drm: Check the fb size against the adjusted v/hdisplay for stereo modes

Some stereo modes, like frame packing, need a larger CRTC viewport than
the "natural" underlying 2D mode and thus drm_crtc_check_viewport()
needs to query the adjusted mode to use the correct h/vdisplay.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_crtc.c

@@ -2078,6 +2078,14 @@ static int drm_crtc_check_viewport(const struct drm_crtc *crtc,
 	hdisplay = mode->hdisplay;
 	vdisplay = mode->vdisplay;
 
+	if (drm_mode_is_stereo(mode)) {
+		struct drm_display_mode adjusted = *mode;
+
+		drm_mode_set_crtcinfo(&adjusted, CRTC_STEREO_DOUBLE);
+		hdisplay = adjusted.crtc_hdisplay;
+		vdisplay = adjusted.crtc_vdisplay;
+	}
+
 	if (crtc->invert_dimensions)
 		swap(hdisplay, vdisplay);