[PATCH 4/5] drm/i915: Add a partial GGTT view type

[Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>]

Partial view type allows manipulating parts of huge BOs through the GGTT,
which was not previously possible due to constraint that whole object had
to be mapped for any access to it through GGTT.

Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c |   46 +++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem_gtt.h |   15 ++++++++++--
 2 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 5babbd3..5937d3d 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2764,6 +2764,47 @@ err_st_alloc:
 	return ERR_PTR(ret);
 }
 
+static struct sg_table *
+intel_partial_pages(const struct i915_ggtt_view *view,
+		    struct drm_i915_gem_object *obj)
+{
+	struct sg_table *st;
+	struct scatterlist *sg;
+	struct sg_page_iter obj_sg_iter;
+	int ret;
+
+	st = kmalloc(sizeof(*st), GFP_KERNEL);
+	if (!st)
+		goto err_st_alloc;
+
+	ret = sg_alloc_table(st, view->params.partial.size, GFP_KERNEL);
+	if (ret)
+		goto err_sg_alloc;
+
+	sg = st->sgl;
+	st->nents = 0;
+	for_each_sg_page(obj->pages->sgl, &obj_sg_iter, obj->pages->nents,
+		view->params.partial.offset)
+	{
+		if (st->nents >= view->params.partial.size)
+			break;
+
+		sg_set_page(sg, NULL, PAGE_SIZE, 0);
+		sg_dma_address(sg) = sg_page_iter_dma_address(&obj_sg_iter);
+		sg_dma_len(sg) = PAGE_SIZE;
+
+		sg = sg_next(sg);
+		st->nents++;
+	}
+
+	return st;
+
+err_sg_alloc:
+	kfree(st);
+err_st_alloc:
+	return ERR_PTR(-ENOMEM);
+}
+
 static int
 i915_get_ggtt_vma_pages(struct i915_vma *vma)
 {
@@ -2777,6 +2818,9 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
 	else if (vma->ggtt_view.type == I915_GGTT_VIEW_ROTATED)
 		vma->ggtt_view.pages =
 			intel_rotate_fb_obj_pages(&vma->ggtt_view, vma->obj);
+	else if (vma->ggtt_view.type == I915_GGTT_VIEW_PARTIAL)
+		vma->ggtt_view.pages =
+			intel_partial_pages(&vma->ggtt_view, vma->obj);
 	else
 		WARN_ONCE(1, "GGTT view %u not implemented!\n",
 			  vma->ggtt_view.type);
@@ -2859,6 +2903,8 @@ i915_ggtt_view_size(struct drm_i915_gem_object *obj,
 	if (view->type == I915_GGTT_VIEW_NORMAL ||
 	    view->type == I915_GGTT_VIEW_ROTATED) {
 		return obj->base.size;
+	} else if (view->type == I915_GGTT_VIEW_PARTIAL) {
+		return view->params.partial.size << PAGE_SHIFT;
 	} else {
 		WARN_ONCE(1, "GGTT view %u not implemented!\n", view->type);
 		return obj->base.size;
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 34b7cca..ab1ad8a 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -117,7 +117,8 @@ typedef uint64_t gen8_pde_t;
 
 enum i915_ggtt_view_type {
 	I915_GGTT_VIEW_NORMAL = 0,
-	I915_GGTT_VIEW_ROTATED
+	I915_GGTT_VIEW_ROTATED,
+	I915_GGTT_VIEW_PARTIAL,
 };
 
 struct intel_rotation_info {
@@ -130,6 +131,13 @@ struct intel_rotation_info {
 struct i915_ggtt_view {
 	enum i915_ggtt_view_type type;
 
+	union {
+		struct {
+			pgoff_t offset;
+			size_t size;
+		} partial;
+	} params;
+
 	struct sg_table *pages;
 
 	union {
@@ -495,7 +503,10 @@ i915_ggtt_view_equal(const struct i915_ggtt_view *a,
 	if (WARN_ON(!a || !b))
 		return false;
 
-	return a->type == b->type;
+	if (a->type != b->type)
+		return false;
+
+	return !memcmp(&a->params, &b->params, sizeof(a->params));
 }
 
 size_t
-- 
1.7.9.5



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