[PATCH 1/6] drm/i915: Clearing buffer objects via CPU/GTT

[ankitprasad.r.sharma@intel.com]

From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>

This patch adds support for clearing buffer objects via CPU/GTT. This
is particularly useful for clearing out the non shmem backed objects.
Currently intend to use this only for buffers allocated from stolen
region.

v2: Added kernel doc for i915_gem_clear_object(), corrected/removed
variable assignments (Tvrtko)

v3: Map object page by page to the gtt if the pinning of the whole object
to the ggtt fails, Corrected function name (Chris)

Testcase: igt/gem_stolen

Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h |  1 +
 drivers/gpu/drm/i915/i915_gem.c | 79 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 548a0eb..8e554d3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2856,6 +2856,7 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj,
 				    int *needs_clflush);
 
 int __must_check i915_gem_object_get_pages(struct drm_i915_gem_object *obj);
+int i915_gem_object_clear(struct drm_i915_gem_object *obj);
 
 static inline int __sg_page_count(struct scatterlist *sg)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9d2e6e3..d57e850 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5244,3 +5244,82 @@ fail:
 	drm_gem_object_unreference(&obj->base);
 	return ERR_PTR(ret);
 }
+
+/**
+ * i915_gem_clear_object() - Clear buffer object via CPU/GTT
+ * @obj: Buffer object to be cleared
+ *
+ * Return: 0 - success, non-zero - failure
+ */
+int i915_gem_object_clear(struct drm_i915_gem_object *obj)
+{
+	int ret, i;
+	char __iomem *base;
+	size_t size = obj->base.size;
+	struct drm_i915_private *i915 = to_i915(obj->base.dev);
+	struct drm_mm_node node;
+
+	WARN_ON(!mutex_is_locked(&obj->base.dev->struct_mutex));
+	ret = i915_gem_obj_ggtt_pin(obj, 0, PIN_MAPPABLE | PIN_NONBLOCK);
+	if (ret) {
+		memset(&node, 0, sizeof(node));
+		ret = drm_mm_insert_node_in_range_generic(&i915->gtt.base.mm,
+							  &node, 4096, 0,
+							  I915_CACHE_NONE, 0,
+							  i915->gtt.mappable_end,
+							  DRM_MM_SEARCH_DEFAULT,
+							  DRM_MM_CREATE_DEFAULT);
+		if (ret)
+			goto out;
+
+		i915_gem_object_pin_pages(obj);
+	} else {
+		node.start = i915_gem_obj_ggtt_offset(obj);
+		node.allocated = false;
+	}
+
+	ret = i915_gem_object_put_fence(obj);
+	if (ret)
+		goto unpin;
+
+	if (node.allocated) {
+		for (i = 0; i < size/PAGE_SIZE; i++) {
+			wmb();
+			i915->gtt.base.insert_page(&i915->gtt.base,
+					i915_gem_object_get_dma_address(obj, i),
+					node.start,
+					I915_CACHE_NONE,
+					0);
+			wmb();
+			base = ioremap_wc(i915->gtt.mappable_base + node.start, 4096);
+			memset_io(base, 0, 4096);
+			iounmap(base);
+		}
+	} else {
+		/* Get the CPU virtual address of the buffer */
+		base = ioremap_wc(i915->gtt.mappable_base +
+				  node.start, size);
+		if (base == NULL) {
+			DRM_ERROR("Mapping of gem object to CPU failed!\n");
+			ret = -ENOSPC;
+			goto unpin;
+		}
+
+		memset_io(base, 0, size);
+		iounmap(base);
+	}
+unpin:
+	if (node.allocated) {
+		wmb();
+		i915->gtt.base.clear_range(&i915->gtt.base,
+				node.start, node.size,
+				true);
+		drm_mm_remove_node(&node);
+		i915_gem_object_unpin_pages(obj);
+	}
+	else {
+		i915_gem_object_ggtt_unpin(obj);
+	}
+out:
+	return ret;
+}
-- 
1.9.1

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