drm/amd/display: add workaround flag to link to force FFE preset

[Why]
There have been instances of some monitors being unable to link train on
their reported link speed using their selected FFE preset. If a different
FFE preset is found that has a higher rate of success during link training
this workaround can be used to force its FFE preset.

[How]
A new link workaround flag is made called force_dp_ffe_preset. The flag is
checked in override_training_settings and will set lt_settings->ffe_preset
which is null if the flag is not set. The flag is then set in
override_lane_settings.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Brendan Tam <Brendan.Tam@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h
index e1f4f643c3647c0468b91eb62082cb8ac52a6eb7..16cd7833e931834deb25d75545abc9480db7b8b0 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dc.h
+++ b/drivers/gpu/drm/amd/display/dc/dc.h
@@ -1792,7 +1792,9 @@ struct dc_link {
                bool dongle_mode_timing_override;
                bool blank_stream_on_ocs_change;
                bool read_dpcd204h_on_irq_hpd;
+               bool force_dp_ffe_preset;
        } wa_flags;
+       union dc_dp_ffe_preset forced_dp_ffe_preset;
        struct link_mst_stream_allocation_table mst_stream_alloc_table;
 
        struct dc_link_status link_status;

diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c
index 88d4288cde0f5869a72094192a27e78bd8068a51..751c18e592ea5ef1cd774de0dbf687a38f011ec1 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c
+++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c
@@ -736,6 +736,8 @@ void override_training_settings(
                lt_settings->pre_emphasis = overrides->pre_emphasis;
        if (overrides->post_cursor2 != NULL)
                lt_settings->post_cursor2 = overrides->post_cursor2;
+       if (link->wa_flags.force_dp_ffe_preset && !dp_is_lttpr_present(link))
+               lt_settings->ffe_preset = &link->forced_dp_ffe_preset;
        if (overrides->ffe_preset != NULL)
                lt_settings->ffe_preset = overrides->ffe_preset;
        /* Override HW lane settings with BIOS forced values if present */