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    SubjectRe: [PATCH v2 1/8] x86/PCI: prevent re-allocation of already existing bridge and ROM resources
    On Wed, Jul 3, 2013 at 8:04 AM, Mika Westerberg
    <mika.westerberg@linux.intel.com> wrote:
    > In hotplug case (especially with Thunderbolt enabled systems) we might need
    > to call pcibios_resource_survey_bus() several times for a bus. The function
    > ends up calling pci_claim_resource() for each bridge resource that then
    > fails claiming that the resource exists already (which it does). Once this
    > happens the resource is invalidated thus preventing devices behind the
    > bridge to allocate their resources.
    >
    > To fix this we do what has been done in pcibios_allocate_dev_resources()
    > and check 'parent' of the given resource. If it is non-NULL it means that
    > the resource has been allocated already and we can skip it. We do the same
    > for ROM resources as well.
    >
    > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

    This looks reasonable to me.

    However, the use of "r->parent" to determine whether the resource is
    already allocated is nothing specific to x86. So I think we might be
    missing an opportunity to make this more consistent across
    architectures. I looked at other callers of pci_claim_resource() for
    bridge and ROM resources, and it looks like we might be able to make
    similar changes in:

    frv pcibios_allocate_bus_resources()
    ia64 pcibios_fixup_resources() (via pcibios_fixup_bridge_resources())
    mn10300 pcibios_allocate_bus_resources()
    mn10300 pcibios_assign_resources() (ROM)
    mn10300 pcibios_fixup_device_resources()
    parisc lba_fixup_bus()

    I really hate the idea of fixing something for x86 but not for other
    arches, so maybe somebody could take a deeper look at this and see if
    it would make sense to change the other arches, too.

    Bjorn

    > ---
    > arch/x86/pci/i386.c | 4 ++++
    > 1 file changed, 4 insertions(+)
    >
    > diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
    > index 94919e3..db6b1ab 100644
    > --- a/arch/x86/pci/i386.c
    > +++ b/arch/x86/pci/i386.c
    > @@ -210,6 +210,8 @@ static void pcibios_allocate_bridge_resources(struct pci_dev *dev)
    > r = &dev->resource[idx];
    > if (!r->flags)
    > continue;
    > + if (r->parent) /* Already allocated */
    > + continue;
    > if (!r->start || pci_claim_resource(dev, idx) < 0) {
    > /*
    > * Something is wrong with the region.
    > @@ -318,6 +320,8 @@ static void pcibios_allocate_dev_rom_resource(struct pci_dev *dev)
    > r = &dev->resource[PCI_ROM_RESOURCE];
    > if (!r->flags || !r->start)
    > return;
    > + if (r->parent) /* Already allocated */
    > + return;
    >
    > if (pci_claim_resource(dev, PCI_ROM_RESOURCE) < 0) {
    > r->end -= r->start;
    > --
    > 1.8.3.2
    >


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