Created attachment 163901 [details] Kernel log I get the following output on a Dell Inspiron 1525 with Linux 3.18.3: [ 0.150051] ACPI: Interpreter enabled [ 0.150058] ACPI Exception: AE_NOT_FOUND, While evaluating Sleep State [\_S1_] (20140926/hwxface-580) [ 0.150062] ACPI Exception: AE_NOT_FOUND, While evaluating Sleep State [\_S2_] (20140926/hwxface-580) [ 0.150078] ACPI: (supports S0 S3 S4 S5) [ 0.150080] ACPI: Using IOAPIC for interrupt routing [ 0.150107] PCI: Using host bridge windows from ACPI; if necessary, use "pci=nocrs" and report a bug [ 0.189327] ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff]) [ 0.189334] acpi PNP0A03:00: _OSC: OS supports [ExtendedConfig ASPM ClockPM Segments MSI] [ 0.189341] acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM I can't say anything about the former, but for the ASPM part I remember that it used to work with older kernels. I didn't investigate which Linux version worked yet, but I can try to do it if needed. Searching for similar bugs, I see: bug #36932, bug #67241. If this one is also a BIOS bug, then it's OK, but I'm reporting it in case it is not.
Created attachment 163911 [details] ACPI dump
They are harmless. The _S1_ and _S2_ is used by the ACPI table to tell OS if the platform supports S1 and S2 ACPI sleeping state. If they are not defined in the ACPI table, the platform doesn't support it. The debug info " [ 0.189341] acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM" is added in v3.13, so you may not see it in earlier kernels. It means the ACPI table doesn't provide _OSC control method that would affect some of the PCI features like ASPM. There is nothing we can do here in Linux.
Thanks for the explanation. I just booted a 3.10 kernel and confirmed that even there the /sys/module/pcie_aspm/parameters/policy setting cannot be changed (echo gives "Operation not permitted" under root). So I suppose it is working as expected and this bugreport can be closed.