drm/nouveau/hwmon: return EINVAL if the GPU is powered down for sensors reads

fixes bogus values userspace gets from hwmon while the GPU is powered down
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Rhys Kidd <rhyskidd@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_hwmon.c

@@ -428,6 +428,8 @@ nouveau_temp_read(struct device *dev, u32 attr, int channel, long *val)
 
 	switch (attr) {
 	case hwmon_temp_input:
+		if (drm_dev->switch_power_state != DRM_SWITCH_POWER_ON)
+			return -EINVAL;
 		ret = nvkm_therm_temp_get(therm);
 		*val = ret < 0 ? ret : (ret * 1000);
 		break;
@@ -474,6 +476,8 @@ nouveau_fan_read(struct device *dev, u32 attr, int channel, long *val)
 
 	switch (attr) {
 	case hwmon_fan_input:
+		if (drm_dev->switch_power_state != DRM_SWITCH_POWER_ON)
+			return -EINVAL;
 		*val = nvkm_therm_fan_sense(therm);
 		break;
 	default:
@@ -496,6 +500,8 @@ nouveau_in_read(struct device *dev, u32 attr, int channel, long *val)
 
 	switch (attr) {
 	case hwmon_in_input:
+		if (drm_dev->switch_power_state != DRM_SWITCH_POWER_ON)
+			return -EINVAL;
 		ret = nvkm_volt_get(volt);
 		*val = ret < 0 ? ret : (ret / 1000);
 		break;
@@ -527,6 +533,8 @@ nouveau_pwm_read(struct device *dev, u32 attr, int channel, long *val)
 		*val = therm->attr_get(therm, NVKM_THERM_ATTR_FAN_MODE);
 		break;
 	case hwmon_pwm_input:
+		if (drm_dev->switch_power_state != DRM_SWITCH_POWER_ON)
+			return -EINVAL;
 		*val = therm->fan_get(therm);
 		break;
 	default:
@@ -548,6 +556,8 @@ nouveau_power_read(struct device *dev, u32 attr, int channel, long *val)
 
 	switch (attr) {
 	case hwmon_power_input:
+		if (drm_dev->switch_power_state != DRM_SWITCH_POWER_ON)
+			return -EINVAL;
 		*val = nvkm_iccsense_read_all(iccsense);
 		break;
 	case hwmon_power_max: