Re: [PATCH v4 37/39] drm/msm/dp: add HPD callback for dp MST

[Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>]

On Fri, Apr 10, 2026 at 05:34:12PM +0800, Yongxing Mou wrote:
> From: Abhinav Kumar <quic_abhinavk@quicinc.com>
> 
> Add HPD callback for the MST module which shall be invoked from the
> dp_display's HPD handler to perform MST specific operations in case
> of HPD. In MST case, route the HPD messages to MST module.
> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 23 +++++++++++++++++++----
>  drivers/gpu/drm/msm/dp/dp_mst_drm.c | 34 ++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/msm/dp/dp_mst_drm.h |  1 +
>  3 files changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 919767945ba5..ca89e20b7563 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -454,6 +454,9 @@ static int msm_dp_hpd_plug_handle(struct msm_dp_display_private *dp)
>  			dp->msm_dp_display.connector_type,
>  			dp->link->sink_count);
>  
> +	if (dp->plugged)
> +		return 0;
> +
>  	mutex_lock(&dp->plugged_lock);
>  
>  	ret = pm_runtime_resume_and_get(&pdev->dev);
> @@ -556,12 +559,19 @@ static int msm_dp_irq_hpd_handle(struct msm_dp_display_private *dp)
>  {
>  	u32 sink_request;
>  	int rc = 0;
> +	struct msm_dp *msm_dp_display = &dp->msm_dp_display;
>  
>  	/* irq_hpd can happen at either connected or disconnected state */
>  	drm_dbg_dp(dp->drm_dev, "Before, type=%d, sink_count=%d\n",
>  			dp->msm_dp_display.connector_type,
>  			dp->link->sink_count);
>  
> +	if (msm_dp_display->mst_active) {
> +		if (msm_dp_aux_is_link_connected(dp->aux) != ISR_DISCONNECTED)

Will this work for USB-C?

> +			msm_dp_mst_display_hpd_irq(&dp->msm_dp_display);
> +		return 0;
> +	}
> +
>  	/* check for any test request issued by sink */
>  	rc = msm_dp_link_process_request(dp->link);
>  	if (!rc) {
> @@ -1125,9 +1135,13 @@ static irqreturn_t msm_dp_display_irq_thread(int irq, void *dev_id)
>  				      connector_status_connected);
>  
>  	/* Send HPD as connected and distinguish it in the notifier */
> -	if (hpd_isr_status & DP_DP_IRQ_HPD_INT_MASK)
> -		drm_bridge_hpd_notify(dp->msm_dp_display.bridge,
> -				      connector_status_connected);
> +	if (hpd_isr_status & DP_DP_IRQ_HPD_INT_MASK) {
> +		if (dp->msm_dp_display.mst_active)
> +			msm_dp_irq_hpd_handle(dp);

No, don't touch this code. HPD notifications might be coming from the
other entities. This IRQ thread can only send the HPD notification.
There rest should be handled in the notifier.

> +		else
> +			drm_bridge_hpd_notify(dp->msm_dp_display.bridge,
> +					      connector_status_connected);
> +	}
>  
>  	ret = IRQ_HANDLED;
>  
> @@ -1793,7 +1807,8 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge,
>  			msm_dp_hpd_plug_handle(dp);
>  		}
>  	} else {
> -		msm_dp_hpd_unplug_handle(dp);
> +		if (hpd_link_status == ISR_DISCONNECTED)

Why?

> +			msm_dp_hpd_unplug_handle(dp);
>  	}
>  
>  	pm_runtime_put_sync(&msm_dp_display->pdev->dev);
> diff --git a/drivers/gpu/drm/msm/dp/dp_mst_drm.c b/drivers/gpu/drm/msm/dp/dp_mst_drm.c
> index bb3898b1f6b1..71d3f63973e6 100644
> --- a/drivers/gpu/drm/msm/dp/dp_mst_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_mst_drm.c
> @@ -490,6 +490,40 @@ int msm_dp_mst_display_set_mgr_state(struct msm_dp *dp_display, bool state)
>  	return rc;
>  }
>  
> +/* DP MST HPD IRQ callback */

Useless comment.

> +void msm_dp_mst_display_hpd_irq(struct msm_dp *dp_display)
> +{
> +	int rc;
> +	struct msm_dp_mst *mst = dp_display->msm_dp_mst;
> +	u8 ack[8] = {};
> +	u8 esi[4];
> +	unsigned int esi_res = DP_SINK_COUNT_ESI + 1;
> +	bool handled;
> +
> +	rc = drm_dp_dpcd_read_data(mst->dp_aux, DP_SINK_COUNT_ESI, esi, 4);
> +	if (rc < 0) {
> +		DRM_ERROR("DPCD sink status read failed, rlen=%d\n", rc);
> +		return;
> +	}
> +
> +	drm_dbg_dp(dp_display->drm_dev, "MST irq: esi1[0x%x] esi2[0x%x] esi3[%x]\n",
> +		   esi[1], esi[2], esi[3]);
> +
> +	rc = drm_dp_mst_hpd_irq_handle_event(&mst->mst_mgr, esi, ack, &handled);
> +
> +	/* ack the request */
> +	if (handled) {
> +		rc = drm_dp_dpcd_write_byte(mst->dp_aux, esi_res, ack[1]);
> +		if (rc < 0) {
> +			DRM_ERROR("DPCD esi_res failed. rc=%d\n", rc);
> +			return;
> +		}
> +
> +		drm_dp_mst_hpd_irq_send_new_request(&mst->mst_mgr);
> +	}
> +	drm_dbg_dp(dp_display->drm_dev, "MST display hpd_irq handled:%d rc:%d\n", handled, rc);
> +}
> +
>  /* DP MST Connector OPs */
>  static int
>  msm_dp_mst_connector_detect(struct drm_connector *connector,
> diff --git a/drivers/gpu/drm/msm/dp/dp_mst_drm.h b/drivers/gpu/drm/msm/dp/dp_mst_drm.h
> index 5d411529f681..08e145399cfc 100644
> --- a/drivers/gpu/drm/msm/dp/dp_mst_drm.h
> +++ b/drivers/gpu/drm/msm/dp/dp_mst_drm.h
> @@ -9,5 +9,6 @@
>  
>  int msm_dp_mst_init(struct msm_dp *dp_display, u32 max_streams, struct drm_dp_aux *drm_aux);
>  int msm_dp_mst_display_set_mgr_state(struct msm_dp *dp_display, bool state);
> +void msm_dp_mst_display_hpd_irq(struct msm_dp *dp_display);
>  
>  #endif /* _DP_MST_DRM_H_ */
> 
> -- 
> 2.43.0
> 

-- 
With best wishes
Dmitry