Messages in this thread | | | Date | Tue, 12 Mar 2013 14:14:12 -0700 | From | John Stultz <> | Subject | Re: [PATCH v4 1/4] x86: Add cpu capability flag X86_FEATURE_NONSTOP_TSC_S3 |
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On 03/11/2013 08:56 PM, Feng Tang wrote: > On some new Intel Atom processors (Penwell and Cloverview), there is > a feature that the TSC won't stop in S3 state, say the TSC value > won't be reset to 0 after resume. This feature makes TSC a more reliable > clocksource and could benefit the timekeeping code during system > suspend/resume cycle, so add a flag for it. > > Signed-off-by: Feng Tang <feng.tang@intel.com> > --- > arch/x86/include/asm/cpufeature.h | 1 + > arch/x86/kernel/cpu/intel.c | 12 ++++++++++++ > 2 files changed, 13 insertions(+) > > diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h > index 93fe929..a8466f2 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -100,6 +100,7 @@ > #define X86_FEATURE_AMD_DCM (3*32+27) /* multi-node processor */ > #define X86_FEATURE_APERFMPERF (3*32+28) /* APERFMPERF */ > #define X86_FEATURE_EAGER_FPU (3*32+29) /* "eagerfpu" Non lazy FPU restore */ > +#define X86_FEATURE_NONSTOP_TSC_S3 (3*32+30) /* TSC doesn't stop in S3 state */ > > /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */ > #define X86_FEATURE_XMM3 (4*32+ 0) /* "pni" SSE-3 */ > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c > index 1905ce9..fe57544 100644 > --- a/arch/x86/kernel/cpu/intel.c > +++ b/arch/x86/kernel/cpu/intel.c > @@ -96,6 +96,18 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) > sched_clock_stable = 1; > } > > + /* Penwell and Cloverview have the TSC which doesn't sleep on S3 */ > + if (c->x86 == 6) { > + switch (c->x86_model) { > + case 0x27: /* Penwell */ > + case 0x35: /* Cloverview */ > + set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC_S3); > + break; > + default: > + ;
Just FYI, checkpatch.sh complains that this should be default: break;
I've gone ahead and fixed that, but you might be sure to run checkpatch in the future before submitting.
thanks -john
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