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, 8 insertions, 0 deletions

diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index 5f24329e6927..f4a173c8d79c 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -798,6 +798,14 @@ struct drm_mode_config {
 	 * See also: drm_writeback_connector_init()
 	 */
 	struct drm_property *writeback_pixel_formats_property;
+	/**
+	 * @writeback_out_fence_ptr_property: Property for writeback connectors,
+	 * fd pointer representing the outgoing fences for a writeback
+	 * connector. Userspace should provide a pointer to a value of type s32,
+	 * and then cast that pointer to u64.
+	 * See also: drm_writeback_connector_init()
+	 */
+	struct drm_property *writeback_out_fence_ptr_property;
 
 	/* dumb ioctl parameters */
 	uint32_t preferred_depth, prefer_shadow;