drm/amd/display: Keep eDP stream enabled during boot.

This path fixed specific eDP panel cold boot black screen
due to unnecessary enable link.
Change:
In case of boot up with eDP, if OS is going to set mode
on eDP, keep eDP light up, do not disable and reset corresponding
HW.
This change may affect dce asics and S3/S4 Resume with multi-monitor.
Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -2296,7 +2296,16 @@ void core_link_enable_stream(
 {
 	struct dc  *core_dc = pipe_ctx->stream->ctx->dc;
 
-	enum dc_status status = enable_link(state, pipe_ctx);
+	enum dc_status status;
+
+	/* eDP lit up by bios already, no need to enable again. */
+	if (pipe_ctx->stream->signal == SIGNAL_TYPE_EDP &&
+		core_dc->apply_edp_fast_boot_optimization) {
+		core_dc->apply_edp_fast_boot_optimization = false;
+		return;
+	}
+
+	status = enable_link(state, pipe_ctx);
 
 	if (status != DC_OK) {
 			dm_logger_write(pipe_ctx->stream->ctx->logger,

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

@@ -257,6 +257,8 @@ struct dc {
 
 	bool optimized_required;
 
+	bool apply_edp_fast_boot_optimization;
+
 	/* FBC compressor */
 #if defined(CONFIG_DRM_AMD_DC_FBC)
 	struct compressor *fbc_compressor;

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -57,6 +57,8 @@
 #include "dce/dce_11_0_sh_mask.h"
 #include "custom_float.h"
 
+#include "atomfirmware.h"
+
 /*
  * All values are in milliseconds;
  * For eDP, after power-up/power/down,
@@ -1425,23 +1427,6 @@ static void disable_vga_and_power_gate_all_controllers(
 	}
 }
 
-static struct dc_link *get_link_for_edp(
-		struct dc *dc)
-{
-	int i;
-	struct dc_link *link = NULL;
-
-	/* check if there is an eDP panel not in use */
-	for (i = 0; i < dc->link_count; i++) {
-		if (dc->links[i]->local_sink &&
-			dc->links[i]->local_sink->sink_signal == SIGNAL_TYPE_EDP) {
-			link = dc->links[i];
-			break;
-		}
-	}
-
-	return link;
-}
 static struct dc_link *get_link_for_edp_not_in_use(
 		struct dc *dc,
 		struct dc_state *context)
@@ -1477,13 +1462,27 @@ static struct dc_link *get_link_for_edp_not_in_use(
 void dce110_enable_accelerated_mode(struct dc *dc, struct dc_state *context)
 {
 	struct dc_bios *dcb = dc->ctx->dc_bios;
-	struct dc_link *edp_link_to_turnoff = get_link_for_edp_not_in_use(dc, context);
 
-	struct dc_link *edp_link = get_link_for_edp(dc);
-	if (dcb->funcs->get_vga_enabled_displays(dc->ctx->dc_bios) != 0) {
-		if (edp_link) {
-			/*we need turn off backlight before DP_blank and encoder powered down, todo add optimization*/
-			dc->hwss.edp_backlight_control(edp_link, false);
+	/* vbios already light up eDP, so we can leverage vbios and skip eDP
+	 * programming
+	 */
+	bool can_eDP_fast_boot_optimize =
+			(dcb->funcs->get_vga_enabled_displays(dc->ctx->dc_bios) == ATOM_DISPLAY_LCD1_ACTIVE);
+
+	/* if OS doesn't light up eDP and eDP link is available, we want to disable */
+	struct dc_link *edp_link_to_turnoff = NULL;
+
+	if (can_eDP_fast_boot_optimize) {
+		edp_link_to_turnoff = get_link_for_edp_not_in_use(dc, context);
+
+		if (!edp_link_to_turnoff)
+			dc->apply_edp_fast_boot_optimization = true;
+	}
+
+	if (!dc->apply_edp_fast_boot_optimization) {
+		if (edp_link_to_turnoff) {
+			/*turn off backlight before DP_blank and encoder powered down*/
+			dc->hwss.edp_backlight_control(edp_link_to_turnoff, false);
 		}
 		/*resume from S3, no vbios posting, no need to power down again*/
 		power_down_all_hw_blocks(dc);