Re: calling runtime PM from system PM methods

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Saturday, June 11, 2011, Mark Brown wrote:
> On Fri, Jun 10, 2011 at 10:27:25PM +0200, Rafael J. Wysocki wrote:
> 
> > So, there are a few things to consider:
> 
> > * Can the device do things like DMA?
> > * Does the driver use a workqueue?
> > * Does it use timers?
> 
> > In all of the above cases your system suspend handling will require extra
> > care to make sure those things won't get in the way of the suspend process.
> 
> Yes, that's the quiesce operation I think myself or Alan mentioned.
> 
> > It's probably fair to say that everithing depends on the subsystem, what it
> > does and what it expects from the driver.  In the extreme case, when the
> > subsystem is like the platform bus type, the driver unfortunately is on its
> > own and has to deal with the whole complexity.
> 
> I'm pretty much only working with buses that have no infrastructure and
> for which power is essentially orthogonal to the control bus itself -
> that's a very large proportion of the embedded space.  It really feels
> like we could be doing a better job for drivers using these buses,
> there's a lot of similarities in what many of them need but I can never
> find the time to get my head round it confidently enough to actually
> propose anything.

I agree.  That's one of the reasons why I introduced the struct dev_power_domain
thing a while ago and the generic PM domains patchset I've just posted is a step
in that direction.

Thanks,
Rafael