Visible to Intel only — GUID: unf1589939745702
Ixiasoft
Visible to Intel only — GUID: unf1589939745702
Ixiasoft
3.1.3.2. MSI-X/Writeback
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 |
---|---|---|
1 | 1 | On |
1 | 0 | Off |
0 | 1 | Off |
0 | 0 | Off |
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).