From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.free-electrons.com ([94.23.35.102]:33363 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753343Ab3A2KB0 (ORCPT ); Tue, 29 Jan 2013 05:01:26 -0500 Date: Tue, 29 Jan 2013 11:01:19 +0100 From: Thomas Petazzoni To: Jason Gunthorpe Cc: Lior Amsalem , Andrew Lunn , Maen Suleiman , Russell King - ARM Linux , Jason Cooper , Arnd Bergmann , Stephen Warren , linux-pci@vger.kernel.org, Thierry Reding , Eran Ben-Avi , Nadav Haklai , Gregory Clement , Shadi Ammouri , Bjorn Helgaas , Tawfik Bayouk , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 07/27] PCI: Add software-emulated host bridge Message-ID: <20130129110119.07cb9ef3@skate> In-Reply-To: <20130128225105.GA21935@obsidianresearch.com> References: <1359399397-29729-1-git-send-email-thomas.petazzoni@free-electrons.com> <1359399397-29729-8-git-send-email-thomas.petazzoni@free-electrons.com> <201301282018.17714.arnd@arndb.de> <5106F5CB.8050304@wwwdotorg.org> <20130128220904.GA21446@obsidianresearch.com> <20130128231829.6b205c3c@skate> <20130128222348.GA21628@obsidianresearch.com> <20130128233048.2ab6a6d2@skate> <20130128225105.GA21935@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-pci-owner@vger.kernel.org List-ID: Dear Jason Gunthorpe, On Mon, 28 Jan 2013 15:51:05 -0700, Jason Gunthorpe wrote: > > > I'm refering to your earlier question about what PCI IDs to use for > > > the SW emulated devices. If there is no need for the host bridge then > > > you only need 1 PCI ID (for the root port bridge) and you can probably > > > fairly safely re-use the one in the Marvell config space of the HW. > > > > Ah, ok, I see. But isn't a host bridge needed to bind all the > > PCI-to-PCI bridges under a single bus, in order to get the global > > resource assignment I was referring to? > > The PCI-E spec requires it, but AFAIK it doesn't actually *do* > anything on Linux, and Linux doesn't require it. > > I thought Thierry did this experiment and decided it wasn't necessary: Could you detail what would be visible PCI bus topology if I remove the emulated PCI host bridge? (And keeping one PCI-to-PCI bridge per PCIe interface) ? I'm just trying to understand what it would look like, in terms of "lspci -t" output, because for now, it's not clear to me how everything would fit together with the emulated host bridge. Thanks, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com