VeeR EL2 RISC-V Core

This repository contains the VeeR EL2 RISC-V Core design RTL.

License

By contributing to this project, you agree that your contribution is governed by Apache-2.0.
Files under the tools directory may be available under a different license. Please review individual files for details.

Directory Structure

├── configs                 # Configurations Dir
│   └── snapshots           # Where generated configuration files are created
├── design                  # Design root dir
│   ├── dbg                 #   Debugger
│   ├── dec                 #   Decode, Registers and Exceptions
│   ├── dmi                 #   DMI block
│   ├── exu                 #   EXU (ALU/MUL/DIV)
│   ├── ifu                 #   Fetch & Branch Prediction
│   ├── include             
│   ├── lib
│   └── lsu                 #   Load/Store
├── docs
├── tools                   # Scripts/Makefiles
└── testbench               # (Very) simple testbench
    ├── asm                 #   Example assembly files
    ├── hex                 #   Canned demo hex files
    └── tests               #   Example tests

Dependencies

• Verilator (4.106 or later) must be installed on the system if running with Verilator
• If adding/removing instructions, espresso must be installed (used by tools/coredecode). Remember to checkout on 3.x branch.
• RISCV tool chain (based on gcc version 8.3 or higher) must be installed so that it can be used to prepare RISCV binaries to run.

Quickstart guide

1. Clone the repository, clone submodules with git submodule update --init --recursive
2. Setup RV_ROOT to point to the path in your local filesystem
3. Determine your configuration (optional)
4. Run make with tools/Makefile

Release Notes for this version

Please see release notes for changes and bug fixes in this version of VeeR.

Configurations

VeeR can be configured by running the $RV_ROOT/configs/veer.config script:

% $RV_ROOT/configs/veer.config -h for detailed help options

For example to build with a DCCM of size 64 Kb:

% $RV_ROOT/configs/veer.config -dccm_size=64

This will update the default snapshot in ./snapshots/default/ with parameters for a 64K DCCM.

Add -snapshot=dccm64, for example, if you wish to name your build snapshot dccm64 and refer to it during the build.

There are 4 predefined target configurations: default, default_ahb, typical_pd and high_perf that can be selected via the -target=name option to veer.config. Note: that the typical_pd target is what we base our published PPA numbers. It does not include an ICCM.

Building an FPGA speed optimized model: Use -fpga_optimize=1 option to veer.config to build a model that removes clock gating logic from flop model so that the FPGA builds can run at higher speeds. This is now the default option for targets other than typical_pd.

Building a Power optimized model (ASIC flows): Use -fpga_optimize=0 option to veer.config to build a model that enables clock gating logic into the flop model so that the ASIC flows get a better power footprint. This is now the default option for targettypical_pd.

This script derives the following consistent set of include files:

./snapshots/default
├── common_defines.vh                       # `defines for testbench or design
├── defines.h                               # #defines for C/assembly headers
├── el2_param.vh                            # Design parameters
├── el2_pdef.vh                             # Parameter structure
├── pd_defines.vh                           # `defines for physical design
├── perl_configs.pl                         # Perl %configs hash for scripting
├── pic_map_auto.h                          # PIC memory map based on configure size
└── whisper.json                            # JSON file for veer-iss
└── link.ld                                 # default linker control file

Building a model

While in a work directory:

1. Set the RV_ROOT environment variable to the root of the VeeR directory structure.

   Example for bash shell: export RV_ROOT=/path/to/veer Example for csh or its derivatives: setenv RV_ROOT /path/to/veer

2. Create your specific configuration

   (Skip if default is sufficient)
   (Name your snapshot to distinguish it from the default. Without an explicit name, it will update/override the default snapshot)

   For example if mybuild is the name for the snapshot:

   $RV_ROOT/configs/veer.config [configuration options..] -snapshot=mybuild

   Snapshots are placed in the ./snapshots directory

3. Run a simple Hello World program (Verilator)

   make -f $RV_ROOT/tools/Makefile

This command will build a Verilator model of VeeR EL2 with the AXI bus, and execute a short sequence of instructions that writes out "HELLO WORLD" to the bus.

The simulation produces output on the screen like:

VerilatorTB: Start of sim

-------------------------
Hello World from VeeR EL2
-------------------------
TEST_PASSED

Finished : minstret = 437, mcycle = 922
See "exec.log" for execution trace with register updates..

The simulation generates the following files:

• console.log contains what the cpu writes to the console address of 0xd0580000.
• exec.log shows instruction trace with GPR updates.
• trace_port.csv contains a log of the trace port.

When debug=1 is provided, a vcd file sim.vcd is created and can be browsed by gtkwave or similar waveform viewers.

You can re-execute the simulation using:

make -f $RV_ROOT/tools/Makefile verilator

The simulation run/build command has following generic form:

make -f $RV_ROOT/tools/Makefile [<simulator>] [debug=1] [snapshot=mybuild] [target=<target>] [TEST=<test>] [TEST_DIR=<path_to_test_dir>]

where:

<simulator> -  can be 'verilator' (by default) 'irun' - Cadence xrun, 'vcs' - Synopsys VCS, 'vlog' Mentor Questa
               'riviera'- Aldec Riviera-PRO. if not provided, 'make' cleans work directory, builds verilator executable and runs a test.
debug=1     -  allows VCD generation for verilator and VCS and SHM waves for irun option.
assert=1    -  enables assertions in simulation runs (with simulators other than Verilator)
<target>    -  predefined CPU configurations 'default' ( by default), 'default_ahb', 'typical_pd', 'high_perf' 
TEST        -  allows to run a C (<test>.c) or assembly (<test>.s) test, hello_world is run by default 
TEST_DIR    -  alternative to test source directory testbench/asm or testbench/tests
<snapshot>  -  run and build executable model of custom CPU configuration, remember to provide 'snapshot' argument 
               for runs on custom configurations.
CONF_PARAMS -  allows to provide -set options to veer.conf script to alter predefined EL2 targets parameters

Example:

make -f $RV_ROOT/tools/Makefile verilator TEST=cmark

will build and simulate the testbench/asm/cmark.c program with Verilator.

If you want to compile a test only, you can run:

make -f $RV_ROOT/tools/Makefile program.hex TEST=<test> [TEST_DIR=/path/to/dir]

The Makefile uses the snapshot/<target>/link.ld file, generated by the veer.conf script by default to build the test executable. User can provide test specific linker file in form <test_name>.ld to build the test executable, in the same directory with the test source.

User also can create a test-specific Makefile in <test_name>.makefile, containing building instructions how to create the program.hex file used by simulation. The private Makefile should be in the same directory as the test source. See examples in the testbench/asm directory.

Another way to alter test building process is to use <test_name>.mki file in test source directory. It may help to select multiple sources to compile and/or alter compilation swiches. See examples in the testbench/tests/ directory

(the program.hex file is loaded to instruction and LSU bus memory slaves and optionally to DCCM/ICCM at the beginning of simulation).

User can build the program.hex file by any other means and then run simulation with the following command:

make -f $RV_ROOT/tools/Makefile <simulator>

Note: You may need to delete the program.hex file from the work directory, when running a new test.

The $RV_ROOT/testbench/asm directory contains the following tests ready to simulate:

hello_world       - default test program to run, prints Hello World message to screen and console.log
hello_world_dccm  - the same as above, but takes the string from preloaded DCCM.
hello_world_iccm  - the same as hello_world, but loads the test code to ICCM via LSU to DMA bridge and then executes
                    it from there. Runs on EL2 with AXI4 buses only. 
cmark             - coremark benchmark running with code and data in external memories
cmark_dccm        - the same as above, running data and stack from DCCM (faster)
cmark_iccm        - the same as above with preloaded code to ICCM (slower, optimized for size to fit into default ICCM). 

dhry              - Run dhrystone. (Scale by 1757 to get DMIPS/MHZ)

The $RV_ROOT/testbench/hex directory contains precompiled hex files of the tests, ready for simulation in case RISC-V SW tools are not installed.

Note: The testbench has a simple synthesizable bridge that allows you to load the ICCM via load/store instructions. This is only supported for AXI4 builds.