From: Boris Ostrovsky <[email protected]>
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.
Signed-off-by: Boris Ostrovsky <[email protected]>
Tested-by: Borislav Petkov <[email protected]>
Acked-by: Andreas Herrmann <[email protected]>
Acked-by: Mark Langsdorf <[email protected]>
---
arch/x86/kernel/cpu/amd.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 7c7bedb..48eaa1b 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
--
1.7.1
Commit-ID: b87cf80af3ba4b4c008b4face3c68d604e1715c6
Gitweb: http://git.kernel.org/tip/b87cf80af3ba4b4c008b4face3c68d604e1715c6
Author: Boris Ostrovsky <[email protected]>
AuthorDate: Tue, 15 Mar 2011 12:13:44 -0400
Committer: Ingo Molnar <[email protected]>
CommitDate: Wed, 16 Mar 2011 14:03:33 +0100
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 <[email protected]>
Acked-by: Andreas Herrmann <[email protected]>
Acked-by: Mark Langsdorf <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Signed-off-by: Boris Ostrovsky <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/kernel/cpu/amd.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 7c7bedb..48eaa1b 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