cpuidle: enter_state: Don't needlessly calculate diff time

Currently, ktime_us_delta() is invoked unconditionally to compute the
idle residency of the CPU, but it only makes sense to do that if a
valid idle state has been entered, so move the ktime_us_delta()
invocation after the entered_state >= 0 check.

While at it, merge two comment blocks in there into one and drop
a space between type casting of diff.

This patch has no functional changes.

Signed-off-by: Fieah Lim <kw@fieahl.im>
[ rjw: Changelog cleanup, comment format fix ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 6df894d65d9e270efe800ff0c371d8c775183f08..4a97446f66d836bbf4129454420108313872b26e 100644 (file)
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -247,17 +247,17 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
        if (!cpuidle_state_is_coupled(drv, index))
                local_irq_enable();
 
-       diff = ktime_us_delta(time_end, time_start);
-       if (diff > INT_MAX)
-               diff = INT_MAX;
-
-       dev->last_residency = (int) diff;
-
        if (entered_state >= 0) {
-               /* Update cpuidle counters */
-               /* This can be moved to within driver enter routine
+               /*
+                * Update cpuidle counters
+                * This can be moved to within driver enter routine,
                 * but that results in multiple copies of same code.
                 */
+               diff = ktime_us_delta(time_end, time_start);
+               if (diff > INT_MAX)
+                       diff = INT_MAX;
+
+               dev->last_residency = (int)diff;
                dev->states_usage[entered_state].time += dev->last_residency;
                dev->states_usage[entered_state].usage++;
        } else {