From: Baihan Li <libaihan@huawei.com>

The issue is that drm_connector_helper_detect_from_ddc() returns wrong
status when plugging or unplugging the monitor. Use HPD pin status in
DP's detect_ctx() for real physcal monitor in/out, and implementation
a complete DP detection including read DPCD, check if it's a branch
device and its sink count for different situations.

Fixes: 3c7623fb5bb6 ("drm/hisilicon/hibmc: Enable this hot plug detect of irq feature")
Signed-off-by: Baihan Li <libaihan@huawei.com>
Signed-off-by: Yongbang Shi <shiyongbang@huawei.com>
---
ChangeLog:
v6 -> v7:
  - add the check about branch devices, suggested by Dmitry Baryshkov.
v5 -> v6:
  - use HPD status in DP detect_ctx(), suggested by Dmitry Baryshkov.
v4 -> v5:
  - fix the commit message and DP detect_ctx(), suggested by Dmitry Baryshkov.
---
 drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h  |  3 ++
 drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c    | 12 +++++++
 drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h    |  6 ++++
 drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h   |  3 ++
 .../gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c    | 34 +++++++++++++++++--
 5 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h
index 4add05c7f161..7954a883435c 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h
@@ -40,6 +40,9 @@ struct hibmc_dp_dev {
 	struct mutex lock; /* protects concurrent RW in hibmc_dp_reg_write_field() */
 	struct hibmc_dp_link link;
 	u8 dpcd[DP_RECEIVER_CAP_SIZE];
+	struct drm_dp_desc desc;
+	bool is_branch;
+	int hpd_status;
 	void __iomem *serdes_base;
 };
 
diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
index 8f0daec7d174..bd3d73075629 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
@@ -2,6 +2,7 @@
 // Copyright (c) 2024 Hisilicon Limited.
 
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/delay.h>
 #include "dp_config.h"
 #include "dp_comm.h"
@@ -305,3 +306,14 @@ void hibmc_dp_set_cbar(struct hibmc_dp *dp, const struct hibmc_dp_cbar_cfg *cfg)
 	hibmc_dp_reg_write_field(dp_dev, HIBMC_DP_COLOR_BAR_CTRL, BIT(0), cfg->enable);
 	writel(HIBMC_DP_SYNC_EN_MASK, dp_dev->base + HIBMC_DP_TIMING_SYNC_CTRL);
 }
+
+void hibmc_dp_update_hpd_status(struct hibmc_dp *dp)
+{
+	int status;
+
+	readl_poll_timeout(dp->dp_dev->base + HIBMC_DP_HPD_STATUS, status,
+			   FIELD_GET(HIBMC_DP_HPD_CUR_STATE, status) != dp->dp_dev->hpd_status,
+			   1000, 100000); /* DP spec says 100ms */
+
+	dp->dp_dev->hpd_status = FIELD_GET(HIBMC_DP_HPD_CUR_STATE, status);
+}
diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
index 665f5b166dfb..1e2214aece6a 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
@@ -14,6 +14,11 @@
 
 struct hibmc_dp_dev;
 
+enum hibmc_hpd_status {
+	HIBMC_HPD_OUT,
+	HIBMC_HPD_IN,
+};
+
 enum hibmc_dp_cbar_pattern {
 	CBAR_COLOR_BAR,
 	CBAR_WHITE,
@@ -60,5 +65,6 @@ void hibmc_dp_reset_link(struct hibmc_dp *dp);
 void hibmc_dp_hpd_cfg(struct hibmc_dp *dp);
 void hibmc_dp_enable_int(struct hibmc_dp *dp);
 void hibmc_dp_disable_int(struct hibmc_dp *dp);
+void hibmc_dp_update_hpd_status(struct hibmc_dp *dp);
 
 #endif
diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
index 394b1e933c3a..64306abcd986 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
@@ -24,6 +24,9 @@
 #define HIBMC_DP_CFG_AUX_READY_DATA_BYTE	GENMASK(16, 12)
 #define HIBMC_DP_CFG_AUX			GENMASK(24, 17)
 
+#define HIBMC_DP_HPD_STATUS			0x98
+#define HIBMC_DP_HPD_CUR_STATE		GENMASK(7, 4)
+
 #define HIBMC_DP_PHYIF_CTRL0			0xa0
 #define HIBMC_DP_CFG_SCRAMBLE_EN		BIT(0)
 #define HIBMC_DP_CFG_PAT_SEL			GENMASK(7, 4)
diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
index d06832e62e96..6792cd0b64b2 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)
 
@@ -34,9 +35,36 @@ 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);
+	struct hibmc_dp_dev *dp_dev = dp->dp_dev;
+	int ret;
+
+	if (dp->irq_status) {
+		if (dp_dev->hpd_status != HIBMC_HPD_IN)
+			return connector_status_disconnected;
+	}
+
+	ret = drm_dp_read_dpcd_caps(dp_dev->aux, dp_dev->dpcd);
+	if (ret)
+		return connector_status_disconnected;
+
+	dp_dev->is_branch = drm_dp_is_branch(dp_dev->dpcd);
 
-	return drm_connector_helper_detect_from_ddc(connector, ctx, force);
+	ret = drm_dp_read_desc(dp_dev->aux, &dp_dev->desc, dp_dev->is_branch);
+	if (ret)
+		return connector_status_disconnected;
+
+	if (!dp_dev->is_branch)
+		return connector_status_connected;
+
+	if (drm_dp_read_sink_count_cap(connector, dp_dev->dpcd, &dp_dev->desc) &&
+	    dp_dev->dpcd[DP_DOWNSTREAM_PORT_0] & DP_DS_PORT_HPD) {
+		ret = drm_dp_read_sink_count(dp_dev->aux);
+		if (ret > 0)
+			return connector_status_connected;
+	}
+
+	return connector_status_disconnected;
 }
 
 static const struct drm_connector_helper_funcs hibmc_dp_conn_helper_funcs = {
@@ -128,6 +156,8 @@ irqreturn_t hibmc_dp_hpd_isr(int irq, void *arg)
 		hibmc_dp_reset_link(&priv->dp);
 	}
 
+	hibmc_dp_update_hpd_status(&priv->dp);
+
 	if (dev->registered)
 		drm_connector_helper_hpd_irq_event(&priv->dp.connector);
 
-- 
2.33.0

Hi Yongbang,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linus/master v6.17-rc7 next-20250923]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Yongbang-Shi/drm-hisilicon-hibmc-fix-dp-probabilistical-detect-errors-after-HPD-irq/20250923-211652
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20250923130411.2522339-2-shiyongbang%40huawei.com
patch subject: [PATCH v7 drm-dp 1/4] drm/hisilicon/hibmc: fix dp probabilistical detect errors after HPD irq
config: s390-randconfig-001-20250924 (https://download.01.org/0day-ci/archive/20250924/202509241625.o4mNleVb-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 8.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250924/202509241625.o4mNleVb-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509241625.o4mNleVb-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c: In function 'hibmc_dp_detect':
>> drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c:61:18: warning: array subscript 128 is above array bounds of 'u8[15]' {aka 'unsigned char[15]'} [-Warray-bounds]
         dp_dev->dpcd[DP_DOWNSTREAM_PORT_0] & DP_DS_PORT_HPD) {
         ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~


vim +61 drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c

    34	
    35	static int hibmc_dp_detect(struct drm_connector *connector,
    36				   struct drm_modeset_acquire_ctx *ctx, bool force)
    37	{
    38		struct hibmc_dp *dp = to_hibmc_dp(connector);
    39		struct hibmc_dp_dev *dp_dev = dp->dp_dev;
    40		int ret;
    41	
    42		if (dp->irq_status) {
    43			if (dp_dev->hpd_status != HIBMC_HPD_IN)
    44				return connector_status_disconnected;
    45		}
    46	
    47		ret = drm_dp_read_dpcd_caps(dp_dev->aux, dp_dev->dpcd);
    48		if (ret)
    49			return connector_status_disconnected;
    50	
    51		dp_dev->is_branch = drm_dp_is_branch(dp_dev->dpcd);
    52	
    53		ret = drm_dp_read_desc(dp_dev->aux, &dp_dev->desc, dp_dev->is_branch);
    54		if (ret)
    55			return connector_status_disconnected;
    56	
    57		if (!dp_dev->is_branch)
    58			return connector_status_connected;
    59	
    60		if (drm_dp_read_sink_count_cap(connector, dp_dev->dpcd, &dp_dev->desc) &&
  > 61		    dp_dev->dpcd[DP_DOWNSTREAM_PORT_0] & DP_DS_PORT_HPD) {
    62			ret = drm_dp_read_sink_count(dp_dev->aux);
    63			if (ret > 0)
    64				return connector_status_connected;
    65		}
    66	
    67		return connector_status_disconnected;
    68	}
    69	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki