Jamm02/linux-devkit-dev

Linux Development Kit for Shakti SOC'S

The Development kit acts a "One Stop" means to build and deploy linux on a specfic Shakti capable SOC.

To Learn more about the Shakti and its avaliable SOC , details can be found here at (http://shakti.org.in/)

Salient Features

Boots Linux following Version 5.5(Stable)
Makes use of the following Supported Bootloaders such as
- Proxy Kernel(BBL) -> Supported
- OpenSBI -> Supported
- U-Boot -> Work In Progress
Builds a standalone filesystem which can be loaded on to a compatible block device such as SDCard(Work in Progress)

Getting Started

Setting up the Build Enviroment

Get the latest RISCV-Toolchain

This repository uses submodules. You need the --recursive option to fetch the submodules automatically

$ git clone --recursive https://github.com/riscv/riscv-gnu-toolchain

Alternatively :

$ git clone https://github.com/riscv/riscv-gnu-toolchain
$ cd riscv-gnu-toolchain
$ git submodule update --init --recursive

Install the necessary packages

Several standard packages are needed to build the toolchain. On Ubuntu, executing the following command should suffice:

$ sudo apt-get install autoconf automake autotools-dev curl libmpc-dev libmpfr-dev libgmp-dev gawk build-essential bison flex texinfo gperf libtool patchutils bc zlib1g-dev libexpat-dev

Install the toolchain by doing

To build the Newlib cross-compiler, pick an install path. If you choose, say, /opt/riscv, then add /opt/riscv/bin to your PATH now. Then, simply run the following commands,

cd riscv-gnu-toolchain
./configure --prefix=/opt/riscv --with-arch=rv64imac --with-abi=lp64 --with-cmodel=medany
sudo make && sudo make linux

Once the above steps are completed you can find the cross-compile and baremetal binaries in the respective path '/opt/riscv/bin' also assuming you have added it to the PATH variable you can proceed to build linux.

Getting started on linux Devlopment

The linux development repository uses submodules. You need the --recursive option to fetch the submodules automatically

 $ git clone --recursive https://gitlab.com/shaktiproject/software/linux-devkit.git

The development package Supports C-Class 64bit Core,which boots linux on top of Proxy Kernel.

Rapid deployment using BBL as a bootloader

Linux can be built as a payload to BBL by doing the below command.

For instance Shakti C-Class is based on RV64IMAC. So alter the config file.

Location : <Your linux-devkit dir>/buildroot/package/busybox/busybox.config

CONFIG_EXTRA_CFLAGS="-g -march=rv64imac -mabi=lp64"
CONFIG_EXTRA_LDFLAGS="-g -march=rv64imac -mabi=lp64"

Also once the above is done, please rebuild it.

cd linux-devkit

To enable Ethernet support follow the below steps :

Change to 13-sos branch of the linux-devkit.

make bbl

Devlopment Cycle

The Linux Development Kit has the following Directories

BSP(Board Support Packages) -> Used to store all device trees with configuration specific to a SoC.
Bootloaders -> Avaliable Bootloaders which can be bundled with a payload and deployed on a Specific SoC.
Linux-on-Shakti(Submodule Type) -> Linux kernel Repo forked from offical kernel release :https://github.com/torvalds/linux. Currently on v5.5.
Buildroot(Submodule Type) -> Used to Combine the above 3 as a deployable along with filesystem and its utilities.

To develop with this kit the following points below must be adhered to.

If anychange regarding non-submodules or a update is being pushed do create a branch and subsequent merge requests will be processed and approved.
For Updates regarding Linux Kernel and Buildroot please pull appropriate branches below the submodules to make use of them , to above point 1 update if necessary.

Using SOC to Boot Linux

Currently the linux kernel boots on ARTY A7 100t with C-Class.

Assuming you have programmed the board and ready to deploy the bbl follow the below steps.

Open Three terminals,

Miniterm
OpenOcd
RISC-V GDB

Connect to the board using openocd with shakti-sdk

$ cd ~/shakti-sdk/bsp/third_party/vajra
$ sudo $(which openocd) -f ftdi.cfg
Connect to gtkterm or minicom or miniterm with a baudrate of 19200 and port as /dev/ttyUSB

$ sudo miniterm.py /dev/ttyUSB1 19200
Using gdb(riscv64-unknown-elf-gdb) load the bbl , steps are given below.

(gdb) set remotetimeout unlimited
(gdb) target remote localhost:3333
(gdb) file path/to/linux-devkit/bootloaders/riscv-pk/build/bbl
(gdb) load
Once done inspect the memory at 0x80000000 to check if the image is loaded properly.

(gdb) x/10x 0x80000000

GDB after load,

Hit Continue to get the output. Output is displayed in Serial Monitor (Miniterm).
```
(gdb) c  
```
Login details are
```
Login ID : root
Password : shakti
```
One can use "adduser" to add new users .

Linux with minimal filesystem (miniterm)

Using Simulator to Boot linux

Verilog artifacts

Download the verilog artifacts from here

Convert to hex using elf2hex

Follow the instructions in the below link to install riscv-isa-sim. This will give elf2hex binary which we will be using later.

https://github.com/riscv/riscv-isa-sim/blob/master/README.md

Note: set $RISCV to the install path of toolchain. Example: export RISCV=/opt/riscv

Simulation

Extract the verilog-artifacts

$ unzip verilog-artifacts.zip

Copy the bbl binary and start the simulation.

$ cd verilog-artifacts/sim  
$ cp <linux-dev location>/work/riscv-pk/build/bbl ./  
$ elf2hex 8 33554432 bbl 2147483648 > code.mem  
$ ./cclass

The output will be gernerated in a text file "app_log" , make use of tail method to recursively see generated log.

Sample Debug Log

note: If you have already installed toolchain, please use it appropriately.

Jamm02 / linux-devkit-dev