drm/sun4i: crtc: Call drm_crtc_vblank_on / drm_crtc_vblank_off

Make sure that the CRTC code will call the enable/disable_vblank hooks.

Otherwise, since the refcounting will be off, we might end up in a
situation where the vblank management functions are called while the CRTC
is off.
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180221125703.4595-3-maxime.ripard@bootlin.com

drivers/gpu/drm/sun4i/sun4i_crtc.c

@@ -93,6 +93,8 @@ static void sun4i_crtc_atomic_disable(struct drm_crtc *crtc,
 
 	DRM_DEBUG_DRIVER("Disabling the CRTC\n");
 
+	drm_crtc_vblank_off(crtc);
+
 	sun4i_tcon_set_status(scrtc->tcon, encoder, false);
 
 	if (crtc->state->event && !crtc->state->active) {
@@ -113,6 +115,8 @@ static void sun4i_crtc_atomic_enable(struct drm_crtc *crtc,
 	DRM_DEBUG_DRIVER("Enabling the CRTC\n");
 
 	sun4i_tcon_set_status(scrtc->tcon, encoder, true);
+
+	drm_crtc_vblank_on(crtc);
 }
 
 static void sun4i_crtc_mode_set_nofb(struct drm_crtc *crtc)