From 6545c8c3a26470349b7ca3564cf0ec033393aaa6 Mon Sep 17 00:00:00 2001
From: Andi Kleen <ak@suse.de>
Date: Sat, 29 Jul 2006 21:42:37 +0200
Subject: [PATCH] --- yaml --- r: 32891 b: refs/heads/master c:
 0e5f61b00c577da698fb00cd9c91a96b79044dfd h: refs/heads/master i:   32889:
 aeda4f47d5bddc6ee4c3a6b98a794530c3cdbe50   32887:
 44a0640f691e5b630042ad7276999e84e74c6b5a v: v3

---
 [refs]                          |  2 +-
 trunk/arch/x86_64/kernel/time.c | 16 ++++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/[refs] b/[refs]
index 65f2b0880aa0..4348f3d449d3 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 260f659b232b17889e3f0c9bf411675898b222c2
+refs/heads/master: 0e5f61b00c577da698fb00cd9c91a96b79044dfd
diff --git a/trunk/arch/x86_64/kernel/time.c b/trunk/arch/x86_64/kernel/time.c
index e0341c6808e5..7a9b18224182 100644
--- a/trunk/arch/x86_64/kernel/time.c
+++ b/trunk/arch/x86_64/kernel/time.c
@@ -28,6 +28,7 @@
 #include <linux/acpi.h>
 #ifdef CONFIG_ACPI
 #include <acpi/achware.h>	/* for PM timer frequency */
+#include <acpi/acpi_bus.h>
 #endif
 #include <asm/8253pit.h>
 #include <asm/pgtable.h>
@@ -953,11 +954,18 @@ __cpuinit int unsynchronized_tsc(void)
 #ifdef CONFIG_SMP
 	if (apic_is_clustered_box())
 		return 1;
- 	/* Intel systems are normally all synchronized. Exceptions
- 	   are handled in the check above. */
- 	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
- 		return 0;
 #endif
+	/* Most intel systems have synchronized TSCs except for
+	   multi node systems */
+ 	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
+#ifdef CONFIG_ACPI
+		/* But TSC doesn't tick in C3 so don't use it there */
+		if (acpi_fadt.length > 0 && acpi_fadt.plvl3_lat < 100)
+			return 1;
+#endif
+ 		return 0;
+	}
+
  	/* Assume multi socket systems are not synchronized */
  	return num_present_cpus() > 1;
 }