[PATCH 11/38] drm: rcar-du: Wait for page flip completion when turning the CRTC off

[Laurent Pinchart]

Turning a CRTC off will prevent a queued page flip from ever completing,
potentially confusing userspace. Wait for queued page flips to complete
before turning the CRTC off to avoid this.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
---
 drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 35 ++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/rcar-du/rcar_du_crtc.h |  3 +++
 2 files changed, 38 insertions(+)

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c 
b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
index e0562f2b3261..7f5ae0269a61 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
@@ -300,11 +300,39 @@ static void rcar_du_crtc_finish_page_flip(struct 
rcar_du_crtc *rcrtc)

        spin_lock_irqsave(&dev->event_lock, flags);
        drm_send_vblank_event(dev, rcrtc->index, event);
+       wake_up(&rcrtc->flip_wait);
        spin_unlock_irqrestore(&dev->event_lock, flags);

        drm_vblank_put(dev, rcrtc->index);
 }

+static bool rcar_du_crtc_page_flip_pending(struct rcar_du_crtc *rcrtc)
+{
+       struct drm_device *dev = rcrtc->crtc.dev;
+       unsigned long flags;
+       bool pending;
+
+       spin_lock_irqsave(&dev->event_lock, flags);
+       pending = rcrtc->event != NULL;
+       spin_unlock_irqrestore(&dev->event_lock, flags);
+
+       return pending;
+}
+
+static void rcar_du_crtc_wait_page_flip(struct rcar_du_crtc *rcrtc)
+{
+       struct rcar_du_device *rcdu = rcrtc->group->dev;
+
+       if (wait_event_timeout(rcrtc->flip_wait,
+                              !rcar_du_crtc_page_flip_pending(rcrtc),
+                              msecs_to_jiffies(50)))
+               return;
+
+       dev_warn(rcdu->dev, "page flip timeout\n");
+
+       rcar_du_crtc_finish_page_flip(rcrtc);
+}
+
 /* 
-----------------------------------------------------------------------------
  * Start/Stop and Suspend/Resume
  */
@@ -365,6 +393,11 @@ static void rcar_du_crtc_stop(struct rcar_du_crtc *rcrtc)
        if (!rcrtc->started)
                return;

+       /* Wait for page flip completion before stopping the CRTC as userspace
+        * excepts page flips to eventually complete.
+        */
+       rcar_du_crtc_wait_page_flip(rcrtc);
+
        mutex_lock(&rcrtc->group->planes.lock);
        rcrtc->plane->enabled = false;
        rcar_du_crtc_update_planes(crtc);
@@ -644,6 +677,8 @@ int rcar_du_crtc_create(struct rcar_du_group *rgrp, 
unsigned int index)
                return -EPROBE_DEFER;
        }

+       init_waitqueue_head(&rcrtc->flip_wait);
+
        rcrtc->group = rgrp;
        rcrtc->mmio_offset = mmio_offsets[index];
        rcrtc->index = index;
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h 
b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
index d2f89f7d2e5e..fb39e040f17b 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
+++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h
@@ -15,6 +15,7 @@
 #define __RCAR_DU_CRTC_H__

 #include <linux/mutex.h>
+#include <linux/wait.h>

 #include <drm/drmP.h>
 #include <drm/drm_crtc.h>
@@ -32,6 +33,8 @@ struct rcar_du_crtc {
        bool started;

        struct drm_pending_vblank_event *event;
+       wait_queue_head_t flip_wait;
+
        unsigned int outputs;
        int dpms;

-- 
2.0.5