On Sun, 24 May 2009, David wrote:
> Alan Stern wrote:
> > It's not obvious what could be causing this, so let's start out easy.
> > Try collecting two usbmon traces (instructions are in
> > Documentation/usb/usbmon.txt), showing what happens with and without
> > the reversion. Maybe some difference will stick ou
> >
> Traces attached. Took a while as my quad core hangs solid when 0u is
> piped to a file (I had to compile on a laptop and take the logs there).
Okay, here's a patch for you to try. It refreshes the toggle setting
in a linked but otherwise idle QH when a new URB is queued.
Alan Stern
Index: usb-2.6/drivers/usb/host/ehci-q.c
===================================================================
--- usb-2.6.orig/drivers/usb/host/ehci-q.c
+++ usb-2.6/drivers/usb/host/ehci-q.c
@@ -88,7 +88,7 @@ static inline void
qh_update (struct ehci_hcd *ehci, struct ehci_qh *qh, struct ehci_qtd *qtd)
{
/* writes to an active overlay are unsafe */
- BUG_ON(qh->qh_state != QH_STATE_IDLE);
+ BUG_ON(qh->qh_state != QH_STATE_IDLE && !list_empty(&qh->qtd_list));
qh->hw_qtd_next = QTD_NEXT(ehci, qtd->qtd_dma);
qh->hw_alt_next = EHCI_LIST_END(ehci);
@@ -971,7 +971,13 @@ static struct ehci_qh *qh_append_tds (
/* can't sleep here, we have ehci->lock... */
qh = qh_make (ehci, urb, GFP_ATOMIC);
*ptr = qh;
+ } else if (list_empty(&qh->qtd_list)) {
+ /* There might have been a Clear-Halt while the QH
+ * was linked but empty.
+ */
+ qh_refresh(ehci, qh);
}
+
if (likely (qh != NULL)) {
struct ehci_qtd *qtd;
--
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