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authorBoris Ostrovsky <boris.ostrovsky@amd.com>2011-03-15 19:13:44 +0300
committerIngo Molnar <mingo@elte.hu>2011-03-16 16:03:33 +0300
commitb87cf80af3ba4b4c008b4face3c68d604e1715c6 (patch)
treede37fabdc7bc8dc73828469ef989a2cf976d8027
parent1d3e09a304e6c4e004ca06356578b171e8735d3c (diff)
downloadlinux-b87cf80af3ba4b4c008b4face3c68d604e1715c6.tar.xz
x86, AMD: Set ARAT feature on AMD processors
Support for Always Running APIC timer (ARAT) was introduced in commit db954b5898dd3ef3ef93f4144158ea8f97deb058. 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>
-rw-r--r--arch/x86/kernel/cpu/amd.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 7c7bedb83c5a..48eaa1b6fc46 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -594,6 +594,10 @@ 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