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

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Message-ID: <AANLkTikOuY-q42mDRmxc-9W0uLeJeW-hiFG26WrV7CfU@mail.gmail.com>
Date:	Thu, 5 Aug 2010 17:22:10 -0700
From:	Brian Swetland <swetland@...gle.com>
To:	david@...g.hm
Cc:	paulmck@...ux.vnet.ibm.com,
	kevin granade <kevin.granade@...il.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 5:16 PM,  <david@...g.hm> wrote:
>>>
>>> So for an mp3 playback, does an Android suspend between data fetches?
>>
>> It can if the latency is long enough (which is why I point out low
>> power audio which is usually high latency).  For low latency (system
>> sounds, etc) 10-25ms between buffers it's not practical to fully
>> suspend but we will go to the lowest power state in idle if possible.
>
> the playback is able to continue even with all the clocks stopped? that
> surprises me. I would hav expected it to be able to sleep while playing
> audio, but not do a full suspend.

Obviously not all clocks are stopped (the DSP and codec are powered
and clocked, for example), but yeah we can clock gate and power gate
the cpu and most other peripherals while audio is playing on a number
of ARM SoC designs available today (and the past few years).

Brian
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