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.
Cheers
Jon
-------- 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: gregkh@xxxxxxx <gregkh@xxxxxxx>
To: Hunter, Jon <jon-hunter@xxxxxx>, fei.yang@xxxxxxxxxxxx
<fei.yang@xxxxxxxxxxxx>, gregkh@xxxxxxx <gregkh@xxxxxxx>,
greg@xxxxxxxxx <greg@xxxxxxxxx>, stern@xxxxxxxxxxxxxxxxxxx
<stern@xxxxxxxxxxxxxxxxxxx>
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 stern@xxxxxxxxxxxxxxxxxxx Thu Aug 13 16:37:16 2009
From: Jon Hunter <jon-hunter@xxxxxx>
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 <greg@xxxxxxxxx>, Jon Hunter <jon-hunter@xxxxxx>
Cc: Fei Yang <fei.yang@xxxxxxxxxxxx>
Message-ID: <Pine.LNX.4.44L0.0908121157090.9635-100000@xxxxxxxxxxxxxxxxxxxx>
From: Jon Hunter <jon-hunter@xxxxxx>
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 <fei.yang@xxxxxxxxxxxx>
Signed-off-by: Jon Hunter <jon-hunter@xxxxxx>
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
drivers/usb/host/ehci-hub.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/drivers/usb/host/ehci-hub.c
+++ b/drivers/usb/host/ehci-hub.c
@@ -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;
}
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