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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250912213604.eoftwe6j67e5o3z2@synopsys.com>
Date: Fri, 12 Sep 2025 21:36:10 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: ryan zhou <ryanzhou54@...il.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.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

On Thu, Sep 11, 2025, ryan zhou wrote:
> Thinh Nguyen <Thinh.Nguyen@...opsys.com> 于2025年9月11日周四 09:32写道：
> >
> > 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.
> 
> No documentation was found, but modifying the runtime suspend state
> after wakeup from sleep seems unnecessary if the device was already
> in runtime suspend before sleep.
> 
> > What if the user wants to keep the old behavior and resume up the device
> > on system resume?

> For USB devices, RPM resume should be initiated by plug/unplug events,
> not PM resume when the device is physically disconnected.
> 

Why not? This resume will also apply for host right? The host can be
woken up by a remote-wake signal that triggers a pm_resume. The user may
expect the host to resume on pm_resume.

We may implement device hibernation in the future where RPM resume is
relevant more than just plug/unplug events.

BR,
Thinh