linux-kernel - [ 17/26] USB: EHCI: fix timer bug affecting port resume

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Date:	Thu,  7 Feb 2013 16:57:45 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Alan Stern <stern@...land.harvard.edu>,
	Ming Lei <ming.lei@...onical.com>
Subject: [ 17/26] USB: EHCI: fix timer bug affecting port resume

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alan Stern <stern@...land.harvard.edu>

commit ee74290b7853db9d5fd64db70e5c175241c59fba upstream.

This patch (as1652) fixes a long-standing bug in ehci-hcd.  The driver
relies on status polls to know when to stop port-resume signalling.
It uses the root-hub status timer to schedule these status polls.  But
when the driver for the root hub is resumed, the timer is rescheduled
to go off immediately -- before the port is ready.  When this happens
the timer does not get re-enabled, which prevents the port resume from
finishing until some other event occurs.

The symptom is that when a new device is plugged in, it doesn't get
recognized or enumerated until lsusb is run or something else happens.

The solution is to re-enable the root-hub status timer after every
status poll while a port resume is in progress.

This bug hasn't surfaced before now because we never used to try to
suspend the root hub in the middle of a port resume (except by
coincidence).

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Reported-and-tested-by: Norbert Preining <preining@...ic.at>
Tested-by: Ming Lei <ming.lei@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/host/ehci-hub.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/usb/host/ehci-hub.c
+++ b/drivers/usb/host/ehci-hub.c
@@ -612,7 +612,11 @@ ehci_hub_status_data (struct usb_hcd *hc
 			status = STS_PCD;
 		}
 	}
-	/* FIXME autosuspend idle root hubs */
+
+	/* If a resume is in progress, make sure it can finish */
+	if (ehci->resuming_ports)
+		mod_timer(&hcd->rh_timer, jiffies + msecs_to_jiffies(25));
+
 	spin_unlock_irqrestore (&ehci->lock, flags);
 	return status ? retval : 0;
 }

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