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    SubjectRe: [PATCH 1/2] PCI: make pci_claim_resource() work with conflict resources as appropriate
    From
    It was found that PCI quirks claim resources (by calling pci_claim_resource())
    *BEFORE* pcibios_fixup_bus() is called. In pcibios_fixup_bus(),
    pci_bus->resource[0] for the root bus DOES point to msc_io_resource. If PCI
    quirks do the resource claim after the arch-defined pcibios_fixup_bus() being
    called, then the problem with Malta goes away.

    So, it looks like 2 solutions out there:

    1) To manage the call sequence. This seems not a desired one as it affects other
    arches.

    2) To raise the start point of the system controller's io_resource in
    mips_pcibios_init() in arch/mips/mti-malta/malta-pci.c. This will place PCI
    quirks' resources at the same level of the system controller's resources.

    Ralf and Bjorn, which one sounds good to you?


    Deng-Cheng


    2011/7/30 Bjorn Helgaas <bhelgaas@google.com>:
    > On Fri, Jul 29, 2011 at 12:32 AM, Deng-Cheng Zhu
    > <dengcheng.zhu@gmail.com> wrote:
    >> I noticed that at 79896cf42f Linus changed the function from insert_resource()
    >> to request_resource() (and later evolved into request_resource_conflict()) and
    >> he explained the reason. So, in the NIC's case, the problem is that in
    >> pci_claim_resource() the function pci_find_parent_resource() returns the root
    >> (0x0-0xffffff) rather than the MSC PCI I/O (0x1000-0xffffff).
    >
    > This seems like the real problem: PCI has the wrong idea of the
    > resources available on bus 00.  The pci_bus->resource[0] for bus 00
    > points to ioport_resource (the default put there by pci_create_bus()),
    > when it should point to to msc_io_resource instead.
    >
    > Some architectures fill in the pci_bus->resource[] array directly for
    > host bridges (for examples, try 'grep -r "resource\[0\] = " arch/').
    > On x86 and ia64, we use pci_bus_remove_resources() and
    > pci_bus_add_resource(), and I'd prefer that style for new code because
    > it hides some ugly implementation details.
    >
    > I'm a little puzzled that we don't see this problem on more
    > architectures.  The grep above only found a few arches that update the
    > root bus resources.  I would expect most of the ones it didn't find to
    > be broken the same way Malta is.
    >
    > Bjorn
    >
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