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Bug#1131158: linux: regression on ThinkPad T14s Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works

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  Bug#1131158: linux: regression on ThinkPad T14s Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works Andrea V <andreakarimodm@gmail.com> - 2026-03-18 12:10 +0100
    Bug#1131158: linux: regression on ThinkPad T14s Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works Salvatore Bonaccorso <carnil@debian.org> - 2026-03-18 13:50 +0100
    Processed: Re: Bug#1131158: linux: regression on ThinkPad T14s  Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works "Debian Bug Tracking System" <owner@bugs.debian.org> - 2026-03-18 13:50 +0100
    Bug#1131158: Debian Bug #1131158 Alastair Sherringham <alastair@sherringham.net> - 2026-03-19 18:00 +0100

#91718 — Bug#1131158: linux: regression on ThinkPad T14s Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works

Source: linux-signed-amd64
Severity: important
Tags: upstream

Subject: linux-image-6.18.15+deb13-amd64: suspend via s2idle fails to reach S0i3 on ThinkPad T14s Gen 4 AMD, while 6.12.74 works

Package: linux-image-6.18.15+deb13-amd64
Version: 6.18.15-1~bpo13+1
Severity: important
Tags: upstream

Dear Debian Kernel Team,

I am reporting what appears to be a suspend regression in the Debian backports
kernel on a Lenovo ThinkPad T14s Gen 4 AMD (type 21F8CTO1WW).

Summary
-------
On linux-image-6.18.15+deb13-amd64 (6.18.15-1~bpo13+1), suspend enters s2idle
but fails to reach S0i3 / deep low-power idle. The laptop "suspends", but the
fan keeps running and power draw remains high.

On the same machine, the Debian security kernel
linux-image-6.12.74+deb13+1-amd64 (6.12.74-2) works correctly: s2idle reaches
S0i3 successfully and the machine suspends properly.

System
------
- Model: Lenovo ThinkPad T14s Gen 4 AMD (21F8CTO1WW)
- CPU: AMD Ryzen 7 PRO 7840U
- BIOS before testing: 1.25
- BIOS updated during debugging via fwupd to: 1.29
- mem_sleep: [s2idle]
- The platform exposes S0/S4/S5 only; no "deep"/S3 is available

Regression comparison
---------------------
Working kernel:
- linux-image-6.12.74+deb13+1-amd64
- version 6.12.74-2

Failing kernel:
- linux-image-6.18.15+deb13-amd64
- version 6.18.15-1~bpo13+1

Both kernels were tested on the same machine and firmware.

Behavior on failing kernel (6.18.15-1~bpo13+1)
-----------------------------------------------
Relevant journal excerpts from the failing boot:

  Linux version 6.18.15+deb13-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.18.15-1~bpo13+1
  ACPI: PM: (supports S0 S4 S5)
  Low-power S0 idle used by default for system suspend
  systemd-sleep: Performing sleep operation 'suspend'...
  PM: suspend entry (s2idle)
  amd_pmc AMDI0009:00: Last suspend didn't reach deepest state
  systemd-sleep: System returned from sleep operation 'suspend'
  PM: suspend exit

During testing on 6.18, AMD PMC debugfs showed:
- S0ix Residency Time: 0
- Last S0i3 Status: Unknown/Fail

Observed user-visible effect:
- laptop appears suspended
- but fan keeps spinning
- opening the lid resumes the machine

Behavior on working kernel (6.12.74-2)
--------------------------------------
On 6.12.74+deb13+1-amd64, the same machine suspends correctly.

AMD PMC debugfs on the working 6.12 kernel reports:
- Last S0i3 Status: Success
- Time in S0i3: 9852905 us
- Residency Time: 9852905

This strongly suggests a regression between the two Debian kernel versions.

What was already tested
-----------------------
- BIOS updated from 1.25 to 1.29: no fix for 6.18 behavior
- acpi.ec_no_wakeup=1: no fix for 6.18 behavior
- Suspend tested with and without USB-C dock attached
- Suspend tested with dock-side USB/Thunderbolt wake settings adjusted
- The separate lid-close/logind issue was fixed independently and is unrelated

Potentially relevant hardware path
----------------------------------
This platform includes AMD Pink Sardine USB4/Thunderbolt controllers:
- 0000:c5:00.5
- 0000:c5:00.6

While debugging 6.18, amd_pmc debug output suggested USB4 activity remained
significant when suspend failed, but the regression remains reproducible even
after disconnecting the dock.

Installed package versions
--------------------------
- linux-image-6.18.15+deb13-amd64: 6.18.15-1~bpo13+1
- linux-image-6.12.74+deb13+1-amd64: 6.12.74-2
- amd64-microcode: 3.20250311.1
- firmware-linux / firmware-linux-nonfree: 20260110-1~bpo13+1

If needed, I can provide additional logs, but the key point is:
- 6.18 backports fails to reach S0i3 on suspend
- 6.12 on the same machine succeeds

Thanks.


-- System Information:
Debian Release: 13.4
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 6.12.74+deb13+1-amd64 (SMP w/16 CPU threads; PREEMPT)
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to C.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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#91721

Control: reassign -1 src:linux 6.18.15-1
Control: tags -1 + moreinfo

On Wed, Mar 18, 2026 at 11:01:08AM +0000, Andrea V wrote:
> Source: linux-signed-amd64
> Severity: important
> Tags: upstream
> 
> Subject: linux-image-6.18.15+deb13-amd64: suspend via s2idle fails to reach S0i3 on ThinkPad T14s Gen 4 AMD, while 6.12.74 works
> 
> Package: linux-image-6.18.15+deb13-amd64
> Version: 6.18.15-1~bpo13+1
> Severity: important
> Tags: upstream
> 
> Dear Debian Kernel Team,
> 
> I am reporting what appears to be a suspend regression in the Debian backports
> kernel on a Lenovo ThinkPad T14s Gen 4 AMD (type 21F8CTO1WW).
> 
> Summary
> -------
> On linux-image-6.18.15+deb13-amd64 (6.18.15-1~bpo13+1), suspend enters s2idle
> but fails to reach S0i3 / deep low-power idle. The laptop "suspends", but the
> fan keeps running and power draw remains high.
> 
> On the same machine, the Debian security kernel
> linux-image-6.12.74+deb13+1-amd64 (6.12.74-2) works correctly: s2idle reaches
> S0i3 successfully and the machine suspends properly.
> 
> System
> ------
> - Model: Lenovo ThinkPad T14s Gen 4 AMD (21F8CTO1WW)
> - CPU: AMD Ryzen 7 PRO 7840U
> - BIOS before testing: 1.25
> - BIOS updated during debugging via fwupd to: 1.29
> - mem_sleep: [s2idle]
> - The platform exposes S0/S4/S5 only; no "deep"/S3 is available
> 
> Regression comparison
> ---------------------
> Working kernel:
> - linux-image-6.12.74+deb13+1-amd64
> - version 6.12.74-2
> 
> Failing kernel:
> - linux-image-6.18.15+deb13-amd64
> - version 6.18.15-1~bpo13+1
> 
> Both kernels were tested on the same machine and firmware.
> 
> Behavior on failing kernel (6.18.15-1~bpo13+1)
> -----------------------------------------------
> Relevant journal excerpts from the failing boot:
> 
>   Linux version 6.18.15+deb13-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.18.15-1~bpo13+1
>   ACPI: PM: (supports S0 S4 S5)
>   Low-power S0 idle used by default for system suspend
>   systemd-sleep: Performing sleep operation 'suspend'...
>   PM: suspend entry (s2idle)
>   amd_pmc AMDI0009:00: Last suspend didn't reach deepest state
>   systemd-sleep: System returned from sleep operation 'suspend'
>   PM: suspend exit
> 
> During testing on 6.18, AMD PMC debugfs showed:
> - S0ix Residency Time: 0
> - Last S0i3 Status: Unknown/Fail
> 
> Observed user-visible effect:
> - laptop appears suspended
> - but fan keeps spinning
> - opening the lid resumes the machine
> 
> Behavior on working kernel (6.12.74-2)
> --------------------------------------
> On 6.12.74+deb13+1-amd64, the same machine suspends correctly.
> 
> AMD PMC debugfs on the working 6.12 kernel reports:
> - Last S0i3 Status: Success
> - Time in S0i3: 9852905 us
> - Residency Time: 9852905
> 
> This strongly suggests a regression between the two Debian kernel versions.
> 
> What was already tested
> -----------------------
> - BIOS updated from 1.25 to 1.29: no fix for 6.18 behavior
> - acpi.ec_no_wakeup=1: no fix for 6.18 behavior
> - Suspend tested with and without USB-C dock attached
> - Suspend tested with dock-side USB/Thunderbolt wake settings adjusted
> - The separate lid-close/logind issue was fixed independently and is unrelated
> 
> Potentially relevant hardware path
> ----------------------------------
> This platform includes AMD Pink Sardine USB4/Thunderbolt controllers:
> - 0000:c5:00.5
> - 0000:c5:00.6
> 
> While debugging 6.18, amd_pmc debug output suggested USB4 activity remained
> significant when suspend failed, but the regression remains reproducible even
> after disconnecting the dock.
> 
> Installed package versions
> --------------------------
> - linux-image-6.18.15+deb13-amd64: 6.18.15-1~bpo13+1
> - linux-image-6.12.74+deb13+1-amd64: 6.12.74-2
> - amd64-microcode: 3.20250311.1
> - firmware-linux / firmware-linux-nonfree: 20260110-1~bpo13+1
> 
> If needed, I can provide additional logs, but the key point is:
> - 6.18 backports fails to reach S0i3 on suspend
> - 6.12 on the same machine succeeds

As we won't provide more updates to kernels with the 6.18 series, and
moved to 6.19 (with a bpo upload pending as well yet), can you confirm
if the issue persists with 6.19.8-1 from unstable?

Regards,
Salvatore

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#91723 — Processed: Re: Bug#1131158: linux: regression on ThinkPad T14s Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works

Processing control commands:

> reassign -1 src:linux 6.18.15-1
Bug #1131158 [src:linux-signed-amd64] linux: regression on ThinkPad T14s Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works
Bug reassigned from package 'src:linux-signed-amd64' to 'src:linux'.
Ignoring request to alter found versions of bug #1131158 to the same values previously set
Ignoring request to alter fixed versions of bug #1131158 to the same values previously set
Bug #1131158 [src:linux] linux: regression on ThinkPad T14s Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works
Marked as found in versions linux/6.18.15-1.
> tags -1 + moreinfo
Bug #1131158 [src:linux] linux: regression on ThinkPad T14s Gen 4 AMD: 6.18.15 backports fails to reach S0i3 on s2idle, 6.12.74 works
Added tag(s) moreinfo.

-- 
1131158: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1131158
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems

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#91751 — Bug#1131158: Debian Bug #1131158

[Multipart message — attachments visible in raw view] — view raw

I would like to mention that I think this is the same bug I have hit.

I am using Debian Stable but BACKPORTS kernels on a new-ish (Dec 2025) :

Thinkpad P14s Gen6 AMD

I pass the kernel boot parameter :

amdgpu.dcdebugmask=0x10

to fix some X/screen issues (slow redraw, lock-ups).

Suspend works when I close the laptop lid.

However, updating to the last backport kernel "6.18.15+deb13" caused 
suspend to break. The laptop seems to suspend on lid close (red lid 
light starts flashing normally) but in the morning the laptop is warm 
and the battery has drained.

To summarise :

6.18.12+deb13-amd64 -- ok

6.18.15+deb13-amd64 -- BAD suspend

I installed the latest "testing" kernel "6.19.6+deb14+1" and suspend 
works OK again.

6.19.6+deb14+1-amd64 - ok

In case it is useful, I attach the output of lspci.


Cheers,


-- 
Alastair Sherringham
blog : https://www.sherringham.net/blog
art: https://art.sherringham.net

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