From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759534AbYHNUC6 (ORCPT ); Thu, 14 Aug 2008 16:02:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753993AbYHNUCt (ORCPT ); Thu, 14 Aug 2008 16:02:49 -0400 Received: from 8bytes.org ([88.198.83.132]:59951 "EHLO 8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753743AbYHNUCs (ORCPT ); Thu, 14 Aug 2008 16:02:48 -0400 Date: Thu, 14 Aug 2008 22:02:47 +0200 From: Joerg Roedel To: Ingo Oeser Cc: Joerg Roedel , mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org Subject: Re: [PATCH 1/4] AMD IOMMU: use status bit instead of memory write-back for completion wait Message-ID: <20080814200247.GA26988@8bytes.org> References: <1218736518-25301-1-git-send-email-joerg.roedel@amd.com> <1218736518-25301-2-git-send-email-joerg.roedel@amd.com> <200808142035.32422.ioe-lkml@rameria.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200808142035.32422.ioe-lkml@rameria.de> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 14, 2008 at 08:35:30PM +0200, Ingo Oeser wrote: > Hi Joerg, > > On Thursday 14 August 2008, Joerg Roedel wrote: > > diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c > > index 22d7d05..028e945 100644 > > --- a/arch/x86/kernel/amd_iommu.c > > +++ b/arch/x86/kernel/amd_iommu.c > > @@ -122,9 +119,15 @@ static int iommu_completion_wait(struct amd_iommu *iommu) > > > > while (!ready && (i < EXIT_LOOP_COUNT)) { > > ++i; > > - cpu_relax(); > > Could you elaborate, why you had to remove this? > > Busy waiting loops should always do cpu_relay() > to reduce heat procution and power consumption while idle. I removed it because its not idling anymore in that loop imho. It reads data from MMIO and does a small calculation with it. Joerg