Does Orin have bidirectional cache coherency between the CPU and integrated GPU (iGPU)? I understand that previous generations of Jetson do not, but I have seen several conflicting pieces of documentation for Orin specifically. Alternatively, does the iGPU cache pinned memory on Orin?
In the datasheet, the SCF (now Scalable Coherency Fabric) is described as providing “full-speed I/O coherence”, with no mention of applying only to the CPU’s caches. That kind of sounds like it works with all the caches in the SoC, but it’s not very clear.
CUDA for Tegra claims that there are no Jetson systems where the CPU can read from the iGPU’s cache, but maybe that hasn’t been updated for Orin?
I haven’t gotten around to running any speed tests myself, but RidgeRun’s tests seem to imply that the GPU is caching pinned memory, which I think can only happen if the CPU and GPU are fully bidirectionally cache coherent.