Re: [PATCH v4] usb: gadget: udc: Handle gadget_connect failure during bind operation

[Krishna Kurapati PSSNV]

On 9/27/2023 1:36 AM, Krishna Kurapati PSSNV wrote:
> > >   drivers/usb/gadget/udc/core.c | 23 +++++++++++++++++++----
> > >   1 file changed, 19 insertions(+), 4 deletions(-)
> > >
> > >   static void vbus_event_work(struct work_struct *work)
> > > @@ -1604,12 +1608,23 @@ static int gadget_bind_driver(struct device 
> > > *dev)
> > >       }
> > >       usb_gadget_enable_async_callbacks(udc);
> > >       udc->allow_connect = true;
> > > -    usb_udc_connect_control_locked(udc);
> > > +    ret = usb_udc_connect_control_locked(udc);
> > > +    if (ret) {
> > > +        mutex_unlock(&udc->connect_lock);
> > > +        goto err_connect_control;
> > > +    }
> > > +
> > >       mutex_unlock(&udc->connect_lock);
> > >       kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
> > >       return 0;
> > > + err_connect_control:
> > > +    usb_gadget_disable_async_callbacks(udc);
> > > +    if (gadget->irq)
> > > +        synchronize_irq(gadget->irq);
> > > +    usb_gadget_udc_stop_locked(udc);
> >
> > Not good -- usb_gadget_udc_stop_locked() expects you to be holding
> > udc->connect_lock, but you just dropped the lock!  Also, you never set
> > udc->allow_connect back to false.
> >
> > You should move the mutex_unlock() call from inside the "if" statement
> > to down here, and add a line for udc->allow_connect.
>
> Hi Alan,
>
>   Thanks for the review. Will push v5 addressing the changes.
Hi Alan,

I tried out the following diff:

-       usb_udc_connect_control_locked(udc);
+       ret = usb_udc_connect_control_locked(udc);
+       if (ret)
+               goto err_connect_control;
+
        mutex_unlock(&udc->connect_lock);

        kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
        return 0;

+ err_connect_control:
+       udc->allow_connect = false;
+       usb_gadget_disable_async_callbacks(udc);
+       if (gadget->irq)
+               synchronize_irq(gadget->irq);
+       usb_gadget_udc_stop_locked(udc);
+       mutex_unlock(&udc->connect_lock);
+

If I clear UDC and fail dwc3 soft reset on purpose, I see UDC_store failing:

#echo a600000.usb > /sys/kernel/config/usb_gadget/g1/UDC
[  127.394087] dwc3 a600000.usb: request 000000003f43f907 was not queued 
to ep0out
[  127.401637] udc a600000.usb: failed to start g1: -110
[  127.406841] configfs-gadget.g1: probe of gadget.0 failed with error -110
[  127.413809] UDC core: g1: couldn't find an available UDC or it's busy

The same output came when I tested v4 as well. Every time soft_reset 
would fail when I try to write to UDC, UDC_store fails and above log 
will come up. Can you help confirm if the diff above is proper as I 
don't see any diff in the logs in v4 and about to push v5.

Regards,
Krishna,