linux-kernel - [PATCH] drm/msm/dpu: Disable dither in phys encoder cleanup

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Message-ID: <20250211-dither-disable-v1-1-ac2cb455f6b9@quicinc.com>
Date: Tue, 11 Feb 2025 19:59:19 -0800
From: Jessica Zhang <quic_jesszhan@...cinc.com>
To: Rob Clark <robdclark@...il.com>,
        Dmitry Baryshkov
	<dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Simona
 Vetter" <simona@...ll.ch>
CC: <quic_abhinavk@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <freedreno@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>
Subject: [PATCH] drm/msm/dpu: Disable dither in phys encoder cleanup

Disable pingpong dither in dpu_encoder_helper_phys_cleanup().

This avoids the issue where an encoder unknowingly uses dither after
reserving a pingpong block that was previously bound to an encoder that
had enabled dither.

Reported-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Closes: https://lore.kernel.org/all/jr7zbj5w7iq4apg3gofuvcwf4r2swzqjk7sshwcdjll4mn6ctt@l2n3qfpujg3q/
Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
---
This was tested on SC7180 Trogdor by pulling in the concurrent writeback
series [1] and running the IGT kms_writeback@...teback_check_output
subtest.

[1] https://patchwork.freedesktop.org/series/144083/
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
index 5172ab4dea995..48e6e8d74c855 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
@@ -2281,6 +2281,9 @@ void dpu_encoder_helper_phys_cleanup(struct dpu_encoder_phys *phys_enc)
 		}
 	}
 
+	if (phys_enc->hw_pp && phys_enc->hw_pp->ops.setup_dither)
+		phys_enc->hw_pp->ops.setup_dither(phys_enc->hw_pp, NULL);
+
 	/* reset the merge 3D HW block */
 	if (phys_enc->hw_pp && phys_enc->hw_pp->merge_3d) {
 		phys_enc->hw_pp->merge_3d->ops.setup_3d_mode(phys_enc->hw_pp->merge_3d,

---
base-commit: 866e43b945bf98f8e807dfa45eca92f931f3a032
change-id: 20250211-dither-disable-b77b1e31977f

Best regards,
-- 
Jessica Zhang <quic_jesszhan@...cinc.com>