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Date: Fri, 7 May 2010 10:50:30 -0700
From: Tony Lindgren <tony@atomide.com>
To: Daniel Walker <dwalker@fifo99.com>
Cc: Matthew Garrett <mjg@redhat.com>, Brian Swetland <swetland@google.com>,
       Alan Stern <stern@rowland.harvard.edu>,
       mark gross <mgross@linux.intel.com>, markgross@thegnar.org,
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       Kernel development list <linux-kernel@vger.kernel.org>,
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       Wu Fengguang <fengguang.wu@intel.com>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [linux-pm] [PATCH 1/8] PM: Add suspend block api.
Message-ID: <20100507175029.GG387@atomide.com>
References: <20100505234755.GI29604@atomide.com>
 <20100506134015.GA23426@srcf.ucam.org>
 <20100506170151.GA30928@atomide.com>
 <20100506170956.GA28104@srcf.ucam.org>
 <20100506171453.GC30928@atomide.com>
 <1273167311.20494.13.camel@c-dwalke-linux.qualcomm.com>
 <20100506183605.GF30928@atomide.com>
 <1273173110.20494.19.camel@c-dwalke-linux.qualcomm.com>
 <20100507020057.GG30928@atomide.com>
 <1273252837.3542.30.camel@c-dwalke-linux.qualcomm.com>
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* Daniel Walker <dwalker@fifo99.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