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Message-ID: <54a3e2de1baf2aab893ab6370f8f6ec0a83c45db.camel@kernel.crashing.org>
Subject: Re: [PATCH 4/8] PCI: Add quirk to disable MSI support for Amazon's
 Annapurna Labs host bridge
From:   Benjamin Herrenschmidt <benh@kernel.crashing.org>
To:     "Chocron, Jonathan" <jonnyc@amazon.com>,
        "helgaas@kernel.org" <helgaas@kernel.org>
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Date:   Mon, 15 Jul 2019 08:54:00 +1000
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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.