On 2024-05-31 10:32 am, Andre Przywara wrote:
On Fri, 31 May 2024 09:42:36 +0100
Robin Murphy <robin.murphy@xxxxxxx> 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.
