diff options
Diffstat (limited to 'arch/x86_64/kernel/time.c')
| -rw-r--r-- | arch/x86_64/kernel/time.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index e0341c6808e..7a9b1822418 100644 --- a/arch/x86_64/kernel/time.c +++ b/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; } |