usb: dwc2: host: Add scheduler tracing

In preparation for future changes to the scheduler let's add some
tracing that makes it easy for us to see what's happening.  By default
this tracing will be off.

By changing "core.h" you can easily trace to ftrace, the console, or
nowhere.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
index c409843..1faf1c6 100644
--- a/drivers/usb/dwc2/hcd_intr.c
+++ b/drivers/usb/dwc2/hcd_intr.c
@@ -138,13 +138,17 @@
 	while (qh_entry != &hsotg->periodic_sched_inactive) {
 		qh = list_entry(qh_entry, struct dwc2_qh, qh_list_entry);
 		qh_entry = qh_entry->next;
-		if (dwc2_frame_num_le(qh->sched_frame, hsotg->frame_number))
+		if (dwc2_frame_num_le(qh->sched_frame, hsotg->frame_number)) {
+			dwc2_sch_vdbg(hsotg, "QH=%p ready fn=%04x, sch=%04x\n",
+				      qh, hsotg->frame_number, qh->sched_frame);
+
 			/*
 			 * Move QH to the ready list to be executed next
 			 * (micro)frame
 			 */
 			list_move_tail(&qh->qh_list_entry,
 				  &hsotg->periodic_sched_ready);
+		}
 	}
 	tr_type = dwc2_hcd_select_transactions(hsotg);
 	if (tr_type != DWC2_TRANSACTION_NONE)