From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751691AbVJTBjw (ORCPT ); Wed, 19 Oct 2005 21:39:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751692AbVJTBjw (ORCPT ); Wed, 19 Oct 2005 21:39:52 -0400 Received: from gate.crashing.org ([63.228.1.57]:9190 "EHLO gate.crashing.org") by vger.kernel.org with ESMTP id S1751690AbVJTBjw (ORCPT ); Wed, 19 Oct 2005 21:39:52 -0400 Subject: Re: [BUG] PDC20268 crashing during DMA setup on stock Debian 2.6.12-1-powerpc From: Benjamin Herrenschmidt To: Kyle Moffett Cc: Andrew Morton , Bartlomiej Zolnierkiewicz , LKML Kernel In-Reply-To: <75FE9776-B88F-453E-9616-850097DB0138@mac.com> 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> <75FE9776-B88F-453E-9616-850097DB0138@mac.com> Content-Type: text/plain Date: Thu, 20 Oct 2005 11:36:44 +1000 Message-Id: <1129772205.7620.226.camel@gaston> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > 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? Maybe there is some fighting going on between ppc/pmac.c and that driver over the hwif's and you end up with mmio inadvertently set ? > > 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.