[RESEND v3 0/6] drm/i915/mst: enable MST mode for 128b/132b single-stream sideband

[RESEND v3 0/6] drm/i915/mst: enable MST mode for 128b/132b single-stream sideband

[Jani Nikula]

Resend because I forgot to Cc: dri-devel on the original submission.

Jani Nikula (6):
  drm/mst: read sideband messaging cap
  drm/i915/mst: improve debug logging of DP MST mode detect
  drm/i915/mst: abstract choosing the MST mode to use
  drm/i915/mst: use the MST mode detected previously
  drm/i915/mst: add intel_dp_mst_disconnect()
  drm/i915/mst: enable MST mode for 128b/132b single-stream sideband

 drivers/gpu/drm/display/drm_dp_mst_topology.c | 20 ++--
 .../drm/i915/display/intel_display_types.h    |  1 +
 drivers/gpu/drm/i915/display/intel_dp.c       | 95 +++++++++++++------
 drivers/gpu/drm/nouveau/nouveau_dp.c          |  2 +-
 include/drm/display/drm_dp_mst_helper.h       | 23 ++++-
 5 files changed, 104 insertions(+), 37 deletions(-)

-- 
2.39.2

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

[Jani Nikula]

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@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Danilo Krummrich <dakr@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.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,
-- 
2.39.2

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

[Jani Nikula]

On Tue, 19 Mar 2024, Jani Nikula <jani.nikula@intel.com> 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.

drm-misc and nouveau maintainers, ack for merging this via drm-intel,
please?

BR,
Jani.



>
> v2:
> - Rename enumerators (Ville)
>
> Cc: Arun R Murthy <arun.r.murthy@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Karol Herbst <kherbst@redhat.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Danilo Krummrich <dakr@redhat.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.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,

-- 
Jani Nikula, Intel

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

[Maxime Ripard]

[-- Attachment #1: Type: text/plain, Size: 420 bytes --]

On Tue, Mar 19, 2024 at 11:20:16AM +0200, Jani Nikula wrote:
> On Tue, 19 Mar 2024, Jani Nikula <jani.nikula@intel.com> 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.
> 
> drm-misc and nouveau maintainers, ack for merging this via drm-intel,
> please?

Ack

Maxime

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

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

[Danilo Krummrich]

On 3/19/24 10:20, Jani Nikula wrote:
> On Tue, 19 Mar 2024, Jani Nikula <jani.nikula@intel.com> 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.
> 
> drm-misc and nouveau maintainers, ack for merging this via drm-intel,
> please?

Sure, please go ahead.

Thanks,
Danilo

> 
> BR,
> Jani.
> 
> 
> 
>>
>> v2:
>> - Rename enumerators (Ville)
>>
>> Cc: Arun R Murthy <arun.r.murthy@intel.com>
>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> Cc: Karol Herbst <kherbst@redhat.com>
>> Cc: Lyude Paul <lyude@redhat.com>
>> Cc: Danilo Krummrich <dakr@redhat.com>
>> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@intel.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,
> 

Re: [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@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Karol Herbst <kherbst@redhat.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Danilo Krummrich <dakr@redhat.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Acked-by: Danilo Krummrich <dakr@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,

[RESEND v3 2/6] drm/i915/mst: improve debug logging of DP MST mode detect

[Jani Nikula]

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.

We need to detect MST in intel_dp_detect_dpcd() before the earlier
returns, but try not to change the logic otherwise.

v2:
- Use "MST", "SST w/ sideband messaging", and "SST" for logging (Ville)
- Return MST mode from intel_dp_mst_detect()
- Do MST detect before early returns from intel_dp_detect_dpcd()

Cc: Arun R Murthy <arun.r.murthy@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 52 ++++++++++++++++++-------
 1 file changed, 37 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 91c42949ac7e..9590c8c2c4f3 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4039,31 +4039,50 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 					   intel_dp->downstream_ports) == 0;
 }
 
-static bool
-intel_dp_can_mst(struct intel_dp *intel_dp)
+static const char *intel_dp_mst_mode_str(enum drm_dp_mst_mode mst_mode)
+{
+	if (mst_mode == DRM_DP_MST)
+		return "MST";
+	else if (mst_mode == DRM_DP_SST_SIDEBAND_MSG)
+		return "SST w/ sideband messaging";
+	else
+		return "SST";
+}
+
+static enum drm_dp_mst_mode
+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;
 }
 
 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;
 
@@ -5352,6 +5371,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 {
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
+	enum drm_dp_mst_mode mst_detect;
 	u8 *dpcd = intel_dp->dpcd;
 	u8 type;
 
@@ -5363,6 +5383,8 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 	if (!intel_dp_get_dpcd(intel_dp))
 		return connector_status_disconnected;
 
+	mst_detect = intel_dp_mst_detect(intel_dp);
+
 	/* if there's no downstream port, we're done */
 	if (!drm_dp_is_branch(dpcd))
 		return connector_status_connected;
@@ -5374,7 +5396,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 		connector_status_connected : connector_status_disconnected;
 	}
 
-	if (intel_dp_can_mst(intel_dp))
+	if (mst_detect == DRM_DP_MST)
 		return connector_status_connected;
 
 	/* If no HPD, poke DDC gently */
-- 
2.39.2

[RESEND v3 3/6] drm/i915/mst: abstract choosing the MST mode to use

[Jani Nikula]

Clarify the conditions for choosing the MST mode to use by adding a new
function intel_dp_mst_mode_choose(). This also prepares for being able
to extend the MST modes to single-stream sideband messaging.

Cc: Arun R Murthy <arun.r.murthy@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 9590c8c2c4f3..127b5a89502d 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4049,6 +4049,24 @@ static const char *intel_dp_mst_mode_str(enum drm_dp_mst_mode mst_mode)
 		return "SST";
 }
 
+static enum drm_dp_mst_mode
+intel_dp_mst_mode_choose(struct intel_dp *intel_dp,
+			 enum drm_dp_mst_mode sink_mst_mode)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+
+	if (!i915->display.params.enable_dp_mst)
+		return DRM_DP_SST;
+
+	if (!intel_dp_mst_source_support(intel_dp))
+		return DRM_DP_SST;
+
+	if (sink_mst_mode == DRM_DP_SST_SIDEBAND_MSG)
+		return DRM_DP_SST;
+
+	return sink_mst_mode;
+}
+
 static enum drm_dp_mst_mode
 intel_dp_mst_detect(struct intel_dp *intel_dp)
 {
@@ -4059,12 +4077,7 @@ intel_dp_mst_detect(struct intel_dp *intel_dp)
 
 	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;
+	mst_detect = intel_dp_mst_mode_choose(intel_dp, sink_mst_mode);
 
 	drm_dbg_kms(&i915->drm,
 		    "[ENCODER:%d:%s] MST support: port: %s, sink: %s, modparam: %s -> enable: %s\n",
-- 
2.39.2

[RESEND v3 4/6] drm/i915/mst: use the MST mode detected previously

[Jani Nikula]

Drop the duplicate read of DP_MSTM_CAP DPCD register, and the duplicate
logic for choosing MST mode, and store the chosen mode in struct
intel_dp. Rename intel_dp_configure_mst() to intel_dp_mst_configure()
while at it.

v2: Rebase on drm_dp_mst_detect() returning the mode, not bool

Cc: Arun R Murthy <arun.r.murthy@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 .../drm/i915/display/intel_display_types.h    |  1 +
 drivers/gpu/drm/i915/display/intel_dp.c       | 21 ++++++++-----------
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 8b9860cefaae..8a35fb6b2ade 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1804,6 +1804,7 @@ struct intel_dp {
 
 	bool is_mst;
 	int active_mst_links;
+	enum drm_dp_mst_mode mst_detect;
 
 	/* connector directly attached - won't be use for modeset in mst world */
 	struct intel_connector *attached_connector;
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 127b5a89502d..e2f77855e4a0 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4091,19 +4091,17 @@ intel_dp_mst_detect(struct intel_dp *intel_dp)
 }
 
 static void
-intel_dp_configure_mst(struct intel_dp *intel_dp)
+intel_dp_mst_configure(struct intel_dp *intel_dp)
 {
-	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
-	bool sink_can_mst = drm_dp_read_mst_cap(&intel_dp->aux, intel_dp->dpcd) == DRM_DP_MST;
-
 	if (!intel_dp_mst_source_support(intel_dp))
 		return;
 
-	intel_dp->is_mst = sink_can_mst &&
-		i915->display.params.enable_dp_mst;
+	intel_dp->is_mst = intel_dp->mst_detect != DRM_DP_SST;
 
-	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
-					intel_dp->is_mst);
+	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
+
+	/* Avoid stale info on the next detect cycle. */
+	intel_dp->mst_detect = DRM_DP_SST;
 }
 
 static bool
@@ -5384,7 +5382,6 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 {
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
-	enum drm_dp_mst_mode mst_detect;
 	u8 *dpcd = intel_dp->dpcd;
 	u8 type;
 
@@ -5396,7 +5393,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 	if (!intel_dp_get_dpcd(intel_dp))
 		return connector_status_disconnected;
 
-	mst_detect = intel_dp_mst_detect(intel_dp);
+	intel_dp->mst_detect = intel_dp_mst_detect(intel_dp);
 
 	/* if there's no downstream port, we're done */
 	if (!drm_dp_is_branch(dpcd))
@@ -5409,7 +5406,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 		connector_status_connected : connector_status_disconnected;
 	}
 
-	if (mst_detect == DRM_DP_MST)
+	if (intel_dp->mst_detect == DRM_DP_MST)
 		return connector_status_connected;
 
 	/* If no HPD, poke DDC gently */
@@ -5741,7 +5738,7 @@ intel_dp_detect(struct drm_connector *connector,
 
 	intel_dp_detect_dsc_caps(intel_dp, intel_connector);
 
-	intel_dp_configure_mst(intel_dp);
+	intel_dp_mst_configure(intel_dp);
 
 	/*
 	 * TODO: Reset link params when switching to MST mode, until MST
-- 
2.39.2

[RESEND v3 5/6] drm/i915/mst: add intel_dp_mst_disconnect()

[Jani Nikula]

Abstract the MST mode disconnect to a separate function.

Cc: Arun R Murthy <arun.r.murthy@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index e2f77855e4a0..9b8bd85c1a4e 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4104,6 +4104,20 @@ intel_dp_mst_configure(struct intel_dp *intel_dp)
 	intel_dp->mst_detect = DRM_DP_SST;
 }
 
+static void
+intel_dp_mst_disconnect(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+
+	if (!intel_dp->is_mst)
+		return;
+
+	drm_dbg_kms(&i915->drm, "MST device may have disappeared %d vs %d\n",
+		    intel_dp->is_mst, intel_dp->mst_mgr.mst_state);
+	intel_dp->is_mst = false;
+	drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst);
+}
+
 static bool
 intel_dp_get_sink_irq_esi(struct intel_dp *intel_dp, u8 *esi)
 {
@@ -5711,15 +5725,7 @@ intel_dp_detect(struct drm_connector *connector,
 		memset(intel_connector->dp.dsc_dpcd, 0, sizeof(intel_connector->dp.dsc_dpcd));
 		intel_dp->psr.sink_panel_replay_support = false;
 
-		if (intel_dp->is_mst) {
-			drm_dbg_kms(&dev_priv->drm,
-				    "MST device may have disappeared %d vs %d\n",
-				    intel_dp->is_mst,
-				    intel_dp->mst_mgr.mst_state);
-			intel_dp->is_mst = false;
-			drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
-							intel_dp->is_mst);
-		}
+		intel_dp_mst_disconnect(intel_dp);
 
 		intel_dp_tunnel_disconnect(intel_dp);
 
-- 
2.39.2

[RESEND v3 6/6] drm/i915/mst: enable MST mode for 128b/132b single-stream sideband

[Jani Nikula]

If the sink supports 128b/132b and single-stream sideband messaging,
enable MST mode.

With this, the topology manager will still write DP_MSTM_CTRL, which
should be ignored by the sink. In the future, the topology manager
should probably only set the sideband messaging related parts of the
register.

Cc: Arun R Murthy <arun.r.murthy@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 9b8bd85c1a4e..254f758e8dcd 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4061,7 +4061,8 @@ intel_dp_mst_mode_choose(struct intel_dp *intel_dp,
 	if (!intel_dp_mst_source_support(intel_dp))
 		return DRM_DP_SST;
 
-	if (sink_mst_mode == DRM_DP_SST_SIDEBAND_MSG)
+	if (sink_mst_mode == DRM_DP_SST_SIDEBAND_MSG &&
+	    !(intel_dp->dpcd[DP_MAIN_LINK_CHANNEL_CODING] & DP_CAP_ANSI_128B132B))
 		return DRM_DP_SST;
 
 	return sink_mst_mode;
-- 
2.39.2

Re: [RESEND v3 0/6] drm/i915/mst: enable MST mode for 128b/132b single-stream sideband

[Jani Nikula]

On Tue, 19 Mar 2024, Jani Nikula <jani.nikula@intel.com> wrote:
> Resend because I forgot to Cc: dri-devel on the original submission.

Pushed to drm-intel-next, thanks for the reviews and acks.

BR,
Jani.

>
> Jani Nikula (6):
>   drm/mst: read sideband messaging cap
>   drm/i915/mst: improve debug logging of DP MST mode detect
>   drm/i915/mst: abstract choosing the MST mode to use
>   drm/i915/mst: use the MST mode detected previously
>   drm/i915/mst: add intel_dp_mst_disconnect()
>   drm/i915/mst: enable MST mode for 128b/132b single-stream sideband
>
>  drivers/gpu/drm/display/drm_dp_mst_topology.c | 20 ++--
>  .../drm/i915/display/intel_display_types.h    |  1 +
>  drivers/gpu/drm/i915/display/intel_dp.c       | 95 +++++++++++++------
>  drivers/gpu/drm/nouveau/nouveau_dp.c          |  2 +-
>  include/drm/display/drm_dp_mst_helper.h       | 23 ++++-
>  5 files changed, 104 insertions(+), 37 deletions(-)

-- 
Jani Nikula, Intel