| Message ID | 20200706224308.22636-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: Update dma-attributes for our sg DMA | expand |
On 06/07/2020 23:43, Chris Wilson wrote: > Looking through the attributes for DMA mappings, it appears that by > default dma_map_sg will try and create a kernel accessible map of the > page. We never access this, as we either have a struct page already or > an iomap, so we can request that the dma mapper does not create one. > Without a kernel map in place, one presumes the rest of the memory > control attributes do not apply. We also explicitly control the caches > around the mappings, so we can ask it not to bother synchronising itself. > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Matthew Auld <matthew.auld@intel.com> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index cb43381b0d37..c5ee1567f3d1 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -31,6 +31,8 @@ int i915_gem_gtt_prepare_pages(struct drm_i915_gem_object *obj, if (dma_map_sg_attrs(&obj->base.dev->pdev->dev, pages->sgl, pages->nents, PCI_DMA_BIDIRECTIONAL, + DMA_ATTR_SKIP_CPU_SYNC | + DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_NO_WARN)) return 0;
Looking through the attributes for DMA mappings, it appears that by default dma_map_sg will try and create a kernel accessible map of the page. We never access this, as we either have a struct page already or an iomap, so we can request that the dma mapper does not create one. Without a kernel map in place, one presumes the rest of the memory control attributes do not apply. We also explicitly control the caches around the mappings, so we can ask it not to bother synchronising itself. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Matthew Auld <matthew.auld@intel.com> --- drivers/gpu/drm/i915/i915_gem_gtt.c | 2 ++ 1 file changed, 2 insertions(+)