linux-kernel - [PATCH 20/21] cpuidle: don't calculate time-diff if entered

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Date:	Sun, 22 Sep 2013 06:51:12 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	rjw@...k.pl, daniel.lezcano@...aro.org
Cc:	linaro-kernel@...ts.linaro.org, patches@...aro.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: [PATCH 20/21] cpuidle: don't calculate time-diff if entered_state == 0

If entered_state == 0, we don't need to set dev->last_residency to 'diff' as we
will be setting it to zero without using its new value.

And so move calculation of diff also inside the "if" statement.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpuidle/cpuidle.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index bf80236..cb81689 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -77,23 +77,22 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 
 	struct cpuidle_state *target_state = &drv->states[index];
 	ktime_t time_start, time_end;
-	s64 diff;
 
 	time_start = ktime_get();
 
 	entered_state = target_state->enter(dev, drv, index);
 
-	time_end = ktime_get();
+	if (entered_state >= 0) {
+		s64 diff;
 
-	local_irq_enable();
+		time_end = ktime_get();
+		diff = ktime_to_us(ktime_sub(time_end, time_start));
 
-	diff = ktime_to_us(ktime_sub(time_end, time_start));
-	if (diff > INT_MAX)
-		diff = INT_MAX;
+		if (diff > INT_MAX)
+			diff = INT_MAX;
 
-	dev->last_residency = (int) diff;
+		dev->last_residency = (int) diff;
 
-	if (entered_state >= 0) {
 		/* Update cpuidle counters */
 		/* This can be moved to within driver enter routine
 		 * but that results in multiple copies of same code.
@@ -104,6 +103,8 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 		dev->last_residency = 0;
 	}
 
+	local_irq_enable();
+
 	return entered_state;
 }
 
-- 
1.7.12.rc2.18.g61b472e

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