Revolution Pi Connect SE + Debian Bookworm 64 bit

Board Integrations
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The official Mender documentation explains how Mender works. This is a board-specific complement to the official documentation.

Topic title should be in the format: <board type> + <OS>

Suggested title: Revolution Pi Connect SE + Debian Bookworm 64 bit

Device description

Revolution Pi (Kunbus) is an industrial DIN-rail platform based on the Raspberry Pi Compute Module. The RevPi Connect SE uses a Raspberry Pi Compute Module 4S (brcm,bcm2711, revision type 0x15).

Verified on a working Bullseye Mender image on the same hardware:

Property Value
/proc/device-tree/model Raspberry Pi Compute Module 4S Rev 1.0
/proc/device-tree/compatible kunbus,revpi-connect-se, brcm,bcm2711
OS (working control) Debian 11 (bullseye), kernel 6.1.174-rt51-v8

There is no dedicated CM4S / Connect SE config in mender-convert. Closest advertised path is the Raspberry Pi 4 Bookworm 64-bit U-Boot config (same SoC family).

Support level

Board / OS Status
RevPi Connect SE + Debian Bullseye 64-bit + Mender U-Boot Works (same U-Boot generation as below)
RevPi Connect SE + Debian Bookworm 64-bit + stock mender-convert Does not boot — early hang after color splash (confirmed)
Other RevPi variants (Core, Compact, Connect 4/5, …) Not tested here

Tested mender-convert versions (Bookworm hang):

  • 5.2.1 — hang confirmed on hardware
  • master @ e7bff87 (5.2.1-40-ge7bff87) — same hang confirmed on hardware

Both pin the same U-Boot asset: raspberrypi_arm64-2024.04.tar.gz (Mender branch mender-rpi-2024.04``Preformatted text).

Getting started

Follow the official guide: Convert a Mender Debian image.

Input image: official KUNBUS RevPi Bookworm 64-bit lite, e.g. 2026-03-17-revpi-bookworm-arm64-lite.img.

Important before convert:

  1. Boot the vendor image once and complete Kunbus first-boot setup (serial / MAC / model) before converting, same as for Bullseye integrations.
  2. Grow the root partition if needed — the stock lite rootfs is often 100% full, so apt fails while installing Mender packages. Growing root by ~1 GiB is a convert-time prerequisite, not the boot bug below.

Config used for the Bookworm attempt:

./docker-build

MENDER_ARTIFACT_NAME=revpi-bookworm-1 \
  ./docker-mender-convert \
    --disk-image input/2026-03-17-revpi-bookworm-arm64-lite-grown.img \
    --config configs/raspberrypi/uboot/debian/raspberrypi4_bookworm_64bit_config \
    --overlay input/rootfs_overlay_demo

That config installs Mender RPi U-Boot as kernel8.img (MENDER_DEVICE_TYPE=raspberrypi4_64, boot mount /boot/firmware).

Related Bullseye Hub topic (working path on older OS): Revolution Pi + Debian Bullseye 64 bit.

References

  • Docs: Convert a Mender Debian image
  • Config: configs/raspberrypi/uboot/debian/raspberrypi4_bookworm_64bit_config in mender-convert
  • U-Boot build script / branch: build-uboot-rpi64.sh → mender-rpi-2024.04
  • Golden images: Kunbus / Revolution Pi download portal (Bookworm arm64 lite)
  • Detailed repro notes (local): BUG.md in this tree

Known issues

Bookworm + Mender U-Boot 2024.04 early hang (primary)

Symptom: after flashing a stock mender-convert Bookworm image, power-cycle shows the Raspberry Pi color splash, then nothing (no multi-user / SSH). UART on Connect SE is not usable for forensics (PiBridge).

Reproduced with: stock Docker mender-convert on both 5.2.1 and current master — no custom convert hooks, no third-party U-Boot. Convert itself completes successfully; the failure is at early boot.

Strong evidence (controlled bisect on same hardware):

U-Boot 2024.04 + Bullseye CM4S/RevPi FDT   → boots
U-Boot 2024.04 + Bookworm CM4S/RevPi FDT  → early hang
Bookworm Linux + Bookworm CM4S FDT        → boots (vendor image, no Mender U-Boot)

Replacing only Bookworm bcm2711-*.dtb on an otherwise working Bullseye boot VFAT is enough to recreate the hang. So the interesting object is the firmware-provided BCM2711/RevPi FDT handed into U-Boot, not the rootfs alone.

Not the primary cause: missing CM4S model type 0x15 in U-Boot’s rpi_models_new_scheme[] (falls back to “Unknown model” / bcm283x-rpi-other.dtb). On a working Bullseye Mender image, Linux still sees the real RevPi/CM4S tree (kunbus,revpi-connect-se / brcm,bcm2711). That means the unknown-model fdtfile fallback is not what Linux boots from on this Mender path — treat 0x15 support as a separate correctness fix.

Ask to maintainers:

  1. Is Connect SE / CM4S + Bookworm considered supported under raspberrypi4_bookworm_64bit_config, or is a dedicated config needed?
  2. Can Mender RPi U-Boot 2024.04 be fixed (or a newer raspberrypi_arm64-*.tar.gz shipped) to tolerate the Bookworm CM4S/RevPi FDT at fdt_addr?
  3. Separately: add CM4S revision type 0x15 to the RPi model table.
Revolution Pi + Debian Bullseye 64 bit