diff --git a/drivers/mtd/maps/physmap-core.c b/drivers/mtd/maps/physmap-core.c
index fc8721339282..9be71b045b25 100644
--- a/drivers/mtd/maps/physmap-core.c
+++ b/drivers/mtd/maps/physmap-core.c
@@ -523,7 +523,7 @@ static int physmap_flash_probe(struct platform_device *dev)
 		if (!info->maps[i].phys)
 			info->maps[i].phys = res->start;
 
-		info->win_order = get_bitmask_order(resource_size(res)) - 1;
+		info->win_order = fls64(resource_size(res)) - 1;
 		info->maps[i].size = BIT(info->win_order +
 					 (info->gpios ?
 					  info->gpios->ndescs : 0));