From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH 4/8] PCI: Add quirk to disable MSI support for Amazon's Annapurna Labs host bridge Date: Mon, 15 Jul 2019 08:54:00 +1000 Message-ID: <54a3e2de1baf2aab893ab6370f8f6ec0a83c45db.camel@kernel.crashing.org> References: <20190710164519.17883-1-jonnyc@amazon.com> <20190710164519.17883-5-jonnyc@amazon.com> <20190712130419.GA46935@google.com> <2cac43401f0cf76acb645b98c6543204f12d5c05.camel@amazon.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <2cac43401f0cf76acb645b98c6543204f12d5c05.camel@amazon.com> Sender: linux-kernel-owner@vger.kernel.org To: "Chocron, Jonathan" , "helgaas@kernel.org" Cc: "linux-kernel@vger.kernel.org" , "robh+dt@kernel.org" , "jingoohan1@gmail.com" , "Woodhouse, David" , "Hanoch, Uri" , "devicetree@vger.kernel.org" , "lorenzo.pieralisi@arm.com" , "gustavo.pimentel@synopsys.com" , "Wasserstrom, Barak" , "Saidi, Ali" , "mark.rutland@arm.com" , "Hawa, Hanna" , "Shenhar, Talel" , "Krupnik, Ronen" , "linux-pci@vger.kernel.org" List-Id: devicetree@vger.kernel.org On Sun, 2019-07-14 at 15:09 +0000, Chocron, Jonathan wrote: > > s/host bridge/Root Port/, if I understand correctly. > > > > Ack. > > BTW, what is the main difference between the 2 terms, since they seem > to be (mistakenly?) used interchangeably? The host bridge is the parent of the root port. You can have several root ports under a host bridge in fact. They tend to be part of the same silicon and somewhat intimately linked but they are distinct logical entities. The root port appears as a PCIe p2p bridge sitting on the top level bus provided by the host bridge. The Host Bridge doesn't have to have a representation in config space (it sometimes does historically, but as a sibling of the devices on that top level bus. In PCIe land, these are chipset built-in devices). Ben.