The reads and writes can be routed to the FPD memory coherent interconnect for memory coherency with the FPD system cache. In descriptor mode, the memory coherency parameters for the DMA transfer are sourced from the descriptor table in memory. In the simple register DMA mode, the memory coherency parameters are sourced from APB registers.
- Register DMA
- Descriptor table, scatter-gather, SG DMA
The DMA coherent transaction routing to the FPD coherent interconnect is controlled by the LPD_INT_CSR.ROUTE_DMA register.
The memory coherency is controlled by the PS_DMA register.
Software programs the SRC and DST descriptors. Software programs registers to point to the start of these descriptors in memory, and enables the channel. Upon receiving a channel enable, the DMA channel fetches SRC and DST descriptors from memory and uses these parameters to perform the actual data transfer. It is the responsibility of the software to program descriptors before enabling a channel.