Bug#1121822: linux: ThinkPad T460s: poweroff leaves FnLock active with Intel PTT (Debian 13, 6.12.57-1)
Source: linux
Version: 6.12.57-1
Severity: important
X-Debbugs-Cc: naibaf.eckidab@gmail.com
Dear Maintainer,
Problem: After shutting down Debian 13 (Trixie) with kernel 6.12.57-1 on a Lenovo ThinkPad T460s, the laptop does not fully power off. The Fn/FnLock indicator light on the keyboard remains on and can still be toggled, even though the screen and fans are off.
Device/Setup: Lenovo ThinkPad T460s. In the BIOS, under Security → Security Chip, “Security Chip Selection” was set to “Intel PTT” and the Security Chip was enabled.
Reproduction:
1. Boot Debian 13 with linux-image-6.12.57-1 on the ThinkPad T460s.
2. Run `systemctl poweroff` (or shut down via the desktop environment).
3. After shutdown completes, the machine appears off (screen and power LED off), but the Fn/FnLock key can still be toggled and its LED changes state. A long press of the physical power button is needed to force a complete power-off.
Expected result: After `systemctl poweroff`, the machine should enter S5 and the embedded controller / keyboard, including the Fn/FnLock LED, should be fully powered off; the Fn key should no longer react.
Workaround/Observation:
- In the BIOS, under Security → Security Chip, changing “Security Chip Selection” from “Intel PTT” to “Disabled” (or to the discrete TPM option if available) and disabling the Security Chip makes the problem disappear.
- With this change, `systemctl poweroff` powers the machine down completely, the Fn/FnLock LED is off and cannot be toggled anymore.
This suggests an interaction between the current Debian kernel (6.12.57-1) and Intel PTT/TPM ACPI handling on the ThinkPad T460s.
-- System Information:
Debian Release: 13.2
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 6.12.57+deb13-amd64 (SMP w/4 CPU threads; PREEMPT)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
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