[Intel-gfx] [PATCH 6/7] drm/i915/vlv: Clear out contents of Frame buffer allocations from Stolen area

[akash.goel at intel.com]

From: Akash Goel <akash.goel at intel.com>

On VLV the User frame buffers could also get allocated from stolen area,
but there was no zeroing-out of the contents done, whereas by default
any allocation from shmem is zeroed out. Now the contents of Frame
buffers allocated from stolen area are also cleared, otherwise there
are corruptions observed in the display.

Signed-off-by: Akash Goel <akash.goel at intel.com>
---
 drivers/gpu/drm/i915/i915_gem_stolen.c | 40 +++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
index 29c22f9..253a39a 100644
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -371,6 +371,41 @@ i915_gem_object_create_stolen(struct drm_device *dev, u32 size)
 	return NULL;
 }
 
+static void i915_memset_stolen_obj(struct drm_i915_gem_object *obj)
+{
+	int ret;
+	char __iomem *base;
+	int size = obj->base.size;
+	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
+	unsigned alignment = 0;
+	bool map_and_fenceable =  true;
+	bool nonblocking = false;
+
+	ret = i915_gem_obj_ggtt_pin(obj, alignment, map_and_fenceable,
+				nonblocking);
+	if (ret) {
+		DRM_ERROR("Mapping of User FB to GTT failed\n");
+		return;
+	}
+
+	/* Get the CPU virtual address of the frame buffer */
+	base = ioremap_wc(dev_priv->gtt.mappable_base +
+				i915_gem_obj_ggtt_offset(obj), size);
+	if (base == NULL) {
+		DRM_ERROR("Mapping of User FB to CPU failed\n");
+		i915_gem_object_ggtt_unpin(obj);
+		return;
+	}
+
+	memset_io(base, 0, size);
+
+	iounmap(base);
+	i915_gem_object_ggtt_unpin(obj);
+
+	DRM_DEBUG_DRIVER("User FB obj ptr=%p cleared using CPU virt add %p\n",
+			 obj, base);
+}
+
 void
 i915_gem_object_move_to_stolen(struct drm_i915_gem_object *obj)
 {
@@ -454,7 +489,10 @@ i915_gem_object_move_to_stolen(struct drm_i915_gem_object *obj)
 	obj->base.read_domains = I915_GEM_DOMAIN_CPU | I915_GEM_DOMAIN_GTT;
 	obj->cache_level = HAS_LLC(dev) ? I915_CACHE_LLC : I915_CACHE_NONE;
 
-	/* No zeroing-out of buffers allocated from stolen area */
+	/* Zero-out the contents of the stolen object, otherwise we observe
+	 * corruptions in the display.
+	 */
+	i915_memset_stolen_obj(obj);
 	return;
 
 cleanup:
-- 
1.8.5.2