USB: EHCI: use hrtimer for async schedule

This patch (as1576) adds hrtimer support for managing ehci-hcd's
async schedule.  Just as with the earlier change to the periodic
schedule management, two new hrtimer events take care of everything.

One event polls at 1-ms intervals to see when the Asynchronous
Schedule Status (ASS) flag matches the Asynchronous Schedule Enable
(ASE) value; the schedule's state must not be changed until it does.
The other event delays for 15 ms after the async schedule becomes
empty before turning it off.

The new events replace a busy-wait poll and a kernel timer usage.
They also replace the rather illogical method currently used for
indicating the async schedule should be turned off: attempting to
unlink the dedicated QH at the head of the async list.

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

1 files changed, 30 insertions, 38 deletions

diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 285d5a0f3f7..d68764ef447 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -964,6 +964,30 @@ done:
 
 /*-------------------------------------------------------------------------*/
 
+static void enable_async(struct ehci_hcd *ehci)
+{
+	if (ehci->async_count++)
+		return;
+
+	/* Stop waiting to turn off the async schedule */
+	ehci->enabled_hrtimer_events &= ~BIT(EHCI_HRTIMER_DISABLE_ASYNC);
+
+	/* Don't start the schedule until ASS is 0 */
+	ehci_poll_ASS(ehci);
+}
+
+static void disable_async(struct ehci_hcd *ehci)
+{
+	if (--ehci->async_count)
+		return;
+
+	/* The async schedule and async_unlink list are supposed to be empty */
+	WARN_ON(ehci->async->qh_next.qh || ehci->async_unlink);
+
+	/* Don't turn off the schedule until ASS is 1 */
+	ehci_poll_ASS(ehci);
+}
+
 /* move qh (and its qtds) onto async queue; maybe enable queue.  */
 
 static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
@@ -977,24 +1001,11 @@ static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 
 	WARN_ON(qh->qh_state != QH_STATE_IDLE);
 
-	/* (re)start the async schedule? */
-	head = ehci->async;
-	timer_action_done (ehci, TIMER_ASYNC_OFF);
-	if (!head->qh_next.qh) {
-		if (!(ehci->command & CMD_ASE)) {
-			/* in case a clear of CMD_ASE didn't take yet */
-			(void)handshake(ehci, &ehci->regs->status,
-					STS_ASS, 0, 150);
-			ehci->command |= CMD_ASE;
-			ehci_writel(ehci, ehci->command, &ehci->regs->command);
-			/* posted write need not be known to HC yet ... */
-		}
-	}
-
 	/* clear halt and/or toggle; and maybe recover from silicon quirk */
 	qh_refresh(ehci, qh);
 
 	/* splice right after start */
+	head = ehci->async;
 	qh->qh_next = head->qh_next;
 	qh->hw->hw_next = head->hw->hw_next;
 	wmb ();
@@ -1005,6 +1016,8 @@ static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 	qh->xacterrs = 0;
 	qh->qh_state = QH_STATE_LINKED;
 	/* qtd completions reported later by interrupt */
+
+	enable_async(ehci);
 }
 
 /*-------------------------------------------------------------------------*/
@@ -1173,16 +1186,10 @@ static void end_unlink_async (struct ehci_hcd *ehci)
 
 	qh_completions (ehci, qh);
 
-	if (!list_empty(&qh->qtd_list) && ehci->rh_state == EHCI_RH_RUNNING) {
+	if (!list_empty(&qh->qtd_list) && ehci->rh_state == EHCI_RH_RUNNING)
 		qh_link_async (ehci, qh);
-	} else {
-		/* it's not free to turn the async schedule on/off; leave it
-		 * active but idle for a while once it empties.
-		 */
-		if (ehci->rh_state == EHCI_RH_RUNNING
-				&& ehci->async->qh_next.qh == NULL)
-			timer_action (ehci, TIMER_ASYNC_OFF);
-	}
+
+	disable_async(ehci);
 
 	if (next) {
 		ehci->async_unlink = NULL;
@@ -1210,21 +1217,6 @@ static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 		BUG ();
 #endif
 
-	/* stop async schedule right now? */
-	if (unlikely (qh == ehci->async)) {
-		/* can't get here without STS_ASS set */
-		if (ehci->rh_state != EHCI_RH_HALTED
-				&& !ehci->async_unlink) {
-			/* ... and CMD_IAAD clear */
-			ehci->command &= ~CMD_ASE;
-			ehci_writel(ehci, ehci->command, &ehci->regs->command);
-			wmb ();
-			// handshake later, if we need to
-			timer_action_done (ehci, TIMER_ASYNC_OFF);
-		}
-		return;
-	}
-
 	qh->qh_state = QH_STATE_UNLINK;
 	ehci->async_unlink = qh;
 	if (!qh->unlink_next)