linux-kernel - Re: [RFC PATCH 1/5] x86: Add cpu capability flag X86_FEATURE_TSC_S3

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Date:	Mon, 21 Jan 2013 02:27:29 -0500
From:	Chen Gong <gong.chen@...ux.intel.com>
To:	Feng Tang <feng.tang@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...ux.intel.com>, x86@...nel.org,
	Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/5] x86: Add cpu capability flag
 X86_FEATURE_TSC_S3_NOTSTOP

On Mon, Jan 21, 2013 at 02:38:41PM +0800, Feng Tang wrote:
> Date:	Mon, 21 Jan 2013 14:38:41 +0800
> From: Feng Tang <feng.tang@...el.com>
> To: Thomas Gleixner <tglx@...utronix.de>, John Stultz
>  <john.stultz@...aro.org>, Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin"
>  <hpa@...ux.intel.com>, x86@...nel.org, Len Brown <lenb@...nel.org>,
>  "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
>  linux-kernel@...r.kernel.org
> Cc: Feng Tang <feng.tang@...el.com>
> Subject: [RFC PATCH 1/5] x86: Add cpu capability flag
>  X86_FEATURE_TSC_S3_NOTSTOP
> X-Mailer: git-send-email 1.7.9.5
> 
> On some new Intel Atom processors (Penwell and Cloverview), there is
> a feature that the TSC won't stop S3, say the TSC value won't be
> reset to 0 after resume. This feature makes TSC a more reliable
> clocksource and could benefit the timekeeping code during system
> suspend/resume cycle, so add a flag for it.
> 
> Signed-off-by: Feng Tang <feng.tang@...el.com>
> ---
>  arch/x86/include/asm/cpufeature.h |    1 +
>  arch/x86/kernel/cpu/intel.c       |   12 ++++++++++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
> index 2d9075e..f7e1eac 100644
> --- a/arch/x86/include/asm/cpufeature.h
> +++ b/arch/x86/include/asm/cpufeature.h
> @@ -100,6 +100,7 @@
>  #define X86_FEATURE_AMD_DCM     (3*32+27) /* multi-node processor */
>  #define X86_FEATURE_APERFMPERF	(3*32+28) /* APERFMPERF */
>  #define X86_FEATURE_EAGER_FPU	(3*32+29) /* "eagerfpu" Non lazy FPU restore */
> +#define X86_FEATURE_TSC_S3_NOTSTOP (3*32+30) /* TSC doesn't stop in S3 state */
>  
We have an existed "TSC always running in C3+" feature and name it as
X86_FEATURE_NONSTOP_TSC, so how about naming it with the same style,
like X86_FEATURE_NONSTOP_TSC_S3?


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