Scalable Scatter-Gather DMA Intel® FPGA IP User Guide

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ID 823097
Date 4/07/2025
Public
Document Table of Contents
Document Table of Contents x
1. Terms and Acronyms 2. Introduction 3. Functional Description 4. Interfaces 5. HAL Driver for DMA SoC Mode  6. Parameters 7. Registers 8. Document Revision History for the Scalable Scatter-Gather DMA Intel® FPGA IP User Guide
2. Introduction x
2.1. Device Family Support 2.2. Release Information 2.3. Resource Utilization
3. Functional Description x
3.1. DMA PCIe* Mode 3.2. DMA SoC Mode 3.3. Device Port 3.4. Prefetcher Engine 3.5. DMA Arbiter 3.6. DMA Router 3.7. CSRUnit 3.8. Descriptor Handling 3.9. Interrupts 3.10. Reset Initialization Flows 3.11. Transaction Flow
3.1. DMA PCIe* Mode x
3.1.1. Submodules
3.1.1. Submodules x
3.1.1.1. PCIe* TLP Constructor 3.1.1.2. PCIe* TLP ID Generation 3.1.1.3. PCIe TX Credit Controller 3.1.1.4. PCIe* TX Scheduler 3.1.1.5. PCIe TLP Completer 3.1.1.6. PCIe RX Router 3.1.1.7. PCIe* MSI-X Controller 3.1.1.8. PCIe BAR0 3.1.1.9. PCIe Bursting Manager (BAM) 3.1.1.10. Completion Timeout Parser 3.1.1.11. Control Shadow Parser
3.2. DMA SoC Mode x
3.2.1. Interrupt Controller 3.2.2. Host AXI-4 Agent 3.2.3. Host CSR AXI-4 Lite Agent
3.3. Device Port x
3.3.1. ST Source Agent/ST Sink Agent/MM Agent 3.3.2. Descriptor Engine 3.3.3. Agent Controller 3.3.4. Constructor 3.3.5. Responder 3.3.6. Width Adaptation FIFO
3.8. Descriptor Handling x
3.8.1. Link Descriptor 3.8.2. Data Descriptor 3.8.3. Responder Descriptor 3.8.4. Descriptor Chain 3.8.5. Aligned and Unaligned Transfer Support
3.8.2. Data Descriptor x
3.8.2.1. Data Descriptor - H2D Streaming Transfer 3.8.2.2. Data Descriptor - D2H Streaming Transfer 3.8.2.3. Data Descriptor - H2D Memory Transfer
3.8.3. Responder Descriptor x
3.8.3.1. Responder Descriptor - H2D Streaming Transfer 3.8.3.2. Responder Descriptor - D2H Streaming Transfer 3.8.3.3. Responder Descriptor - H2D Memory Transfer
3.8.4. Descriptor Chain x
3.8.4.1. Descriptor Fetch and Status Update Mechanism
3.11. Transaction Flow x
3.11.1. General DMA Operation Flow 3.11.2. Host to Device (H2D) Flow 3.11.3. Device to Host (D2H) Flow 3.11.4. Soft Reset Handshake Flow
4. Interfaces x
4.1. Port List 4.2. DMA PCIe* Mode Interfaces 4.3. DMA SoC Mode Interfaces 4.4. Device Port Interfaces 4.5. Resets 4.6. Clocks
4.2. DMA PCIe* Mode Interfaces x
4.2.1. Application Packet Receive Interface 4.2.2. Application Packet Transmit Interface 4.2.3. Control Shadow Interface 4.2.4. Transmit Flow Control Credit Interface 4.2.5. Completion Timeout Interface 4.2.6. PCIe* Miscellaneous Signals 4.2.7. Control and Status Register Responder Manager Interface 4.2.8. Bursting Manager Interface
4.3. DMA SoC Mode Interfaces x
4.3.1. Host AXI-4 Memory Map Manager Interface 4.3.2. Host AXI-4 Lite CSR Memory Map Subordinate Interface 4.3.3. Interrupt Interface
4.4. Device Port Interfaces x
4.4.1. Device to Host <PORT#> AXI-ST Subordinate Interface 4.4.2. Device to Host <PORT#> Avalon-ST Sink Interface 4.4.3. Host to Device <PORT#> AXI-ST Manager Interface 4.4.4. Host to Device <PORT#> Avalon-ST Source Interface 4.4.5. Host to Device <PORT#> AXI-4 Manager Interface
5. HAL Driver for DMA SoC Mode  x
5.1. Descriptor Indexing  5.2. HAL Public API 
5.1. Descriptor Indexing  x
5.1.1. Data Descriptors  5.1.2. Responders 
5.2. HAL Public API  x
5.2.1. Software Features 5.2.2. intel_ssgdma.c  5.2.3. intel_ssgdma_global.c 5.2.4. intel_ssgdma_device_port.c  5.2.5. intel_ssgdma_descriptor.c 
6. Parameters x
6.1. DMA Settings 6.2. Device Port Settings 6.3. DMA PCIe Mode Settings 6.4. DMA SoC Mode Settings 6.5. Example Design
6.2. Device Port Settings x
6.2.1. H2D MM 6.2.2. H2D ST 6.2.3. D2H ST
7. Registers x
7.1. Global CSR 7.2. MSI-X Memory Space 7.3. Device Port Control Register
1. Terms and Acronyms
2. Introduction
3. Functional Description
4. Interfaces
5. HAL Driver for DMA SoC Mode 
6. Parameters
7. Registers
8. Document Revision History for the Scalable Scatter-Gather DMA Intel® FPGA IP User Guide

5.1.1. Data Descriptors 

Data descriptors are stored in the host memory as an array. sw_idx is the index used to access the array in the driver and starts with index 0. The descriptors also contain a field called DescrIDX, which is equivalent to hw_idx. hw_idx is also used, when setting the insert pointer in the hardware. As the first hw_idx starts with 1, an offset is needed to sync them: sw_idx = hw_idx - 1. 

The driver provides a descriptor tracking index (sw_insert_hw_idx), which assists you to write to the next free descriptor. This index may be used as an input to set the hardware insert pointer. This allows you to prepare several descriptors in software, before updating the index to the hardware. 

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