[3.13.y.z extended stable] Patch "USB: OHCI: don't lose track of EDs when a controller dies" has been added to staging queue

[Kamal Mostafa]

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

    USB: OHCI: don't lose track of EDs when a controller dies

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.7.

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

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 3d9475c24e62024b34cf673fa237ba09cd4e898f Mon Sep 17 00:00:00 2001
From: Alan Stern <stern at rowland.harvard.edu>
Date: Thu, 17 Jul 2014 16:34:29 -0400
Subject: USB: OHCI: don't lose track of EDs when a controller dies

commit 977dcfdc60311e7aa571cabf6f39c36dde13339e upstream.

This patch fixes a bug in ohci-hcd.  When an URB is unlinked, the
corresponding Endpoint Descriptor is added to the ed_rm_list and taken
off the hardware schedule.  Once the ED is no longer visible to the
hardware, finish_unlinks() handles the URBs that were unlinked or have
completed.  If any URBs remain attached to the ED, the ED is added
back to the hardware schedule -- but only if the controller is
running.

This fails when a controller dies.  A non-empty ED does not get added
back to the hardware schedule and does not remain on the ed_rm_list;
ohci-hcd loses track of it.  The remaining URBs cannot be unlinked,
which causes the USB stack to hang.

The patch changes finish_unlinks() so that non-empty EDs remain on
the ed_rm_list if the controller isn't running.  This requires moving
some of the existing code around, to avoid modifying the ED's hardware
fields more than once.

Signed-off-by: Alan Stern <stern at rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/usb/host/ohci-q.c | 46 +++++++++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/host/ohci-q.c b/drivers/usb/host/ohci-q.c
index e7f577e..4e9f6a4 100644
--- a/drivers/usb/host/ohci-q.c
+++ b/drivers/usb/host/ohci-q.c
@@ -315,8 +315,7 @@ static void periodic_unlink (struct ohci_hcd *ohci, struct ed *ed)
  *  - ED_OPER: when there's any request queued, the ED gets rescheduled
  *    immediately.  HC should be working on them.
  *
- *  - ED_IDLE:  when there's no TD queue. there's no reason for the HC
- *    to care about this ED; safe to disable the endpoint.
+ *  - ED_IDLE: when there's no TD queue or the HC isn't running.
  *
  * When finish_unlinks() runs later, after SOF interrupt, it will often
  * complete one or more URB unlinks before making that state change.
@@ -930,6 +929,10 @@ rescan_all:
 		int			completed, modified;
 		__hc32			*prev;

+		/* Is this ED already invisible to the hardware? */
+		if (ed->state == ED_IDLE)
+			goto ed_idle;
+
 		/* only take off EDs that the HC isn't using, accounting for
 		 * frame counter wraps and EDs with partially retired TDs
 		 */
@@ -959,12 +962,20 @@ skip_ed:
 			}
 		}

+		/* ED's now officially unlinked, hc doesn't see */
+		ed->state = ED_IDLE;
+		if (quirk_zfmicro(ohci) && ed->type == PIPE_INTERRUPT)
+			ohci->eds_scheduled--;
+		ed->hwHeadP &= ~cpu_to_hc32(ohci, ED_H);
+		ed->hwNextED = 0;
+		wmb();
+		ed->hwINFO &= ~cpu_to_hc32(ohci, ED_SKIP | ED_DEQUEUE);
+ed_idle:
+
 		/* reentrancy:  if we drop the schedule lock, someone might
 		 * have modified this list.  normally it's just prepending
 		 * entries (which we'd ignore), but paranoia won't hurt.
 		 */
-		*last = ed->ed_next;
-		ed->ed_next = NULL;
 		modified = 0;

 		/* unlink urbs as requested, but rescan the list after
@@ -1022,19 +1033,20 @@ rescan_this:
 		if (completed && !list_empty (&ed->td_list))
 			goto rescan_this;

-		/* ED's now officially unlinked, hc doesn't see */
-		ed->state = ED_IDLE;
-		if (quirk_zfmicro(ohci) && ed->type == PIPE_INTERRUPT)
-			ohci->eds_scheduled--;
-		ed->hwHeadP &= ~cpu_to_hc32(ohci, ED_H);
-		ed->hwNextED = 0;
-		wmb ();
-		ed->hwINFO &= ~cpu_to_hc32 (ohci, ED_SKIP | ED_DEQUEUE);
-
-		/* but if there's work queued, reschedule */
-		if (!list_empty (&ed->td_list)) {
-			if (ohci->rh_state == OHCI_RH_RUNNING)
-				ed_schedule (ohci, ed);
+		/*
+		 * If no TDs are queued, take ED off the ed_rm_list.
+		 * Otherwise, if the HC is running, reschedule.
+		 * If not, leave it on the list for further dequeues.
+		 */
+		if (list_empty(&ed->td_list)) {
+			*last = ed->ed_next;
+			ed->ed_next = NULL;
+		} else if (ohci->rh_state == OHCI_RH_RUNNING) {
+			*last = ed->ed_next;
+			ed->ed_next = NULL;
+			ed_schedule(ohci, ed);
+		} else {
+			last = &ed->ed_next;
 		}

 		if (modified)
--
1.9.1