Multi Channel DMA Intel® FPGA IP for PCI Express User Guide

ID 683821
Date 11/01/2022
Public
Document Table of Contents

8.4.2.3. Descriptor Memory Management

As a part of channel initialization, the driver allocates the memory for descriptors and associates to the channel. Driver uses dma_alloc_coherent API of Linux DMA framework to allocate non-swapable and physically contagious memory.

  • By default, currently 1 page is enabled. 1 page contains 128 descriptors. By using ethtool, netdev supports changing the queue size.
  • Each queue (H2D & D2H) of each channel gets its descriptor memory.
  • After allocation of this memory, the hardware is notified of it by a write of the starting address to the QCSR region.

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