drm/fsl-du: Implement some semblance of vblank event handling

No idea how exactly fsl-du commits hw state changes, but here in flush
is probably the safest place.

While at it nuke the dummy functions.

v2: Be more robust and either arm, when the CRTC is on, or just send
the event out right away.

Cc: Stefan Agner <stefan@agner.ch>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465388359-8070-4-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c

@@ -22,20 +22,21 @@
 #include "fsl_dcu_drm_drv.h"
 #include "fsl_dcu_drm_plane.h"
 
-static void fsl_dcu_drm_crtc_atomic_begin(struct drm_crtc *crtc,
+static void fsl_dcu_drm_crtc_atomic_flush(struct drm_crtc *crtc,
 					  struct drm_crtc_state *old_crtc_state)
 {
-}
+	struct drm_pending_vblank_event *event = crtc->state->event;
 
-static int fsl_dcu_drm_crtc_atomic_check(struct drm_crtc *crtc,
-					 struct drm_crtc_state *state)
-{
-	return 0;
-}
+	if (event) {
+		crtc->state->event = NULL;
 
-static void fsl_dcu_drm_crtc_atomic_flush(struct drm_crtc *crtc,
-					  struct drm_crtc_state *old_crtc_state)
-{
+		spin_lock_irq(&crtc->dev->event_lock);
+		if (drm_crtc_vblank_get(crtc) == 0)
+			drm_crtc_arm_vblank_event(crtc, event);
+		else
+			drm_crtc_send_vblank_event(crtc, event);
+		spin_unlock_irq(&crtc->dev->event_lock);
+	}
 }
 
 static void fsl_dcu_drm_disable_crtc(struct drm_crtc *crtc)
@@ -117,8 +118,6 @@ static void fsl_dcu_drm_crtc_mode_set_nofb(struct drm_crtc *crtc)
 }
 
 static const struct drm_crtc_helper_funcs fsl_dcu_drm_crtc_helper_funcs = {
-	.atomic_begin = fsl_dcu_drm_crtc_atomic_begin,
-	.atomic_check = fsl_dcu_drm_crtc_atomic_check,
 	.atomic_flush = fsl_dcu_drm_crtc_atomic_flush,
 	.disable = fsl_dcu_drm_disable_crtc,
 	.enable = fsl_dcu_drm_crtc_enable,