On Wed, Jun 04, 2014 at 10:12:38PM +0100, Thierry Reding wrote: > On Fri, May 30, 2014 at 12:27:28PM +0100, Dave Martin wrote: > > On Fri, May 30, 2014 at 08:30:08AM +0100, Thierry Reding wrote: > [...] > > > Arnd, can you take another look at this binding and see if there's > > > anything else missing? If not I'll go through the document again and > > > update all #address-cells/#size-cells references with #iommu-cells as > > > appropriate and submit v3. > > > > How do you envisage propagation of the master ID bits downstream of the > > IOMMU would be described? > > > > We will definitely need a way to describe this for GICv3. How those > > values are propagated is likely to vary between related SoCs and doesn't > > feel like it should be baked into a driver, especially for the ARM SMMU > > which may get reused in radically different SoC families from different > > vendors. > > Well, we've had cases like these in the past (power sequences come to > mind). Some concepts are just too difficult or unwieldy to be put into > device tree. I think that this is one of them. > > > The most likely types of remapping are the adding of a base offset or > > some extra bits to the ID -- because not all MSIs to the GIC will > > necessarily pass through the IOMMU. It's also possible that we might > > see ID squashing or folding in some systems. > > It can easily be argued that if the algorithm used to remap the ID > varies, the compatibility of the device changes. Therefore I would > expect any variant of the GICv3 that deviates from the "standard" > mapping (if there is such a thing) to have its own compatible string. There is no standard mapping; it's a property defined at system integration time. I fully expect different SoCs to do different things here. Will -- 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
