From: Brendan Tam <Brendan.Tam@xxxxxxx>
[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@xxxxxxx>
Signed-off-by: Brendan Tam <Brendan.Tam@xxxxxxx>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
---
drivers/gpu/drm/amd/display/dc/dc.h | 2 ++
.../gpu/drm/amd/display/dc/link/protocols/link_dp_training.c | 2 ++
2 files changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h
index e1f4f643c364..16cd7833e931 100644
--- 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 88d4288cde0f..751c18e592ea 100644
--- 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 */
--
2.48.1
