drm/amd/display: Fix incorrect return of vblank enable on unconfigured crtc

[Why&How]
Return -EINVAL when userspace asks us to enable vblank on a crtc that is
not yet enabled.

Suggested-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/1856
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit cb57b8c)
Cc: stable@vger.kernel.org

Author: Ivan Lipski

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c

@@ -308,8 +308,12 @@ static inline int amdgpu_dm_crtc_set_vblank(struct drm_crtc *crtc, bool enable)
 	int irq_type;
 	int rc = 0;
 
-	if (acrtc->otg_inst == -1)
-		goto skip;
+	if (enable && !acrtc->base.enabled) {
+		drm_dbg_vbl(crtc->dev,
+				"Reject vblank enable on unconfigured CRTC %d (enabled=%d)\n",
+				acrtc->crtc_id, acrtc->base.enabled);
+		return -EINVAL;
+	}
 
 	irq_type = amdgpu_display_crtc_idx_to_irq_type(adev, acrtc->crtc_id);
 
@@ -394,7 +398,7 @@ static inline int amdgpu_dm_crtc_set_vblank(struct drm_crtc *crtc, bool enable)
 			return rc;
 	}
 #endif
-skip:
+
 	if (amdgpu_in_reset(adev))
 		return 0;