[RESEND v3 1/6] drm/mst: read sideband messaging cap

[Danilo Krummrich]

On 3/19/24 10:12, Jani Nikula wrote:
> Amend drm_dp_read_mst_cap() to return an enum, indicating "SST", "SST
> with sideband messaging", or "MST". Modify all call sites to take the
> new return value into account.
> 
> v2:
> - Rename enumerators (Ville)
> 
> Cc: Arun R Murthy <arun.r.murthy at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Karol Herbst <kherbst at redhat.com>
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Danilo Krummrich <dakr at redhat.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>

Acked-by: Danilo Krummrich <dakr at redhat.com>

> ---
>   drivers/gpu/drm/display/drm_dp_mst_topology.c | 20 ++++++++++------
>   drivers/gpu/drm/i915/display/intel_dp.c       |  4 ++--
>   drivers/gpu/drm/nouveau/nouveau_dp.c          |  2 +-
>   include/drm/display/drm_dp_mst_helper.h       | 23 ++++++++++++++++++-
>   4 files changed, 38 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index 03d528209426..c193be3577f7 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -3608,24 +3608,30 @@ fixed20_12 drm_dp_get_vc_payload_bw(const struct drm_dp_mst_topology_mgr *mgr,
>   EXPORT_SYMBOL(drm_dp_get_vc_payload_bw);
>   
>   /**
> - * drm_dp_read_mst_cap() - check whether or not a sink supports MST
> + * drm_dp_read_mst_cap() - Read the sink's MST mode capability
>    * @aux: The DP AUX channel to use
>    * @dpcd: A cached copy of the DPCD capabilities for this sink
>    *
> - * Returns: %True if the sink supports MST, %false otherwise
> + * Returns: enum drm_dp_mst_mode to indicate MST mode capability
>    */
> -bool drm_dp_read_mst_cap(struct drm_dp_aux *aux,
> -			 const u8 dpcd[DP_RECEIVER_CAP_SIZE])
> +enum drm_dp_mst_mode drm_dp_read_mst_cap(struct drm_dp_aux *aux,
> +					 const u8 dpcd[DP_RECEIVER_CAP_SIZE])
>   {
>   	u8 mstm_cap;
>   
>   	if (dpcd[DP_DPCD_REV] < DP_DPCD_REV_12)
> -		return false;
> +		return DRM_DP_SST;
>   
>   	if (drm_dp_dpcd_readb(aux, DP_MSTM_CAP, &mstm_cap) != 1)
> -		return false;
> +		return DRM_DP_SST;
> +
> +	if (mstm_cap & DP_MST_CAP)
> +		return DRM_DP_MST;
> +
> +	if (mstm_cap & DP_SINGLE_STREAM_SIDEBAND_MSG)
> +		return DRM_DP_SST_SIDEBAND_MSG;
>   
> -	return mstm_cap & DP_MST_CAP;
> +	return DRM_DP_SST;
>   }
>   EXPORT_SYMBOL(drm_dp_read_mst_cap);
>   
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index af7ca00e9bc0..91c42949ac7e 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4046,7 +4046,7 @@ intel_dp_can_mst(struct intel_dp *intel_dp)
>   
>   	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_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DRM_DP_MST;
>   }
>   
>   static void
> @@ -4055,7 +4055,7 @@ 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);
> +	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",
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dp.c b/drivers/gpu/drm/nouveau/nouveau_dp.c
> index 7de7707ec6a8..fb06ee17d9e5 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dp.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dp.c
> @@ -181,7 +181,7 @@ nouveau_dp_probe_dpcd(struct nouveau_connector *nv_connector,
>   	if (nouveau_mst) {
>   		mstm = outp->dp.mstm;
>   		if (mstm)
> -			mstm->can_mst = drm_dp_read_mst_cap(aux, dpcd);
> +			mstm->can_mst = drm_dp_read_mst_cap(aux, dpcd) == DRM_DP_MST;
>   	}
>   
>   	if (nouveau_dp_has_sink_count(connector, outp)) {
> diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h
> index 3ae88a383a41..cbcb49cb6a46 100644
> --- a/include/drm/display/drm_dp_mst_helper.h
> +++ b/include/drm/display/drm_dp_mst_helper.h
> @@ -817,7 +817,28 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
>   
>   void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr);
>   
> -bool drm_dp_read_mst_cap(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE]);
> +/**
> + * enum drm_dp_mst_mode - sink's MST mode capability
> + */
> +enum drm_dp_mst_mode {
> +	/**
> +	 * @DRM_DP_SST: The sink does not support MST nor single stream sideband
> +	 * messaging.
> +	 */
> +	DRM_DP_SST,
> +	/**
> +	 * @DRM_DP_MST: Sink supports MST, more than one stream and single
> +	 * stream sideband messaging.
> +	 */
> +	DRM_DP_MST,
> +	/**
> +	 * @DRM_DP_SST_SIDEBAND_MSG: Sink supports only one stream and single
> +	 * stream sideband messaging.
> +	 */
> +	DRM_DP_SST_SIDEBAND_MSG,
> +};
> +
> +enum drm_dp_mst_mode drm_dp_read_mst_cap(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIVER_CAP_SIZE]);
>   int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool mst_state);
>   
>   int drm_dp_mst_hpd_irq_handle_event(struct drm_dp_mst_topology_mgr *mgr,