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

Add support to switch to EL1 and load an EL1 app from U-Boot which is
executing at EL2 or EL3 in aarch64 mode.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Link: https://lore.kernel.org/r/20220506055345.1921-1-ashok.reddy.soma@xilinx.com


Signed-off-by: Michal Simek <michal.simek@amd.com>

board/xilinx/versal/board.c

@@ -91,6 +91,23 @@ int board_early_init_r(void)
 	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;
+}
+
 static u8 versal_get_bootmode(void)
 {
 	u8 bootmode;