= GIET-VM / CMA Driver =

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

It supports the SOCLIB ''vci_chbuf_dma'' component, that is a multi channels, chained buffer DMA controller.
This component can be used in conjonction with the SOCLIB ''vci_frame_buffer'' to display images, or with the SOCLIB ''vci_multi_nic'' controller to transfer  RX or TX packets between NIC buffers and memory buffers.

The SEG_CMA_BASE address must be defined in the hard_config.h file.

The addressable registers map is defined [source:soft/giet_vm/giet_drivers/cma_driver.h here].

 === unsigned int '''_cma_get_register'''( unsigned int channel,  unsigned int index ) ===
This low_level function returns the value contained in register (index).

 === void '''_cma_set_register'''( unsigned int channel,  unsigned int index,  unsigned int value ) ===
This low_level function returns the value contained in register (index).

 === void '''_cma_start_channel'''( unsigned int       channel,
                         unsigned long long src_paddr,
                         unsigned int       src_nbufs,
                         unsigned long long dst_paddr,
                         unsigned int       dst_nbufs,
                         unsigned int       buf_length ) ===
This function activates a chained buffer DMA channel.
 * channel : CMA channel index.
 * src_paddr : physical address of the source chbuf.
 * src_nbufs : number of buffers in the source chbuf.
 * dst_paddr : physical address of the destination chbuf.
 * dst_nbufs : number of buffers in the destination chbuf.
 * buf_length : single buffer length (bytes)
 * s

 === void '''_cma_stop_channel( unsigned int channel )
This function desactivates a chained buffer DMA channel.
 * channel : CMA channel index.

 === void '''_cma_isr'''( unsigned int irq_type,  unsigned int irq_id,  unsigned int channel ) ===
This Interrupt Service Routine handles the IRQ generated by a CMA channel.