Building Linux target¶

The memory controllers synhesized for Rowhammer testing can be utilized as parts of a regular digital design that is capable of booting an operating system. In such scenario the memory controller is used by the operating system for interacting with a DRAM memory. This chapter describes a separate target configuration that has been created in order to synthesize a Linux-capable system that you can run on Antmicro’s RDIMM DDR5 Tester.

Base DDR5 Tester Linux Options¶

The ddr5_tester_linux target is configured via specifying the TARGET_ARGS variable and requires the following arguments:

Additionally, you can set up EtherBone or Ethernet to communicate with the system as described below.

Ethernet Options¶

Etherbone Options¶

Building the RDIMM DDR5 Tester Linux Target¶

After configuring the RDIMM DDR5 Tester Linux, the target can be build with make build. Below you can see a use example of a DDR5 Tester Linux Target with Ethernet configured:

make build TARGET=ddr5_tester_linux TARGET_ARGS="--build --l2-size 256 --iodelay-clk-freq 400e6 --module MTC10F1084S1RC --with-wishbone-memory --wishbone-force-32b --with-ethernet --remote-ip-address 192.168.100.100 --local-ip-address 192.168.100.50"

Interacting with RDIMM DDR5 Tester Linux Target¶

First, load the bitstream onto the RDIMM DDR5 Tester with the help of OpenFPGALoader:

openFPGALoader --board antmicro_ddr5_tester build/ddr5_tester_linux/gateware/antmicro_ddr5_tester.bit --freq 3e6

In order to connect to the board, assign the 192.168.100.100 IP Address to the Ethernet interface that is plugged to the DDR5 Tester board and set up the device if needed, e.g. by running:

ip addr add 192.168.100.100/24 dev $ETH
ip link set dev $ETH up

Where ETH is the name of your Ethernet interface. When the Ethernet interface has been set up correctly, you may access the BIOS console on the DDR5 Tester with:

picocom -b 115200 /dev/ttyUSB2

Setting up a TFTP Server¶

Several Linux boot methods can be invoked here but booting via Ethernet is recommended. In order to enable netboot, you need to set up a TFTP server first.

As an example, below is a quick guide on how to configure a TFTP server for Arch Linux. Firstly, if not equipped already, get an implementation of a TFTP server, for example:

pacman -S tftp-hpa

The TFTP server is configured via a /etc/conf.d/tftpd file. Here’s a suggested configuration for the DDR5 Tester Linux boot process:

TFTP_USERNAME="tftp"
TFTPD_OPTIONS="--secure"
TFTP_DIRECTORY="/srv/tftp"
TFTP_ADDRESS="192.168.100.100:69"

TFTP_ADDRESS is specified with the --remote-ip-address option whilst building the target and the port is the default one for the TFTP server. The TFTP_DIRECTORY is the TFTP’s root directory.

To start the TFTP service, run:

systemctl start tftpd

To check whether the TFTP sever is set up properly, run:

cd /srv/tftp/ && echo "TEST TFTP SERVER" > test

cd ~/ && tftp 192.168.100.100 -c get test

The test file should appear in the home directory with “TEST TFTP SERVER” as its content.

Booting Linux on RDIMM DDR5 Tester Linux Target¶

You will need the following binaries:

• Linux kernel Image

• Compiled devicetree

• Opensbi’s fw_jump.bin

• rootfs.cpio

All of these can be obtained with the use of provided firmware/ddr5_tester/buildroot buildroot external configuration. To build binaries with buildroot, run:

git clone --single-branch -b 2023.05.x https://github.com/buildroot/buildroot.git
pushd buildroot
make BR2_EXTERNAL="$(pwd)/../firmware/ddr5_tester/buildroot" ddr5_vexriscv_defconfig

Then, transfer the binaries to the TFTP root directory:

mv buildroot/output/images/* /srv/tftp/
mv /srv/tftp/fw_jump.bin /srv/tftp/opensbi.bin

The address map of the binaries alongside boot arguments can be contained within the boot.json file, for example:

{
    "/srv/tftp/Image":        "0x40000000",
    "/srv/tftp/rv32.dtb":     "0x40ef0000",
    "/srv/tftp/rootfs.cpio":  "0x42000000",
    "/srv/tftp/opensbi.bin":  "0x40f00000",
    "bootargs": {
        "r1":   "0x00000000",
        "r2":   "0x40ef0000",
        "r3":   "0x00000000",
        "addr": "0x40f00000"
    }

With Linux boot binaries in the TFTP’s root directory with boot.json, netboot can be invoked from the BIOS console with:

netboot /srv/tftp/boot.json

Upon successful execution a similar log will be printed:

litex> netboot /srv/tftp/boot.json
Booting from network...
Local IP: 192.168.100.50
Remote IP: 192.168.100.100
Booting from /srv/tftp/boot.json (JSON)...
Copying /srv/tftp/Image to 0x40000000... (7395804 bytes)
Copying /srv/tftp/rv32.dtb to 0x40ef0000... (2463 bytes)
Copying /srv/tftp/rootfs.cpio to 0x42000000... (22128128 bytes)
Copying /srv/tftp/opensbi.bin to 0x40f00000... (1007056 bytes)
Executing booted program at 0x40f00000

--============= Liftoff! ===============--

Then, the OpenSBI and Linux boot log should follow:

OpenSBI v1.3-24-g84c6dc1
   ____                    _____ ____ _____
  / __ \                  / ____|  _ \_   _|
 | |  | |_ __   ___ _ __ | (___ | |_) || |
 | |  | | '_ \ / _ \ '_ \ \___ \|  _ < | |
 | |__| | |_) |  __/ | | |____) | |_) || |_
  \____/| .__/ \___|_| |_|_____/|____/_____|
        | |
        |_|

Platform Name             : LiteX / VexRiscv-SMP
Platform Features         : medeleg
Platform HART Count       : 8
Platform IPI Device       : aclint-mswi
Platform Timer Device     : aclint-mtimer @ 100000000Hz
Platform Console Device   : litex_uart
(...)
[    0.000000] Linux version 5.11.0 (riscv32-buildroot-linux-gnu-gcc.br_real (Buildroot 2023.05.2-154-g787a633711) 11.4.0, GNU ld (GNU Binutils) 2.38) #2 SMP Mon Sep 25 10:52:22 CEST 2023
[    0.000000] earlycon: sbi0 at I/O port 0x0 (options '')
[    0.000000] printk: bootconsole [sbi0] enabled
(...)

And then:

Welcome to Buildroot
buildroot login: root
             _     _
            | |   (_)
            | |    _ _ __  _   ___  __
            | |   | | '_ \| | | \ \/ /
            | |___| | | | | |_| |>  <
            \_____/_|_| |_|\__,_/_/\_\
                      _ _   _
                     (_) | | |
            __      ___| |_| |__
            \ \ /\ / / | __| '_ \
             \ V  V /| | |_| | | |
              \_/\_/ |_|\__|_| |_|
            __________________ _____
            |  _  \  _  \ ___ \  ___|
            | | | | | | | |_/ /___ \
            | | | | | | |    /    \ \
            | |/ /| |/ /| |\ \/\__/ /
            |___/ |___/ \_| \_\____/

  32-bit RISC-V Linux running on DDR5 Tester.

login[65]: root login on 'console'