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README.md

EL2 SweRV RISC-V CoreTM 1.2 from Western Digital

This repository contains the SweRV EL2 CoreTM 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 file 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

Dependencies

  • Verilator (4.020 or later) must be installed on the system if running with verilator
  • If adding/removing instructions, espresso must be installed (used by tools/coredecode)
  • RISCV tool chain (based on gcc version 7.3 or higher) must be installed so that it can be used to prepare RISCV 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 SweRV

Configurations

SweRV can be configured by running the $RV_ROOT/configs/swerv.config script:

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

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

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

This will update the default snapshot in $RV_ROOT/configs/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 swerv.config.

This script derives the following consistent set of include files :

$RV_ROOT/configs/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 swerv-iss

Building a model

while in a work directory:

  1. Set the RV_ROOT environment variable to the root of the SweRV directory structure. Example for bash shell:
    export RV_ROOT=/path/to/swerv
    Example for csh or its derivatives:
    setenv RV_ROOT /path/to/swerv

  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:

    set BUILD_PATH environment variable:

    setenv BUILD_PATH snapshots/mybuild

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

    Snapshots are placed in $BUILD_PATH directory

  3. Running a simple Hello World program (verilator)

    make -f $RV_ROOT/tools/Makefile

This command will build a verilator model of SweRV EL2 with 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 SweRV EL2 @WDC !!
----------------------------------
TEST_PASSED

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

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 simulation using:
./obj_dir/Vtb_top
or
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
               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.
<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
<snapshot>  -  run and build executable model of custom CPU configuration, remember to provide 'snapshot' argument 
               for runs on custom configurations.

Example:

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

will simulate 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 $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, containing building instructions how to create program.hex and data.hex files used by simulation. The private makefile should be in the same directory as the test source.
(program.hex file is loaded to instruction bus memory slave and data.hex file is loaded to LSU bus memory slave and optionally to DCCM at the beginning of simulation).

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

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

hello_world      - default tes 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. 

The $RV_ROOT/testbench/hex directory contains precompiled hex files of the tests, ready for simulation in case RISCV 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.

Building an FPGA speed optimized model:
Use -set=fpga_optimize=1 option to swerv.config to build a model that is removes clock gating logic from flop model so that the FPGA builds can run a higher speeds.


Western Digital, the Western Digital logo, G-Technology, SanDisk, Tegile, Upthere, WD, SweRV Core, SweRV ISS, and OmniXtend are registered trademarks or trademarks of Western Digital Corporation or its affiliates in the US and/or other countries. All other marks are the property of their respective owners.

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