[RFC PATCH 2/3] v4l: vsp1: extend VSP1 module API to allow DRM callback registration

[Kieran Bingham]

To be able to perform page flips in DRM without flicker we need to be
able to notify the rcar-du module when the VSP has completed its
processing.

To synchronise the page flip events for userspace, we move the required
event through the VSP to track the data flow. When the frame is
completed, the event can be returned back to the originator through the
registered callback.

We must not have bidirectional dependencies on the two components to
maintain support for loadable modules, thus we extend the API to allow
a callback to be registered within the VSP DRM interface.

Signed-off-by: Kieran Bingham <kieran.bingham+renesas at ideasonboard.com>
---
 drivers/gpu/drm/rcar-du/rcar_du_vsp.c  |  2 +-
 drivers/media/platform/vsp1/vsp1_drm.c | 42 +++++++++++++++++++++++++--
 drivers/media/platform/vsp1/vsp1_drm.h | 12 ++++++++-
 include/media/vsp1.h                   |  6 +++-
 4 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
index b5bfbe50bd87..71e70e1e0881 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
@@ -81,7 +81,7 @@ void rcar_du_vsp_atomic_begin(struct rcar_du_crtc *crtc)
 
 void rcar_du_vsp_atomic_flush(struct rcar_du_crtc *crtc)
 {
-	vsp1_du_atomic_flush(crtc->vsp->vsp);
+	vsp1_du_atomic_flush(crtc->vsp->vsp, NULL);
 }
 
 /* Keep the two tables in sync. */
diff --git a/drivers/media/platform/vsp1/vsp1_drm.c b/drivers/media/platform/vsp1/vsp1_drm.c
index 8e2aa3f8e52f..743cbce48d0c 100644
--- a/drivers/media/platform/vsp1/vsp1_drm.c
+++ b/drivers/media/platform/vsp1/vsp1_drm.c
@@ -52,6 +52,40 @@ int vsp1_du_init(struct device *dev)
 EXPORT_SYMBOL_GPL(vsp1_du_init);
 
 /**
+ * vsp1_du_register_callback - Register VSP completion notifier callback
+ *
+ * Allow the DRM framework to register a callback with us to notify the end of
+ * processing each frame. This allows synchronisation for page flipping.
+ *
+ * @dev: the VSP device
+ * @callback: the callback function to notify the DU module
+ * @private: private structure data to pass with the callback
+ *
+ */
+void vsp1_du_register_callback(struct device *dev,
+			       void (*callback)(void *, void *),
+			       void *private)
+{
+	struct vsp1_device *vsp1 = dev_get_drvdata(dev);
+
+	vsp1->drm->du_complete = callback;
+	vsp1->drm->du_private = private;
+}
+EXPORT_SYMBOL_GPL(vsp1_du_register_callback);
+
+static void vsp1_du_pipeline_frame_end(struct vsp1_pipeline *pipe)
+{
+	struct vsp1_drm *drm = to_vsp1_drm(pipe);
+
+	if (drm->du_complete && drm->active_data)
+		drm->du_complete(drm->du_private, drm->active_data);
+
+	/* The pending frame is now active */
+	drm->active_data = drm->pending_data;
+	drm->pending_data = NULL;
+}
+
+/**
  * vsp1_du_setup_lif - Setup the output part of the VSP pipeline
  * @dev: the VSP device
  * @width: output frame width in pixels
@@ -99,7 +133,8 @@ int vsp1_du_setup_lif(struct device *dev, unsigned int width,
 		}
 
 		pipe->num_inputs = 0;
-
+		pipe->frame_end = NULL;
+		vsp1->drm->du_complete = NULL;
 		vsp1_dlm_reset(pipe->output->dlm);
 		vsp1_device_put(vsp1);
 
@@ -196,6 +231,8 @@ int vsp1_du_setup_lif(struct device *dev, unsigned int width,
 	if (ret < 0)
 		return ret;
 
+	pipe->frame_end = vsp1_du_pipeline_frame_end;
+
 	ret = media_entity_pipeline_start(&pipe->output->entity.subdev.entity,
 					  &pipe->pipe);
 	if (ret < 0) {
@@ -420,7 +457,7 @@ static unsigned int rpf_zpos(struct vsp1_device *vsp1, struct vsp1_rwpf *rpf)
  * vsp1_du_atomic_flush - Commit an atomic update
  * @dev: the VSP device
  */
-void vsp1_du_atomic_flush(struct device *dev)
+void vsp1_du_atomic_flush(struct device *dev, void *data)
 {
 	struct vsp1_device *vsp1 = dev_get_drvdata(dev);
 	struct vsp1_pipeline *pipe = &vsp1->drm->pipe;
@@ -504,6 +541,7 @@ void vsp1_du_atomic_flush(struct device *dev)
 
 	vsp1_dl_list_commit(pipe->dl);
 	pipe->dl = NULL;
+	vsp1->drm->pending_data = data;
 
 	/* Start or stop the pipeline if needed. */
 	if (!vsp1->drm->num_inputs && pipe->num_inputs) {
diff --git a/drivers/media/platform/vsp1/vsp1_drm.h b/drivers/media/platform/vsp1/vsp1_drm.h
index 9e28ab9254ba..fde19e5948a0 100644
--- a/drivers/media/platform/vsp1/vsp1_drm.h
+++ b/drivers/media/platform/vsp1/vsp1_drm.h
@@ -33,8 +33,20 @@ struct vsp1_drm {
 		struct v4l2_rect compose;
 		unsigned int zpos;
 	} inputs[VSP1_MAX_RPF];
+
+	/* Frame syncronisation */
+	void (*du_complete)(void *, void *);
+	void *du_private;
+	void *pending_data;
+	void *active_data;
 };
 
+static inline struct vsp1_drm *
+to_vsp1_drm(struct vsp1_pipeline *pipe)
+{
+	return container_of(pipe, struct vsp1_drm, pipe);
+}
+
 int vsp1_drm_init(struct vsp1_device *vsp1);
 void vsp1_drm_cleanup(struct vsp1_device *vsp1);
 int vsp1_drm_create_links(struct vsp1_device *vsp1);
diff --git a/include/media/vsp1.h b/include/media/vsp1.h
index 458b400373d4..f82fbab01f21 100644
--- a/include/media/vsp1.h
+++ b/include/media/vsp1.h
@@ -20,6 +20,10 @@ struct device;
 
 int vsp1_du_init(struct device *dev);
 
+void vsp1_du_register_callback(struct device *dev,
+			       void (*callback)(void *, void *),
+			       void *private);
+
 int vsp1_du_setup_lif(struct device *dev, unsigned int width,
 		      unsigned int height);
 
@@ -36,6 +40,6 @@ struct vsp1_du_atomic_config {
 void vsp1_du_atomic_begin(struct device *dev);
 int vsp1_du_atomic_update(struct device *dev, unsigned int rpf,
 			  const struct vsp1_du_atomic_config *cfg);
-void vsp1_du_atomic_flush(struct device *dev);
+void vsp1_du_atomic_flush(struct device *dev, void *data);
 
 #endif /* __MEDIA_VSP1_H__ */
-- 
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