On 11/19/2013 05:03 AM, Hiroshi Doyu wrote: > Hi Thierry, > > Thierry Reding <thierry.reding@xxxxxxxxx> wrote @ Tue, 19 Nov 2013 11:25:07 +0100: > >> From earlier discussions I thought the goal was to actually defer this >> until all nodes referred to by the iommus property were actually >> registered. The above only checks that the phandles can be resolved to >> valid struct device_node:s. That doesn't mean that an actual IOMMU has >> been registered for it, only that the devices have been created. > > Currently "bus->iommu_ops" is set at the end of tegra_smmu_probe(). So > if "bus->iommu_ops" is set, it means that an iommu instance is > populated at that time. Yes, but that's the register bus, upon which the device is a client, not the bus upon which the device is a bus master. They aren't necessarily the same. There's no getting around the fact that, as Thierry said, you need to search for a registered IOMMU device for each phandle, and defer probe if any aren't registered yet. If we do that, then you shouldn't need to look at the value of dev->bus->iommu_ops at all; if all IOMMUs in the list were registered, then iommu_ops must have been set when (one of them) was registered, and if not, then it possibly wasn't, so defer probe. That way, this code won't have to change if the core IOMMU code gets extended to support multiple IOMMUs, devices mastering transactions onto buses other than their register bus, etc. -- 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
