USB: EHCI: use hrtimer for the IAA watchdog

This patch (as1581) replaces the iaa_watchdog kernel timer used by
ehci-hcd with an hrtimer event, in keeping with the general conversion
to high-res timers.

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

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/usb/host/ehci-timer.c b/drivers/usb/host/ehci-timer.c
index 8feb60ff4228..aab042064226 100644
--- a/drivers/usb/host/ehci-timer.c
+++ b/drivers/usb/host/ehci-timer.c
@@ -72,6 +72,7 @@ static unsigned event_delays_ns[] = {
         1 * NSEC_PER_MSEC,      /* EHCI_HRTIMER_POLL_DEAD */
         1125 * NSEC_PER_USEC,   /* EHCI_HRTIMER_UNLINK_INTR */
         2 * NSEC_PER_MSEC,      /* EHCI_HRTIMER_FREE_ITDS */
+        10 * NSEC_PER_MSEC,     /* EHCI_HRTIMER_IAA_WATCHDOG */
         10 * NSEC_PER_MSEC,     /* EHCI_HRTIMER_DISABLE_PERIODIC */
         15 * NSEC_PER_MSEC,     /* EHCI_HRTIMER_DISABLE_ASYNC */
 };
@@ -291,6 +292,49 @@ static void end_free_itds(struct ehci_hcd *ehci)
 }
 
 
+/* Handle lost (or very late) IAA interrupts */
+static void ehci_iaa_watchdog(struct ehci_hcd *ehci)
+{
+        if (ehci->rh_state != EHCI_RH_RUNNING)
+                return;
+
+        /*
+         * Lost IAA irqs wedge things badly; seen first with a vt8235.
+         * So we need this watchdog, but must protect it against both
+         * (a) SMP races against real IAA firing and retriggering, and
+         * (b) clean HC shutdown, when IAA watchdog was pending.
+         */
+        if (ehci->async_unlink) {
+                u32 cmd, status;
+
+                /* If we get here, IAA is *REALLY* late.  It's barely
+                 * conceivable that the system is so busy that CMD_IAAD
+                 * is still legitimately set, so let's be sure it's
+                 * clear before we read STS_IAA.  (The HC should clear
+                 * CMD_IAAD when it sets STS_IAA.)
+                 */
+                cmd = ehci_readl(ehci, &ehci->regs->command);
+
+                /*
+                 * If IAA is set here it either legitimately triggered
+                 * after the watchdog timer expired (_way_ late, so we'll
+                 * still count it as lost) ... or a silicon erratum:
+                 * - VIA seems to set IAA without triggering the IRQ;
+                 * - IAAD potentially cleared without setting IAA.
+                 */
+                status = ehci_readl(ehci, &ehci->regs->status);
+                if ((status & STS_IAA) || !(cmd & CMD_IAAD)) {
+                        COUNT(ehci->stats.lost_iaa);
+                        ehci_writel(ehci, STS_IAA, &ehci->regs->status);
+                }
+
+                ehci_vdbg(ehci, "IAA watchdog: status %x cmd %x\n",
+                                status, cmd);
+                end_unlink_async(ehci);
+        }
+}
+
+
 /*
  * Handler functions for the hrtimer event types.
  * Keep this array in the same order as the event types indexed by
@@ -302,6 +346,7 @@ static void (*event_handlers[])(struct ehci_hcd *) = {
         ehci_handle_controller_death,   /* EHCI_HRTIMER_POLL_DEAD */
         ehci_handle_intr_unlinks,       /* EHCI_HRTIMER_UNLINK_INTR */
         end_free_itds,                  /* EHCI_HRTIMER_FREE_ITDS */
+        ehci_iaa_watchdog,              /* EHCI_HRTIMER_IAA_WATCHDOG */
         ehci_disable_PSE,               /* EHCI_HRTIMER_DISABLE_PERIODIC */
         ehci_disable_ASE,               /* EHCI_HRTIMER_DISABLE_ASYNC */
 };