A common buffer is shared between the DMA channels to hold the AXI read transaction data before it goes out on an AXI write channel. The common buffer is sized to allow utilization of full AXI bandwidth. The size of the common buffer is 4 KB for FPD DMA and 2 KB for LPD DMA.
•Shares the full buffer space between enabled channels. When only one channel is enabled, it can use the full buffer memory space.
•Does not utilize/reserve any space in the memory if a channel is disabled (from a previous enable).
•In the event of an error, the DMA channel frees all occupied common buffer entries.
•Shared buffer on a first-come first-served basis.
•Software can limit the common buffer usage of a particular channel by programming read-issuing and rate-control registers. The design of the DMA ensures no starvation on any channel irrespective of their rate control and read issuing parameters.