dcd/dwc2: fix suspend interrupt indefinitely disabled on AT32F405

Author: peppapighs

src/portable/synopsys/dwc2/dcd_dwc2.c

@@ -1025,6 +1025,8 @@ static void handle_ep_irq(uint8_t rhport, uint8_t dir) {
   }
 }
 
+extern bool tud_connected(void);
+
 /* Interrupt Hierarchy
                  DIEPINT  DIEPINT
                     \       /
@@ -1060,8 +1062,12 @@ void dcd_int_handler(uint8_t rhport) {
 
   if (gintsts & GINTSTS_USBSUSP) {
     dwc2->gintsts = GINTSTS_USBSUSP;
-    dwc2->gintmsk &= ~GINTMSK_USBSUSPM;
-    dcd_event_bus_signal(rhport, DCD_EVENT_SUSPEND, true);
+    // Some MCUs such as AT32F405 receives SUSPEND event before the device is
+    // connected. We should skip handling the event if not currently connected.
+    if (tud_connected()) {
+      dwc2->gintmsk &= ~GINTMSK_USBSUSPM;
+      dcd_event_bus_signal(rhport, DCD_EVENT_SUSPEND, true);
+    }
   }
 
   if (gintsts & GINTSTS_WKUINT) {