linux-kernel - [PATCH AUTOSEL 5.15 01/12] drm: allow encoder mode

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Message-Id: <20250403192001.2682149-1-sashal@kernel.org>
Date: Thu,  3 Apr 2025 15:19:50 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>,
	Jessica Zhang <quic_jesszhan@...cinc.com>,
	Maxime Ripard <mripard@...nel.org>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Sasha Levin <sashal@...nel.org>,
	maarten.lankhorst@...ux.intel.com,
	tzimmermann@...e.de,
	airlied@...il.com,
	simona@...ll.ch,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.15 01/12] drm: allow encoder mode_set even when connectors change for crtc

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

[ Upstream commit 7e182cb4f5567f53417b762ec0d679f0b6f0039d ]

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>
Reviewed-by: Maxime Ripard <mripard@...nel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241211-abhinavk-modeset-fix-v3-1-0de4bf3e7c32@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 2c3883d79f531..bd01d925769db 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1279,7 +1279,7 @@ 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_DEBUG_ATOMIC("modeset on [ENCODER:%d:%s]\n",
-- 
2.39.5