From e9cdd343a5e42c43bcda01e609fa23089e026470 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Thu, 26 May 2011 11:19:52 -0400 Subject: [PATCH] x86, amd: Do not enable ARAT feature on AMD processors below family 0x12 Commit b87cf80af3ba4b4c008b4face3c68d604e1715c6 added support for ARAT (Always Running APIC timer) on AMD processors that are not affected by erratum 400. This erratum is present on certain processor families and prevents APIC timer from waking up the CPU when it is in a deep C state, including C1E state. Determining whether a processor is affected by this erratum may have some corner cases and handling these cases is somewhat complicated. In the interest of simplicity we won't claim ARAT support on processor families below 0x12 and will go back to broadcasting timer when going idle. Signed-off-by: Boris Ostrovsky Link: http://lkml.kernel.org/r/1306423192-19774-1-git-send-email-ostr@amd64.org Tested-by: Boris Petkov Cc: Hans Rosenfeld Cc: Andreas Herrmann Cc: Chuck Ebbert Cc: stable@kernel.org # 32.x, 38.x, 39.x Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/amd.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 8f5cabb3c5b0..b13ed393dfce 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -612,8 +612,11 @@ 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)) + /* + * Family 0x12 and above processors have APIC timer + * running in deep C states. + */ + if (c->x86 > 0x11) set_cpu_cap(c, X86_FEATURE_ARAT); /* -- 2.34.1