Re: [Qemu-devel] [PATCH] hw/arm/virt: Fix address in PCIe device tree node's unit name

[Alexander Gordeev]

On Fri, Oct 23, 2015 at 03:18:34PM +0100, Peter Maydell wrote:
> On 21 October 2015 at 23:01, Alexander Gordeev <address@hidden> wrote:
> > On Wed, Oct 21, 2015 at 10:26:27PM +0100, Peter Maydell wrote:
> >> On 21 October 2015 at 21:43, Alexander Gordeev <address@hidden> wrote:
> >> > PCIe device tree unit name is address@hidden - which denotes
> >> > IO space base address. However, the corresponding node's
> >> > "reg" property points to PCI configuration space base address
> >> > 0x3f000000.
> >> >
> >> > Set the unit name to address@hidden which is not only correct,
> >> > but also conforms to Open Firmware (IEEE 1275).
> >>
> >> Nothing should actually care about the address in the
> >> nodename, though, right -- it's just for human readability
> >> and debugging (and guests will be looking at the regs
> >> etc properties of the node to figure out where it is)?
> >> Or have I misunderstood this and there's an actual visible
> >> consequence to this bug?
> >
> > I do not think there are actual consequences out there.
> > It is just misleading and does not honour the standard.
> 
> Do you have a more precise reference than just "IEEE 1275" ?
> I found the bit that says node names should be address@hidden,
> and unit address is the "text representation of the physical address
> of the device", but it seems to me that our current choice of
> "the lowest physical address where you can find any part of this
> device" is closer to that than deciding that we should use the
> address of the config space window instead.

No, I do not have it other than indirectly (though I probably could locate it).
I relied on Linux Documentation/devicetree/bindings/pci/host-generic-pci.txt
instead:

- reg            : The Configuration Space base address and size, as accessed
                   from the parent bus. [...]

IMHO it perfectly make sense - either io or memory mapped regions are rather
used to map attached devices, while the unit name for a host bridge is implied
to "address" the bridge itself, isn't it?

Thanks!

> thanks
> -- PMM

-- 
Regards,
Alexander Gordeev
address@hidden