Re: [PATCH v2 4/4] arm64: dts: broadcom: Add support for BCM2712

[Florian Fainelli]

On 5/16/24 01:36, Andrea della Porta wrote:
> On 09:14 Fri 10 May     , Florian Fainelli wrote:
> > On 5/10/24 07:35, Andrea della Porta wrote:
> >
> > This should be #size-cells = <2> to be future proof and support over 4GB of
> > DRAM, because the DDR controller and the memory map on that chip have been
> > designed with that requirement.
> >
> > > +
> > > +	interrupt-parent = <&gicv2>;
> > > +
> > > +	axi: axi {
> > > +		compatible = "simple-bus";
> > > +		#address-cells = <2>;
> > > +		#size-cells = <1>;
> > > +		ranges;
> >
> > The AXI peripheral window should be defined in the ranges property. The
> > aperture is from 0x10_0000_0000 to 0x10_3FFF_FFFF.
> >
> >  From that point on you can define all peripherals under the axi node to be
> > relative to that axi aperture, just like what you did for the legacy Pi
> > peripherals in the subsequent bus node.
>
> This doesn't seem to match with what I have here:
> - some axi peripherals goes beyond 0x10_3FFF_FFFF (e.g. the interrupt
>    controller is @0x107fff9000)

The interrupt controller (GIC) is technically its own dedicated bus to 
the CPU, that's why it is typically added to the root node.

> - downstream dts have that ranges going from 0x10 0x00000000 0x11 0x00000000,
>    so to span all the peripheral (included e.g. the above int controller)
> - another comment in downstream dts says: // 10_00000000-1x_xxxxxxxx = up to
>    64GB system RAM

Yes, up to 64GB of DRAM is correct.

> I'm a little confused here, of course we could also define multiple ranges
> but I don't really know what the boundaries are. Anyway, I would opt for the
> extended range (0x10 0x00000000 - 0x11 0x00000000) unless there is concern
> about it. Any thoughts?

A single range is fine with me, those sort of details should not matter.

> Many thanks,
> Andrea
>
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--
Florian

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