Integrating Xenomai 4 on BeagleY-AI: Hard Real-Time Linux

May 28, 2025

Why Xenomai?

While Preempt-RT provides soft real-time capabilities, Xenomai 4 delivers hard real-time performance via its EVL (Evolvable Linux) core. This dual-kernel approach achieves:

Sub-10μs latency for time-critical tasks
Deterministic interrupt handling
Coexistence of real-time and Linux applications

Prerequisites

BeagleY-AI running Debian 12.11 2025-05-21 XFCE
Host Machine: Ubuntu 22.04+ (64-bit) with ARM cross-compiler

Step 1: Obtain Kernel Sources

(Host Machine)

1.1 Clone Beagleboard’s Linux Kernel

git clone https://github.com/beagleboard/linux -b 6.6.58-ti-rt-arm64-r27
cd linux

1.2 Fetch Xenomai EVL Patches

git remote add xenomai https://source.denx.de/Xenomai/xenomai4/linux-evl.git
git fetch xenomai v6.6.y-evl-rebase

Step 2: Merge EVL into TI Kernel

2.1 Create a Merge Branch

git checkout -b ti-xenomai-merge
git merge xenomai/v6.6.y-evl-rebase

2.2 Resolve Merge Conflicts

Focus on:

arch/arm64 (TI-specific changes vs. Xenomai’s EVL modifications)
drivers/ (e.g., SPI, PWM, or Ethernet drivers)
kernel/sched (scheduler conflicts between RT and EVL)

Step 3: Configure the Kernel

3.1 Start with BeagleY’s Default Config

make distclean
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- bb.org_defconfig

3.2 Enable Xenomai EVL

make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig

Key Options:

->Kernel Features                                                                                              
    -> [*]EVL real-time core
        [*]   Enable quota-based scheduling 
        [*]   Enable temporal partitioning policy
        (4)     Number of partitions
        [ ]   Optimize for intra-core concurrency 
        [*]   Collect runtime statistics
        [ ]   Out-of-band networking (EXPERIMENTAL)
        Fixed sizes and limits  --->
        Pre-calibrated latency  --->
        [*]   Debug support  --->

Step 4: Build the Kernel

4.1 Compile Kernel & Modules

make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
    LOCALVERSION="-xenomai" -j$(nproc)
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
     INSTALL_MOD_PATH=./modules modules_install

4.2 Package Artifacts

tar -czf xenomai-kernel-6.6.69-xenomai.tar.gz \
    arch/arm64/boot/Image modules/lib/modules/6.6.69-xenomai

Step 5: Deploy EVL Kernel

5.1 Install on Target

(Target Device BeagleY-AI)

Copy arch/arm64/boot/Image to /BOOT/
Extract modules to /lib/modules
Update /boot/firmware/extlinux/extlinux.conf:

label microSD (default)
    kernel /Image
    append console=ttyS2,115200n8 root=/dev/mmcblk1p3 ro rootfstype=ext4 resume=/dev/mmcblk1p2 rootwait net.ifnames=0 quiet
    fdtdir /
    fdt /ti/k3-am67a-beagley-ai.dtb
    fdtoverlays /overlays/k3-am67a-beagley-ai-csi0-tevs-rpi22.dtbo
    initrd /initrd.img

Validate the kernel version with uname -r and will get:

$ uname -r
6.6.69-xenomai

Step 6: Build & Install Xenomai Libraries

(Native on BeagleY-AI)

6.1 Clone Source

mkdir ~/xenomai && cd ~/xenomai  
git clone https://source.denx.de/Xenomai/xenomai4/libevl.git  
git clone https://source.denx.de/Xenomai/xenomai4/linux-evl.git \
  --depth=1 --branch v6.6.y-evl-rebase

6.2 Build libevl

mkdir build && cd build  
meson setup -Dbuildtype=release -Dprefix=/usr \
            -Duapi=~/xenomai/linux-evl ../libevl  
meson compile  
sudo ninja install

6.3 Validate with EVL test

sudo evl test

Expected Output:

$ sudo evl test
basic-xbuf: OK
clock-timer-periodic: OK
clone-fork-exec: OK
detach-self: OK
duplicate-element: OK
element-visibility: OK
fault: OK
fpu-preload: OK
fpu-stress: OK
heap-torture: OK
mapfd: OK
monitor-deadlock: OK
monitor-deboost-stress: OK
monitor-event: OK
monitor-event-targeted: OK
monitor-event-untrack: OK
monitor-flags: OK
monitor-flags-broadcast: OK
monitor-flags-inband: OK
monitor-pi: OK
monitor-pi-deadlock: OK
monitor-pi-deboost: OK
monitor-pi-stress: OK
monitor-pp-dynamic: OK
monitor-pp-lazy: OK
monitor-pp-lower: OK
monitor-pp-nested: OK
monitor-pp-pi: OK
monitor-pp-raise: OK
monitor-pp-tryenter: OK
monitor-pp-weak: OK
monitor-recursive: OK
monitor-steal: OK
monitor-trylock: OK
monitor-wait-multiple: OK
monitor-wait-requeue: OK
observable-hm: OK
observable-inband: OK
observable-onchange: OK
observable-oob: OK
observable-race: OK
observable-thread: OK
observable-unicast: OK
poll-close: OK
poll-flags: OK
poll-many: OK
poll-multiple: OK
poll-nested: OK
poll-observable-inband: OK
poll-observable-oob: OK
poll-sem: OK
poll-xbuf: OK
proxy-echo: OK
proxy-eventfd: OK
proxy-pipe: OK
proxy-poll: OK
ring-spray: OK
rwlock-read: OK
rwlock-write: OK
sched-quota-accuracy: 99.0%
sched-tp-accuracy: OK
sched-tp-overrun: OK
sem-close-unblock: OK
sem-flush: OK
sem-timedwait: OK
sem-wait: OK
simple-clone: OK
stax-lock: OK
stax-warn: OK
thread-mode-bits: OK

Conclusion

Coming soon

Next Steps:

Coming soon