MSI-X and Writeback block update the host with the current processed queue’s head pointer and interrupt. Apart from a global MSI-X Enable and Writeback Enable, there is a provision to selectively enable or disable the MSI-X and Writeback on a per-descriptor basis. This feature can be used by applications to throttle the MSI-X/Writeback.
|Global Enable||Per-descriptor Enable||MSI-X/Writeback Generation|
If enabled, a Writeback is sent to the host to update the status (completed descriptor ID) stored in Q_CONSUMED_HEAD_ADDR location. In addition, for D2H streaming DMA, an additional MWr TLP is issued to the D2H descriptor itself when the IP’s Avalon-ST sink interface has received an sof/eof from the user logic. It updates the D2H descriptor packet information fields such as start of a file/packet(SOF), end of a file/packet(EOF), and received payload count (RX_PYLD_CNT).
Did you find the information on this page useful?