5.9. Advanced Usage
5.9.1. Alternative RTL Flows
The Make-based build system provided supports using Hammer without using RTL generated by Chipyard. To push a custom Verilog module through, one only needs to append the following environment variables to the
make buildfile command (or edit them directly in the Makefile).
CUSTOM_VLOG=<your Verilog files> VLSI_TOP=<your top module>
CUSTOM_VLOG breaks the dependency on the rest of the Chipyard infrastructure and does not start any Chisel/FIRRTL elaboration.
VLSI_TOP selects the top module from your custom Verilog files.
5.9.2. Under the Hood
To uncover what is happening under the hood, here are the commands that are executed:
./example-vlsi -e /path/to/env.yml -p /path/to/example.yml -p /path/to/inputs.yml --obj_dir /path/to/build syn
example-vlsi is the entry script as explained before,
-e provides the environment yml,
-p points to configuration yml/jsons,
--obj_dir speficies the destination directory, and
syn is the action.
./example-vlsi -e /path/to/env.yml -p /path/to/syn-output-full.json -o /path/to/par-input.json --obj_dir /path/to/build syn-to-par ./example-vlsi -e /path/to/env.yml -p /path/to/par-input.json --obj_dir /path/to/build par
syn-to-par action translates the synthesis output configuration into an input configuration given by
-o. Then, this is passed to the
For more information about all the options that can be passed to the Hammer command-line driver, please see the Hammer documentation.
5.9.3. Manual Step Execution & Dependency Tracking
It is invariably necessary to debug certain steps of the flow, e.g. if the power strap settings need to be updated. The underlying Hammer commands support options such as
--only_step. These allow you to control which steps of a particular action are executed.
Make’s dependency tracking can sometimes result in re-starting the entire flow when the user only wants to re-run a certain action. Hammer’s build system has “redo” targets such as
redo-par to run certain actions without typing out the entire Hammer command.
Say you need to update some power straps settings in
example.yml and want to try out the new settings:
make redo-par HAMMER_REDO_ARGS='-p example.yml --only_step power_straps'
5.9.4. Hierarchical RTL/Gate-level Simulation, Power Estimation
With the Synopsys plugin, hierarchical RTL and gate-level simulation is supported using VCS at the chip-level. Also, post-par power estimation with Voltus in the Cadence plugin is also supported. Special Make targets are provided in the
vlsi/ directory in
power.mk. Here is a brief description:
sim-rtl: RTL-level simulation
sim-rtl-debug: Also write a VPD waveform
sim-syn: Post-synthesis gate-level simulation
sim-syn-debug: Also write a VPD waveform
sim-syn-timing-debug: Timing-annotated with VPD waveform
sim-par: Post-par gate-level simulation
sim-par-debug: Also write a VPD waveform
sim-par-timing-debug: Timing-annotated with VPD waveform
power-par: Post-par power estimation
Note: this will run
redo-can be appended to all above targets to break dependency tracking, like described above.
-$(VLSI_TOP)suffixes denote simulations/power analysis on a submodule in a hierarchical flow. Note that you must provide the testbenches for these modules since the default testbench only simulates a Chipyard-based
The simulation configuration (e.g. binaries) can be edited for your design. See the
Makefile and refer to Hammer’s documentation for how to set up simulation parameters for your design.