https://bugzilla.kernel.org/show_bug.cgi?id=220376
Bug ID: 220376
Summary: Keyboard backlight fails to reinitialize after suspend
(Lenovo Yoga Slim 7 15ILL9, BIOS NYCN69WW)
Product: ACPI
Version: 2.5
Hardware: Intel
OS: Linux
Status: NEW
Severity: high
Priority: P3
Component: EC
Assignee: acpi...@kernel-bugs.osdl.org
Reporter: mattiagu...@gmail.com
Regression: No
On the Lenovo Yoga Slim 7 15ILL9 (Aura Edition, Intel Lunar Lake), the keyboard
backlight becomes non-functional after resuming from suspend.
At boot, the keyboard backlight works correctly. After suspend/resume, writes
to `/sys/class/leds/platform::kbd_backlight/brightness` succeed and the file
updates, but the LED remains off. The issue persists across recent kernel
versions (6.13 to 6.14.3) and appears related to improper reinitialisation of
the EC (Embedded Controller) or missing ACPI notifications on resume.
---
**System Information:**
* Laptop Model: Lenovo Yoga Slim 7 15ILL9 (Aura Edition)
* BIOS Version: NYCN69WW
* UEFI Vendor: Lenovo
* CPU: Intel Lunar Lake
* Kernel: 6.15.8-arch1-1
* Distribution: Arch Linux
* DE: KDE Plasma (Wayland)
* ACPI Kernel Module: ideapad_laptop
* Sysfs Interface: `/sys/class/leds/platform::kbd_backlight/brightness`
---
**Steps to Reproduce:**
1. Boot the system (keyboard backlight works normally)
2. Suspend the system via `systemctl suspend`
3. Resume the system
4. The keyboard backlight is off and remains unresponsive
5. Writing values to `/sys/class/leds/platform::kbd_backlight/brightness`
updates the file but does not turn on the backlight
---
**What Has Been Tried (and Fails):**
* Reloading the `ideapad_laptop` module after resume
* Manually writing to brightness values via sysfs
* Calling known ACPI methods (via `acpi_call`):
* `\KBLI(1)`
* `\_SB.PCI0.LPCB.EC0.KBLI(1)`
* Setting up a systemd resume hook
* Confirmed that no `_Qxx` methods exist for EC events
* Rebooting is the only way to restore keyboard backlight functionality
---
**DSDT Analysis:**
Decompiled DSDT confirms the presence of the `KBLI` method, which stores the
brightness value and notifies a backlight device:
Method (KBLI, 1, NotSerialized)
{
Store (Arg0, KBLV)
Notify (KBLT, 0x80)
}
However, this method is either unreachable post-suspend or ignored due to EC
state.
Other users with the same model have confirmed this issue
Arch Linux forum thread:
[https://bbs.archlinux.org/viewtopic.php?id=305118](https://bbs.archlinux.org/viewtopic.php?id=305118)
Can a kernel-level quirk or EC reset be implemented during resume? Or is this a
firmware bug requiring a fix from Lenovo? Please advise if the report should be
redirected to another subsystem
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