USB: EHCI: revert "remove ASS/PSS polling timeout"
authorAlan Stern <stern@rowland.harvard.edu>
Tue, 26 Feb 2013 18:43:41 +0000 (13:43 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 26 Feb 2013 21:22:38 +0000 (13:22 -0800)
This patch (as1649) reverts commit
55bcdce8a8228223ec4d17d8ded8134ed265d2c5 (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 N├╝tzel <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

index f904071..20dbdcb 100644 (file)
@@ -113,15 +113,14 @@ static void ehci_poll_ASS(struct ehci_hcd *ehci)
 
        if (want != actual) {
 
-               /* Poll again later */
-               ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
-               ++ehci->ASS_poll_count;
-               return;
+               /* 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);
+                       return;
+               }
+               ehci_dbg(ehci, "Waited too long for the async schedule status (%x/%x), giving up\n",
+                               want, actual);
        }
-
-       if (ehci->ASS_poll_count > 20)
-               ehci_dbg(ehci, "ASS poll count reached %d\n",
-                               ehci->ASS_poll_count);
        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 */
-               ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
-               return;
+               /* 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;
+               }
+               ehci_dbg(ehci, "Waited too long for the periodic schedule status (%x/%x), giving up\n",
+                               want, actual);
        }
-
-       if (ehci->PSS_poll_count > 20)
-               ehci_dbg(ehci, "PSS poll count reached %d\n",
-                               ehci->PSS_poll_count);
        ehci->PSS_poll_count = 0;
 
        /* The status is up-to-date; restart or stop the schedule as needed */