usb: xhci: adjust empty TD list handling in handle_tx_event()

Introduce an initial check for an empty list prior to entering the while
loop. Which enables, the implementation of distinct warnings to
differentiate between scenarios where the list is initially empty and
when it has been emptied during processing skipped isoc TDs.

These adjustments not only simplifies the large while loop, but also
facilitates future enhancements to the handle_tx_event() function.

Signed-off-by: Niklas Neronin <[email protected]>
Signed-off-by: Mathias Nyman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Epicurius

drivers/usb/host/xhci-ring.c

@@ -2761,35 +2761,25 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		return 0;
 	}
 
-	do {
-		/* This TRB should be in the TD at the head of this ring's
-		 * TD list.
+	if (list_empty(&ep_ring->td_list)) {
+		/*
+		 * Don't print wanings if ring is empty due to a stopped endpoint generating an
+		 * extra completion event if the device was suspended. Or, a event for the last TRB
+		 * of a short TD we already got a short event for. The short TD is already removed
+		 * from the TD list.
 		 */
-		if (list_empty(&ep_ring->td_list)) {
-			/*
-			 * Don't print wanings if it's due to a stopped endpoint
-			 * generating an extra completion event if the device
-			 * was suspended. Or, a event for the last TRB of a
-			 * short TD we already got a short event for.
-			 * The short TD is already removed from the TD list.
-			 */
-
-			if (!(trb_comp_code == COMP_STOPPED ||
-			      trb_comp_code == COMP_STOPPED_LENGTH_INVALID ||
-			      ep_ring->last_td_was_short)) {
-				xhci_warn(xhci, "WARN Event TRB for slot %u ep %d with no TDs queued?\n",
-					  slot_id, ep_index);
-			}
-			if (ep->skip) {
-				ep->skip = false;
-				xhci_dbg(xhci, "td_list is empty while skip flag set. Clear skip flag for slot %u ep %u.\n",
-					 slot_id, ep_index);
-			}
-
-			td = NULL;
-			goto check_endpoint_halted;
+		if (trb_comp_code != COMP_STOPPED &&
+		    trb_comp_code != COMP_STOPPED_LENGTH_INVALID &&
+		    !ep_ring->last_td_was_short) {
+			xhci_warn(xhci, "Event TRB for slot %u ep %u with no TDs queued\n",
+				  slot_id, ep_index);
 		}
 
+		ep->skip = false;
+		goto check_endpoint_halted;
+	}
+
+	do {
 		td = list_first_entry(&ep_ring->td_list, struct xhci_td,
 				      td_list);
 
@@ -2800,7 +2790,14 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 
 			if (ep->skip && usb_endpoint_xfer_isoc(&td->urb->ep->desc)) {
 				skip_isoc_td(xhci, td, ep, status);
-				continue;
+				if (!list_empty(&ep_ring->td_list))
+					continue;
+
+				xhci_dbg(xhci, "All TDs skipped for slot %u ep %u. Clear skip flag.\n",
+					 slot_id, ep_index);
+				ep->skip = false;
+				td = NULL;
+				goto check_endpoint_halted;
 			}
 
 			/*