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

[Yongxing Mou]

On 7/13/2026 5:00 AM, Dmitry Baryshkov wrote:
> 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.
>
> Please mention that it matches the state of other platforms.
Got it.
> > 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;
>
> Hmm, should it only be marked as disconnected after we switch to the MST
> mode? When is the switch happening?
This condition is intended to handle the DP boot-up case, where detect() 
runs before notify(), meaning mst_active is still false when we reach 
this point. In the normal plug/unplug flow, notify() runs first.

I think this should be split into two patches. Adding this check only 
makes sense once MST is actually functional; otherwise, it risks 
breaking SST.
> > +
> >   end:
> >   	/*
> >   	 * If we detected the DPRX, leave the controller on so that it doesn't
> >
> > --
> > 2.43.0