Merge branch 'usb-boot' into 'master'

try booting from USB first

See merge request !5

board/boundary/nitrogen8m_som/nitrogen8m_som.c

@@ -343,19 +343,22 @@ static void set_env_vars(void)
 	env_set("kernel_addr_r", "0x40480000");
 	env_set("fdt_addr_r", "0x50000000");
 	env_set("ramdisk_addr_r", "0x51000000");
-	env_set("devtype", "mmc");
 	env_set("bootpart", "1");
 	env_set("script", "boot.scr");
 	env_set("bootcmd",
+			"usb start; "
+			"setenv devtype; "            // unset environment variable so that the loop variable takes precedence
+			"for devtype in usb mmc; do " // first try usb, then SD card or eMMC
 				"setenv devnum; "         // unset environment variable so that the loop variable takes precedence
-			"for devnum in 1 0; do " // first try SD card then eMMC
+				"for devnum in 1 0; do "  // first try SD card (mmc1) then eMMC (mmc0)
 					"${devtype} dev ${devnum}; "
-				"if ${devtype} rescan; then "
+					"if test \"${devtype}\" = \"usb\" || ${devtype} rescan; then "
 						"setenv prefix; " // unset environment variable so that the loop variable takes precedence
 						"for prefix in / /boot/; do " // search for boot.scr in / and in /boot/
 							"load ${devtype} ${devnum}:${bootpart} ${loadaddr} ${prefix}${script} && source; "
 						"done; "
 					"fi; "
+				"done; "
 			"done"
 		);
 #endif