usb: dwc3: workaround: bogus hibernation events

Revision 2.20a of the core has a known issue
which would generate bogus hibernation events
_and_ random failures on USB CV TD.9.23 test
case.

The suggested workaround is to ignore hibernation
events which don't match currently connected
speed.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -2378,6 +2378,30 @@ static void dwc3_gadget_linksts_change_interrupt(struct dwc3 *dwc,
 	dev_vdbg(dwc->dev, "%s link %d\n", __func__, dwc->link_state);
 }
 
+static void dwc3_gadget_hibernation_interrupt(struct dwc3 *dwc,
+		unsigned int evtinfo)
+{
+	unsigned int is_ss = evtinfo & BIT(4);
+
+	/**
+	 * WORKAROUND: DWC3 revison 2.20a with hibernation support
+	 * have a known issue which can cause USB CV TD.9.23 to fail
+	 * randomly.
+	 *
+	 * Because of this issue, core could generate bogus hibernation
+	 * events which SW needs to ignore.
+	 *
+	 * Refers to:
+	 *
+	 * STAR#9000546576: Device Mode Hibernation: Issue in USB 2.0
+	 * Device Fallback from SuperSpeed
+	 */
+	if (is_ss ^ (dwc->speed == USB_SPEED_SUPER))
+		return;
+
+	/* enter hibernation here */
+}
+
 static void dwc3_gadget_interrupt(struct dwc3 *dwc,
 		const struct dwc3_event_devt *event)
 {
@@ -2394,6 +2418,13 @@ static void dwc3_gadget_interrupt(struct dwc3 *dwc,
 	case DWC3_DEVICE_EVENT_WAKEUP:
 		dwc3_gadget_wakeup_interrupt(dwc);
 		break;
+	case DWC3_DEVICE_EVENT_HIBER_REQ:
+		if (dev_WARN_ONCE(dwc->dev, !dwc->has_hibernation,
+					"unexpected hibernation event\n"))
+			break;
+
+		dwc3_gadget_hibernation_interrupt(dwc, event->event_info);
+		break;
 	case DWC3_DEVICE_EVENT_LINK_STATUS_CHANGE:
 		dwc3_gadget_linksts_change_interrupt(dwc, event->event_info);
 		break;