Message-ID: <20140317204410.GA1118@arch.cereza>
Date:	Mon, 17 Mar 2014 17:44:10 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Sebastian Capella <sebastian.capella@...aro.org>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Len Brown <len.brown@...el.com>,
	Russell King <linux@....linux.org.uk>,
	Jonathan Austin <jonathan.austin@....com>,
	Victor Kamensky <victor.kamensky@...aro.org>,
	Nicolas Pitre <nico@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Laura Abbott <lauraa@...eaurora.org>,
	Sricharan R <r.sricharan@...com>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Russ Dill <Russ.Dill@...com>,
	Catalin Marinas <catalin.marinas@....com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Jiang Liu <liuj97@...il.com>
Subject: Re: [PATCH v7 2/2] ARM hibernation / suspend-to-disk

On Mar 17, Sebastian Capella wrote:
> On 16 March 2014 00:09, Ezequiel Garcia
> <ezequiel.garcia@...e-electrons.com> wrote:
> > On Mar 05, Sebastian Capella wrote:
> > [..]
> >> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> >> index 1f8fed9..83707702 100644
> >> --- a/arch/arm/mm/Kconfig
> >> +++ b/arch/arm/mm/Kconfig
> >> @@ -611,6 +611,11 @@ config CPU_USE_DOMAINS
> >>  config IO_36
> >>       bool
> >>
> >> +config ARCH_HIBERNATION_POSSIBLE
> ...
> >> +     default y if CPU_ARM920T || CPU_ARM926T || CPU_SA1100 || CPU_XSCALE || CPU_XSC3 || CPU_V6 || CPU_V6K || CPU_V7
> ...
> > Is there any reason why CPU_FEROCEON is not listed here? FWIW, I've just built
> > (but not really tested) a Kirkwood kernel with CONFIG_HIBERNATION=y.
> No reason; I did not change this from the original patch I'd received.
>  I didn't try to get a comprehensive list of supported hardware.  To
> my understanding, the goal is to get the infrastructure in so that
> people can start working on their platforms and add support for them.
> 

Sure, no problem. If you consider that build-test is enough, feel free to put
CPU_FEROCEON on that list. We added suspend/resume to feroceon not long ago.

> > And is there any reason to put this config in arch/arm/mm/Kconfig, instead of
> > in arch/arm/Kconfig, below ARCH_SUSPEND_POSSIBLE?
> I don't have a reason.  Anyone else have a comment on this?
> Otherwise, I'll move it.. thanks!
>

It looked reasonable to me.

> > I'm also puzzled about having two separate options for suspend and hibernate,
> > maybe someone can explain me why a given CPU would support the former but not
> > the latter?
> It's part of having the generic hibernation implemented and available
> but with architecture specific dependencies.  Where an architecture
> may not have support for hibernation, it will prevent compilation of
> the generic hibernation support.  For example, at the moment, ARM does
> not support hibernation.
[..]

I guess my question wasn't clear. I mean to ask: Are there any other
requirements on an ARM platform to support hibernation, other than
suspend/resume support?

If this is the *only* requirement, it seems to me we could make our
ARCH_SUSPEND_POSSIBLE also select ARCH_HIBERNATION_POSSIBLE.

Does this make sense?
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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