1 files changed, 27 insertions, 0 deletions
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index dc4ed655dbbb..29fd50840b55 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -820,6 +820,33 @@ static int __init lapic_init_clockevent(void)
 	return 0;
 }
 
+bool __init apic_needs_pit(void)
+{
+	/*
+	 * If the frequencies are not known, PIT is required for both TSC
+	 * and apic timer calibration.
+	 */
+	if (!tsc_khz || !cpu_khz)
+		return true;
+
+	/* Is there an APIC at all? */
+	if (!boot_cpu_has(X86_FEATURE_APIC))
+		return true;
+
+	/* Deadline timer is based on TSC so no further PIT action required */
+	if (boot_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER))
+		return false;
+
+	/* APIC timer disabled? */
+	if (disable_apic_timer)
+		return true;
+	/*
+	 * The APIC timer frequency is known already, no PIT calibration
+	 * required. If unknown, let the PIT be initialized.
+	 */
+	return lapic_timer_period == 0;
+}
+
 static int __init calibrate_APIC_clock(void)
 {
 	struct clock_event_device *levt = this_cpu_ptr(&lapic_events);