linux-kernel - Re: cpuinfo shows wrong MHz value

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Date:	Mon, 16 Feb 2009 19:13:15 +0100
From:	Thomas Renninger <trenn@...e.de>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: cpuinfo shows wrong MHz value

On Monday 16 February 2009 17:50:08 Matthew Garrett wrote:
> On Mon, Feb 16, 2009 at 02:19:50PM +0000, Thomas Renninger wrote:
> 
> > There should be a message when this driver is loaded like:
> > "This driver is broken. Don't use it, don't complain."
> 
> Please don't. It's perfectly valid (if dumb) for machines to depend on 
> the CPU for passive cooling even if they don't expose any P or T states.
No it's not valid. If the BIOS does not export these, it could be for
a reason.

> In that case p4-clockmod is the only code that can manage it. The 
> removal of the user-visible cpufreq interface should be a strong enough 
> hint that it's not intended for speed control.
AFAIK p4-clockmode is still not synchronized with ACPI throttling?
Thus this driver will destroy a valid machine setup where the BIOS exports
throttling states via ACPI.
The driver is broken (and rather useless) and all the complaints about it
get annoying.

I wonder how dangerous it even is. If thermal management on a P4 is 
properly implemented via "BIOS throws high temperature MCE and throttles 
the CPU itself", could the p4_clockmode driver override the BIOS/HW
settings and still run unthrottled? Danger!

Anyway, I better do not answer on p4_clockmode complaints anymore and
simply delete them, it's just a waste of time.

     Thomas
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