drm/amd/display: Set LTTPR Transparent Mode after read link cap

[WHY]
SCR for DP 2.0 Spec states that a DPTX shall put LTTPRs into Transparent
mode after reading LTTPR Capability registers on HPD.

The wording of the SCR is somewhat ambiguous as to whether
Transparent mode must be set explicity, or is implicitly set on LTTPR
capability read. Explicitly setting Transparent mode after LTTPR
capability read should cover all
cases.

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 38fabaff51eaec37acd42a503d38844c55cbf3f4..586f05a6cd77f89a74d35c278d312a3eddfb78b6 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -3705,9 +3705,10 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link)
                                link->dpcd_caps.lttpr_caps.max_lane_count > 0 &&
                                link->dpcd_caps.lttpr_caps.max_lane_count <= 4 &&
                                link->dpcd_caps.lttpr_caps.revision.raw >= 0x14);
-               if (is_lttpr_present)
+               if (is_lttpr_present) {
                        CONN_DATA_DETECT(link, lttpr_dpcd_data, sizeof(lttpr_dpcd_data), "LTTPR Caps: ");
-               else
+                       configure_lttpr_mode_transparent(link);
+               } else
                        link->lttpr_mode = LTTPR_MODE_NON_LTTPR;
        }
        return is_lttpr_present;