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Commit abb0deac authored by Chris Wilson's avatar Chris Wilson Committed by Jani Nikula
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drm/i915: Fallback to single PAGE_SIZE segments for DMA remapping 



If we at first do not succeed with attempting to remap our physical
pages using a coalesced scattergather list, try again with one
scattergather entry per page. This should help with swiotlb as it uses a
limited buffer size and only searches for contiguous chunks within its
buffer aligned up to the next boundary - i.e. we may prematurely cause a
failure as we are unable to utilize the unused space between large
chunks and trigger an error such as:

	 i915 0000:00:02.0: swiotlb buffer is full (sz: 1630208 bytes)

Reported-by: default avatarJuergen Gross <jgross@suse.com>
Tested-by: default avatarJuergen Gross <jgross@suse.com>
Fixes: 871dfbd6 ("drm/i915: Allow compaction upto SWIOTLB max segment size")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: <drm-intel-fixes@lists.freedesktop.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20161219124346.550-1-chris@chris-wilson.co.uk


Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit d766ef53)
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
parent d8953c83

drivers/gpu/drm/i915/i915_gem.c

+22 −4
Original line number Diff line number Diff line
@@ -2342,7 +2342,8 @@ static struct sg_table * 
i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)

{

	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);

	int page_count, i;

	const unsigned long page_count = obj->base.size / PAGE_SIZE;

	unsigned long i;

	struct address_space *mapping;

	struct sg_table *st;

	struct scatterlist *sg;
@@ -2368,7 +2369,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) 
	if (st == NULL)

		return ERR_PTR(-ENOMEM);



	page_count = obj->base.size / PAGE_SIZE;

rebuild_st:

	if (sg_alloc_table(st, page_count, GFP_KERNEL)) {

		kfree(st);

		return ERR_PTR(-ENOMEM);
@@ -2427,8 +2428,25 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) 
	i915_sg_trim(st);



	ret = i915_gem_gtt_prepare_pages(obj, st);

	if (ret)

	if (ret) {

		/* DMA remapping failed? One possible cause is that

		 * it could not reserve enough large entries, asking

		 * for PAGE_SIZE chunks instead may be helpful.

		 */

		if (max_segment > PAGE_SIZE) {

			for_each_sgt_page(page, sgt_iter, st)

				put_page(page);

			sg_free_table(st);



			max_segment = PAGE_SIZE;

			goto rebuild_st;

		} else {

			dev_warn(&dev_priv->drm.pdev->dev,

				 "Failed to DMA remap %lu pages\n",

				 page_count);

			goto err_pages;

		}

	}



	if (i915_gem_object_needs_bit17_swizzle(obj))

		i915_gem_object_do_bit_17_swizzle(obj, st);