linux-kernel - Re: [PATCH 3/5] cpufreq: Add APERF/MPERF support for AMD processors

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Message-ID: <20100325221638.GA19269@aftab>
Date:	Thu, 25 Mar 2010 23:16:38 +0100
From:	Borislav Petkov <bp@...64.org>
To:	Thomas Renninger <trenn@...e.de>
Cc:	Valdis.Kletnieks@...edu, akpm@...ux-foundation.org,
	davej@...hat.com, linux@...inikbrodowski.net, mingo@...e.hu,
	hpa@...or.com, tglx@...utronix.de, cpufreq@...r.kernel.org,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] cpufreq: Add APERF/MPERF support for AMD processors

From: Thomas Renninger <trenn@...e.de>
Date: Thu, Mar 25, 2010 at 09:59:31PM +0100

> On Thursday 25 March 2010 08:55:19 pm Valdis.Kletnieks@...edu wrote:
> > On Thu, 25 Mar 2010 10:43:04 BST, Thomas Renninger said:
> > > > +	if (c->cpuid_level >= 6) {
> > >
> > > and remove this (arch/x86/kernel/cpu/intel.c):
> > >         if (c->cpuid_level > 6) {
> >
> > So is > or >= the correct comparator here?
> 
> This one: >= is correct (for both).
> I double checked, there is one Intel CPU type
> having a cpuid_level of 6, but this would not support aperf/mperf, thus
> above is still fine.

Agreed. ">" won't work on machines which have base cpuidlevel == 6 (like
AMD, f.e.)

> The remaining question is what Borislav said:
> are there other x86 CPU vendors who could use this differently.
> I very much expect there are not.
> 
> IMO you should resubmit this one or the whole series with this change

Ok, will do tomorrow.

> and Dave should just push this in his tree and queue it up, there was enough
> time to object.

The problem here is that the patches touch both cpufreq and x86 code.
Hmmm...

-- 
Regards/Gruss,
Boris.

--
Advanced Micro Devices, Inc.
Operating Systems Research Center
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