Hi Will, On Fri, Sep 19, 2014 at 05:42:20PM +0100, Will Deacon wrote: > However, I thought about this a bit more and the coherency isn't necessarily > a global property of the SMMU. In reality, it is dependent on the IOTLBs in > use by the domain, so it's not going to be possible to report true here in > many cases. > > That means we'd need a way to say `this device is dma coherent when its > downstream IOMMU is enabled with IOMMU_CACHE mappings'. For the moment, > people will probably just add `dma-coherent' to the endpoint and dma-mapping > will request IOMMU_CACHE mappings regardless of the features advertised by > the IOMMU. In that case, it might make more sense to return `true' here as > we can always generated cacheable transactions from the SMMU. The > dma-coherent property on the device would then indicate whether those > transactions will snoop the CPU caches. Okay, when the SMMU can always generate cachable transactions it is surely fine to return true here. I'll change that before I add the patches to my tree. Joerg -- 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
