Re: [PATCH 1/6] PM: runtime: enable wake irq after runtime_suspend hook called

[Rafael J. Wysocki]

On Fri, Apr 9, 2021 at 10:36 AM Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx> wrote:
>
> On Fri, 2021-04-09 at 08:39 +0300, Tony Lindgren wrote:
> > * Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx> [210409 01:54]:
> > > On Thu, 2021-04-08 at 19:41 +0200, Rafael J. Wysocki wrote:
> > > > On Thu, Apr 8, 2021 at 11:35 AM Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx> wrote:
> > > > >
> > > > > When the dedicated wake irq is level trigger, enable it before
> > > > > calling runtime_suspend, will trigger an interrupt.
> > > > >
> > > > > e.g.
> > > > > for a low level trigger type, it's low level at running time (0),
> > > > > and becomes high level when enters suspend (runtime_suspend (1) is
> > > > > called), a wakeup signal at (2) make it become low level, wake irq
> > > > > will be triggered.
> > > > >
> > > > >                 ------------------
> > > > >                |           ^     ^|
> > > > > ----------------           |     | --------------
> > > > >  |<---(0)--->|<--(1)--|   (3)   (2)    (4)
> > > > >
> > > > > if we enable the wake irq before calling runtime_suspend during (0),
> > > > > an interrupt will arise, it causes resume immediately;
> > > >
> > > > But that's necessary to avoid missing a wakeup interrupt, isn't it?
> > > That's also what I worry about.
> >
> > Yeah sounds like this patch will lead into missed wakeirqs.
> If miss level trigger wakeirqs, that means HW doesn't latch it? is it HW
> limitation?

If it's level-triggered, it won't be missed, but then it is just
pointless to suspend the device when wakeup is being signaled in the
first place.

I'm not sure if I understand the underlying problem correctly.  Is it
about addressing spurious wakeups?