HI  Hao Wu: This exception is executed Therefore, the modifications provided may not be applicable. Resetting a Root Hub Port cause the exception. Although the probability is not high.So I think it still needs to be placed after the Root Hub prot reset. // // 4.3.1 Resetting a Root Hub Port // 1) Write the PORTSC register with the Port Reset (PR) bit set to '1'. // State |= XHC_PORTSC_RESET; XhcWriteOpReg (Xhc, Offset, State); XhcWaitOpRegBit (Xhc, Offset, XHC_PORTSC_PRC, TRUE, XHC_GENERIC_TIMEOUT); if ((((State & 0x1e0) >> 5) == 6) && ((State & 3) == 0)) { // // Usb 3.2 spec 7.5.2 // When the USB state machine is Inactive state, the device is abnormal. // eSS.Inactive is a state where a link has failed Enhanced SuperSpeed operation.Software // is required for warm reset intervention.This flag only applies to USB3 protocol ports. // State |= 0x80000000; XhcWriteOpReg (Xhc, Offset, State); XhcWaitOpRegBit (Xhc, Offset, XHC_PORTSC_PRC, TRUE, XHC_GENERIC_TIMEOUT); DEBUG ((DEBUG_INFO, "Warm Reset Successful! \n")); } break; Best Regards Thanks!