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>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 1905ce98bee0..e7ae0d89e7e0 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:
+                        break;
+                }
+        }
+
         /*
          * There is a known erratum on Pentium III and Core Solo
          * and Core Duo CPUs.