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x86, AMD: Set ARAT feature on AMD processors

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commit b87cf80af3 upstream.

Support for Always Running APIC timer (ARAT) was introduced in
commit db954b5898. This feature
allows us to avoid switching timers from LAPIC to something else
(e.g. HPET) and go into timer broadcasts when entering deep
C-states.

AMD processors don't provide a CPUID bit for that feature but
they also keep APIC timers running in deep C-states (except for
cases when the processor is affected by erratum 400). Therefore
we should set ARAT feature bit on AMD CPUs.

Tested-by: Borislav Petkov <borislav.petkov@amd.com>
Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Mark Langsdorf <mark.langsdorf@amd.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@amd.com>
LKML-Reference: <1300205624-4813-1-git-send-email-ostr@amd64.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Boris Ostrovsky
2011-03-15 12:13:44 -04:00
committed by Greg Kroah-Hartman
parent 7a3b25c055
commit d4274252d1
1 changed files with 4 additions and 0 deletions
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4
arch/x86/kernel/cpu/amd.c
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@@ -566,6 +566,10 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
}
}
#endif
/* As a rule processors have APIC timer running in deep C states */
if (c->x86 >= 0xf && !cpu_has_amd_erratum(amd_erratum_400))
set_cpu_cap(c, X86_FEATURE_ARAT);
}
#ifdef CONFIG_X86_32