drm/amd/display: Read LTTPR caps first on bootup

[WHY]
SCR for DP 2.0 requires that LTTPR caps be read first on hotplug.
For the sake of consistency, this should also be the case on bootup.
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>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c

@@ -54,6 +54,7 @@
 #include "dce/dmub_hw_lock_mgr.h"
 #include "dc_trace.h"
 #include "dce/dmub_outbox.h"
+#include "inc/dc_link_dp.h"
 
 #define DC_LOGGER_INIT(logger)
 
@@ -1403,6 +1404,9 @@ void dcn10_init_hw(struct dc *dc)
 			if (dc->links[i]->connector_signal != SIGNAL_TYPE_DISPLAY_PORT)
 				continue;
 
+			/* DP 2.0 requires that LTTPR Caps be read first */
+			dp_retrieve_lttpr_cap(dc->links[i]);
+
 			/*
 			 * If any of the displays are lit up turn them off.
 			 * The reason is that some MST hubs cannot be turned off

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_hwseq.c

@@ -48,6 +48,7 @@
 #include "dc_dmub_srv.h"
 #include "link_hwss.h"
 #include "dpcd_defs.h"
+#include "inc/dc_link_dp.h"
 
 
 
@@ -529,6 +530,8 @@ void dcn30_init_hw(struct dc *dc)
 		for (i = 0; i < dc->link_count; i++) {
 			if (dc->links[i]->connector_signal != SIGNAL_TYPE_DISPLAY_PORT)
 				continue;
+			/* DP 2.0 states that LTTPR regs must be read first */
+			dp_retrieve_lttpr_cap(dc->links[i]);
 
 			/* if any of the displays are lit up turn them off */
 			status = core_link_read_dpcd(dc->links[i], DP_SET_POWER,

drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h

@@ -190,4 +190,5 @@ enum dc_status dpcd_configure_lttpr_mode(
 		struct link_training_settings *lt_settings);
 
 enum dp_link_encoding dp_get_link_encoding_format(const struct dc_link_settings *link_settings);
+bool dp_retrieve_lttpr_cap(struct dc_link *link);
 #endif /* __DC_LINK_DP_H__ */