linux-kernel - Re: [PATCH 1/5] acpi-cpufreq: Add support for modern AMD CPUs

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Message-ID: <20110519072646.GB19481@alberich.amd.com>
Date:	Thu, 19 May 2011 09:26:46 +0200
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Matthew Garrett <mjg@...hat.com>
CC:	<linux-kernel@...r.kernel.org>, <borislav.petkov@....com>,
	<davej@...hat.com>, <mark.langsdorf@....com>,
	<cpufreq@...r.kernel.org>
Subject: Re: [PATCH 1/5] acpi-cpufreq: Add support for modern AMD CPUs

On Tue, May 17, 2011 at 01:03:35PM -0400, Matthew Garrett wrote:
> The programming model for P-states on modern AMD CPUs is very similar to
> that of Intel and VIA. It makes sense to consolidate this support into one
> driver rather than duplicating functionality between two of them. This
> patch adds support for AMDs with hardware P-state control to acpi-cpufreq.

I think it's a good idea to move the stuff into the more general
driver.  (And this way powernow-k8 becomes what it is supposed to be
-- relevant for K8 CPUs only.)  From a first glance most stuff looks
fine. (but detailed review and testing still outstanding.)

> Signed-off-by: Matthew Garrett <mjg@...hat.com>
> ---
>  arch/x86/include/asm/cpufeature.h          |    1 +
>  arch/x86/include/asm/msr-index.h           |    2 +
>  arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c |   43 ++++++++++++++++++++++++----
>  arch/x86/kernel/cpu/scattered.c            |    1 +
>  4 files changed, 41 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
> index 91f3e087..fee7089 100644
> --- a/arch/x86/include/asm/cpufeature.h
> +++ b/arch/x86/include/asm/cpufeature.h
> @@ -174,6 +174,7 @@
>  #define X86_FEATURE_PLN		(7*32+ 5) /* Intel Power Limit Notification */
>  #define X86_FEATURE_PTS		(7*32+ 6) /* Intel Package Thermal Status */
>  #define X86_FEATURE_DTS		(7*32+ 7) /* Digital Thermal Sensor */
> +#define X86_FEATURE_POWERNOW	(7*32+ 8) /* AMD frequency scaling */

I think it shouldn't be named like that. I'd rather call it
HW_PSTATE. The more general term POWERNOW is also associated with the
old FID/VID control method of changing frequencies on AMD CPUs.  Also
AMD documentation refers to this feature as HwPstate.


Regards,

Andreas


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