[PATCH 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 at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula at 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 3956604d8b00..4787dc15797a 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4069,7 +4069,8 @@ 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