USB: EHCI: revert "remove ASS/PSS polling timeout"

This patch (as1649) reverts commit
55bcdce8 (USB: EHCI: remove ASS/PSS
polling timeout).  That commit was written under the assumption that
some controllers may take a very long time to turn off their async and
periodic schedules.  It now appears that in fact the schedules do get
turned off reasonably quickly, but some controllers occasionally leave
the schedules' status bits turned on and consequently ehci-hcd can't
tell that the schedules are off.

VIA controllers in particular have this problem.  ehci-hcd tells the
hardware to turn off the async schedule, the schedule does get turned
off, but the status bit remains on.  Since the EHCI spec requires that
the schedules not be re-enabled until the previous disable has taken
effect, with an unlimited timeout the async schedule never gets turned
back on.  The resulting symptom is that the system is unable to
communicate with USB devices.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: Ronald <ronald645@gmail.com>
Reported-and-tested-by: Paul Hartman <paul.hartman@gmail.com>
Reported-and-tested-by: Dieter Nützel <dieter@nuetzel-hh.de>
Reported-and-tested-by: Jean Delvare <khali@linux-fr.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-timer.c

@@ -113,15 +113,14 @@ static void ehci_poll_ASS(struct ehci_hcd *ehci)
 
 	if (want != actual) {
 
-		/* Poll again later */
+		/* Poll again later, but give up after about 20 ms */
+		if (ehci->ASS_poll_count++ < 20) {
 			ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
-		++ehci->ASS_poll_count;
 			return;
 		}
-
-	if (ehci->ASS_poll_count > 20)
-		ehci_dbg(ehci, "ASS poll count reached %d\n",
-				ehci->ASS_poll_count);
+		ehci_dbg(ehci, "Waited too long for the async schedule status (%x/%x), giving up\n",
+				want, actual);
+	}
 	ehci->ASS_poll_count = 0;
 
 	/* The status is up-to-date; restart or stop the schedule as needed */
@@ -160,14 +159,14 @@ static void ehci_poll_PSS(struct ehci_hcd *ehci)
 
 	if (want != actual) {
 
-		/* Poll again later */
+		/* Poll again later, but give up after about 20 ms */
+		if (ehci->PSS_poll_count++ < 20) {
 			ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
 			return;
 		}
-
-	if (ehci->PSS_poll_count > 20)
-		ehci_dbg(ehci, "PSS poll count reached %d\n",
-				ehci->PSS_poll_count);
+		ehci_dbg(ehci, "Waited too long for the periodic schedule status (%x/%x), giving up\n",
+				want, actual);
+	}
 	ehci->PSS_poll_count = 0;
 
 	/* The status is up-to-date; restart or stop the schedule as needed */