imx: imx8qx: add system off support

Add system power off support for i.MX8QX,
when Linux kernel issues "poweroff" command,
TF-A will send command to inform system
controller to power off whole board according
to board design, tested on i.MX8QX MEK board.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>

plat/imx/common/imx8_psci.c

+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch.h>
+#include <arch_helpers.h>
+#include <debug.h>
+#include <plat_imx8.h>
+#include <sci/sci.h>
+#include <stdbool.h>
+
+void __dead2 imx_system_off(void)
+{
+	sc_pm_set_sys_power_mode(ipc_handle, SC_PM_PW_MODE_OFF);
+	wfi();
+	ERROR("power off failed.\n");
+	panic();
+}
+
+

plat/imx/common/include/plat_imx8.h

@@ -17,4 +17,5 @@ void plat_gic_cpuif_enable(void);
 void plat_gic_cpuif_disable(void);
 void plat_gic_pcpu_init(void);
 
+void __dead2 imx_system_off(void);
 #endif /*__PLAT_IMX8_H__ */

plat/imx/imx8qx/imx8qx_psci.c

@@ -64,6 +64,7 @@ static const plat_psci_ops_t imx_plat_psci_ops = {
 	.pwr_domain_on = imx_pwr_domain_on,
 	.pwr_domain_on_finish = imx_pwr_domain_on_finish,
 	.validate_ns_entrypoint = imx_validate_ns_entrypoint,
+	.system_off = imx_system_off,
 };
 
 int plat_setup_psci_ops(uintptr_t sec_entrypoint,

plat/imx/imx8qx/platform.mk

@@ -20,6 +20,7 @@ BL31_SOURCES		+=	plat/imx/common/lpuart_console.S	\
 				plat/imx/imx8qx/imx8qx_bl31_setup.c	\
 				plat/imx/imx8qx/imx8qx_psci.c		\
 				plat/imx/common/imx8_topology.c		\
+				plat/imx/common/imx8_psci.c		\
 				lib/xlat_tables/xlat_tables_common.c	\
 				lib/xlat_tables/aarch64/xlat_tables.c	\
 				lib/cpus/aarch64/cortex_a35.S		\