From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <a.p.zijlstra@chello.nl>
Received: from viefep14-int.chello.at (viefep14-int.chello.at [62.179.121.34])
	by ozlabs.org (Postfix) with ESMTP id 95D9BB7B77
	for <linuxppc-dev@lists.ozlabs.org>;
	Thu,  8 Oct 2009 00:06:47 +1100 (EST)
Subject: Re: [v7 PATCH 0/7]: cpuidle/x86/POWER: Cleanup idle power
	management code in x86, cleanup drivers/cpuidle/cpuidle.c and introduce
	cpuidle to POWER.
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: svaidy@linux.vnet.ibm.com
In-Reply-To: <20091007112648.GC7646@dirshya.in.ibm.com>
References: <20091006152421.GA7278@linux.vnet.ibm.com>
	<20091006163521.GA10425@linux.vnet.ibm.com>
	<1254852279.17055.2.camel@laptop>
	<20091007112648.GC7646@dirshya.in.ibm.com>
Content-Type: text/plain
Date: Wed, 07 Oct 2009 15:05:11 +0200
Message-Id: <1254920711.26976.243.camel@twins>
Mime-Version: 1.0
Cc: linux-arch@vger.kernel.org, Gautham R Shenoy <ego@in.ibm.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
	linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>,
	arun@linux.vnet.ibm.com, Ingo Molnar <mingo@elte.hu>,
	linuxppc-dev@lists.ozlabs.org, Arjan van de Ven <arjan@infradead.org>
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
	<mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
	<mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>

On Wed, 2009-10-07 at 16:56 +0530, Vaidyanathan Srinivasan wrote:
> * Peter Zijlstra <a.p.zijlstra@chello.nl> [2009-10-06 20:04:39]:
> 
> > On Tue, 2009-10-06 at 22:05 +0530, Arun R Bharadwaj wrote:
> > 
> > > Also, the per-cpu nature of registration/unregistration of cpuidle
> > > has been maintained as ACPI needs this.
> > 
> > Right, so can't we ditch that and have acpi default to the lowest
> common
> > C-state and warn when various cpus report different C-states?
> 
> Hi Peter,
> 
> As Arjan mentioned previously, the per-cpu registration has to stay
> for x86 for now due to legacy ACPI compatibility.  Breaking that may
> break lot of existing users and we do not have a clean fallback
> method.  

>>From what I understood some broken ass bioses report different C state
availability on different CPUs in the same SMP system.

I'm suggesting to work around that by limiting all CPUs to the subset of
C states reported on all CPUs, instead of the current mess.

I haven't heard anybody tell me why that wouldn't be possible on x86