drm/omap: use dma_mapping_error in omap_gem_dma_sync

omap_gem_dma_sync() calls dma_map_page() but does not check the possible
error with dma_mapping_error(). If DMA-API debugging is enabled, the
debug layer will give a warning if dma_mapping_error() has not been
used.

This patch adds proper error handling to omap_gem_dma_sync().

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/gpu/drm/omapdrm/omap_gem.c

@@ -776,9 +776,20 @@ void omap_gem_dma_sync(struct drm_gem_object *obj,
 
 		for (i = 0; i < npages; i++) {
 			if (!omap_obj->addrs[i]) {
-				omap_obj->addrs[i] = dma_map_page(dev->dev, pages[i], 0,
+				dma_addr_t addr;
+
+				addr = dma_map_page(dev->dev, pages[i], 0,
 						PAGE_SIZE, DMA_BIDIRECTIONAL);
+
+				if (dma_mapping_error(dev->dev, addr)) {
+					dev_warn(dev->dev,
+						"%s: failed to map page\n",
+						__func__);
+					break;
+				}
+
 				dirty = true;
+				omap_obj->addrs[i] = addr;
 			}
 		}