usb: phy: generic: Handle late registration of gadget

It is possible for the VBUS detect GPIO interrupt to occur before
nop_set_peripheral() is called, in which case otg->gadget is NULL.
Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/phy/phy-generic.c

@@ -118,7 +118,8 @@ static irqreturn_t nop_gpio_vbus_thread(int irq, void *data)
 		status = USB_EVENT_VBUS;
 		otg->state = OTG_STATE_B_PERIPHERAL;
 		nop->phy.last_event = status;
-		usb_gadget_vbus_connect(otg->gadget);
+		if (otg->gadget)
+			usb_gadget_vbus_connect(otg->gadget);
 
 		/* drawing a "unit load" is *always* OK, except for OTG */
 		nop_set_vbus_draw(nop, 100);
@@ -128,7 +129,8 @@ static irqreturn_t nop_gpio_vbus_thread(int irq, void *data)
 	} else {
 		nop_set_vbus_draw(nop, 0);
 
-		usb_gadget_vbus_disconnect(otg->gadget);
+		if (otg->gadget)
+			usb_gadget_vbus_disconnect(otg->gadget);
 		status = USB_EVENT_NONE;
 		otg->state = OTG_STATE_B_IDLE;
 		nop->phy.last_event = status;
@@ -184,7 +186,10 @@ static int nop_set_peripheral(struct usb_otg *otg, struct usb_gadget *gadget)
 	}
 
 	otg->gadget = gadget;
-	otg->state = OTG_STATE_B_IDLE;
+	if (otg->state == OTG_STATE_B_PERIPHERAL)
+		usb_gadget_vbus_connect(gadget);
+	else
+		otg->state = OTG_STATE_B_IDLE;
 	return 0;
 }