linux-kernel - Re: [PATCH 2/2] CPUFREQ: Mark e_powersaver driver as EXPERIMENTAL and DANGEROUS

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Date:	Mon, 8 Jun 2009 08:06:18 -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 2/2] CPUFREQ: Mark e_powersaver driver as EXPERIMENTAL and DANGEROUS

On Mon June 8 2009, Harald Welte wrote:
> The e_powersaver driver for VIA's C7 CPU's needs to be marked as
> DANGEROUS as it configures the CPU to power states that are out
> of specification.
> 

I'll put this and your acpi proposal into a test build today - -
If my machine survives, I'll post the build for others to try.

The current build posted (-09159) does not have *either* control
included, leaving the machine running at silicon "#reset" conditions.
Slow - but safe.

Mike
> According to Centaur, all systems with C7 and Nano CPU's support
> the ACPI p-state method.  Thus, the acpi-cpufreq driver should
> be used instead.
> 
> Signed-off-by: Harald Welte <HaraldWelte@...tech.com>
> ---
>  arch/x86/kernel/cpu/cpufreq/Kconfig |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/cpufreq/Kconfig b/arch/x86/kernel/cpu/cpufreq/Kconfig
> index 52c8398..f138c6c 100644
> --- a/arch/x86/kernel/cpu/cpufreq/Kconfig
> +++ b/arch/x86/kernel/cpu/cpufreq/Kconfig
> @@ -220,11 +220,14 @@ config X86_LONGHAUL
>  	  If in doubt, say N.
>  
>  config X86_E_POWERSAVER
> -	tristate "VIA C7 Enhanced PowerSaver"
> +	tristate "VIA C7 Enhanced PowerSaver (DANGEROUS)"
>  	select CPU_FREQ_TABLE
> -	depends on X86_32
> +	depends on X86_32 && EXPERIMENTAL
>  	help
> -	  This adds the CPUFreq driver for VIA C7 processors.
> +	  This adds the CPUFreq driver for VIA C7 processors.  However, this driver
> +	  does not have any safeguards to prevent operating the CPU out of spec
> +	  and is thus considered dangerous.  Please use the regular ACPI cpufreq
> +	  driver, enabled by CONFIG_X86_ACPI_CPUFREQ.
>  
>  	  If in doubt, say N.
>  


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