[PATCH 3.10 05/55] USB: OHCI: dont lose track of EDs when a controller dies

Greg Kroah-Hartman
2014-09-03T22:05:56Z

From: Alan Stern <stern@rowland.harvard.edu>

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@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/host/ohci-q.c | 46 +++++++++++++++++++++++++++++-----------------
1 file changed, 29 insertions(+), 17 deletions(-)

--- a/drivers/usb/host/ohci-q.c
+++ b/drivers/usb/host/ohci-q.c
@@ -314,8 +314,7 @@ static void periodic_unlink (struct ohci
* - 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.
@@ -928,6 +927,10 @@ 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
*/
@@ -957,12 +960,20 @@ 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
@@ -1020,19 +1031,20 @@ 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)