[PATCH] drm/vc4: Return -EBUSY if there's already a pending flip event.

[robert.foss at collabora.com]

From: Robert Foss <robert.foss at collabora.com>

As per the docs, atomic_commit should return -EBUSY "if an asycnhronous
update is requested and there is an earlier update pending".

This patch is based on the rockchip patch below:
    http://article.gmane.org/gmane.comp.video.dri.devel/151678

Signed-off-by: Robert Foss <robert.foss at collabora.com>
---
 drivers/gpu/drm/vc4/vc4_crtc.c |  6 ++++++
 drivers/gpu/drm/vc4/vc4_drv.h  |  1 +
 drivers/gpu/drm/vc4/vc4_kms.c  | 20 ++++++++++++++++++--
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index 355ee4b..43193a3 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -802,3 +802,9 @@ struct platform_driver vc4_crtc_driver = {
 		.of_match_table = vc4_crtc_dt_match,
 	},
 };
+
+bool vc4_crtc_has_pending_event(struct drm_crtc *crtc)
+{
+	assert_spin_locked(&crtc->dev->event_lock);
+	return to_vc4_crtc(crtc)->event;
+}
diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index fa2ad15..54c1fb5 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -414,6 +414,7 @@ extern struct platform_driver vc4_crtc_driver;
 int vc4_enable_vblank(struct drm_device *dev, unsigned int crtc_id);
 void vc4_disable_vblank(struct drm_device *dev, unsigned int crtc_id);
 int vc4_crtc_debugfs_regs(struct seq_file *m, void *arg);
+bool vc4_crtc_has_pending_event(struct drm_crtc *crtc);
 
 /* vc4_debugfs.c */
 int vc4_debugfs_init(struct drm_minor *minor);
diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index 4718ae5..dc157a1e 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -107,10 +107,26 @@ static int vc4_atomic_commit(struct drm_device *dev,
 			     bool async)
 {
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
-	int ret;
-	int i;
 	uint64_t wait_seqno = 0;
 	struct vc4_commit *c;
+	struct drm_crtc_state *crtc_state;
+	struct drm_crtc *crtc;
+	unsigned long flags;
+	int i, ret;
+
+	if (async) {
+		for_each_crtc_in_state(state, crtc, crtc_state, i) {
+
+			spin_lock_irqsave(&dev->event_lock, flags);
+
+			if (crtc->state->event || 
+				vc4_crtc_has_pending_event(crtc)) {
+				spin_unlock_irqrestore(&dev->event_lock, flags);
+				return -EBUSY;
+			}
+			spin_unlock_irqrestore(&dev->event_lock, flags);
+		}
+	}
 
 	c = commit_init(state);
 	if (!c)
-- 
2.5.0