[PATCH 1/4] 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.

Testcase: igt/gem_stolen

Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h |  1 +
 drivers/gpu/drm/i915/i915_gem.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index ea9caf2..f6af9c0 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2764,6 +2764,7 @@ 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_clear_object(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 a2a4a27..fc434ae 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5469,3 +5469,37 @@ bool i915_gem_obj_is_pinned(struct drm_i915_gem_object *obj)
 	return false;
 }
 
+int i915_gem_clear_object(struct drm_i915_gem_object *obj)
+{
+	int ret = 0;
+	char __iomem *base;
+	int size = obj->base.size;
+	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
+	unsigned alignment = 0;
+
+	ret = i915_gem_obj_ggtt_pin(obj, alignment, PIN_MAPPABLE);
+	if (ret) {
+		DRM_ERROR("Mapping of gem object to GTT failed\n");
+		return ret;
+	}
+
+	ret = i915_gem_object_put_fence(obj);
+	if (ret)
+		goto unpin;
+
+	/* Get the CPU virtual address of the buffer */
+	base = ioremap_wc(dev_priv->gtt.mappable_base +
+			  i915_gem_obj_ggtt_offset(obj), 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:
+	i915_gem_object_ggtt_unpin(obj);
+	return ret;
+}
-- 
1.9.1

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