diff --git a/sys/dev/drm/amd/powerplay/smumgr/iceland_smumgr.c b/sys/dev/drm/amd/powerplay/smumgr/iceland_smumgr.c
--- a/sys/dev/drm/amd/powerplay/smumgr/iceland_smumgr.c
+++ b/sys/dev/drm/amd/powerplay/smumgr/iceland_smumgr.c
@@ -2122,6 +2122,12 @@
 	t_diff1 = hwmgr->thermal_controller.advanceFanControlParameters.usTMed - hwmgr->thermal_controller.advanceFanControlParameters.usTMin;
 	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 - hwmgr->thermal_controller.advanceFanControlParameters.usPWMMed;