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x86 ACPI: Add support for Always Running APIC timer

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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@intel.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Venkatesh Pallipadi
2009-04-06 18:51:29 -07:00
committed by Len Brown
parent 577c9c456f
commit db954b5898
4 changed files with 11 additions and 0 deletions
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3
drivers/acpi/processor_idle.c
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@@ -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