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drm/i915/dmabuf: drop the flush on discrete

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We were overzealous here; even though discrete is non-LLC, it should
still be always coherent.

v2(Thomas & Daniel)
  - Be extra cautious and limit to DG1
  - Add some more commentary

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211029122137.3484203-1-matthew.auld@intel.com
This commit is contained in:
Matthew Auld 2021-10-29 13:21:37 +01:00
parent 068b1bd092
commit 57d9898bee
1 changed files with 13 additions and 2 deletions
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15
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
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@ -250,8 +250,19 @@ static int i915_gem_object_get_pages_dmabuf(struct drm_i915_gem_object *obj)
if (IS_ERR(pages))
return PTR_ERR(pages);
/* XXX: consider doing a vmap flush or something */
if (!HAS_LLC(i915) || i915_gem_object_can_bypass_llc(obj))
/*
* DG1 is special here since it still snoops transactions even with
* CACHE_NONE. This is not the case with other HAS_SNOOP platforms. We
* might need to revisit this as we add new discrete platforms.
*
* XXX: Consider doing a vmap flush or something, where possible.
* Currently we just do a heavy handed wbinvd_on_all_cpus() here since
* the underlying sg_table might not even point to struct pages, so we
* can't just call drm_clflush_sg or similar, like we do elsewhere in
* the driver.
*/
if (i915_gem_object_can_bypass_llc(obj) ||
(!HAS_LLC(i915) && !IS_DG1(i915)))
wbinvd_on_all_cpus();
sg_page_sizes = i915_sg_dma_sizes(pages->sgl);