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Writing a Simulation Makefile

The testbench Makefile tells the build tools what to build, where to build it, dependency information, and runtime information. The build infrastructure will handle the how-to part for each supported simulation tool.

An example makefile for a testbench is shown below. If creating a testbench for RFNoC, it is recommended to use the RFNoC ModTool to generate a Makefile template for your RFNoC block.

    #
    # Copyright 2020 Ettus Research, a National Instruments Brand
    #
    # SPDX-License-Identifier: LGPL-3.0-or-later
    #

    #-------------------------------------------------
    # Top-of-Makefile
    #-------------------------------------------------
    # Define BASE_DIR to point to the "top" dir. Note:
    # UHD_FPGA_DIR must be passed into this Makefile.
    ifndef UHD_FPGA_DIR
    $(error "UHD_FPGA_DIR is not set! Must point to UHD FPGA repository!")
    endif
    BASE_DIR = $(UHD_FPGA_DIR)/usrp3/top
    # Include viv_sim_preamble after defining BASE_DIR
    include $(BASE_DIR)/../tools/make/viv_sim_preamble.mak

    #-------------------------------------------------
    # Design Specific
    #-------------------------------------------------
    # Define part using PART_ID (<device>/<package>/<speedgrade>)
    ARCH = kintex7
    PART_ID = xc7k410t/ffg900/-2

    # Include makefiles and sources for the DUT and its dependencies
    include $(BASE_DIR)/../lib/rfnoc/core/Makefile.srcs
    include $(BASE_DIR)/../lib/rfnoc/utils/Makefile.srcs
    include $(BASE_DIR)/../lib/fifo/Makefile.srcs
    include $(BASE_DIR)/../lib/axi/Makefile.srcs
    include $(BASE_DIR)/../lib/control/Makefile.srcs

    DESIGN_SRCS += $(abspath \
    $(RFNOC_CORE_SRCS) \
    $(RFNOC_UTIL_SRCS) \
    $(RFNOC_OOT_SRCS) \
    $(FIFO_SRCS) \
    $(AXI_SRCS) \
    $(CONTROL_LIB_SRCS) \
    )

    #-------------------------------------------------
    # IP Specific
    #-------------------------------------------------
    # If simulation contains IP, define the IP_DIR and point
    # it to the base level IP directory
    IP_DIR = $(BASE_DIR)/x300/ip
    LIB_IP_DIR = $(BASE_DIR)/../lib/ip

    # Include makefiles and sources for all IP components
    # *after* defining the IP_DIR
    include $(IP_DIR)/fifo_4k_2clk/Makefile.inc
    include $(LIB_IP_DIR)/axi_fft/Makefile.inc

    DESIGN_SRCS += $(abspath \
    $(IP_FIFO_4K_2CLK_SRCS) \
    $(LIB_IP_AXI_FFT_SRCS) \
    rfnoc_block_example.v \
    )

    #-------------------------------------------------
    # Testbench Specific
    #-------------------------------------------------
    include $(BASE_DIR)/../sim/general/Makefile.srcs
    include $(BASE_DIR)/../sim/axi/Makefile.srcs

    # Define only one top-level module
    SIM_TOP = rfnoc_block_example_tb

    # Simulation runtime in microseconds
    SIM_RUNTIME_US = 1000

    SIM_SRCS = \
    $(abspath rfnoc_block_example_tb.sv) \

    #-------------------------------------------------
    # Bottom-of-Makefile
    #-------------------------------------------------
    # Include all simulator specific makefiles here
    # Each should define a unique target to simulate
    # e.g. xsim, vsim, etc and a common "clean" target
    include $(BASE_DIR)/../tools/make/viv_simulator.mak

You will notice that the Makefile has 5 distinct sections.

# Section 1: Boilerplate

    #-------------------------------------------------
    # Top-of-Makefile
    #-------------------------------------------------
    # Define BASE_DIR to point to the "top" dir. Note:
    # UHD_FPGA_DIR must be passed into this Makefile.
    ifndef UHD_FPGA_DIR
    $(error "UHD_FPGA_DIR is not set! Must point to UHD FPGA repository!")
    endif
    BASE_DIR = $(UHD_FPGA_DIR)/usrp3/top
    # Include viv_sim_preamble after defining BASE_DIR
    include $(BASE_DIR)/../tools/make/viv_sim_preamble.mak

Before declaring any variables or using any recipes, the following must be performed (in order):

- Define BASE_DIR to tell the build system where the <repo>/fpga/usrp3/top directory is relative to the current testbench directory
- Include viv_sim_preamble.mak to initialize boilerplate variables and functions

This example uses the make variable UHD_FPGA_DIR to specify the location of the FPGA repository. This is useful for out-of-tree modules. UHD_FPGA_DIR is the variable used by CMake for the RFNoC examples.

# Section 2: Design Specific

    #-------------------------------------------------
    # Design Specific
    #-------------------------------------------------
    # Define part using PART_ID (<device>/<package>/<speedgrade>)
    ARCH = kintex7
    PART_ID = xc7k410t/ffg900/-2

    # Include makefiles and sources for the DUT and its dependencies
    include $(BASE_DIR)/../lib/rfnoc/core/Makefile.srcs
    include $(BASE_DIR)/../lib/rfnoc/utils/Makefile.srcs
    include $(BASE_DIR)/../lib/fifo/Makefile.srcs
    include $(BASE_DIR)/../lib/axi/Makefile.srcs
    include $(BASE_DIR)/../lib/control/Makefile.srcs

    DESIGN_SRCS += $(abspath \
    $(RFNOC_CORE_SRCS) \
    $(RFNOC_UTIL_SRCS) \
    $(RFNOC_OOT_SRCS) \
    $(FIFO_SRCS) \
    $(AXI_SRCS) \
    $(CONTROL_LIB_SRCS) \
    )

This section contains pointers to sources and other variables needed for the DUT to function. In the example above, we are including all sources from the lib/fifo, lib/axi, lib/control directories. These may not be needed for your simulation, in which case they can be removed to reduce compile times.

The following makefile variables are special and should be defined:

- ARCH: The architecture targeted for the simulation.
- PART_ID: The exact part targeted for the simulation. Format: <device>/<package>/<speedgrade>
- DESIGN_SRCS: Space-separated paths to the DUT and all of its dependencies.

If ARCH and PART_ID are not specified, a default part will be assumed. This may be fine if your DUT doesn't have any architecture-specific IP.

# Section 3: IP Specific

    #-------------------------------------------------
    # IP Specific
    #-------------------------------------------------
    # If simulation contains IP, define the IP_DIR and point
    # it to the base level IP directory
    IP_DIR = $(BASE_DIR)/x300/ip
    LIB_IP_DIR = $(BASE_DIR)/../lib/ip

    # Include makefiles and sources for all IP components
    # *after* defining the IP_DIR
    include $(IP_DIR)/fifo_4k_2clk/Makefile.inc
    include $(LIB_IP_DIR)/axi_fft/Makefile.inc

    DESIGN_SRCS += $(abspath \
    $(IP_FIFO_4K_2CLK_SRCS) \
    $(LIB_IP_AXI_FFT_SRCS) \
    rfnoc_block_example.v \
    )

If the DUT depends on any Xilinx IP then this section is required. It tells the tools which IP cores need to be built in order to run the simulation. The IP specific Makefile include statements handle the "how" part of building IP. As long as the correct Makefile is included and the IP XCI sources are added to DESIGN_SRCS, the IP intermediates will be built correctly.

The IP_DIR variable shown here is defined to point to the base IP directory that contains target-specific IP sources. The IP_LIB_DIR variable shown here is defined to point to the base IP directory that contains target-independent IP sources.

The IP included in this example may not be needed for your testbench, in which case it can be removed to reduce compile times.

# Section 4: Testbench Specific

    #-------------------------------------------------
    # Testbench Specific
    #-------------------------------------------------
    include $(BASE_DIR)/../sim/general/Makefile.srcs
    include $(BASE_DIR)/../sim/axi/Makefile.srcs

    # Define only one top-level module
    SIM_TOP = rfnoc_block_example_tb

    # Simulation runtime in microseconds
    SIM_RUNTIME_US = 1000

    SIM_SRCS = \
    $(abspath rfnoc_block_example_tb.sv) \

This section contains all sources and parameters for the actual testbench. Any simulation dependency makefiles can be included here.

The following variables should be defined:

- SIM_TOP: The top-level module name for the simulation.
- SIM_RUNTIME_US: The maximum runtime of the simulation in microseconds. At this time $finish will be called to terminate the testbench.
- SIM_SRCS: This is similar to DESIGN_SRCS except that it should contain a path to SIM_TOP and all of its dependencies.

# Section 5: Tool Support

    #-------------------------------------------------
    # Bottom-of-Makefile
    #-------------------------------------------------
    # Include all simulator specific makefiles here
    # Each should define a unique target to simulate
    # e.g. xsim, vsim, etc and a common "clean" target
    include $(BASE_DIR)/../tools/make/viv_simulator.mak

Now that the Makefile knows all the basic information about the testbench, include tool-specific makefiles to implement simulation targets. Currently the following simulator makefiles exits:

- <repo>/fpga/tools/make/viv_simulator.mak
  This makefile supports both Vivado and ModelSim simulators.