====== ACPI on Linux ======

ACPI is usually also implemented in the BIOS/Firmware. In case of buggy implementations it could conflict with Linux ACPI implementation, causing error in the journal. Apparently this is due to faulty communication between a PCI device, the motherboard, and the kernel. 

There are three workarounds, which in all cases involve setting a kernel parameter (if you're using GRUB, here's how it's done):

=== pcie_aspm= ===
Forcibly enable or ignore PCIe Active State Power Management.
     * off   : Don't touch ASPM configuration at all.  Leave any configuration done by firmware unchanged.
     * force : Enable ASPM even on devices that claim not to support it. WARNING: Forcing ASPM on may cause system lockups.

=== pci= ===
  * nomsi: disables Message Signaled Interrupts. I'm not sure exactly what this is, but adding this parameter disables USB devices... so no go.

  * noaer : this shoots the messenger, so to speak. Errors still occur, but they aren't reported, and system logs keep normal proportions.

  * nommconf I've only recently heard about this one. It disables Memory-Mapped PCI Configuration Space, and reverts to the traditional handling of configuration space.


===== Links =====
  * [[https://wiki.archlinux.org/title/Power_management]]
  * [[https://www.kernel.org/doc/Documentation/admin-guide/kernel-parameters.txt]]