Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757314AbYHaDxo (ORCPT ); Sat, 30 Aug 2008 23:53:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753808AbYHaDxf (ORCPT ); Sat, 30 Aug 2008 23:53:35 -0400 Received: from rv-out-0506.google.com ([209.85.198.230]:12159 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752164AbYHaDxd (ORCPT ); Sat, 30 Aug 2008 23:53:33 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=e+EsSWuqvhHo9FNJySAUZgQiWQKL3B4tY5VqsXRwBHW986Byb7DJuCNqFGGvYh7Ggq uu4MM24E8kOxc849yt7GspNIUquxCOZMCsZvJHRwCOAoLb2fisFGnmnl0IlnjZB12+bu mTLJ7UgJmc3AU2rLIUgT1Q3ujSIffevm76a44= Message-ID: <86802c440808302053r46256f68mf356797a259ad164@mail.gmail.com> Date: Sat, 30 Aug 2008 20:53:32 -0700 From: "Yinghai Lu" To: "Linus Torvalds" Subject: Re: Linux 2.6.27-rc5: System boot regression caused by commit a2bd7274b47124d2fc4dfdb8c0591f545ba749dd Cc: "Ivan Kokshaysky" , "Jordan Crouse" , "Rafael J. Wysocki" , "Linux Kernel Mailing List" , "Jeff Garzik" , "Tejun Heo" , "Ingo Molnar" , "David Witbrodt" , "Andrew Morton" , "Kernel Testers" In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <86802c440808301314t525d1b75r9afcc73857cf5c79@mail.gmail.com> <86802c440808301550s627dfcb0h7ff8971c8248703a@mail.gmail.com> <86802c440808301639j137ebef1r1ecadeebd351fc03@mail.gmail.com> <86802c440808301727k3e86c816j323eca0fb5e3f4fc@mail.gmail.com> <86802c440808301750w6655bbek557e6a23b8036654@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2629 Lines: 65 On Sat, Aug 30, 2008 at 8:00 PM, Linus Torvalds wrote: > > > On Sat, 30 Aug 2008, Yinghai Lu wrote: >> > >> > /* Don't touch classless devices or host bridges or ioapics. */ >> > if (class == PCI_CLASS_NOT_DEFINED || >> > class == PCI_CLASS_BRIDGE_HOST) >> > continue; >> > >> > >> > it skips the host bridge... >> >> what's story for not touching host bridges? > > Ahh. Exactly because of things like this. The hist bridge BAR's are often > special. > > That code comes from almost four years ago, the commit message was: > > Author: Maciej W. Rozycki > Date: Thu Dec 16 21:44:31 2004 -0800 > > [PATCH] PCI: Don't touch BARs of host bridges > > BARs of host bridges often have special meaning and AFAIK are best left > to be setup by the firmware or system-specific startup code and kept > intact by the generic resource handler. For example a couple of host > bridges used for MIPS processors interpret BARs as target-mode decoders > for accessing host memory by PCI masters (which is quite reasonable). > For them it's desirable to keep their decoded address range overlapping > with the host RAM for simplicity if nothing else (I can imagine running > out of address space with lots of memory and 32-bit PCI with no DAC > support in the participating devices). > > This is already the case with the i386 and ppc platform-specific PCI > resource allocators. Please consider the following change for the generic > allocator. Currently we have a pile of hacks implemented for host bridges > to be left untouched and I'd be pleased to remove them. > > From: "Maciej W. Rozycki" > Signed-off-by: Greg Kroah-Hartman > > and we've had other things where host bridges are special (ie iirc, if you > turn off PCI_COMMAND_MEM from a host bridge, it stops access to real RAM > from the CPU for some bridges - so you must never turn those things off or > you get a dead system). > > (But at least Intel host bridges will just ignore writes to the CMD > register, I think - you cannot turn MEM off). then 1. we should not probe them in probe.c 2. at least we should not try to request_resource for them in pcibios_resource_survey... just pretend that they are not existing. YH -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/