USB: EHCI: use hrtimer for the I/O watchdog

This patch (as1586) replaces the kernel timer used by ehci-hcd as an
I/O watchdog with an hrtimer event.

Unlike in the current code, the watchdog event is now always enabled
whenever any isochronous URBs are active.  This will prevent bugs
caused by the periodic schedule wrapping around with no completion
interrupts; the watchdog handler is guaranteed to scan the isochronous
transfers at least once during each iteration of the schedule.  The
extra overhead will be negligible: one timer interrupt every 100 ms.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index c9c7f7b3b7db..9bc39ca460c8 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -970,6 +970,7 @@ static void enable_async(struct ehci_hcd *ehci)
 
         /* Don't start the schedule until ASS is 0 */
         ehci_poll_ASS(ehci);
+        turn_on_io_watchdog(ehci);
 }
 
 static void disable_async(struct ehci_hcd *ehci)