Re: [PATCH RESEND v5 14/25] drm/msm/dp: Mark the SST bridge disconnected when mst is active

[Dmitry Baryshkov]

On Mon, Jun 29, 2026 at 10:14:35PM +0800, Yongxing Mou wrote:
> From: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> 
> The bridge detect function is only applicable for SST. In MST mode,
> connector detection is handled by MST bridges. Skips detection for the
> SST bridge when MST is active.
> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index d0081ea9f5cd..5786e598a406 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -910,6 +910,9 @@ enum drm_connector_status msm_dp_bridge_detect(struct drm_bridge *bridge,
>  
>  	priv = container_of(dp, struct msm_dp_display_private, msm_dp_display);
>  
> +	if (dp->mst_active)
> +		return status;
> +
>  	guard(mutex)(&priv->plugged_lock);
>  	ret = pm_runtime_resume_and_get(&dp->pdev->dev);
>  	if (ret) {
> @@ -955,6 +958,10 @@ enum drm_connector_status msm_dp_bridge_detect(struct drm_bridge *bridge,
>  			status = connector_status_disconnected;
>  	}
>  
> +	/* skip for MST */
> +	if (priv->max_stream > 1 && drm_dp_read_mst_cap(priv->aux, dpcd))
> +		status = connector_status_disconnected;

Also, if this patch gets applied at this moment, it breaks DP support,
since the SST connector will report disconnected, but MST connectors are
not there yet.

> +
>  end:
>  	/*
>  	 * If we detected the DPRX, leave the controller on so that it doesn't
> 
> -- 
> 2.43.0
> 

-- 
With best wishes
Dmitry