drm/syncobj: allow wait on unsignalled semanticsdrm-syncobj-wait-null

not even close to working

3 files changed, 61 insertions, 5 deletions

diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index a8b7611810fb..ab3c5a3bccb0 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -55,6 +55,39 @@
 #include "drm_internal.h"
 #include <drm/drm_syncobj.h>
 
+static DEFINE_SPINLOCK(drm_syncobj_null_fence_lock);
+
+static const char *drm_syncobj_fence_get_driver_name(struct dma_fence *fence)
+{
+        return "syncobjnull";
+}
+
+static const char *drm_syncobj_fence_get_timeline_name(struct dma_fence *f)
+{
+        return "syncobjnull";
+}
+
+static const struct dma_fence_ops nullsyncobj_fence_ops = {
+	.get_driver_name = drm_syncobj_fence_get_driver_name,
+	.get_timeline_name = drm_syncobj_fence_get_timeline_name,
+	.enable_signaling = NULL,
+	.wait = dma_fence_default_wait,
+	.release = NULL,
+};
+
+static struct dma_fence *drm_syncobj_create_null_fence(void)
+{
+	struct dma_fence *fence;
+	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
+	if (fence == NULL)
+		return NULL;
+
+	dma_fence_init(fence, &nullsyncobj_fence_ops,
+		       &drm_syncobj_null_fence_lock,
+		       0, 0);
+	return fence;
+}
+
 /**
  * drm_syncobj_find - lookup and reference a sync object.
  * @file_private: drm file private pointer
@@ -98,6 +131,10 @@ void drm_syncobj_replace_fence(struct drm_file *file_private,
 		dma_fence_get(fence);
 	old_fence = xchg(&syncobj->fence, fence);
 
+	if (syncobj->null_fence_attached) {
+		dma_fence_signal(old_fence);
+		syncobj->null_fence_attached = false;
+	}
 	dma_fence_put(old_fence);
 }
 EXPORT_SYMBOL(drm_syncobj_replace_fence);
@@ -138,7 +175,7 @@ void drm_syncobj_free(struct kref *kref)
 EXPORT_SYMBOL(drm_syncobj_free);
 
 static int drm_syncobj_create(struct drm_file *file_private,
-			      u32 *handle)
+			      u32 *handle, bool allow_null_wait)
 {
 	int ret;
 	struct drm_syncobj *syncobj;
@@ -149,6 +186,15 @@ static int drm_syncobj_create(struct drm_file *file_private,
 
 	kref_init(&syncobj->refcount);
 
+	if (allow_null_wait) {
+		struct dma_fence *null_fence = drm_syncobj_create_null_fence();
+
+		syncobj->null_fence_attached = true;
+		drm_syncobj_replace_fence(file_private,
+					  syncobj,
+					  null_fence);
+	}
+
 	idr_preload(GFP_KERNEL);
 	spin_lock(&file_private->syncobj_table_lock);
 	ret = idr_alloc(&file_private->syncobj_idr, syncobj, 1, 0, GFP_NOWAIT);
@@ -385,12 +431,13 @@ drm_syncobj_create_ioctl(struct drm_device *dev, void *data,
 	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
 		return -ENODEV;
 
-	/* no valid flags yet */
-	if (args->flags)
+	if (args->flags != 0 &&
+	    args->flags != DRM_SYNCOBJ_CREATE_FLAGS_ALLOW_NULL_WAIT)
 		return -EINVAL;
 
 	return drm_syncobj_create(file_private,
-				  &args->handle);
+				  &args->handle,
+				  !!(args->flags & DRM_SYNCOBJ_CREATE_FLAGS_ALLOW_NULL_WAIT));
 }
 
 int
@@ -539,7 +586,8 @@ drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
 	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
 		return -ENODEV;
 
-	if (args->flags != 0 && args->flags != DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL)
+	if (args->flags != 0 &&
+	    !(args->flags & (DRM_SYNCOBJ_WAIT_NULL_FENCE_SIGNAL|DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL)))
 		return -EINVAL;
 
 	if (args->count_handles == 0)
@@ -568,6 +616,10 @@ drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
 	for (i = 0; i < args->count_handles; i++) {
 		ret = drm_syncobj_fence_get(file_private, handles[i],
 					    &fences[i]);
+		if (ret == -EINVAL && (args->flags & DRM_SYNCOBJ_WAIT_NULL_FENCE_SIGNAL)) {
+			
+		}
+			/* do magic */
 		if (ret)
 			goto err_free_fence_array;
 	}
diff --git a/include/drm/drm_syncobj.h b/include/drm/drm_syncobj.h
index 2c3610a4a074..6f61ffbe10c7 100644
--- a/include/drm/drm_syncobj.h
+++ b/include/drm/drm_syncobj.h
@@ -50,6 +50,8 @@ struct drm_syncobj {
 	 * a file backing for this syncobj.
 	 */
 	struct file *file;
+
+	bool null_fence_attached;
 };
 
 void drm_syncobj_free(struct kref *kref);
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 0757c1a41821..f9fc42dc9f8c 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -698,6 +698,7 @@ struct drm_prime_handle {
 	__s32 fd;
 };
 
+#define DRM_SYNCOBJ_CREATE_FLAGS_ALLOW_NULL_WAIT (1 << 0)
 struct drm_syncobj_create {
 	__u32 handle;
 	__u32 flags;
@@ -719,6 +720,7 @@ struct drm_syncobj_handle {
 };
 
 #define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL (1 << 0)
+#define DRM_SYNCOBJ_WAIT_NULL_FENCE_SIGNAL (1 << 1)
 struct drm_syncobj_wait {
 	__u64 handles;
 	/* absolute timeout */