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

[Rob Clark]

On Mon, Nov 16, 2020 at 9:33 AM Christoph Hellwig <hch@xxxxxx> wrote:
>
> 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.

my guess is nonCoherentAtomSize=1 only works in the case of cache
coherent buffers

BR,
-R