linux-kernel - Re: [Replacement][PATCH 2/6] PM / Domains: Fix hibernation restore of devices, v2

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Date:	Fri, 16 Mar 2012 09:03:29 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Linux-sh list <linux-sh@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Magnus Damm <magnus.damm@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Cao Minh Hiep <hiepcm@...il.com>
Subject: Re: [Replacement][PATCH 2/6] PM / Domains: Fix hibernation restore
 of devices, v2

On Thu, Mar 15, 2012 at 10:00:09PM +0100, Rafael J. Wysocki wrote:
> On Thursday, March 15, 2012, Simon Horman wrote:
> > On Tue, Mar 13, 2012 at 10:32:42PM +0100, Rafael J. Wysocki wrote:
> > > On Tuesday, March 13, 2012, Rafael J. Wysocki wrote:
> > > > From: Rafael J. Wysocki <rjw@...k.pl>
> > > > 
> > > > During resume from hibernation pm_genpd_restore_noirq() has to
> > > > deal with software state left by pm_genpd_suspend_noirq() and
> > > > unknown hardware state (the boot kernel may leave all PM domains and
> > > > devices in arbitrary states).  For this reason, make it attempt to
> > > > power cycle each domain when before resuming its first device to
> > > > possibly get rid of any unwanted hardware state that may interfere
> > > > with genpd_start_dev() later on.
> > > > 
> > > > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > > 
> > > I realized that this wasn't a good idea because of patch [3/6] (we
> > > can't power cycle domains containing "always on" devices), so I
> > > decided to only fix the really broken things in pm_genpd_restore_noirq().
> > > 
> > > Of course, patch [3/6] also needs to be updated on top of the below to
> > > avoid starting "always on" devices in pm_genpd_restore_noirq() (it has
> > > to assume that they will be "always on" in the boot kernel too, but that
> > > seems to be a reasonable expectation).
> > > 
> > > Please note that those changes only affect resume from hibernation, so
> > > they don't invalidate the testing that has already been carried out.
> > 
> > Hi Rafael,
> > 
> > sorry for such a naeive question, but if I was to test
> > hibernate on the Mackerel how would I achieve resume?
> > Is there a button I should press?
> 
> Hibernation is not supported on Mackerel at the moment, so you'd need to add
> some platform hooks first.  Then, you'd need some persistent storage with
> a swap patrition (or swap file at least) to save the image.  You'd need
> to point your kernel to the image storage using the resume= and resume_offset=
> command line switches.  Then, you should be able to create an image and the
> kernel would look for it automatically on the next boot.
> 
> Still, I'm not sure if doing all that at this point is worth the effort.

Point taken.
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