linux-kernel - [PATCH v5 drm-dp 1/4] drm/hisilicon/hibmc: fix dp probabilistical detect errors after HPD irq

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Message-ID: <20250826021744.3237574-2-shiyongbang@huawei.com>
Date: Tue, 26 Aug 2025 10:17:41 +0800
From: Yongbang Shi <shiyongbang@...wei.com>
To: <xinliang.liu@...aro.org>, <tiantao6@...ilicon.com>,
	<maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
	<tzimmermann@...e.de>, <airlied@...il.com>, <daniel@...ll.ch>,
	<kong.kongxinwei@...ilicon.com>, <dmitry.baryshkov@....qualcomm.com>
CC: <liangjian010@...wei.com>, <chenjianmin@...wei.com>,
	<fengsheng5@...wei.com>, <shiyongbang@...wei.com>, <libaihan@...wei.com>,
	<shenjian15@...wei.com>, <shaojijie@...wei.com>,
	<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 drm-dp 1/4] drm/hisilicon/hibmc: fix dp probabilistical detect errors after HPD irq

From: Baihan Li <libaihan@...wei.com>

The issue is that drm_connector_helper_detect_from_ddc() returns wrong
status when plugging or unplugging the monitor. To perform a DP detect(),
add read_dpcd_cap() and read_sink_count() to detect DP monitor, and 200ms
delay doesn't need anymore.

Fixes: 3c7623fb5bb6 ("drm/hisilicon/hibmc: Enable this hot plug detect of irq feature")
Signed-off-by: Baihan Li <libaihan@...wei.com>
Signed-off-by: Yongbang Shi <shiyongbang@...wei.com>
---
ChangeLog:
v4 -> v5:
  - fix the commit message and DP detect_ctx(), suggested by Dmitry Baryshkov.
---
 drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
index d06832e62e96..123372ae2d40 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
+++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
@@ -12,6 +12,7 @@
 
 #include "hibmc_drm_drv.h"
 #include "dp/dp_hw.h"
+#include "dp/dp_comm.h"
 
 #define DP_MASKED_SINK_HPD_PLUG_INT	BIT(2)
 
@@ -34,7 +35,16 @@ static int hibmc_dp_connector_get_modes(struct drm_connector *connector)
 static int hibmc_dp_detect(struct drm_connector *connector,
 			   struct drm_modeset_acquire_ctx *ctx, bool force)
 {
-	mdelay(200);
+	struct hibmc_dp *dp = to_hibmc_dp(connector);
+	int ret;
+
+	ret = drm_dp_read_dpcd_caps(&dp->aux, dp->dp_dev->dpcd);
+	if (ret)
+		return connector_status_disconnected;
+
+	ret = drm_dp_read_sink_count(&dp->aux);
+	if (ret <= 0)
+		return connector_status_disconnected;
 
 	return drm_connector_helper_detect_from_ddc(connector, ctx, force);
 }
-- 
2.33.0