drm/amd/display: add debug logs for dm_crtc_helper_atomic_check

Instead of silently failing the atomic check, explain what happened via
a debug log. This makes it easier for user-space to figure out why
something failed.
Signed-off-by: Simon Ser <contact@emersion.fr>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Harry Wentland <hwentlan@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -6071,8 +6071,10 @@ static int dm_crtc_helper_atomic_check(struct drm_crtc *crtc,
 	 * userspace which stops using the HW cursor altogether in response to the resulting EINVAL.
 	 */
 	if (crtc_state->enable &&
-	    !(crtc_state->plane_mask & drm_plane_mask(crtc->primary)))
+	    !(crtc_state->plane_mask & drm_plane_mask(crtc->primary))) {
+		DRM_DEBUG_ATOMIC("Can't enable a CRTC without enabling the primary plane\n");
 		return -EINVAL;
+	}
 
 	/* In some use cases, like reset, no stream is attached */
 	if (!dm_crtc_state->stream)
@@ -6081,6 +6083,7 @@ static int dm_crtc_helper_atomic_check(struct drm_crtc *crtc,
 	if (dc_validate_stream(dc, dm_crtc_state->stream) == DC_OK)
 		return 0;
 
+	DRM_DEBUG_ATOMIC("Failed DC stream validation\n");
 	return ret;
 }