usb: dwc3: gadget: Give back staled requests

If a request is dequeued, the transfer is cancelled. Give back all
the started requests.

In most scenarios, the function driver dequeues all requests of a
transfer when there's a failure. If the function driver follows this,
then it's fine. If not, then we'd be skipping TRBs at different points
within the dequeue and enqueue pointers, making dequeue/enqueue pointers
useless. To enforce and make sure that we're properly skipping TRBs,
cancel all the started requests and give back all the cancelled requests
to the function drivers.
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/dwc3/gadget.c

@@ -1560,6 +1560,11 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep *ep,
 
 	spin_lock_irqsave(&dwc->lock, flags);
 
+	list_for_each_entry(r, &dep->cancelled_list, list) {
+		if (r == req)
+			goto out0;
+	}
+
 	list_for_each_entry(r, &dep->pending_list, list) {
 		if (r == req)
 			break;
@@ -1571,13 +1576,21 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep *ep,
 				break;
 		}
 		if (r == req) {
+			struct dwc3_request *t;
+
 			/* wait until it is processed */
 			dwc3_stop_active_transfer(dep, true, true);
 
 			if (!r->trb)
 				goto out0;
 
-			dwc3_gadget_move_cancelled_request(req);
+			/*
+			 * Remove any started request if the transfer is
+			 * cancelled.
+			 */
+			list_for_each_entry_safe(r, t, &dep->started_list, list)
+				dwc3_gadget_move_cancelled_request(r);
+
 			if (dep->flags & DWC3_EP_TRANSFER_STARTED)
 				goto out0;
 			else