From owner-freebsd-arch@FreeBSD.ORG Tue Dec 30 14:23:55 2008 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E17421065670 for ; Tue, 30 Dec 2008 14:23:55 +0000 (UTC) (envelope-from Andre.Albsmeier@siemens.com) Received: from goliath.siemens.de (goliath.siemens.de [192.35.17.28]) by mx1.freebsd.org (Postfix) with ESMTP id 7397B8FC17 for ; Tue, 30 Dec 2008 14:23:55 +0000 (UTC) (envelope-from Andre.Albsmeier@siemens.com) Received: from mail2.siemens.de (localhost [127.0.0.1]) by goliath.siemens.de (8.12.11.20060308/8.12.11) with ESMTP id mBUDqG9T006455; Tue, 30 Dec 2008 14:52:16 +0100 Received: from curry.mchp.siemens.de (curry.mchp.siemens.de [139.25.40.130]) by mail2.siemens.de (8.12.11.20060308/8.12.11) with ESMTP id mBUDqGx2010546; Tue, 30 Dec 2008 14:52:16 +0100 Received: (from localhost) by curry.mchp.siemens.de (8.14.3/8.14.3) id mBUDqG4b001148; Date: Tue, 30 Dec 2008 14:52:16 +0100 From: Andre Albsmeier To: Jeff Roberson Message-ID: <20081230135216.GA2182@curry.mchp.siemens.de> References: <20081229212020.GA1809@curry.mchp.siemens.de> <20081229143221.X1076@desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081229143221.X1076@desktop> X-Echelon: X-Advice: Drop that crappy M$-Outlook, I'm tired of your viruses! User-Agent: Mutt/1.5.18 (2008-05-17) Cc: Andre Albsmeier , freebsd-arch@freebsd.org Subject: Re: Two drivers, one physical device: How to deal with that? X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 30 Dec 2008 14:23:56 -0000 On Mon, 29-Dec-2008 at 14:35:21 -1000, Jeff Roberson wrote: > On Mon, 29 Dec 2008, Andre Albsmeier wrote: > > > Hello, > > > > I have written a driver which attaches to the host bridge in > > order to periodically read the appropriate registers and > > inform the user about ECC errors (ECC-Monitor). No I have > > run across a mainboard where the host bridge is already > > taken by the agp driver. Of course, I can detach the agp > > driver and attach myself and everything is working but > > what is if someone does not want to loose the agp > > functionality? > > > > How does one deal with the case when two separate drivers > > have to access the same device (the host bridge in my case)? > > > > I assume, the correct way would be to join the AGP and > > ECC functionality in one driver but maybe there are other > > tricks I am not aware of? > > Well I don't think it would be correct to merge two conceptually seperate > drivers into one just to share the same device. It sounds like the right > solution is to make a generic layer the attaches to the host bridge and > arbitrates access to it. Then allow other device to find and communicate I see, yes, that sounds as a good idea. I also didn't like the idea of uniting the two functionalities. However, I assume my kernel programming skills are not good enough to implement something like this ;-) > with this generic layer. For the host bridge this doesn't have to be > particularly fancy. > > I am curious; how do you test the ECC functionality? Is there a way to > induce an error? The most common method is to lower the voltage and heat up the DIMMs. Some chips react rather quickly, others nearly have to be molten down ;-). Another possibility is to use a not too weak radioactive source (an old Radiomir watch is not enough) to bomb the RAMs with betas and gammas (this is of course not for everybody ;-)). But the easiest and safest way is to buy an Asus P5W board and enable the "Quick Boot" option in the BIOS. With this setting, lots of ECC-errors are produced in a short time. The rate goes down as the uptime rises. I don't know why this happens but I assume the chipset reads memory cells which have never been written to and therefore the data is inconsistent. As soon as you disable the "Quick Boot" option (which implies a memory writing test being performed by the BIOS) the errors go away. You can then even enable "Quick Boot" again, as long as you don't switch of the power... Thanks, -Andre -- GNU is Not Unix / Linux Is Not UniX