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 21:08:34 +0000 Message-ID: <201206222108.35094.arnd@arndb.de> References: <4FDA2DDA.1030704@wwwdotorg.org> <201206221653.31817.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: > > 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. Right. On my side, it took me a while to figure out that you can actually have multiple root ports in one domain ;-) Arnd