[PATCH] hpet-RTC: disable interrupt when no longer needed

When the emulated RTC interrupt is no longer needed, we better disable it;
otherwise, we get a spurious interrupt whenever the timer has rolled over and
reaches the same comparator value.

Having a superfluous interrupt every five minutes doesn't hurt much, but it's
bad style anyway.  ;-)
Signed-off-by: NClemens Ladisch <clemens@ladisch.de>
Acked-by: N"Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/time_hpet.c

@@ -319,8 +319,12 @@ static void hpet_rtc_timer_reinit(void)
 {
 	unsigned int cfg, cnt;
 
-	if (!(PIE_on | AIE_on | UIE_on))
+	if (unlikely(!(PIE_on | AIE_on | UIE_on))) {
+		cfg = hpet_readl(HPET_T1_CFG);
+		cfg &= ~HPET_TN_ENABLE;
+		hpet_writel(cfg, HPET_T1_CFG);
 		return;
+	}
 
 	if (PIE_on && (PIE_freq > DEFAULT_RTC_INT_FREQ))
 		hpet_rtc_int_freq = PIE_freq;

arch/x86_64/kernel/time.c

@@ -1138,8 +1138,12 @@ static void hpet_rtc_timer_reinit(void)
 {
 	unsigned int cfg, cnt;
 
-	if (!(PIE_on | AIE_on | UIE_on))
+	if (unlikely(!(PIE_on | AIE_on | UIE_on))) {
+		cfg = hpet_readl(HPET_T1_CFG);
+		cfg &= ~HPET_TN_ENABLE;
+		hpet_writel(cfg, HPET_T1_CFG);
 		return;
+	}
 
 	if (PIE_on && (PIE_freq > DEFAULT_RTC_INT_FREQ))
 		hpet_rtc_int_freq = PIE_freq;