From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756661AbZCDNhl (ORCPT ); Wed, 4 Mar 2009 08:37:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752912AbZCDNhP (ORCPT ); Wed, 4 Mar 2009 08:37:15 -0500 Received: from hera.kernel.org ([140.211.167.34]:48073 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751737AbZCDNhN (ORCPT ); Wed, 4 Mar 2009 08:37:13 -0500 Message-ID: <49AE83E6.4040608@kernel.org> Date: Wed, 04 Mar 2009 22:36:38 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.19 (X11/20081227) MIME-Version: 1.0 To: Alan Cox 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 References: <49ADE82D.40103@kernel.org> <49ADE9D3.6080000@kernel.org> <20090304095727.707ac18c@lxorguk.ukuu.org.uk> <49AE53B5.6000009@kernel.org> <20090304132945.2b242e63@lxorguk.ukuu.org.uk> In-Reply-To: <20090304132945.2b242e63@lxorguk.ukuu.org.uk> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Wed, 04 Mar 2009 13:36:42 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alan Cox wrote: >> x86 is blacklisting DAC for everything VIA. :-) > > I'd assume that comes from published docs given VIA actually publish > stuff if you ask nicely. Dunno the history but it's from the time before VIA begins publishing. It's probably worthwhile to refine the blacklisting. >> * MCP51 is a very old chipset at this point (it's circa 2005). Not >> many machine would be running with >4GB memory to begin with. >> >> * Given the above and scarcity of DAC on most end user machines >> (nothing on MCP51 does DAC by default), lack of reports isn't too >> surprising. >> >> * The board doesn't have a 64bit connector. It can't be dodgy >> connector and sil24 is known to behave well with DAC. The failure >> being specific to the particular machine doesn't seem likely. >> >> I'll ping nvidia about it but I think your bar is too high. > > I don't think wanting to see *two* examples is a high bar. I don't think it's an easy combination. Circa 2005 desktop machine with >4GB ram + DAC capable controller running Linux with owner who will report seemingly random data corruption which will end up in the correct hands and given that non-working DAC isn't too surprising of the machines of that time and isn't very likely caused by random component or connection failure, I think we'll be better off just blacklisting it. That said, I admit I'm more trigger happy with blacklists than some people (I think it's generally better to have working systems than chasing performance on not-so-common cases). Anyways, I pinged Peer Chen on the issue. Let's see whether he can confirm it. Thanks. -- tejun