From: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
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 <venkatesh.pallipadi@xxxxxxxxx>
Acked-by: H. Peter Anvin <hpa@xxxxxxxxx>
Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
---
arch/x86/include/asm/cpufeature.h | 1 +
arch/x86/kernel/apic/apic.c | 6 ++++++
arch/x86/kernel/cpu/addon_cpuid_features.c | 1 +
drivers/acpi/processor_idle.c | 3 +++
4 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 0beba0d..bb83b1c 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 098ec84..f287092 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 8220ae6..c965e52 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 }
};
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 4e6e758..6fe1214 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -145,6 +145,9 @@ static void acpi_timer_check_state(int state, struct acpi_processor *pr,
struct acpi_processor_power *pwr = &pr->power;
u8 type = local_apic_timer_c2_ok ? ACPI_STATE_C3 : ACPI_STATE_C2;
+ if (cpu_has(&cpu_data(pr->id), X86_FEATURE_ARAT))
+ return;
+
/*
* Check, if one of the previous states already marked the lapic
* unstable
--
1.6.0.6
--
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