From db954b5898dd3ef3ef93f4144158ea8f97deb058 Mon Sep 17 00:00:00 2001 From: Venkatesh Pallipadi Date: Mon, 6 Apr 2009 18:51:29 -0700 Subject: x86 ACPI: Add support for Always Running APIC timer Add support for Always Running APIC timer, CPUID_0x6_EAX_Bit2. This bit means the APIC timer continues to run even when CPU is in deep C-states. The advantage is that we can use LAPIC timer on these CPUs always, and there is no need for "slow to read and program" external timers (HPET/PIT) and the timer broadcast logic and related code in C-state entry and exit. Signed-off-by: Venkatesh Pallipadi Acked-by: H. Peter Anvin Signed-off-by: Len Brown --- arch/x86/include/asm/cpufeature.h | 1 + arch/x86/kernel/apic/apic.c | 6 ++++++ arch/x86/kernel/cpu/addon_cpuid_features.c | 1 + 3 files changed, 8 insertions(+) (limited to 'arch/x86') diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 0beba0d1468d..bb83b1c397aa 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -154,6 +154,7 @@ * CPUID levels like 0x6, 0xA etc */ #define X86_FEATURE_IDA (7*32+ 0) /* Intel Dynamic Acceleration */ +#define X86_FEATURE_ARAT (7*32+ 1) /* Always Running APIC Timer */ /* Virtualization flags: Linux defined */ #define X86_FEATURE_TPR_SHADOW (8*32+ 0) /* Intel TPR Shadow */ diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 098ec84b8c00..f2870920f246 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -431,6 +431,12 @@ static void __cpuinit setup_APIC_timer(void) { struct clock_event_device *levt = &__get_cpu_var(lapic_events); + if (cpu_has(¤t_cpu_data, X86_FEATURE_ARAT)) { + lapic_clockevent.features &= ~CLOCK_EVT_FEAT_C3STOP; + /* Make LAPIC timer preferrable over percpu HPET */ + lapic_clockevent.rating = 150; + } + memcpy(levt, &lapic_clockevent, sizeof(*levt)); levt->cpumask = cpumask_of(smp_processor_id()); diff --git a/arch/x86/kernel/cpu/addon_cpuid_features.c b/arch/x86/kernel/cpu/addon_cpuid_features.c index 8220ae69849d..c965e5212714 100644 --- a/arch/x86/kernel/cpu/addon_cpuid_features.c +++ b/arch/x86/kernel/cpu/addon_cpuid_features.c @@ -31,6 +31,7 @@ void __cpuinit init_scattered_cpuid_features(struct cpuinfo_x86 *c) static const struct cpuid_bit __cpuinitconst cpuid_bits[] = { { X86_FEATURE_IDA, CR_EAX, 1, 0x00000006 }, + { X86_FEATURE_ARAT, CR_EAX, 2, 0x00000006 }, { 0, 0, 0, 0 } }; -- cgit v1.2.3