Dear Maintainer,

*** Summary ***
Under high-concurrency HTTPS/TLS traffic (such as multi-threaded web
scraping or parallel asset downloads), the Intel AC 9560 CNVi wireless
interface triggers a hardware microcode stall that deadlocks the internal
PCH chipset ring bus on Intel 12th Gen (Alder Lake-P) platforms.

*** Symptoms & Absence of Crash Logs ***
- Sudden, instantaneous hard system lockup accompanied by a rhythmically
blinking Caps Lock LED.
- IMPORTANT: No kernel panic backtrace, oops, or kdump vmcore is written to
disk because the sudden freeze deadlocks the internal motherboard PCH bus,
freezing NVMe DMA write transactions before the kernel can flush the crash
logs.
- Both software watchdogs (nmi_watchdog=1, hardlockup_panic=1) and hardware
watchdogs (iTCO_wdt nowayout=1) fail to trigger an automatic platform
reboot due to the PCH bus lockup.
- Hardware integrity was thoroughly ruled out: Memtest86+ v7.20 completed 7
full passes (0 errors across 16GB RAM) and sustained 100% CPU load across
all 12 cores held steady at 62°C without any throttling; the issue
reproduces strictly under multi-stream network traffic over iwlwifi.

*** Hardware & Environment ***
System: Advan WorkPro Laptop
CPU: 12th Gen Intel Core i3-1220P (Alder Lake-P hybrid 2P+8E, 12T)
Kernel: Linux workpro 6.12.101+deb13-amd64 #1 SMP PREEMPT_DYNAMIC Debian
6.12.101-1 (2026-08-05) x86_64 GNU/Linux
OS: Debian GNU/Linux 13 (Trixie) [13.0]
Installation: Fresh, clean Debian 13 installation (a few days old, official
Debian repositories only)
Wireless Device:
00:14.3 Network controller [0280]: Intel Corporation Alder Lake-P PCH CNVi
WiFi [8086:51f0] (rev 01)
DeviceName: Onboard - Ethernet
Subsystem: Intel Corporation Dual Band Wi-Fi 5(802.11ac) Wireless-AC 9560
160MHz 2x2 [Jefferson Peak] [8086:0034]
Kernel driver in use: iwlwifi
Kernel modules: iwlwifi

*** Pre-Freeze Diagnostic Log Snippets (Captured from Prior Boot
Initializations) ***
iwlwifi 0000:00:14.3: Detected Intel(R) Wireless-AC 9560 160MHz
iwlwifi 0000:00:14.3: firmware: failed to load iwlwifi-so-a0-jf-b0-89.ucode
down to 80 (-2 Not Found)
iwlwifi 0000:00:14.3: loaded fallback firmware iwlwifi-so-a0-jf-b0-77.ucode
iwlwifi 0000:00:14.3: 0x00000084 | NMI_INTERRUPT_UNKNOWN
iwlwifi 0000:00:14.3: timeout waiting for FW reset ACK (inta_hw=0x0)
iwlwifi 0000:00:14.3: Failed to start RT ucode: -110

*** Root Cause & Verified Workaround ***
1. Upgraded to firmware-iwlwifi 20260622-1~bpo13+1 from trixie-backports.
2. Configured /etc/modprobe.d/iwlwifi.conf:
   options iwlwifi power_save=0 11n_disable=1
   options iwlmvm power_scheme=1

With 11n_disable=1, the system successfully completed 200 concurrent TLS
streams at 100% throughput with 0 freezes and rock-solid stability.

*** Proposed Action for Debian ***
1. Consider backporting firmware-iwlwifi 20260622 into trixie point
releases.
2. Document or consider module parameter adjustments (11n_disable=1) for
Intel Alder Lake CNVi AC 9560 chipsets to prevent bus deadlocks under high
TLS concurrency.

Hi,

Following up on bug #1145628 with additional testing, a better full-speed
workaround, and distribution comparison:

1. High-Speed Workaround ('swcrypto=1' instead of '11n_disable=1'):
   In the original report, '11n_disable=1' was suggested. However, further
testing revealed that enabling software cryptography:

   /etc/modprobe.d/iwlwifi.conf:
   options iwlwifi swcrypto=1 power_save=0
   options iwlmvm power_scheme=1

   routes WPA encryption through the CPU's hardware AES-NI instructions
rather than the on-chip CNVi microcode engine. This completely prevents the
'NMI_INTERRUPT_UNKNOWN' and 'timeout waiting for FW reset ACK' bus
deadlocks while preserving full 802.11ac high-speed throughput (no
throttling to 54/150 Mbps).

2. Distribution Regression Context (Ubuntu 24.04 LTS vs. Debian 13):
   This exact laptop hardware previously ran Ubuntu 24.04 LTS (Linux Kernel
6.8) for extended periods under heavy multi-stream network traffic with
zero freezes. The issue specifically reproduces on Debian 13 with Linux
Kernel 6.12 when using hardware cryptography on the Intel AC 9560 CNVi
(JF-B0) companion module.

3. PCIe ASPM Interaction:
   Removing forced 'pcie_aspm.policy=performance' restored default dynamic
PCH power management, preventing CNVio bus clock desynchronization during
high-concurrency DMA bursts.

Thank you!