05-bottom_up_rtl_kernel

Vitis™ Application Acceleration Development Flow Tutorials

Bottom-up RTL Kernel Flow with Vitis for Acceleration

Version: Vitis 2023.1

Register transfer level (RTL) design is a traditional and important hardware accelerator development methodology for FPGA. RTL modules provide excellent flexibility and efficiency, while the design process is a time consuming and error-prone process. The Vitis unified software platform provides a mature and proven RTL kernel design methodology. With Vitis and the included the AMD Vivado™ Design Suite, you can focus on your core accelerating module, instead of spending a lot of time on integration, host-field programmable gate array (FPGA) communication, direct memory access (DMA), and other supporting tasks.

About This Tutorial

This tutorial introduces a bottom-up Vitis-based RTL kernel construct and wrap-up process, as well as the host-kernel interaction with the Xilinx Runtime library (XRT). All the steps in this tutorial use the command line interface, except those needed to view waveform or system diagram.

This tutorial uses an example design to illustrate the relevant concept and steps. The following image shows the block diagram of this design. It is a simple advanced encryption standard (AES) accelerator design and comprises two kernels, krnl_aes and krnl_cbc. The krnl_aes kernel is the core AES computation core with AXI streams slave and master ports. The krnl_cbc kernel handles the host-kernel data exchange, and the implementation of AES-ECB and AES-CBD modes along with the krnl_aes module.

The AMD Alveo™ Data Center accelerator cards are the target platform for this tutorial, which describes the following tasks:

• Packing RTL design to Vitis-compliant RTL kernel with the command line interface
• Using mixed-mode clock manager (MMCM)/ phase-locked loop (PLL) in the RTL kernel
• Using the Vivado XSIM to simulate the design
• Using AMD AXI VIP to verify the RTL design with AXI interface
• Using three RTL kernel control modes with XRT: ap_ctrl_none, ap_ctrl_hs, and ap_ctrl_chain.
• Host programming for the RTL kernel with the XRT Native API
• Using Vitis hardware emulation to get an insight look of the RTL kernel operation

NOTE: This is not a detailed tools usage guideline, so only basic ideas and steps are shown. You will need to refer to other documents for details.

Device and Software Requirements

The designs have been verified with the following software/hardware environment and tool chain versions:

• Operating Systems:
  • Redhat/CentOS 7 (See Additional Requiements for RedHat/CentOS)
  • Ubuntu 18.04/20.04 (See Additional Requiements for Ubuntu)
  • Perl package installed for Verilog simulation (required)
  • OpenSSL library installed for hardware output validate (required)
  • GCC 7
• Vitis: 2023.1
• Hardware and Platform for your Alveo card (you need both the deployment and development platforms):
  • Alveo U200: xilinx_u200_gen3x16_xdma_2_202110_1
  • Alveo U250: xilinx_u250_gen3x16_xdma_4_1_202210_1
  • Alveo U50: xilinx_u50_gen3x16_xdma_5_202210_1
  • Alveo U55C: xilinx_u55c_gen3x16_xdma_3_202210_1
  • Alveo U280: xilinx_u280_gen3x16_xdma_1_202211_1

Additional Requirements for RedHat/CentOS

If you are using RedHat/CentOS 7, the default installed GNU compiler collection (GCC) version is 4.x.x. You must use the following command to install and switch to GCC 7 before compiling the host program.

sudo yum install centos-release-scl
sudo yum install devtoolset-7-gcc-c++
scl enable devtoolset-7 bash

To install the OpenSSL library for CentOS/Redhat, use:

sudo yum install openssl-devel

Additional Requirements for Ubuntu

To install the OpenSSL library for Ubuntu, use:

sudo apt install libssl-dev

Tutorial Contents

This tutorial is separated into three parts and are intended to be used in order.

1. AES Introduction and Core AES Computing RTL Module

   This part gives a brief introduction to AES algorithm and the core RTL module for AES acceleration. The RTL AES module uses native Verilog interface. A simple Verilog testbench is provided to verify the function of the RTL module.

2. Creating and Packing Vitis Compatible RTL Kernel krnl_aes

   This part packs the RTL module described in the first part into a Vitis kernel called krnl_aes, which can be integrated into Vitis. The krnl_aes kernel has four internal AES pipelines and includes AXI control slave and AXI stream master/slave ports.

   The krn_aes kernel has a mix control model of ap_ctrl_none and ap_ctrl_hs. An MMCM IP is used in this kernel to generate required core clock, while the AXI interface uses the standard platform clock. A simple Verilog testbench with Xilinx AXI VIPs are provided to verify the function of the kernel.

   In this part, you also integrate the krnl_aes kernel with a few HLS kernels to generate a usable XCLBIN file. A host test program with XRT native API is used to test the function of the krnl_aes kernel.

3. Creating and Packing Vitis Compatible RTL Kernel krnl_cbc

This part introduces a new RTL kernel called krnl_cbc, which has AXI master interfaces as well as AXI-Stream interfaces. This kernel will be connected with the krnl_aes kernel to implement the AES-ECB and AES-CBC mode encryption/decryption functions.

The krnl_cbc kernel supports ap_ctrl_chain control models. You can study and compare the behavior and performance differences between ap_ctrl_chain and ap_ctrl_hs model using the provided AXI VIP-based testbench, hardware emulation, and host program.

The directory structure and brief explanations of the design repository are as follows.

├── aes                                         # Directory for first part: aes
│   ├── rtl/                                    #   Verilog sources
│   ├── tbench/                                 #   Verilog/SystemVerilog testbench files
│   ├── filelist_aes.f                          #   file list file for xsim simulation
│   ├── Makefile                                #   Makefile for all operation
│   ├── runsim_aes_xsim.sh                      #   shell script to run the simulation with xsim
│   └── xsim.tcl                                #   xsim tcl script for simulation
│
├── common                                      # common resources
│   └── plain_gen.pl                                # Perl script to generate input data for RTL simulation
│
├── doc                                         # documents
│
├── krnl_aes                                    # Directory for second part: krnl_aes
│   ├── hls                                     #   HLS sources
│   ├── host/                                   #   Host test program    
│   ├── rtl/                                    #   Verilog sources
│   ├── tbench/                                 #   Verilog/SystemVerilog testbench files
│   ├── filelist_krnl_cbc.f                     #   xsim simulation command file
│   ├── gen_ip.tcl                              #   Vivado tcl script to generate required IPs
│   ├── krnl_aes_test.cfg                       #   Vitis v++ link config file
│   ├── krnl_aes.xdc                            #   constraint for kernel krnl_aes
│   ├── Makefile                                #   Makefile for all operation
│   ├── pack_kernel.tcl                         #   Vivado tcl script to pack the kernel
│   ├── runsim_krnl_aes_xsim.sh                 #   shell script to run the simulation with xsim   
│   ├── setup_emu.sh                            #   shell script to enable/disable hw_emu emulation mode
│   └── xrt.ini                                 #   XRT config file for emulation/profiling
│
├── krnl_cbc                                    # Directory for third pard: krnl_cbc
│   ├── host/                                   #   Host test program  
│   ├── rtl/                                    #   Verilog sources
│   ├── tbench/                                 #   Verilog/SystemVerilog testbench files
│   ├── filelist_krnl_cbc.f                     #   xsim simulation command file
│   ├── gen_ip.tcl                              #   Vivado tcl script to generate required IPs
│   ├── krnl_cbc_test.cfg                       #   Vitis v++ link config file
│   ├── Makefile                                #   Makefile for all operation
│   ├── pack_kernel.tcl                         #   Vivado tcl script to pack the kernel
│   ├── runsim_krnl_cbc_xsim.sh                 #   shell script to run the simulation with xsim   
│   ├── setup_emu.sh                            #   shell script to enable/disable hw_emu emulation mode
│   ├── xrt.ini                                 #   XRT config file for emulation/profiling
│   └── xsim.tcl                                #   xsim tcl script to set hw_emu simulation options
│
└── README.md

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