Re: [PATCH net v1 1/1] net: usb: asix: ax88772: drop phylink use in PM to avoid MDIO runtime PM wakeups

Russell King (Oracle)
2025-09-12T14:38:10Z

On Fri, Sep 12, 2025 at 10:29:47AM -0400, Alan Stern wrote:
> On Fri, Sep 12, 2025 at 09:33:05AM +0100, Russell King (Oracle) wrote:
> > On Thu, Sep 11, 2025 at 10:30:09PM -0400, Alan Stern wrote:
> > > The USB subsystem uses only one pair of callbacks for suspend and resume
> > > because USB hardware has only one suspend state. However, the callbacks
> > > do get an extra pm_message_t parameter which they can use to distinguish
> > > between system sleep transitions and runtime PM transitions.
> >
> > Unfortunately, this isn't the case. While a struct usb_device_driver's
> > suspend()/resume() methods get the pm_message_t, a struct usb_driver's
> > suspend()/resume() methods do not:
> >
> > static int usb_resume_interface(struct usb_device *udev,
> > struct usb_interface *intf, pm_message_t msg, int reset_resume)
> > {
> > struct usb_driver *driver;
> > ...
> > if (reset_resume) {
> > if (driver->reset_resume) {
> > status = driver->reset_resume(intf);
> > ...
> > } else {
> > status = driver->resume(intf);
> >
> > vs
> >
> > static int usb_resume_device(struct usb_device *udev, pm_message_t msg)
> > {
> > struct usb_device_driver *udriver;
> > ...
> > if (status == 0 && udriver->resume)
> > status = udriver->resume(udev, msg);
> >
> > and in drivers/net/usb/asix_devices.c:
> >
> > static struct usb_driver asix_driver = {
> > ...
> > .suspend = asix_suspend,
> > .resume = asix_resume,
> > .reset_resume = asix_resume,
> >
> > where asix_resume() only takes one argument:
> >
> > static int asix_resume(struct usb_interface *intf)
> > {
>
> Your email made me go back and check the code more carefully, and it
> turns out that we were both half-right. :-)
>
> The pm_message_t argument is passed to the usb_driver's ->suspend
> callback in usb_suspend_interface(), but not to the ->resume callback in
> usb_resume_interface(). Yes, it's inconsistent.
>
> I suppose the API could be changed, at the cost of updating a lot of
> drivers. But it would be easier if this wasn't necessary, if there was
> some way to work around the problem. Unfortunately, I don't know
> anything about how the network stack handles suspend and resume, or
> what sort of locking it requires, so I can't offer any suggestions.

I, too, am unable to help further as I have no bandwidth available
to deal with this. Sorry.

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