With a value of '0' read from MSTM_CAP register MST to be enabled. DP2.1 SCR updates the spec for 128/132b DP capable supporting only one stream and not supporting single stream sideband MSG. The underlying protocol will be MST to enable use of MTP. Signed-off-by: Arun R Murthy <arun.r.murthy@xxxxxxxxx> --- drivers/gpu/drm/i915/display/intel_dp.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 9ff0cbd9c0df..05722f10cdd7 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -4037,9 +4037,15 @@ intel_dp_configure_mst(struct intel_dp *intel_dp) if (!intel_dp_mst_source_support(intel_dp)) return; - - intel_dp->is_mst = sink_can_mst && - i915->display.params.enable_dp_mst; + /* + * Even if dpcd reg MSTM_CAP is 0, if the sink supports UHBR rates then + * DP2.1 can be enabled with underlying protocol using MST for MTP + * TODO: Need to accommodate MSTM_CAP bit[0]=0, bit[1]=1 condition, i.e + * one stream with single stream sideband msg. + */ + intel_dp->is_mst = (sink_can_mst || (intel_dp->dpcd[DP_MAIN_LINK_CHANNEL_CODING] & + DP_CAP_ANSI_128B132B)) && + i915->display.params.enable_dp_mst; drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst); -- 2.25.1
