linux-kernel - Re: [PATCH 1/2] CPUFREQ: Enable acpi-cpufreq driver for VIA/Centaur CPUs

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Message-Id: <200906081341.44403.lkml@morethan.org>
Date:	Mon, 8 Jun 2009 13:41:30 -0500
From:	"Michael S. Zick" <lkml@...ethan.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Harald Welte <HaraldWelte@...tech.com>,
	Duane Griffin <duaneg@...da.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH 1/2] CPUFREQ: Enable acpi-cpufreq driver for VIA/Centaur CPUs

On Mon June 8 2009, Linus Torvalds wrote:
> 
> On Mon, 8 Jun 2009, Harald Welte wrote:
> >
> > The VIA/Centaur C7, C7-M and Nano CPU's all support ACPI based cpu p-states
> > using a MSR interface.  The Linux driver just never made use of it, since in
> > addition to the check for the EST flag it also checked if the vendor is Intel.
> > 
> > Signed-off-by: Harald Welte <HaraldWelte@...tech.com>
> > ---
> >  arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c |    3 ++-
> >  1 files changed, 2 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> > index 208ecf6..ee03585 100644
> > --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> > +++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> > @@ -90,7 +90,8 @@ static int check_est_cpu(unsigned int cpuid)
> >  {
> >  	struct cpuinfo_x86 *cpu = &cpu_data(cpuid);
> >  
> > -	if (cpu->x86_vendor != X86_VENDOR_INTEL ||
> > +	if ((cpu->x86_vendor != X86_VENDOR_INTEL &&
> > +	     cpu->x86_vendor != X86_VENDOR_CENTAUR) ||
> >  	    !cpu_has(cpu, X86_FEATURE_EST))
> 
> Hmm. This all really should be just
> 
> 	static int check_est_cpu(unsigned int cpuid)
> 	{
> 		struct cpuinfo_x86 *cpu = &cpu_data(cpuid);
> 		return cpu_has(cpu, X86_FEATURE_EST);
> 	}
> 
> I suspect, with no vendor tests. That's the whole _point_ of CPU features, 
> after all.
> 
> If some vendor claims EST but doesn't actually support the EST interfaces, 
> we should just have fixups to clear the bit in the per-vendor cpuinfo 
> code, not in some random driver.
> 
> The only thing that makes me nervous about this is how close to 2.6.30 we 
> are. I'd be happier if this was resolved by doing this as a patch 
> post-2.6.30, and then adding 'stable@...nel.org' as a Cc: tag, and 
> backporting it to 2.6.30.1 if no problems appear. 
> 
> It's not like this is a regression, I think.
> 
> Does that sound like a reasonable plan?
> 

Sounds like a plan to me - it has been broke a long time - a little longer...
I can continue to carry any change we code up as a local patch until it
gets done at the mainline level.
There are only about 20,000 of these old Everex machines ever produced.

Mike
> 		Linus
> 
> 


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