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

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Message-ID: <f7co2accpkvt4b5jy7ar4j6jqiytmysd3ki32hvhg7w2ohqoo6@nwwxeif6f73q>
Date: Sat, 26 Jul 2025 18:03:55 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Yongbang Shi <shiyongbang@...wei.com>
Cc: 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, liangjian010@...wei.com,
        chenjianmin@...wei.com, fengsheng5@...wei.com, libaihan@...wei.com,
        shenjian15@...wei.com, shaojijie@...wei.com,
        jani.nikula@...ux.intel.com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 drm-dp 02/11] drm/hisilicon/hibmc: fix dp
 probabilistical detect errors after HPD irq

On Fri, Jul 18, 2025 at 02:51:16PM +0800, Yongbang Shi wrote:
> From: Baihan Li <libaihan@...wei.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.

> 
> 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>
> ---
>  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
> 

-- 
With best wishes
Dmitry