[v5,13/14] drm/msm/dpu: Reorder encoder kickoff for CWB

Commit Message

Jessica Zhang Jan. 29, 2025, 3:20 a.m. UTC

Add a helper that will handle the correct order of the encoder kickoffs
for concurrent writeback.

For concurrent writeback, the realtime encoder must always kickoff last
as it will call the trigger flush and start.

This avoids the following scenario where the writeback encoder
increments the pending kickoff count after the WB_DONE interrupt is
fired:

If the realtime encoder is kicked off first, the encoder kickoff will
flush/start the encoder and increment the pending kickoff count. The
WB_DONE interrupt then fires (before the writeback encoder is kicked
off). When the writeback encoder enters its kickoff, it will skip the
flush/start (due to CWB being enabled) and hit a frame done timeout
as the frame was kicked off (and the WB_DONE interrupt fired) without
the pending kickoff count being incremented.

In addition, the writeback timer should only start after the realtime
encoder is kicked off to ensure that we don't get timeouts when the
system has a heavy load (ex. when debug logs are enabled)

Reviewed-by: Dmitry Baryshkov <[e-mail]>
Reviewed-by: Abhinav Kumar <[e-mail]>
Signed-off-by: Jessica Zhang <[e-mail]>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 74 ++++++++++++++++++++++++++------
 1 file changed, 60 insertions(+), 14 deletions(-)

Patch

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index 0f8b220b52cec6c6844d3f5e5d924d47c55eb65b..5eabeb1ae4208b707be2413afcda9fa5ed1a2f65 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -953,6 +953,45 @@  static int _dpu_crtc_wait_for_frame_done(struct drm_crtc *crtc)
 	return rc;
 }
 
+static int dpu_crtc_kickoff_clone_mode(struct drm_crtc *crtc)
+{
+	struct drm_encoder *encoder;
+	struct drm_encoder *rt_encoder = NULL, *wb_encoder;
+	struct dpu_kms *dpu_kms = _dpu_crtc_get_kms(crtc);
+
+	/* Find encoder for real time display */
+	drm_for_each_encoder_mask(encoder, crtc->dev,
+				  crtc->state->encoder_mask) {
+		if (encoder->encoder_type == DRM_MODE_ENCODER_VIRTUAL)
+			wb_encoder = encoder;
+		else
+			rt_encoder = encoder;
+	}
+
+	if (!rt_encoder || !wb_encoder) {
+		DRM_DEBUG_ATOMIC("real time or wb encoder not found\n");
+		return -EINVAL;
+	}
+
+	dpu_encoder_prepare_for_kickoff(wb_encoder);
+	dpu_encoder_prepare_for_kickoff(rt_encoder);
+
+	dpu_vbif_clear_errors(dpu_kms);
+
+	/*
+	 * Kickoff real time encoder last as it's the encoder that
+	 * will do the flush
+	 */
+	dpu_encoder_kickoff(wb_encoder);
+	dpu_encoder_kickoff(rt_encoder);
+
+	/* Don't start frame done timers until the kickoffs have finished */
+	dpu_encoder_start_frame_done_timer(wb_encoder);
+	dpu_encoder_start_frame_done_timer(rt_encoder);
+
+	return 0;
+}
+
 /**
  * dpu_crtc_commit_kickoff - trigger kickoff of the commit for this crtc
  * @crtc: Pointer to drm crtc object
@@ -981,13 +1020,27 @@  void dpu_crtc_commit_kickoff(struct drm_crtc *crtc)
 			goto end;
 		}
 	}
-	/*
-	 * Encoder will flush/start now, unless it has a tx pending. If so, it
-	 * may delay and flush at an irq event (e.g. ppdone)
-	 */
-	drm_for_each_encoder_mask(encoder, crtc->dev,
-				  crtc->state->encoder_mask)
-		dpu_encoder_prepare_for_kickoff(encoder);
+
+	if (drm_crtc_in_clone_mode(crtc->state)) {
+		if (dpu_crtc_kickoff_clone_mode(crtc))
+			goto end;
+	} else {
+		/*
+		 * Encoder will flush/start now, unless it has a tx pending.
+		 * If so, it may delay and flush at an irq event (e.g. ppdone)
+		 */
+		drm_for_each_encoder_mask(encoder, crtc->dev,
+				crtc->state->encoder_mask)
+			dpu_encoder_prepare_for_kickoff(encoder);
+
+		dpu_vbif_clear_errors(dpu_kms);
+
+		drm_for_each_encoder_mask(encoder, crtc->dev,
+				crtc->state->encoder_mask) {
+			dpu_encoder_kickoff(encoder);
+			dpu_encoder_start_frame_done_timer(encoder);
+		}
+	}
 
 	if (atomic_inc_return(&dpu_crtc->frame_pending) == 1) {
 		/* acquire bandwidth and other resources */
@@ -997,13 +1050,6 @@  void dpu_crtc_commit_kickoff(struct drm_crtc *crtc)
 
 	dpu_crtc->play_count++;
 
-	dpu_vbif_clear_errors(dpu_kms);
-
-	drm_for_each_encoder_mask(encoder, crtc->dev, crtc->state->encoder_mask) {
-		dpu_encoder_kickoff(encoder);
-		dpu_encoder_start_frame_done_timer(encoder);
-	}
-
 	reinit_completion(&dpu_crtc->frame_done_comp);
 
 end: