VeeR EH1 RISC-V Core

This repository contains the VeeR EH1 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 Predictor
│   ├── include             
│   ├── lib
│   └── lsu                 # Load/Store
├── docs
├── tools                   # Scripts/Makefiles
└── testbench               # (Very) simple testbench
    ├── asm                 # Example test files
    └── hex                 # Canned demo hex files

Dependencies

• Verilator (4.102 or later) must be installed on the system if running with verilator
• If adding/removing instructions, espresso must be installed (used by tools/coredecode)
• A RISC-V tool chain (based on gcc version 7.3 or higher) must be installed so that it can be used to prepare RISC-V binaries to run.

Quickstart guide

1. Clone the repository
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 $PWD/snapshots/default/ with parameters for a 64K DCCM. To unset a parameter, add -unset=PARAM option to veer.config.

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

There are four predefined target configurations: default, default_ahb, default_pd, high_perf that can be selected via the -target=name option in veer.config.

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
├── 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

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

Building an FPGA speed optimized model:
Use -fpga_optimize=1 option in 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 default_pd.

Building a Power optimized model (ASIC flows):
Use -fpga_optimize=0 option in 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 targetdefault_pd.

Running RTL simulations

To run a simple Hello World program in Verilator, use:

make -f $RV_ROOT/tools/Makefile

This command will build a Verilator model of VeeR EH1 with an 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 EH1
-------------------------

Finished : minstret = 443, mcycle = 1372
See "exec.log" for execution trace with register updates..

TEST_PASSED

The simulation generates 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: ./obj_dir/Vtb_top or make -f $RV_ROOT/tools/Makefile verilator.

The simulation run/build command has the following generic form:

make -f $RV_ROOT/tools/Makefile [<simulator>] [debug=1] [snapshot=<snapshot>] [target=<target>] [TEST=<test>] [TEST_DIR=<path_to_test_dir>] [CONF_PARAMS=<veer.config option>]

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 the work directory, builds a Verilator executable and runs a test.
• debug=1 - allows VCD generation for verilator, VCS and Riviera-PRO and SHM waves for irun option.
• <target> - predefined CPU configurations default (by default), default_ahb, default_pd, high_perf
• TEST - allows to run a C (.c) or assembly (.s) test, hello_world is run by default
• TEST_DIR - alternative to test source directory testbench/asm
• <snapshot> - run and build executable model of custom CPU configuration, remember to provide snapshot argument for runs on custom configurations.
• CONF_PARAMS - configuration parameter for veer.config, ex: CONF_PARAMS=-unset=dccm_enable to build with no DCCM

Example:

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

will simulate the testbench/asm/cmark.c program with Verilator on the default target.

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 $RV_ROOT/testbench/link.ld file by default to build 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 form <test_name>.makefile, contaning building instructions how to create a program.hex file used by the simulation. The private Makefile should be in the same directory as the test source.
(the program.hex file is loaded to instruction and data bus memory slaves and optionally to DCCM/ICCM at the beginning of simulation).

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

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

• hello_world - default test to run, prints Hello World message to screen and console.log
• hello_world_dccm - same as above, but takes the string from preloaded DCCM.
• hello_world_iccm - same as above, but CPU copies the code from external memory to ICCM via AXI LSU to DMA bridge and then jumps there. The test runs only on CPU configurations with ICCM and AXI bus.
• cmark - coremark benchmark running with code and data in external memories
• cmark_dccm - same as above, running data and stack from DCCM (faster)
• cmark_iccm - same as above, but with code preloaded to iccm - runs only on CPU with ICCM; use the CONF_PARAMS=-set=iccm_enable argument to make to build CPU with ICCM
• dhry - dhrystone benchmark - example of multi source files program

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.