From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 34542B7334 for ; Thu, 24 Sep 2009 22:25:57 +1000 (EST) Date: Thu, 24 Sep 2009 14:22:28 +0200 From: Arjan van de Ven To: arun@linux.vnet.ibm.com Subject: Re: [v6 PATCH 0/7]: cpuidle/x86/POWER: Cleanup idle power management code in x86, cleanup drivers/cpuidle/cpuidle.c and introduce cpuidle to POWER. Message-ID: <20090924142228.5a2ddf59@infradead.org> In-Reply-To: <20090924051238.GA5963@linux.vnet.ibm.com> References: <20090922112526.GA7788@linux.vnet.ibm.com> <20090924051238.GA5963@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: Peter Zijlstra , Gautham R Shenoy , Venkatesh Pallipadi , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, Paul Mackerras , Shaohua Li , Ingo Molnar , linuxppc-dev@lists.ozlabs.org, Len Brown List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 24 Sep 2009 10:42:41 +0530 Arun R Bharadwaj wrote: > * Arun R Bharadwaj [2009-09-22 16:55:27]: > > Hi Len, (or other acpi folks), > > I had a question regarding ACPI-cpuidle interaction in the current > implementation. > > Currently, every cpu (i.e. acpi_processor) registers to cpuidle as > a cpuidle_device. So every cpu has to go through the process of > setting up the idle states and then registering as a cpuidle device. > > What exactly is the reason behind this? > technically a BIOS can opt to give you C states via ACPI on some cpus, but not on others. in practice when this happens it tends to be a bug.. but it's technically a valid configuration -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org