linux-kernel - Re: Attempted summary of suspend-blockers LKML thread

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Message-ID: <AANLkTikCCeMG=DAQ04xqkvqH9tngBWyBA5VQTD4_15xU@mail.gmail.com>
Date:	Thu, 5 Aug 2010 15:16:51 -0700
From:	Brian Swetland <swetland@...gle.com>
To:	david@...g.hm
Cc:	kevin granade <kevin.granade@...il.com>,
	paulmck@...ux.vnet.ibm.com,
	Arve Hjønnevåg <arve@...roid.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	pavel@....cz, florian@...kler.org, stern@...land.harvard.edu,
	peterz@...radead.org, tglx@...utronix.de, alan@...rguk.ukuu.org.uk
Subject: Re: Attempted summary of suspend-blockers LKML thread

On Thu, Aug 5, 2010 at 3:09 PM,  <david@...g.hm> wrote:
>> Oops, yea that's actually a really bad example, that's probably
>> something that would be handled by low-power states.  I think the
>> incoming text message example is a good one though.  There seemed to
>> be a focus on user-interaction scale time scales, and I wanted to
>> point out that there are also very short duration time scales to
>> consider as well.
>
> good point, but I do think the short time scales are less common than people
> think.
>
> I'd love to get good examples of them
>
> on my iphone when a text message arrives the phone displays an alert for
> user-interaction times (it even lights the display to show who the message
> is from, and optionally a preview of the message)
>
> so what would wake a phone up from suspend where the phone should go back to
> sleep in under a second?

Here are some real-world examples from shipped android devices:
- battery gauging happens every 10 minutes, need to wake long enough
to chatter with the 1w interface and make sure the battery is not
exploding
- always on mail/im/calendar/etc sync often has network events that
happen every 5-10 minutes which cause devices to briefly wake up and
return to sleep
- gps tracker app might wake every couple minutes or every n gps
events to log location
- low power audio subsystems can wake you up every 1-4 seconds (pcm)
or 1-4 minutes (mp3) to fetch more data

Brian
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