Re: [RESEND PATCH v2 4/5] drm/msm: add DRM_MSM_GEM_SYNC_CACHE for non-coherent cache maintenance

[Christoph Hellwig]

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.