Scalable Scatter-Gather DMA Intel® FPGA IP User Guide

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ID 823097
Date 1/27/2025
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

3.1.1.4. PCIe* TX Scheduler

The TX Scheduler module performs the following tasks:

  • Performs arbitration between different TLPs coming from different modules:
    • Memory read or write from TLP Constructor module:
      • H2D (host to device) Agents
      • D2H (device to host) Agents
      • Prefetcher Engine
      • MSI-X Controller
    • Memory Read Completion from BAM(BAR1) Agent
    • Memory Read Completion from BAR0 Agent
  • Reads out TLPs from internal FIFO modules based on the advertised partner's credits from TX Credit Controller. Additional to that, the TX Scheduler monitors the occupancy of reordering buffer resided in the TLP Completer apart from Non-posted credits before sending any memory read request to PCIe host. If a TLP type is blocked due to a lack of the corresponding RX buffer space from the PCIe host, other TLP types may bypass it per the PCIe transaction ordering rules.
  • Performs Packing according to the Header Packing scheme defined in the GTS AXI Streaming Intel® FPGA IP for PCI Express. The SSGDMA supports simple packing scheme where the header always start from Byte Index 0. This rule constraints only one packet can be sent per cycle.
  • Generates dummy completion TLP(for posted/MEMWR TLP) to TLP Completer which eventually routes to the agents upon transfer completion to PCIe Host. This is to ensure the agents only initiate write-back response to PCIe Host after all data are successfully transferred to Host memory.
The table below shows the mapping of the header and data for a 256-bit wide Tdata defined in the PCIe* IP.
Table 7.  Simple Packing Scheme with 256-bit Tdata Bus
Tdata [255:0]
16B 16B
Header Upper 16 bytes Header Lower 16 bytes
Data Data
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