drm/i915: Fix DMA mapped scatterlist lookup

As the previous patch fixed the places where we walk the whole scatterlist
for DMA addresses, this patch fixes the random lookup functionality.

To achieve this we have to add a second lookup iterator and add a
i915_gem_object_get_sg_dma helper, to be used analoguous to existing
i915_gem_object_get_sg_dma. Therefore two lookup caches are maintained per
object and they are flushed at the same point for simplicity. (Strictly
speaking the DMA cache should be flushed from i915_gem_gtt_finish_pages,
but today this conincides with unsetting of the pages in general.)

Partial VMA view is then fixed to use the new DMA lookup and properly
query sg length.

v2:
 * Checkpatch.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Tom Murphy <murphyt7@tcd.ie>
Cc: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20201006092508.1064287-2-tvrtko.ursulin@linux.intel.com

1 files changed, 13 insertions, 8 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index ed31bb2b82de..138020b5edf7 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -33,6 +33,8 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
 
 	obj->mm.get_page.sg_pos = pages->sgl;
 	obj->mm.get_page.sg_idx = 0;
+	obj->mm.get_dma_page.sg_pos = pages->sgl;
+	obj->mm.get_dma_page.sg_idx = 0;
 
 	obj->mm.pages = pages;
 
@@ -155,6 +157,8 @@ static void __i915_gem_object_reset_page_iter(struct drm_i915_gem_object *obj)
 	rcu_read_lock();
 	radix_tree_for_each_slot(slot, &obj->mm.get_page.radix, &iter, 0)
 		radix_tree_delete(&obj->mm.get_page.radix, iter.index);
+	radix_tree_for_each_slot(slot, &obj->mm.get_dma_page.radix, &iter, 0)
+		radix_tree_delete(&obj->mm.get_dma_page.radix, iter.index);
 	rcu_read_unlock();
 }
 
@@ -450,11 +454,12 @@ void __i915_gem_object_release_map(struct drm_i915_gem_object *obj)
 }
 
 struct scatterlist *
-i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
-		       unsigned int n,
-		       unsigned int *offset)
+__i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
+			 struct i915_gem_object_page_iter *iter,
+			 unsigned int n,
+			 unsigned int *offset)
 {
-	struct i915_gem_object_page_iter *iter = &obj->mm.get_page;
+	const bool dma = iter == &obj->mm.get_dma_page;
 	struct scatterlist *sg;
 	unsigned int idx, count;
 
@@ -483,7 +488,7 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
 
 	sg = iter->sg_pos;
 	idx = iter->sg_idx;
-	count = __sg_page_count(sg);
+	count = dma ? __sg_dma_page_count(sg) : __sg_page_count(sg);
 
 	while (idx + count <= n) {
 		void *entry;
@@ -511,7 +516,7 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
 
 		idx += count;
 		sg = ____sg_next(sg);
-		count = __sg_page_count(sg);
+		count = dma ? __sg_dma_page_count(sg) : __sg_page_count(sg);
 	}
 
 scan:
@@ -529,7 +534,7 @@ scan:
 	while (idx + count <= n) {
 		idx += count;
 		sg = ____sg_next(sg);
-		count = __sg_page_count(sg);
+		count = dma ? __sg_dma_page_count(sg) : __sg_page_count(sg);
 	}
 
 	*offset = n - idx;
@@ -582,7 +587,7 @@ i915_gem_object_get_dma_address_len(struct drm_i915_gem_object *obj,
 	struct scatterlist *sg;
 	unsigned int offset;
 
-	sg = i915_gem_object_get_sg(obj, n, &offset);
+	sg = i915_gem_object_get_sg_dma(obj, n, &offset);
 
 	if (len)
 		*len = sg_dma_len(sg) - (offset << PAGE_SHIFT);