linux-kernel - Re: [PATCH] [18/20] x86: Don't disable TSC in any C states on AMD Fam10h

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Message-ID: <20080104084043.GA27278@elte.hu>
Date:	Fri, 4 Jan 2008 09:40:43 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <ak@...e.de>
Cc:	lenb@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] [18/20] x86: Don't disable TSC in any C states on AMD
	Fam10h


* Andi Kleen <ak@...e.de> wrote:

> The ACPI code currently disables TSC use in any C2 and C3 states. But 
> the AMD Fam10h BKDG documents that the TSC will never stop in any C 
> states when the CONSTANT_TSC bit is set. Make this disabling 
> conditional on CONSTANT_TSC not set on AMD.
> 
> I actually think this is true on Intel too for C2 states on CPUs with 
> p-state invariant TSC, but this needs further discussions with Len to 
> really confirm :-)
> 
> So far it is only enabled on AMD.

thanks Andi - i've picked this up for x86.git, to get it tested. Len, 
what do you think? If/when you pick it up into the ACPI tree i'll drop 
it from x86.git.

	Ingo
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