[Fwd: patch usb-ehci-ensure-all-watchdog-timer-events-are-deleted-when-suspending-usb.patch added to gregkh-2.6 tree]

Hi All,

I just thought I would send out this patch as an FYI. We recently ran into an issue where we were getting a kernel panic in the ehci driver when entering suspend on the omap3. We discussed this with the linux-usb folks and they recommended the below fix. This problem is hard to reproduce, but has not been seen since adding this fix. Anyway the details are below.

-------- Original Message --------
Subject: patch usb-ehci-ensure-all-watchdog-timer-events-are-deleted-when-suspending-usb.patch added to gregkh-2.6 tree
Date: Fri, 14 Aug 2009 11:48:45 -0500
From: [email protected] <[email protected]>
To: Hunter, Jon <[email protected]>, [email protected] <[email protected]>, [email protected] <[email protected]>,
[email protected] <[email protected]>, [email protected]
<[email protected]>

This is a note to let you know that I've just added the patch titled

Subject: USB: EHCI: ensure all watchdog timer events are deleted
when suspending usb

to my gregkh-2.6 tree. Its filename is

usb-ehci-ensure-all-watchdog-timer-events-are-deleted-when-suspending-usb.patch

This tree can be found at

http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/patches/

From [email protected] Thu Aug 13 16:37:16 2009
From: Jon Hunter <[email protected]>
Date: Wed, 12 Aug 2009 11:57:59 -0400 (EDT)
Subject: USB: EHCI: ensure all watchdog timer events are deleted when suspending usb
To: Greg KH <[email protected]>, Jon Hunter <[email protected]>
Cc: Fei Yang <[email protected]>
Message-ID: <[email protected]>

From: Jon Hunter <[email protected]>

This patch was previously discussed in the following thread:
http://thread.gmane.org/gmane.linux.usb.general/19472/focus=19484

On the OMAP3 device the usbhost controller is in a separate internal power-domain. So when the usbhost is inactive or suspend is called, we can disable clocks and power-down the usbhost to save power.

Recently we found that after calling ehci_bus_suspend() and disabling the usbhost clocks we would see the ehci watchdog timer event fire. This was causing a kernel panic because the usbhost controllers clocks were disabled and inside the watchdog timer function the clocks were not being re-enabled, so when the ehci registers were accessed this resulted in a CPU data-abort.

To avoid this panic, per recommendation from Alan Stern (see above thread), we
make sure any pending timer events (that may have been scheduled by calling ehci_work within the ehci_bus_suspend() function) are deleted before returning.

Signed-off-by Fei Yang <[email protected]>

Signed-off-by Jon Hunter <[email protected]>

Acked-by Alan Stern <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

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

drivers/usb/host/ehci-hub.c +5 -1

@@ -209,6 +209,11 @@ static int ehci_bus_suspend (struct usb_
 
 	ehci->next_statechange = jiffies + msecs_to_jiffies(10);
 	spin_unlock_irq (&ehci->lock);
+
+	/* ehci_work() may have re-enabled the watchdog timer, which we do not
+	 * want, and so we must delete any pending watchdog timer events.
+	 */
+	del_timer_sync(&ehci->watchdog);
 	return 0;
 }
 
 
 
--

To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html

Jon,

Do you know if this will be queued as a fix for .31? or if it will wait for the .32 merge window.

Kevin