Re: irq mask swapping during suspend/resume

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Friday, September 26, 2014 09:58:39 AM Eric Caruso wrote:
> I was putting together a prototype for this, and ran into a design
> issue. It's not obvious how to get from the struct wakeup_source to
> places where we hold all of the relevant device information or irq
> information. If we were to walk the list of wakeup source objects,
> where would we actually get the irq information to call
> enable_irq_wake()?
> 
> Does this just require a bunch of extra plumbing we don't have right
> now, and this is what you meant by changes to wakeup_source_create()
> and friends?

Yes, that's it.

But at least some drivers call enable_irq_wake() today, so it should just
work for devices handled by them.  That may not be all devices you want,
though.

And BTW, there is a problem with the approach I was talking about which is
the sysfs interface for enabling wakeup, so we actually need to put wakeup
IRQ information into struct dev_pm_info and point to that from the
associated wakeup source object.  It still should be doable though.

> On Sat, Sep 20, 2014 at 5:48 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> > On Thursday, September 18, 2014 01:32:06 PM Thomas Gleixner wrote:
> >> On Wed, 17 Sep 2014, Dmitry Torokhov wrote:
> >> > Hi Thomas,
> >> >
> >> > On Wednesday, September 17, 2014 12:05:42 PM Thomas Gleixner wrote:
> >> > > On Tue, 16 Sep 2014, Eric Caruso wrote:
> >> > > > We would like to be able to set different irq masks for triggers during
> >> > > > normal operation and for waking up the system. For example, while a laptop
> >> > > > is awake, closing the lid and opening the lid should both fire an
> >> > > > interrupt, but when the system is asleep, we would like to stay asleep
> >> > > > when
> >> > > > closing the lid.
> >> > > >
> >> > > > We are thinking about stashing the irq mask used specifically for waking
> >> > > > the system up in the irq_desc struct, and then swapping it during
> >> > > > enable_irq_wake and disable_irq_wake calls. Devices that do not specify a
> >> > > > different wake mask will use their normal trigger mask for both
> >> > > > situations.
> >> > > >
> >> > > > Is this acceptable?
> >> > >
> >> > > Not really. Why should irq_desc provide storage for random
> >> > > configurations and bind them to some random system state?
> >> > >
> >> > > What's wrong with calling
> >> > >
> >> > >        irq_set_type(irq, B);
> >> > >        enable_irq_wake(irq);
> >> > >
> >> > >        disable_irq_wake(irq);
> >> > >        irq_set_type(irq, A);
> >> >
> >> > The desire is to avoid doing it in [every] driver but rather have it done
> >> > centrally by device/PM core. It does not have to be irq_desc though,
> >> > maybe you can suggest a better place for it (aside of the individual driver
> >> > code that is)?
> >>
> >> Well, if it should be done by the device/pm core then you want to
> >> store that information in the device related data structure.
> >>
> >> struct dev_pm_info might be the right place for it, but that's up to
> >> Rafael.
> >>
> >> So driver would set
> >>
> >>    dev->power.update_wakeirq_type = true;
> >>    dev->power.irq_type_normal = IRQ_TYPE_EDGE_BOTH;
> >>    dev->power.irq_type_sleep = IRQ_TYPE_EDGE_LOW;
> >>
> >> And the dev/PM core can issue the calls on suspend/resume.
> >
> > So I'd rather put that into the struct wakeup_source pointed to by
> > the wakeup pointer in struct dev_pm_info.  That would give us a mapping
> > between wakeup source objects and wakeup interrupts and which would make
> > a fair amount of sense in my view.
> >
> > Then, we could simply walk the list of wakeup source objects before
> > suspend_device_irqs() and call enable_irq_wake() etc. for all of the
> > interrupts in question without drivers having to worry about that.
> > We also could save the current IRQ type for them at that point and
> > restore it during resume.
> >
> > Of course, that would require some changes to wakeup_source_create()
> > and friends, but is probably worth doing.
> >
> > Still, before we start making those changes, here's a bunch of questions
> > to answer:
> >
> > (1) Say a wakeup interrupt is shared between two drivers and one of them
> >     asks for a different "IRQ type for sleep" than the other one.  How are
> >     we going to resolve such conflicts?
> >
> > (2) Can platforms place restrictions on the IRQ type to be used with a given
> >     line?  If so, how do we handle situations in which the requested
> >     "IRQ type for sleep" is different from what the given line can use?
> >     Do we need to resolve that at the struct wakeup_source creation time or
> >     can we do that later (during suspend?) and how?
> >
> > Rafael
> >
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-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.