x86: Add cpu capability flag X86_FEATURE_NONSTOP_TSC_S3
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>
[jstultz: Fix checkpatch warning]
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 1905ce9..e7ae0d8 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -96,6 +96,18 @@
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:
+ break;
+ }
+ }
+
/*
* There is a known erratum on Pentium III and Core Solo
* and Core Duo CPUs.