When an idle USB bus state has been detected for 3 ms, the controller sets the Suspend (USBHS_DEVISR.SUSP) interrupt bit. The user may then write a one to the USBHS_CTRL.FRZCLK bit to reduce power consumption.
To recover from the Suspend mode, the user should wait for the Wakeup (USBHS_DEVISR.WAKEUP) interrupt bit, which is set when a non-idle event is detected, then write a zero to USBHS_CTRL.FRZCLK.
As the USBHS_DEVISR.WAKEUP interrupt bit is set when a non-idle event is detected, it can occur whether the controller is in the Suspend mode or not. The USBHS_DEVISR.SUSP and USBHS_DEVISR.WAKEUP interrupts are thus independent, except that one bit is cleared when the other is set.