linux-kernel - Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

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Date:	Fri, 7 May 2010 10:50:30 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Daniel Walker <dwalker@...o99.com>
Cc:	Matthew Garrett <mjg@...hat.com>,
	Brian Swetland <swetland@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	mark gross <mgross@...ux.intel.com>, markgross@...gnar.org,
	Len Brown <len.brown@...el.com>, linux-doc@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.

* Daniel Walker <dwalker@...o99.com> [100507 10:15]:
> On Thu, 2010-05-06 at 19:00 -0700, Tony Lindgren wrote:
> 
> > Oh some SoC devices like omap hit retention or off modes in the idle loop.
> > That brings down the idle consumption of a running system to minimal
> > levels. It's basically the same as suspending the device in every idle loop.
> > 
> > The system wakes up every few seconds or so, but that already provides
> > battery life of over ten days or so on an idle system. Of course the
> > wakeup latencies are in milliseconds then.
> 
> MSM doesn't have those power states unfortunately .. Your kind of
> suggesting what I was suggesting in that we should suspend in idle. Your
> hardware can do it easier tho since your have power states that are
> equal to suspend.

You might be able to implement suspend-while-idle with cpuidle and
a custom idle function on MSM. That is if MSM supports waking to
a timer event and some device interrupts. However, if it only wakes
to pressing some power button, then you will get missed timers
and the system won't behave in a normal way.

Maybe you could still kill -STOP the misbehaving apps, then keep the
idle system running until some timer expires, then when no activity,
echo mem > /sys/power/state?

Regards,

Tony
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