[RFC][PATCH 1/1] ARM: Add initial hibernation support

[Hiroshi DOYU]

From: ext Russell King - ARM Linux <linux at arm.linux.org.uk>
Subject: Re: [RFC][PATCH 1/1] ARM: Add initial hibernation support
Date: Fri, 16 Jul 2010 09:52:44 +0200

> On Thu, Jul 15, 2010 at 12:08:07PM +0300, Hiroshi DOYU wrote:
>> From: ext Russell King - ARM Linux <linux at arm.linux.org.uk>
>> Subject: Re: [RFC][PATCH 1/1] ARM: Add initial hibernation support
>> Date: Thu, 15 Jul 2010 10:41:18 +0200
>> 
>> > On Thu, Jul 15, 2010 at 08:34:50AM +0300, Hiroshi DOYU wrote:
>> >> Russell, would it be possible to put this into your next merge queue?
>> > 
>> > I think it needs quite a bit of rework - I certainly don't like all
>> > those CP15 register accesses there - that's asking for lots of ifdefs
>> > to spring up as more CPUs are supported.
>> >
>> > Eg, what about ensuring that state such as iWMMXt on PXA CPUs is
>> > properly restored?
>> 
>> Right. This arch specific part can be something like
>> "suspend-v[3-7].S" to accomodate those differences
> 
> It's not quite that simple - things like iWMMXt aren't part of the ARM
> arch specs.
>
>> > We already have code which knows what needs to be saved across a
>> > power-off transition - its what we use for our normal suspend/resume
>> > functionality, so we should look at re-using that code for hibernate
>> > as well.  We really don't want to be maintaining two sets of code
>> > doing the same thing.
>> 
>> Could you explain which code you're refering for the existing one?
> 
> The code which handles saving state for the existing suspend/resume
> support.  This code already saves the necessary state from CP15 and
> any other state which needs to be saved prior to putting the system
> into low power mode.
> 
> Every machine class which supports suspend today has their own chunk
> of code which does this, normally called something like sleep.S

Ok, it seems to be the way to try to make use of the existing one for
suspend-to-ram with some modifications.