From abb0deacb5a6713b918ac6395182cb27bb88be69 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 19 Dec 2016 12:43:45 +0000 Subject: [PATCH] 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: Juergen Gross Tested-by: Juergen Gross Fixes: 871dfbd67d4e ("drm/i915: Allow compaction upto SWIOTLB max segment size") Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Imre Deak Cc: Link: http://patchwork.freedesktop.org/patch/msgid/20161219124346.550-1-chris@chris-wilson.co.uk Reviewed-by: Daniel Vetter (cherry picked from commit d766ef53006c2c38a7fe2bef0904105a793383f2) Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/i915_gem.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 3b6eb651d88a..c6f80bc3b7bc 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -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) - goto err_pages; + 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); -- 2.30.2