linux-kernel - Re: [PATCH v3] power: add an API to log wakeup reasons

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Message-ID: <1559784.2mnpODc5zV@vostro.rjw.lan>
Date:	Thu, 13 Mar 2014 23:18:14 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Ruchi Kandoi <kandoiruchi@...gle.com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	ghackmann@...gle.com, john.stultz@...aro.org, toddpoynor@...gle.com
Subject: Re: [PATCH v3] power: add an API to log wakeup reasons

Hi,

I saw the v4, but I don't have it handy, so replying here.

On Wednesday, March 12, 2014 12:46:38 PM Ruchi Kandoi wrote:
> For power management diagnostic purposes, it is often useful to know
> what interrupts are frequently waking the system from low power
> suspend mode, especially on battery-powered consumer electronics
> devices that are expected to spend much of their time in low-power
> suspend while not in active use.  For example, reduced battery life on
> a mobile phone may be caused in part by frequent wakeups by broadcast
> traffic on a busy wireless LAN even while the screen is off and the
> phone not in active use.
> 
> Add API log_wakeup_reason() exposes it to userspace via the sysfs path
> /sys/kernel/wakeup_reasons/last_resume_reason. This API would be called
> from the paltform specific, or from the driver for the interrupt controller,
> when the system resumes because of an IRQ. It logs the reasons which caused
> the system to wakeup from the low-power mode.

So what exactly is wrong with using wakeup sources for this purpose?

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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