drm: introduce sync objects (v4)

Sync objects are new toplevel drm object, that contain a
pointer to a fence. This fence can be updated via command
submission ioctls via drivers.

There is also a generic wait obj API modelled on the vulkan
wait API (with code modelled on some amdgpu code).

These objects can be converted to an opaque fd that can be
passes between processes.

v2: rename reference/unreference to put/get (Chris)
fix leaked reference (David Zhou)
drop mutex in favour of cmpxchg (Chris)
v3: cleanups from danvet, rebase on drm_fops rename
check fd_flags is 0 in ioctls.
v4: export find/free, change replace fence to take a
syncobj. In order to support lookup first, replace
later semantics which seem in the end to be cleaner.

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>

4 files changed, 120 insertions, 0 deletions

diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 18f3181674e8..d855f9ae41a8 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -53,6 +53,7 @@ struct drm_mode_create_dumb;
 #define DRIVER_RENDER			0x8000
 #define DRIVER_ATOMIC			0x10000
 #define DRIVER_KMS_LEGACY_CONTEXT	0x20000
+#define DRIVER_SYNCOBJ                  0x40000
 
 /**
  * struct drm_driver - DRM driver structure
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index d66f7ee07fb5..0e0c868451a5 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -232,6 +232,11 @@ struct drm_file {
 	/** @table_lock: Protects @object_idr. */
 	spinlock_t table_lock;
 
+	/** @syncobj_idr: Mapping of sync object handles to object pointers. */
+	struct idr syncobj_idr;
+	/** @syncobj_table_lock: Protects @syncobj_idr. */
+	spinlock_t syncobj_table_lock;
+
 	/** @filp: Pointer to the core file structure. */
 	struct file *filp;
 
diff --git a/include/drm/drm_syncobj.h b/include/drm/drm_syncobj.h
new file mode 100644
index 000000000000..2c3610a4a074
--- /dev/null
+++ b/include/drm/drm_syncobj.h
@@ -0,0 +1,90 @@
+/*
+ * Copyright © 2017 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *
+ */
+#ifndef __DRM_SYNCOBJ_H__
+#define __DRM_SYNCOBJ_H__
+
+#include "linux/dma-fence.h"
+
+/**
+ * struct drm_syncobj - sync object.
+ *
+ * This structure defines a generic sync object which wraps a dma fence.
+ */
+struct drm_syncobj {
+	/**
+	 * @refcount:
+	 *
+	 * Reference count of this object.
+	 */
+	struct kref refcount;
+	/**
+	 * @fence:
+	 * NULL or a pointer to the fence bound to this object.
+	 */
+	struct dma_fence *fence;
+	/**
+	 * @file:
+	 * a file backing for this syncobj.
+	 */
+	struct file *file;
+};
+
+void drm_syncobj_free(struct kref *kref);
+
+/**
+ * drm_syncobj_get - acquire a syncobj reference
+ * @obj: sync object
+ *
+ * This acquires additional reference to @obj. It is illegal to call this
+ * without already holding a reference. No locks required.
+ */
+static inline void
+drm_syncobj_get(struct drm_syncobj *obj)
+{
+	kref_get(&obj->refcount);
+}
+
+/**
+ * drm_syncobj_put - release a reference to a sync object.
+ * @obj: sync object.
+ */
+static inline void
+drm_syncobj_put(struct drm_syncobj *obj)
+{
+	kref_put(&obj->refcount, drm_syncobj_free);
+}
+
+struct drm_syncobj *drm_syncobj_find(struct drm_file *file_private,
+				     u32 handle);
+void drm_syncobj_replace_fence(struct drm_file *file_private,
+			       struct drm_syncobj *syncobj,
+			       struct dma_fence *fence);
+int drm_syncobj_fence_get(struct drm_file *file_private,
+			  u32 handle,
+			  struct dma_fence **fence);
+void drm_syncobj_free(struct kref *kref);
+
+#endif
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 42d9f64ce416..96c5c789e73d 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -648,6 +648,7 @@ struct drm_gem_open {
 #define DRM_CAP_ADDFB2_MODIFIERS	0x10
 #define DRM_CAP_PAGE_FLIP_TARGET	0x11
 #define DRM_CAP_CRTC_IN_VBLANK_EVENT	0x12
+#define DRM_CAP_SYNCOBJ		0x13
 
 /** DRM_IOCTL_GET_CAP ioctl argument type */
 struct drm_get_cap {
@@ -697,6 +698,24 @@ struct drm_prime_handle {
 	__s32 fd;
 };
 
+struct drm_syncobj_create {
+	__u32 handle;
+	__u32 flags;
+};
+
+struct drm_syncobj_destroy {
+	__u32 handle;
+	__u32 pad;
+};
+
+struct drm_syncobj_handle {
+	__u32 handle;
+	__u32 flags;
+
+	__s32 fd;
+	__u32 pad;
+};
+
 #if defined(__cplusplus)
 }
 #endif
@@ -815,6 +834,11 @@ extern "C" {
 #define DRM_IOCTL_MODE_CREATEPROPBLOB	DRM_IOWR(0xBD, struct drm_mode_create_blob)
 #define DRM_IOCTL_MODE_DESTROYPROPBLOB	DRM_IOWR(0xBE, struct drm_mode_destroy_blob)
 
+#define DRM_IOCTL_SYNCOBJ_CREATE	DRM_IOWR(0xBF, struct drm_syncobj_create)
+#define DRM_IOCTL_SYNCOBJ_DESTROY	DRM_IOWR(0xC0, struct drm_syncobj_destroy)
+#define DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD	DRM_IOWR(0xC1, struct drm_syncobj_handle)
+#define DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE	DRM_IOWR(0xC2, struct drm_syncobj_handle)
+
 /**
  * Device specific ioctls should only be in their respective headers
  * The device specific ioctl range is from 0x40 to 0x9f.