Reduce the link parameters after a link training failure for MST outputs, similarly to how this is done for SST.
For now allow the reduction only by staying in the 8b/10b vs. 128b/132b mode. Enabling the mode switch is left for a follow-up patchset, after taking measures ensuring that the mode switch happens properly. In particular a rediscovery of the whole MST topology may be required for such a switch, see the References below. Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/10970 Signed-off-by: Imre Deak <imre.d...@intel.com> --- drivers/gpu/drm/i915/display/intel_dp.c | 6 +----- .../gpu/drm/i915/display/intel_dp_link_training.c | 13 ++++--------- 2 files changed, 5 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 34d64fe3302ef..c8d940a2ef7af 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -5844,11 +5844,7 @@ intel_dp_detect(struct drm_connector *connector, intel_dp_mst_configure(intel_dp); - /* - * TODO: Reset link params when switching to MST mode, until MST - * supports link training fallback params. - */ - if (intel_dp->reset_link_params || intel_dp->is_mst) { + if (intel_dp->reset_link_params) { intel_dp_reset_link_params(intel_dp); intel_dp->reset_link_params = false; } diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c index 375f59afd4dec..9a59a28ca36d2 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -1124,6 +1124,10 @@ static int reduce_link_rate(struct intel_dp *intel_dp, int current_rate) new_rate = intel_dp_common_rate(intel_dp, rate_index - 1); + /* TODO: Make switching from UHBR to non-UHBR rates work. */ + if (drm_dp_is_uhbr_rate(current_rate) != drm_dp_is_uhbr_rate(new_rate)) + return -1; + return new_rate; } @@ -1142,15 +1146,6 @@ static int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp, int new_link_rate; int new_lane_count; - /* - * TODO: Enable fallback on MST links once MST link compute can handle - * the fallback params. - */ - if (intel_dp->is_mst) { - drm_err(&i915->drm, "Link Training Unsuccessful\n"); - return -1; - } - if (intel_dp_is_edp(intel_dp) && !intel_dp->use_max_params) { drm_dbg_kms(&i915->drm, "Retrying Link training for eDP with max parameters\n"); -- 2.43.3
