From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f174.google.com ([209.85.217.174]:36368 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756229Ab2FVRNm convert rfc822-to-8bit (ORCPT ); Fri, 22 Jun 2012 13:13:42 -0400 Received: by lbbgm6 with SMTP id gm6so3848973lbb.19 for ; Fri, 22 Jun 2012 10:13:40 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <201206221653.31817.arnd@arndb.de> References: <4FDA2DDA.1030704@wwwdotorg.org> <201206221303.21985.arnd@arndb.de> <201206221653.31817.arnd@arndb.de> From: Bjorn Helgaas Date: Fri, 22 Jun 2012 11:13:19 -0600 Message-ID: Subject: Re: [PATCH v2 07/10] ARM: tegra: pcie: Add device tree support To: Arnd Bergmann Cc: Thierry Reding , Mitch Bradley , Stephen Warren , Russell King , linux-pci@vger.kernel.org, devicetree-discuss@lists.ozlabs.org, Rob Herring , Jesse Barnes , Colin Cross , linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Yinghai Lu Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-pci-owner@vger.kernel.org List-ID: On Fri, Jun 22, 2012 at 10:53 AM, Arnd Bergmann wrote: > On Friday 22 June 2012, Bjorn Helgaas wrote: >> The requirement (if there is one) isn't anything related to PC-ness. >> I just don't understand how things can actually work if two host >> bridges both claim the same bus number.  If we do a config read to >> that bus, both bridges should claim it and turn it into config cycles >> on their respective root buses, and we should get two responses.  I >> would expect the second response to cause an "unexpected response" >> machine check or similar. > > But each PCI domain has its own config space, so if you do a config > read for one bus, it's always relative to the domain. Oh, I see! I totally missed the fact that each host bridge was in its own domain. If each has its own domain, then the bus number aperture can certainly be [bus 00-ff] and there's no problem.