Re: [linux-pm] [patch update 2 fix] PM: Introduce core framework for run-time PM of I/O devices

Rafael J. Wysocki
2009-06-22T15:52:30Z

On Monday 22 June 2009, Alan Stern wrote:
> On Mon, 22 Jun 2009, Rafael J. Wysocki wrote:
>
> > On Monday 22 June 2009, Alan Stern wrote:
> > > On Sun, 21 Jun 2009, Rafael J. Wysocki wrote:
> > >
> > > > > Seriously, there _are_ places where drivers get bound to device before
> > > > > those devices are registered. This happens for example in USB when a
> > > > > bunch of related interfaces are present in the same physical device.
> > > > > When the first interface is registered, its driver binds itself to all
> > > > > the others even though they haven't been registered yet.
> > > >
> > > > Well, the suspend functions could be protected against that under the
> > > > assumption that no suspend is possible for resume_counter = 0 (then, the "good
> > > > to go" value would be -1).
> > > >
> > > > Still, the resume functions start from acquring a spinlock, which is not going
> > > > to work if that spinlock is uninitialized.
> > >
> > > The initialization needs to be improved. Most of the code in
> > > pm_runtime_init() should be called from device_pm_init(), and the rest
> > > should be moved into a separate pm_runtime_add() routine to be called
> > > from device_pm_add().
> >
> > OK
> >
> > In that case, I think, the initialization of the spinlock and resume_counter
> > can be put into the thing called by device_pm_init().
>
> Right.
>
> > > One of the things pm_runtime_add() could do is change the status from
> > > RPM_UNREGISTERED to RPM_ACTIVE.
> >
> > If the status is initially (ie. at the device_pm_init() point) RPM_ACTIVE and
> > resume_couter is initially 1, what are we going to need RPM_UNREGISTERED for?
>
> Okay, we don't need it then. I forgot to mention in the previous
> message that there also has to be a pm_runtime_del() routine, which
> should cancel pending workqueue items and set the counter to some high
> value so that no new items are added.

Should that be called by device_pm_remove()? I think so.

Rafael