[PATCH v8 10/13] [media] vb2: add out-fence support to QBUF

[Gustavo Padovan <gustavo@padovan.org>]

From: Gustavo Padovan <gustavo.padovan@collabora.com>

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.

v9:	- remove in-fences changes from this patch (Alex Courbot)
	- improve fence context creation (Hans Verkuil)
	- clean up out fences if vb2_core_qbuf() fails (Hans Verkuil)

v8:
	- return 0 as fence_fd if OUT_FENCE flag not used (Mauro)
	- fix crash when checking not using fences in vb2_buffer_done()

v7:
	- merge patch that add the infrastructure to out-fences into
	this one (Alex Courbot)
	- Do not install the fd if there is no fence. (Alex Courbot)
	- do not report error on requeueing, just WARN_ON_ONCE() (Hans)

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@collabora.com>
---
 drivers/media/common/videobuf2/videobuf2-core.c | 88 +++++++++++++++++++++++++
 drivers/media/common/videobuf2/videobuf2-v4l2.c | 20 +++++-
 include/media/videobuf2-core.h                  | 25 +++++++
 3 files changed, 132 insertions(+), 1 deletion(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 5de5e35cfc40..dd18a9f345c7 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -25,6 +25,7 @@
 #include <linux/sched.h>
 #include <linux/freezer.h>
 #include <linux/kthread.h>
+#include <linux/sync_file.h>
 
 #include <media/videobuf2-core.h>
 #include <media/v4l2-mc.h>
@@ -357,6 +358,7 @@ 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 +936,22 @@ static void vb2_process_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state
 	case VB2_BUF_STATE_QUEUED:
 		return;
 	case VB2_BUF_STATE_REQUEUEING:
+		/* Requeuing with explicit synchronization, spit warning */
+		WARN_ON_ONCE(vb->out_fence);
+
 		if (q->start_streaming_called)
 			__enqueue_in_driver(vb);
 		return;
 	default:
+		if (vb->out_fence) {
+			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;
@@ -1353,6 +1367,62 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
 }
 EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
 
+static inline const char *vb2_fence_get_driver_name(struct dma_fence *fence)
+{
+	return "vb2_fence";
+}
+
+static inline const char *vb2_fence_get_timeline_name(struct dma_fence *fence)
+{
+	return "vb2_fence_timeline";
+}
+
+static inline bool vb2_fence_enable_signaling(struct dma_fence *fence)
+{
+	return true;
+}
+
+static const struct dma_fence_ops vb2_fence_ops = {
+	.get_driver_name = vb2_fence_get_driver_name,
+	.get_timeline_name = vb2_fence_get_timeline_name,
+	.enable_signaling = vb2_fence_enable_signaling,
+	.wait = dma_fence_default_wait,
+};
+
+int vb2_setup_out_fence(struct vb2_queue *q, unsigned int index)
+{
+	struct vb2_buffer *vb;
+
+	vb = q->bufs[index];
+
+	vb->out_fence_fd = get_unused_fd_flags(O_CLOEXEC);
+
+	if (call_qop(q, is_unordered, q) || !q->queueing_started)
+		q->out_fence_context = dma_fence_context_alloc(1);
+
+	vb->out_fence = kzalloc(sizeof(*vb->out_fence), GFP_KERNEL);
+	if (!vb->out_fence)
+		return -ENOMEM;
+
+	dma_fence_init(vb->out_fence, &vb2_fence_ops, &q->out_fence_lock,
+		       q->out_fence_context, 1);
+	if (!vb->out_fence) {
+		put_unused_fd(vb->out_fence_fd);
+		return -ENOMEM;
+	}
+
+	vb->sync_file = sync_file_create(vb->out_fence);
+	if (!vb->sync_file) {
+		put_unused_fd(vb->out_fence_fd);
+		dma_fence_put(vb->out_fence);
+		vb->out_fence = NULL;
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_setup_out_fence);
+
 /*
  * vb2_start_streaming() - Attempt to start streaming.
  * @q:		videobuf2 queue
@@ -1482,6 +1552,7 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
 	list_add_tail(&vb->queued_entry, &q->queued_list);
 	q->queued_count++;
 	q->waiting_for_buffers = false;
+	q->queueing_started = 1;
 	vb->state = VB2_BUF_STATE_QUEUED;
 	vb->in_fence = in_fence;
 
@@ -1545,6 +1616,11 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
 	if (pb)
 		call_void_bufop(q, fill_user_buffer, vb, pb);
 
+	if (vb->out_fence) {
+		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;
 
@@ -1552,6 +1628,16 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
 	spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
 
 err:
+	if (vb->sync_file) {
+		put_unused_fd(vb->out_fence_fd);
+		vb->out_fence_fd = -1;
+
+		dma_fence_put(vb->out_fence);
+
+		fput(vb->sync_file->file);
+		vb->sync_file = NULL;
+	}
+
 	/* Fill buffer information for the userspace */
 	if (pb)
 		call_void_bufop(q, fill_user_buffer, vb, pb);
@@ -1804,6 +1890,7 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
 	q->start_streaming_called = 0;
 	q->queued_count = 0;
 	q->error = 0;
+	q->queueing_started = 0;
 
 	list_for_each_entry(vb, &q->queued_list, queued_entry) {
 		spin_lock_irqsave(&vb->fence_cb_lock, flags);
@@ -2156,6 +2243,7 @@ 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);
+	spin_lock_init(&q->out_fence_lock);
 
 	q->memory = VB2_MEMORY_UNKNOWN;
 
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 1df5dd01c0cd..ab5b2b71d784 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -217,7 +217,12 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb)
 	b->sequence = vbuf->sequence;
 	b->reserved = 0;
 
-	b->fence_fd = 0;
+	if (b->flags & V4L2_BUF_FLAG_OUT_FENCE) {
+		b->fence_fd = vb->out_fence_fd;
+	} else {
+		b->fence_fd = 0;
+	}
+
 	if (vb->in_fence)
 		b->flags |= V4L2_BUF_FLAG_IN_FENCE;
 	else
@@ -496,6 +501,10 @@ 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);
@@ -600,6 +609,15 @@ 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(in_fence);
+			return ret;
+		}
+	}
+
 	return vb2_core_qbuf(q, b->index, b, in_fence);
 }
 EXPORT_SYMBOL_GPL(vb2_qbuf);
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 59cd9a6ac168..2b9d3433e960 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -260,6 +260,10 @@ struct vb2_buffer {
 	 *			using the buffer (queueing to the driver)
 	 * fence_cb:		fence callback information
 	 * fence_cb_lock:	protect callback signal/remove
+	 * out_fence_fd:	the out_fence_fd to be shared with userspace.
+	 * out_fence:		the out-fence associated with the buffer once
+	 *			it is queued to the driver.
+	 * sync_file:		the sync file to wrap the out fence
 	 */
 	enum vb2_buffer_state	state;
 
@@ -271,6 +275,10 @@ struct vb2_buffer {
 	struct dma_fence_cb	fence_cb;
 	spinlock_t              fence_cb_lock;
 
+	int			out_fence_fd;
+	struct dma_fence	*out_fence;
+	struct sync_file	*sync_file;
+
 #ifdef CONFIG_VIDEO_ADV_DEBUG
 	/*
 	 * Counters for how often these buffer-related ops are
@@ -515,6 +523,9 @@ struct vb2_buf_ops {
  * @last_buffer_dequeued: used in poll() and DQBUF to immediately return if the
  *		last decoded buffer was already dequeued. Set for capture queues
  *		when a buffer with the %V4L2_BUF_FLAG_LAST is dequeued.
+ * @queueing_started: if queueing has started. Currently used to determine
+ *		if an out_fence_context is needed.
+ * @out_fence_context: the fence context for the out fences
  * @fileio:	file io emulator internal data, used only if emulator is active
  * @threadio:	thread io internal data, used only if thread is active
  */
@@ -567,6 +578,10 @@ struct vb2_queue {
 	unsigned int			is_output:1;
 	unsigned int			copy_timestamp:1;
 	unsigned int			last_buffer_dequeued:1;
+	unsigned int			queueing_started:1;
+
+	u64				out_fence_context;
+	spinlock_t			out_fence_lock;
 
 	struct vb2_fileio_data		*fileio;
 	struct vb2_threadio_data	*threadio;
@@ -754,6 +769,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
  */
 int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
 
+/**
+ * vb2_setup_out_fence() - setup new out-fence
+ * @q:		The vb2_queue where to setup it
+ * @index:	index of the buffer
+ *
+ * Setup the file descriptor, the fence and the sync_file for the next
+ * buffer to be queued and add everything to the tail of the q->out_fence_list.
+ */
+int vb2_setup_out_fence(struct vb2_queue *q, unsigned int index);
+
 /**
  * vb2_core_qbuf() - Queue a buffer from userspace
  *
-- 
2.14.3