On PoE sites the MIPI-DSI panel can lose its init on a supply dip while the
RK3566 keeps running; the UI may also hang or exit. Three layers:
- hardware watchdog: systemd RuntimeWatchdogSec=20s (system.conf.d)
- GUI: SdWatchdog pings systemd per swapped frame (WATCHDOG_USEC=30s, enabled
by the binary so older versions run under the same unit) and writes
run/qt.frame; buttontask.service gets Restart=always, NotifyAccess=main,
TimeoutAbortSec=10s
- bt-displaywatch (root, buttontask-displaywatch.service): kernel DRM/DSI
timeouts, eth link down->up (PoE dip hint), stale UI frames, restart storms
-> panel re-init (stop UI, fb0 blank 4->0, start UI), repeated -> reboot
(max 3/day, never during OTA); incident log in /var/log/buttontask/
Manual recovery: hold one finger 10 s in the bottom-left corner (panels are
single-touch). Delivered by OTA via bt-update sync_system; the web service
runs `bt-update sync-system` at start for devices updated by an older
bt-update.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
GrigoandClaude Opus 5.5
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