Re: Strange behavior of high-speed hub during hibernation test

On Wed, 12 Dec 2007, David Brownell wrote:

> On Tuesday 11 December 2007, Alan Stern wrote:
> > Dave:
> > 
> > I just tried doing some hibernation testing, and my external high-speed
> > hub is behaving very strangely.  The test is simple.  First plug in the
> > hub, then plug a flash drive into the hub to keep it from
> > autosuspending.  Then:
> > 
> > 	echo test >/sys/power/disk
> > 	echo disk >/sys/power/state
> > 
> > The first line causes the hibernation to stop after the PM_EVENT_FREEZE 
> > message has been sent; after that everything is woken back up.  There 
> > are no bus-power-level changes since the EHCI controller remains in D0 
> > throughout.
> > 
> > This sequence causes the hub to disconnect and reconnect itself!  When
> > khubd starts running again, it sees the port-connect-change event.

> This doesn't ring any bells with me.  It seems buglike.  :)

Well, I can't tell exactly what the cause is.  But this patch fixes it.  
Look okay to you?

Alan Stern



This patch (as1029) adds a short delay to the bus-suspend routine in
ehci-hcd.  Without it some devices disconnect when they should
suspend.

The patch also moves a del_timer_sync() call outside the scope of a
spinlock, where it could cause a deadlock, and adds a new
del_timer_sync() call for the new IAA watchdog timer (it was omitted
by mistake).

Signed-off-by: Alan Stern <stern-nwvwT67g6+6dFdvTe/[email protected]>

---

Index: usb-2.6/drivers/usb/host/ehci-hub.c
===================================================================
--- usb-2.6.orig/drivers/usb/host/ehci-hub.c
+++ usb-2.6/drivers/usb/host/ehci-hub.c
@@ -170,8 +170,11 @@ static int ehci_bus_suspend (struct usb_
 		}
 	}
 
+	/* Apparently some devices need a 1-uframe delay here */
+	if (ehci->bus_suspended)
+		udelay(125);
+
 	/* turn off now-idle HC */
-	del_timer_sync (&ehci->watchdog);
 	ehci_halt (ehci);
 	hcd->state = HC_STATE_SUSPENDED;
 
@@ -184,6 +187,9 @@ static int ehci_bus_suspend (struct usb_
 
 	ehci->next_statechange = jiffies + msecs_to_jiffies(10);
 	spin_unlock_irq (&ehci->lock);
+
+	del_timer_sync(&ehci->watchdog);
+	del_timer_sync(&ehci->iaa_watchdog);
 	return 0;
 }
 

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