1 files changed, 77 insertions, 4 deletions

diff --git a/drivers/usb/dwc2/hcd_queue.c b/drivers/usb/dwc2/hcd_queue.c
index fcd1676c7f0b..e34ad5e65350 100644
--- a/drivers/usb/dwc2/hcd_queue.c
+++ b/drivers/usb/dwc2/hcd_queue.c
@@ -58,6 +58,9 @@
 /* Wait this long before releasing periodic reservation */
 #define DWC2_UNRESERVE_DELAY (msecs_to_jiffies(5))
 
+/* If we get a NAK, wait this long before retrying */
+#define DWC2_RETRY_WAIT_DELAY (msecs_to_jiffies(1))
+
 /**
  * dwc2_periodic_channel_available() - Checks that a channel is available for a
  * periodic transfer
@@ -1441,6 +1444,55 @@ static void dwc2_deschedule_periodic(struct dwc2_hsotg *hsotg,
 }
 
 /**
+ * dwc2_wait_timer_fn() - Timer function to re-queue after waiting
+ *
+ * As per the spec, a NAK indicates that "a function is temporarily unable to
+ * transmit or receive data, but will eventually be able to do so without need
+ * of host intervention".
+ *
+ * That means that when we encounter a NAK we're supposed to retry.
+ *
+ * ...but if we retry right away (from the interrupt handler that saw the NAK)
+ * then we can end up with an interrupt storm (if the other side keeps NAKing
+ * us) because on slow enough CPUs it could take us longer to get out of the
+ * interrupt routine than it takes for the device to send another NAK.  That
+ * leads to a constant stream of NAK interrupts and the CPU locks.
+ *
+ * ...so instead of retrying right away in the case of a NAK we'll set a timer
+ * to retry some time later.  This function handles that timer and moves the
+ * qh back to the "inactive" list, then queues transactions.
+ *
+ * @t: Pointer to wait_timer in a qh.
+ */
+static void dwc2_wait_timer_fn(struct timer_list *t)
+{
+	struct dwc2_qh *qh = from_timer(qh, t, wait_timer);
+	struct dwc2_hsotg *hsotg = qh->hsotg;
+	unsigned long flags;
+
+	spin_lock_irqsave(&hsotg->lock, flags);
+
+	/*
+	 * We'll set wait_timer_cancel to true if we want to cancel this
+	 * operation in dwc2_hcd_qh_unlink().
+	 */
+	if (!qh->wait_timer_cancel) {
+		enum dwc2_transaction_type tr_type;
+
+		qh->want_wait = false;
+
+		list_move(&qh->qh_list_entry,
+			  &hsotg->non_periodic_sched_inactive);
+
+		tr_type = dwc2_hcd_select_transactions(hsotg);
+		if (tr_type != DWC2_TRANSACTION_NONE)
+			dwc2_hcd_queue_transactions(hsotg, tr_type);
+	}
+
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+}
+
+/**
  * dwc2_qh_init() - Initializes a QH structure
  *
  * @hsotg: The HCD state structure for the DWC OTG controller
@@ -1468,6 +1520,7 @@ static void dwc2_qh_init(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh,
 	/* Initialize QH */
 	qh->hsotg = hsotg;
 	timer_setup(&qh->unreserve_timer, dwc2_unreserve_timer_fn, 0);
+	timer_setup(&qh->wait_timer, dwc2_wait_timer_fn, 0);
 	qh->ep_type = ep_type;
 	qh->ep_is_in = ep_is_in;
 
@@ -1628,6 +1681,16 @@ void dwc2_hcd_qh_free(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 		dwc2_do_unreserve(hsotg, qh);
 		spin_unlock_irqrestore(&hsotg->lock, flags);
 	}
+
+	/*
+	 * We don't have the lock so we can safely wait until the wait timer
+	 * finishes.  Of course, at this point in time we'd better have set
+	 * wait_timer_active to false so if this timer was still pending it
+	 * won't do anything anyway, but we want it to finish before we free
+	 * memory.
+	 */
+	del_timer_sync(&qh->wait_timer);
+
 	dwc2_host_put_tt_info(hsotg, qh->dwc_tt);
 
 	if (qh->desc_list)
@@ -1663,9 +1726,16 @@ int dwc2_hcd_qh_add(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 		qh->start_active_frame = hsotg->frame_number;
 		qh->next_active_frame = qh->start_active_frame;
 
-		/* Always start in inactive schedule */
-		list_add_tail(&qh->qh_list_entry,
-			      &hsotg->non_periodic_sched_inactive);
+		if (qh->want_wait) {
+			list_add_tail(&qh->qh_list_entry,
+				      &hsotg->non_periodic_sched_waiting);
+			qh->wait_timer_cancel = false;
+			mod_timer(&qh->wait_timer,
+				  jiffies + DWC2_RETRY_WAIT_DELAY + 1);
+		} else {
+			list_add_tail(&qh->qh_list_entry,
+				      &hsotg->non_periodic_sched_inactive);
+		}
 		return 0;
 	}
 
@@ -1695,6 +1765,9 @@ void dwc2_hcd_qh_unlink(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 
 	dev_vdbg(hsotg->dev, "%s()\n", __func__);
 
+	/* If the wait_timer is pending, this will stop it from acting */
+	qh->wait_timer_cancel = true;
+
 	if (list_empty(&qh->qh_list_entry))
 		/* QH is not in a schedule */
 		return;
@@ -1903,7 +1976,7 @@ void dwc2_hcd_qh_deactivate(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh,
 	if (dwc2_qh_is_non_per(qh)) {
 		dwc2_hcd_qh_unlink(hsotg, qh);
 		if (!list_empty(&qh->qtd_list))
-			/* Add back to inactive non-periodic schedule */
+			/* Add back to inactive/waiting non-periodic schedule */
 			dwc2_hcd_qh_add(hsotg, qh);
 		return;
 	}