Re: [RFC PATCH V3 3/5] powerpc/cpuidle: Generic powerpc backend cpuidle driver.

[Scott Wood <scottwood@freescale.com>]

On Thu, 2013-08-22 at 11:20 +0530, Deepthi Dharwar wrote:
> On 08/22/2013 01:38 AM, Scott Wood wrote:
> > On Wed, 2013-08-21 at 10:23 +0530, Deepthi Dharwar wrote:
> >> On 08/19/2013 11:47 PM, Scott Wood wrote:
> >>> What actual functionality is common to all powerpc but not common to
> >>> other arches?
> > 
> 
> The functionality here is idle states on powerpc  like the snooze loop
> that is common.
> Also, the basic registration of the driver, hotplug notifier etc for
> powerpc.

The snooze loop uses things like SPRN_PURR, get_lppaca(), and CTRL which
aren't common to all PPC (they might be common to all book3s64).  I also
don't see any hook for the low power mode entry -- is "snooze" just a
busy loop plus the de-emphasis stuff like HMT and CTRL[RUN]?  I'm not
familiar with the term "snooze" in this context.  I don't think we'd use
anything like that on our chips; we'd always at least "wait" or "doze"
depending on the chip.

It's not clear what is powerpc-specific about the notifier -- perhaps it
should go in drivers/cpuidle/.

> > The way forward is to give this file a more appropriate name based on
> > the hardware that it actually targets -- and to refactor it so that the
> > answer to that question is not complicated.
> 
> Sure, thanks.
> Our idea was to have POWER archs idle states merged at the first go.
> Only that is what is enabled in the current version (V4 posted out)
> ( Code is enabled for PSERIES and POWERNV only)
> If needed, other POWERPC archs might benefit by extending the same
> driver, that is why it is named cpuidle-powerpc.c
> 
> But if having cpuidle backend-driver separately for other powerpc arcs
> makes sense such that each one have their own state information etc
> then it makes sense to name the files as cpuidle-power.c,
> cpuilde-ppc32.c and so on.

Thanks.

-Scott