Re: [PATCH RESEND v5 17/25] drm/msm/dp: add link_ready to manage link-level operations

[Yongxing Mou]

On 7/13/2026 7:46 AM, Dmitry Baryshkov wrote:
> On Mon, Jun 29, 2026 at 10:14:38PM +0800, Yongxing Mou wrote:
> > In MST mode, multiple streams share the same DP link. Track a link_ready
> > state so msm_dp_display_prepare_link() runs only once per link and
> > repeated calls are skipped.
> >
> > Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> > Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/dp/dp_display.c | 42 ++++++++++++++++++++++++-------------
> >   drivers/gpu/drm/msm/dp/dp_display.h |  1 +
> >   2 files changed, 29 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> > index 2a74302bcb7c..d56ee10ee065 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > @@ -702,6 +702,9 @@ int msm_dp_display_prepare_link(struct msm_dp *msm_dp_display)
> >   	if (msm_dp_display->is_edp)
> >   		msm_dp_hpd_plug_handle(dp);
> >   
> > +	if (msm_dp_display->link_ready)
> > +		return 0;
> > +
>
> What kind of locking is protecting this variable? What prevents it from
> being accessed concurrently?
In MST, the entire function is protected by mst_lock, so concurrent 
access to this variable is serialized.
> >   	rc = pm_runtime_resume_and_get(&msm_dp_display->pdev->dev);
> >   	if (rc) {
> >   		DRM_ERROR("failed to pm_runtime_resume\n");
> > @@ -714,14 +717,18 @@ int msm_dp_display_prepare_link(struct msm_dp *msm_dp_display)
> >   	if (!msm_dp_display->active_stream_cnt) {
> >   		msm_dp_display_host_phy_init(dp);
> >   		force_link_train = true;
> > +
> > +		rc = msm_dp_ctrl_on_link(dp->ctrl, dp->panel);
> > +		if (rc)
> > +			DRM_ERROR("Failed link training (rc=%d)\n", rc);
> > +		// TODO: schedule drm_connector_set_link_status_property()
> >   	}
> >   
> > -	rc = msm_dp_ctrl_on_link(dp->ctrl, dp->panel);
> > -	if (rc)
> > -		DRM_ERROR("Failed link training (rc=%d)\n", rc);
> > -	// TODO: schedule drm_connector_set_link_status_property()
>
> Why is it being moved now rather than in the patch where
> active_stream_cnt was introduced?
Got it. will move to that part
> > +	rc = msm_dp_ctrl_prepare_stream_on(dp->ctrl, dp->panel, force_link_train);
> > +	if (!rc)
> > +		msm_dp_display->link_ready = true;
> >   
> > -	return msm_dp_ctrl_prepare_stream_on(dp->ctrl, dp->panel, force_link_train);
> > +	return rc;
> >   }
> >   
> >   static int msm_dp_display_enable(struct msm_dp_display_private *dp,
>
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> > index 676213a48089..0464f8941e8d 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.h
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> > @@ -22,6 +22,7 @@ struct msm_dp {
> >   	bool mst_active;
> >   	unsigned int connector_type;
> >   	bool is_edp;
> > +	bool link_ready;
>
> Please group the status variables together.
Got it.
> >   
> >   	struct msm_dp_audio *msm_dp_audio;
> >   	bool psr_supported;
> >
> > --
> > 2.43.0