patch "xhci: Don't show incorrect WARN message about events for empty rings" added to usb-linus

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    xhci: Don't show incorrect WARN message about events for empty rings

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From e4ec40ec4b260efcca15089de4285a0a3411259b Mon Sep 17 00:00:00 2001
From: Mathias Nyman <mathias.nyman@linux.intel.com>
Date: Fri, 1 Dec 2017 13:41:19 +0200
Subject: xhci: Don't show incorrect WARN message about events for empty rings

xHC can generate two events for a short transfer if the short TRB and
last TRB in the TD are not the same TRB.

The driver will handle the TD after the first short event, and remove
it from its internal list. Driver then incorrectly prints a warning
for the second event:

"WARN Event TRB for slot x ep y with no TDs queued"

Fix this by not printing a warning if we get a event on a empty list
if the previous event was a short event.

Cc: <stable@vger.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/host/xhci-ring.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index c239c688076c..6eb87c6e4d24 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2477,12 +2477,16 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		 */
 		if (list_empty(&ep_ring->td_list)) {
 			/*
-			 * A stopped endpoint may generate an extra completion
-			 * event if the device was suspended.  Don't print
-			 * warnings.
+			 * 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)) {
+			      trb_comp_code == COMP_STOPPED_LENGTH_INVALID ||
+			      ep_ring->last_td_was_short)) {
 				xhci_warn(xhci, "WARN Event TRB for slot %d ep %d with no TDs queued?\n",
 						TRB_TO_SLOT_ID(le32_to_cpu(event->flags)),
 						ep_index);
-- 
2.15.1