--- a/sys/dev/drm/amd/powerplay/smumgr/tonga_smumgr.c
+++ b/sys/dev/drm/amd/powerplay/smumgr/tonga_smumgr.c
@@ -2504,6 +2504,12 @@
 	t_diff2 = hwmgr->thermal_controller.advanceFanControlParameters.usTHigh -
 		  hwmgr->thermal_controller.advanceFanControlParameters.usTMed;
 
+	if (t_diff1 == 0 || t_diff2 == 0) {
+		phm_cap_unset(hwmgr->platform_descriptor.platformCaps,
+			PHM_PlatformCaps_MicrocodeFanControl);
+		return 0;
+	}
+
 	pwm_diff1 = hwmgr->thermal_controller.advanceFanControlParameters.usPWMMed -
 		    hwmgr->thermal_controller.advanceFanControlParameters.usPWMMin;
 	pwm_diff2 = hwmgr->thermal_controller.advanceFanControlParameters.usPWMHigh -