Different type iommus integrated in a SoC

[joro]

On Thu, Jun 03, 2021 at 01:05:43PM +0100, Robin Murphy wrote:
> Hooray! I've been forecasting this for years, but the cases we regularly hit
> with internal FPGA prototyping (nor the secret unused MMU-400 I found on
> RK3288) have never really been a strong enough argument to stand behind.
> 
> Based on what I remember from looking into this a few years ago, converting
> *most* of the API to per-device ops (now via dev->iommu) is trivial; the
> main challenge will be getting the per-device data bootstrapped in
> iommu_probe_device(), which would probably need to rely on the fwspec and/or
> list of registered IOMMU instances.
> 
> The other notable thing which will need to change is the domain allocation
> interface, but in practice I think everyone who calls iommu_domain_alloc()
> today is in fact doing so for a specific device, so I don't think it's as
> big a problem as it might first appear.

Yeah, I think for that we have to give up on the promise that a domain
can be assigned to _any_ device. But this promise doesn't even hold true
now when there are several IOMMU of the same type but with different
feature sets in a system.

So I happily review patches enabling the Multi-IOMMU SOCs :)

Regards,

	Joerg