linux-kernel - Re: [PATCH 3/6] pci, thunder: Add PCIe host controller devicetree bindings

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Message-ID: <CA+sq2CcXCVrk=fxH79n88ZJj5fBQmbyhnzj08qHNO8EmpZT1Yg@mail.gmail.com>
Date:	Thu, 25 Sep 2014 00:37:00 +0530
From:	Sunil Kovvuri <sunil.kovvuri@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	LAKML <linux-arm-kernel@...ts.infradead.org>,
	Robert Richter <rric@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-pci <linux-pci@...r.kernel.org>,
	Liviu Dudau <liviu.dudau@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Robert Richter <rrichter@...ium.com>,
	Sunil Goutham <sgoutham@...ium.com>
Subject: Re: [PATCH 3/6] pci, thunder: Add PCIe host controller devicetree bindings

On Thu, Sep 25, 2014 at 12:04 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Wednesday 24 September 2014 23:34:04 Sunil Kovvuri wrote:
>> On Wed, Sep 24, 2014 at 9:36 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> > On Wednesday 24 September 2014 17:37:45 Robert Richter wrote:
>> >> +               compatible = "cavium,thunder-pcie";
>> >> +               device_type = "pci";
>> >> +               msi-parent = <&its>;
>> >> +               bus-range = <0 255>;
>> >> +               #size-cells = <2>;
>> >> +               #address-cells = <3>;
>> >> +               reg = <0x8480 0x00000000 0 0x10000000>;  /* Configuration space */
>> >> +               ranges = <0x03000000 0x8010 0x00000000 0x8010 0x00000000 0x70 0x00000000>, /* mem ranges */
>> >> +                       <0x03000000 0x8300 0x00000000 0x8300 0x00000000 0x80 0x00000000>,
>> >> +                       <0x03000000 0x87e0 0x00000000 0x87e0 0x00000000 0x01 0x00000000>;
>> >> +        };
>> >
>> > If you claim the entire 0-255 bus range, I think you should also
>> > specify a domain, otherwise it's not predictable which domain you
>> > get.
>> >
>> > The interrupt-map and interrupt-map-mask properties are required for PCI,
>> > otherwise you can't do LSI interrupts.
>>
>> This PCI controller supports only MSIx interrupts which are edge triggered.
>
> Interesting, so it's not PCI compliant then? I assume this will be fixed
> in the production version of the silicon, right?
>
> Having no support for interrupts mean that the majority of PCI device drivers
> will fail.

This controller is for on-board PCI devices and all of them do support
MSIx interrupts.

>
>> > If your hardware can support it, you should also list I/O space and prefetchable
>> > memory spaces. Can you explain why you have multiple non-prefetchable ranges?
>>
>> Our hardware is an ECAM based host controller and doesn't support I/O
>> and prefetchable memory spaces.
>> All on-board PCI devices connected to this PCI controller have fixed resources
>> and doesn't have to be allocated/reassigned. Some of these devices are
>> SRIOV based.
>
> I think you need to mark the ones that are nonrelocatable with flag
> 0x80000000, otherwise the PCI core might decide to reassign them.

Is this flag part of DT pci node properties ?
I am using IORESOURCE_PCI_FIXED flag. Its there in other patches of
the same series.

>
>> Kernel's SRIOV (pci/iov.c) is expecting 'resource->parent' hierarchy
>> to be set, otherwise doesn't
>> enable SRIOV device. So, here multiple non-prefetchable ranges of root bus
>> aid in resource claiming and setting res->parent hierarchy.
>
> I don't understand. Isn't that just a bug in the code that you are working
> around with the DT. Have you tried fixing the code instead?

I tried but wasn't sure if its going to impact existing SRIOV devices.
Will have a deeper look again .

>
>> We do call "pci_claim_resource" in controller driver code.
>> "[PATCH 1/6] pci, thunder: Add support for Thunder PCIe host controller."
>
> My guess is that you are using the wrong interface here. Isn't the normal
> request_resource() in the host driver enough?

Isn't that host driver calls "request_resource" only for resources of root port.
i.e requesting from iomem_resource/ioport_resource. Here i am referring
to SRIOV devices enumerated upon scan of root port.

>
>         Arnd
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