linux-kernel - [PATCH 2/2] PM / Runtime: use deferrable timer for autosuspend

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Message-Id: <1452619040-27137-2-git-send-email-l.stach@pengutronix.de>
Date:	Tue, 12 Jan 2016 18:17:20 +0100
From:	Lucas Stach <l.stach@...gutronix.de>
To:	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Pavel Machek <pavel@....cz>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, patchwork-lst@...gutronix.de
Subject: [PATCH 2/2] PM / Runtime: use deferrable timer for autosuspend

The timeouts used in PM autosuspend are relatively coarse (the shortest
I could find in a quick search through the kernel is 50ms). As they are
already handled relaxed by saving the overhead of always rearming the
timer by opportunistically suspending a device a bit early, it should
not matter if the the timeout is missed slightly.

By using a deferrable timer the CPU will not be woken just to handle
the autosuspend timeout, but handling will be batched with other
wakeups in the system.

Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
---
 drivers/base/power/runtime.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index e1a10a03df8e..975a282600ff 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1383,7 +1383,7 @@ void pm_runtime_init(struct device *dev)
 	INIT_WORK(&dev->power.work, pm_runtime_work);

 	dev->power.timer_expires = 0;
-	setup_timer(&dev->power.suspend_timer, pm_suspend_timer_fn,
+	setup_deferrable_timer(&dev->power.suspend_timer, pm_suspend_timer_fn,
 			(unsigned long)dev);

 	init_waitqueue_head(&dev->power.wait_queue);
-- 
2.6.4