linux-kernel - Re: [PATCH] SATA / AHCI: Do not play with the link PM during suspend to RAM

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Message-Id: <201008270109.36687.rjw@sisk.pl>
Date:	Fri, 27 Aug 2010 01:09:36 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Tejun Heo <htejun@...il.com>
Cc:	Stephan Diestelhorst <stephan.diestelhorst@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"linux-pm@...ts.osdl.org" <linux-pm@...ts.osdl.org>,
	Stephan Diestelhorst <stephan.diestelhorst@...il.com>
Subject: Re: [PATCH] SATA / AHCI: Do not play with the link PM during suspend to RAM

On Tuesday, August 24, 2010, Rafael J. Wysocki wrote:
> On Tuesday, August 24, 2010, Tejun Heo wrote:
> > On 08/23/2010 08:58 PM, Rafael J. Wysocki wrote:
> > > On Monday, August 23, 2010, Tejun Heo wrote:
> > >> Hello, sorry about the delay.
> > >>
> > >> On 08/19/2010 06:23 PM, Stephan Diestelhorst wrote:
> > >>> It says "max_performance", I have not touched anyhting. So it has been
> > >>> like that all the time. Would this explain why your patch did not show
> > >>> the debug printout?
> > >>
> > >> Hmm... okay.  Yeah, if you haven't been using IPM at all, there won't
> > >> be any debug messages but at the same time the posted patch should
> > >> have had the same effect as Rafael's patch as IPM path isn't traveled
> > >> at all.  Can you please check the followings?
> > >>
> > >> * You're actually running the correct patched kernel and modules.  It
> > >>   probably is a good idea to add a printk message.  ie. Apply the
> > >>   patch and add a printk() in ata_host_request_pm() in libata-core.c
> > >>   and make sure the debug messages appears.
> > >>
> > >> * Rafael's patch actually fixes the problem.  If you haven't been
> > >>   using IPM at all, Rafael's patch and mine should behave exactly the
> > >>   same (ie. no IPM operation at all during suspend/resume).  It could
> > >>   be that you're seeing a different issue.
> > >>
> > >> Rafael, can you please test my patch and see how your case behaves?
> > > 
> > > This one: http://lkml.org/lkml/2010/8/5/328 ?
> > 
> > Yeap, that one.  I can prep a test git branch if necessary.
> 
> No need to, but it's going to take a few days to verify on my box.

Well, no luck.  I was able to reproduce the issue on my box with this patch
applied on top of 2.6.32-rc2.

Which probably means that the link power management is not really involved
here and seems to turn up this statement:

rc = ata_host_request_pm(host, mesg, 0, ATA_EHI_QUIET, 1);

in ata_host_suspend() as the culprit.

Does it make sense?

Thanks,
Rafael
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