[PATCH v2 2/3] iommu/dma: Use fast DMA domain lookup

On Fri, Sep 28, 2018 at 04:31:10PM +0100, Robin Murphy wrote:

The tricky part is how to reconcile that with those other drivers which 
want to do explicit IOMMU management with their own domain but still use 
the DMA API for coherency of the underlying memory. I do have a couple of 
half-formed ideas, but they're not quite there yet.

It think the only sensible answer is that they can't, and we'll need
coherency API in the iommu API (or augmenting it).  Which might be a
real possibility now that I'm almost done lifting the coherency
management to arch hooks instead of dma op methods.