https://bugzilla.kernel.org/show_bug.cgi?id=208785
Bug ID: 208785
Summary: ThunderX2: Thousands errors "PCC check channel failed
for ss: XXX. ret=-110"
Product: ACPI
Version: 2.5
Kernel Version: 5.4.0-42-generic
Hardware: ARM
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Config-Processors
Assignee: acpi_config-process...@kernel-bugs.osdl.org
Reporter: ww8...@gmail.com
Regression: No
I manage Gigabyte R281-T94 server based on two 32-cores ThunderX2 ARM
processor. I found that my ubuntu 20.04 generates thousands such errors:
```
Aug 3 00:33:45 XXXXX kernel: [196168.486836] ACPI CPPC: PCC check channel
failed for ss: 11. ret=-110
Aug 3 00:33:45 XXXXX kernel: [196168.518217] ACPI CPPC: PCC check channel
failed for ss: 46. ret=-110
Aug 3 00:33:45 XXXXX kernel: [196168.518255] ACPI CPPC: PCC check channel
failed for ss: 36. ret=-110
Aug 3 00:33:45 XXXXX kernel: [196168.554905] ACPI CPPC: PCC check channel
failed for ss: 53. ret=-110
Aug 3 00:33:45 XXXXX kernel: [196168.778789] ACPI CPPC: PCC check channel
failed for ss: 6. ret=-110
Aug 3 00:33:45 XXXXX kernel: [196168.824350] ACPI CPPC: PCC check channel
failed for ss: 41. ret=-110
Aug 3 00:33:45 XXXXX kernel: [196168.877658] ACPI CPPC: PCC check channel
failed for ss: 39. ret=-110
```
As I understand that return code `-110` means timeout. I also found that the
message appears in following part of linux kernel code:
https://github.com/torvalds/linux/blame/194098915ac74daddca9d6ed46fd11be57f45e16/drivers/acpi/cppc_acpi.c#L206-L222
```
:~$ cat /proc/version
Linux version 5.4.0-42-generic (buildd@bos02-arm64-077) (gcc version 9.3.0
(Ubuntu 9.3.0-10ubuntu2)) #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020
```
BIOS version: F31 (the most fresh today)
BMC version: 12.44.04 (the most fresh today)
MB_CPLD version: M11 (the most fresh today)
My BIOS have three modes for ACPI:
- Autonomous - CPPC On
- OSPM Turbo
- OSPM Non-Turbo
`OSPM Turbo` is default for me now. I tried all three modes without any effect
on errors.
P.S. I'm ready to communicate and can attach additional information which you
need.
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