linux-kernel - Re: [PATCH v4 drm-dp 02/11] drm/hisilicon/hibmc: fix dp probabilistical detect errors after HPD irq

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Message-ID: <aayi7zjrmru2ancexrqmcutams6ohde3nrkhqacixwp45dsk4v@7ig6hqzahdxf>
Date: Thu, 14 Aug 2025 12:05:57 +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,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 drm-dp 02/11] drm/hisilicon/hibmc: fix dp
 probabilistical detect errors after HPD irq

On Wed, Aug 13, 2025 at 05:42:29PM +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. So add a flag to hold the sink
> status, and changed detect_ctx() functions by using flag to check status.

THis doesn't explain what is wrong with
drm_connector_helper_detect_from_ddc(). In the end, this function
doesn't use the HPD pin.

> 
> 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:
> v3 -> v4:
>   - remove link training process in hibmc_dp_detect(), suggested by Dmitry Baryshkov.
>   - remove if (dev->registered), suggested by Dmitry Baryshkov.
> ---
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h    |  1 +
>  .../gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c    | 19 ++++++++++++-------
>  2 files changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
> index 665f5b166dfb..68867475508c 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
> +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.h
> @@ -50,6 +50,7 @@ struct hibmc_dp {
>  	struct drm_dp_aux aux;
>  	struct hibmc_dp_cbar_cfg cfg;
>  	u32 irq_status;
> +	int hpd_status;
>  };
>  
>  int hibmc_dp_hw_init(struct hibmc_dp *dp);
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
> index d06832e62e96..ded38530ecda 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_dp *dp = to_hibmc_dp(connector);
>  
> -	return drm_connector_helper_detect_from_ddc(connector, ctx, force);
> +	if (dp->hpd_status)
> +		return connector_status_connected;
> +	else
> +		return connector_status_disconnected;
>  }
>  
>  static const struct drm_connector_helper_funcs hibmc_dp_conn_helper_funcs = {
> @@ -115,21 +118,23 @@ irqreturn_t hibmc_dp_hpd_isr(int irq, void *arg)
>  {
>  	struct drm_device *dev = (struct drm_device *)arg;
>  	struct hibmc_drm_private *priv = to_hibmc_drm_private(dev);
> +	struct hibmc_dp *dp = &priv->dp;
>  	int idx;
>  
>  	if (!drm_dev_enter(dev, &idx))
>  		return -ENODEV;
>  
> -	if (priv->dp.irq_status & DP_MASKED_SINK_HPD_PLUG_INT) {
> +	if (((dp->irq_status & DP_MASKED_SINK_HPD_PLUG_INT) && !dp->hpd_status)) {
>  		drm_dbg_dp(&priv->dev, "HPD IN isr occur!\n");
> -		hibmc_dp_hpd_cfg(&priv->dp);
> +		hibmc_dp_hpd_cfg(dp);
> +		dp->hpd_status = 1;
>  	} else {
>  		drm_dbg_dp(&priv->dev, "HPD OUT isr occur!\n");
> -		hibmc_dp_reset_link(&priv->dp);
> +		hibmc_dp_reset_link(dp);
> +		dp->hpd_status = 0;
>  	}
>  
> -	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