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

[Vikash Garodia <vikash.garodia@oss.qualcomm.com>]

On 8/18/2026 1:21 PM, Vikash Garodia wrote:
> 
> On 8/18/2026 11:53 AM, Dmitry Baryshkov wrote:
>> 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.
>>
> 
>  From my readings, a node defined under reserved-memory can have other 
> properties like "reg" alongwith "iommu-addresses". Are we saying when 
> *only* "iommu-addresses" is there, then move to the device and when 
> other property is there, then move to individual device ?

sorry, typo. Pls read the last few words as ".., then keep under 
reserve-memory ?"

> 
> Again the device may have the "reg" property already, in such case, 
> moving the iommu-addresses + reg in corresponding device might not be 
> feasible.
> 
> Regards,
> Vikash