linux-kernel - Re: [PATCH v1] PCI: Make PCI_SCAN_ALL_PCIE_DEVS work for Root as well as Downstream Ports

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Message-ID: <87k1y33xwg.fsf@concordia.ellerman.id.au>
Date:   Mon, 04 Dec 2017 15:44:15 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Christian Zigotzky <chzigotzky@...osoft.de>
Subject: Re: [PATCH v1] PCI: Make PCI_SCAN_ALL_PCIE_DEVS work for Root as well as Downstream Ports

Bjorn Helgaas <helgaas@...nel.org> writes:

> On Fri, Dec 01, 2017 at 06:27:10PM -0600, Bjorn Helgaas wrote:
>> From: Bjorn Helgaas <bhelgaas@...gle.com>
>> 
>> PCIe Downstream Ports normally have only a Device 0 below them.  To
>> optimize enumeration, we don't scan for other devices *unless* the
>> PCI_SCAN_ALL_PCIE_DEVS flag is set by set by quirks or the
>> "pci=pcie_scan_all" kernel parameter.
>> 
>> Previously PCI_SCAN_ALL_PCIE_DEVS only affected scanning below Switch
>> Downstream Ports, not Root Ports.
>> 
>> But the "Nemo" system, also known as the AmigaOne X1000, has a PA Semi Root
>> Port whose link leads to an AMD/ATI SB600 South Bridge.  The Root Port is a
>> PCIe device, of course, but the SB600 contains only conventional PCI
>> devices with no visible PCIe port.
>> 
>> Simplify and restructure only_one_child() so that we scan for all possible
>> devices below Root Ports as well as Switch Downstream Ports when
>> PCI_SCAN_ALL_PCIE_DEVS is set.
>> 
>> This is enough to make Nemo work with "pci=pcie_scan_all".  We would also
>> like to add a quirk to set PCI_SCAN_ALL_PCIE_DEVS automatically on Nemo so
>> users wouldn't have to use the "pci=pcie_scan_all" parameter, but we don't
>> have that yet.
>> 
>> Link: https://lkml.kernel.org/r/CAErSpo55Q8Q=5p6_+uu7ahnw+53ibVDNRXxrzRV9QnUr_9EUfw@mail.gmail.com
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=198057
>> Reported-and-Tested-by: Christian Zigotzky <chzigotzky@...osoft.de>
>> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
>
> Applied to pci/enumeration for v4.16.

Thanks Bjorn.

cheers