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>

board/xilinx/zynqmp/zynqmp.c

@@ -316,6 +316,23 @@ int zynq_board_read_rom_ethaddr(unsigned char *ethaddr)
 	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)
 {

include/command.h

@@ -111,6 +111,8 @@ extern int common_diskboot(cmd_tbl_t *cmdtp, const char *intf, int argc,
 extern int do_reset(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
 extern int do_poweroff(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
 
+extern unsigned long do_go_exec(ulong (*entry)(int, char * const []), int argc,
+				char * const argv[]);
 /*
  * Error codes that commands return to cmd_process(). We use the standard 0
  * and 1 for success and failure, but add one more case - failure with a