[PATCH 2/2] usb: xhci: Warn about suspected "start-stop" bugs in HCs

[Michal Pecio <michal.pecio@gmail.com>]

NEC controllers have a bug, where stopping an endpoint soon after it
has been restarted doesn't quite work as expected. This forces us to
track whether each Stop Endpoint command is expected to fail or not.

Reuse this infrastracture to warn about similar bugs on other chips,
if any are found.

Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
---
 drivers/usb/host/xhci-ring.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index c0efb4d34ab9..c326b86d713c 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1186,8 +1186,11 @@ static void xhci_handle_cmd_stop_ep(struct xhci_hcd *xhci, int slot_id,
 			 * So keep retrying until the command clearly succeeds.
 			 * Not clear what to do if other HCs have similar bugs.
 			 */
-			if (!(xhci->quirks & XHCI_NEC_HOST))
+			if (!(xhci->quirks & XHCI_NEC_HOST)) {
+				xhci_warn(xhci, "Unhandled Stop Endpoint failure on slot %d ep_index %d\n",
+						slot_id, ep_index);
 				break;
+			}
 			fallthrough;
 
 		case EP_STATE_RUNNING:
-- 
2.43.0