SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
Configuration (Cfg) traffic is not symmetrical: it can only be requested by the RC, and completed (in the case of PCIe controller) by the EP. It is used by the RC for the enumeration of the fabric: EP, functions, switches.
The RC cannot use configuration traffic over the PCIe wire to access its own 4 KiB configuration space. To do that, it uses DIF accesses (CS) with bit PCIECTRL_PL_DBI_RO_WR_EN[0] CX_DBI_RO_WR_EN = 0b0.