drm/amd/display: Add debug option to disable dmcu

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/dc.h

@@ -147,6 +147,7 @@ struct dc_debug {
 	bool disable_dfs_bypass;
 	bool disable_power_gate;
 	bool disable_clock_gate;
+	bool disable_dmcu;
 };
 
 struct dc {

drivers/gpu/drm/amd/display/dc/dce/dce_link_encoder.c

@@ -1821,6 +1821,9 @@ void dce110_link_encoder_init_dmcu_backlight_settings(
 	uint32_t s2;
 	uint32_t value;
 
+	if (enc->ctx->dc->debug.disable_dmcu)
+		return;
+
 	bl_pwm_cntl = REG_READ(BL_PWM_CNTL);
 
 	/* It must not be 0, so we have to restore them