[PATCH v2 2/8] usb: xhci: Better error handling in abort_td()

[Hector Martin]

If the xHC has a problem with our STOP ENDPOINT command, it is likely to
return a completion directly instead of first a transfer event for the
in-progress transfer. Handle that more gracefully.

We still BUG() on the error code, but at least we don't end up timing
out on the event and ending up with unexpected event errors.

Signed-off-by: Hector Martin <marcan at marcan.st>
---
 drivers/usb/host/xhci-ring.c | 34 ++++++++++++++++++++++------------
 include/usb/xhci.h           |  2 ++
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index d0960812a47b..d21e76e0bdb6 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -466,7 +466,8 @@ union xhci_trb *xhci_wait_for_event(struct xhci_ctrl *ctrl, trb_type expected)
 			continue;
 
 		type = TRB_FIELD_TO_TYPE(le32_to_cpu(event->event_cmd.flags));
-		if (type == expected)
+		if (type == expected ||
+		    (expected == TRB_NONE && type != TRB_PORT_STATUS))
 			return event;
 
 		if (type == TRB_PORT_STATUS)
@@ -544,27 +545,36 @@ static void abort_td(struct usb_device *udev, int ep_index)
 	struct xhci_ctrl *ctrl = xhci_get_ctrl(udev);
 	struct xhci_ring *ring =  ctrl->devs[udev->slot_id]->eps[ep_index].ring;
 	union xhci_trb *event;
+	trb_type type;
 	u64 addr;
 	u32 field;
 
 	xhci_queue_command(ctrl, 0, udev->slot_id, ep_index, TRB_STOP_RING);
 
-	event = xhci_wait_for_event(ctrl, TRB_TRANSFER);
+	event = xhci_wait_for_event(ctrl, TRB_NONE);
 	if (!event)
 		return;
 
-	field = le32_to_cpu(event->trans_event.flags);
-	BUG_ON(TRB_TO_SLOT_ID(field) != udev->slot_id);
-	BUG_ON(TRB_TO_EP_INDEX(field) != ep_index);
-	BUG_ON(GET_COMP_CODE(le32_to_cpu(event->trans_event.transfer_len
-		!= COMP_STOP)));
-	xhci_acknowledge_event(ctrl);
+	type = TRB_FIELD_TO_TYPE(le32_to_cpu(event->event_cmd.flags));
+	if (type == TRB_TRANSFER) {
+		field = le32_to_cpu(event->trans_event.flags);
+		BUG_ON(TRB_TO_SLOT_ID(field) != udev->slot_id);
+		BUG_ON(TRB_TO_EP_INDEX(field) != ep_index);
+		BUG_ON(GET_COMP_CODE(le32_to_cpu(event->trans_event.transfer_len
+			!= COMP_STOP)));
+		xhci_acknowledge_event(ctrl);
 
-	event = xhci_wait_for_event(ctrl, TRB_COMPLETION);
-	if (!event)
-		return;
+		event = xhci_wait_for_event(ctrl, TRB_COMPLETION);
+		if (!event)
+			return;
+		type = TRB_FIELD_TO_TYPE(le32_to_cpu(event->event_cmd.flags));
 
-	BUG_ON(TRB_TO_SLOT_ID(le32_to_cpu(event->event_cmd.flags))
+	} else {
+		printf("abort_td: Expected a TRB_TRANSFER TRB first\n");
+	}
+
+	BUG_ON(type != TRB_COMPLETION ||
+		TRB_TO_SLOT_ID(le32_to_cpu(event->event_cmd.flags))
 		!= udev->slot_id || GET_COMP_CODE(le32_to_cpu(
 		event->event_cmd.status)) != COMP_SUCCESS);
 	xhci_acknowledge_event(ctrl);
diff --git a/include/usb/xhci.h b/include/usb/xhci.h
index 4a4ac10229ac..04d16a256bbd 100644
--- a/include/usb/xhci.h
+++ b/include/usb/xhci.h
@@ -901,6 +901,8 @@ union xhci_trb {
 
 /* TRB type IDs */
 typedef enum {
+	/* reserved, used as a software sentinel */
+	TRB_NONE = 0,
 	/* bulk, interrupt, isoc scatter/gather, and control data stage */
 	TRB_NORMAL = 1,
 	/* setup stage for control transfers */

-- 
2.41.0