As explained in the previous patch, the MST link BW reported by branch devices during topology probing/path resources enumeration depends on the link parameters programmed to DPCD to be up-to-date. After a sink is plugged this is not ensured, as those DPCD values start out zeroed. The target link parameters (for a subsequent modeset) are the maximum that is supported, so make sure these maximum values are programmed before the topology probing.
Signed-off-by: Imre Deak <imre.d...@intel.com> --- drivers/gpu/drm/i915/display/intel_dp.c | 3 ++ drivers/gpu/drm/i915/display/intel_dp_mst.c | 31 +++++++++++++++++++++ drivers/gpu/drm/i915/display/intel_dp_mst.h | 1 + 3 files changed, 35 insertions(+) diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 0771e4c6357ba..41f5d82ca75d8 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -4262,6 +4262,9 @@ intel_dp_mst_configure(struct intel_dp *intel_dp) intel_dp->is_mst = intel_dp->mst_detect != DRM_DP_SST; + if (intel_dp->is_mst) + intel_dp_mst_prepare_probe(intel_dp); + drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr, intel_dp->is_mst); /* Avoid stale info on the next detect cycle. */ diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c index 19c8b6878b030..faee7af0a8a48 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c @@ -43,6 +43,7 @@ #include "intel_dp_hdcp.h" #include "intel_dp_mst.h" #include "intel_dp_tunnel.h" +#include "intel_dp_link_training.h" #include "intel_dpio_phy.h" #include "intel_hdcp.h" #include "intel_hotplug.h" @@ -2031,3 +2032,33 @@ bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state, return false; } + +/** + * intel_dp_mst_prepare_probe - Prepare an MST link for topology probing + * @intel_dp: DP port object + * + * Prepare an MST link for topology probing, programming the target + * link parameters to DPCD. This step is a requirement of the enumaration + * of path resources during probing. + */ +void intel_dp_mst_prepare_probe(struct intel_dp *intel_dp) +{ + int link_rate = intel_dp_max_link_rate(intel_dp); + int lane_count = intel_dp_max_lane_count(intel_dp); + u8 rate_select; + u8 link_bw; + + if (intel_dp->link_trained) + return; + + if (intel_mst_probed_link_params_valid(intel_dp, link_rate, lane_count)) + return; + + intel_dp_compute_rate(intel_dp, link_rate, &link_bw, &rate_select); + + intel_dp_link_training_set_mode(intel_dp, link_rate, false); + intel_dp_link_training_set_bw(intel_dp, link_bw, rate_select, lane_count, + drm_dp_enhanced_frame_cap(intel_dp->dpcd)); + + intel_mst_set_probed_link_params(intel_dp, link_rate, lane_count); +} diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.h b/drivers/gpu/drm/i915/display/intel_dp_mst.h index 8ca1d599091c6..fba76454fa67f 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_mst.h +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.h @@ -27,5 +27,6 @@ int intel_dp_mst_atomic_check_link(struct intel_atomic_state *state, struct intel_link_bw_limits *limits); bool intel_dp_mst_crtc_needs_modeset(struct intel_atomic_state *state, struct intel_crtc *crtc); +void intel_dp_mst_prepare_probe(struct intel_dp *intel_dp); #endif /* __INTEL_DP_MST_H__ */ -- 2.44.2