linux-kernel - Re: [PATCH] PM / runtime: Drop children check from __pm_runtime_set

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Message-ID: <CAPDyKFoG2-mVGDtzPyg2FDVbXnsWGy543craKqeBVE_awKpf8Q@mail.gmail.com>
Date:   Wed, 29 Nov 2017 10:24:51 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        USB list <linux-usb@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH] PM / runtime: Drop children check from __pm_runtime_set_status()

On 29 November 2017 at 09:21, Yoshihiro Shimoda
<yoshihiro.shimoda.uh@...esas.com> wrote:
> Hi,
>
>> From: Ulf Hansson, Sent: Wednesday, November 29, 2017 2:23 AM
>>
>> On 28 November 2017 at 13:48, Yoshihiro Shimoda
>> <yoshihiro.shimoda.uh@...esas.com> wrote:
>> > Hi Geert-san,
>> >
>> >> From: Geert Uytterhoeven, Sent: Tuesday, November 28, 2017 7:58 PM
>> >>
>> >> Hi Rafael, Shimoda-san,
>> >>
>> >> On Sun, Nov 12, 2017 at 1:27 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> >> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> <snip>
>> >> JFTR, this triggered before during system resume on e.g. Salvator-XS with
>> >> R-Car H3:
>> >>
>> >>     ohci-platform ee080000.usb: runtime PM trying to suspend device
>> >> but active child
>> >>     phy_rcar_gen3_usb2 ee080200.usb-phy: runtime PM trying to suspend
>> >> device but active child
>> >>     ohci-platform ee0c0000.usb: runtime PM trying to suspend device
>> >> but active child
>> >>     ohci-platform ee0a0000.usb: runtime PM trying to suspend device
>> >> but active child
>> >>     phy_rcar_gen3_usb2 ee0c0200.usb-phy: runtime PM trying to suspend
>> >> device but active child
>> >>     phy_rcar_gen3_usb2 ee0a0200.usb-phy: runtime PM trying to suspend
>> >> device but active child
>> >>
>> >> so this was an existing issue with USB before.
>> >
>> > Thank you for the report!
>> > I know that, but since this didn't cause any trouble until now,
>> > I postponed to investigate the issue... But, I investigate it today.
>> > I don't find the root cause yet. However, it seems related to usb host and/or usb core.
>> > --> USB host related devices' child_count will be 1 in suspend timing.
>> >  --> I guess remote wakeup feature is enabled? But, I don't find the point yet.
>>
>> I am guessing the issue is triggered by genpd in the suspend noirq
>> phase (genpd_suspend_noirq()). In there,  there is a call to
>> pm_runtime_force_suspend() (which calls pm_runtime_set_suspended() and
>> which triggered the earlier error messages being printed).
>>
>> The reason why genpd calls pm_runtime_force_suspend(), is because when
>> validating wakeup configurations for the device "if
>> (dev->power.wakeup_path && genpd_is_active_wakeup(genpd))", it's
>> thinks wakeup isn't configured while it probably should be.
>>
>> An additional note, only when genpd has the GENPD_FLAG_PM_CLK set,
>> which makes the genpd->dev_ops.stop|start() being assigned, genpd
>> calls pm_runtime_force_suspend() - else it doesn't.
>>
>> Perhaps try out the series I recently posted improving the code
>> dealing with wakeups in genpd and the PM core:
>> https://www.spinics.net/lists/linux-renesas-soc/msg20122.html
>> To that, you need to set the new flag (invented in the above series)
>> DPM_FLAG_IN_BAND_WAKEUP in the driver that configures wakeup of its
>> device.
>>
>> Hope this helps!
>
> Thank you for the comments!
> I tried DPM_FLAG_IN_BAND_WAKEUP, but the issue still exists.
> I added the flag in the [eo]hci-platform driver and usb/core/driver.c.
> I also added the flag in the phy_rcar_gen3_usb2 driver except usb host drivers.

First, did you confirm that genpd was used? Then for what device?

Second, did you check the call to pm_runtime_force_suspend() called by
genpd, is the reason to the error messages?

Third, it should be sufficient to add DPM_FLAG_IN_BAND_WAKEUP for the
driver that is actually dealing with the wakeup. Although, does this
driver's system ->suspend() callback check device_may_wakeup(), before
it decides to enable wakeup?
If not, the PM core and genpd don't notice that wakeup is enabled for
the device.

>
>> > The renesas_usbhs also uses the phy_rcar_gen3_usb2 driver.
>> > --> If I only used the renesas_usbhs driver (in other words, I don't install
>> >     [eo]hci-{hcd,platform} drivers), the issue disappeared.
>> >  --> So, I think the phy_rcar_gen3_usb2 driver doesn't cause this issue.
>> >     (But, it is possible to be related though.)
>> >
>> > I'll continue to investigate this issue tomorrow.
>>
>> Please keep me posted, I am interested about the why the problem exists. :-)
>
> Sure! :)

Great, thanks.

Kind regards
Uffe