README from GitHub, GPL-2.0

USE THIS AT YOUR OWN RISK!!! I AM NOT RESPONSIBLE IF YOUR MOVE/COMPUTER/OTHER HARDWARE IS DAMAGED OR HAS OTHER UNINTENDED SIDE EFFECTS.

CURRENTLY TESTED ON MOVE WITH CM4 LITE 8GB RAM, CM5 TESTING UNDERWAY!!

Ableton Move Armbian Image and SPI Kernel Driver

Clean-room port of the Move's two SoC-specific pieces - the ablspi kernel module and the device tree - from the original Compute Module 4 (BCM2711, Linux 5.15.92-rt57) image to Armbian/Compute Module 5 (BCM2712, Linux 6.6 LTS + PREEMPT_RT).

Everything else in /opt/move is pure aarch64 user space and rebuilds unchanged against the new SDK; the XMOS-side firmware blobs in /opt/move/Firmware/ are hardware-side and ship as-is.

What's here

port/
├── kernel/
│   ├── ablspi.c       Linux 6.6+ kernel driver, clean-room reimplementation
│   ├── Kbuild
│   ├── Makefile       Out-of-tree build
│   └── (this dir is a drop-in for any kernel >= 6.6)
├── dts/
│   ├── ablspi-move-cm5.dts        Overlay form (recommended)
│   ├── bcm2712-rpi-cm5-move.dts   Standalone wrapper DTS
│   └── ablspi-move-cm5.dtbo       Compiled overlay (regenerate with dtc)
└── README.md

Provenance

The driver is reconstructed from three sources, all of which the project owns lawfully:

ablspi.ko (GPL, 28 KB, retained debug symbols) - the shipped binary on the CM4 image. Used as the structural reference: function names, error strings, /proc layout, statistic counters, IRQ/swait/mmap topology. Running strings on ablspi.ko shows "alias=spi:ablspi , description=SPI driver for CM to XMOS communication , license=GPL, author=Ableton AG". Source has been requested, but at the time of publishing, not been provided.
ablspi.dtbo (decompiled) - the legacy DT binding: compatible = "ablspi", irq-gpio = <3>, SPI0 chip-select 0, custom pinctrl pins 40-43.
Ableton AG's move-spi user-space library, GPL-2.0-or-later. This is the canonical ABI spec - it's the library MoveLauncher/MoveOriginal/MoveWebService and JackMoveDriver all link against to talk to the kernel module. Defines the ioctl numbers, the 4096-byte mmap layout (output region 0..2047, input region 2048..4095), the 768-byte frame size, the 20 MHz bus clock, and the wait-then-duplex-transfer hot path semantics.

No reverse engineering of the Ableton AG GPL-Licensed ablspi.ko binary was needed beyond confirming that the recovered structure matches what the user-space library expects.

ABI surface (must remain stable)

The Move user-space binaries call only two ioctls in the steady state:

#	name	arg	use
10	`ABLSPI_WAIT_AND_SEND_MESSAGE_WITH_SIZE`	size in bytes	hot path
11	`ABLSPI_SET_SPEED`	clock in Hz	init

Plus mmap(NULL, 4096, RW, MAP_SHARED, fd, 0) to map the shared buffer.

The full table of 13 ioctls (0..12) is implemented for parity with the original driver so test harnesses (MoveLibBenchmark, MoveTestHardware) that exercise the legacy commands keep working. See kernel/ablspi.c lines for the enum and per-command handlers.

Shared buffer layout

Single page allocated with alloc_pages(GFP_KERNEL | __GFP_ZERO, 0), mapped to user space via remap_pfn_range. The SPI hot path does one duplex transfer of message_size bytes (default 768) with tx_buf = buffer + 0 and rx_buf = buffer + 2048.

offset      size  direction      contents
─────────── ────  ─────────────  ─────────────────────────────────────
   0          80  CM → XMOS      output USB-MIDI (20 × 4 B)
  80           4  CM → XMOS      output display-status (u32 ack)
  84         172  CM → XMOS      output display-data chunk
 256         512  CM → XMOS      output audio (128 × stereo s16)
 ...
2048         248  XMOS → CM      input USB-MIDI events
2296           8  XMOS → CM      input display-status (drives chunk pull)
2304         512  XMOS → CM      input audio (128 × stereo s16)

Audio rate is fixed at 44.1 kHz, stereo, int16 little-endian, 128 samples per frame (≈ 2.9 ms per duplex transfer).

Driver behaviour notes

Real-time friendly. Uses request_threaded_irq with a NULL primary handler so the wake path runs in a kernel thread that can be tuned with chrt -p. The original /etc/init.d/move script does exactly this (chrt -p 91 \pgrep ablspi``); the threaded model means that scheme continues to work unchanged on the CM5 image.
Streaming DMA. No DMA-coherent allocation - the SPI core maps the page on each transfer via the standard streaming DMA path. Acceptable for 768 B @ 20 MHz (~310 µs of bus time per frame).
Statistics. /proc/ableton/ablspi/<bus>.<cs>/{irq_count, failed_send_count, spi_tx_time} mirror the original /proc entries byte-for-byte where possible (spi_tx_time is richer here - reports last_ns/max_ns/total_ns).
A note on spi_get_chipselect(). Used because rpi-6.6.y took the multi-CS conversion. For pre-6.5 kernels, swap to spi->chip_select.

Building the kernel module

Cross-compile against an rpi-6.6.y tree configured for arm64:

make -C port/kernel \
     KDIR=$HOME/src/linux-rpi-6.6.y \
     ARCH=arm64 \
     CROSS_COMPILE=aarch64-linux-gnu- \
     -j$(nproc)

Native build on the device (kernel headers installed):

ssh root@move.local "cd /root/port/kernel && make"

Install:

make -C port/kernel install KVER=6.6.x-rt-v8   # writes /lib/modules/<ver>/extra

Add to /etc/modules-load.d/ablspi.conf so it loads at boot, like the CM4 image did:

ablspi
i2c-dev
spi-bcm2835    # or whatever the CM5 SPI driver is named on your kernel

Building the device tree

Overlay form (recommended - drops in next to the existing rpi overlays):

cd port/dts
dtc -@ -W no-gpios_property -I dts -O dtb \
    -o ablspi-move-cm5.dtbo ablspi-move-cm5.dts

scp ablspi-move-cm5.dtbo root@move.local:/boot/firmware/overlays/
ssh root@move.local 'printf "dtoverlay=ablspi-move-cm5\n" >> /boot/firmware/config.txt'

Standalone form (replaces the entire DTB - matches the CM4 image's model of shipping move-cm4-complete-devicetree.dtb):

cp port/dts/bcm2712-rpi-cm5-move.dts \
   $HOME/src/linux-rpi-6.6.y/arch/arm64/boot/dts/broadcom/
# append the new entry to broadcom/Makefile next to the other bcm2712 dtbs
make -C $HOME/src/linux-rpi-6.6.y \
     ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
     broadcom/bcm2712-rpi-cm5-move.dtb

Then set device_tree=bcm2712-rpi-cm5-move.dtb in config.txt.

What I deliberately did not do

xmos-power-cycle / xmos-power-off. These are pure shell scripts that call /opt/move/MoveXmosPower (a userland binary that talks to /dev/ablspi0.0 over the same ABI). They work as-is on the new image - no change required.
setup-usb-network-gadget. Pure configfs script. Once the dwc2 controller is enabled in peripheral mode (we did that in the DTS), the script attaches the NCM gadget unchanged.
Intel WiFi. iwlwifi and iwlmvm are upstream drivers; CM5 still routes PCIe to the carrier slot. No port work needed beyond carrying /lib/firmware/iwlwifi/* into the new image.
A/B partition / SWUpdate. Preserve the p1/p2/p3/p4 layout and the /etc/swupdate* config from the CM4 image verbatim. U-Boot environment variables (default_part, fallback_part, bootcount, check_bootcount) port one-to-one once you have a working U-Boot ≥ 2024.01 for BCM2712.

Testing checklist

Once the new image boots:

dmesg | grep ablspi should show one ablspi: ablspi0.0 ready: irq=N speed=20000000Hz frame=768 bytes line.
ls -l /dev/ablspi0.0 exists with the same permissions as before.
cat /proc/ableton/ablspi/0.0/irq_count increments once per XMOS frame (~3 ms / frame → ~340 / s when active).
Start MoveLauncher manually: start-stop-daemon --start -c ableton -b /opt/move/MoveLauncher. The LCD should come up, pads should respond, audio should pass through.
If the LCD stays blank but pads respond, the IRQ path works but the display-pull handshake is stuck - check /proc/ableton/ablspi/0.0/irq_count continues to climb. If it's frozen, the GPIO mapping / pin routing on the carrier differs from the CM4 layout.

Troubleshooting

Move Manager: "No options. Unable to stat path ..." on Recordings / Samples / Presets. Caused by /opt/move/MoveWebService hardcoding the stock data partition (/dev/mmcblk0p4) for a quota lookup that doesn't exist on this single-partition build. Fix: sudo scripts/fix-move-manager-quota.sh (or --host root@move.local). See docs/MOVE_MANAGER_QUOTA_FIX.md.

AI Assistance Disclaimer

This was developed with AI assistance, including Claude, Codex, and other AI assistants.

All architecture, implementation, and release decisions are reviewed by human maintainers. AI-assisted content may still contain errors, so please validate functionality, security, and license compatibility before production use.