IPC vs EDMA3

DP,

A rather lengthy explanation:

IPC (InterProcessor Communication) is a rather overused term. In general, it refers to synchronization/messaging between processors or even tasks.  On Keystone devices (and earlier TI processors) there are also “IPC” registers, which provide a rudimentary core-to-core interrupt capability.

EDMA3 is a normal (though very flexible) DMA, which can be used for simple messaging schemes by using its Transfer Completion interrupts.  So in this respect, EDMA3 can be used as an IPC module.

Multicore Navigator is a combination of a hardware Queue Manager Subsystem (a Queue Manager plus several dedicated firmware processors and other auxiliary pieces) plus a number of pktDMAs (Packet DMA) that are distributed around the device. The number of pktDMAs varies from device to device, but in Appleton (TCI6614) there are pktDMAs in these IP:

AIF

BCP

FFTC (x2)

NetCP

QMSS (infrastructure – a memory to memory pktDMA)

SRIO

There are several ways that Navigator can be used as an IPC module:

Synchronization:

-          Queues can be polled, by multiple “slaves” if necessary.

-          Special queues can trigger CP-INTC interrupts.

-          QMSS INTD can be used independently to trigger interrupts.

Messaging:

-          QM by itself can be used for zero-copy or shared memory messages.

-          QM with Infrastructure pktDMA for point-to-point messages. Rx queues can be polled or interrupt driven.

-          QM with Infrastructure pktDMA and Accumulator.  Accumulator firmware performs Rx queue management in the background with interrupts to host.

So it is much more flexible than the IPC registers and EDMA3 combined.

Differences between EDMA3 and pktDMA:

EDMA3 is slightly faster.

pktDMA is more flexible.

pktDMA is unconcerned with data format or stride. It simply moves chunks of data.

pktDMA (and QM) handle atomicity issues.

pktDMA is easier to program and use, though it requires more initial setup than EDMA3.

There is a wider variety of ways to respond to pktDMA outputs (descriptors written to Rx queues).

pktDMA transfers can be chained from one to another.

DP,

Good point. My answer was not to the point of your question on the C665x. My apologies.

The C6657 uses a different EMAC module which does not include the same pktDMA capability, nor the NetCP. It does have its own DMA capability, but it is implemented differently from the other Keystone devices. The EMAC User's Guide from the TMS320C6657 Product Folder has the details on this.

The C6657's EMAC does not go through the EDMA3 module for data transfers. It has its own built-in DMA capability which has some similarities with the pktDMA.

Regards,
RandyP