dau utils

Host-side operational utilities for DAU bench work

Overview

Small, package-neutral utilities for operating FPGA bench hosts. Each owns one mechanism; policy (which devices, when to arm) belongs to the caller — higher layers such as dau-build compose these into their hardware command plans.

Deadman: survive a wedged PCIe device

A driver/PCIe hang can leave the kernel and systemd alive — the hardware watchdog keeps getting petted, yet a clean systemctl reboot blocks on the stuck device, and the box needs a walk to the power switch. The deadman arms a forced reboot before the risky operation and cancels it on success:

dau-utils-deadman arm --timeout 300     # transient systemd timer; survives SSH loss
# ... rescan / flash / probe ...
dau-utils-deadman disarm                # clean return: cancel the reset
dau-utils-deadman status

If the host wedges before disarm, the timer fires sysrq-b (emergency_restart()), which resets past the wedged driver without touching it. The same operations are available as a Python API (dau_utils.deadman.arm/disarm/is_armed and an armed() context manager); failures raise DeadmanError — treat the host as unsafe.

Arm it before every PCIe rescan, flash, or register probe against a device that has previously wedged. Synthesis and other non-PCIe work does not need it.

Runtime PM: hold and release PCIe power management

dau-utils-pci-runtime-pm holds or releases Linux PCI runtime PM for devices matched from lspci -Dnn. The caller decides which patterns matter; this utility owns the sysfs writes:

dau-utils-pci-runtime-pm hold    --pattern Thunderbolt --pattern 10ee:7011
dau-utils-pci-runtime-pm release --pattern Thunderbolt --pattern 10ee:7011

Use --dry-run to print the planned writes without touching sysfs.

Development

pip install -e .[develop]
python -m pytest dau_utils/tests
python -m ruff check dau_utils

Note

This library was generated using copier from the Base Python Project Template repository.