2 files changed, 47 insertions, 6 deletions

diff --git a/arch/x86_64/kernel/apic.c b/arch/x86_64/kernel/apic.c
index 673a2fe9923c..c02218b3ae2b 100644
--- a/arch/x86_64/kernel/apic.c
+++ b/arch/x86_64/kernel/apic.c
@@ -40,6 +40,7 @@
 
 int apic_verbosity;
 int apic_runs_main_timer;
+int apic_calibrate_pmtmr __initdata;
 
 int disable_apic_timer __initdata;
 
@@ -746,14 +747,27 @@ static int __init calibrate_APIC_clock(void)
 	__setup_APIC_LVTT(1000000000);
 
 	apic_start = apic_read(APIC_TMCCT);
-	rdtscl(tsc_start);
-
-	do {
+#ifdef CONFIG_X86_PM_TIMER
+	if (apic_calibrate_pmtmr && pmtmr_ioport) {
+		pmtimer_wait(5000);  /* 5ms wait */
 		apic = apic_read(APIC_TMCCT);
-		rdtscl(tsc);
-	} while ((tsc - tsc_start) < TICK_COUNT && (apic - apic_start) < TICK_COUNT);
+		result = (apic_start - apic) * 1000L / 5;
+	} else
+#endif
+	{
+		rdtscl(tsc_start);
+
+		do {
+			apic = apic_read(APIC_TMCCT);
+			rdtscl(tsc);
+		} while ((tsc - tsc_start) < TICK_COUNT &&
+				(apic - apic_start) < TICK_COUNT);
+
+		result = (apic_start - apic) * 1000L * cpu_khz /
+					(tsc - tsc_start);
+	}
+	printk("result %d\n", result);
 
-	result = (apic_start - apic) * 1000L * cpu_khz / (tsc - tsc_start);
 
 	printk(KERN_INFO "Detected %d.%03d MHz APIC timer.\n",
 		result / 1000 / 1000, result / 1000 % 1000);
@@ -1115,6 +1129,13 @@ static __init int setup_noapicmaintimer(char *str)
 }
 __setup("noapicmaintimer", setup_noapicmaintimer);
 
+static __init int setup_apicpmtimer(char *s)
+{
+	apic_calibrate_pmtmr = 1;
+	return setup_apicmaintimer(NULL);
+}
+__setup("apicpmtimer", setup_apicpmtimer);
+
 /* dummy parsing: see setup.c */
 
 __setup("disableapic", setup_disableapic); 
diff --git a/arch/x86_64/kernel/pmtimer.c b/arch/x86_64/kernel/pmtimer.c
index 8b2655ae4e61..5c51d10408a6 100644
--- a/arch/x86_64/kernel/pmtimer.c
+++ b/arch/x86_64/kernel/pmtimer.c
@@ -80,6 +80,26 @@ int pmtimer_mark_offset(void)
 	return lost - 1;
 }
 
+static unsigned pmtimer_wait_tick(void)
+{
+	u32 a, b;
+	for (a = b = inl(pmtmr_ioport) & ACPI_PM_MASK;
+	     a == b;
+	     b = inl(pmtmr_ioport) & ACPI_PM_MASK)
+		;
+	return b;
+}
+
+/* note: wait time is rounded up to one tick */
+void pmtimer_wait(unsigned us)
+{
+	u32 a, b;
+	a = pmtimer_wait_tick();
+	do {
+		b = inl(pmtmr_ioport);
+	} while (cyc2us(b - a) < us);
+}
+
 void pmtimer_resume(void)
 {
 	last_pmtmr_tick = inl(pmtmr_ioport);