[PATCH 08/30] drm/amd/display: Skip DPCD read for DPTX-to-DPIA hop

[Timo Aaltonen]

From: Jimmy Kizito <Jimmy.Kizito at amd.com>

BugLink: https://bugs.launchpad.net/bugs/1951868

[why & how]
Driver does not need to train the first hop.

Reviewed-by: Jun Lei <Jun.Lei at amd.com>
Acked-by: Wayne Lin <Wayne.Lin at amd.com>
Acked-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
Acked-by: Harry Wentland <harry.wentland at amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito at amd.com>
Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
(cherry picked from commit 31cf79f05d34f4a8040bbeaaf7f03b0fb5fe117f)
Signed-off-by: Timo Aaltonen <timo.aaltonen at canonical.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 7 +++++++
 1 file changed, 7 insertions(+)

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 c132fd8feaaf..a1eb5e2d4816 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
@@ -1433,6 +1433,13 @@ enum dc_status configure_lttpr_mode_non_transparent(
 
 		if (encoding == DP_8b_10b_ENCODING) {
 			repeater_cnt = dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt);
+
+			/* Driver does not need to train the first hop. Skip DPCD read and clear
+			 * AUX_RD_INTERVAL for DPTX-to-DPIA hop.
+			 */
+			if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA)
+				link->dpcd_caps.lttpr_caps.aux_rd_interval[--repeater_cnt] = 0;
+
 			for (repeater_id = repeater_cnt; repeater_id > 0; repeater_id--) {
 				aux_interval_address = DP_TRAINING_AUX_RD_INTERVAL_PHY_REPEATER1 +
 							((DP_REPEATER_CONFIGURATION_AND_STATUS_SIZE) * (repeater_id - 1));
-- 
2.32.0