diff --git a/Ubiquitous/XiZi_AIoT/services/drivers/usb/components/port/xhci/xhci.c b/Ubiquitous/XiZi_AIoT/services/drivers/usb/components/port/xhci/xhci.c
index 7d0746025..bcb0815a3 100644
--- a/Ubiquitous/XiZi_AIoT/services/drivers/usb/components/port/xhci/xhci.c
+++ b/Ubiquitous/XiZi_AIoT/services/drivers/usb/components/port/xhci/xhci.c
@@ -2733,6 +2733,8 @@ static void xhci_transfer ( struct xhci_host *xhci,
 //    trans_trb = trb->transfer;
     trans_ring = (struct xhci_ring *)(vir_addr); /* to align addr is ring base */
 	pending = &trans_ring->evt; /* preserve event trb pending to handle */
+
+/* We must pay attention on whether the result of eidx should increase by 1 or not, when we begin to debug. */
     eidx = (trb->transfer - phy_addr)/sizeof(union xhci_trb) + 1; /* calculate current evt trb index */	
 
 	/* Identify slot */