[PATCH 3/4] drm/vc4: Export fence through syncobj

[Stefan Schake]

Allow specifying a syncobj on render job submission where we store the
fence for the job. This gives userland flexible access to the fence.

Signed-off-by: Stefan Schake <stschake at gmail.com>
---
 drivers/gpu/drm/vc4/vc4_gem.c | 38 +++++++++++++++++++++++++++++++++++---
 include/uapi/drm/vc4_drm.h    | 13 +++++++++++++
 2 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_gem.c b/drivers/gpu/drm/vc4/vc4_gem.c
index 232363488125..b39515a4ddcb 100644
--- a/drivers/gpu/drm/vc4/vc4_gem.c
+++ b/drivers/gpu/drm/vc4/vc4_gem.c
@@ -656,7 +656,8 @@ vc4_lock_bo_reservations(struct drm_device *dev,
  */
 static int
 vc4_queue_submit(struct drm_device *dev, struct vc4_exec_info *exec,
-		 struct ww_acquire_ctx *acquire_ctx)
+		 struct ww_acquire_ctx *acquire_ctx,
+		 struct drm_syncobj *out_sync)
 {
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct vc4_exec_info *renderjob;
@@ -679,6 +680,9 @@ vc4_queue_submit(struct drm_device *dev, struct vc4_exec_info *exec,
 	fence->seqno = exec->seqno;
 	exec->fence = &fence->base;
 
+	if (out_sync)
+		drm_syncobj_replace_fence(out_sync, exec->fence);
+
 	vc4_update_bo_seqnos(exec, seqno);
 
 	vc4_unlock_bo_reservations(dev, exec, acquire_ctx);
@@ -1114,6 +1118,7 @@ vc4_submit_cl_ioctl(struct drm_device *dev, void *data,
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct vc4_file *vc4file = file_priv->driver_priv;
 	struct drm_vc4_submit_cl *args = data;
+	struct drm_syncobj *out_sync = NULL;
 	struct vc4_exec_info *exec;
 	struct ww_acquire_ctx acquire_ctx;
 	struct dma_fence *in_fence;
@@ -1123,11 +1128,17 @@ vc4_submit_cl_ioctl(struct drm_device *dev, void *data,
 			     VC4_SUBMIT_CL_FIXED_RCL_ORDER |
 			     VC4_SUBMIT_CL_RCL_ORDER_INCREASING_X |
 			     VC4_SUBMIT_CL_RCL_ORDER_INCREASING_Y |
-			     VC4_SUBMIT_CL_IMPORT_SYNCOBJ)) != 0) {
+			     VC4_SUBMIT_CL_IMPORT_SYNCOBJ |
+			     VC4_SUBMIT_CL_EXPORT_SYNCOBJ)) != 0) {
 		DRM_DEBUG("Unknown flags: 0x%02x\n", args->flags);
 		return -EINVAL;
 	}
 
+	if (args->pad2 != 0) {
+		DRM_DEBUG("->pad2 must be set to zero\n");
+		return -EINVAL;
+	}
+
 	exec = kcalloc(1, sizeof(*exec), GFP_KERNEL);
 	if (!exec) {
 		DRM_ERROR("malloc failure on exec struct\n");
@@ -1202,12 +1213,33 @@ vc4_submit_cl_ioctl(struct drm_device *dev, void *data,
 	if (ret)
 		goto fail;
 
+	if (args->flags & VC4_SUBMIT_CL_EXPORT_SYNCOBJ) {
+		out_sync = drm_syncobj_find(file_priv, args->out_sync);
+		if (!out_sync) {
+			ret = -EINVAL;
+			goto fail;
+		}
+
+		/* We replace the fence in out_sync in vc4_queue_submit since
+		 * the render job could execute immediately after that call.
+		 * If it finishes before our ioctl processing resumes the
+		 * render job fence could already have been freed.
+		 */
+	}
+
 	/* Clear this out of the struct we'll be putting in the queue,
 	 * since it's part of our stack.
 	 */
 	exec->args = NULL;
 
-	ret = vc4_queue_submit(dev, exec, &acquire_ctx);
+	ret = vc4_queue_submit(dev, exec, &acquire_ctx, out_sync);
+
+	/* The syncobj isn't part of the exec data and we need to free our
+	 * reference even if job submission failed.
+	 */
+	if (out_sync)
+		drm_syncobj_put(out_sync);
+
 	if (ret)
 		goto fail;
 
diff --git a/include/uapi/drm/vc4_drm.h b/include/uapi/drm/vc4_drm.h
index 389f21931c25..3a2ef9b5b60b 100644
--- a/include/uapi/drm/vc4_drm.h
+++ b/include/uapi/drm/vc4_drm.h
@@ -174,6 +174,7 @@ struct drm_vc4_submit_cl {
 #define VC4_SUBMIT_CL_RCL_ORDER_INCREASING_X		(1 << 2)
 #define VC4_SUBMIT_CL_RCL_ORDER_INCREASING_Y		(1 << 3)
 #define VC4_SUBMIT_CL_IMPORT_SYNCOBJ			(1 << 4)
+#define VC4_SUBMIT_CL_EXPORT_SYNCOBJ			(1 << 5)
 	__u32 flags;
 
 	/* Returned value of the seqno of this render job (for the
@@ -189,6 +190,18 @@ struct drm_vc4_submit_cl {
 	 * syncobj is signalled.
 	 */
 	__u32 in_sync;
+
+	/* Syncobj handle to export fence to. Set together with EXPORT_SYNCOBJ
+	 * flag. If set, the fence in the syncobj will be replaced with a fence
+	 * that signals upon completion of this render job.
+	 */
+	__u32 out_sync;
+
+	/* Unused field to align this struct on 64 bits. Must be set to 0.
+	 * If one ever needs to add an u32 field to this struct, this field
+	 * can be used.
+	 */
+	__u32 pad2;
 };
 
 /**
-- 
2.14.1