linux-kernel - [PATCH 4/4] drm/tidss: Fix enable/disable order

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Message-Id: <20251205-drm-seq-fix-v1-4-fda68fa1b3de@ideasonboard.com>
Date: Fri, 05 Dec 2025 11:51:51 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Dmitry Baryshkov <lumag@...nel.org>, 
 Chun-Kuang Hu <chunkuang.hu@...nel.org>, 
 Philipp Zabel <p.zabel@...gutronix.de>, 
 Matthias Brugger <matthias.bgg@...il.com>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
 Jyri Sarha <jyri.sarha@....fi>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 linux-mediatek@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
 Marek Szyprowski <m.szyprowski@...sung.com>, 
 Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>, 
 Aradhya Bhatia <aradhya.bhatia@...ux.dev>, 
 Linus Walleij <linusw@...nel.org>, Chaoyi Chen <chaoyi.chen@...k-chips.com>, 
 Vicente Bergas <vicencb@...il.com>, 
 Marek Vasut <marek.vasut+renesas@...lbox.org>, 
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, stable@...r.kernel.org
Subject: [PATCH 4/4] drm/tidss: Fix enable/disable order

TI's OLDI and DSI encoders need to be set up before the crtc is enabled,
but the DRM helpers will enable the crtc first. This causes various
issues on TI platforms, like visual artifacts or crtc sync lost
warnings.

Thus drm_atomic_helper_commit_modeset_enables() and
drm_atomic_helper_commit_modeset_disables() cannot be used, as they
enable the crtc before bridges' pre-enable, and disable the crtc after
bridges' post-disable.

Open code the drm_atomic_helper_commit_modeset_enables() and
drm_atomic_helper_commit_modeset_disables(), and first call the bridges'
pre-enables, then crtc enable, then bridges' post-enable (and vice versa
for disable).

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: stable@...r.kernel.org # v6.17+
---
 drivers/gpu/drm/tidss/tidss_kms.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/tidss/tidss_kms.c b/drivers/gpu/drm/tidss/tidss_kms.c
index 86eb5d97410b..8bb93194e5ac 100644
--- a/drivers/gpu/drm/tidss/tidss_kms.c
+++ b/drivers/gpu/drm/tidss/tidss_kms.c
@@ -26,9 +26,33 @@ static void tidss_atomic_commit_tail(struct drm_atomic_state *old_state)
 
 	tidss_runtime_get(tidss);
 
-	drm_atomic_helper_commit_modeset_disables(ddev, old_state);
-	drm_atomic_helper_commit_planes(ddev, old_state, DRM_PLANE_COMMIT_ACTIVE_ONLY);
-	drm_atomic_helper_commit_modeset_enables(ddev, old_state);
+	/*
+	 * TI's OLDI and DSI encoders need to be set up before the crtc is
+	 * enabled. Thus drm_atomic_helper_commit_modeset_enables() and
+	 * drm_atomic_helper_commit_modeset_disables() cannot be used here, as
+	 * they enable the crtc before bridges' pre-enable, and disable the crtc
+	 * after bridges' post-disable.
+	 *
+	 * Open code the functions here and first call the bridges' pre-enables,
+	 * then crtc enable, then bridges' post-enable (and vice versa for
+	 * disable).
+	 */
+
+	drm_atomic_helper_commit_encoder_bridge_disable(ddev, old_state);
+	drm_atomic_helper_commit_crtc_disable(ddev, old_state);
+	drm_atomic_helper_commit_encoder_bridge_post_disable(ddev, old_state);
+
+	drm_atomic_helper_update_legacy_modeset_state(ddev, old_state);
+	drm_atomic_helper_calc_timestamping_constants(old_state);
+	drm_atomic_helper_commit_crtc_set_mode(ddev, old_state);
+
+	drm_atomic_helper_commit_planes(ddev, old_state,
+					DRM_PLANE_COMMIT_ACTIVE_ONLY);
+
+	drm_atomic_helper_commit_encoder_bridge_pre_enable(ddev, old_state);
+	drm_atomic_helper_commit_crtc_enable(ddev, old_state);
+	drm_atomic_helper_commit_encoder_bridge_enable(ddev, old_state);
+	drm_atomic_helper_commit_writebacks(ddev, old_state);
 
 	drm_atomic_helper_commit_hw_done(old_state);
 	drm_atomic_helper_wait_for_flip_done(ddev, old_state);

-- 
2.43.0