cycles_per_jiffy;
 	}
 
 	/*