[RFC v5 10/11] [media] vb2: add out-fence support to QBUF

[Gustavo Padovan]

From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>

If V4L2_BUF_FLAG_OUT_FENCE flag is present on the QBUF call we create
an out_fence and send its fd to userspace on the fence_fd field as a
return arg for the QBUF call.

The fence is signaled on buffer_done(), when the job on the buffer is
finished.

With out-fences we do not allow drivers to requeue buffers through vb2,
instead we flag an error on the buffer, signals it fence with error and
return it to userspace.

v6
	- get rid of the V4L2_EVENT_OUT_FENCE event. We always keep the
	ordering in vb2 for queueing in the driver, so the event is not
	necessary anymore and the out_fence_fd is sent back to userspace
	on QBUF call return arg
	- do not allow requeueing with out-fences, instead mark the buffer
	with an error and wake up to userspace.
	- send the out_fence_fd back to userspace on the fence_fd field

v5:
	- delay fd_install to DQ_EVENT (Hans)
	- if queue is fully ordered send OUT_FENCE event right away
	(Brian)
	- rename 'q->ordered' to 'q->ordered_in_driver'
	- merge change to implement OUT_FENCE event here

v4:
	- return the out_fence_fd in the BUF_QUEUED event(Hans)

v3:	- add WARN_ON_ONCE(q->ordered) on requeueing (Hans)
	- set the OUT_FENCE flag if there is a fence pending (Hans)
	- call fd_install() after vb2_core_qbuf() (Hans)
	- clean up fence if vb2_core_qbuf() fails (Hans)
	- add list to store sync_file and fence for the next queued buffer

v2: check if the queue is ordered.

Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
---
 drivers/media/v4l2-core/videobuf2-core.c | 42 +++++++++++++++++++++++++++++---
 drivers/media/v4l2-core/videobuf2-v4l2.c | 21 +++++++++++++++-
 2 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 8b4f0e9bcb36..2eb5ffa8e028 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -354,6 +354,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
 			vb->planes[plane].length = plane_sizes[plane];
 			vb->planes[plane].min_length = plane_sizes[plane];
 		}
+		vb->out_fence_fd = -1;
 		q->bufs[vb->index] = vb;
 
 		/* Allocate video buffer memory for the MMAP type */
@@ -934,10 +935,26 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
 	case VB2_BUF_STATE_QUEUED:
 		return;
 	case VB2_BUF_STATE_REQUEUEING:
-		if (q->start_streaming_called)
-			__enqueue_in_driver(vb);
-		return;
+
+		if (!vb->out_fence) {
+			if (q->start_streaming_called)
+				__enqueue_in_driver(vb);
+			return;
+		}
+
+		/* Do not allow requeuing with explicit synchronization,
+		 * report it as an error to userspace */
+		state = VB2_BUF_STATE_ERROR;
+
+		/* fall through */
 	default:
+		if (state == VB2_BUF_STATE_ERROR)
+			dma_fence_set_error(vb->out_fence, -EFAULT);
+		dma_fence_signal(vb->out_fence);
+		dma_fence_put(vb->out_fence);
+		vb->out_fence = NULL;
+		vb->out_fence_fd = -1;
+
 		/* Inform any processes that may be waiting for buffers */
 		wake_up(&q->done_wq);
 		break;
@@ -1325,12 +1342,18 @@ EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
 int vb2_setup_out_fence(struct vb2_queue *q, unsigned int index)
 {
 	struct vb2_buffer *vb;
+	u64 context;
 
 	vb = q->bufs[index];
 
 	vb->out_fence_fd = get_unused_fd_flags(O_CLOEXEC);
 
-	vb->out_fence = vb2_fence_alloc(q->out_fence_context);
+	if (q->ordered_in_driver)
+		context = q->out_fence_context;
+	else
+		context = dma_fence_context_alloc(1);
+
+	vb->out_fence = vb2_fence_alloc(context);
 	if (!vb->out_fence) {
 		put_unused_fd(vb->out_fence_fd);
 		return -ENOMEM;
@@ -1594,6 +1617,9 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
 	if (pb)
 		call_void_bufop(q, fill_user_buffer, vb, pb);
 
+	fd_install(vb->out_fence_fd, vb->sync_file->file);
+	vb->sync_file = NULL;
+
 	dprintk(2, "qbuf of buffer %d succeeded\n", vb->index);
 	return 0;
 
@@ -1860,6 +1886,12 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
 	}
 
 	/*
+	 * Renew out-fence context.
+	 */
+	if (q->ordered_in_driver)
+		q->out_fence_context = dma_fence_context_alloc(1);
+
+	/*
 	 * Remove all buffers from videobuf's list...
 	 */
 	INIT_LIST_HEAD(&q->queued_list);
@@ -2191,6 +2223,8 @@ int vb2_core_queue_init(struct vb2_queue *q)
 	spin_lock_init(&q->done_lock);
 	mutex_init(&q->mmap_lock);
 	init_waitqueue_head(&q->done_wq);
+	if (q->ordered_in_driver)
+		q->out_fence_context = dma_fence_context_alloc(1);
 
 	if (q->buf_struct_size == 0)
 		q->buf_struct_size = sizeof(struct vb2_buffer);
diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
index 4c09ea007d90..f2e60d2908ae 100644
--- a/drivers/media/v4l2-core/videobuf2-v4l2.c
+++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
@@ -212,7 +212,13 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb)
 	b->sequence = vbuf->sequence;
 	b->reserved = 0;
 
-	b->fence_fd = -1;
+	if (vb->out_fence) {
+		b->flags |= V4L2_BUF_FLAG_OUT_FENCE;
+		b->fence_fd = vb->out_fence_fd;
+	} else {
+		b->fence_fd = -1;
+	}
+
 	if (vb->in_fence)
 		b->flags |= V4L2_BUF_FLAG_IN_FENCE;
 	else
@@ -489,6 +495,10 @@ int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
 	ret = __verify_planes_array(vb, b);
 	if (!ret)
 		vb2_core_querybuf(q, b->index, b);
+
+	/* Do not return the out-fence fd on querybuf */
+	if (vb->out_fence)
+		b->fence_fd = -1;
 	return ret;
 }
 EXPORT_SYMBOL(vb2_querybuf);
@@ -593,6 +603,15 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
 		}
 	}
 
+	if (b->flags & V4L2_BUF_FLAG_OUT_FENCE) {
+		ret = vb2_setup_out_fence(q, b->index);
+		if (ret) {
+			dprintk(1, "failed to set up out-fence\n");
+			dma_fence_put(fence);
+			return ret;
+		}
+	}
+
 	return vb2_core_qbuf(q, b->index, b, fence);
 }
 EXPORT_SYMBOL_GPL(vb2_qbuf);
-- 
2.13.6