Re: [PATCH v2 2/6] drm/i915/mst: improve debug logging of DP MST mode detect

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Feb 13, 2024 at 01:30:57PM +0200, Jani Nikula wrote:
> Rename intel_dp_can_mst() to intel_dp_mst_detect(), and move all DP MST
> detect debug logging there. Debug log the sink's MST capability,
> including single-stream sideband messaging support, and the decision
> whether to enable MST mode or not. Do this regardless of whether we're
> actually enabling MST or not.
> 
> Cc: Arun R Murthy <arun.r.murthy@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 45 +++++++++++++++++--------
>  1 file changed, 31 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index a1c304f451bd..944f566525dd 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4007,31 +4007,48 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
>  					   intel_dp->downstream_ports) == 0;
>  }
>  
> +static const char *intel_dp_mst_mode_str(enum drm_dp_mst_mode mst_mode)
> +{
> +	if (mst_mode == DRM_DP_SST_SIDEBAND_MSG)
> +		return "single-stream sideband messaging";
> +	else
> +		return str_yes_no(mst_mode == DRM_DP_MST);

I wonder if this should also just say "sst"/"mst"/"sst sideband" etc.
Shrug.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +}
> +
>  static bool
> -intel_dp_can_mst(struct intel_dp *intel_dp)
> +intel_dp_mst_detect(struct intel_dp *intel_dp)
>  {
>  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> +	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
> +	enum drm_dp_mst_mode sink_mst_mode;
> +	enum drm_dp_mst_mode mst_detect;
> +
> +	sink_mst_mode = drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd);
> +
> +	if (i915->display.params.enable_dp_mst &&
> +	    intel_dp_mst_source_support(intel_dp) &&
> +	    sink_mst_mode == DRM_DP_MST)
> +		mst_detect = DRM_DP_MST;
> +	else
> +		mst_detect = DRM_DP_SST;
>  
> -	return i915->display.params.enable_dp_mst &&
> -		intel_dp_mst_source_support(intel_dp) &&
> -		drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DRM_DP_MST;
> +	drm_dbg_kms(&i915->drm,
> +		    "[ENCODER:%d:%s] MST support: port: %s, sink: %s, modparam: %s -> enable: %s\n",
> +		    encoder->base.base.id, encoder->base.name,
> +		    str_yes_no(intel_dp_mst_source_support(intel_dp)),
> +		    intel_dp_mst_mode_str(sink_mst_mode),
> +		    str_yes_no(i915->display.params.enable_dp_mst),
> +		    intel_dp_mst_mode_str(mst_detect));
> +
> +	return mst_detect != DRM_DP_SST;
>  }
>  
>  static void
>  intel_dp_configure_mst(struct intel_dp *intel_dp)
>  {
>  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> -	struct intel_encoder *encoder =
> -		&dp_to_dig_port(intel_dp)->base;
>  	bool sink_can_mst = drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DRM_DP_MST;
>  
> -	drm_dbg_kms(&i915->drm,
> -		    "[ENCODER:%d:%s] MST support: port: %s, sink: %s, modparam: %s\n",
> -		    encoder->base.base.id, encoder->base.name,
> -		    str_yes_no(intel_dp_mst_source_support(intel_dp)),
> -		    str_yes_no(sink_can_mst),
> -		    str_yes_no(i915->display.params.enable_dp_mst));
> -
>  	if (!intel_dp_mst_source_support(intel_dp))
>  		return;
>  
> @@ -5390,7 +5407,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
>  		connector_status_connected : connector_status_disconnected;
>  	}
>  
> -	if (intel_dp_can_mst(intel_dp))
> +	if (intel_dp_mst_detect(intel_dp))
>  		return connector_status_connected;
>  
>  	/* If no HPD, poke DDC gently */
> -- 
> 2.39.2

-- 
Ville Syrjälä
Intel