On Mon, Dec 19, 2016 at 12:43:45PM +0000, Chris Wilson wrote:
> 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 <jgross@xxxxxxxx>
> Fixes: 871dfbd67d4e ("drm/i915: Allow compaction upto SWIOTLB max segment size")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
> Cc: <drm-intel-fixes@xxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Feels a bit funny to call swiotlb_* functions, I'd kinda assume that we
could somehow figure this out from the dma limits instead of leaking
through the dma api abstraction. But that's already there, so meh.
-Daniel
> ---
> 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 412f3513f269..4e263df2afc3 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2326,7 +2326,8 @@ 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;
> @@ -2352,7 +2353,7 @@ 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);
> @@ -2411,8 +2412,25 @@ 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);
> --
> 2.11.0
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
