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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: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Michael Reutman <mreutman@epiqsolutions.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Stern 2015-11-20 13:53:58 -05:00 committed by Greg Kroah-Hartman
parent 8ee10d6292
commit fc0855f274
2 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/usb/host/ehci-q.c
View File

@ -132,10 +132,14 @@ 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.

1
drivers/usb/host/ehci.h
View File

@ -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;
};
/*-------------------------------------------------------------------------*/