linux-kernel - Re: [PATCH] powercap / RAPL : remove dependency on iosf

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Message-ID: <20150921143629.4f597e1c@icelake>
Date:	Mon, 21 Sep 2015 14:36:29 -0700
From:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:	Pengyu Ma <pengyu.ma@...driver.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	<rafael.j.wysocki@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powercap / RAPL : remove dependency on iosf_mbi

On Mon, 21 Sep 2015 11:48:14 +0800
Pengyu Ma <pengyu.ma@...driver.com> wrote:

> 
> 
> On 09/18/2015 11:43 PM, Jacob Pan wrote:
> > On Fri, 18 Sep 2015 02:09:55 +0200
> > "Rafael J. Wysocki" <rjw@...ysocki.net> wrote:
> >
> >> On Thursday, September 17, 2015 03:31:41 PM Pengyu Ma wrote:
> >>> iosf_mbi is supported on Quark, Braswell, Baytrail and some Atom
> >>> SoC, but RAPL is not limited to these SoC, it supports almost
> >>> Intel CPUs. Remove this dependece to make RAPL support more Intel
> >>> CPUs.
> >>>
> >>> Please select IOSF_MBI on Atom SoCs.
> >>>
> > Unlike Quark, I don't think we want to or do differentiate Atom from
> > other x86 at compile time. IOSF driver can be compiled as a module
> > also, therefore RAPL driver needs this explicit dependency at
> > compile time.
> As commit had exported iosf_mbi to let user use it.
> 
> commit aa8e4f22ab7773352ba3895597189b8097f2c307
> Author: David E. Box <david.e.box@...ux.intel.com>
> Date:   Wed Aug 27 14:40:39 2014 -0700
> 
>      x86/iosf: Add Kconfig prompt for IOSF_MBI selection
> 
> 
> While selecting IOSF_MBI is preferred, it does mean carrying extra
> code on non-SoC architectures.
> 
> We can NOT force user to build in iosf_mbi if they want use RAPL on 
> haswell/broadwell/skylake.
> And RAPL can be compiled and worked well on haswell/broadwell/skylake 
> without IOSF_MBI.
> RAPL is really NOT depended on IOSF_MBI.
> 
True for haswell/broadwell/skylake platforms. But if we want binary
compatibility for Atom and Core, I can' see how simply removing the
dependency would work, unless we have runtime detection of IOSF.

> Pengyu
> >>> Signed-off-by: Pengyu Ma <pengyu.ma@...driver.com>
> >> Jacob?
> >>
> >>> ---
> >>>   drivers/powercap/Kconfig | 2 +-
> >>>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/powercap/Kconfig b/drivers/powercap/Kconfig
> >>> index 85727ef..a7c81b5 100644
> >>> --- a/drivers/powercap/Kconfig
> >>> +++ b/drivers/powercap/Kconfig
> >>> @@ -17,7 +17,7 @@ if POWERCAP
> >>>   # Client driver configurations go here.
> >>>   config INTEL_RAPL
> >>>   	tristate "Intel RAPL Support"
> >>> -	depends on X86 && IOSF_MBI
> >>> +	depends on X86
> >>>   	default n
> >>>   	---help---
> >>>   	  This enables support for the Intel Running Average
> >>> Power Limit (RAPL)
> >>>
> > [Jacob Pan]
> 

[Jacob Pan]
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