On Sat, Nov 14, 2020 at 03:07:20PM -0500, Jonathan Marek wrote: > qcom's vulkan driver has nonCoherentAtomSize=1, and it looks like > dma_sync_single_for_cpu() does deal in some way with the partial cache line > case, although I'm not sure that means we can have a nonCoherentAtomSize=1. No, it doesn't. You need to ensure ownership is managed at dma_get_cache_alignment() granularity.