USB: EHCI: add separate IAA watchdog timer

This patch (as1028) was mostly written by David Brownell; I made only
a few changes (extra log info and a small bug fix -- which might
account for why David's version had to be reverted).  It adds a new
watchdog timer to the ehci-hcd driver to be used exclusively for
detecting lost or missing IAA notifications.

Previously a shared timer had been used, which may have led to some
problems as reported by Christian Hoffmann.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-dbg.c

@@ -786,9 +786,7 @@ static ssize_t fill_registers_buffer(struct debug_buffer *buf)
 	}
 
 	if (ehci->reclaim) {
-		temp = scnprintf (next, size, "reclaim qh %p%s\n",
-				ehci->reclaim,
-				ehci->reclaim_ready ? " ready" : "");
+		temp = scnprintf(next, size, "reclaim qh %p\n", ehci->reclaim);
 		size -= temp;
 		next += temp;
 	}

drivers/usb/host/ehci-hcd.c

@@ -110,7 +110,7 @@ static const char	hcd_name [] = "ehci_hcd";
 #define	EHCI_TUNE_MULT_TT	1
 #define	EHCI_TUNE_FLS		2	/* (small) 256 frame schedule */
 
-#define EHCI_IAA_JIFFIES	(HZ/100)	/* arbitrary; ~10 msec */
+#define EHCI_IAA_MSECS		10		/* arbitrary */
 #define EHCI_IO_JIFFIES		(HZ/10)		/* io watchdog > irq_thresh */
 #define EHCI_ASYNC_JIFFIES	(HZ/20)		/* async idle timeout */
 #define EHCI_SHRINK_JIFFIES	(HZ/200)	/* async qh unlink delay */
@@ -267,6 +267,7 @@ static void ehci_quiesce (struct ehci_hcd *ehci)
 
 /*-------------------------------------------------------------------------*/
 
+static void end_unlink_async(struct ehci_hcd *ehci);
 static void ehci_work(struct ehci_hcd *ehci);
 
 #include "ehci-hub.c"
@@ -276,25 +277,41 @@ static void ehci_work(struct ehci_hcd *ehci);
 
 /*-------------------------------------------------------------------------*/
 
-static void ehci_watchdog (unsigned long param)
+static void ehci_iaa_watchdog(unsigned long param)
 {
 	struct ehci_hcd		*ehci = (struct ehci_hcd *) param;
 	unsigned long		flags;
+	u32			status, cmd;
 
 	spin_lock_irqsave (&ehci->lock, flags);
+	WARN_ON(!ehci->reclaim);
 
-	/* lost IAA irqs wedge things badly; seen with a vt8235 */
+	status = ehci_readl(ehci, &ehci->regs->status);
+	cmd = ehci_readl(ehci, &ehci->regs->command);
+	ehci_dbg(ehci, "IAA watchdog: status %x cmd %x\n", status, cmd);
+
+	/* lost IAA irqs wedge things badly; seen first with a vt8235 */
 	if (ehci->reclaim) {
-		u32		status = ehci_readl(ehci, &ehci->regs->status);
 		if (status & STS_IAA) {
 			ehci_vdbg (ehci, "lost IAA\n");
 			COUNT (ehci->stats.lost_iaa);
 			ehci_writel(ehci, STS_IAA, &ehci->regs->status);
-			ehci->reclaim_ready = 1;
 		}
+		ehci_writel(ehci, cmd & ~CMD_IAAD, &ehci->regs->command);
+		end_unlink_async(ehci);
 	}
 
- 	/* stop async processing after it's idled a bit */
+	spin_unlock_irqrestore(&ehci->lock, flags);
+}
+
+static void ehci_watchdog(unsigned long param)
+{
+	struct ehci_hcd		*ehci = (struct ehci_hcd *) param;
+	unsigned long		flags;
+
+	spin_lock_irqsave(&ehci->lock, flags);
+
+	/* stop async processing after it's idled a bit */
 	if (test_bit (TIMER_ASYNC_OFF, &ehci->actions))
 		start_unlink_async (ehci, ehci->async);
 
@@ -364,8 +381,6 @@ static void ehci_port_power (struct ehci_hcd *ehci, int is_on)
 static void ehci_work (struct ehci_hcd *ehci)
 {
 	timer_action_done (ehci, TIMER_IO_WATCHDOG);
-	if (ehci->reclaim_ready)
-		end_unlink_async (ehci);
 
 	/* another CPU may drop ehci->lock during a schedule scan while
 	 * it reports urb completions.  this flag guards against bogus
@@ -400,6 +415,7 @@ 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);
 	if (HC_IS_RUNNING (hcd->state))
@@ -448,6 +464,10 @@ 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;
+
 	/*
 	 * hw default: 1K periodic list heads, one per frame.
 	 * periodic_size can shrink by USBCMD update if hcc_params allows.
@@ -464,7 +484,6 @@ static int ehci_init(struct usb_hcd *hcd)
 		ehci->i_thresh = 2 + HCC_ISOC_THRES(hcc_params);
 
 	ehci->reclaim = NULL;
-	ehci->reclaim_ready = 0;
 	ehci->next_uframe = -1;
 
 	/*
@@ -655,8 +674,7 @@ static irqreturn_t ehci_irq (struct usb_hcd *hcd)
 	/* complete the unlinking of some qh [4.15.2.3] */
 	if (status & STS_IAA) {
 		COUNT (ehci->stats.reclaim);
-		ehci->reclaim_ready = 1;
-		bh = 1;
+		end_unlink_async(ehci);
 	}
 
 	/* remote wakeup [4.3.1] */
@@ -762,10 +780,16 @@ static int ehci_urb_enqueue (
 
 static void unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 {
-	/* if we need to use IAA and it's busy, defer */
-	if (qh->qh_state == QH_STATE_LINKED
-			&& ehci->reclaim
-			&& HC_IS_RUNNING (ehci_to_hcd(ehci)->state)) {
+	/* failfast */
+	if (!HC_IS_RUNNING(ehci_to_hcd(ehci)->state))
+		end_unlink_async(ehci);
+
+	/* if it's not linked then there's nothing to do */
+	if (qh->qh_state != QH_STATE_LINKED)
+		;
+
+	/* defer till later if busy */
+	else if (ehci->reclaim) {
 		struct ehci_qh		*last;
 
 		for (last = ehci->reclaim;
@@ -775,12 +799,8 @@ static void unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 		qh->qh_state = QH_STATE_UNLINK_WAIT;
 		last->reclaim = qh;
 
-	/* bypass IAA if the hc can't care */
-	} else if (!HC_IS_RUNNING (ehci_to_hcd(ehci)->state) && ehci->reclaim)
-		end_unlink_async (ehci);
-
-	/* something else might have unlinked the qh by now */
-	if (qh->qh_state == QH_STATE_LINKED)
+	/* start IAA cycle */
+	} else
 		start_unlink_async (ehci, qh);
 }
 
@@ -807,7 +827,19 @@ static int ehci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
 		qh = (struct ehci_qh *) urb->hcpriv;
 		if (!qh)
 			break;
-		unlink_async (ehci, qh);
+		switch (qh->qh_state) {
+		case QH_STATE_LINKED:
+		case QH_STATE_COMPLETING:
+			unlink_async(ehci, qh);
+			break;
+		case QH_STATE_UNLINK:
+		case QH_STATE_UNLINK_WAIT:
+			/* already started */
+			break;
+		case QH_STATE_IDLE:
+			WARN_ON(1);
+			break;
+		}
 		break;
 
 	case PIPE_INTERRUPT:
@@ -899,6 +931,7 @@ rescan:
 		unlink_async (ehci, qh);
 		/* FALL THROUGH */
 	case QH_STATE_UNLINK:		/* wait for hw to finish? */
+	case QH_STATE_UNLINK_WAIT:
 idle_timeout:
 		spin_unlock_irqrestore (&ehci->lock, flags);
 		schedule_timeout_uninterruptible(1);

drivers/usb/host/ehci-hub.c

@@ -134,7 +134,7 @@ static int ehci_bus_suspend (struct usb_hcd *hcd)
 	}
 	ehci->command = ehci_readl(ehci, &ehci->regs->command);
 	if (ehci->reclaim)
-		ehci->reclaim_ready = 1;
+		end_unlink_async(ehci);
 	ehci_work(ehci);
 
 	/* Unlike other USB host controller types, EHCI doesn't have

drivers/usb/host/ehci-pci.c

@@ -305,7 +305,7 @@ static int ehci_pci_resume(struct usb_hcd *hcd)
 	/* emptying the schedule aborts any urbs */
 	spin_lock_irq(&ehci->lock);
 	if (ehci->reclaim)
-		ehci->reclaim_ready = 1;
+		end_unlink_async(ehci);
 	ehci_work(ehci);
 	spin_unlock_irq(&ehci->lock);
 

drivers/usb/host/ehci-q.c

@@ -973,7 +973,7 @@ static void end_unlink_async (struct ehci_hcd *ehci)
 	struct ehci_qh		*qh = ehci->reclaim;
 	struct ehci_qh		*next;
 
-	timer_action_done (ehci, TIMER_IAA_WATCHDOG);
+	iaa_watchdog_done(ehci);
 
 	// qh->hw_next = cpu_to_hc32(qh->qh_dma);
 	qh->qh_state = QH_STATE_IDLE;
@@ -983,7 +983,6 @@ static void end_unlink_async (struct ehci_hcd *ehci)
 	/* other unlink(s) may be pending (in QH_STATE_UNLINK_WAIT) */
 	next = qh->reclaim;
 	ehci->reclaim = next;
-	ehci->reclaim_ready = 0;
 	qh->reclaim = NULL;
 
 	qh_completions (ehci, qh);
@@ -1059,11 +1058,10 @@ static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 		return;
 	}
 
-	ehci->reclaim_ready = 0;
 	cmd |= CMD_IAAD;
 	ehci_writel(ehci, cmd, &ehci->regs->command);
 	(void)ehci_readl(ehci, &ehci->regs->command);
-	timer_action (ehci, TIMER_IAA_WATCHDOG);
+	iaa_watchdog_start(ehci);
 }
 
 /*-------------------------------------------------------------------------*/

drivers/usb/host/ehci.h

@@ -74,7 +74,6 @@ struct ehci_hcd {			/* one per controller */
 	/* async schedule support */
 	struct ehci_qh		*async;
 	struct ehci_qh		*reclaim;
-	unsigned		reclaim_ready : 1;
 	unsigned		scanning : 1;
 
 	/* periodic schedule support */
@@ -105,6 +104,7 @@ 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		stamp;
@@ -148,9 +148,21 @@ static inline struct usb_hcd *ehci_to_hcd (struct ehci_hcd *ehci)
 }
 
 
+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_IAA_WATCHDOG,
 	TIMER_ASYNC_SHRINK,
 	TIMER_ASYNC_OFF,
 };
@@ -168,9 +180,6 @@ timer_action (struct ehci_hcd *ehci, enum ehci_timer_action action)
 		unsigned long t;
 
 		switch (action) {
-		case TIMER_IAA_WATCHDOG:
-			t = EHCI_IAA_JIFFIES;
-			break;
 		case TIMER_IO_WATCHDOG:
 			t = EHCI_IO_JIFFIES;
 			break;
@@ -187,8 +196,7 @@ timer_action (struct ehci_hcd *ehci, enum ehci_timer_action action)
 		// async queue SHRINK often precedes IAA.  while it's ready
 		// to go OFF neither can matter, and afterwards the IO
 		// watchdog stops unless there's still periodic traffic.
-		if (action != TIMER_IAA_WATCHDOG
-				&& t > ehci->watchdog.expires
+		if (time_before_eq(t, ehci->watchdog.expires)
 				&& timer_pending (&ehci->watchdog))
 			return;
 		mod_timer (&ehci->watchdog, t);