linux-kernel - Re: PM / Wakeup: Introduce wakeup source objects and event statistics (v2)

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Message-ID: <87eict5hhx.fsf@deeprootsystems.com>
Date:	Thu, 16 Sep 2010 17:41:14 -0700
From:	Kevin Hilman <khilman@...prootsystems.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Arve Hjønnevåg 
	<arve@...roid.com>,
	"Linux-pm mailing list" <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: PM / Wakeup: Introduce wakeup source objects and event statistics (v2)

"Rafael J. Wysocki" <rjw@...k.pl> writes:

> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: PM / Wakeup: Introduce wakeup source objects and event statistics (v2)
>
> Introduce struct wakeup_source for representing system wakeup sources
> within the kernel and for collecting statistics related to them.
> Make the recently introduced helper functions pm_wakeup_event(),
> pm_stay_awake() and pm_relax() use struct wakeup_source objects
> internally, so that wakeup statistics associated with wakeup devices
> can be collected and reported in a consistent way (the definition of
> pm_relax() is changed, which is harmless, because this function is
> not called directly by anyone yet).  Introduce new wakeup-related
> sysfs device attributes in /sys/devices/.../power for reporting the
> device wakeup statistics.
>
> Change the global wakeup events counters event_count and
> events_in_progress into atomic variables, so that it is not necessary
> to acquire a global spinlock in pm_wakeup_event(), pm_stay_awake()
> and pm_relax(), which should allow us to avoid lock contention in
> these functions on SMP systems with many wakeup devices.
>
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>

Hi Rafael,

This looks like a really useful feature.  Was doing some experiments
with this on OMAP, and found a minor cut-and-paste bug in the
Documentation file:

[...]

> +What:		/sys/devices/.../power/wakeup_max_time_ms
> +Date:		September 2010
> +Contact:	Rafael J. Wysocki <rjw@...k.pl>
> +Description:
> +		The /sys/devices/.../wakeup_max_time_ms attribute contains
> +		the maximum time of processing a single wakeup event associated
> +		with the device, in milliseconds.  This attribute is read-only.
> +		If the device is not enabled to wake up the system from sleep
> +		states, this attribute is empty.
> +
> +What:		/sys/devices/.../power/wakeup_max_time_ms
                                                      ^^^
s/max/last/ for this one.

> +Date:		September 2010
> +Contact:	Rafael J. Wysocki <rjw@...k.pl>
> +Description:
> +		The /sys/devices/.../wakeup_last_time_ms attribute contains
> +		the value of the monotonic clock corresponding to the time of
> +		signaling the last wakeup event associated with the device, in
> +		milliseconds.  This attribute is read-only.  If the device is
> +		not enabled to wake up the system from sleep states, this
> +		attribute is empty.

Kevin
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