Am 10.01.19 um 14:31 schrieb Bas Vermeulen: On Thu, Jan 10, 2019 at 11:59 AM Christian König <ckoenig.leichtzumer...@gmail.com<mailto:ckoenig.leichtzumer...@gmail.com>> wrote: The PCI Express controller as instantiated on this chip does not support hardware coherency. All incoming PCI Express transactions are made non IO-coherent.
Would AMDGPU still work with that PCI Express controller, or is this a show-stopper? I'm really wondering what this comment in the documentation means. As far as I know PCIe doesn't support cache coherency in the downstream and supporting it in the up stream is a must have. So what exactly is meant here with IO-coherent? I believe IO Coherent means that when PCIe writes something to CPU memory, the caches are flushed or updated (or in this case they aren't). I found https://community.arm.com/processors/b/blog/posts/extended-system-coherency---part-1---cache-coherency-fundamentals with this explanation. Yeah, but as I said this upstream memory coherency is mandatory for PCIe. When a controller doesn't have that it can't call itself a PCIe controller. The spec is pretty clear about that :) And to answer the original question: Yes, that would be a totally show-stopper. Regards, Christian. Regards, Bas Vermeulen
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