[3.16.y-ckt stable] Patch "Revert "xhci: don't finish a TD if we get a short-transfer event mid TD"" has been added to the 3.16.y-ckt tree

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    Revert "xhci: don't finish a TD if we get a short-transfer event mid TD"

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt25.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

---8<------------------------------------------------------------

>From 877417fe0c22521283dcb39d08170010c505aa69 Mon Sep 17 00:00:00 2001
From: Mathias Nyman <mathias.nyman at linux.intel.com>
Date: Tue, 26 Jan 2016 17:50:04 +0200
Subject: Revert "xhci: don't finish a TD if we get a short-transfer event mid
 TD"

commit a6835090716a85f2297668ba593bd00e1051e662 upstream.

This reverts commit e210c422b6fd ("xhci: don't finish a TD if we get a
short transfer event mid TD")

Turns out that most host controllers do not follow the xHCI specs and never
send the second event for the last TRB in the TD if there was a short event
mid-TD.

Returning the URB directly after the first short-transfer event is far
better than never returning the URB. (class drivers usually timeout
after 30sec). For the hosts that do send the second event we will go
back to treating it as misplaced event and print an error message for it.

The origial patch was sent to stable kernels and needs to be reverted from
there as well

Signed-off-by: Mathias Nyman <mathias.nyman at linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/host/xhci-ring.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 22c9bca66569..f15e2df4448c 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2192,10 +2192,6 @@ static int process_bulk_intr_td(struct xhci_hcd *xhci, struct xhci_td *td,
 				EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)));
 	/* Fast path - was this the last TRB in the TD for this URB? */
 	if (event_trb == td->last_trb) {
-		if (td->urb_length_set && trb_comp_code == COMP_SHORT_TX)
-			return finish_td(xhci, td, event_trb, event, ep,
-					 status, false);
-
 		if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) != 0) {
 			td->urb->actual_length =
 				td->urb->transfer_buffer_length -
@@ -2247,12 +2243,6 @@ static int process_bulk_intr_td(struct xhci_hcd *xhci, struct xhci_td *td,
 			td->urb->actual_length +=
 				TRB_LEN(le32_to_cpu(cur_trb->generic.field[2])) -
 				EVENT_TRB_LEN(le32_to_cpu(event->transfer_len));
-
-		if (trb_comp_code == COMP_SHORT_TX) {
-			xhci_dbg(xhci, "mid bulk/intr SP, wait for last TRB event\n");
-			td->urb_length_set = true;
-			return 0;
-		}
 	}

 	return finish_td(xhci, td, event_trb, event, ep, status, false);