Re: ACPI Error: AE_AML_LOOP_TIMEOUT in \_SB.PCI0.SBUS.RDWD & \_SB.PCI0.SBRG.ADP1._PSR

[Armin Wolf <W_Armin@gmx.de>]

Am 19.03.25 um 12:29 schrieb Naveen Kumar P:

> Hi all,
>
> I am encountering repeated AE_AML_LOOP_TIMEOUT errors in the ACPI RDWD
> & \_SB.PCI0.SBRG.ADP1._PSR methods. Below are relevant log entries
> from my system running Linux kernel 6.13.0+:
>
> [77998.038653]
>                 Initialized Local Variables for Method [RDWD]:
> [77998.038691]   Local1: 00000000d0fe9fee <Obj>           Integer
> 0000000000000015
> [77998.038862]   Local6: 00000000f41c1645 <Obj>           Integer
> 0000000000000000
> [77998.039031]   Local7: 0000000040665c5c <Obj>           Integer
> 000000000000AA55
>
> [77998.039237] Initialized Arguments for Method [RDWD]:  (2 arguments
> defined for method invocation)
> [77998.039273]   Arg0:   00000000397dc53d <Obj>           Integer
> 0000000000000014
> [77998.039442]   Arg1:   000000001099e334 <Obj>           Integer
> 0000000000000002
>
> [77998.039673] ACPI Error: Aborting method \_SB.PCI0.SBUS.RDWD due to
> previous error (AE_AML_LOOP_TIMEOUT) (20240827/psparse-529)
> [77998.040455] ACPI Error: Aborting method \_SB.PCI0.SBRG.ADP1._PSR
> due to previous error (AE_AML_LOOP_TIMEOUT) (20240827/psparse-529)
> [77998.043659] ACPI: \_SB_.PCI0.SBRG.ADP1: Error reading AC Adapter
> state: AE_AML_LOOP_TIMEOUT
>
> [78028.442980]
>                 Initialized Local Variables for Method [RDWD]:
> [78028.443019]   Local1: 00000000898a9a7e <Obj>           Integer
> 0000000000000017
> [78028.443192]   Local6: 000000000cf0c853 <Obj>           Integer
> 0000000000000000
> [78028.443362]   Local7: 00000000bb4aa65f <Obj>           Integer
> 000000000000AA55
>
> [78028.443569] Initialized Arguments for Method [RDWD]:  (2 arguments
> defined for method invocation)
> [78028.443606]   Arg0:   00000000ef8d445b <Obj>           Integer
> 0000000000000016
> [78028.443775]   Arg1:   000000006cacc887 <Obj>           Integer
> 0000000000000003
>
> [78028.444006] ACPI Error: Aborting method \_SB.PCI0.SBUS.RDWD due to
> previous error (AE_AML_LOOP_TIMEOUT) (20240827/psparse-529)
> [78028.446366] ACPI Error: Aborting method \_SB.PCI0.SBRG.ADP1._PSR
> due to previous error (AE_AML_LOOP_TIMEOUT) (20240827/psparse-529)
> [78028.451179] ACPI: \_SB_.PCI0.SBRG.ADP1: Error reading AC Adapter
> state: AE_AML_LOOP_TIMEOUT
>
> [78032.877472]
>                 Initialized Local Variables for Method [RDWD]:
> [78032.877509]   Local1: 00000000cf6291ae <Obj>           Integer
> 0000000000000017
> [78032.877682]   Local6: 0000000026aa8a7a <Obj>           Integer
> 0000000000000003
> [78032.877851]   Local7: 00000000acfa20e0 <Obj>           Integer
> 000000000000AA55
>
> [78032.878058] Initialized Arguments for Method [RDWD]:  (2 arguments
> defined for method invocation)
> [78032.878094]   Arg0:   00000000a186096f <Obj>           Integer
> 0000000000000016
> [78032.878262]   Arg1:   00000000d0e1eefe <Obj>           Integer
> 0000000000000003
>
> [78032.878492] ACPI Error: Aborting method \_SB.PCI0.SBUS.RDWD due to
> previous error (AE_AML_LOOP_TIMEOUT) (20240827/psparse-529)
> [78032.881011] ACPI Error: Aborting method \_SB.PCI0.SBRG.ADP1._PSR
> due to previous error (AE_AML_LOOP_TIMEOUT) (20240827/psparse-529)
> [78032.883061] ACPI: \_SB_.PCI0.SBRG.ADP1: Error reading AC Adapter
> state: AE_AML_LOOP_TIMEOUT
>
>
> This issue appears randomly, affecting the RDWD method, which is
> likely responsible for reading data from a bus, and consequently
> causing the _PSR method (power state read) to fail.
>
>
> Questions:
> 1. What typically causes AE_AML_LOOP_TIMEOUT errors?

AFAIK this error is caused by a while loop taking too long to finish. I suspect that
the ACPI bytecode tries to wait for a non-responsive hardware device.

> 2. Could these ACPI errors impact PCI device access?
> Since the error originates from _SB.PCI0.SBUS.RDWD, could this failure
> affect PCI device communication or cause failures when accessing PCI
> devices?

I do not think so, the SBUS device is likely just a SMBus controller attached to the PCI bus.

>
> 3. Could this be a firmware/BIOS issue?If so, what tools or steps
> should I use to verify and debug the ACPI tables?

It is either a hardware issue or a BIOS bug. Can you share the output of the "acpidump" utility
provided by the ACPICA project? Many Linux distributions already package ACPICA in their package repositories.

>
> 4. Is there a recommended workaround to mitigate this issue?

You can check if a BIOS update is available for your device.

>
> 4. How can I debug this further?I can enable additional ACPI debugging
> logs or provide dumps of ACPI tables if necessary.

I can take a look at the \_SB.PCI0.SBUS.RDWD method inside the ACPI table dumps
to see where the error is coming from.

Thanks,
Armin Wolf

>
> Any guidance on resolving or further diagnosing this issue would be
> highly appreciated.
>
> Best regards,
> Naveen
>