drm/amd/display: Assume LTTPR interop for DCN31+

[WHY]
For DCN31 onward, LTTPR is to be enabled and set to Transparent by
VBIOS.  Driver is to assume that VBIOS has done this without needing to
check the VBIOS interop bit.

[HOW]
Add LTTPR enable and interop VBIOS bits into dc->caps, and force-set the
interop bit to true for DCN31+.
Reviewed-by: NJun Lei <Jun.Lei@amd.com>
Acked-by: NAurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: NWesley Chalmers <Wesley.Chalmers@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -3595,29 +3595,12 @@ static bool dpcd_read_sink_ext_caps(struct dc_link *link)
 bool dp_retrieve_lttpr_cap(struct dc_link *link)
 {
 	uint8_t lttpr_dpcd_data[6];
-	bool vbios_lttpr_enable = false;
-	bool vbios_lttpr_interop = false;
-	struct dc_bios *bios = link->dc->ctx->dc_bios;
+	bool vbios_lttpr_enable = link->dc->caps.vbios_lttpr_enable;
+	bool vbios_lttpr_interop = link->dc->caps.vbios_lttpr_aware;
 	enum dc_status status = DC_ERROR_UNEXPECTED;
 	bool is_lttpr_present = false;
 
 	memset(lttpr_dpcd_data, '\0', sizeof(lttpr_dpcd_data));
-	/* Query BIOS to determine if LTTPR functionality is forced on by system */
-	if (bios->funcs->get_lttpr_caps) {
-		enum bp_result bp_query_result;
-		uint8_t is_vbios_lttpr_enable = 0;
-
-		bp_query_result = bios->funcs->get_lttpr_caps(bios, &is_vbios_lttpr_enable);
-		vbios_lttpr_enable = (bp_query_result == BP_RESULT_OK) && !!is_vbios_lttpr_enable;
-	}
-
-	if (bios->funcs->get_lttpr_interop) {
-		enum bp_result bp_query_result;
-		uint8_t is_vbios_interop_enabled = 0;
-
-		bp_query_result = bios->funcs->get_lttpr_interop(bios, &is_vbios_interop_enabled);
-		vbios_lttpr_interop = (bp_query_result == BP_RESULT_OK) && !!is_vbios_interop_enabled;
-	}
 
 	/*
 	 * Logic to determine LTTPR mode

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

@@ -183,6 +183,8 @@ struct dc_caps {
 	unsigned int cursor_cache_size;
 	struct dc_plane_cap planes[MAX_PLANES];
 	struct dc_color_caps color;
+	bool vbios_lttpr_aware;
+	bool vbios_lttpr_enable;
 };
 
 struct dc_bug_wa {

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_resource.c

@@ -2617,6 +2617,26 @@ static bool dcn30_resource_construct(
 	dc->caps.color.mpc.ogam_rom_caps.hlg = 0;
 	dc->caps.color.mpc.ocsc = 1;
 
+	/* read VBIOS LTTPR caps */
+	{
+		if (ctx->dc_bios->funcs->get_lttpr_caps) {
+			enum bp_result bp_query_result;
+			uint8_t is_vbios_lttpr_enable = 0;
+
+			bp_query_result = ctx->dc_bios->funcs->get_lttpr_caps(ctx->dc_bios, &is_vbios_lttpr_enable);
+			dc->caps.vbios_lttpr_enable = (bp_query_result == BP_RESULT_OK) && !!is_vbios_lttpr_enable;
+		}
+
+		if (ctx->dc_bios->funcs->get_lttpr_interop) {
+			enum bp_result bp_query_result;
+			uint8_t is_vbios_interop_enabled = 0;
+
+			bp_query_result = ctx->dc_bios->funcs->get_lttpr_interop(ctx->dc_bios,
+					&is_vbios_interop_enabled);
+			dc->caps.vbios_lttpr_aware = (bp_query_result == BP_RESULT_OK) && !!is_vbios_interop_enabled;
+		}
+	}
+
 	if (dc->ctx->dce_environment == DCE_ENV_PRODUCTION_DRV)
 		dc->debug = debug_defaults_drv;
 	else if (dc->ctx->dce_environment == DCE_ENV_FPGA_MAXIMUS) {

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_resource.c

@@ -1968,6 +1968,22 @@ static bool dcn31_resource_construct(
 	dc->caps.color.mpc.ogam_rom_caps.hlg = 0;
 	dc->caps.color.mpc.ocsc = 1;
 
+	/* read VBIOS LTTPR caps */
+	{
+		if (ctx->dc_bios->funcs->get_lttpr_caps) {
+			enum bp_result bp_query_result;
+			uint8_t is_vbios_lttpr_enable = 0;
+
+			bp_query_result = ctx->dc_bios->funcs->get_lttpr_caps(ctx->dc_bios, &is_vbios_lttpr_enable);
+			dc->caps.vbios_lttpr_enable = (bp_query_result == BP_RESULT_OK) && !!is_vbios_lttpr_enable;
+		}
+
+		/* interop bit is implicit */
+		{
+			dc->caps.vbios_lttpr_aware = true;
+		}
+	}
+
 	if (dc->ctx->dce_environment == DCE_ENV_PRODUCTION_DRV)
 		dc->debug = debug_defaults_drv;
 	else if (dc->ctx->dce_environment == DCE_ENV_FPGA_MAXIMUS) {