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>

drivers/usb/host/ehci-hcd.c

@@ -93,7 +93,6 @@ static const char	hcd_name [] = "ehci_hcd";
  */
 #define	EHCI_TUNE_FLS		1	/* (medium) 512-frame schedule */
 
-#define EHCI_IAA_MSECS		10		/* arbitrary */
 #define EHCI_IO_JIFFIES		(HZ/10)		/* io watchdog > irq_thresh */
 #define EHCI_SHRINK_JIFFIES	(DIV_ROUND_UP(HZ, 200) + 1)
 						/* 5-ms async qh unlink delay */
@@ -322,51 +321,6 @@ static void end_unlink_intr(struct ehci_hcd *ehci, struct ehci_qh *qh);
 
 /*-------------------------------------------------------------------------*/
 
-static void ehci_iaa_watchdog(unsigned long param)
-{
-	struct ehci_hcd		*ehci = (struct ehci_hcd *) param;
-	unsigned long		flags;
-
-	spin_lock_irqsave (&ehci->lock, flags);
-
-	/* 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
-			&& !timer_pending(&ehci->iaa_watchdog)
-			&& ehci->rh_state == EHCI_RH_RUNNING) {
-		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
-		 * before we cleared IAAD above (but _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);
-	}
-
-	spin_unlock_irqrestore(&ehci->lock, flags);
-}
-
 static void ehci_watchdog(unsigned long param)
 {
 	struct ehci_hcd		*ehci = (struct ehci_hcd *) param;
@@ -418,7 +372,6 @@ static void ehci_shutdown(struct usb_hcd *hcd)
 	struct ehci_hcd	*ehci = hcd_to_ehci(hcd);
 
 	del_timer_sync(&ehci->watchdog);
-	del_timer_sync(&ehci->iaa_watchdog);
 
 	spin_lock_irq(&ehci->lock);
 	ehci->rh_state = EHCI_RH_STOPPING;
@@ -491,7 +444,6 @@ static void ehci_stop (struct usb_hcd *hcd)
 
 	/* no more interrupts ... */
 	del_timer_sync (&ehci->watchdog);
-	del_timer_sync(&ehci->iaa_watchdog);
 
 	spin_lock_irq(&ehci->lock);
 	ehci->enabled_hrtimer_events = 0;
@@ -547,10 +499,6 @@ static int ehci_init(struct usb_hcd *hcd)
 	ehci->watchdog.function = ehci_watchdog;
 	ehci->watchdog.data = (unsigned long) ehci;
 
-	init_timer(&ehci->iaa_watchdog);
-	ehci->iaa_watchdog.function = ehci_iaa_watchdog;
-	ehci->iaa_watchdog.data = (unsigned long) ehci;
-
 	hrtimer_init(&ehci->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
 	ehci->hrtimer.function = ehci_hrtimer_func;
 	ehci->next_hrtimer_event = EHCI_HRTIMER_NO_EVENT;
@@ -830,6 +778,20 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
 
 	/* complete the unlinking of some qh [4.15.2.3] */
 	if (status & STS_IAA) {
+
+		/* Turn off the IAA watchdog */
+		ehci->enabled_hrtimer_events &= ~BIT(EHCI_HRTIMER_IAA_WATCHDOG);
+
+		/*
+		 * Mild optimization: Allow another IAAD to reset the
+		 * hrtimer, if one occurs before the next expiration.
+		 * In theory we could always cancel the hrtimer, but
+		 * tests show that about half the time it will be reset
+		 * for some other event anyway.
+		 */
+		if (ehci->next_hrtimer_event == EHCI_HRTIMER_IAA_WATCHDOG)
+			++ehci->next_hrtimer_event;
+
 		/* guard against (alleged) silicon errata */
 		if (cmd & CMD_IAAD)
 			ehci_dbg(ehci, "IAA with IAAD still set?\n");

drivers/usb/host/ehci-hub.c

@@ -209,7 +209,6 @@ static int ehci_bus_suspend (struct usb_hcd *hcd)
 	if (time_before (jiffies, ehci->next_statechange))
 		msleep(5);
 	del_timer_sync(&ehci->watchdog);
-	del_timer_sync(&ehci->iaa_watchdog);
 
 	spin_lock_irq (&ehci->lock);
 

drivers/usb/host/ehci-q.c

@@ -1173,8 +1173,6 @@ static void end_unlink_async (struct ehci_hcd *ehci)
 	struct ehci_qh		*qh = ehci->async_unlink;
 	struct ehci_qh		*next;
 
-	iaa_watchdog_done(ehci);
-
 	// qh->hw_next = cpu_to_hc32(qh->qh_dma);
 	qh->qh_state = QH_STATE_IDLE;
 	qh->qh_next.qh = NULL;
@@ -1243,7 +1241,7 @@ static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 
 	ehci_writel(ehci, ehci->command | CMD_IAAD, &ehci->regs->command);
 	(void)ehci_readl(ehci, &ehci->regs->command);
-	iaa_watchdog_start(ehci);
+	ehci_enable_event(ehci, EHCI_HRTIMER_IAA_WATCHDOG, true);
 }
 
 /*-------------------------------------------------------------------------*/

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 */
 };

drivers/usb/host/ehci.h

@@ -84,6 +84,7 @@ enum ehci_hrtimer_event {
 	EHCI_HRTIMER_POLL_DEAD,		/* Wait for dead controller to stop */
 	EHCI_HRTIMER_UNLINK_INTR,	/* Wait for interrupt QH unlink */
 	EHCI_HRTIMER_FREE_ITDS,		/* Wait for unused iTDs and siTDs */
+	EHCI_HRTIMER_IAA_WATCHDOG,	/* Handle lost IAA interrupts */
 	EHCI_HRTIMER_DISABLE_PERIODIC,	/* Wait to disable periodic sched */
 	EHCI_HRTIMER_DISABLE_ASYNC,	/* Wait to disable async sched */
 	EHCI_HRTIMER_NUM_EVENTS		/* Must come last */
@@ -168,7 +169,6 @@ struct ehci_hcd {			/* one per controller */
 	struct dma_pool		*itd_pool;	/* itd per iso urb */
 	struct dma_pool		*sitd_pool;	/* sitd per split iso urb */
 
-	struct timer_list	iaa_watchdog;
 	struct timer_list	watchdog;
 	unsigned long		actions;
 	unsigned		periodic_stamp;
@@ -228,20 +228,6 @@ static inline struct usb_hcd *ehci_to_hcd (struct ehci_hcd *ehci)
 	return container_of ((void *) ehci, struct usb_hcd, hcd_priv);
 }
 
-
-static inline void
-iaa_watchdog_start(struct ehci_hcd *ehci)
-{
-	WARN_ON(timer_pending(&ehci->iaa_watchdog));
-	mod_timer(&ehci->iaa_watchdog,
-			jiffies + msecs_to_jiffies(EHCI_IAA_MSECS));
-}
-
-static inline void iaa_watchdog_done(struct ehci_hcd *ehci)
-{
-	del_timer(&ehci->iaa_watchdog);
-}
-
 enum ehci_timer_action {
 	TIMER_IO_WATCHDOG,
 	TIMER_ASYNC_SHRINK,