[PATCH 5/5] arm64: dts: allwinner: h616: add IOMMU node

[Robin Murphy]

On 2024-05-31 10:32 am, Andre Przywara wrote:
> On Fri, 31 May 2024 09:42:36 +0100
> Robin Murphy <robin.murphy at arm.com> wrote:
> 
> Hi Robin,
> 
>> On 2024-05-31 12:38 am, Andre Przywara wrote:
>>> The Allwinner H616 contains a scatter-gather IOMMU connected to some
>>> video related devices. It's almost compatible to the one used in the H6,
>>> though with minor incompatibilities.
>>>
>>> Add the DT node describing its resources, so that devices like the video
>>> or display engine can connect to it.
>>
>> Without also describing those connections, though, having this node
>> enabled in the DT means the driver will just bind, block DMA, and
>> prevent those devices from working. That's probably not what you want.
> 
> The IOMMU manages the Display Engine (DE), the Deinterlacer (DI), the
> video engine (VE) and the 2D acceleration engine (G2D).
> None of those devices are supported for the H616 in mainline yet, but there
> are patches out there for the DE and VE, at least. Especially the video
> codecs benefit from scatter-gather, so with this patch they can make use
> of it from day one.

Oh, I see - I assumed that stuff like display was more exciting and 
likely to be supported already, so read "can connect to it" in the 
present tense. If it's a future "can use it as soon as they are also 
supported", then there's no concern, and indeed this is arguably the 
ideal order of doing things.

Cheers,
Robin.