drm/amd/display: Implement fixed DP drive settings

[Why]
Currently there are use cases that require DP link to maintain fixed VS
and PE in HW regardless of what the sink requests. BIOS integrated info
table will specify whether we need to use the fixed drive settings, and
the drive settings to use.

[How]
Implement changes to parse the integrated info table and set the fixed
drive settings accordingly.

Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Acked-by: Agustin Gutierrez <agustin.gutierrez@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

4 files changed, 20 insertions, 1 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c b/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
index c17732fba039..a4bef4364afd 100644
--- a/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
+++ b/drivers/gpu/drm/amd/display/dc/bios/bios_parser2.c
@@ -2321,6 +2321,8 @@ static enum bp_result get_integrated_info_v2_2(
 
 	info->ext_disp_conn_info.checksum =
 		info_v2_2->extdispconninfo.checksum;
+	info->ext_disp_conn_info.fixdpvoltageswing =
+		info_v2_2->extdispconninfo.fixdpvoltageswing;
 
 	info->edp1_info.edp_backlight_pwm_hz =
 	le16_to_cpu(info_v2_2->edp1_info.edp_backlight_pwm_hz);
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index 96d2001ede61..a1fa50ddf43e 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -1660,6 +1660,14 @@ static bool dc_link_construct_legacy(struct dc_link *link,
 				DC_LOG_DC("BIOS object table - ddi_channel_mapping: 0x%04X", link->ddi_channel_mapping.raw);
 				DC_LOG_DC("BIOS object table - chip_caps: %d", link->chip_caps);
 			}
+
+			if (link->chip_caps & EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN) {
+				link->bios_forced_drive_settings.VOLTAGE_SWING =
+						(info->ext_disp_conn_info.fixdpvoltageswing & 0x3);
+				link->bios_forced_drive_settings.PRE_EMPHASIS =
+						((info->ext_disp_conn_info.fixdpvoltageswing >> 2) & 0x3);
+			}
+
 			break;
 		}
 	}
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index e514506b1997..3313f2af139f 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -1661,7 +1661,13 @@ static void override_training_settings(
 	if (overrides->ffe_preset != NULL)
 		lt_settings->ffe_preset = overrides->ffe_preset;
 #endif
-
+	/* Override HW lane settings with BIOS forced values if present */
+	if (link->chip_caps & EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN &&
+			link->lttpr_mode == LTTPR_MODE_TRANSPARENT) {
+		lt_settings->voltage_swing = &link->bios_forced_drive_settings.VOLTAGE_SWING;
+		lt_settings->pre_emphasis = &link->bios_forced_drive_settings.PRE_EMPHASIS;
+		lt_settings->always_match_dpcd_with_hw_lane_settings = false;
+	}
 	for (lane = 0; lane < LANE_COUNT_DP_MAX; lane++) {
 		lt_settings->lane_settings[lane].VOLTAGE_SWING =
 			lt_settings->voltage_swing != NULL ?
diff --git a/drivers/gpu/drm/amd/display/dc/dc_link.h b/drivers/gpu/drm/amd/display/dc/dc_link.h
index 8902d642e719..517950674729 100644
--- a/drivers/gpu/drm/amd/display/dc/dc_link.h
+++ b/drivers/gpu/drm/amd/display/dc/dc_link.h
@@ -178,6 +178,9 @@ struct dc_link {
 
 	struct psr_settings psr_settings;
 
+	/* Drive settings read from integrated info table */
+	struct dc_lane_settings bios_forced_drive_settings;
+
 	/* MST record stream using this link */
 	struct link_flags {
 		bool dp_keep_receiver_powered;