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axi_dmac: Use AXI3 for DMAC in Intel projects
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The buffers inside the interconnect are sized based on maximum burst sizes
the masters can produce.
For AXI4 the max burst size is 128 but for these projects for the
default burst size of 128 bytes the DMACs are creating only burst of 8 or
16 beats depending on the bus width (128bits and 64 bits respectively).

These burst sizes can fit in the AXI3 protocol where the max burst
length is 16. Therefore the interconnect will be reduced.

The observed reduction is around 4 Mb of block RAM per project.
Another benefit is a better timing closure,
since these buffers reside in the DDR3 clock domain.
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ronagyl committed Aug 21, 2018
1 parent 2293374 commit cff06bd
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion library/axi_dmac/axi_dmac_hw.tcl
Original file line number Diff line number Diff line change
Expand Up @@ -91,7 +91,7 @@ foreach {suffix group} { \
{ "0:Memory-Mapped AXI" "1:Streaming AXI" "2:FIFO Interface" }
set_parameter_property DMA_TYPE_$suffix GROUP $group

add_parameter DMA_AXI_PROTOCOL_$suffix INTEGER 0
add_parameter DMA_AXI_PROTOCOL_$suffix INTEGER 1
set_parameter_property DMA_AXI_PROTOCOL_$suffix DISPLAY_NAME "AXI Protocol"
set_parameter_property DMA_AXI_PROTOCOL_$suffix HDL_PARAMETER true
set_parameter_property DMA_AXI_PROTOCOL_$suffix ALLOWED_RANGES { "0:AXI4" "1:AXI3" }
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