The LS1012A RDB reference manual outlines 2 possible sources for the PCIe reference clock: PCIE_CLK and SD1_TX_CLK. In both cases, the reference clock is an *output* from the board, which means (IIUC) these configurations apply only to the case in which the PCIe is used in RC mode. In EP mode, the reference clock would be an *input*. Correct? If so, where are the relevant PCIe configurations documented? Is there no way to route an externally-provided reference clock to the LS1012A's PCIe controller?