From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268800AbUHUBEa (ORCPT ); Fri, 20 Aug 2004 21:04:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268785AbUHUBEa (ORCPT ); Fri, 20 Aug 2004 21:04:30 -0400 Received: from gate.crashing.org ([63.228.1.57]:40337 "EHLO gate.crashing.org") by vger.kernel.org with ESMTP id S268800AbUHUBEN (ORCPT ); Fri, 20 Aug 2004 21:04:13 -0400 Subject: Re: SMP cpu deep sleep From: Benjamin Herrenschmidt To: Wes Felter Cc: Linux Kernel list In-Reply-To: References: <1092989207.18275.14.camel@linux.local> Content-Type: text/plain Message-Id: <1093049624.9932.262.camel@gaston> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Sat, 21 Aug 2004 10:53:45 +1000 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2004-08-21 at 02:44, Wes Felter wrote: > The CPU hotplug patch is the way to go, but the hardware is the problem. I > talked to an Intel CPU architect at MICRO last year and he confirmed that > SMP Intel systems don't support any low-power modes besides HLT. AMD's > documentation says that Opterons support voltage/frequency scaling (aka > Cool 'n' Quiet), but AFAICT the documentation is wrong. In summary, you > are doomed. Well, with intel CPUs maybe ;) On PPC we can put some CPUs (at least the desktop ones and the 970, I don't know about POWER3/4/5) into SLEEP mode after flushing all caches & masking all IRQs to them, and get them out via an IPI, or we can mask EE as well and get them out via a soft reset if we have access to it. Ben.