linux-kernel - Re: [PATCH 01/19] drm/msm/dp: Track when DP is physically plugged in

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Message-ID: <ytskndhnox6p2ozwqxnpfyj7d4finr2go7qih4hpjqaf6onigc@zhiunxyw6xaa>
Date: Mon, 14 Jul 2025 14:42:57 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Jessica Zhang <jessica.zhang@....qualcomm.com>
Cc: Rob Clark <robin.clark@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Dmitry Baryshkov <lumag@...nel.org>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yongxing Mou <quic_yongmou@...cinc.com>
Subject: Re: [PATCH 01/19] drm/msm/dp: Track when DP is physically plugged in

On Fri, Jul 11, 2025 at 05:58:06PM -0700, Jessica Zhang wrote:
> Add a boolean to track whether the DP cable is physically plugged in.

I think there is more than that. Other drivers check that there is
actually something connected (so checking the sink count, etc.). See
Mediatek or IT6505 drivers, they have simple examples.

> Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 11 ++++++++++-
>  drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index d87d47cc7ec3..6945df782f7b 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -531,6 +531,7 @@ static int msm_dp_display_handle_port_status_changed(struct msm_dp_display_priva
>  			rc = msm_dp_display_process_hpd_high(dp);
>  			if (rc)
>  				dp->hpd_state = ST_DISCONNECTED;
> +			dp->msm_dp_display.connected = true;
>  		}
>  	}
>  
> @@ -604,6 +605,8 @@ static int msm_dp_hpd_plug_handle(struct msm_dp_display_private *dp, u32 data)
>  		return 0;
>  	}
>  
> +	dp->msm_dp_display.connected = true;
> +
>  	if (state == ST_DISCONNECT_PENDING) {
>  		/* wait until ST_DISCONNECTED */
>  		msm_dp_add_event(dp, EV_HPD_PLUG_INT, 0, 1); /* delay = 1 */
> @@ -621,6 +624,7 @@ static int msm_dp_hpd_plug_handle(struct msm_dp_display_private *dp, u32 data)
>  	ret = msm_dp_display_usbpd_configure_cb(&pdev->dev);
>  	if (ret) {	/* link train failed */
>  		dp->hpd_state = ST_DISCONNECTED;
> +		dp->msm_dp_display.connected = false;
>  		pm_runtime_put_sync(&pdev->dev);
>  	} else {
>  		dp->hpd_state = ST_MAINLINK_READY;
> @@ -662,6 +666,8 @@ static int msm_dp_hpd_unplug_handle(struct msm_dp_display_private *dp, u32 data)
>  	drm_dbg_dp(dp->drm_dev, "Before, type=%d hpd_state=%d\n",
>  			dp->msm_dp_display.connector_type, state);
>  
> +	dp->msm_dp_display.connected = false;
> +
>  	/* unplugged, no more irq_hpd handle */
>  	msm_dp_del_event(dp, EV_IRQ_HPD_INT);
>  
> @@ -680,6 +686,7 @@ static int msm_dp_hpd_unplug_handle(struct msm_dp_display_private *dp, u32 data)
>  		msm_dp_ctrl_off_link(dp->ctrl);
>  		msm_dp_display_host_phy_exit(dp);
>  		dp->hpd_state = ST_DISCONNECTED;
> +		dp->msm_dp_display.connected = false;
>  		msm_dp_display_notify_disconnect(&dp->msm_dp_display.pdev->dev);
>  		pm_runtime_put_sync(&pdev->dev);
>  		mutex_unlock(&dp->event_mutex);
> @@ -1596,8 +1603,10 @@ void msm_dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
>  		return;
>  	}
>  
> -	if (dp->is_edp)
> +	if (dp->is_edp) {
>  		msm_dp_hpd_plug_handle(msm_dp_display, 0);
> +		dp->connected = true;
> +	}

So, are we returning 'disconnected' for eDP panels up to the
atomic_enable() point? Then nobody will ever enable it.

>  
>  	mutex_lock(&msm_dp_display->event_mutex);
>  	if (pm_runtime_resume_and_get(&dp->pdev->dev)) {
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index cc6e2cab36e9..68bd8be19463 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -16,6 +16,7 @@ struct msm_dp {
>  	struct platform_device *pdev;
>  	struct drm_connector *connector;
>  	struct drm_bridge *next_bridge;
> +	bool connected;
>  	bool link_ready;
>  	bool audio_enabled;
>  	bool power_on;
> 
> -- 
> 2.50.1
> 

-- 
With best wishes
Dmitry