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Commit fc0855f2 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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USB: EHCI: warn on unexpectedly active QH 



This patch adds a new warning message to ehci-hcd.  The warning is
triggered whenever the driver finds that the hardware has set the
Active bit in a QH at a time when the driver expects the QH to be
completely idle.  Such bugs have been observed by users in the past,
and since they can lead to serious problems (such as inability to
unlink an URB that never completes), it would be good to know about
them when they occur.

This won't fix these bugs; that's a bigger job for a later patch.  But
success isn't guaranteed, since this depends on aspects of the
hardware which are not documented in the EHCI spec or for which the
spec's recommendations are clearly unworkable.  It therefore seems
worthwhile to check for these bugs proactively.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Reported-by: default avatarMichael Reutman <mreutman@epiqsolutions.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8ee10d62

drivers/usb/host/ehci-q.c

+7 −2
Original line number Diff line number Diff line
@@ -132,11 +132,15 @@ qh_refresh (struct ehci_hcd *ehci, struct ehci_qh *qh) 
	 * qtd is updated in qh_completions(). Update the QH

	 * overlay here.

	 */

	if (qh->hw->hw_token & ACTIVE_BIT(ehci))

	if (qh->hw->hw_token & ACTIVE_BIT(ehci)) {

		qh->hw->hw_qtd_next = qtd->hw_next;

	else

		if (qh->should_be_inactive)

			ehci_warn(ehci, "qh %p should be inactive!\n", qh);

	} else {

		qh_update(ehci, qh, qtd);

	}

	qh->should_be_inactive = 0;

}



/*-------------------------------------------------------------------------*/
@@ -438,6 +442,7 @@ qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh) 
					(hw->hw_token & ACTIVE_BIT(ehci))) {

				token = hc32_to_cpu(ehci, hw->hw_token);

				hw->hw_token &= ~ACTIVE_BIT(ehci);

				qh->should_be_inactive = 1;



				/* An unlink may leave an incomplete

				 * async transaction in the TT buffer.

drivers/usb/host/ehci.h

+1 −0
Original line number Diff line number Diff line
@@ -439,6 +439,7 @@ struct ehci_qh { 
	unsigned		dequeue_during_giveback:1;

	unsigned		exception:1;	/* got a fault, or an unlink

						   was requested */

	unsigned		should_be_inactive:1;

};



/*-------------------------------------------------------------------------*/