linux-kernel - [PATCH 1/4] drm/msm/dp: remove redundant checks related to ST_DISPLAY_OFF in plug/irq

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Message-Id: <20250529-hpd_display_off-v1-1-ce33bac2987c@oss.qualcomm.com>
Date: Thu, 29 May 2025 16:13:43 -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>,
        Dmitry Baryshkov <lumag@...nel.org>
Subject: [PATCH 1/4] drm/msm/dp: remove redundant checks related to
 ST_DISPLAY_OFF in plug/irq_ipd handlers

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

In commit 8ede2ecc3e5ee ("drm/msm/dp: Add DP compliance tests on Snapdragon
Chipsets"), checks were introduced to avoid handling any plug or irq hpd
events in ST_DISPLAY_OFF state.

Even if we do get hpd events, after the bridge was disabled,
it should get handled. Moreover, its unclear under what circumstances
these events will fire because ST_DISPLAY_OFF means that the link was
still connected but only the bridge was disabled. If the link was
untouched, then interrupts shouldn't fire.

Even in the case of the DP compliance equipment, it should be raising these
interrupts during the start of the test which is usually accompanied with
either a HPD pulse or a IRQ HPD but after the bridge is disabled it should
be fine to handle these anyway. In the absence of a better reason to keep
these checks, drop these and if any other issues do arise, it should be
handled in a different way.

Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 386c4669c831..1d7cda62d5fb 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -579,11 +579,6 @@ static int msm_dp_hpd_plug_handle(struct msm_dp_display_private *dp, u32 data)
 	drm_dbg_dp(dp->drm_dev, "Before, type=%d hpd_state=%d\n",
 			dp->msm_dp_display.connector_type, state);
 
-	if (state == ST_DISPLAY_OFF) {
-		mutex_unlock(&dp->event_mutex);
-		return 0;
-	}
-
 	if (state == ST_MAINLINK_READY || state == ST_CONNECTED) {
 		mutex_unlock(&dp->event_mutex);
 		return 0;
@@ -706,11 +701,6 @@ static int msm_dp_irq_hpd_handle(struct msm_dp_display_private *dp, u32 data)
 	drm_dbg_dp(dp->drm_dev, "Before, type=%d hpd_state=%d\n",
 			dp->msm_dp_display.connector_type, state);
 
-	if (state == ST_DISPLAY_OFF) {
-		mutex_unlock(&dp->event_mutex);
-		return 0;
-	}
-
 	if (state == ST_MAINLINK_READY || state == ST_DISCONNECT_PENDING) {
 		/* wait until ST_CONNECTED */
 		msm_dp_add_event(dp, EV_IRQ_HPD_INT, 0, 1); /* delay = 1 */

-- 
2.49.0