USB: EHCI: update toggle state for linked QHs

This patch (as1245) fixes a bug in ehci-hcd.  When an URB is queued
for an endpoint whose QH is already in the LINKED state, the QH
doesn't get refreshed.  As a result, if usb_clear_halt() was called
during the time that the QH was linked but idle, the data toggle value
in the QH doesn't get reset.

The symptom is that after a clear_halt, data gets lost and transfers
time out.  This problem is starting to show up now because the
"ehci-hcd unlink speedups" patch causes QHs with no queued URBs to
remain linked for a suitable time.

The patch utilizes the new endpoint_reset mechanism to fix the
problem.  When an endpoint is reset, the new method forcibly unlinks
the QH (if necessary) and safely updates the toggle value.  This
allows qh_update() to be simplified and avoids using usb_device's
toggle bits in a rather unintuitive way.

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

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index a2ca9cbf2809..2b72473544d3 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -1024,6 +1024,51 @@ done:
         return;
 }
 
+static void
+ehci_endpoint_reset(struct usb_hcd *hcd, struct usb_host_endpoint *ep)
+{
+        struct ehci_hcd         *ehci = hcd_to_ehci(hcd);
+        struct ehci_qh          *qh;
+        int                     eptype = usb_endpoint_type(&ep->desc);
+
+        if (eptype != USB_ENDPOINT_XFER_BULK && eptype != USB_ENDPOINT_XFER_INT)
+                return;
+
+ rescan:
+        spin_lock_irq(&ehci->lock);
+        qh = ep->hcpriv;
+
+        /* For Bulk and Interrupt endpoints we maintain the toggle state
+         * in the hardware; the toggle bits in udev aren't used at all.
+         * When an endpoint is reset by usb_clear_halt() we must reset
+         * the toggle bit in the QH.
+         */
+        if (qh) {
+                if (!list_empty(&qh->qtd_list)) {
+                        WARN_ONCE(1, "clear_halt for a busy endpoint\n");
+                } else if (qh->qh_state == QH_STATE_IDLE) {
+                        qh->hw_token &= ~cpu_to_hc32(ehci, QTD_TOGGLE);
+                } else {
+                        /* It's not safe to write into the overlay area
+                         * while the QH is active.  Unlink it first and
+                         * wait for the unlink to complete.
+                         */
+                        if (qh->qh_state == QH_STATE_LINKED) {
+                                if (eptype == USB_ENDPOINT_XFER_BULK) {
+                                        unlink_async(ehci, qh);
+                                } else {
+                                        intr_deschedule(ehci, qh);
+                                        (void) qh_schedule(ehci, qh);
+                                }
+                        }
+                        spin_unlock_irq(&ehci->lock);
+                        schedule_timeout_uninterruptible(1);
+                        goto rescan;
+                }
+        }
+        spin_unlock_irq(&ehci->lock);
+}
+
 static int ehci_get_frame (struct usb_hcd *hcd)
 {
         struct ehci_hcd         *ehci = hcd_to_ehci (hcd);