On Tue, 11 Aug 2009, Jon Hunter wrote: > 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> > --- > drivers/usb/host/ehci-hub.c | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/drivers/usb/host/ehci-hub.c b/drivers/usb/host/ehci-hub.c > index f46ad27..96801ca 100644 > --- a/drivers/usb/host/ehci-hub.c > +++ b/drivers/usb/host/ehci-hub.c > @@ -183,6 +183,11 @@ static int ehci_bus_suspend (struct usb_hcd *hcd) > > 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; > } Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
