From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751626AbVJSXOc (ORCPT ); Wed, 19 Oct 2005 19:14:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751628AbVJSXOc (ORCPT ); Wed, 19 Oct 2005 19:14:32 -0400 Received: from smtpout.mac.com ([17.250.248.97]:1482 "EHLO smtpout.mac.com") by vger.kernel.org with ESMTP id S1751624AbVJSXOb (ORCPT ); Wed, 19 Oct 2005 19:14:31 -0400 In-Reply-To: <1129760024.7620.219.camel@gaston> References: <20051017005855.132266ac.akpm@osdl.org> <1129536482.7620.76.camel@gaston> <6DFB5723-0042-46FE-811F-BF372B068014@mac.com> <204AB9A8-7701-402F-A6B9-DF455DAA2A3F@mac.com> <1129760024.7620.219.camel@gaston> Mime-Version: 1.0 (Apple Message framework v734) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <75FE9776-B88F-453E-9616-850097DB0138@mac.com> Cc: Andrew Morton , Bartlomiej Zolnierkiewicz , LKML Kernel Content-Transfer-Encoding: 7bit From: Kyle Moffett Subject: Re: [BUG] PDC20268 crashing during DMA setup on stock Debian 2.6.12-1-powerpc Date: Wed, 19 Oct 2005 19:14:19 -0400 To: Benjamin Herrenschmidt X-Mailer: Apple Mail (2.734) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Oct 19, 2005, at 18:13:44, Benjamin Herrenschmidt wrote: > On Wed, 2005-10-19 at 13:48 -0400, Kyle Moffett wrote: > >> Do you have any other ideas WRT this bug? I've been browsing >> around in the code a bit, and I plan to try diffing my 2.6.8.1 >> version of the files against the latest Debian to see what >> changed, although I suspect it will be a relatively fat hunk of >> changes. Thanks for your >> help! >> > > Nope. The lspci output looks perfectly normal. I looks like a > mixture of issues with BM DMA being disabled for a reason I haven't > figured out and then the code crashing because it doesn't like BM- > DMA being disabled ... BusMaster-DMA definitely should be enabled on that card. After a lot of looking through icky IDE code, I've determined that the reason for the crash is that if there is a "mate", or another IDE bus on the same card, then hwif->dma_master is set to hwif->mate->dma_base on the secondary channel. Since DMA explicitly wasn't enabled on the primary channel, hwif->dma_master on the secondary is 0 even though dma is enabled, and therefore we hit that BUG(). Therefore it seems that the only issue is ide_get_or_set_dma_base is returning 0 when it should return a valid DMA base. In that function, the only ways that function can even theoretically return 0 without printing any weird error messages is "if (hwif->mmio)" or "if (hwif->mate && hwif->mate->dma_base)". The latter can't happen before hwif->mate is set up (since the problem is while initializing the primary). Could hwif->mmio be nonzero somehow? The only drivers that seem to set it are pci/sgiioc4, pci/siimage, ppc/pmac, and a couple misc arch drivers. I see a couple theoretical possibilities: * hwif->mate and hwif->mate->dma_base are set for the primary while still initializing it (before any secondary is set up. * hwif->mmio is set somehow even though it shouldn't be, is the value ever pre-initialized to 0? > Again, best is you pour printk's all over setup-pci.c and ide-dma.c > to figure out what's going on... I wish I could but the machine is remote and in-production, so it's hard to have time to do much with it. I'm trying as best I can to walk through the sources by hand, specifically with regards to changes between the two. I'm hoping I can come up with a good enough guess by Thanksgiving, so that when I have a week near the server to test things out I can make significant progress. Cheers, Kyle Moffett -- I have yet to see any problem, however complicated, which, when you looked at it in the right way, did not become still more complicated. -- Poul Anderson