Intel IXP400 manual DMA Initialization, IxDmaAcc Control Flow

Intel® IXP400 Software

Access-Layer Components: DMA Access Driver (IxDmaAcc) API

Upon completion of the DMA transfer, the NPE writes a message to the AQM-done queue. The AQM dispatcher then calls the ixDmaAcc callback and the access layer calls the client callback.

Figure 45 shows the overall flow of the DMA transfer operation between the client, the access layer, and the NPE.

Figure 45. IxDmaAcc Control Flow

1.ixDmaAccInit

2.ixDmaAccDmaTransfer

3. ixQMgrQWrite

4.IX_STATUS

7. ixDmaAccDoneCallback

8.Client Callback

Client Task

IxDmaAcc

IxQMgr

NPE

5.ReadReqFIFO

6.WriteDoneFIFO

The NPE is triggered by a hardware event to read a DMA transfer request descriptor.

A DMA transfer is performed and when the transfer is completed the descriptor pointer is passed on to the DMA Done Queue.

The descriptor contains the client callback function pointer that is called when the descriptor is passed back to IxDmaAcc (Steps 7 and 8)

B2359-03

8.9.1DMA Initialization

Figure 46 and the following steps describe the DMA access-layer initialization:

April 2005	IXP400 Software Version 2.0	Programmer’s Guide
124	Document Number: 252539, Revision: 007