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

ryan zhou
2025-09-11T13:57:06Z

Rafael J. Wysocki <rafael@kernel.org> 于2025年9月11日周四 19:36写道：
>
> On Thu, Sep 11, 2025 at 12:58 PM Xu Yang <xu.yang_2@nxp.com> wrote:
> >
> > 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@gmail.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);
>
> You can just call pm_runtime_resume() here without the preliminary check.

If the device is active before sleep, skip runtime_resume after wakeup
and just call dwc3->suspend.

Thanks，

Ryan