drm/i915: Wait for vblank before unpinning old fb

Be paranoid and ensure that the vblank has passed and the scanout has
switched to the new fb, before unpinning the old one and possibly
tearing down its PTEs.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f2d50141e0c2..840bfc3ae719 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1626,8 +1626,10 @@ intel_pipe_set_base(struct drm_crtc *crtc, int x, int y,
                 return ret;
         }
 
-        if (old_fb)
+        if (old_fb) {
+                intel_wait_for_vblank(dev, intel_crtc->pipe);
                 i915_gem_object_unpin(to_intel_framebuffer(old_fb)->obj);
+        }
 
         mutex_unlock(&dev->struct_mutex);