linux-kernel - Re: [PATCH 6/6] x86/PCI: quirk Thunderbolt PCI-to-PCI bridges

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Date:	Wed, 26 Jun 2013 16:56:03 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"Ronciak, John" <john.ronciak@...el.com>,
	"Penner, Miles J" <miles.j.penner@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 6/6] x86/PCI: quirk Thunderbolt PCI-to-PCI bridges

On Wed, Jun 26, 2013 at 3:55 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Wed, Jun 26, 2013 at 4:31 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>> On Wed, Jun 26, 2013 at 3:26 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>>> On Wed, Jun 26, 2013 at 3:18 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>>>> On Tue, Jun 25, 2013 at 10:22 AM, Mika Westerberg
>>>> <mika.westerberg@...ux.intel.com> wrote:
>>>>> Thunderbolt PCI-to-PCI bridges typically use BIOS "assisted" enumeration.
>>>>> This means that the BIOS will allocate bridge resources based on some
>>>>> assumptions of a maximum Thunderbolt chain. It also disables native PCIe
>>>>> hotplug of the root port where the Thunderbolt host router is connected.
>> ...
>> During acpi hotplug, firmare could do extra help for us like assign
>> some resources to pci device bars, so it is NOT "boot-time".
>
> Really?  How can firmware assign BARs at hotplug-time?  I mean,
> obviously firmware *can* write things to the BARs before giving the
> device to the OS, but how would it know what to write?

should be acpi code, or SMI code or even BMC firmware via sideband.

>  I assume the
> OS owns the address space, and it can change the upstream bridge
> windows or the BARs of another device on the bus at any time, subject
> to the OS's own issues as far as quiescing or unbinding drivers, etc.,
> but without coordinating with the BIOS.

for thunderbolt or dock with acpiphp, then all children devices/bridges should
not have drivers loaded yet.

Yinghai
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