linux-kernel - [PATCH v9 12/13] drm/atomic-helper: Re-order bridge chain pre-enable and post-disable

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Message-Id: <20250209121621.34677-5-aradhya.bhatia@linux.dev>
Date: Sun,  9 Feb 2025 17:46:20 +0530
From: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>,
	Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	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>
Cc: Nishanth Menon <nm@...com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Devarsh Thakkar <devarsht@...com>,
	Praneeth Bajjuri <praneeth@...com>,
	Udit Kumar <u-kumar1@...com>,
	Jayesh Choudhary <j-choudhary@...com>,
	DRI Development List <dri-devel@...ts.freedesktop.org>,
	Linux Kernel List <linux-kernel@...r.kernel.org>,
	Aradhya Bhatia <aradhya.bhatia@...ux.dev>
Subject: [PATCH v9 12/13] drm/atomic-helper: Re-order bridge chain pre-enable and post-disable

Move the bridge pre_enable call before crtc enable, and the bridge
post_disable call after the crtc disable.

The sequence of enable after this patch will look like:

	bridge[n]_pre_enable
	...
	bridge[1]_pre_enable

	crtc_enable
	encoder_enable

	bridge[1]_enable
	...
	bridge[n]_enable

And, the disable sequence for the display pipeline will look like:

	bridge[n]_disable
	...
	bridge[1]_disable

	encoder_disable
	crtc_disable

	bridge[1]_post_disable
	...
	bridge[n]_post_disable

The definition of bridge pre_enable hook says that,
"The display pipe (i.e. clocks and timing signals) feeding this bridge
will not yet be running when this callback is called".

Since CRTC is also a source feeding the bridge, it should not be enabled
before the bridges in the pipeline are pre_enabled. Fix that by
re-ordering the sequence of bridge pre_enable and bridge post_disable.

Acked-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
Signed-off-by: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
---
 drivers/gpu/drm/drm_atomic_helper.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index c9ffca796f32..348ef0c12949 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1298,9 +1298,9 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
 {
 	encoder_bridge_disable(dev, old_state);
 
-	encoder_bridge_post_disable(dev, old_state);
-
 	crtc_disable(dev, old_state);
+
+	encoder_bridge_post_disable(dev, old_state);
 }
 
 /**
@@ -1636,10 +1636,10 @@ encoder_bridge_enable(struct drm_device *dev, struct drm_atomic_state *old_state
 void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,
 					      struct drm_atomic_state *old_state)
 {
-	crtc_enable(dev, old_state);
-
 	encoder_bridge_pre_enable(dev, old_state);
 
+	crtc_enable(dev, old_state);
+
 	encoder_bridge_enable(dev, old_state);
 
 	drm_atomic_helper_commit_writebacks(dev, old_state);
-- 
2.34.1