linux-kernel - Re: [PATCH 1/2] CPUFREQ: Enable acpi-cpufreq driver for VIA/Centaur CPUs

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Date:	Mon, 8 Jun 2009 15:03:28 -0500
From:	"Michael S. Zick" <lkml@...ethan.org>
To:	Harald Welte <HaraldWelte@...tech.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Duane Griffin <duaneg@...da.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH 1/2] CPUFREQ: Enable acpi-cpufreq driver for VIA/Centaur CPUs

On Mon June 8 2009, Harald Welte wrote:
> The VIA/Centaur C7, C7-M and Nano CPU's all support ACPI based cpu p-states
> using a MSR interface.  The Linux driver just never made use of it, since in
> addition to the check for the EST flag it also checked if the vendor is Intel.
> 
> Signed-off-by: Harald Welte <HaraldWelte@...tech.com>
> ---
>  arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> index 208ecf6..ee03585 100644
> --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> +++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> @@ -90,7 +90,8 @@ static int check_est_cpu(unsigned int cpuid)
>  {
>  	struct cpuinfo_x86 *cpu = &cpu_data(cpuid);
>  
> -	if (cpu->x86_vendor != X86_VENDOR_INTEL ||
> +	if ((cpu->x86_vendor != X86_VENDOR_INTEL &&
> +	     cpu->x86_vendor != X86_VENDOR_CENTAUR) ||
>  	    !cpu_has(cpu, X86_FEATURE_EST))
>  		return 0;
>  

For my own internal testing, based on subsequent posts, I simplified
that to:

static int check_est_cpu(unsigned int cpuid)
{
        struct cpuinfo_x86 *cpu = &cpu_data(cpuid);

        if (!cpu_has(cpu, X86_FEATURE_EST))
                return 0;

        return 1;
}

Have not done anything (yet) to deal with the adaptive controller,
**which is safe to (not) do on my test system because I know it isn't enabled**

Note: This machine is known to run common, proprietary operating systems,
so I am also assuming its BIOS ACPI is complete enough.

Note 2: Don't try this unless you have a machine to waste.  ;)

Mike
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