drm: writeback: Add out-fences for writeback connectors

Add the WRITEBACK_OUT_FENCE_PTR property to writeback connectors, to
enable userspace to get a fence which will signal once the writeback is
complete. It is not allowed to request an out-fence without a
framebuffer attached to the connector.

A timeline is added to drm_writeback_connector for use by the writeback
out-fences.

In the case of a commit failure or DRM_MODE_ATOMIC_TEST_ONLY, the fence
is set to -1.

Changes from v2:
 - Rebase onto Gustavo Padovan's v9 explicit sync series
 - Change out_fence_ptr type to s32 __user *
 - Set *out_fence_ptr to -1 in drm_atomic_connector_set_property
 - Store fence in drm_writeback_job
 Gustavo Padovan:
 - Move out_fence_ptr out of connector_state
 - Signal fence from drm_writeback_signal_completion instead of
   in driver directly

Changes from v3:
 - Rebase onto commit 7e9081c5aac7 ("drm/fence: fix memory overwrite
   when setting out_fence fd") (change out_fence_ptr to s32 __user *,
   for real this time.)
 - Update documentation around WRITEBACK_OUT_FENCE_PTR

Signed-off-by: Brian Starkey <brian.starkey@arm.com>
[rebased and fixed conflicts]
Signed-off-by: Mihail Atanassov <mihail.atanassov@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/229036/

1 files changed, 40 insertions, 1 deletions

diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
index 17cd1feecd7e..a10fe556dfd4 100644
--- a/include/drm/drm_writeback.h
+++ b/include/drm/drm_writeback.h
@@ -50,6 +50,32 @@ struct drm_writeback_connector {
 	 * drm_writeback_signal_completion()
 	 */
 	struct list_head job_queue;
+
+	/**
+	 * @fence_context:
+	 *
+	 * timeline context used for fence operations.
+	 */
+	unsigned int fence_context;
+	/**
+	 * @fence_lock:
+	 *
+	 * spinlock to protect the fences in the fence_context.
+	 */
+	spinlock_t fence_lock;
+	/**
+	 * @fence_seqno:
+	 *
+	 * Seqno variable used as monotonic counter for the fences
+	 * created on the connector's timeline.
+	 */
+	unsigned long fence_seqno;
+	/**
+	 * @timeline_name:
+	 *
+	 * The name of the connector's fence timeline.
+	 */
+	char timeline_name[32];
 };
 
 struct drm_writeback_job {
@@ -75,6 +101,13 @@ struct drm_writeback_job {
 	 * directly, use drm_atomic_set_writeback_fb_for_connector()
 	 */
 	struct drm_framebuffer *fb;
+
+	/**
+	 * @out_fence:
+	 *
+	 * Fence which will signal once the writeback has completed
+	 */
+	struct dma_fence *out_fence;
 };
 
 int drm_writeback_connector_init(struct drm_device *dev,
@@ -87,5 +120,11 @@ void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
 			     struct drm_writeback_job *job);
 
 void drm_writeback_cleanup_job(struct drm_writeback_job *job);
-void drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector);
+
+void
+drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
+				int status);
+
+struct dma_fence *
+drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector);
 #endif