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

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Date:   Wed, 21 Sep 2022 20:13:29 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     cy_huang <u0084500@...il.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        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

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?

>. 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
>