kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

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Hugh
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kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by Hugh » 2009/09/22 21:46:32

I have an HP Pavilion a530n running CentOS 5.3, up to date.

When running the latest kernel, kernel-2.6.18-164.el5, CPU frequency scaling is disabled.
If I boot the previous kernel, kernel-2.6.18-128.7.1.el5, frequency scaling works.

Here are the motherboard specs: [url=http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00064822&lc=en&dlc=en&cc=ca&product=404646〈=en]http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00064822&lc=en&dlc=en&cc=ca&product=404646〈=en[/url]

On the working system, modules cpufreq_ondemand, powernow_k8, and freq_tables are loaded.
When I try to modprobe powernow_k8 on the non-working system, I get "no such device".

When I first start up my desktop (which has a power frequency monitor applet) with the latest computer, I get an alert box that says:

[quote]CPU frequency scaling unsupported
You will not be able to modicy the frequency of your machine. Your machine may be misconfigured or not have hardware support for CPU frequency scaling.[/quote]

On the working system, dmesg shows these suspicious lines:
[quote]
powernow-k8: Pre-initialization of ACPI failed
powernow-k8: Found 1 AMD Athlon(tm) 64 Processor 3200+ processors (1 cpu cores) (version 2.20.00)
powernow-k8: invalid freq entries 3300000 kHz vs. 2147483048 kHz
powernow-k8: invalid freq entries 3300000 kHz vs. 2147483048 kHz
powernow-k8: 0 : fid 0xc (2000 MHz), vid 0x2
powernow-k8: 1 : fid 0xa (1800 MHz), vid 0x6
powernow-k8: 2 : fid 0x0 (800 MHz), vid 0xa
powernow-k8: ph2 null fid transition 0xc
[/quote]

On the non-working system, dmesg shows these suspicious lines:
[quote]
powernow-k8: Pre-initialization of ACPI failed
powernow-k8: Found 1 AMD Athlon(tm) 64 Processor 3200+ processors (1 cpu cores) (version 2.20.00)
ACPI: Invalid BIOS _PSS frequency: 0x9999999 MHz
powernow-k8: BIOS error: maxvid exceeded with pstate 2
[/quote]
Any idea what's going on? How can I get scaling back?

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AlanBartlett
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Re: kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by AlanBartlett » 2009/09/23 12:51:41

Until such time as our sleepy [b]toracat[/b] is awake and ready to make a comment, I'll suggest you take a look at a certain [url=http://blog.toracat.org/2009/08/go-green-with-newer-amd-processors/]blog posting[/url] to see if it is relevant to your issue.

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toracat
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kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 6

Post by toracat » 2009/09/23 15:26:02

If the previous kernel -128 was working for you, it is possible that a new bug was introduced by the changes made in the -164 kernel. I see at least a couple of powernow-k8-related patches that were added when going from 128 to 164. It could be a regression that affects your hardware. After confirming that there was no problem with the -128 kernel, you may want to file a bug report at http://bugzilla.redhat.com with the details. If you are not comfortable with filing it upstream, you can start with the CentOS bug tracker at http://bugs.centos.org and see if there are other CentOS users experiencing the problem.

Hugh
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Location: Toronto, Canada

Re: kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by Hugh » 2009/09/27 04:24:58

[quote]
AlanJBartlett wrote:
Until such time as our sleepy [b]toracat[/b] is awake and ready to make a comment, I'll suggest you take a look at a certain [url=http://blog.toracat.org/2009/08/go-green-with-newer-amd-processors/]blog posting[/url] to see if it is relevant to your issue.[/quote]
Thanks for your suggestion.

That article is about support for a feature of newer AMD processors: allowing each core's frequency to be scaled separately. My processor is one of the first AMD processors and it doesn't have multiple cores.

Hugh
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Location: Toronto, Canada

Re: kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by Hugh » 2010/01/27 19:57:20

The problem was introduced by a kernel patch: linux-2.6-acpi-check-_pss-frequency-to-prevent-cpufreq-crash.patch

This patch addressed https://bugzilla.redhat.com/show_bug.cgi?id=500311

I have added information to that bz entry but since its status is "CLOSED ERRATA" this may have no effect.

Suggestions welcome!

Summary: my BIOS has a frequency table with two bad entries and three good ones. Before the patch, the kernel complained about an ignored the bad entries and used the good ones. After the patch, the table is ignored if there are any bad entries (where bad means: frequency is some number of megahertz that, when converted to kilohertz, does not fit in a 32-bit unsigned). In my computer's case, the bad frequencies are 0x9999999 MHz, a rather peculiar number.

Hugh
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Re: kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by Hugh » 2010/01/27 21:58:31

See also https://bugzilla.redhat.com/show_bug.cgi?id=559357

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Re: kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by AlanBartlett » 2010/01/28 15:44:50

I wonder if this issue could be addressed in the [i]CentOS-Plus[/i] kernel?

[b]toracat[/b], any opinion / view? :-o

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toracat
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Re: kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by toracat » 2010/01/28 16:02:02

There needs to be a patch before it can be considered for the centosplus kernel. Now that TUV has closed the door (it seems), perhaps filing a bug report at bugs.centos.org may not be a bad idea.

Hugh
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Re: kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by Hugh » 2010/01/29 04:40:09

I have built a 2.6.18-164.11.1.el5 kernel, but without the patch that caused the problem (linux-2.6-acpi-check-_pss-frequency-to-prevent-cpufreq-crash.patch).

I'm now using this kernel. It seems to work the same as the original version except that CPU clock scaling now works.

For those interested, the dmesg output is attached to the Red Hat Bugzilla entry mentioned above.

The correct fix is to improve the patch. After all, it was introduced to fix a problem someone else experienced. Without being able to test on that machine, I wouldn't know if a revised patch would work for it.


I don't really know the rules of the CentOS game. Is there any chance CentOS would diverge from RHEL to fix my problem, or is the only reasonable approach to convince upstream to fix this?


I don't know whether Linus kernels have adopted the problematic patch.

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toracat
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Re: kernel 2.6.18-164.el5 doesn't scale frequency of my Athlon 64

Post by toracat » 2010/01/29 08:28:16

[quote]
Hugh wrote:

I don't really know the rules of the CentOS game. Is there any chance CentOS would diverge from RHEL to fix my problem, or is the only reasonable approach to convince upstream to fix this?
[/quote]
CentOS kernels must be 100% binary compatible with TUV, bug to bug. However, it is [i]possible[/i] to introduce patches and fixes to the centosplus kernel. The best course of action is, of course, to get it fixed upstream.

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