The host controller interfaces to the system bus using the AXI interfaces.
AXI Interface for Programmed I/O
The AXI programming interface provides software with access to the read/write memory mapped registers for control and status. It also provides port accesses for programmed I/O commands, reads, and writes. All accesses are single 32-bit read/write transactions.
AXI Master Interface for DMA Transfers
The 32-bit AXI master is used by the SDMA for simple programmed I/O access and the ADMA for autonomous read and write memory transactions using descriptor tables with scatter-gather capabilities.