ARM: zynq: Add uEnv.txt support

preboot macro load the uEnv.txt from mmc 0 when bootmode is mmc. uenvcmd is
executed after load of uEnv.txt if it is defined in the uEnv.txt env text
file.

The default importbootenv macro reads the uEnv.txt from mmc.

Additional to this, usb_loadbootenv is added to support loading uEnv.txt
from usb dev 0.
Signed-off-by: NJason Wu <jason.wu.misc@gmail.com>
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>

include/configs/zynq-common.h

@@ -203,6 +203,9 @@
 # define CONFIG_ENV_OFFSET		0xE0000
 #endif
 
+/* enable preboot to be loaded before CONFIG_BOOTDELAY */
+#define CONFIG_PREBOOT
+
 /* Default environment */
 #ifndef CONFIG_EXTRA_ENV_SETTINGS
 #define CONFIG_EXTRA_ENV_SETTINGS	\
@@ -213,6 +216,29 @@
 	"nor_flash_off=0xE2100000\0"	\
 	"fdt_high=0x20000000\0"		\
 	"initrd_high=0x20000000\0"	\
+	"loadbootenv_addr=0x2000000\0" \
+	"bootenv=uEnv.txt\0" \
+	"bootenv_dev=mmc\0" \
+	"loadbootenv=load ${bootenv_dev} 0 ${loadbootenv_addr} ${bootenv}\0" \
+	"importbootenv=echo Importing environment from ${bootenv_dev} ...; " \
+		"env import -t ${loadbootenv_addr} $filesize\0" \
+	"bootenv_existence_test=test -e ${bootenv_dev} 0 /${bootenv}\0" \
+	"setbootenv=if env run bootenv_existence_test; then " \
+			"if env run loadbootenv; then " \
+				"env run importbootenv; " \
+			"fi; " \
+		"fi; \0" \
+	"sd_loadbootenv=set bootenv_dev mmc && " \
+			"run setbootenv \0" \
+	"usb_loadbootenv=set bootenv_dev usb && usb start && run setbootenv \0" \
+	"preboot=if test $modeboot = sdboot; then " \
+			"run sd_loadbootenv; " \
+			"echo Checking if uenvcmd is set ...; " \
+			"if test -n $uenvcmd; then " \
+				"echo Running uenvcmd ...; " \
+				"run uenvcmd; " \
+			"fi; " \
+		"fi; \0" \
 	"norboot=echo Copying FIT from NOR flash to RAM... && " \
 		"cp.b ${nor_flash_off} ${load_addr} ${fit_size} && " \
 		"bootm ${load_addr}\0" \