Re: [PATCH 04/22] arm64: dts: qcom: hamoa: Reserve low IOVA range for Iris

[Dmitry Baryshkov]

On Mon, Aug 17, 2026 at 10:54:47AM +0100, Bryan O'Donoghue wrote:
> On 10/08/2026 14:47, Rob Herring wrote:
> > > > As per the reserved-memory.yaml schema document, the iommu-addresses
> > > > property for IOVA reservation into /reserved-memory is allowed — it's
> > > > documented for IOVA carveout reservations:
> > > > https://github.com/devicetree-org/dt-schema/blob/main/dtschema/
> > > > schemas/reserved-memory/reserved-memory.yaml#L56
> > > I think that is an entirely reasonable reading of the text
> > > 
> > > Quote:
> > > 
> > > "If no "reg" property is specified, the "iommu-addresses" property
> > >    defines carveout regions in the IOVA space for the given device. This
> > >    can be useful if a certain memory region should not be mapped through
> > >    the IOMMU."
> > > 
> > > Which is exactly what this series does. Excludes a specific IOVA range
> > > from being allocated for this device.
> > But if "iommu-addresses" is the only property of the reserved memory,
> > why put this property in reserved-memory rather than directly in the
> > device's node? I'm only questioning where is the right place to
> > describe a reserved IOVA.
> > 
> > Rob
> 
> Back from the eclipse, sorry for the delayed response.
> 
> Ah I get you.
> 
> Yes.
> 
> I take your point. This is a property of the node itself; the IOVA < 600MB
> only matters _if_ the venus or iris nodes are enabled - otherwise an IOVA <
> 600MB is perfectly fine.
> 
> So it follows its a property specific to this node not specific to the
> overall system.
> 
> Yep, I agree - its a device/node property, not a top-level property.

:-)

FWIW, I think it's a proper way to describe it too.

-- 
With best wishes
Dmitry