= GIET-VM / DMA Driver =

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The [source:soft/giet_vm/giet_drivers/dma_driver.c dma_driver.c] and [source:soft/giet_vm/giet_drivers/dma_driver.h dma_driver.h] files define the DMA driver. 

This ''vci_multi_dma'' component is a multi-channels DMA controller, that can replicated in all clusters (''internal'' peripheral).

There is  (NB_CLUSTERS * NB_DMA_CHANNELS) channels, indexed by a global index:
        dma_id = cluster_xy * NB_DMA_CHANNELS + local_index

A DMA channel is a private ressource allocated to a given processor. It is exclusively used by the kernet to speedup data transfers, and
there is no lock protecting exclusive access to the channel. As the kernel uses a polling policy on the DMA_STATUS register to detect
transfer completion, the DMA IRQ is not used.

The virtual base address of the segment associated to a channel is:
    SEG_DMA_BASE + cluster_xy * PERI_CLUSTER_INCREMENT + DMA_SPAN * local_index

The SEG_DMA_BASE virtual address and PERI_CLUSTER_INCREMENT values must be defined in the hard_config.h file.