Where is define of PCIe LTSSM state?

Hi

I used orin for PCIe EP mode, a x86 PC as RP. current promble is link failed.

I read PCIe register PCIE_RP_APPL_LINK_STATUS_0 is 0x00000020

PCIE_RP_APPL_DEBUG_0 sametimes is 0x00002000 and sametimes is 0x00002008. I want see LTSSM state define in PCIE_RP_APPL_DEBUG_0 register. It say Encoding is defined in databook,but where is the databook.