linux-kernel - [PATCH 2/4] drm/msm/dp: Return early from atomic_enable() if ST_DISCONNECT

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Message-Id: <20250529-hpd_display_off-v1-2-ce33bac2987c@oss.qualcomm.com>
Date: Thu, 29 May 2025 16:13:44 -0700
From: Jessica Zhang <jessica.zhang@....qualcomm.com>
To: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <lumag@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>, Johan Hovold <johan@...nel.org>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Abhinav Kumar <abhinav.kumar@....qualcomm.com>,
        linux-kernel@...r.kernel.org, Yongxing Mou <quic_yongmou@...cinc.com>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>
Subject: [PATCH 2/4] drm/msm/dp: Return early from atomic_enable() if
 ST_DISCONNECT_PENDING

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

The checks in msm_dp_bridge_atomic_enable() for making sure that we are in
ST_DISPLAY_OFF OR ST_MAINLINK_READY seem redundant.

DRM fwk shall not issue any commits if state is not ST_MAINLINK_READY as
msm_dp's atomic_check callback returns a failure if state is not
ST_MAINLINK_READY.

For the ST_DISPLAY_OFF check, its mainly to guard against a scenario that
there is an atomic_enable() without a prior atomic_disable() which once
again should not really happen.

Since it's still possible for the state machine to transition to
ST_DISCONNECT_PENDING between atomic_check() and atomic_commit(), change
this check to return early if hpd_state is ST_DISCONNECT_PENDING.

Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
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 1d7cda62d5fb..f2820f06f5dc 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1512,7 +1512,7 @@ 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 (hpd_state == ST_DISCONNECT_PENDING) {
 		mutex_unlock(&msm_dp_display->event_mutex);
 		return;
 	}

-- 
2.49.0