[bsp/qemu-vexpress-a9] add remount operation to avoid dfs_mout fail (#6018)

bsp/qemu-vexpress-a9/applications/mnt.c

@@ -10,6 +10,10 @@
 
 #include <rtthread.h>
 
+#define DBG_TAG     "FileSystem"
+#define DBG_LVL     DBG_INFO
+#include <rtdbg.h>
+
 #ifdef RT_USING_DFS
 #include <dfs_fs.h>
 
@@ -19,10 +23,25 @@ int mnt_init(void)
 
     if (dfs_mount("sd0", "/", "elm", 0, 0) == 0)
     {
-        rt_kprintf("file system initialization done!\n");
+        LOG_I("file system initialization done!\n");
+        return 0;
     }
+    else
+    {
+        LOG_W("[sd0] File System on SD ('sd0') initialization failed!");
+        LOG_W("[sd0] Try to format and re-mount...");
+        if (dfs_mkfs("elm", "sd0") == 0)
+        {
+            if (dfs_mount("sd0", "/", "elm", 0, 0) == 0)
+            {
+                LOG_I("[sd0] File System on SD ('sd0') initialized!");
+                return 0;
+            }
+        }
 
-    return 0;
+        LOG_E("[sd0] File System on SD ('sd0') initialization failed!");
+        return -1;
+    }
 }
 INIT_ENV_EXPORT(mnt_init);
 #endif