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

[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?

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?

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

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

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

Any guidance on resolving or further diagnosing this issue would be
highly appreciated.

Best regards,
Naveen