Bug 680115

Summary:	cpufreq-info displays wrong frequency (DID msr bit not accounted for).
Product:	[Fedora] Fedora	Reporter:	koukou73gr
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	low	Docs Contact:
Priority:	unspecified
Version:	14	CC:	gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda, psabata
Target Milestone:	---
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2011-02-24 22:49:47 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description koukou73gr 2011-02-24 12:00:07 UTC

Description of problem:

cpufreq-info when run as root doesn't seem to understand the Division ID (DID) in the msr which signals the processor's Dynamic FSB Frequency Switching or Super Low Frequency Mode (SLFM) mode is in use.

For example, when my SP9600 is idling in 800MHz it is fed a multiplier of 6 but against an 133MHz bus (266MHz reduced to half in SLFM mode). However,  cpufreq-info when querying directly the hardware (msr?) reports frequency as 1600MHz.

acpi-cpufreq driver seems to know about DID however and if cpufreq-info is run as a user and queries the kernel, it displays the correct 800MHz value.


Version-Release number of selected component (if applicable):
cpufrequtils-008-2.fc14.x86_64
(probably exists in the i686 version too but no way to check)

How reproducible:
Always

Steps to Reproduce:
1. Login as root
2. run cpufreq-info
  
Actual results:
DID bit ignored, wrong frequency displayed when processor in SLFM mode.


Expected results:
DID bit detected and correct frequency displayed.

Additional info:
None

Comment 1 Petr Šabata 2011-02-24 14:01:10 UTC

This is a difference between --freq and --hwfreq.

'cpufreq-info' gets values for both of them from the cpufreq sysfs interface -- scaling_cur_freq and cpuinfo_cur_freq (available only to root) respectively. If there's an issue, it's not in userspace.

Re-assigning to kernel.

Comment 2 koukou73gr 2011-02-24 22:49:47 UTC

Indeed you're correct. There is a discrepancy between the values reported there.

However, looking a bit further, it appears to be caused by the infamous linux-phc patch for processor undervolting I recently used.

This is not a bug of the Fedora kernel. 
I'm sorry I've wasted your bandwidth.