usb: dwc3: Add error logs for unknown endpoint events

In cases where the controller somehow fails to write to event buffer
memory (e.g. due to incorrect MMU config), the driver would receive
all-zero dwc3 events. However, the abnormal event is silently dropped
as a regular ep0out event.
Add error logs when an unknown endpoint event is received to highlight
the anomaly.
Signed-off-by: Roy Luo <royluo@google.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20230504000129.728316-1-royluo@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/ep0.c

@@ -1207,5 +1207,8 @@ void dwc3_ep0_interrupt(struct dwc3 *dwc,
 			dep->flags &= ~DWC3_EP_TRANSFER_STARTED;
 		}
 		break;
+	default:
+		dev_err(dwc->dev, "unknown endpoint event %d\n", event->endpoint_event);
+		break;
 	}
 }

drivers/usb/dwc3/gadget.c

@@ -3803,6 +3803,9 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
 		break;
 	case DWC3_DEPEVT_RXTXFIFOEVT:
 		break;
+	default:
+		dev_err(dwc->dev, "unknown endpoint event %d\n", event->endpoint_event);
+		break;
 	}
 }