does EPCS controller support DMA

This may be irrelevant, because of hippo's throughput analysis, but if offloading the data transfer to a DMA-like component is still of interest, read on:

The Avalon DMA cannot transfer data from the epcs component, because Avalon flow control doesn't work properly on that connection. The root of the problem is the way the epcs component produces read data:

1) an avalon master writes a dummy byte to the epcs component

2) the epcs component clocks out the dummy byte, and simultaneously receives data from the epcs flash chip

3) the received byte is available to be read in the epcs component rx register.

In a simple DMA <-> epcs component connection, there is no master to write dummy bytes into the epcs component, thus no received data. It _might_ work if, say, the Nios was writing the dummy bytes into the tx register, but ... why bother using a DMA if you have to tie up the processor anyway?

I suggest writing a custom component in the HDL of your choice (for importation with component editor), which writes and reads the epcs, and delivers the received data at a flow-control-equipped slave port, for the DMA to consume. Or, your custom component could have a master port, which would write its data directly to memory.