1 files changed, 26 insertions, 7 deletions

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index a2fd72e0ab35..f98d84caf94c 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -186,7 +186,7 @@ static struct resource lapic_resource = {
         .flags = IORESOURCE_MEM | IORESOURCE_BUSY,
 };
 
-static unsigned int calibration_result;
+unsigned int lapic_timer_frequency = 0;
 
 static void apic_pm_activate(void);
 
@@ -454,7 +454,7 @@ static void lapic_timer_setup(enum clock_event_mode mode,
         switch (mode) {
         case CLOCK_EVT_MODE_PERIODIC:
         case CLOCK_EVT_MODE_ONESHOT:
-                __setup_APIC_LVTT(calibration_result,
+                __setup_APIC_LVTT(lapic_timer_frequency,
                                   mode != CLOCK_EVT_MODE_PERIODIC, 1);
                 break;
         case CLOCK_EVT_MODE_UNUSED:
@@ -638,6 +638,25 @@ static int __init calibrate_APIC_clock(void)
         long delta, deltatsc;
         int pm_referenced = 0;
 
+        /**
+         * check if lapic timer has already been calibrated by platform
+         * specific routine, such as tsc calibration code. if so, we just fill
+         * in the clockevent structure and return.
+         */
+
+        if (lapic_timer_frequency) {
+                apic_printk(APIC_VERBOSE, "lapic timer already calibrated %d\n",
+                                lapic_timer_frequency);
+                lapic_clockevent.mult = div_sc(lapic_timer_frequency/APIC_DIVISOR,
+                                        TICK_NSEC, lapic_clockevent.shift);
+                lapic_clockevent.max_delta_ns =
+                        clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
+                lapic_clockevent.min_delta_ns =
+                        clockevent_delta2ns(0xF, &lapic_clockevent);
+                lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY;
+                return 0;
+        }
+
         local_irq_disable();
 
         /* Replace the global interrupt handler */
@@ -679,12 +698,12 @@ static int __init calibrate_APIC_clock(void)
         lapic_clockevent.min_delta_ns =
                 clockevent_delta2ns(0xF, &lapic_clockevent);
 
-        calibration_result = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;
+        lapic_timer_frequency = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;
 
         apic_printk(APIC_VERBOSE, "..... delta %ld\n", delta);
         apic_printk(APIC_VERBOSE, "..... mult: %u\n", lapic_clockevent.mult);
         apic_printk(APIC_VERBOSE, "..... calibration result: %u\n",
-                    calibration_result);
+                    lapic_timer_frequency);
 
         if (cpu_has_tsc) {
                 apic_printk(APIC_VERBOSE, "..... CPU clock speed is "
@@ -695,13 +714,13 @@ static int __init calibrate_APIC_clock(void)
 
         apic_printk(APIC_VERBOSE, "..... host bus clock speed is "
                     "%u.%04u MHz.\n",
-                    calibration_result / (1000000 / HZ),
-                    calibration_result % (1000000 / HZ));
+                    lapic_timer_frequency / (1000000 / HZ),
+                    lapic_timer_frequency % (1000000 / HZ));
 
         /*
          * Do a sanity check on the APIC calibration result
          */
-        if (calibration_result < (1000000 / HZ)) {
+        if (lapic_timer_frequency < (1000000 / HZ)) {
                 local_irq_enable();
                 pr_warning("APIC frequency too slow, disabling apic timer\n");
                 return -1;