drm/exynos: extend vblank off delay time.

some platform could be entering to sleep after short time once lcd panel off
but before that vblank could be off by vblank off delay feature. at that time,
vblank doesn't have the pair between vblank_get/put. so this path makes vblank
off delay to have enough.

Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_drv.c

@@ -44,6 +44,8 @@
 #define DRIVER_MAJOR	1
 #define DRIVER_MINOR	0
 
+#define VBLANK_OFF_DELAY	50000
+
 static int exynos_drm_load(struct drm_device *dev, unsigned long flags)
 {
 	struct exynos_drm_private *private;
@@ -107,6 +109,8 @@ static int exynos_drm_load(struct drm_device *dev, unsigned long flags)
 		goto err_drm_device;
 	}
 
+	drm_vblank_offdelay = VBLANK_OFF_DELAY;
+
 	return 0;
 
 err_drm_device:

drivers/gpu/drm/exynos/exynos_drm_drv.h

@@ -41,6 +41,8 @@ struct drm_device;
 struct exynos_drm_overlay;
 struct drm_connector;
 
+extern unsigned int drm_vblank_offdelay;
+
 /* this enumerates display type. */
 enum exynos_drm_output_type {
 	EXYNOS_DISPLAY_TYPE_NONE,