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Commit db954b58 authored by Venkatesh Pallipadi's avatar Venkatesh Pallipadi Committed by Len Brown
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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: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Acked-by: default avatarH. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 577c9c45

arch/x86/include/asm/cpufeature.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kernel/apic/apic.c

+6 −0
Original line number Diff line number Diff line
@@ -431,6 +431,12 @@ static void __cpuinit setup_APIC_timer(void) 
{

	struct clock_event_device *levt = &__get_cpu_var(lapic_events);



	if (cpu_has(&current_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());

arch/x86/kernel/cpu/addon_cpuid_features.c

+1 −0
Original line number Diff line number Diff line
@@ -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 }

	};

drivers/acpi/processor_idle.c

+3 −0
Original line number Diff line number Diff line
@@ -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