drm/nouveau: fail runtime pm properly.

If we were on a non-optimus device, we'd return -EINVAL, this would
lead to the over engineered runtime pm system to go into an error
state, subsequent get_sync's would fail, so we'd never be able
to open the device again.

(like really get_sync shouldn't fail if the device isn't powered
down).

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/nouveau/nouveau_drm.c

@@ -866,13 +866,16 @@ static int nouveau_pmops_runtime_suspend(struct device *dev)
 	struct drm_device *drm_dev = pci_get_drvdata(pdev);
 	int ret;
 
-	if (nouveau_runtime_pm == 0)
-		return -EINVAL;
+	if (nouveau_runtime_pm == 0) {
+		pm_runtime_forbid(dev);
+		return -EBUSY;
+	}
 
 	/* are we optimus enabled? */
 	if (nouveau_runtime_pm == -1 && !nouveau_is_optimus() && !nouveau_is_v1_dsm()) {
 		DRM_DEBUG_DRIVER("failing to power off - not optimus\n");
-		return -EINVAL;
+		pm_runtime_forbid(dev);
+		return -EBUSY;
 	}
 
 	nv_debug_level(SILENT);
@@ -923,12 +926,15 @@ static int nouveau_pmops_runtime_idle(struct device *dev)
 	struct nouveau_drm *drm = nouveau_drm(drm_dev);
 	struct drm_crtc *crtc;
 
-	if (nouveau_runtime_pm == 0)
+	if (nouveau_runtime_pm == 0) {
+		pm_runtime_forbid(dev);
 		return -EBUSY;
+	}
 
 	/* are we optimus enabled? */
 	if (nouveau_runtime_pm == -1 && !nouveau_is_optimus() && !nouveau_is_v1_dsm()) {
 		DRM_DEBUG_DRIVER("failing to power off - not optimus\n");
+		pm_runtime_forbid(dev);
 		return -EBUSY;
 	}