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

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Date:	Tue, 23 Mar 2010 12:26:22 +0100
From:	Thomas Renninger <trenn@...e.de>
To:	Borislav Petkov <bp@...64.org>
Cc:	akpm@...ux-foundation.org, davej@...hat.com,
	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

On Monday 22 March 2010 19:38:39 Borislav Petkov wrote:
> From: Mark Langsdorf <mark.langsdorf@....com>
> 
> Starting with model 10 of Family 0x10, AMD processors may have
> support for APERF/MPERF.  Add support for identifying it and using
> it within cpufreq.  Move the APERF/MPERF functions out of the
> acpi-cpufreq code and into their own file so they can easily be
> shared.
> 
> Signed-off-by: Mark Langsdorf <mark.langsdorf@....com>
> Signed-off-by: Borislav Petkov <borislav.petkov@....com>
> ---
>  arch/x86/kernel/cpu/amd.c                  |    6 +++
>  arch/x86/kernel/cpu/cpufreq/Makefile       |    4 +-
>  arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c |   44 +-----------------------
>  arch/x86/kernel/cpu/cpufreq/mperf.c        |   50 ++++++++++++++++++++++++++++
>  arch/x86/kernel/cpu/cpufreq/mperf.h        |    9 +++++
>  arch/x86/kernel/cpu/cpufreq/powernow-k8.c  |    8 ++++
>  6 files changed, 77 insertions(+), 44 deletions(-)
>  create mode 100644 arch/x86/kernel/cpu/cpufreq/mperf.c
>  create mode 100644 arch/x86/kernel/cpu/cpufreq/mperf.h
> 
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index e485825..796f662 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -537,6 +537,12 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
>  		set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC);
>  	}
>  
> +	if (c->cpuid_level >= 6) {
> +		unsigned ecx = cpuid_ecx(6);
> +		if (ecx & 0x01)
> +			set_cpu_cap(c, X86_FEATURE_APERFMPERF);
> +	}
This is nearly identical to (beside c->cpuid_level > 6),
in arch/x86/kernel/cpu/intel.c:
if (c->cpuid_level > 6) {
                unsigned ecx = cpuid_ecx(6);
                if (ecx & 0x01)
                        set_cpu_cap(c, X86_FEATURE_APERFMPERF);
}
I expect you are correct... or could it get moved to general x86 init code?

     Thomas
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