linux-kernel - Re: [PATCH 1/6] PM: runtime: enable wake irq after runtime

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Date:   Fri, 9 Apr 2021 09:53:31 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
CC:     Rob Herring <robh+dt@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        "open list:ULTRA-WIDEBAND (UWB) SUBSYSTEM:" 
        <linux-usb@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Tony Lindgren <tony@...mide.com>,
        Tianping Fang <tianping.fang@...iatek.com>,
        Eddie Hung <eddie.hung@...iatek.com>,
        "Ikjoon Jang" <ikjn@...omium.org>,
        Nicolas Boichat <drinkcat@...omium.org>
Subject: Re: [PATCH 1/6] PM: runtime: enable wake irq after runtime_suspend
 hook called

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@...iatek.com> 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.
It may happen if the trigger level only keeps a very short time, and the
interrupt controller can't process it timely, but I don't think it
follow the level trigger mechanism, the HW should latch it until the ISR
is called. right?

> 
> > enable wake irq after calling runtime_suspend, e.g. at (3) or (4),
> > will works.
> >
> > This patch seems no side effect on edge trigger wake irq.
> >
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > ---
> >  drivers/base/power/runtime.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> > index a46a7e30881b..796739a015a5 100644
> > --- a/drivers/base/power/runtime.c
> > +++ b/drivers/base/power/runtime.c
> > @@ -619,12 +619,12 @@ static int rpm_suspend(struct device *dev, int rpmflags)
> >         __update_runtime_status(dev, RPM_SUSPENDING);
> >
> >         callback = RPM_GET_CALLBACK(dev, runtime_suspend);
> > -
> > -       dev_pm_enable_wake_irq_check(dev, true);
> >         retval = rpm_callback(callback, dev);
> >         if (retval)
> >                 goto fail;
> >
> > +       dev_pm_enable_wake_irq_check(dev, true);
> > +
> >   no_callback:
> >         __update_runtime_status(dev, RPM_SUSPENDED);
> >         pm_runtime_deactivate_timer(dev);
> > @@ -659,7 +659,6 @@ static int rpm_suspend(struct device *dev, int rpmflags)
> >         return retval;
> >
> >   fail:
> > -       dev_pm_disable_wake_irq_check(dev);
> >         __update_runtime_status(dev, RPM_ACTIVE);
> >         dev->power.deferred_resume = false;
> >         wake_up_all(&dev->power.wait_queue);
> > --
> > 2.18.0
> >