linux-kernel - Re: autosleep suspend too frquent problem

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Date:	Fri, 6 Jun 2014 12:30:56 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
Cc:	'Ulf Hansson' <ulf.hansson@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"rjw@...k.pl" <rjw@...k.pl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mmc <linux-mmc@...r.kernel.org>
Subject: Re: autosleep suspend too frquent problem

On Fri 2014-06-06 10:59:13, Wang, Yalin wrote:
> Hi  Pavel,
> 
> 
> This is kernel log from a Android phone:
> 
> <6>[ 7262.353794] PM: suspend exit 2014-05-07 21:19:17.438320072 UTC
> <6>[ 7262.353820] PM: suspend entry 2014-05-07 21:19:17.438348353 UTC
> <6>[ 7264.822367] PM: suspend exit 2014-05-07 21:19:19.906892259 UTC
> <6>[ 7264.822391] PM: suspend entry 2014-05-07 21:19:19.906919447 UTC
> <6>[ 7266.100346] PM: suspend exit 2014-05-07 21:19:21.184872206 UTC
> <6>[ 7266.100371] PM: suspend entry 2014-05-07 21:19:21.184899342 UTC
> <6>[ 7268.650852] PM: suspend exit 2014-05-07 21:19:23.735377778 UTC
> <6>[ 7268.650876] PM: suspend entry 2014-05-07 21:19:23.735404393 UTC
> <6>[ 7269.023665] PM: suspend exit 2014-05-07 21:19:26.398622725 UTC
> <6>[ 7269.023691] PM: suspend entry 2014-05-07 21:19:26.398651787 UTC
> <6>[ 7269.232675] PM: suspend exit 2014-05-07 21:19:28.959217201 UTC
> <6>[ 7269.250878] PM: suspend entry 2014-05-07 21:19:28.977414076 UTC
> <6>[ 7269.256004] PM: suspend exit 2014-05-07 21:19:28.982547202 UTC
> <6>[ 7269.260040] PM: suspend entry 2014-05-07 21:19:28.986580588 UTC
> <6>[ 7269.265169] PM: suspend exit 2014-05-07 21:19:28.991711785 UTC
> <6>[ 7269.269311] PM: suspend entry 2014-05-07 21:19:28.995851004 UTC
> <6>[ 7270.410962] PM: suspend exit 2014-05-07 21:19:30.137503920 UTC
> <6>[ 7270.410986] PM: suspend entry 2014-05-07 21:19:30.137529389 UTC
> <6>[ 7272.970123] PM: suspend exit 2014-05-07 21:19:32.696662461 UTC
> <6>[ 7272.973330] PM: suspend entry 2014-05-07 21:19:32.699869909 UTC
> <6>[ 7275.534527] PM: suspend exit 2014-05-07 21:19:35.261069387 UTC
> <6>[ 7275.534551] PM: suspend entry 2014-05-07 21:19:35.261095846 UTC
> <6>[ 7275.556227] PM: suspend exit 2014-05-07 21:19:35.282769491 UTC
> <6>[ 7275.579152] PM: suspend entry 2014-05-07 21:19:35.305686210 UTC
> <6>[ 7275.822618] PM: suspend exit 2014-05-07 21:19:37.918187092 UTC
> <6>[ 7275.822644] PM: suspend entry 2014-05-07 21:19:37.918215894 UTC
> <6>[ 7276.122721] PM: suspend exit 2014-05-07 21:19:40.479243344 UTC
> <6>[ 7276.122745] PM: suspend entry 2014-05-07 21:19:40.479269125 UTC
> <6>[ 7278.578212] PM: suspend exit 2014-05-07 21:19:42.934733395 UTC
> <6>[ 7278.578237] PM: suspend entry 2014-05-07 21:19:42.934761520 UTC
> 
> You can see there is several times suspend / resume status change 
> Form 2014-05-07 21:19:28. 959217201  to 2014-05-07 21:19:28.995851004
> 
> There is also some suspend fail in this log , the suspend return -EBUSY  
> Because of driver wake up system during suspend process .
> 
> During our power test , suspend frequently like this will consume more
> Power , because it will suspend/resume lots of
> Devices . Why don't we make a time window to make sure there is no more than
> 1 time suspend during the time window ?

If you can optimize power consumption on your hardware, by all means
go ahead. But arbitrary limit "don't suspend more than twice a second"
is probably not a way to go... not without some analysis.

You may want to take a look at n900 -- it uses regular idle, not
suspend, to save power. 

> I remember Android use wakelock for suspend in older linux kernel ,
> The wakelock will make some time window check to make sure
> Not suspend frequently ,  could autosleep also add this ?

Are you sure autosleep does not already have equivalent functionality?
									Pavel
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