Re: [PATCH v7 0/3] Add support for PCI in AArch64

Sunil Kovvuri
2014-05-20T08:55:11Z

On Tue, May 20, 2014 at 2:14 PM, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
> On Tuesday 20 May 2014 09:52:33 Sunil Kovvuri wrote:
>> >> In sriov_enable() (drivers/pci/iov.c)
>> >>
>> >> 296 for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
>> >> 297 bars |= (1 << (i + PCI_IOV_RESOURCES));
>> >> 298 res = dev->resource + PCI_IOV_RESOURCES + i;
>> >> 299 if (res->parent)
>> >> 300 nres++;
>> >> 301 }
>> >> 302 if (nres != iov->nres) {
>> >> 303 dev_err(&dev->dev, "not enough MMIO resources for
>> >> SR-IOV\n");
>> >> 304 return -ENOMEM;
>> >> 305 }
>> >>
>> >> Here its checking if physical function's IOV resource has a parent or not.
>> >> Which is pci-pci bridge in this case. Otherwise it doesn't consider
>> >> that resource.
>> >>
>> >> Added below api to your patch.
>> >> This will try to claim a resource while creating a PCI device which
>> >> inturn sets 'res->parent'.
>> >
>> > This looks like the wrong approach. The PCI host controller should
>> > really have been registered with the root 'iomem_resource' during
>> > the probe of the host controller.
>> >
>> I didn't get this, if a SR-IOV device is connected to a PCI-PCI bridge
>> and inturn bridge connected to root port. Then the parent bus is not root,
>> but the bridge. The issue is either hierarchy should not be checked for
>> SR-IOV resources or someone should set the hierarchy (i.e parent resources).
>
> Ah, I misunderstood the problem, I thought the PCI core was complaining
> about lack of space in the resources, not about a lack of BARs.
>
> It seems there is code like yours in a couple of architectures, but they
> only claim the resources of bridges, not the actual devices as you
> seem to be doing. Can you check if the x86 version of
> pcibios_allocate_bus_resources() does the trick for you? Maybe we can
> turn that into a generic helper.
>
Thanks for the suggestion. Will try that once.
FYI, IA64 architecture does claim resources for devices as well.
arch/ia64/pci/pci.c 'pcibios_fixup_device_resources()'

Thanks,
Sunil.
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