linux-kernel - Re: [PATCH v4 1/3] PM / wakeirq: support enabling wake-up irq after runtime

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Date:   Wed, 27 Oct 2021 17:29:52 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
CC:     Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Linux PM" <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "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>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v4 1/3] PM / wakeirq: support enabling wake-up irq
 after runtime_suspend called

On Tue, 2021-10-26 at 17:39 +0200, Rafael J. Wysocki wrote:
> On Mon, Oct 25, 2021 at 9:02 AM Chunfeng Yun <
> chunfeng.yun@...iatek.com> wrote:
> > 
> > When the dedicated wake IRQ is level trigger, and it uses the
> > device's low-power status as the wakeup source, that means if the
> > device is not in low-power state, the wake IRQ will be triggered
> > if enabled; For this case, need enable the wake IRQ after running
> > the device's ->runtime_suspend() which make it enter low-power
> > state.
> > 
> > e.g.
> > Assume the wake IRQ is a low level trigger type, and the wakeup
> > signal comes from the low-power status of the device.
> > The wakeup signal is low level at running time (0), and becomes
> > high level when the device enters low-power state (runtime_suspend
> > (1) is called), a wakeup event at (2) make the device exit low-
> > power
> > state, then the wakeup signal also becomes low level.
> > 
> >                 ------------------
> >                |           ^     ^|
> > ----------------           |     | --------------
> >  |<---(0)--->|<--(1)--|   (3)   (2)    (4)
> > 
> > if enable the wake IRQ before running runtime_suspend during (0),
> > a wake IRQ will arise, it causes resume immediately;
> > it works if enable wake IRQ ( e.g. at (3) or (4)) after running
> > ->runtime_suspend().
> > 
> > This patch introduces a new status WAKE_IRQ_DEDICATED_REVERSE to
> > optionally support enabling wake IRQ after running
> > ->runtime_suspend().
> > 
> > Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> 
> I don't really have anything to add regarding the code.
> 
> The kerneldoc comments could be improved, but I can take care of this
> when applying the patch.
Ok, thanks
> 
> Please collect ACKs for the remaining 2 patches in the series and I
> will pick up all three.
The files (mtu3_plat.c, xhci-mtk.c) modified by other 2 patches are
maintained by myself, please pick up them, thanks a lot.

> 
> Thanks!
> 
> > ---
> > v4: changes according to Rafael's suggestions
> >     1. rename new flag as WAKE_IRQ_DEDICATED_REVERSE;
> >     2. add __dev_pm_set_dedicated_wake_irq() with flag parameter,
> > then
> >        rebuild dev_pm_set_dedicated_wake_irq() and add new api
> >        dev_pm_set_dedicated_wake_irq_reverse();
> >     3. rename the new added parameter as cond_disable in
> >        dev_pm_disable_wake_irq_check(), and also simplify its flow;
> >     4. modify some comments
> > 
> > v3: add new status suggested by Rafael
> > 
> > v2: add more commit message
> > 
> >   Use the falling edge trigger interrupt suggested by Ikjoon [1],
> > it
> > works well at firstly when only use this related wakeup source, but
> > encounter issues if use other wakeup sources to wakeup platform as
> > below steps:
> > 1. use another wakeup source to wake up the suspended system;
> > 2. the consumer's resume() will be called, and exits sleep state;
> > 3. the consumer's wakeup signal will fall into low level, due to
> >    currently the wakeup irq is disabled, the wake-irq is pending;
> > 4. the consumer tries to enter runtime suspend, but there is a
> >    pending wakeup irq, so will resume again, this will repeat
> >    endlessly.
> > 
> >   Send out the patch again for further discussion.
> > 
> > [1]: https://patchwork.kernel.org/patch/12190407
> > 
> > ---
> >  drivers/base/power/power.h   |   7 ++-
> >  drivers/base/power/runtime.c |   6 ++-
> >  drivers/base/power/wakeirq.c | 101 +++++++++++++++++++++++++++--
> > ------
> >  include/linux/pm_wakeirq.h   |   9 +++-
> >  4 files changed, 96 insertions(+), 27 deletions(-)
[...]
> >