Re: [PATCH v2 1/9] dt-bindings: dma: nvidia,tegra186-gpc-dma: Add iommu-map property

Jon Hunter
2026-03-03T13:09:16Z

On 03/03/2026 08:40, Akhil R wrote:

...

>> Why is this flexible? If it is, means usually items are distinctive, so
>> I would expect defining/listing them. If they are not distinctive,
>> commit msg is incorrect. If the list is as simple as 1-to-1 channel
>> mapping, just add it in the description how they are ordered.
>
> Yes, it is a 1-to-1 channel mapping to an IOMMU ID. The intent of making
> it flexible is to allow non-consecutive IOMMU ID assignments as well.
> This is particularly needed in virtualised environments where the
> hypervisor may reserve certain stream IDs, and the guest VM can map only
> the permitted ones. Shall I add a description here mentioning this
> use-case?

Isn't this already handled by the 'dma-channel-mask' property? The
driver will skip over any channels that are not in specified by the mask.

Jon

--
nvpublic