[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)

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 | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 548a0eb..39b29d3 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_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 9d2e6e3..645b8a0 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5244,3 +5244,42 @@ 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_clear_object(struct drm_i915_gem_object *obj)
+{
+	int ret;
+	char __iomem *base;
+	size_t size = obj->base.size;
+	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
+
+	WARN_ON(!mutex_is_locked(&obj->base.dev->struct_mutex));
+	ret = i915_gem_obj_ggtt_pin(obj, 0, PIN_MAPPABLE);
+	if (ret)
+		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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