usb: dwc3: gadget: fix isoc END TRANSFER Condition

There were still some corner cases where isoc transfer was not able to
restart, specially when missed isoc does not happen , and in fact gadget does
not queue any new request during giveback.

Cleanup function calls giveback first, which provides a way to queue
another request to gadget. But gadget did not had any data. So , it did
not call ep_queue. To twist it further, gadget did not queue till
cleanup for last queued TRB is called. If we ever reach this scenario,
we must call END TRANSFER, so that we receive a new  xfernotready with
information about current microframe number.

Also insure that there is no request submitted to core when issuing END
TRANSFER.

Cc: <stable@vger.kernel.org> # v3.8
Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -1089,7 +1089,10 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
 		 * notion of current microframe.
 		 */
 		if (usb_endpoint_xfer_isoc(dep->endpoint.desc)) {
-			dwc3_stop_active_transfer(dwc, dep->number);
+			if (list_empty(&dep->req_queued)) {
+				dwc3_stop_active_transfer(dwc, dep->number);
+				dep->flags = DWC3_EP_ENABLED;
+			}
 			return 0;
 		}
 
@@ -1727,10 +1730,20 @@ static int dwc3_cleanup_done_reqs(struct dwc3 *dwc, struct dwc3_ep *dep,
 			break;
 	} while (1);
 
-	if (list_empty(&dep->req_queued) &&
-			(dep->flags & DWC3_EP_MISSED_ISOC)) {
-		dwc3_stop_active_transfer(dwc, dep->number);
-		dep->flags &= ~DWC3_EP_MISSED_ISOC;
+	if (usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
+			list_empty(&dep->req_queued)) {
+		if (list_empty(&dep->request_list)) {
+			/*
+			 * If there is no entry in request list then do
+			 * not issue END TRANSFER now. Just set PENDING
+			 * flag, so that END TRANSFER is issued when an
+			 * entry is added into request list.
+			 */
+			dep->flags = DWC3_EP_PENDING_REQUEST;
+		} else {
+			dwc3_stop_active_transfer(dwc, dep->number);
+			dep->flags = DWC3_EP_ENABLED;
+		}
 		return 1;
 	}