Re: [PATCH] ARM: dts: ventana: fix eth1 pci dev node

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Tue, Mar 18, 2014 at 01:02:55PM -0700, Tim Harvey wrote:
> > Is this whole bridge/switch hierarchy binding documented somewhere
> > or is this just something that work for you?
> 
> I'm not sure where its 'best' documented, but it is the way the
> kernel works.

It is documented in the 'PCI Bus Binding to Open Firware'
publication from IEEE.

> >> +             pcie@0,0 {
> >> +                     /* 01:00.0 PCIe switch */
> >> +                     #address-cells = <3>;
> >> +                     #size-cells = <2>;
> >> +                     device_type = "pci";
> >> +                     reg = <0x0 0 0 0 0>;
> >> +
> >> +                     pcie@8,0 {
> >
> > What's the naming schema for all these pcie nodes?  Generally, we should
> > have the numbers encoded in the node name coming from the address cells
> > in 'reg' property.

The 'reg' property for PCI encodes the device and function number, and
the suffix in the device path is of the form @DEVICE,FUNCTION (see
2.2.1.3 of the spec)

So device=8, function=0 is @8,0 and reg = 0x4000.

> I was hoping there was a way to reference PCI nodes by BDF values as
> I'm simply trying to define a marvell,sky2 device at 08:00.0.  I found
> that the kernel's OF parsing code for PCI requires you to nest the
> nodes to match the bus hierarchy.  In order to map a dt node to a PCI
> device, the bus the device is on must have a dt node itself, which is
> what creates the need for the nesting.  Note that the bus topology
> here rc -> P2P bridge -> GigE.

Right, otherwise the kernel and firmware would have to agree on bus
numbering. With nesting it only has to agree on the device numbering,
which is a fixed property of PCI.

> >> +                             /* 02:08.0 PCIe switch port */
> >> +                             #address-cells = <3>;
> >> +                             #size-cells = <2>;
> >> +                             device_type = "pci";
> >> +                             reg = <0x4000 0 0 0 0>;
> >> +                             eth1: pcie@0,0 {
> >> +                                     /* 08:00.0 GigE */
> >> +                                     #address-cells = <3>;
> >> +                                     #size-cells = <2>;
> >> +                                     device_type = "pci";
> >> +                                     reg = <0x0 0 0 0 0>;
> >> +                                     compatible = "marvell,sky2";
> >> +                             };

Don't forget your interrupts and interrupt-map - every DT nodes need
to describe how its interrupts are routed.

Jason
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