# FPGA Hardware Acceleration over PCIe

## What This Is

Multi-threaded Linux application + custom kernel driver + FPGA hardware design that accelerates Sobel edge detection on images. Demonstrates full-stack embedded systems engineering from RTL to application layer.

![System Overview][system_overview]

## Project Summary
This project implements a **full-stack hardware acceleration platform** that offloads compute-intensive image processing tasks from a multi-threaded Linux application to custom FPGA accelerators connected via PCIe. The system demonstrates advanced concepts in **computer architecture, hardware-software co-design, parallel processing, and driver development**.

### Key Achievement
Successfully designed and implemented a multi-acceleration-group architecture supporting **concurrent hardware acceleration** for up to **16 simultaneous threads**, with intelligent resource scheduling and DMA-based data transfers.

- **See [Engineering Challenges Solved](#engineering-challenges-solved)**

## Technical Overview

**Hardware (Xilinx Virtex-7 FPGA)**
- 7 parallel acceleration units supporting up to 16 concurrent threads
- Custom IP cores designed in C/C++ (Vivado HLS), synthesized to RTL
- PCIe Gen2 x4 interface with DMA engines for high-throughput data transfer
- Sobel filter accelerator processing up to 1080p images

**Software (Linux)**
- **Kernel driver**: PCIe device management, MSI interrupts, multi-thread resource scheduling
- **User application**: pthreads, memory-mapped I/O, DMA buffer management
- **MicroBlaze firmware**:  FPGA system initialization

---
## Architecture Highlights

```
┌─────────────────────────────────────────┐
│  Multi-threaded Application (pthreads)  │
└──────────────┬──────────────────────────┘
               │ ioctl(), mmap()
┌──────────────▼──────────────────────────┐
│  Kernel Driver (Resource Scheduler)     │  ← Thread arbitration, DMA setup
└──────────────┬──────────────────────────┘
               │ PCIe, MSI Interrupts
┌──────────────▼──────────────────────────┐
│  FPGA Hardware (7 Accel Groups)         │  ← Parallel processing
│  • Fetch/Send Schedulers (DMA)          │
│  • Sobel Filter Accelerators            │
│  • Interrupt Manager                    │
└─────────────────────────────────────────┘
```

**Why 7 acceleration groups?** 
- 2 Direct-mode (PCIe → BRAM, low latency)
- 4 Indirect-mode (PCIe → DDR3, higher throughput)  
- 1 Scatter-Gather (supports fragmented user memory)

Each can process different images simultaneously with driver-managed scheduling.

---

## Engineering Challenges Solved

**1. Multi-thread resource arbitration**  
16 threads competing for 7 hardware units → Implemented two scheduling policies (greedy, best-available) in kernel driver with per-thread state tracking

**2. PCIe interrupt routing**  
Designed custom Interrupt Manager IP to map 7 accelerators to MSI vectors, coordinated with GPIO-triggered interrupts

**3. Zero-copy DMA from userspace**  
Used `get_user_pages()` + scatter-gather tables for direct DMA to/from application buffers without memcpy overhead

**4. Hardware-software timing correlation**  
FPGA global timer accessible via memory-mapped registers for nanosecond-precision performance analysis

---

## Results

- **Throughput**: Supports 16 concurrent requests with linear scaling up to 7 threads
- **Latency**: ~50-100 μs for VGA images (640x480)

---

## Quick Start

```bash
# Generate custom IPs (one-time)
cd Hardware/Vivado_HLS_IPs/Sobel_Filter && vivado_hls run_hls.tcl
# ...  repeat for 8 other IPs

# Build bitstream
cd Hardware && vivado -source create_project.tcl
# Flow → Generate Bitstream

# Load driver & run
cd Software/Linux_App_Driver
make
./make_device
insmod xilinx_pci_driver.ko
./ui image. bmp 100 16 1 10  # 100 iterations, 16 threads
```

---

## Repository Structure

```
Hardware/Vivado_HLS_IPs/      9 custom IP cores (C++ → RTL)
Hardware/Vivado_Block_Design/ System integration (AXI, PCIe, DDR3)
Software/Linux_App_Driver/    Kernel driver + test application  
Software/Microblaze_XSDK/     FPGA firmware
```

[system_overview]: /Images/system_overview.png "System Overview Diagram"