[PATCH] x86/apic: Fix duplicated lapic timer calculation

[Jacob Pan]

Local APIC timer clockevent parameters can be calculated based on
platform specific methods. However the code is mostly duplicated
with the interrupt based calibration. This causes further updates
prone to mistakes.

Fixes: 4aed89d ("x86, lapic-timer: Increase the max_delta to 31 bits")

Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/apic/apic.c | 46
++++++++++++++++++++++++++------------------- 1 file changed, 27
insertions(+), 19 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index b7bcdd7..b2ef91c 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -802,6 +802,24 @@ calibrate_by_pmtimer(long deltapm, long *delta,
long *deltatsc) return 0;
 }
 
+static int __init calculate_lapic_clockevent(void)
+{
+	if (!lapic_timer_frequency)
+		return -1;
+
+	/* Calculate the scaled math multiplication factor */
+	lapic_clockevent.mult =
div_sc(lapic_timer_frequency/APIC_DIVISOR,
+					TICK_NSEC,
lapic_clockevent.shift);
+	lapic_clockevent.max_delta_ns =
+		clockevent_delta2ns(0x7FFFFFFF, &lapic_clockevent);
+	lapic_clockevent.max_delta_ticks = 0x7FFFFFFF;
+	lapic_clockevent.min_delta_ns =
+		clockevent_delta2ns(0xF, &lapic_clockevent);
+	lapic_clockevent.min_delta_ticks = 0xF;
+
+	return 0;
+}
+
 static int __init calibrate_APIC_clock(void)
 {
 	struct clock_event_device *levt = this_cpu_ptr(&lapic_events);
@@ -818,18 +836,17 @@ static int __init calibrate_APIC_clock(void)
 
 	if (boot_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER)) {
 		return 0;
-	} else if (lapic_timer_frequency) {
+	}
+
+	if (!calculate_lapic_clockevent()) {
 		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.max_delta_ticks = 0x7FFFFF;
-		lapic_clockevent.min_delta_ns =
-			clockevent_delta2ns(0xF, &lapic_clockevent);
-		lapic_clockevent.min_delta_ticks = 0xF;
+		/*
+		 * Newer platforms provide early calibration methods
must have always
+		 * running local APIC timers, no need for boradcast
timer.
+		 */
 		lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY;
+
 		return 0;
 	}
 
@@ -869,17 +886,8 @@ static int __init calibrate_APIC_clock(void)
 	pm_referenced = !calibrate_by_pmtimer(lapic_cal_pm2 -
lapic_cal_pm1, &delta, &deltatsc);
 
-	/* Calculate the scaled math multiplication factor */
-	lapic_clockevent.mult = div_sc(delta, TICK_NSEC *
LAPIC_CAL_LOOPS,
-				       lapic_clockevent.shift);
-	lapic_clockevent.max_delta_ns =
-		clockevent_delta2ns(0x7FFFFFFF, &lapic_clockevent);
-	lapic_clockevent.max_delta_ticks = 0x7FFFFFFF;
-	lapic_clockevent.min_delta_ns =
-		clockevent_delta2ns(0xF, &lapic_clockevent);
-	lapic_clockevent.min_delta_ticks = 0xF;
-
 	lapic_timer_frequency = (delta * APIC_DIVISOR) /
LAPIC_CAL_LOOPS;
+	calculate_lapic_clockevent();
 
 	apic_printk(APIC_VERBOSE, "..... delta %ld\n", delta);
 	apic_printk(APIC_VERBOSE, "..... mult: %u\n",
lapic_clockevent.mult);
-- 
2.7.4