1 files changed, 27 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);