From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756000AbZCDKBe (ORCPT ); Wed, 4 Mar 2009 05:01:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753102AbZCDKB0 (ORCPT ); Wed, 4 Mar 2009 05:01:26 -0500 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:33346 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751084AbZCDKBZ (ORCPT ); Wed, 4 Mar 2009 05:01:25 -0500 Date: Wed, 4 Mar 2009 09:57:27 +0000 From: Alan Cox To: Tejun Heo Cc: Linux Kernel Mailing List , the arch/x86 maintainers , Thomas Gleixner , "H. Peter Anvin" , Ingo Molnar , pgnet.trash@gmail.com Subject: Re: [PATCH 2.6.29-rc7 2/2] x86: disallow DAC for MCP51 PCI bridge Message-ID: <20090304095727.707ac18c@lxorguk.ukuu.org.uk> In-Reply-To: <49ADE9D3.6080000@kernel.org> References: <49ADE82D.40103@kernel.org> <49ADE9D3.6080000@kernel.org> X-Mailer: Claws Mail 3.7.0 (GTK+ 2.14.7; x86_64-redhat-linux-gnu) Organization: None.. I'm free I'm free bwhahahahaha! Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 04 Mar 2009 11:39:15 +0900 Tejun Heo wrote: > MCP51 corrupts DAC transfers. Disallow it. Reported by pgnet on > bnc#463829. So you have a single piece of evidence as I read it - from a single board that represents system with a very common chipset and no supporting errata information from the vendor. That bug could easily be a faulty motherboard or dodgy connector or a specific hardware compatibility issue between two specific components. I don't think that can be considered sufficient evidence for adding sledgehammer sized workarounds that harm everyone elses performance and cripples such systems for certain kinds of work (eg video) Insufficient evidence and google searches and other bug searches don't seem to be turning up any parallel cases so for the moment At the very least someone needs to reproduce the hardware configuration and see the same problem, and then repeat with a different DAC enabled card. I don't believe this patch should go in ... yet. More information/testing is needed. Alan