linux-kernel - [PATCH v2 10/12] drm/msm/dp: Return early from atomic

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Message-Id: <20250808-hpd-refactor-v2-10-7f4e1e741aa3@oss.qualcomm.com>
Date: Fri, 08 Aug 2025 17:35:22 -0700
From: Jessica Zhang <jessica.zhang@....qualcomm.com>
To: Rob Clark <robin.clark@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Dmitry Baryshkov <lumag@...nel.org>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yongxing Mou <quic_yongmou@...cinc.com>
Subject: [PATCH v2 10/12] drm/msm/dp: Return early from atomic_enable() if
 cable is not connected

Replace the ST_MAINLINK_READY check here with a check for sink count.

Since atomic_check() fails if the link isn't ready, we technically don't
need a check against ST_MAINLINK_READY. The hpd_state should also never
really hit ST_DISPLAY_OFF since atomic_enable() shouldn't be called
twice in a row without an atomic_disable() in between.

That being said, it is possible for the cable to be disconnected after
atomic_check() but before atomic_enable(). So let's change this check to
guard against sink_count instead.

Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index dd3fdeaacc91..82f0b6bdbf39 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1444,7 +1444,7 @@ void msm_dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
 	}
 
 	hpd_state = msm_dp_display->hpd_state;
-	if (hpd_state != ST_DISPLAY_OFF && hpd_state != ST_MAINLINK_READY)
+	if (msm_dp_display->link->sink_count == 0)
 		return;
 
 	rc = msm_dp_display_set_mode(dp, &msm_dp_display->msm_dp_mode);

-- 
2.50.1