linux-kernel - Re: [PATCH 3/10 -tip] x86: Add cpufeatures for Advanced Power Management

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Message-Id: <1242395277.3082.24.camel@localhost.localdomain>
Date:	Fri, 15 May 2009 19:17:57 +0530
From:	Jaswinder Singh Rajput <jaswinder@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...nel.org>,
	Robert Richter <robert.richter@....com>,
	Dave Jones <davej@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH 3/10 -tip] x86: Add cpufeatures for Advanced Power
 Management

Hello Thomas,

On Tue, 2009-05-12 at 23:04 +0200, Thomas Gleixner wrote:
> Jaswinder,
> 
> On Wed, 13 May 2009, Jaswinder Singh Rajput wrote:
> > +	/* Advanced Power Management (Function 8000_0007h), edx */
> > +	if (c->extended_cpuid_level >= 0x80000007) {
> > +		c->x86_capability[9] = cpuid_edx(0x80000007);
> 
> In the reply to [Patch 5/10] Ingo wrote:
> >> Also, open-coding x86_capability[9] like that is quite unclean. Were 
> >> we ever to reorder those bits internally, this could would break.
> 
> Do you really believe that open-coding x86_capability[9] in .../common.c
> is better than the open-coding in ../powernow-k8.c ?
> 

BTW, then how you can set x86_capability[9] in one shot ? do you want me
to set each bit with set_cpu_cap() ?

> Again, open-coding is wrong and error prone. Ingo explicitely asked for a
> helper function. All you did is moving the open-coded hard wired array
> reference to a different place.

I am sorry I did not get you, if possible can you please explain your
comment.

I made x86_capability[9] as Advanced Power Management (Function
8000_0007h), edx.
And I moved to X86_FEATURE_CONSTANT_TSC to Advanced Power Management
group as it is the part of it.

I added helper cpufeature for Advanced Power Management availability
so I set in software cpufeature array in vacuum created by
X86_FEATURE_CONSTANT_TSC.

If you have some better suggestion, please let me know.

Thanks for your guidance,
--
JSR


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