drm: writeback: Add job prepare and cleanup operations

As writeback jobs contain a framebuffer, drivers may need to prepare and
cleanup them the same way they can prepare and cleanup framebuffers for
planes. Add two new optional connector helper operations,
.prepare_writeback_job() and .cleanup_writeback_job() to support this.

The job prepare operation is called from
drm_atomic_helper_prepare_planes() to avoid a new atomic commit helper
that would need to be called by all drivers not using
drm_atomic_helper_commit(). The job cleanup operation is called from the
existing drm_writeback_cleanup_job() function, invoked both when
destroying the job as part of a aborted commit, or when the job
completes.

The drm_writeback_job structure is extended with a priv field to let
drivers store per-job data, such as mappings related to the writeback
framebuffer.

For internal plumbing reasons the drm_writeback_job structure needs to
store a back-pointer to the drm_writeback_connector. To avoid pushing
too much writeback-specific knowledge to drm_atomic_uapi.c, create a
drm_writeback_set_fb() function, move the writeback job setup code
there, and set the connector backpointer. The prepare_signaling()
function doesn't need to allocate writeback jobs and can ignore
connectors without a job, as it is called after the writeback jobs are
allocated to store framebuffers, and a writeback fence with a
framebuffer is an invalid configuration that gets rejected by the commit
check.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 40ac19848034..f89641216a44 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -2261,10 +2261,21 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_cleanup_done);
 int drm_atomic_helper_prepare_planes(struct drm_device *dev,
 				     struct drm_atomic_state *state)
 {
+	struct drm_connector *connector;
+	struct drm_connector_state *new_conn_state;
 	struct drm_plane *plane;
 	struct drm_plane_state *new_plane_state;
 	int ret, i, j;
 
+	for_each_new_connector_in_state(state, connector, new_conn_state, i) {
+		if (!new_conn_state->writeback_job)
+			continue;
+
+		ret = drm_writeback_prepare_job(new_conn_state->writeback_job);
+		if (ret < 0)
+			return ret;
+	}
+
 	for_each_new_plane_in_state(state, plane, new_plane_state, i) {
 		const struct drm_plane_helper_funcs *funcs;