drm/exynos: wait for the completion of pending page flip

This patch fixes the issue that drm_vblank_get() is failed.

The issus occurs when next page flip request is tried
if previous page flip event wasn't completed yet and then
dpms became off.

So this patch make sure that page flip event is completed
before dpms goes to off.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_crtc.c

@@ -48,6 +48,8 @@ struct exynos_drm_crtc {
 	unsigned int			pipe;
 	unsigned int			dpms;
 	enum exynos_crtc_mode		mode;
+	wait_queue_head_t		pending_flip_queue;
+	atomic_t			pending_flip;
 };
 
 static void exynos_drm_crtc_dpms(struct drm_crtc *crtc, int mode)
@@ -61,6 +63,13 @@ static void exynos_drm_crtc_dpms(struct drm_crtc *crtc, int mode)
 		return;
 	}
 
+	if (mode > DRM_MODE_DPMS_ON) {
+		/* wait for the completion of page flip. */
+		wait_event(exynos_crtc->pending_flip_queue,
+				atomic_read(&exynos_crtc->pending_flip) == 0);
+		drm_vblank_off(crtc->dev, exynos_crtc->pipe);
+	}
+
 	exynos_drm_fn_encoder(crtc, &mode, exynos_drm_encoder_crtc_dpms);
 	exynos_crtc->dpms = mode;
 }
@@ -224,6 +233,7 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
 		spin_lock_irq(&dev->event_lock);
 		list_add_tail(&event->base.link,
 				&dev_priv->pageflip_event_list);
+		atomic_set(&exynos_crtc->pending_flip, 1);
 		spin_unlock_irq(&dev->event_lock);
 
 		crtc->fb = fb;
@@ -343,6 +353,8 @@ int exynos_drm_crtc_create(struct drm_device *dev, unsigned int nr)
 
 	exynos_crtc->pipe = nr;
 	exynos_crtc->dpms = DRM_MODE_DPMS_OFF;
+	init_waitqueue_head(&exynos_crtc->pending_flip_queue);
+	atomic_set(&exynos_crtc->pending_flip, 0);
 	exynos_crtc->plane = exynos_plane_init(dev, 1 << nr, true);
 	if (!exynos_crtc->plane) {
 		kfree(exynos_crtc);
@@ -397,6 +409,8 @@ void exynos_drm_crtc_finish_pageflip(struct drm_device *dev, int crtc)
 {
 	struct exynos_drm_private *dev_priv = dev->dev_private;
 	struct drm_pending_vblank_event *e, *t;
+	struct drm_crtc *drm_crtc = dev_priv->crtc[crtc];
+	struct exynos_drm_crtc *exynos_crtc = to_exynos_crtc(drm_crtc);
 	unsigned long flags;
 
 	DRM_DEBUG_KMS("%s\n", __FILE__);
@@ -412,6 +426,8 @@ void exynos_drm_crtc_finish_pageflip(struct drm_device *dev, int crtc)
 		list_del(&e->base.link);
 		drm_send_vblank_event(dev, -1, e);
 		drm_vblank_put(dev, crtc);
+		atomic_set(&exynos_crtc->pending_flip, 0);
+		wake_up(&exynos_crtc->pending_flip_queue);
 	}
 
 	spin_unlock_irqrestore(&dev->event_lock, flags);