[linux-pm] [RFC PATCH v4] ARM hibernation/suspend-to-disk support

[santosh.shilimkar@ti.com (Santosh Shilimkar)]

On 6/9/2011 10:10 PM, Russell King - ARM Linux wrote:
> On Thu, Jun 09, 2011 at 09:57:06PM +0530, Santosh Shilimkar wrote:
>> On 6/9/2011 9:10 PM, Russell King - ARM Linux wrote:
>>> On Thu, Jun 09, 2011 at 04:30:08PM +0100, Frank Hofmann wrote:
>>>> Btw, when testing this I found that generic cpu_suspend seems to be just
>>>> fine for OMAP3; the OMAP platforms though do not at this time use the
>>>> generic cpu_suspend/resume for sleep, is it planned to change that ?
>>>
>>> That's because OMAP was doing changes to their sleep code while I was
>>> consolidating the sleep code, and although I asked several times that
>>> the OMAP folk should participate in this effort, but evidentally I was
>>> unsuccessful in achieving anything in that direction.
>>
>> Agreed but the situation at that point was the code was not at
>> all in convertible position. Looking at your below comment,
>> it's still not :)
>
> Well, I had a look before posting this reply, and ran away from it.
> I've gone back to it several times since, and got a similar reaction.
>
> I seem to remember that it looked _more_ convertable when I looked at
> it when doing the generic suspend/resume support - I could see a nice
> simple way to pull out the saving and just leave the PLL resume stuff
> in SRAM.
>
> I'm now convinced that if I try to convert it use the generic support,
> it will end up being a horrible broken mess.
I must admit that I had same impression when I started looking at it.

Few provisions are necessary for OMAP which I can think of are:
1. WFI loop should be made a seperate function so that it can pushed
on SRAM which is must for OMAP3.

2. A callback before WFI to implement the Errata WA's

3. Avoid direct write to AUXCTRL in generic suspend code.

4. Before MMU is enabled in resume a callback to restore
secure register, setup auxctrl etc.

With above addressed, mostly we should be able to
get it working. But for sure it will mess up the
simple suspend hooks as they are today.

btw, for OMAP4 as well I looked at this suspend hooks
and most the requirement above apply except 4)

Additionally the L2 cache handling isn't part of
these common suspend hooks.

Regards
Santosh