arm64: zynqmp: Add support to load an app at EL1

This patch is adding support to switch to EL1 while loading an EL1
application with u-boot running at EL above EL1 in aarch64 mode.

Signed-off-by: Nitin Jain <nitinj@xilinx.com>
Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/zynqmp/zynqmp.c b/board/xilinx/zynqmp/zynqmp.c
index ff0b3c7..b9825dd 100644
--- a/board/xilinx/zynqmp/zynqmp.c
+++ b/board/xilinx/zynqmp/zynqmp.c
@@ -316,6 +316,23 @@
 	return 0;
 }
 
+unsigned long do_go_exec(ulong (*entry)(int, char * const []), int argc,
+			 char * const argv[])
+{
+	int ret = 0;
+
+	if (current_el() > 1) {
+		smp_kick_all_cpus();
+		dcache_disable();
+		armv8_switch_to_el1(0x0, 0, 0, 0, (unsigned long)entry,
+				    ES_TO_AARCH64);
+	} else {
+		printf("FAIL: current EL is not above EL1\n");
+		ret = EINVAL;
+	}
+	return ret;
+}
+
 #if !defined(CONFIG_SYS_SDRAM_BASE) && !defined(CONFIG_SYS_SDRAM_SIZE)
 int dram_init_banksize(void)
 {