drm/exynos: fixed page flip issue.

with vblank_refcount = 1, there was the case that drm_vblank_put
is called by specific page flip function so this patch fixes the
issue.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/exynos/exynos_drm_crtc.c

@@ -307,9 +307,6 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
 		 */
 		event->pipe = exynos_crtc->pipe;
 
-		list_add_tail(&event->base.link,
-				&dev_priv->pageflip_event_list);
-
 		ret = drm_vblank_get(dev, exynos_crtc->pipe);
 		if (ret) {
 			DRM_DEBUG("failed to acquire vblank counter\n");
@@ -318,6 +315,9 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
 			goto out;
 		}
 
+		list_add_tail(&event->base.link,
+				&dev_priv->pageflip_event_list);
+
 		crtc->fb = fb;
 		ret = exynos_drm_crtc_update(crtc);
 		if (ret) {

drivers/gpu/drm/exynos/exynos_drm_fimd.c

@@ -604,7 +604,12 @@ static void fimd_finish_pageflip(struct drm_device *drm_dev, int crtc)
 	}
 
 	if (is_checked) {
-		drm_vblank_put(drm_dev, crtc);
+		/*
+		 * call drm_vblank_put only in case that drm_vblank_get was
+		 * called.
+		 */
+		if (atomic_read(&drm_dev->vblank_refcount[crtc]) > 0)
+			drm_vblank_put(drm_dev, crtc);
 
 		/*
 		 * don't off vblank if vblank_disable_allowed is 1,

drivers/gpu/drm/exynos/exynos_mixer.c

@@ -712,7 +712,12 @@ static void mixer_finish_pageflip(struct drm_device *drm_dev, int crtc)
 	}
 
 	if (is_checked)
-		drm_vblank_put(drm_dev, crtc);
+		/*
+		 * call drm_vblank_put only in case that drm_vblank_get was
+		 * called.
+		 */
+		if (atomic_read(&drm_dev->vblank_refcount[crtc]) > 0)
+			drm_vblank_put(drm_dev, crtc);
 
 	spin_unlock_irqrestore(&drm_dev->event_lock, flags);
 }