drm: Add async event synchronization for drmWaitVblank

This patch adds a new flag to the drmWaitVblank ioctl, which asks the drm
to return immediately and notify userspace when the specified vblank sequence
happens by sending an event back on the drm fd.

The event mechanism works with the other flags supported by the ioctls,
specifically, the vblank sequence can be specified relatively or absolutely,
and works for primary and seconday crtc.

The signal field of the vblank request is used to provide user data,
which will be sent back to user space in the vblank event.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 95 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 0a6f0b3bdc78..72754aca7abf 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -550,6 +550,62 @@ out:
 	return ret;
 }
 
+static int drm_queue_vblank_event(struct drm_device *dev, int pipe,
+				  union drm_wait_vblank *vblwait,
+				  struct drm_file *file_priv)
+{
+	struct drm_pending_vblank_event *e;
+	struct timeval now;
+	unsigned long flags;
+	unsigned int seq;
+
+	e = kzalloc(sizeof *e, GFP_KERNEL);
+	if (e == NULL)
+		return -ENOMEM;
+
+	e->pipe = pipe;
+	e->event.base.type = DRM_EVENT_VBLANK;
+	e->event.base.length = sizeof e->event;
+	e->event.user_data = vblwait->request.signal;
+	e->base.event = &e->event.base;
+	e->base.file_priv = file_priv;
+	e->base.destroy = (void (*) (struct drm_pending_event *)) kfree;
+
+	do_gettimeofday(&now);
+	spin_lock_irqsave(&dev->event_lock, flags);
+
+	if (file_priv->event_space < sizeof e->event) {
+		spin_unlock_irqrestore(&dev->event_lock, flags);
+		kfree(e);
+		return -ENOMEM;
+	}
+
+	file_priv->event_space -= sizeof e->event;
+	seq = drm_vblank_count(dev, pipe);
+	if ((vblwait->request.type & _DRM_VBLANK_NEXTONMISS) &&
+	    (seq - vblwait->request.sequence) <= (1 << 23)) {
+		vblwait->request.sequence = seq + 1;
+	}
+
+	DRM_DEBUG("event on vblank count %d, current %d, crtc %d\n",
+		  vblwait->request.sequence, seq, pipe);
+
+	e->event.sequence = vblwait->request.sequence;
+	if ((seq - vblwait->request.sequence) <= (1 << 23)) {
+		e->event.tv_sec = now.tv_sec;
+		e->event.tv_usec = now.tv_usec;
+		drm_vblank_put(dev, e->pipe);
+		list_add_tail(&e->base.link, &e->base.file_priv->event_list);
+		wake_up_interruptible(&e->base.file_priv->event_wait);
+	} else {
+		list_add_tail(&e->base.link, &dev->vblank_event_list);
+	}
+
+	spin_unlock_irqrestore(&dev->event_lock, flags);
+
+	return 0;
+}
+
 /**
  * Wait for VBLANK.
  *
@@ -609,6 +665,9 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
 		goto done;
 	}
 
+	if (flags & _DRM_VBLANK_EVENT)
+		return drm_queue_vblank_event(dev, crtc, vblwait, file_priv);
+
 	if ((flags & _DRM_VBLANK_NEXTONMISS) &&
 	    (seq - vblwait->request.sequence) <= (1<<23)) {
 		vblwait->request.sequence = seq + 1;
@@ -641,6 +700,38 @@ done:
 	return ret;
 }
 
+void drm_handle_vblank_events(struct drm_device *dev, int crtc)
+{
+	struct drm_pending_vblank_event *e, *t;
+	struct timeval now;
+	unsigned long flags;
+	unsigned int seq;
+
+	do_gettimeofday(&now);
+	seq = drm_vblank_count(dev, crtc);
+
+	spin_lock_irqsave(&dev->event_lock, flags);
+
+	list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link) {
+		if (e->pipe != crtc)
+			continue;
+		if ((seq - e->event.sequence) > (1<<23))
+			continue;
+
+		DRM_DEBUG("vblank event on %d, current %d\n",
+			  e->event.sequence, seq);
+
+		e->event.sequence = seq;
+		e->event.tv_sec = now.tv_sec;
+		e->event.tv_usec = now.tv_usec;
+		drm_vblank_put(dev, e->pipe);
+		list_move_tail(&e->base.link, &e->base.file_priv->event_list);
+		wake_up_interruptible(&e->base.file_priv->event_wait);
+	}
+
+	spin_unlock_irqrestore(&dev->event_lock, flags);
+}
+
 /**
  * drm_handle_vblank - handle a vblank event
  * @dev: DRM device
@@ -651,7 +742,11 @@ done:
  */
 void drm_handle_vblank(struct drm_device *dev, int crtc)
 {
+	if (!dev->num_crtcs)
+		return;
+
 	atomic_inc(&dev->_vblank_count[crtc]);
 	DRM_WAKEUP(&dev->vbl_queue[crtc]);
+	drm_handle_vblank_events(dev, crtc);
 }
 EXPORT_SYMBOL(drm_handle_vblank);