linux-kernel - Re: [RFC] PM: core: Add pm_wakeup_pending check in device suspend

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Date:   Thu, 22 Sep 2022 08:34:29 +0800
From:   ChiYuan Huang <u0084500@...il.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>,
        Kees Cook <keescook@...omium.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>, cy_huang@...htek.com,
        gene_chen@...htek.com, Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] PM: core: Add pm_wakeup_pending check in device suspend_noirq

Rafael J. Wysocki <rafael@...nel.org> 於 2022年9月22日 週四 凌晨2:13寫道：
>
> On Fri, Sep 16, 2022 at 4:15 AM cy_huang <u0084500@...il.com> wrote:
> >
> > From: ChiYuan Huang <cy_huang@...htek.com>
> >
> > In 'dpm_suspend_noirq', it will do the sychronized_irq to guarantee all
> > irqs are all done, and then do any wakeup flag set.
> >
> > For some peripherial deivces like as I2C/SPI, to speed up the irq handling,
> > it may use 'pm_stay_awake' and really handle in another thread context like
> > as workqueue.
> >
> > But in mem suspend flow, after 'dpm_suspend_noirq" stage, the next
> > 'pm_wakeup_pending' check will be at 'syscore_suspend'.
> >
> > The checkpoint seems too late and cause I2C/SPI fail during 'noirq' to
> > 'syscore_suspend'
>
> What exactly do you mean by "fail" here?
For the below case
Once the adapter is marked as 'Suspend', any i2c_xfer or spi_xfer will
directly return 'ESHUTDOWN".
There's no real I/O transferred, only the direct returned error code.

>
> >. But some adapter was already be marked as 'suspended'
> > at 'noirq' callback, any I2C/SPI xfer will return the error flag '-ESHUTDOWN'.
> >
> > After the code trace, it seems all device callback will do 'pm_wakeup_pending'
> > check, except 'noirq'.
> >
> > This patch is to add 'pm_wakeup_pending' check in 'noirq' sage to prevent this
> > kind of usage.
> >
> > Signed-off-by: ChiYuan Huang <cy_huang@...htek.com>
> > ---
> > Hi,
> >
> > Is there any rule to define when I2C/SPI host controller need to mark adapter as
> > 'suspended'?
> >
> > I trace 'drivers/i2c/buses'.It seems there's no common rule, Some are 'suspend',
> > others may did it at 'suspend_noirq'.
> >
> > ---
> >  drivers/base/power/main.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > index c501392..7cd7dc5 100644
> > --- a/drivers/base/power/main.c
> > +++ b/drivers/base/power/main.c
> > @@ -1210,6 +1210,11 @@ static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool a
> >         if (async_error)
> >                 goto Complete;
> >
> > +       if (pm_wakeup_pending()) {
> > +               async_error = -EBUSY;
> > +               goto Complete;
> > +       }
> > +
> >         if (dev->power.syscore || dev->power.direct_complete)
> >                 goto Complete;
> >
> > --
> > 2.7.4
> >