Re: [coreboot - Bug #657] Alder Lake (x2e_n150) ACPI SCI (IRQ9) Interrupt Storm Escalation up to 180k/sec on FreeBSD/OPNsense

Hello Zooom,

i fixed this for a similiar board i maintain and uploaded to 
coreboot-gerrit. The IRQ 9 storm comes from the Super IO sensing no RPM 
from the cpu fan and raising an alarm!

https://review.coreboot.org/c/coreboot/+/93713/6/Documentation/mainboard/bkhd/1264np_12_4l.md

Please read the part with the Super IO.

I hope i helped. I can suggest a patch for you.

Regards

Sebastian

Am 11.07.2026 um 01:36 schrieb Zoomm Deka via coreboot:
> Issue #657 has been updated by Zoomm Deka.
>
> Description updated
>
> ----------------------------------------
> Bug #657: Alder Lake (x2e_n150) ACPI SCI (IRQ9) Interrupt Storm Escalation up to 180k/sec on FreeBSD/OPNsense
> https://ticket.coreboot.org/issues/657#change-2339
>
> * Author: Zoomm Deka
> * Status: New
> * Priority: Normal
> * Target version: none
> * Start date: 2026-07-10
> * Affected versions: main
> ----------------------------------------
> Following up on the initial observation of interrupt storms on an Intel Alder Lake platform (x2e_n150 mainboard) running FreeBSD 14 / OPNsense 26.7 with a clean Libreboot/coreboot image:
>
>      UART0 (IRQ4): Disabling the serial port via loader hints (hint.uart.0.disabled="1") successfully stopped the IRQ4 storm.
>
>      ACPI SCI (IRQ9): The ACPI storm on IRQ9 escalated drastically post-boot, reaching a critical rate of 181,199 interrupts per second. Attempts to mitigate this via software (e.g., changing the trigger to edge mode using hw.acpi.sci.trigger="edge") were unsuccessful, indicating a persistent level-triggered assertion from the hardware/firmware side.
>
> This storm consumes significant CPU cycles, causing system degradation and immediate hard locks when USB devices or higher IO loads are introduced.
>
> Updated Data from vmstat -i:
> interrupt                          total       rate
> irq9: acpi0                 4241009125     181199
>
> Context & Platform Details:
>
>      Mainboard: x2e_n150 (Intel Alder Lake)
>
>      OS: FreeBSD 14.1-RELEASE / OPNsense 26.7
>
>      Firmware: Clean Libreboot/coreboot compilation (includes commit 4988900789 soc/intel/alderlake: Fix PCI IRQ tables).
>
> The issue points to an unhandled GPE (General Purpose Event) loop or incorrect SCI routing configuration within the Alder Lake ACPI implementation for this specific board variant.
>
>
>
>
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