In a Pass-Through application (KCU105), as soon as the application is executed, it checks if a Monitor is connected or not. If a monitor is already connected, then it starts up the following options as shown in the following figure to choose from (KCU105).
Selecting either r or s puts the system in Pass-Through mode, where the video received by the RX is
forwarded to the TX. This configures the vid_phy_controller
and sets up the DisplayPort for RX. If a DisplayPort Source (for example, GPU) is already
connected to DisplayPort RX Subsystem, then it starts the training. Otherwise, the training
starts when the cable is plugged in. As soon as the training is completed, the application
starts the DisplayPort TX Subsystem. The video should be seen on the monitor after the TX is
up. The previous figure shows the UART transcript. The transcript might differ based on the
training done by the GPU.