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.

Small correction to my original report:
I did not fully disable the security chip. Instead, I changed the BIOS
option ‘Security Chip Selection’ from ‘Intel PTT’ to ‘Discrete TPM’. With
this setting, the system now powers off correctly and the Fn/FnLock LED
stays off.