iob-dma

DMA for IObundle SoCs with:

• 1 AXI manager data interface (memory source/destination path)
• 1 AXI-Lite subordinate control interface (register programming and status)

This repository contains the hardware module, software driver, and integration support files for simulation/embedding flows.

Overview

iob-dma moves data from an AXI-full source address range to an AXI-full destination address range under software control. Software configures source/destination addresses, transfer length, burst length, and source/destination burst types through the control registers, then starts source-to-destination DMA operations.

Supported burst types are DMA_BURST_TYPE_FIXED (0) and DMA_BURST_TYPE_INCR (1) for both source and destination paths.

DMA Operation

• The DMA reads data from AXI source address space and writes it to AXI destination address space.
• The internal datapath connects read-side output to write-side input, so no external AXI-Stream interface is required.
• A single start triggers both source read and destination write paths.
• busy remains high while the transfer is in progress.

Example programming sequence:

dma_init(DMA_BASEADDR);
dma_start_transfer(src_addr, dst_addr, length_words, burstlen_words,
				   DMA_BURST_TYPE_INCR, DMA_BURST_TYPE_FIXED);
while (dma_busy()) {
	// wait
}

Main Interfaces

AXI manager data interface

• Used for DMA transfers between AXI-full source and destination memory regions.
• Configurable address, burst length, ID, and data width parameters.

AXI-Lite subordinate control interface

• Used by CPU/software to configure and monitor the DMA.
• Exposes control/status registers for source and destination addressing plus shared transfer control/status.

Register-Level Control

The DMA exposes source and destination address/burst-type registers, plus shared transfer control/status fields:

• Source address: src_addr
• Destination address: dst_addr
• Source transfer fields: src_addr, src_burst_type
• Destination transfer fields: dst_addr, dst_burst_type
• Shared transfer fields: length, burstlen, start, busy, buf_level
• soft_reset

Typical sequence:

1. Program src_addr and dst_addr.
2. Program length, burstlen, src_burst_type, and dst_burst_type.
3. Trigger start.
4. Poll busy until transfer completes.

Software API

Driver files are available in software/src/:

• iob-dma.h
• iob-dma.c

Exposed helper functions:

• dma_init(...): initializes the DMA base address.
• dma_start_transfer(...): starts a source-to-destination transfer.
• dma_busy(...): reports transfer progress.

void dma_init(int base_address);
void dma_start_transfer(uint32_t *src_addr, uint32_t *dst_addr,
						uint32_t length, uint32_t burstlen,
						uint32_t src_burst_type, uint32_t dst_burst_type);
uint8_t dma_busy();

Repository Structure

• iob_dma.py: DMA description and configurable parameters
• hardware/src/iob_dma.v: top-level RTL
• software/src/: C driver and software support