Re: [linux-pm] calling runtime PM from system PM methods

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

On Friday, June 10, 2011, Mark Brown wrote:
> On Fri, Jun 10, 2011 at 08:49:03PM +0200, Rafael J. Wysocki wrote:
> > On Friday, June 10, 2011, Mark Brown wrote:
> 
> > > It seems like everyone's agreeing with each other here - from the user
> > > side the request seems to be largely for core infastructure like
> > > UNIVERSAL_DEV_PM_OPS() (which I'm not sure is a good idea any more given
> > > that it doesn't do anything to handle the runtime/system interaction?).
> 
> > I'm not sure what you mean here.  First, UNIVERSAL_DEV_PM_OPS() actually
> > does what it says, defines a set of operations to use for system suspend,
> > hibernation and runtime PM all the same.
> 
> Right, but in the light of what you guys are saying about the
> interactions between runtime suspend and resume I'm no longer clear that
> that is actually sane for something which does use runtime PM, and of
> course if a driver wants to support the wake configuration interface
> then this might also fall out of the window.

It is not generally safe and there are multiple factors deciding of it
(see the message I've just sent for details).

> > The Kevin's point originally was that it might be desirable to do things
> > like calling pm_runtime_suspend() from a driver's (system) .suspend()
> > callback, if I understood it correctly, and the answer was that it wasn't
> > the right thing to do (for reasons given elsewhere in the thread).
> 
> Yeah, I think it is too.
> 
> > Your point seems to be that simple drivers should not be required to
> > define separate callback routines, for example, for system suspend and
> > runtime PM.  However, they aren't required to do so, they can point
> > all of their "suspend" callback pointers to the same routine, which is
> > what the UNIVERSAL_DEV_PM_OPS() macro does.
> 
> So that's definitely safe?  I guess this partly comes back to the thing
> I'm saying about how I'm finding all this stuff difficult to reason
> about, every time I see such discussion I get confused about needing to
> worry about it or not.

Well, it's just that multiple things go into play here: the subsystem, the
overall complexity of the driver and so on.  I can probably say what's
good for a PCI driver, but that may not be suitable for a USB driver, for
one example.

Thanks,
Rafael