By sending a WAKEUP signal from MCU (FPGA as well), CY7C65215 is waken up from suspend state, which in turn issues a remote wakeup to the USB host. It is mentioned in our datasheet.
Otherwise, simply monitor the CY7C65215's VBUS pin voltage and XRES (if used) so as to detect the USB connection.
If these things do not meet the customer's requirement, kindly let me know which feature of CY7C65215 will they use? UART, I2C, or SPI? Master or Slave? Self-powered or Bus-powered? Since they use CY7C65215, will they use dual channel? Do they have to detect USB connection with exact timing?