linux-kernel - Re: [PATCH v4] power: add an API to log wakeup reasons

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Date:	Mon, 7 Jul 2014 15:02:18 +0200
From:	John Stultz <john.stultz@...aro.org>
To:	Ruchi Kandoi <kandoiruchi@...gle.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	rjw@...ysocki.net, ghackmann@...gle.com, toddpoynor@...gle.com,
	Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [PATCH v4] power: add an API to log wakeup reasons

On Thu, Mar 13, 2014 at 6:05 PM, Ruchi Kandoi <kandoiruchi@...gle.com> 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.
>
> This information can be collected by userspace as part of the accounting
> kept on power consumption.

Rafael,
   I realize its been awhile here, but seeing as discussion on this
petered out somewhat ambiguously, I was curious if your thoughts on
using wakeup_sources for this was considered a prereq for further
discussion or if it was a softer thought experiment?

thanks
-john
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