On Wed, May 17, 2023 at 10:19:25AM -0700, Badhri Jagan Sridharan wrote:
> On Wed, May 17, 2023 at 7:44 AM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Wed, May 17, 2023 at 11:59:55AM +0000, Badhri Jagan Sridharan wrote:
> > > chipidea udc calls usb_udc_vbus_handler from udc_start gadget
> > > ops causing a deadlock. Avoid this by offloading usb_udc_vbus_handler
> > > processing.
> >
> > Surely that is the wrong approach.
> >
> > The real problem here is that usb_udc_vbus_handler() gets called from
> > within a udc_start routine. But this is totally unnecessary, because
> > the UDC core will call usb_udc_connect_control_locked() itself, later on
> > during gadget_bind_driver().
>
> Hi Alan,
>
> usb_udc_vbus_handler sets the udc->vbus flag as well apart from
> calling usb_udc_connect_control_locked(). So, removing usb_udc_vbus_handler
> from chip specific start callback might prevent the controller from
> starting.
>
> void usb_udc_vbus_handler(struct usb_gadget *gadget, bool status)
> {
> struct usb_udc *udc = gadget->udc;
>
> mutex_lock(&udc->connect_lock);
> if (udc) {
> udc->vbus = status;
> usb_udc_connect_control_locked(udc);
Then add "udc->vbus = true;" at the appropriate spot in
gadget_bind_driver().
Alan Stern
PS: I just noticed that in max3420_udc.c, the max_3420_vbus_handler()
function calls usb_udc_vbus_handler() from within an interrupt handler.
This won't work, since interrupt handlers aren't allowed to sleep and
therefore can't lock mutexes.
