Re: [PATCH v2] drm/i915/dmabuf: avoid global wbinvd on dma-buf import

"Prabhakaran, Krishna" <[email protected]>
Newsgroups org.freedesktop.lists.intel-gfx,org.freedesktop.lists.dri-devel
Message-ID <IA1PR11MB641816D15A8673AFD5667E22FAA42@IA1PR11MB6418.namprd11.prod.outlook.com>
> I think we can bump this now for dg2? I think we treat dgfx as always
> coherent with system memory. So maybe s/IS_DG1/IS_DGFX/ in a separate
> patch? Pretty sure the rest of the driver is the same.

Agreed. I'll send that as a separate patch, "drm/i915/dmabuf: skip
acquire flush on all discrete GPUs", with you as Suggested-by.

> Do we need the flush under the else here? If it's not placed in system
> memory what is this flushing, from i915 pov?

Right. i915_gem_dmabuf_attach() migrates the exporter to SMEM
(INTEL_REGION_SMEM) before get_pages() runs, so dma_obj is always
struct-page backed here and the else was effectively dead code; a wbinvd
of device memory doesn't make sense from i915's point of view. Dropped
in v3 -- the own-dma-buf branch is now just:

	drm_clflush_sg(dma_obj->mm.pages);

Thanks
Krishna
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