GIET_VM / MWR Driver

The mwr_driver.c​ and mwr_driver.h​ files define the MWR driver for the vci_mwmr_dma peripheral.

The vci_mwmr_dma component is a multi-channels DMA controller that can be used to connect an hardware coprocesseur to a VCI interconnect. This component provides the coprocessor one or several TO_COPROC or FROM_COPROC communication channels, without address. Each T0_COPROC/FROM_COPROC port contains an hardware FIFO interface (DATA, R_WOK, W_ROK signals), plus three signals (REQ, ACK, BURSTS) allowing the coprocessor to request an integer number of data burst. Each burst contains a fixed number of 32 bits words. For each coprocessor type, the burst length is an hardware parameter.

These communication channels implement two running modes:

• in MWMR mode (Multi-Writer / Multi-Reader), the channel FSM transfer an infinite data stream between the coprocessor and a MWMR software FIFO, implementing the 7 steps MWMR protocol.
• in DMA mode the channel FSM transfer data between the coprocessor and a fixed size memory buffer, with an optional interrupt signaling completion.

The vci_mwmr_dma component is an internal peripheral, that can be replicated in all clusters. Each cluster can contain at most one coprocessor.

For the vci_mwmr_dma component, the addressable registers map and the command codes are defined here​.

Besides these communication channels registers, the vci_mwmr_dma componentt supports up to 16 coprocessor specific configuration/status registers. Configuration registers are Read/Write?. Status registers are Read-Only.

Coprocessor registers access functions

These functions can be used to access the coprocessor specific registers.

void _mwr_set_coproc_register( unsigned int cluster_xy , unsigned int index , unsigned int value )

This function set a a new value in a coprocessor register.

• cluster_xy : cluster coordinates.
• index : register index.
• value : value to be written.

unsigned int _mwr_get coproc_register( unsigned int cluster_xy , unsigned int index)

• cluster_xy : cluster coordinates.

• index : register index.

Channel registers access functions

These functions access the communication channels registers contained in the vci_mwmr_dma controller.

void _mwr_set_channel_register( unsigned int cluster_xy , unsigned int channel , unsigned int index , unsigned int value )

This function set a a new value in a coprocessor register.

• cluster_xy : cluster coordinates.
• channel: channel index.
• index : register index.
• value : value to be written.

unsigned int _mwr_get channel_register( unsigned int cluster_xy , unsigned int channel, unsigned int index)

• cluster_xy : cluster coordinates.
• channel: channel index.
• index : register index.

Interrupt Service Routine

void _mwr_isr( unsigned int irq_type, unsigned int irq_id, unsigned int channel )

This Interrupt Service Routine handles the IRQ signaling the completion of a data transfer for a channel running in DMA_IRQ mode). It set the _dma_done[x][y] synchronisation variable.