linux-kernel - Re: [PATCH 7/8] cpufreq: Add support for x86 cpuinfo auto loading v3

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Message-ID: <20111222000142.GA10955@alboin.amr.corp.intel.com>
Date:	Wed, 21 Dec 2011 16:01:42 -0800
From:	Andi Kleen <ak@...ux.intel.com>
To:	Dave Jones <davej@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Renninger <trenn@...e.de>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	kay.sievers@....org, kay.sievers@...y.org
Subject: Re: [PATCH 7/8] cpufreq: Add support for x86 cpuinfo auto loading
 v3

> A synthetic one is pointless, because you'd just be duplicating something
> similar to the above in generic code that would need updating for every new stepping.

powernow-k8 uses two mechanisms: family/models and on newer CPUs like
Fam15 a CPUID bit.  Just not in the standard leaves. This would
not need to be updated.

 } else { /* must be a HW Pstate capable processor */
                cpuid(CPUID_FREQ_VOLT_CAPABILITIES, &eax, &ebx, &ecx, &edx);
                if ((edx & USE_HW_PSTATE) == USE_HW_PSTATE)
                        cpu_family = CPU_HW_PSTATE;
                else
                        return;
}

-Andi
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