linux-kernel - [PATCH v3 1/2] drm: allow encoder mode_set even when connectors change for crtc

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Message-ID: <20241211-abhinavk-modeset-fix-v3-1-0de4bf3e7c32@quicinc.com>
Date: Wed, 11 Dec 2024 13:18:42 -0800
From: Jessica Zhang <quic_jesszhan@...cinc.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>
CC: <quic_abhinavk@...cinc.com>, <dri-devel@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>, <dmitry.baryshkov@...aro.org>,
        <robdclark@...il.com>, Jessica Zhang <quic_jesszhan@...cinc.com>
Subject: [PATCH v3 1/2] drm: allow encoder mode_set even when connectors
 change for crtc

From: Abhinav Kumar <quic_abhinavk@...cinc.com>

In certain use-cases, a CRTC could switch between two encoders
and because the mode being programmed on the CRTC remains
the same during this switch, the CRTC's mode_changed remains false.
In such cases, the encoder's mode_set also gets skipped.

Skipping mode_set on the encoder for such cases could cause an issue
because even though the same CRTC mode was being used, the encoder
type could have changed like the CRTC could have switched from a
real time encoder to a writeback encoder OR vice-versa.

Allow encoder's mode_set to happen even when connectors changed on a
CRTC and not just when the mode changed.

Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 5186d2114a503701e228e382cc45180b0c578d0c..32902f77f00dd8b85f03811e6d6da99b6d538afe 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1376,7 +1376,7 @@ crtc_set_mode(struct drm_device *dev, struct drm_atomic_state *old_state)
 		mode = &new_crtc_state->mode;
 		adjusted_mode = &new_crtc_state->adjusted_mode;
 
-		if (!new_crtc_state->mode_changed)
+		if (!new_crtc_state->mode_changed && !new_crtc_state->connectors_changed)
 			continue;
 
 		drm_dbg_atomic(dev, "modeset on [ENCODER:%d:%s]\n",

-- 
2.34.1