Commit 47c2790a authored by Michael Strauss's avatar Michael Strauss Committed by Alex Deucher
Browse files

drm/amd/display: Assume an LTTPR is always present on fixed_vs links 



[WHY]
LTTPRs can in very rare instsances fail to increment DPCD LTTPR count.
This results in aux-i LTTPR requests to be sent to the wrong DPCD
address, which causes link training failure.

[HOW]
Override internal repeater count if fixed_vs flag is set for a given link

Reviewed-by: default avatarGeorge Shen <George.Shen@amd.com>
Acked-by: default avatarWayne Lin <wayne.lin@amd.com>
Signed-off-by: default avatarMichael Strauss <michael.strauss@amd.com>
Tested-by: default avatarDaniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 62f0576c

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

+8 −0
Original line number Diff line number Diff line
@@ -5133,6 +5133,14 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link) 
				lttpr_dpcd_data[DP_PHY_REPEATER_128B132B_RATES -

								DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV];



		/* If this chip cap is set, at least one retimer must exist in the chain

		 * Override count to 1 if we receive a known bad count (0 or an invalid value) */

		if (link->chip_caps & EXT_DISPLAY_PATH_CAPS__DP_FIXED_VS_EN &&

				(dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt) == 0)) {

			ASSERT(0);

			link->dpcd_caps.lttpr_caps.phy_repeater_cnt = 0x80;

		}



		/* Attempt to train in LTTPR transparent mode if repeater count exceeds 8. */

		is_lttpr_present = (link->dpcd_caps.lttpr_caps.max_lane_count > 0 &&

				link->dpcd_caps.lttpr_caps.max_lane_count <= 4 &&