Re: [PATCH v3 drm-dp 02/11] drm/hisilicon/hibmc: fix dp probabilistical detect errors after HPD irq

[Yongbang Shi]

On Fri, Jul 18, 2025 at 02:51:16PM +0800, Yongbang Shi wrote:

From: Baihan Li <libai...@huawei.com>

The debouncing when HPD pulled out still remains sometimes, 200ms still can
not ensure helper_detect() is correct. Add hibmc_dp_detect_link() in
detect_ctx(), which is to try dp link training.

I'm not sure if I follow the commit message. Anyway, link training
should be a part of atomic_(pre)_enable, not a detect_ctx.

Okay, I will change it. thanks for your advice!

The problem is that when I unpluged the connector, sometimes the 
drm_connector_helper_detect_from_ddc()
return connected in dp's detect_ctx().

Fixes: 3c7623fb5bb6 ("drm/hisilicon/hibmc: Enable this hot plug detect of irq 
feature")
Signed-off-by: Baihan Li <libai...@huawei.com>
Signed-off-by: Yongbang Shi <shiyongb...@huawei.com>
---
  drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c    | 27 +++++++++++++++----
  drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h    |  2 ++
  .../gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c    | 10 ++++---
  3 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c 
b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
index 8f0daec7d174..2d2fb6e759c3 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c
@@ -3,6 +3,7 @@

#include <linux/io.h>

  #include <linux/delay.h>
+#include <drm/drm_managed.h>
  #include "dp_config.h"
  #include "dp_comm.h"
  #include "dp_reg.h"
@@ -162,6 +163,8 @@ int hibmc_dp_hw_init(struct hibmc_dp *dp)

mutex_init(&dp_dev->lock); + drmm_mutex_init(drm_dev, &dp->link_train_mutex);

+
        dp->dp_dev = dp_dev;

dp_dev->dev = drm_dev;

@@ -238,19 +241,33 @@ void hibmc_dp_display_en(struct hibmc_dp *dp, bool enable)
        msleep(50);
  }

-int hibmc_dp_mode_set(struct hibmc_dp *dp, struct drm_display_mode *mode)

+int hibmc_dp_detect_link(struct hibmc_dp *dp)
  {
        struct hibmc_dp_dev *dp_dev = dp->dp_dev;
-       int ret;
+       int ret = 0;
+
+       mutex_lock(&dp->link_train_mutex);

if (!dp_dev->link.status.channel_equalized) {

                ret = hibmc_dp_link_training(dp_dev);
-               if (ret) {
+               if (ret)
                        drm_err(dp->drm_dev, "dp link training failed, ret: 
%d\n", ret);
-                       return ret;
-               }
        }

+ mutex_unlock(&dp->link_train_mutex);

+
+       return ret;
+}
+
+int hibmc_dp_mode_set(struct hibmc_dp *dp, struct drm_display_mode *mode)
+{
+       struct hibmc_dp_dev *dp_dev = dp->dp_dev;
+       int ret;
+
+       ret = hibmc_dp_detect_link(dp);
+       if (ret)
+               return ret;
+
        hibmc_dp_display_en(dp, false);
        hibmc_dp_link_cfg(dp_dev, mode);

diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h

index 665f5b166dfb..9b45e88e47e4 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
@@ -50,9 +50,11 @@ struct hibmc_dp {
        struct drm_dp_aux aux;
        struct hibmc_dp_cbar_cfg cfg;
        u32 irq_status;
+       struct mutex link_train_mutex; /* link training mutex */
  };

int hibmc_dp_hw_init(struct hibmc_dp *dp);

+int hibmc_dp_detect_link(struct hibmc_dp *dp);
  int hibmc_dp_mode_set(struct hibmc_dp *dp, struct drm_display_mode *mode);
  void hibmc_dp_display_en(struct hibmc_dp *dp, bool enable);
  void hibmc_dp_set_cbar(struct hibmc_dp *dp, const struct hibmc_dp_cbar_cfg 
*cfg);
diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c 
b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
index d06832e62e96..354e18bb2998 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
+++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
@@ -34,9 +34,12 @@ 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_drm_private *priv = to_hibmc_drm_private(connector->dev);

- return drm_connector_helper_detect_from_ddc(connector, ctx, force);

+       if (!hibmc_dp_detect_link(&priv->dp))
+               return connector_status_connected;
+
+       return connector_status_disconnected;
  }

static const struct drm_connector_helper_funcs hibmc_dp_conn_helper_funcs = {

@@ -128,8 +131,7 @@ irqreturn_t hibmc_dp_hpd_isr(int irq, void *arg)
                hibmc_dp_reset_link(&priv->dp);
        }

- if (dev->registered)

-               drm_connector_helper_hpd_irq_event(&priv->dp.connector);
+       drm_connector_helper_hpd_irq_event(&priv->dp.connector);

drm_dev_exit(idx); --

2.33.0