[Intel-gfx] [PATCH] drm/i915: Clear the stolen fb before enabling

[Chris Wilson]

As the stolen memory region will contain the contents of whatever was
last there, it invariably contains garbage. To be consistent with the
shmemfs backed fb and the expectations of the fb layer, we need to clear
the fb prior to installing it as an fbcon.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=58111
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_fb.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_fb.c b/drivers/gpu/drm/i915/intel_fb.c
index 30d317a..a815e64 100644
--- a/drivers/gpu/drm/i915/intel_fb.c
+++ b/drivers/gpu/drm/i915/intel_fb.c
@@ -104,6 +104,13 @@ static struct fb_info *intelfb_create_info(struct intel_fbdev *ifbdev)
 	if (!info->screen_base)
 		goto err_cmap;
 
+	/* If the object is shmemfs backed, it will have given us zeroed pages.
+	 * If the object is stolen however, it will be full of whatever
+	 * garbage was left in there.
+	 */
+	if (ifbdev->ifb.obj->stolen)
+		memset(info->screen_base, 0, info->screen_size);
+
 	/* Use default scratch pixmap (info->pixmap.flags = FB_PIXMAP_SYSTEM) */
 
 	drm_fb_helper_fill_fix(info, fb->pitches[0], fb->depth);
-- 
1.7.10.4