reset2: Add css_system_reset2()

This function implements the platform dependant part of PSCI system
reset2 for CSS platforms using SCMI.

Change-Id: I724389decab484043cadf577aeed96b349c1466d
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

plat/arm/css/common/css_pm.c

@@ -300,4 +300,7 @@ plat_psci_ops_t plat_arm_psci_pm_ops = {
 	.read_mem_protect	= arm_psci_read_mem_protect,
 	.write_mem_protect	= arm_nor_psci_write_mem_protect,
 #endif
+#if CSS_USE_SCMI_SDS_DRIVER
+	.system_reset2		= css_system_reset2,
+#endif
 };

plat/arm/css/drivers/scp/css_pm_scmi.c

@@ -358,13 +358,35 @@ const plat_psci_ops_t *plat_arm_psci_override_pm_ops(plat_psci_ops_t *ops)
 		ops->system_off = NULL;
 		ops->system_reset = NULL;
 		ops->get_sys_suspend_power_state = NULL;
-	} else if (!(msg_attr & SCMI_SYS_PWR_SUSPEND_SUPPORTED)) {
+	} else {
+		if (!(msg_attr & SCMI_SYS_PWR_SUSPEND_SUPPORTED)) {
 			/*
-		 * System power management protocol is available, but it does
-		 * not support SYSTEM SUSPEND.
+			 * System power management protocol is available, but
+			 * it does not support SYSTEM SUSPEND.
 			 */
 			ops->get_sys_suspend_power_state = NULL;
 		}
+		if (!(msg_attr & SCMI_SYS_PWR_WARM_RESET_SUPPORTED)) {
+			/*
+			 * WARM reset is not available.
+			 */
+			ops->system_reset2 = NULL;
+		}
+	}
 
 	return ops;
 }
+
+int css_system_reset2(int is_vendor, int reset_type, u_register_t cookie)
+{
+	if (is_vendor || (reset_type != PSCI_RESET2_SYSTEM_WARM_RESET))
+		return PSCI_E_INVALID_PARAMS;
+
+	css_scp_system_off(SCMI_SYS_PWR_WARM_RESET);
+	/*
+	 * css_scp_system_off cannot return (it is a __dead function),
+	 * but css_system_reset2 has to return some value, even in
+	 * this case.
+	 */
+	return 0;
+}

plat/arm/css/drivers/scp/css_scp.h

@@ -15,6 +15,7 @@
 struct psci_power_state;
 
 /* API for power management by SCP */
+int css_system_reset2(int is_vendor, int reset_type, u_register_t cookie);
 void css_scp_suspend(const struct psci_power_state *target_state);
 void css_scp_off(const struct psci_power_state *target_state);
 void css_scp_on(u_register_t mpidr);