https://bugzilla.kernel.org/show_bug.cgi?id=198779
Bug ID: 198779
Summary: ASRock J3455M (Goldmont) does not reach PC10
Product: ACPI
Version: 2.5
Kernel Version: 4.15.0
Hardware: All
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Power-Processor
Assignee: acpi_power-proces...@kernel-bugs.osdl.org
Reporter: matts...@gmail.com
CC: l...@kernel.org
Regression: No
Created attachment 274151
--> https://bugzilla.kernel.org/attachment.cgi?id=274151&action=edit
turbostat log
powertop shows the CPUs in C10, core in C6, and package in C6. No residency in
PC10. turbostat agrees.
>From the Intel Software Developers' Manual, Vol. 4 [1], I know that there are
MSRs for core C1/C3/C6 and package C2/C3/C6/C10. Also confirmed by the commit
message of 5c10b048c37c ("perf/x86/intel: Enable C-state residency events for
Apollo Lake")
In the attached turbostat log, I noticed something odd:
cpu1: MSR_PKG_CST_CONFIG_CONTROL: 0x14008072 (... pkg-cstate-limit=2 ...)
The BIOS allows you to limit the deepest cstate, with options disabled, C1, C6,
C7, C8, C9, C10. I tried each option and did a "rdmsr 0xe2" with each set:
BIOS limit powertop reports rdmsr 0xe2
disabled no pkg residency 8000
C1 PC2 14008012
C6 PC6 14008032
C7 PC6 14008042
C8 PC6 14008052
C9 PC6 14008062
C10 PC6 14008072
According to ISD Vol 4 [1] Table 2-12, bits 3:0 of Goldmont's
MSR_PKG_CST_CONFIG_CONTROL are:
0000b: No limit
0001b: C1
0010b: C3
0011b: C6
0100b: C7
0101b: C7S
0110b: C8
0111b: C9
1000b: C10
Until C7S, these correspond to bits 7:4 of my readings of 0xe2 (with a missing
C3 fitting in as 14008022). The high bits are the lock bit (bit 15) and
presumably demote/undemote bits, though those are not documented for Goldmont.
Is the BIOS programming the wrong nibble? 0x2 in the low nibble looks like it
would be C3 and maybe the undemotion bit would cause the package to use C6?
Maybe I'm off on a tangent?
[1]
https://software.intel.com/sites/default/files/managed/22/0d/335592-sdm-vol-4.pdf
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