1 files changed, 33 insertions, 9 deletions

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 46b2f41f8b05..0aed75a1e31b 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -702,6 +702,20 @@ unsigned long native_calibrate_tsc(void)
 		}
 	}
 
+	/*
+	 * TSC frequency determined by CPUID is a "hardware reported"
+	 * frequency and is the most accurate one so far we have. This
+	 * is considered a known frequency.
+	 */
+	setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
+
+	/*
+	 * For Atom SoCs TSC is the only reliable clocksource.
+	 * Mark TSC reliable so no watchdog on it.
+	 */
+	if (boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT)
+		setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
+
 	return crystal_khz * ebx_numerator / eax_denominator;
 }
 
@@ -1043,18 +1057,20 @@ static void detect_art(void)
 	if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF)
 		return;
 
-	cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator,
-	      &art_to_tsc_numerator, unused, unused+1);
-
-	/* Don't enable ART in a VM, non-stop TSC required */
+	/* Don't enable ART in a VM, non-stop TSC and TSC_ADJUST required */
 	if (boot_cpu_has(X86_FEATURE_HYPERVISOR) ||
 	    !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) ||
-	    art_to_tsc_denominator < ART_MIN_DENOMINATOR)
+	    !boot_cpu_has(X86_FEATURE_TSC_ADJUST))
 		return;
 
-	if (rdmsrl_safe(MSR_IA32_TSC_ADJUST, &art_to_tsc_offset))
+	cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator,
+	      &art_to_tsc_numerator, unused, unused+1);
+
+	if (art_to_tsc_denominator < ART_MIN_DENOMINATOR)
 		return;
 
+	rdmsrl(MSR_IA32_TSC_ADJUST, art_to_tsc_offset);
+
 	/* Make this sticky over multiple CPU init calls */
 	setup_force_cpu_cap(X86_FEATURE_ART);
 }
@@ -1064,6 +1080,11 @@ static void detect_art(void)
 
 static struct clocksource clocksource_tsc;
 
+static void tsc_resume(struct clocksource *cs)
+{
+	tsc_verify_tsc_adjust(true);
+}
+
 /*
  * We used to compare the TSC to the cycle_last value in the clocksource
  * structure to avoid a nasty time-warp. This can be observed in a
@@ -1096,6 +1117,7 @@ static struct clocksource clocksource_tsc = {
 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
 				  CLOCK_SOURCE_MUST_VERIFY,
 	.archdata               = { .vclock_mode = VCLOCK_TSC },
+	.resume			= tsc_resume,
 };
 
 void mark_tsc_unstable(char *reason)
@@ -1283,10 +1305,10 @@ static int __init init_tsc_clocksource(void)
 		clocksource_tsc.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP;
 
 	/*
-	 * Trust the results of the earlier calibration on systems
-	 * exporting a reliable TSC.
+	 * When TSC frequency is known (retrieved via MSR or CPUID), we skip
+	 * the refined calibration and directly register it as a clocksource.
 	 */
-	if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) {
+	if (boot_cpu_has(X86_FEATURE_TSC_KNOWN_FREQ)) {
 		clocksource_register_khz(&clocksource_tsc, tsc_khz);
 		return 0;
 	}
@@ -1363,6 +1385,8 @@ void __init tsc_init(void)
 
 	if (unsynchronized_tsc())
 		mark_tsc_unstable("TSCs unsynchronized");
+	else
+		tsc_store_and_check_tsc_adjust(true);
 
 	check_system_tsc_reliable();