[PATCH] drm/komeda: Skips the invalid writeback job

["Lowry Li (Arm Technology China)" <Lowry.Li@arm.com>]

Current DRM-CORE accepts the writeback_job with a empty fb, but that
is an invalid job for HW, so need to skip it when commit it to HW.

Signed-off-by: Lowry Li (Arm Technology China) <lowry.li@arm.com>
---
 drivers/gpu/drm/arm/display/komeda/komeda_crtc.c         | 2 +-
 drivers/gpu/drm/arm/display/komeda/komeda_wb_connector.c | 9 ++++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
index 2fed1f6..372e99a 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
@@ -265,7 +265,7 @@ void komeda_crtc_handle_event(struct komeda_crtc *kcrtc,
 		komeda_pipeline_update(slave, old->state);
 
 	conn_st = wb_conn ? wb_conn->base.base.state : NULL;
-	if (conn_st && conn_st->writeback_job)
+	if (conn_st && conn_st->writeback_job && conn_st->writeback_job->fb)
 		drm_writeback_queue_job(&wb_conn->base, conn_st);
 
 	/* step 2: notify the HW to kickoff the update */
diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_wb_connector.c b/drivers/gpu/drm/arm/display/komeda/komeda_wb_connector.c
index 9787745..8e2ef63 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_wb_connector.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_wb_connector.c
@@ -52,9 +52,16 @@
 	struct komeda_data_flow_cfg dflow;
 	int err;
 
-	if (!writeback_job || !writeback_job->fb)
+	if (!writeback_job)
 		return 0;
 
+	if (!writeback_job->fb) {
+		if (writeback_job->out_fence)
+			DRM_DEBUG_ATOMIC("Out fence required on a invalid writeback job.\n");
+
+		return writeback_job->out_fence ? -EINVAL : 0;
+	}
+
 	if (!crtc_st->active) {
 		DRM_DEBUG_ATOMIC("Cannot write the composition result out on a inactive CRTC.\n");
 		return -EINVAL;
-- 
1.9.1