Re: [PATCH RESEND v5 25/25] drm/msm/dp: add HPD callback for dp MST

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

On Mon, Jun 29, 2026 at 10:14:46PM +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 | 22 ++++++++++++++----
>  drivers/gpu/drm/msm/dp/dp_mst_drm.c | 46 +++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/msm/dp/dp_mst_drm.h |  1 +
>  3 files changed, 65 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 6eac390af2e0..49a7bc5e031e 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -455,6 +455,9 @@ 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 && dp->msm_dp_display.mst_active)
> +		return 0;

Why?

> +
>  	guard(mutex)(&dp->plugged_lock);
>  
>  	ret = pm_runtime_resume_and_get(&pdev->dev);
> @@ -550,12 +553,18 @@ 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) {
> +		msm_dp_mst_display_hpd_irq(&dp->msm_dp_display);

This should be routed through the HPD / notifications API so that there
is always a single path for handling the IRQ_HPD interrupts.

> +		return 0;
> +	}
> +
>  	/* check for any test request issued by sink */
>  	rc = msm_dp_link_process_request(dp->link);
>  	if (!rc) {
> @@ -1111,9 +1120,13 @@ 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)

Locking? What if MST is being enabled or disabled on the other core?

> +			msm_dp_irq_hpd_handle(dp);
> +		else
> +			drm_bridge_hpd_notify(dp->msm_dp_display.bridge,
> +					      connector_status_connected);
> +	}
>  
>  	ret = IRQ_HANDLED;
>  

-- 
With best wishes
Dmitry