Re: [linux-pm] pm loss development

[mark gross]

On Fri, May 13, 2011 at 06:54:57PM +0200, Rafael J. Wysocki wrote:
> On Friday, May 13, 2011, Raffaele Recalcati wrote:
> > Hi Rafael,
> > 
> > 2011/5/12 Rafael J. Wysocki <rjw@xxxxxxx>:
> > > On Thursday, May 12, 2011, Raffaele Recalcati wrote:
> > >> What happen normally in runtime pm implementation is that every devices
> > >> are switched off and are enabled only when needed.
> > >> In our case instead we have a completely functional embedded system and,
> > >> when an asyncrhonous event appear, we have only some tens milliseconds
> > >> before the actual power failure takes place.
> > >> This patchset add a support in order to switch off not vital part of the system,
> > >> in order to allow the board to survive longer.
> > >> This allow the possibility to save important data.
> > >
> > > OK, so first, who decides what parts of the system are vital and what aren't?
> > 
> > Take a quick look at Documentation/power/loss.txt  paragrpah "2.4
> > Power loss policies".
> > You can decide what can be powered off.
> 
> I read the patches.  My question was about the general idea of who should
> be responsible of making these decisions.

I would expect the system integrator would based on the application the
device is getting deployed into.

A generic opportunistic policy for peripherals that are stateless and can
be trivially power gated off/on from an ISR could be a default but, for
peripherals that need to do some processing (like waiting on an eMMC DMA
to complete) can take time to power down into a safe state.

--mark

> 
> Thanks,
> Rafael
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