SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The bulk of PCIe traffic is expected to take place in the memory (MEM) space, making use of large TLP/large L3_MAIN interface bursts.
Before PCI activity starts, one or several BAR of each device (EP function or RC) shall be initialized in Memory mode, as described in the Section 24.9.4.9.3, Base Address Registers (BAR) Initialization.
The following fields shall be set, using (CS) access (they are RO over PCI) :
The BAR shall be enabled, using (CS2) access to BARn[0]:
As part of the standard enumeration process, the RC then maps all the Memory BARs it finds (while discovering the connected EP functions) into the memory address space (32 or 64-bit address), using Cfg accesses over the PCIe wire. Optionally, the RC can also configure its own two BAR, over the DIF interface.
Once that process is complete, memory requests can take place point-to-point, that means that the requests can be initiated by any device (EP or RC) towards any other device function.