On 11/19/2013 11:35 AM, Will Deacon wrote: > On Tue, Nov 19, 2013 at 09:40:54AM +0000, Hiroshi Doyu wrote: >> Grant Likely <grant.likely@xxxxxxxxxxxx> wrote @ Fri, 15 Nov 2013 08:06:27 +0100: >>> On Mon, 11 Nov 2013 10:47:23 +0100, Hiroshi Doyu <hdoyu@xxxxxxxxxx> wrote: >>>> 1, When a device is populated, it checks if that device is IOMMU'able >>>> or not. This is identified by "#stream-id-cells" in DT. If >>>> a device is normal(non IOMMU), a device is populated. If a device >>>> is IOMMU'able, it continues to be checked. > > [...] > >>>> I'm not so sure if this dependecy on "#stream-id-cells" is acceptable >>>> or not, but I haven't any better idea right now. >>> >>> It seems a little fragile to me too. I'd rather the IOMMU requirement be >>> described more explicitly. I don't see how this can work. Typically you find a property and then read the relevant #*-cells to determine the size. Having multiple cell properties is asking for errors. >> >> I think that Will Deacon can do better than I. > > I already commented briefly here: > > http://www.spinics.net/lists/devicetree/msg11513.html > > basically deferring to DT people :) > > Anyway, I'm happy to tighten up the IOMMU requirement description but > *not* at the expense of breaking what we currently have for the ARM SMMU, > which is being used by Calxeda. > > Adding Andreas and Rob for input on potential binding additions to the SMMU. The above proposal would be an incompatible change. However, I think we could still deal with a change in this binding at this stage. One way approach to handle this without changing the binding would be to scan the DT for all iommu's up front and create a list of all nodes and their iommu parent. The fact that the hierarchy is described in a way that doesn't fit Linux well is really a Linux implementation detail. If changing the binding, a simple approach would be to allow 'smmu-parent' to be a bus and/or device property and not just for chained iommu's. This could be a global or bus property that is inherited. Like interrupt-parent, you would have to deal with the parent being itself. Also, perhaps iommu-parent would be a better name. In any case, I'd like to see this all be a generic iommu binding. Rob -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
