linux-kernel - Re: [PATCH v3 4/8] drm/msm/dp: Move link training to atomic

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Message-ID: <x72w6pys3ph7sfcpp2drowkv7wkis2vf2z72eokgo2m3mpiod5@ykuxvtdfcnpf>
Date: Thu, 15 Jan 2026 09:30:22 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Rob Clark <robin.clark@....qualcomm.com>, 
	Dmitry Baryshkov <lumag@...nel.org>, Abhinav Kumar <abhinav.kumar@...ux.dev>, 
	Jessica Zhang <jesszhan0024@...il.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Kuogee Hsieh <quic_khsieh@...cinc.com>, 
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, Jessica Zhang <jessica.zhang@....qualcomm.com>
Subject: Re: [PATCH v3 4/8] drm/msm/dp: Move link training to atomic_enable()

On Thu, Jan 15, 2026 at 09:29:09AM +0200, Dmitry Baryshkov wrote:
> From: Jessica Zhang <jessica.zhang@....qualcomm.com>
> 
> Currently, the DP link training is being done during HPD. Move
> link training to atomic_enable() in accordance with the atomic_enable()
> documentation.
> 
> Link disabling is already done in atomic_post_disable() (as part of the
> dp_ctrl_off_link_stream() helper).
> 
> Finally, call the plug/unplug handlers directly in hpd_notify() instead
> of queueing them in the event thread so that they aren't preempted by
> other events.
> 
> Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>

Reviewed-by: Bjorn Andersson <andersson@...nel.org>

> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index a05144de3b93..3184066adb15 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -436,11 +436,6 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
>  	msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false);
>  
>  	msm_dp_link_reset_phy_params_vx_px(dp->link);

I think unrelated to this patch (and series), but do we really want to
keep the v_level and p_level settings until the user reconnects the
cable?

Regards,
Bjorn

> -	rc = msm_dp_ctrl_on_link(dp->ctrl);
> -	if (rc) {
> -		DRM_ERROR("failed to complete DP link training\n");
> -		goto end;
> -	}
>  
>  	msm_dp_add_event(dp, EV_USER_NOTIFICATION, true, 0);
>  
> @@ -1695,6 +1690,12 @@ void msm_dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
>  		force_link_train = true;
>  	}
>  
> +	rc = msm_dp_ctrl_on_link(msm_dp_display->ctrl);
> +	if (rc) {
> +		DRM_ERROR("Failed link training (rc=%d)\n", rc);
> +		drm_connector_set_link_status_property(dp->connector, DRM_LINK_STATUS_BAD);
> +	}
> +
>  	msm_dp_display_enable(msm_dp_display, force_link_train);
>  
>  	rc = msm_dp_display_post_enable(dp);
> 
> -- 
> 2.47.3
> 
>