ACPI: Minor cleanup eliminating redundant PMTIMER_TICKS to NS conversion

acpi_enter_[simple,bm] does
idle timing in ns, convert it to timeval, then to us, then to
pmtimer_ticks and then back to ns.

This patch changes things to
idle timing in ns, convert it to us, and then to pmtimer_ticks.

Just saves an imul along this path, but makes the code cleaner.
Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/processor_idle.c

@@ -859,6 +859,7 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
 	struct acpi_processor *pr;
 	struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
 	ktime_t  kt1, kt2;
+	s64 idle_time_ns;
 	s64 idle_time;
 	s64 sleep_ticks = 0;
 
@@ -900,12 +901,14 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
 	sched_clock_idle_sleep_event();
 	acpi_idle_do_entry(cx);
 	kt2 = ktime_get_real();
-	idle_time =  ktime_to_us(ktime_sub(kt2, kt1));
+	idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1));
+	idle_time = idle_time_ns;
+	do_div(idle_time, NSEC_PER_USEC);
 
 	sleep_ticks = us_to_pm_timer_ticks(idle_time);
 
 	/* Tell the scheduler how much we idled: */
-	sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
+	sched_clock_idle_wakeup_event(idle_time_ns);
 
 	local_irq_enable();
 	current_thread_info()->status |= TS_POLLING;
@@ -933,6 +936,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
 	struct acpi_processor *pr;
 	struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
 	ktime_t  kt1, kt2;
+	s64 idle_time_ns;
 	s64 idle_time;
 	s64 sleep_ticks = 0;
 
@@ -1015,11 +1019,13 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
 		spin_unlock(&c3_lock);
 	}
 	kt2 = ktime_get_real();
-	idle_time =  ktime_to_us(ktime_sub(kt2, kt1));
+	idle_time_ns = ktime_to_us(ktime_sub(kt2, kt1));
+	idle_time = idle_time_ns;
+	do_div(idle_time, NSEC_PER_USEC);
 
 	sleep_ticks = us_to_pm_timer_ticks(idle_time);
 	/* Tell the scheduler how much we idled: */
-	sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
+	sched_clock_idle_wakeup_event(idle_time_ns);
 
 	local_irq_enable();
 	current_thread_info()->status |= TS_POLLING;