On some new Intel Atom processors (Penwell and Cloverview), there is
a feature that the TSC won't stop S3, 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.t...@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 2d9075e..f7e1eac 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_TSC_S3_NOTSTOP (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 fcaabd0..532f873 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -97,6 +97,18 @@ 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_TSC_S3_NOTSTOP);
+ break;
+ default:
+ ;
+ }
+ }
+
/*
* There is a known erratum on Pentium III and Core Solo
* and Core Duo CPUs.
--
1.7.9.5
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