From: Brendan Tam Brendan.Tam@amd.com
[ Upstream commit 51d1b338541dea83fec8e6f95d3e46fa469a73a8 ]
[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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 cc5e01df15135..88e64b280c90f 100644 --- a/drivers/gpu/drm/amd/display/dc/dc.h +++ b/drivers/gpu/drm/amd/display/dc/dc.h @@ -1563,7 +1563,9 @@ 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 9d1adfc09fb2a..51e88efee11e4 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 @@ -697,6 +697,8 @@ 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 */