[PATCH] drm/msm/dpu: don't flush a legacy CTL after its interface has stopped

[Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>]

On DPU < 5.0 the CTL latches a flush at the next vsync of the interface
it drives.  dpu_encoder_helper_phys_cleanup() runs after the video
encoder has switched the timing engine off, and still flushes the mixers
it has just reset, so the flush is never taken: the bits stay pending in
CTL_FLUSH, where a CTL soft reset doesn't clear them either.

The next display on that CTL then waits for a flush which can't
complete.  On SDA660, going back to fbcon from a two-mixer mode leaves
the LM_1 bit pending, and every following frame of the single-mixer
mode times out:

  [dpu error]vblank timeout: 80
  [dpu error]wait for commit done returned -110

Only trigger the flush from the teardown on DPU >= 5.0.  The legacy CTL
gets its registers flushed by its next user, as downstream does, which
rewrites CTL_TOP without a flush when it stops a CTL.

Fixes: 22cb02bc96ff ("drm/msm/disp/dpu: reset the datapath after timing engine disable")
Assisted-by: LLM
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
index 1f20695f81e3..5a06a0fbc7e1 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
@@ -2339,8 +2339,11 @@ void dpu_encoder_helper_phys_cleanup(struct dpu_encoder_phys *phys_enc)
 	if (ctl->ops.reset_intf_cfg)
 		ctl->ops.reset_intf_cfg(ctl, &intf_cfg);
 
-	ctl->ops.trigger_flush(ctl);
-	ctl->ops.trigger_start(ctl);
+	/* a legacy CTL latches its flush at the vsync of a stopped interface */
+	if (phys_enc->dpu_kms->catalog->mdss_ver->core_major_ver >= 5) {
+		ctl->ops.trigger_flush(ctl);
+		ctl->ops.trigger_start(ctl);
+	}
 	ctl->ops.clear_pending_flush(ctl);
 }
 

---
base-commit: 5e4a3f7b262060d70cfdc7889cfe0f4aba9ea3fc
change-id: 20261002-encoder-flush-old-ctl-45d4bbb489d8

Best regards,
--  
With best wishes
Dmitry