On Mon, Aug 08, 2022 at 03:48:02PM +0000, Hellstrom, Thomas wrote: > This whole thing looks a bit strange to me since with SWIOTLB actually > used for i915, the driver should malfunction anyway as it doesn't do > any dma_sync_sg_for_cpu() or dma_sync_sg_for_device(), Yeah, I can't actually see any syncs in i915. > and the driver > assumes all coherent dma. Is that SWIOTLB=force kernel option still > available? Yes, although it is (and always has been) lower case swiotlb for the option. > Also, correct me if I'm wrong, but the original driver segment size > appears to mean "the largest contiguous area that can be handled either > by the device or the dma mapping layer" rather than the total space > available for dma mappings? Not completely sure what > dma_max_mapping_size() is returning, though? dma_max_mapping_size is sort of both. It is is the largest contigous size, but we really should not go above that to avoid starvation.
