[PATCH] hpet-RTC: fix timer config register accesses

Make sure that the RTC timer is in non-periodic mode; some stupid BIOS might
have initialized it to periodic mode.

Furthermore, don't set the SETVAL bit in the config register.  This wouldn't
have any effect unless the timer was in period mode (which it isn't), and then
the actual timer frequency would be half that of the desired one because
incrementing the comparator in the interrupt handler would be done after the
hardware has already incremented it itself.
Signed-off-by: NClemens Ladisch <clemens@ladisch.de>
Acked-by: NVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/time_hpet.c

@@ -309,7 +309,8 @@ int hpet_rtc_timer_init(void)
 	local_irq_restore(flags);
 
 	cfg = hpet_readl(HPET_T1_CFG);
-	cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT;
+	cfg &= ~HPET_TN_PERIODIC;
+	cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
 	hpet_writel(cfg, HPET_T1_CFG);
 
 	return 1;
@@ -335,12 +336,6 @@ static void hpet_rtc_timer_reinit(void)
 	cnt = hpet_readl(HPET_T1_CMP);
 	cnt += hpet_tick*HZ/hpet_rtc_int_freq;
 	hpet_writel(cnt, HPET_T1_CMP);
-
-	cfg = hpet_readl(HPET_T1_CFG);
-	cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT;
-	hpet_writel(cfg, HPET_T1_CFG);
-
-	return;
 }
 
 /*

arch/x86_64/kernel/time.c

@@ -1128,7 +1128,8 @@ int hpet_rtc_timer_init(void)
 	local_irq_restore(flags);
 
 	cfg = hpet_readl(HPET_T1_CFG);
-	cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT;
+	cfg &= ~HPET_TN_PERIODIC;
+	cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
 	hpet_writel(cfg, HPET_T1_CFG);
 
 	return 1;
@@ -1154,12 +1155,6 @@ static void hpet_rtc_timer_reinit(void)
 	cnt = hpet_readl(HPET_T1_CMP);
 	cnt += hpet_tick*HZ/hpet_rtc_int_freq;
 	hpet_writel(cnt, HPET_T1_CMP);
-
-	cfg = hpet_readl(HPET_T1_CFG);
-	cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT;
-	hpet_writel(cfg, HPET_T1_CFG);
-
-	return;
 }
 
 /*