linux-kernel - Re: [PATCH] Kconfig powernow-k8 driver should depend on ACPI P-States driver

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Date:	Thu, 17 May 2007 17:04:36 -1000
From:	Joshua Hoblitt <jhoblitt@....hawaii.edu>
To:	Dave Jones <davej@...hat.com>
Cc:	Duane Griffin <duaneg@...da.com>,
	Prakash Punnoor <prakash@...noor.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Daniel Drake <dsd@...too.org>,
	Ed Sweetman <safemode2@...cast.net>
Subject: Re: [PATCH] Kconfig powernow-k8 driver should depend on ACPI P-States driver

I think it's pretty clear that Dave and Daniel were both correct and
that ACPI_PROCESSOR is the correct dependency for multi-socket systems.
However, it's worth noting that this dependency seems to be unrelated to
SMP support.  Ed Sweetman has reported that his single-socket but
multi-core system doesn't require ACPI_PROCESSOR for powernow support.
I just tried booting 2.6.21 w/o SMP support and w/o ACPI_PROCESSOR on
one of my multi-socket/multi-core systems.  Sure enough, powernow 
won't work without ACPI_PROCESSOR:

powernow-k8: Found 1 Dual-Core AMD Opteron(tm) Processor 2220 processors (version 2.00.00)
powernow-k8: BIOS error - no PSB or ACPI _PSS objects

I suppose this means that the BIOS does something different to enable
SMP on a multi-core single socket and multi-socket systems.  Anyways, I
believe the question that needs to be answered is: is it reasonable for
X86_POWERNOW_K8 to select ACPI_PROCESSOR if SMP is set?  I'm not sure we
can do anything more intelligent unless Kconfig had more knowledge of
how the hardware other than just SMP/!SMP.

-J

--
On Wed, May 16, 2007 at 04:48:07PM -0400, Dave Jones wrote:
> On Wed, May 16, 2007 at 08:53:13PM +0100, Duane Griffin wrote:
>  > On 16/05/07, Prakash Punnoor <prakash@...noor.de> wrote:
>  > > Maybe you want to give a hint in the p states driver help text?
>  > 
>  > I think a hint is the right thing to do, but in the PowerNow! driver
>  > rather than the p states one. How about adding something like this to
>  > the X86_POWERNOW_K8 (and X86_POWERNOW_K7?) help text:
> 
> The mobile K7s which had powernow support weren't SMP capable, so they're
> irrelevant.
> 
>  > "ACPI support is required for non-UP systems and requires ACPI_PROCESSOR
>  >  to be selected. If ACPI_PROCESSOR is compiled as a module then this
>  >  option must be too in order for ACPI support to be available."
> 
> X86_POWERNOW_K8_ACPI is already 'default y'. I think the problem lies in
> that people aren't enabling its dependancy, ACPI_PROCESSOR.
> 
> We want something along the lines of..
> 
> config X86_POWERNOW_K8_ACPI
> 	bool
> 	if SMP & X86_POWERNOW_K8_ACPI
> 	  select ACPI_PROCESSOR
> 
> kconfig language quirks aside..
> 
> 
> 	Dave
> 
> -- 
> http://www.codemonkey.org.uk

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