drm/nv40/therm: disable temperature reading if the bios misses some parameters

Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Martin Peres <martin.peres@labri.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/subdev/therm/nv40.c

@@ -93,12 +93,10 @@ nv40_temp_get(struct nouveau_therm *therm)
 	} else
 		return -ENODEV;
 
-	if (sensor->slope_div == 0)
-		sensor->slope_div = 1;
-	if (sensor->offset_den == 0)
-		sensor->offset_den = 1;
-	if (sensor->slope_mult < 1)
-		sensor->slope_mult = 1;
+	/* if the slope or the offset is unset, do no use the sensor */
+	if (!sensor->slope_div || !sensor->slope_mult ||
+	    !sensor->offset_num || !sensor->offset_den)
+	    return -ENODEV;
 
 	core_temp = core_temp * sensor->slope_mult / sensor->slope_div;
 	core_temp = core_temp + sensor->offset_num / sensor->offset_den;

drivers/gpu/drm/nouveau/core/subdev/therm/temp.c

@@ -34,10 +34,6 @@ nouveau_therm_temp_set_defaults(struct nouveau_therm *therm)
 {
 	struct nouveau_therm_priv *priv = (void *)therm;
 
-	priv->bios_sensor.slope_mult = 1;
-	priv->bios_sensor.slope_div = 1;
-	priv->bios_sensor.offset_num = 0;
-	priv->bios_sensor.offset_den = 1;
 	priv->bios_sensor.offset_constant = 0;
 
 	priv->bios_sensor.thrs_fan_boost.temp = 90;
@@ -60,11 +56,6 @@ nouveau_therm_temp_safety_checks(struct nouveau_therm *therm)
 	struct nouveau_therm_priv *priv = (void *)therm;
 	struct nvbios_therm_sensor *s = &priv->bios_sensor;
 
-	if (!priv->bios_sensor.slope_div)
-		priv->bios_sensor.slope_div = 1;
-	if (!priv->bios_sensor.offset_den)
-		priv->bios_sensor.offset_den = 1;
-
 	/* enforce a minimum hysteresis on thresholds */
 	s->thrs_fan_boost.hysteresis = max_t(u8, s->thrs_fan_boost.hysteresis, 2);
 	s->thrs_down_clock.hysteresis = max_t(u8, s->thrs_down_clock.hysteresis, 2);