Allow ARM Standard platforms to dynamically define PSCI capability

The capabilities exposed by the PSCI generic layer depends on the hooks
populated by the platform in `plat_arm_psci_pm_ops`. Currently ARM
Standard platforms statically define this structure. However, some
platforms may want to modify the hooks at runtime before registering
them with the generic layer.

This patch introduces a new ARM platform layer API
`plat_arm_psci_override_pm_ops` which allows the platform to probe
the power controller and modify `plat_arm_psci_pm_ops` if required.
Consequently, 'plat_arm_psci_pm_ops' is no longer qualified as
`const` on ARM Standard platforms.

Change-Id: I7dbb44b7bd36c20ec14ded5ee45a96816ca2ab9d
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

include/plat/arm/common/plat_arm.h

@@ -220,4 +220,7 @@ int plat_arm_get_alt_image_source(
 unsigned int plat_arm_calc_core_pos(u_register_t mpidr);
 const mmap_region_t *plat_arm_get_mmap(void);
 
+/* Allow platform to override psci_pm_ops during runtime */
+const plat_psci_ops_t *plat_arm_psci_override_pm_ops(plat_psci_ops_t *ops);
+
 #endif /* __PLAT_ARM_H__ */

plat/arm/board/fvp/fvp_pm.c

@@ -327,7 +327,7 @@ static int fvp_node_hw_state(u_register_t target_cpu,
  * Export the platform handlers via plat_arm_psci_pm_ops. The ARM Standard
  * platform layer will take care of registering the handlers with PSCI.
  ******************************************************************************/
-const plat_psci_ops_t plat_arm_psci_pm_ops = {
+plat_psci_ops_t plat_arm_psci_pm_ops = {
 	.cpu_standby = fvp_cpu_standby,
 	.pwr_domain_on = fvp_pwr_domain_on,
 	.pwr_domain_off = fvp_pwr_domain_off,

plat/arm/board/juno/juno_pm.c

@@ -76,7 +76,7 @@ static int juno_translate_power_state_by_mpidr(u_register_t mpidr,
  * Export the platform handlers via plat_arm_psci_pm_ops. The ARM Standard
  * platform will take care of registering the handlers with PSCI.
  ******************************************************************************/
-const plat_psci_ops_t plat_arm_psci_pm_ops = {
+plat_psci_ops_t plat_arm_psci_pm_ops = {
 	.pwr_domain_on			= css_pwr_domain_on,
 	.pwr_domain_on_finish		= css_pwr_domain_on_finish,
 	.pwr_domain_off			= css_pwr_domain_off,

plat/arm/common/arm_pm.c

 /*
- * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -38,8 +38,11 @@
 #include <platform_def.h>
 #include <psci.h>
 
+/* Allow ARM Standard platforms to override this function */
+#pragma weak plat_arm_psci_override_pm_ops
+
 /* Standard ARM platforms are expected to export plat_arm_psci_pm_ops */
-extern const plat_psci_ops_t plat_arm_psci_pm_ops;
+extern plat_psci_ops_t plat_arm_psci_pm_ops;
 
 #if ARM_RECOM_STATE_ID_ENC
 extern unsigned int arm_pm_idle_states[];
@@ -150,6 +153,14 @@ int arm_validate_ns_entrypoint(uintptr_t entrypoint)
 	return PSCI_E_INVALID_ADDRESS;
 }
 
+/******************************************************************************
+ * Default definition on ARM standard platforms to override the plat_psci_ops.
+ *****************************************************************************/
+const plat_psci_ops_t *plat_arm_psci_override_pm_ops(plat_psci_ops_t *ops)
+{
+	return ops;
+}
+
 /******************************************************************************
  * Helper function to resume the platform from system suspend. Reinitialize
  * the system components which are not in the Always ON power domain.
@@ -201,7 +212,7 @@ void arm_program_trusted_mailbox(uintptr_t address)
 int plat_setup_psci_ops(uintptr_t sec_entrypoint,
 				const plat_psci_ops_t **psci_ops)
 {
-	*psci_ops = &plat_arm_psci_pm_ops;
+	*psci_ops = plat_arm_psci_override_pm_ops(&plat_arm_psci_pm_ops);
 
 	/* Setup mailbox with entry point. */
 	arm_program_trusted_mailbox(sec_entrypoint);

plat/arm/css/common/css_pm.c

@@ -261,7 +261,7 @@ int css_node_hw_state(u_register_t mpidr, unsigned int power_level)
  * Export the platform handlers via plat_arm_psci_pm_ops. The ARM Standard
  * platform will take care of registering the handlers with PSCI.
  ******************************************************************************/
-const plat_psci_ops_t plat_arm_psci_pm_ops = {
+plat_psci_ops_t plat_arm_psci_pm_ops = {
 	.pwr_domain_on		= css_pwr_domain_on,
 	.pwr_domain_on_finish	= css_pwr_domain_on_finish,
 	.pwr_domain_off		= css_pwr_domain_off,