[PATCH 9/9] usb: xhci: Clean up and rename bad stream event handler

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

Function handle_transferless_tx_event() pretends that it sometimes
deals with certain isochronous events, but it really doesn't.

All isochronous events are handled in the big switch statement of
handle_tx_event(). The above function is never called on isoch EPs
because xhci_dma_to_transfer_ring() never returns NULL on those.

The only conceivable way we could end up there is if an isoch EP
is marked EP_HAS_STREAMS or its ring pointer is NULL, or we get an
X-run event on a non-isoch EP. Either way it's a blatant bug, so
don't "handle" this with a no-op, but print the default warning.

The actual meaningful work done by this function is cleaning up
after various problems on streams in questionable state, so give
it a more specific name and add a bit of comment.

Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
---
 drivers/usb/host/xhci-ring.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9d1af76955cd..aebbdbfd8da8 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2566,10 +2566,14 @@ static int process_bulk_intr_td(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
 
 	return finish_td(xhci, ep, ep_ring, td, trb_comp_code);
 }
 
-/* Transfer events which don't point to a transfer TRB, see xhci 4.17.4 */
-static int handle_transferless_tx_event(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
+/*
+ * Transfer events which don't point to a transfer TRB, see xhci 4.17.4
+ * Specifically, this deals with cases where the EP has streams and the event
+ * TRB pointer is NULL or otherwise doesn't point into any known stream ring.
+ */
+static int handle_bad_stream_event(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
 					u32 trb_comp_code)
 {
 	switch (trb_comp_code) {
 	case COMP_STALL_ERROR:
@@ -2581,10 +2585,8 @@ static int handle_transferless_tx_event(struct xhci_hcd *xhci, struct xhci_virt_
 			xhci_handle_halted_endpoint(xhci, ep, NULL, EP_HARD_RESET);
 		else
 			xhci_handle_halted_endpoint(xhci, ep, NULL, EP_SOFT_RESET);
 		break;
-	case COMP_RING_UNDERRUN:
-	case COMP_RING_OVERRUN:
 	case COMP_STOPPED_LENGTH_INVALID:
 		break;
 	default:
 		xhci_err(xhci, "Transfer event %u for unknown stream ring slot %u ep %u\n",
@@ -2637,9 +2639,9 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		goto err_out;
 	}
 
 	if (!ep_ring)
-		return handle_transferless_tx_event(xhci, ep, trb_comp_code);
+		return handle_bad_stream_event(xhci, ep, trb_comp_code);
 
 	/* Look for common error cases */
 	switch (trb_comp_code) {
 	/* Skip codes that require special handling depending on
-- 
2.43.0