drm: Check plane src coordinates correctly during page flip for atomic drivers

Instead of relying on the old crtc-{x,y,mode} gunk, dig out the primary
plane coordinates from the plane state when checking them against the
new framebuffer during page flip.

Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1444930802-8515-5-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_crtc.c

@@ -5183,7 +5183,14 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 		goto out;
 	}
 
+	if (crtc->state) {
+		const struct drm_plane_state *state = crtc->primary->state;
+
+		ret = check_src_coords(state->src_x, state->src_y,
+				       state->src_w, state->src_h, fb);
+	} else {
 		ret = drm_crtc_check_viewport(crtc, crtc->x, crtc->y, &crtc->mode, fb);
+	}
 	if (ret)
 		goto out;