Re: ThinkPad L13 Gen 2 AMD (21AB): Caps Lock LED broken by ACPI GPIO 11 interrupt conflict

["Mark Pearson" <mpearson-lenovo@squebb.ca>]

On Thu, Oct 15, 2026, at 2:48 PM, Mario Limonciello wrote:
> On 10/15/26 13:31, Andy Shevchenko wrote:
>> On Thu, Oct 15, 2026 at 09:25:10PM +0300, Andy Shevchenko wrote:
>>> +Cc: Dmitry (as it might be related to keyboard configuration), others for
>>> the previously reported same IRQ on the same GPIO controller but for some
>>> camera stuff.
>>>
>>> On Thu, Oct 15, 2026 at 03:13:02PM +0100, Nikodem Sanecki wrote:
>>>> Hello,
>>>>
>>>> I'm reporting a Caps Lock LED issue on my Lenovo ThinkPad L13 Gen 2 AMD
>>>> running Arch Linux. I found a workaround that completely fixes it, and I
>>>> hope the findings might help implement a permanent kernel fix.
>>>>
>>>> *A quick note:* This is my first time using Linux, and I'm a complete
>>>> beginner when it comes to kernel development. I used ChatGPT (GPT-6) to
>>>> guide the troubleshooting process, analyse my laptop's ACPI firmware, and
>>>> interpret the results. I personally ran the diagnostic commands and
>>>> verified the observed behaviour, but the technical explanation below is
>>>> AI-assisted. Please correct me if any of the analysis is inaccurate.
>>>> Problem
>>>>
>>>> Under Linux, the physical Caps Lock indicator LED never illuminates, even
>>>> though the Caps Lock key itself works normally.
>>>>
>>>> The LED works correctly under Windows and during certain stages of boot, so
>>>> the hardware itself is functional.
>>>>
>>>> After investigating, GPT-6 identified what appears to be a conflict
>>>> involving GPIO 11 on the AMD AMDI0030 controller.
>>>>
>>>> Booting Arch Linux with this kernel parameter completely fixes the problem:
>>>>
>>>> gpiolib_acpi.ignore_interrupt=AMDI0030:00@11
>>>>
>>>> The Caps Lock LED now works normally, and I haven't noticed any other
>>>> hardware issues.
>>>> System information
>>>>
>>>>     -
>>>>
>>>>     Device: Lenovo ThinkPad L13 Gen 2 AMD
>>>>     -
>>>>
>>>>     DMI product name: 21AB004LSP
>>>>     -
>>>>
>>>>     DMI product version/family: ThinkPad L13 Gen 2a
>>>>     -
>>>>
>>>>     DMI vendor: LENOVO
>>>>     -
>>>>
>>>>     DMI product SKU: LENOVO_MT_21AB_BU_Think_FM_ThinkPad L13 Gen 2a
>>>>     -
>>>>
>>>>     Kernel: 7.2.9-arch1-1
>>>>     -
>>>>
>>>>     Distribution: Arch Linux
>>>>     -
>>>>
>>>>     BIOS: R1QET54W (1.40)
>>>>     -
>>>>
>>>>     BIOS date: 2026-04-14
>>>>     -
>>>>
>>>>     DSDT OEM ID: LENOVO
>>>>     -
>>>>
>>>>     DSDT OEM Table ID: TP-R1Q
>>>>
>>>> Diagnostic findings
>>>>
>>>> The following is GPT-6's analysis of the diagnostic output and decompiled
>>>> ACPI tables.
>>>>
>>>> *1. Linux sends the correct keyboard LED commands*
>>>>
>>>> Using bpftrace, we observed that atkbd_set_leds() consistently returned 0.
>>>>
>>>> Tracing ps2_command() for command 0x10ED produced:
>>>>
>>>> SETLEDS: value=4, caps=1
>>>> SETLEDS: value=0, caps=0
>>>> SETLEDS: value=4, caps=1
>>>> SETLEDS: value=0, caps=0
>>>>
>>>> The driver reports success and sends the expected Caps Lock states, but the
>>>> physical indicator stays off.
>>>>
>>>> *2. The embedded controller tracks Caps Lock correctly*
>>>>
>>>> The DSDT defines the CPLS field at EC offset 0x0F, bit 7.
>>>>
>>>> Reading that byte through the read-only ec_sys interface showed it changing
>>>> from 0x00 to 0x80 when Caps Lock was toggled.
>>>>
>>>> Enabling dynamic debugging in drivers/acpi/ec.c confirmed that each Caps
>>>> Lock press triggered EC query 0x78, which was scheduled, started and
>>>> stopped successfully.
>>>>
>>>> *3. Lenovo's firmware controls GPIO 11*
>>>>
>>>> The DSDT contains:
>>>>
>>>> Method (_Q78, 0, NotSerialized)
>>>> {
>>>>      If (CPLS)
>>>>      {
>>>>          WFIO (0x0B, 0x00)
>>>>      }
>>>>      Else
>>>>      {
>>>>          WFIO (0x0B, 0x01)
>>>>      }
>>>> }
>>>>
>>>> The WFIO method writes bit 22 using WMEM(), targeting address 0xFED81500 +
>>>> (11 * 4) = 0xFED8152C.
>>>>
>>>> This appears to control the Caps Lock indicator using GPIO 11.
>>>>
>>>> *4. The same GPIO is declared as an ACPI interrupt*
>>>>
>>>> In SSDT12, _SB.GPIO._AEI declares GPIO 11 as an edge-triggered, active-low,
>>>> exclusive wake interrupt.
>>>>
>>>> Its _EVT handler includes:
>>>>
>>>> Case (0x0B)
>>>> {
>>>>      MSTP (0x3911)
>>>>      Notify (\_SB.PCI0.GPP1, 0x00) // Bus Check
>> 
>> This looks like some GPIO related notification. I dunno what Windows driver does.
>> Mario?
>> 
>
> Honestly - this sounds like a copy / paste BIOS bug that they copied the 
> SSDT from one system and didn't change it.
>
> I would think quirking it makes sense if the BIOS isn't going to be fixed.
>
> Before we go much further can you check if this is the latest BIOS? 
> Check Lenovo's website, in case it wasn't brought to LVFS.
>
> Also; Mark can you ask BIOS guys to look this over?
>
> It sure seems like GPIO 11 shouldn't be in _AEI.
>
Yep - created internal ticket LO-4711
Just a note though - the platform was not in the Linux program (and is rather old) - so my expectations of getting a fix is rather low I'm afraid

I'd get the quirk ready, and if I don't get any feedback from the FW team by next week go ahead with that.

Mark