From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from moutng.kundenserver.de ([212.227.17.9]:51001 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756014Ab2FVQxs (ORCPT ); Fri, 22 Jun 2012 12:53:48 -0400 From: Arnd Bergmann To: Bjorn Helgaas Subject: Re: [PATCH v2 07/10] ARM: tegra: pcie: Add device tree support Date: Fri, 22 Jun 2012 16:53:31 +0000 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 References: <4FDA2DDA.1030704@wwwdotorg.org> <201206221303.21985.arnd@arndb.de> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Message-Id: <201206221653.31817.arnd@arndb.de> Sender: linux-pci-owner@vger.kernel.org List-ID: 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. The part that is specific to PCs is that they don't have PCI domains normally. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v2 07/10] ARM: tegra: pcie: Add device tree support Date: Fri, 22 Jun 2012 16:53:31 +0000 Message-ID: <201206221653.31817.arnd@arndb.de> References: <4FDA2DDA.1030704@wwwdotorg.org> <201206221303.21985.arnd@arndb.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bjorn Helgaas Cc: Thierry Reding , Mitch Bradley , Stephen Warren , Russell King , linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Rob Herring , Jesse Barnes , Colin Cross , linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Yinghai Lu List-Id: linux-tegra@vger.kernel.org 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. The part that is specific to PCs is that they don't have PCI domains normally. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Fri, 22 Jun 2012 16:53:31 +0000 Subject: [PATCH v2 07/10] ARM: tegra: pcie: Add device tree support In-Reply-To: References: <4FDA2DDA.1030704@wwwdotorg.org> <201206221303.21985.arnd@arndb.de> Message-ID: <201206221653.31817.arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. The part that is specific to PCs is that they don't have PCI domains normally. Arnd