[PATCH] UHCI: Improve FSBR-off timing

This patch (as707) improves the FSBR operation in uhci-hcd by turning it
off more quickly when it isn't needed.  FSBR puts a noticeable load on a
computer's PCI bus, so it should be disabled as soon as possible when it
isn't in use.  The patch leaves it running for only 10 ms after the last
URB stops using it, on the theory that this should be long enough for a
driver to submit another URB if it wants keep FSBR going.

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

1 files changed, 51 insertions, 20 deletions

diff --git a/drivers/usb/host/uhci-q.c b/drivers/usb/host/uhci-q.c
index b173d914d74..c9d72ac0a1d 100644
--- a/drivers/usb/host/uhci-q.c
+++ b/drivers/usb/host/uhci-q.c
@@ -64,16 +64,30 @@ static void uhci_add_fsbr(struct uhci_hcd *uhci, struct urb *urb)
 		urbp->fsbr = 1;
 }
 
-static void uhci_qh_wants_fsbr(struct uhci_hcd *uhci, struct uhci_qh *qh)
+static void uhci_urbp_wants_fsbr(struct uhci_hcd *uhci, struct urb_priv *urbp)
 {
-	struct urb_priv *urbp =
-			list_entry(qh->queue.next, struct urb_priv, node);
-
 	if (urbp->fsbr) {
-		uhci->fsbr_jiffies = jiffies;
+		uhci->fsbr_is_wanted = 1;
 		if (!uhci->fsbr_is_on)
 			uhci_fsbr_on(uhci);
+		else if (uhci->fsbr_expiring) {
+			uhci->fsbr_expiring = 0;
+			del_timer(&uhci->fsbr_timer);
+		}
+	}
+}
+
+static void uhci_fsbr_timeout(unsigned long _uhci)
+{
+	struct uhci_hcd *uhci = (struct uhci_hcd *) _uhci;
+	unsigned long flags;
+
+	spin_lock_irqsave(&uhci->lock, flags);
+	if (uhci->fsbr_expiring) {
+		uhci->fsbr_expiring = 0;
+		uhci_fsbr_off(uhci);
 	}
+	spin_unlock_irqrestore(&uhci->lock, flags);
 }
 
 
@@ -287,7 +301,7 @@ static int uhci_cleanup_queue(struct uhci_hcd *uhci, struct uhci_qh *qh,
 	if (qh->type == USB_ENDPOINT_XFER_ISOC) {
 		ret = (uhci->frame_number + uhci->is_stopped !=
 				qh->unlink_frame);
-		return ret;
+		goto done;
 	}
 
 	/* If the URB isn't first on its queue, adjust the link pointer
@@ -304,24 +318,26 @@ static int uhci_cleanup_queue(struct uhci_hcd *uhci, struct uhci_qh *qh,
 		td = list_entry(urbp->td_list.prev, struct uhci_td,
 				list);
 		ptd->link = td->link;
-		return ret;
+		goto done;
 	}
 
 	/* If the QH element pointer is UHCI_PTR_TERM then then currently
 	 * executing URB has already been unlinked, so this one isn't it. */
 	if (qh_element(qh) == UHCI_PTR_TERM)
-		return ret;
+		goto done;
 	qh->element = UHCI_PTR_TERM;
 
 	/* Control pipes have to worry about toggles */
 	if (qh->type == USB_ENDPOINT_XFER_CONTROL)
-		return ret;
+		goto done;
 
 	/* Save the next toggle value */
 	WARN_ON(list_empty(&urbp->td_list));
 	td = list_entry(urbp->td_list.next, struct uhci_td, list);
 	qh->needs_fixup = 1;
 	qh->initial_toggle = uhci_toggle(td_token(td));
+
+done:
 	return ret;
 }
 
@@ -1175,7 +1191,7 @@ static int uhci_urb_enqueue(struct usb_hcd *hcd,
 	 * queue isn't stopped. */
 	if (qh->queue.next == &urbp->node && !qh->is_stopped) {
 		uhci_activate_qh(uhci, qh);
-		uhci_qh_wants_fsbr(uhci, qh);
+		uhci_urbp_wants_fsbr(uhci, urbp);
 	}
 	goto done;
 
@@ -1404,7 +1420,7 @@ static int uhci_advance_check(struct uhci_hcd *uhci, struct uhci_qh *qh)
 	unsigned status;
 
 	if (qh->type == USB_ENDPOINT_XFER_ISOC)
-		return ret;
+		goto done;
 
 	/* Treat an UNLINKING queue as though it hasn't advanced.
 	 * This is okay because reactivation will treat it as though
@@ -1427,21 +1443,24 @@ static int uhci_advance_check(struct uhci_hcd *uhci, struct uhci_qh *qh)
 			/* We're okay, the queue has advanced */
 			qh->wait_expired = 0;
 			qh->advance_jiffies = jiffies;
-			return ret;
+			goto done;
 		}
 		ret = 0;
 	}
 
 	/* The queue hasn't advanced; check for timeout */
-	if (!qh->wait_expired && time_after(jiffies,
-			qh->advance_jiffies + QH_WAIT_TIMEOUT)) {
+	if (qh->wait_expired)
+		goto done;
+
+	if (time_after(jiffies, qh->advance_jiffies + QH_WAIT_TIMEOUT)) {
 
 		/* Detect the Intel bug and work around it */
 		if (qh->post_td && qh_element(qh) ==
 				cpu_to_le32(qh->post_td->dma_handle)) {
 			qh->element = qh->post_td->link;
 			qh->advance_jiffies = jiffies;
-			return 1;
+			ret = 1;
+			goto done;
 		}
 
 		qh->wait_expired = 1;
@@ -1452,7 +1471,14 @@ static int uhci_advance_check(struct uhci_hcd *uhci, struct uhci_qh *qh)
 		 * starts moving again. */
 		if (urbp && urbp->fsbr && !(status & TD_CTRL_IOC))
 			uhci_unlink_qh(uhci, qh);
+
+	} else {
+		/* Unmoving but not-yet-expired queues keep FSBR alive */
+		if (urbp)
+			uhci_urbp_wants_fsbr(uhci, urbp);
 	}
+
+done:
 	return ret;
 }
 
@@ -1472,6 +1498,7 @@ static void uhci_scan_schedule(struct uhci_hcd *uhci, struct pt_regs *regs)
 	uhci->scan_in_progress = 1;
 rescan:
 	uhci->need_rescan = 0;
+	uhci->fsbr_is_wanted = 0;
 
 	uhci_clear_next_interrupt(uhci);
 	uhci_get_current_frame_number(uhci);
@@ -1487,8 +1514,10 @@ rescan:
 
 			if (uhci_advance_check(uhci, qh)) {
 				uhci_scan_qh(uhci, qh, regs);
-				if (qh->state == QH_STATE_ACTIVE)
-					uhci_qh_wants_fsbr(uhci, qh);
+				if (qh->state == QH_STATE_ACTIVE) {
+					uhci_urbp_wants_fsbr(uhci,
+	list_entry(qh->queue.next, struct urb_priv, node));
+				}
 			}
 		}
 	}
@@ -1498,9 +1527,11 @@ rescan:
 		goto rescan;
 	uhci->scan_in_progress = 0;
 
-	if (uhci->fsbr_is_on && time_after(jiffies,
-			uhci->fsbr_jiffies + FSBR_OFF_DELAY))
-		uhci_fsbr_off(uhci);
+	if (uhci->fsbr_is_on && !uhci->fsbr_is_wanted &&
+			!uhci->fsbr_expiring) {
+		uhci->fsbr_expiring = 1;
+		mod_timer(&uhci->fsbr_timer, jiffies + FSBR_OFF_DELAY);
+	}
 
 	if (list_empty(&uhci->skel_unlink_qh->node))
 		uhci_clear_next_interrupt(uhci);