Thierry Reding <thierry.reding@xxxxxxxxx> wrote @ Fri, 25 Oct 2013 09:56:55 +0200: > I suspect that there will be enough differences between the various > IOMMU implementations that we won't be able to have a unified binding > (especially for how to associate devices with a particular virtual > address space), but perhaps that could be solved with something like an > .of_xlate() that IOMMU drivers implement, much like we've done with most > other subsystems too. > > The binding for Tegra's IOMMU currently only uses the HW IDs (or a mask) > to put a device into a given address space, but I think that could be > easily extended to something like: > > memory-clients = <&iommu MASK>; > > Or similar. If other information is required, we could encode that into > a multi-cell specifier. Perhaps we could even leave away the phandle > since typically there will only be a single IOMMU in the system? > > Does that sound reasonable? Hiroshi is much more familiar with IOMMUs, > so I'd like to get his opinion on the above as well. I think that the above may be possible, but I'd like to listen from other IOMMU SOC maintainers. A brief explanation for "memory-clients": In tegra, every H/W has its own memory-client ID, and it can be associated to any address spaces. The above "memory-cilents" is used to indicate which ID a device has in DT. If the other SOC IOMMUs need this kind of "memory-clients", this would be standarized. Any comment? At least arm-smmu seems to have the following. multiple IOMMUs can be handled with this. - smmu-parent : When multiple SMMUs are chained together, this property can be used to provide a phandle to the parent SMMU (that is the next SMMU on the path going from the mmu-masters towards memory) node for this SMMU. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html