USB: EHCI: change deschedule logic for interrupt QHs

This patch (as1281) changes the way ehci-hcd deschedules interrupt
QHs, copying the approach used for async QHs.  The caller is no longer
responsible for rescheduling the QH if its queue is non-empty; instead
the reschedule is done directly by intr_deschedule(), after calling
qh_completions().  This is exactly the same as how end_unlink_async()
works.

ehci_urb_dequeue() and intr_deschedule() now correctly handle the case
where they are called while another interrupt URB for the same QH is
being given back.  This was a surprisingly large blind spot.  And
scan_periodic() now respects the new needs_rescan flag.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 40 insertions, 34 deletions

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index d7e85b6231b3..4f89d7ffd53a 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -934,8 +934,9 @@ static int ehci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
                         break;
                 switch (qh->qh_state) {
                 case QH_STATE_LINKED:
+                case QH_STATE_COMPLETING:
                         intr_deschedule (ehci, qh);
-                        /* FALL THROUGH */
+                        break;
                 case QH_STATE_IDLE:
                         qh_completions (ehci, qh);
                         break;
@@ -944,23 +945,6 @@ static int ehci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
                                         qh, qh->qh_state);
                         goto done;
                 }
-
-                /* reschedule QH iff another request is queued */
-                if (!list_empty (&qh->qtd_list)
-                                && HC_IS_RUNNING (hcd->state)) {
-                        rc = qh_schedule(ehci, qh);
-
-                        /* An error here likely indicates handshake failure
-                         * or no space left in the schedule.  Neither fault
-                         * should happen often ...
-                         *
-                         * FIXME kill the now-dysfunctional queued urbs
-                         */
-                        if (rc != 0)
-                                ehci_err(ehci,
-                                        "can't reschedule qh %p, err %d",
-                                        qh, rc);
-                }
                 break;
 
         case PIPE_ISOCHRONOUS:
@@ -1079,12 +1063,10 @@ ehci_endpoint_reset(struct usb_hcd *hcd, struct usb_host_endpoint *ep)
                          * while the QH is active.  Unlink it now;
                          * re-linking will call qh_refresh().
                          */
-                        if (eptype == USB_ENDPOINT_XFER_BULK) {
+                        if (eptype == USB_ENDPOINT_XFER_BULK)
                                 unlink_async(ehci, qh);
-                        } else {
+                        else
                                 intr_deschedule(ehci, qh);
-                                (void) qh_schedule(ehci, qh);
-                        }
                 }
         }
         spin_unlock_irqrestore(&ehci->lock, flags);
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 57a84795c43f..00ad9ce392ed 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -299,7 +299,6 @@ __acquires(ehci->lock)
 static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh);
 static void unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh);
 
-static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh);
 static int qh_schedule (struct ehci_hcd *ehci, struct ehci_qh *qh);
 
 /*
@@ -555,14 +554,9 @@ halt:
                          * That should be rare for interrupt transfers,
                          * except maybe high bandwidth ...
                          */
-                        if ((cpu_to_hc32(ehci, QH_SMASK)
-                                        & hw->hw_info2) != 0) {
-                                intr_deschedule (ehci, qh);
-                                (void) qh_schedule (ehci, qh);
-                        } else {
-                                /* Tell the caller to start an unlink */
-                                qh->needs_rescan = 1;
-                        }
+
+                        /* Tell the caller to start an unlink */
+                        qh->needs_rescan = 1;
                         break;
                 /* otherwise, unlink already started */
                 }
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 327437af2122..3ea05936851f 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -615,8 +615,19 @@ static int qh_unlink_periodic(struct ehci_hcd *ehci, struct ehci_qh *qh)
 
 static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
 {
-        unsigned        wait;
-        struct ehci_qh_hw *hw = qh->hw;
+        unsigned                wait;
+        struct ehci_qh_hw       *hw = qh->hw;
+        int                     rc;
+
+        /* If the QH isn't linked then there's nothing we can do
+         * unless we were called during a giveback, in which case
+         * qh_completions() has to deal with it.
+         */
+        if (qh->qh_state != QH_STATE_LINKED) {
+                if (qh->qh_state == QH_STATE_COMPLETING)
+                        qh->needs_rescan = 1;
+                return;
+        }
 
         qh_unlink_periodic (ehci, qh);
 
@@ -636,6 +647,24 @@ static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
         qh->qh_state = QH_STATE_IDLE;
         hw->hw_next = EHCI_LIST_END(ehci);
         wmb ();
+
+        qh_completions(ehci, qh);
+
+        /* reschedule QH iff another request is queued */
+        if (!list_empty(&qh->qtd_list) &&
+                        HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {
+                rc = qh_schedule(ehci, qh);
+
+                /* An error here likely indicates handshake failure
+                 * or no space left in the schedule.  Neither fault
+                 * should happen often ...
+                 *
+                 * FIXME kill the now-dysfunctional queued urbs
+                 */
+                if (rc != 0)
+                        ehci_err(ehci, "can't reschedule qh %p, err %d\n",
+                                        qh, rc);
+        }
 }
 
 /*-------------------------------------------------------------------------*/
@@ -2213,7 +2242,8 @@ restart:
                                 type = Q_NEXT_TYPE(ehci, q.qh->hw->hw_next);
                                 q = q.qh->qh_next;
                                 modified = qh_completions (ehci, temp.qh);
-                                if (unlikely (list_empty (&temp.qh->qtd_list)))
+                                if (unlikely(list_empty(&temp.qh->qtd_list) ||
+                                                temp.qh->needs_rescan))
                                         intr_deschedule (ehci, temp.qh);
                                 qh_put (temp.qh);
                                 break;