Jetson AGX Xavier PCIe endpoint using I/F C4

I am working on Xavier to Xavier Endpoint connection with my custom carrier board. In the reference guide, there is an example for connecting both Xaviers with PCIe I/F C5. However, in my case, I used C5 for connecting other device. Instead I connect both Xaviers with PCIe I/F C4. I add pcie_ep@14160000 in DT but still can’t get it working. One question on the hardware side is that, which PIN PEX_CLK4_N/P should be connected to? There is no clear reference on this. Is it UPHY_REFCLK1_N/P or NVHS0_SLVS_REFCLK_N/P?