Ping-Pong Buffer with SGDMA

That's correct, if data arrives while the DMA is idle then it won't accept the new data. That said, if you are dependent on the DMA always being ready then that tells me you need some buffering in your system. Typically you would have a FIFO in the data path before the DMA so that you can handle cases like these. For example if the SGDMA and some other master were accessing the same memory, the DMA might be starved for cycles, it's internal FIFO becomes, and then it stops accepting data.