Blank Screen / Unresponsive Keyboard Investigation

diagnosis and summary thanks to Claude

Symptom

On this Dell 14 Plus 2-in-1 (Intel Lunar Lake, Arc 130V/140V graphics), the screen occasionally goes completely black and the keyboard stops responding — except F5 (keyboard backlight toggle) still works. Happens after long periods of inactivity with the laptop lid open (not closed), on battery power. Connecting/disconnecting the charger while stuck made no difference.

Diagnosis

Checked journalctl/dmesg across ~10 recent boots. No kernel panics, GPU hangs/resets, or unclean shutdowns were logged — but a clear pattern emerged:

  • Aug 23, 19:17:06 — system entered suspend (s2idle) after the 15-minute battery idle timeout
  • ~20:34–20:35 (≈78 min later) — kernel and networking resumed successfully (confirmed via Tailscale reconnect logs scrambling back online at that exact time)
  • Display and input never came back — nothing further logged until a hard power-cycle forced a new boot

Root cause: the kernel resumes from suspend correctly, but the xe gra driver / Wayland compositor fails to reinitialize the display pipeline afterward — a known class of bug on this very new Lunar Lake + xe driver combination. Backlight toggling works because backlight toggling is handled by the EC/ACPI layer directly, not through the wedged compositor. BIOS was already current (1.11.0), so this is a driver-side issue, not a firmware gap.

Fix Applied

Disabled auto-suspend on battery so the machine can’t hit the broken resume. It will still blank/lock the screen on idle, just won’t suspend:

gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-battery-type ‘nothing’

Verified current settings:

Setting Value
sleep-inactive-battery-type nothing
sleep-inactive-battery-timeout 900s
sleep-inactive-ac-type nothing
sleep-inactive-ac-timeout 3600s

Safe Recovery (if it happens again before/without this fix)

Instead of holding the power button (risks filesystem corruption from unflushed writes), use the Magic SysRq key — handled directly by the kernel’s keyboar interrupt handler, bypassing the frozen compositor entirely.

This system’s SysRq is enabled at level 176 (Ubuntu default), which permits only:

  • S — sync disks (flush dirty pages)
  • U — remount filesystems read-only
  • B — reboot

(R/E/I — raw keyboard toggle and process terminate/kill — are disabled by default on Debian/Ubuntu and won’t do anything here.)

To use: hold Alt+SysRq (often shares the PrtScn key, sometimes need tap S, release, tap U, release, tap B — with a brief pause between each.