Descriptor Engine - 2.0 English

Versal Adaptive SoC DMA and Bridge Subsystem for PCI Express Product Guide (PG344)

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2.0 English

The descriptor engine is responsible for managing the consumer side of the Host to Card (H2C) and Card to Host (C2H) descriptor ring buffers for each queue. The context for each queue determines how the descriptor engine will process each queue individually. When descriptors are available and other conditions are met, the descriptor engine will issue read requests to PCIe to fetch the descriptors. Received descriptors are offloaded to either the descriptor bypass out interface (bypass mode) or delivered directly to a DMA engine (internal mode). When a H2C Stream or Memory Mapped DMA engine completes a descriptor, status can be written back to the status descriptor, an interrupt, and/or a marker response can be generated to inform software and user logic of the current DMA progress. The descriptor engine also provides a Traffic Manager Interface which notifies user logic of certain status for each queue. This allows the user logic to make informed decisions if customization and optimization of DMA behavior is desired.