From: Luming Yu <luyu@redhat.com>
Date: Fri, 20 Aug 2010 06:29:00 -0400
Subject: [x86_64] use apic as main timer if non-stop-apic timer
Message-id: <4C6E20AC.2050902@redhat.com>
Patchwork-id: 27728
O-Subject: [RHEL 5.6 PATCH 2/3] bz 573514: use apic timer as main timer for
	system with non-stop-apic timer
Bugzilla: 573514
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>
RH-Acked-by: Stefan Assmann <sassmann@redhat.com>

Bugzilla #573514

Description of problem:

It is useful to kill interrupt 0 to make the system more idle by
shutting down a interrupt source,which wakes up CPU0 every 1ms, to save
some power on systems like WSM-EX with non-stop APIC timer feature.

Upstream status:

Upstream don't need this. So no upstream.

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/arch/x86_64/kernel/apic.c b/arch/x86_64/kernel/apic.c
index 7f08ec4..9a0b86a 100644
--- a/arch/x86_64/kernel/apic.c
+++ b/arch/x86_64/kernel/apic.c
@@ -756,7 +756,7 @@ static void setup_APIC_timer(unsigned int clocks)
 	/* Turn off PIT interrupt if we use APIC timer as main timer.
 	   Only works with the PM timer right now
 	   TBD fix it for HPET too. */
-	if (vxtime.mode == VXTIME_PMTMR &&
+	if ((vxtime.mode == VXTIME_PMTMR || boot_cpu_has(X86_FEATURE_ARAT)) &&
 		smp_processor_id() == boot_cpu_id &&
 		apic_runs_main_timer == 1 &&
 		!cpu_isset(boot_cpu_id, timer_interrupt_broadcast_ipi_mask)) {
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 830c7d6..11dce35 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -1429,6 +1429,13 @@ void __init time_init(void)
 		tick_nsec = SH_DIV(NSEC_PER_SEC, acthz, 8) / tick_divider;
 	}
 
+	if ((apic_runs_main_timer == 0) && (nohpet == 0) &&
+	    boot_cpu_has(X86_FEATURE_ARAT)) {
+		/* apic timer as main timer */
+		nohpet = 1;
+		apic_runs_main_timer = 1;
+	}
+
 	if (nohpet)
 		vxtime.hpet_address = 0;