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

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Date:	Tue, 20 May 2014 09:52:33 +0530
From:	Sunil Kovvuri <sunil.kovvuri@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Liviu Dudau <Liviu.Dudau@....com>,
	linux-pci <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Scott Lurndal <kdb@...ndal.org>,
	"yu.zhao@...el.com" <yu.zhao@...el.com>
Subject: Re: [PATCH v7 0/3] Add support for PCI in AArch64

On Mon, May 19, 2014 at 6:31 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Friday 16 May 2014 16:03:04 Sunil Kovvuri wrote:
>> When the SR-IOV capable device's driver tries to enable sriov
>> (pci_enable_sriov()) it fails to create/add PCI device for each
>> virtual function reporting  "not enough MMIO resources for SR-IOV".
>
> I assume you have checked that there is indeed enough MMIO space
> available, right?
>
Yes, i have checked for enough MMIO space multiple times.

>> 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.
>
>         Arnd
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).

Regards,
Sunil.
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