drm/amd/display: Validate function returns

[WHAT & HOW]
Function return values must be checked before data can be used
in subsequent functions.

This fixes 4 CHECKED_RETURN issues reported by Coverity.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Hung <alex.hung@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/dc_dmub_srv.c

@@ -245,7 +245,9 @@ bool dc_dmub_srv_cmd_run_list(struct dc_dmub_srv *dc_dmub_srv, unsigned int coun
 			if (status == DMUB_STATUS_POWER_STATE_D3)
 				return false;
 
-			dmub_srv_wait_for_idle(dmub, 100000);
+			status = dmub_srv_wait_for_idle(dmub, 100000);
+			if (status != DMUB_STATUS_OK)
+				return false;
 
 			/* Requeue the command. */
 			status = dmub_srv_cmd_queue(dmub, &cmd_list[i]);
@@ -517,7 +519,8 @@ void dc_dmub_srv_get_visual_confirm_color_cmd(struct dc *dc, struct pipe_ctx *pi
 	union dmub_rb_cmd cmd = { 0 };
 	unsigned int panel_inst = 0;
 
-	dc_get_edp_link_panel_inst(dc, pipe_ctx->stream->link, &panel_inst);
+	if (!dc_get_edp_link_panel_inst(dc, pipe_ctx->stream->link, &panel_inst))
+		return;
 
 	memset(&cmd, 0, sizeof(cmd));
 

drivers/gpu/drm/amd/display/dc/hubbub/dcn20/dcn20_hubbub.c

@@ -616,7 +616,8 @@ static bool hubbub2_program_watermarks(
 		hubbub1->base.ctx->dc->clk_mgr->clks.p_state_change_support == false)
 		safe_to_lower = true;
 
-	hubbub1_program_pstate_watermarks(hubbub, watermarks, refclk_mhz, safe_to_lower);
+	if (hubbub1_program_pstate_watermarks(hubbub, watermarks, refclk_mhz, safe_to_lower))
+		wm_pending = true;
 
 	REG_SET(DCHUBBUB_ARB_SAT_LEVEL, 0,
 			DCHUBBUB_ARB_SAT_LEVEL, 60 * refclk_mhz);

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c

@@ -1663,8 +1663,7 @@ bool perform_link_training_with_retries(
 		if (status == LINK_TRAINING_ABORT) {
 			enum dc_connection_type type = dc_connection_none;
 
-			link_detect_connection_type(link, &type);
-			if (type == dc_connection_none) {
+			if (link_detect_connection_type(link, &type) && type == dc_connection_none) {
 				DC_LOG_HW_LINK_TRAINING("%s: Aborting training because sink unplugged\n", __func__);
 				break;
 			}