linux-kernel - Re: [PATCH v2] drvier: usb: dwc3: Fix runtime PM trying to activate child device xxx.dwc3 but parent is not active

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Message-ID: <xbfvykzfi26pyaycd7efbqvmraxcu6zzgqjfxtk33wcsjsnnal@5e3g4pq5qcj3>
Date: Thu, 11 Sep 2025 18:52:47 +0800
From: Xu Yang <xu.yang_2@....com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: Ryan Zhou <ryanzhou54@...il.com>, 
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>, "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, 
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>, "rafael@...nel.org" <rafael@...nel.org>, 
	"royluo@...gle.com" <royluo@...gle.com>
Subject: Re: [PATCH v2] drvier: usb: dwc3: Fix runtime PM trying to activate
 child device xxx.dwc3 but parent is not active

Hi Ryan,

On Thu, Sep 11, 2025 at 01:32:47AM +0000, Thinh Nguyen wrote:
> On Wed, Sep 10, 2025, Ryan Zhou wrote:
> > Issue description:During the wake-up sequence, if the system invokes
> >  dwc3->resume and detects that the parent device of dwc3 is in a
> > runtime suspend state, the system will generate an error: runtime PM
> > trying to activate child device xxx.dwc3 but parent is not active.
> > 
> > Solution:At the dwc3->resume entry point, if the dwc3 controller
> > is detected in a suspended state, the function shall return
> > immediately without executing any further operations.
> > 
> > Signed-off-by: Ryan Zhou <ryanzhou54@...il.com>
> > ---
> >  drivers/usb/dwc3/core.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index 370fc524a468..06a6f8a67129 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -2687,6 +2687,9 @@ int dwc3_pm_resume(struct dwc3 *dwc)
> >  	struct device *dev = dwc->dev;
> >  	int		ret = 0;
> >  
> > +	if (pm_runtime_suspended(dev))
> > +		return ret;
> > +
> 
> Is this a documented behavior where the device should remain runtime
> suspend on system resume? I feel that that this should be configurable
> by the user or defined the PM core. I don't think we should change
> default behavior here just to workaround the issue that we're facing.
> 
> What if the user wants to keep the old behavior and resume up the device
> on system resume?

What about resume the device firstly if it's already runtime suspended when
call dwc3_pm_suspend(). Therefor, the old behavior can be kept and the issue
can be avoided.

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 370fc524a468..1b8dbb260017 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -2672,6 +2672,9 @@ int dwc3_pm_suspend(struct dwc3 *dwc)
        struct device *dev = dwc->dev;
        int             ret;

+       if (pm_runtime_suspended(dev))
+               pm_runtime_resume(dev);
+
        ret = dwc3_suspend_common(dwc, PMSG_SUSPEND);
        if (ret)
                return ret;

Thanks,
Xu Yang

> 
> BR,
> Thinh
> 
> >  	pinctrl_pm_select_default_state(dev);
> >  
> >  	pm_runtime_disable(dev);
> > -- 
> > 2.25.1
> >