drm/exynos: track vblank events on a per crtc basis

The goal of the change is to make sure we send the vblank event on the
current vblank. My hope is to fix any races that might be causing flicker.
After this change I only see a flicker in the transition plymouth and
X11.

Simplified the code by tracking vblank events on a per-crtc basis. This
allowed me to remove all error paths from the callback. It also allowed
me to remove the vblank wait from the callback.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_crtc.c

@@ -34,9 +34,8 @@ static void exynos_drm_crtc_dpms(struct drm_crtc *crtc, int mode)
 	if (mode > DRM_MODE_DPMS_ON) {
 		/* wait for the completion of page flip. */
 		if (!wait_event_timeout(exynos_crtc->pending_flip_queue,
-				!atomic_read(&exynos_crtc->pending_flip),
-				HZ/20))
-			atomic_set(&exynos_crtc->pending_flip, 0);
+				(exynos_crtc->event == NULL), HZ/20))
+			exynos_crtc->event = NULL;
 		drm_crtc_vblank_off(crtc);
 	}
 
@@ -164,11 +163,10 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
 				     uint32_t page_flip_flags)
 {
 	struct drm_device *dev = crtc->dev;
-	struct exynos_drm_private *dev_priv = dev->dev_private;
 	struct exynos_drm_crtc *exynos_crtc = to_exynos_crtc(crtc);
 	struct drm_framebuffer *old_fb = crtc->primary->fb;
 	unsigned int crtc_w, crtc_h;
-	int ret = -EINVAL;
+	int ret;
 
 	/* when the page flip is requested, crtc's dpms should be on */
 	if (exynos_crtc->dpms > DRM_MODE_DPMS_ON) {
@@ -176,28 +174,30 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
 		return -EINVAL;
 	}
 
-	mutex_lock(&dev->struct_mutex);
+	if (!event)
+		return -EINVAL;
 
-	if (event) {
-		/*
-		 * the pipe from user always is 0 so we can set pipe number
-		 * of current owner to event.
-		 */
-		event->pipe = exynos_crtc->pipe;
+	spin_lock_irq(&dev->event_lock);
+	if (exynos_crtc->event) {
+		ret = -EBUSY;
+		goto out;
+	}
 
 	ret = drm_vblank_get(dev, exynos_crtc->pipe);
 	if (ret) {
 		DRM_DEBUG("failed to acquire vblank counter\n");
-
 		goto out;
 	}
 
-		spin_lock_irq(&dev->event_lock);
-		list_add_tail(&event->base.link,
-				&dev_priv->pageflip_event_list);
-		atomic_set(&exynos_crtc->pending_flip, 1);
+	exynos_crtc->event = event;
 	spin_unlock_irq(&dev->event_lock);
 
+	/*
+	 * the pipe from user always is 0 so we can set pipe number
+	 * of current owner to event.
+	 */
+	event->pipe = exynos_crtc->pipe;
+
 	crtc->primary->fb = fb;
 	crtc_w = fb->width - crtc->x;
 	crtc_h = fb->height - crtc->y;
@@ -206,18 +206,17 @@ static int exynos_drm_crtc_page_flip(struct drm_crtc *crtc,
 				  crtc_w, crtc_h);
 	if (ret) {
 		crtc->primary->fb = old_fb;
-
 		spin_lock_irq(&dev->event_lock);
+		exynos_crtc->event = NULL;
 		drm_vblank_put(dev, exynos_crtc->pipe);
-			list_del(&event->base.link);
-			atomic_set(&exynos_crtc->pending_flip, 0);
 		spin_unlock_irq(&dev->event_lock);
-
-			goto out;
-		}
+		return ret;
 	}
+
+	return 0;
+
 out:
-	mutex_unlock(&dev->struct_mutex);
+	spin_unlock_irq(&dev->event_lock);
 	return ret;
 }
 
@@ -255,7 +254,6 @@ struct exynos_drm_crtc *exynos_drm_crtc_create(struct drm_device *drm_dev,
 		return ERR_PTR(-ENOMEM);
 
 	init_waitqueue_head(&exynos_crtc->pending_flip_queue);
-	atomic_set(&exynos_crtc->pending_flip, 0);
 
 	exynos_crtc->dpms = DRM_MODE_DPMS_OFF;
 	exynos_crtc->pipe = pipe;
@@ -313,26 +311,20 @@ void exynos_drm_crtc_disable_vblank(struct drm_device *dev, int pipe)
 void exynos_drm_crtc_finish_pageflip(struct drm_device *dev, int pipe)
 {
 	struct exynos_drm_private *dev_priv = dev->dev_private;
-	struct drm_pending_vblank_event *e, *t;
 	struct drm_crtc *drm_crtc = dev_priv->crtc[pipe];
 	struct exynos_drm_crtc *exynos_crtc = to_exynos_crtc(drm_crtc);
 	unsigned long flags;
 
 	spin_lock_irqsave(&dev->event_lock, flags);
+	if (exynos_crtc->event) {
 
-	list_for_each_entry_safe(e, t, &dev_priv->pageflip_event_list,
-			base.link) {
-		/* if event's pipe isn't same as crtc then ignore it. */
-		if (pipe != e->pipe)
-			continue;
-
-		list_del(&e->base.link);
-		drm_send_vblank_event(dev, -1, e);
+		drm_send_vblank_event(dev, -1, exynos_crtc->event);
 		drm_vblank_put(dev, pipe);
-		atomic_set(&exynos_crtc->pending_flip, 0);
 		wake_up(&exynos_crtc->pending_flip_queue);
+
 	}
 
+	exynos_crtc->event = NULL;
 	spin_unlock_irqrestore(&dev->event_lock, flags);
 }
 

drivers/gpu/drm/exynos/exynos_drm_drv.c

@@ -60,7 +60,6 @@ static int exynos_drm_load(struct drm_device *dev, unsigned long flags)
 	if (!private)
 		return -ENOMEM;
 
-	INIT_LIST_HEAD(&private->pageflip_event_list);
 	dev_set_drvdata(dev->dev, dev);
 	dev->dev_private = (void *)private;
 
@@ -223,25 +222,13 @@ static void exynos_drm_preclose(struct drm_device *dev,
 
 static void exynos_drm_postclose(struct drm_device *dev, struct drm_file *file)
 {
-	struct exynos_drm_private *private = dev->dev_private;
-	struct drm_pending_vblank_event *v, *vt;
 	struct drm_pending_event *e, *et;
 	unsigned long flags;
 
 	if (!file->driver_priv)
 		return;
 
-	/* Release all events not unhandled by page flip handler. */
 	spin_lock_irqsave(&dev->event_lock, flags);
-	list_for_each_entry_safe(v, vt, &private->pageflip_event_list,
-			base.link) {
-		if (v->base.file_priv == file) {
-			list_del(&v->base.link);
-			drm_vblank_put(dev, v->pipe);
-			v->base.destroy(&v->base);
-		}
-	}
-
 	/* Release all events handled by page flip handler but not freed. */
 	list_for_each_entry_safe(e, et, &file->event_list, link) {
 		list_del(&e->link);

drivers/gpu/drm/exynos/exynos_drm_drv.h

@@ -206,6 +206,7 @@ struct exynos_drm_crtc_ops {
  *	we can refer to the crtc to current hardware interrupt occurred through
  *	this pipe value.
  * @dpms: store the crtc dpms value
+ * @event: vblank event that is currently queued for flip
  * @ops: pointer to callbacks for exynos drm specific functionality
  * @ctx: A pointer to the crtc's implementation specific context
  */
@@ -215,7 +216,7 @@ struct exynos_drm_crtc {
 	unsigned int			pipe;
 	unsigned int			dpms;
 	wait_queue_head_t		pending_flip_queue;
-	atomic_t			pending_flip;
+	struct drm_pending_vblank_event	*event;
 	struct exynos_drm_crtc_ops	*ops;
 	void				*ctx;
 };
@@ -245,9 +246,6 @@ struct drm_exynos_file_private {
 struct exynos_drm_private {
 	struct drm_fb_helper *fb_helper;
 
-	/* list head for new event to be added. */
-	struct list_head pageflip_event_list;
-
 	/*
 	 * created crtc object would be contained at this array and
 	 * this array is used to be aware of which crtc did it request vblank.